Electrophotosensitive material

Abstract

The invention relates to an electrophotosensitive material comprising an organic photosensitive layer and an inorganic surface protective layer, wherein at least an outermost part of the organic photosensitive layer contains any one of the compounds represented by formulas (1) to (4). 1

Description

TECHNICAL FIELD

[0001] The present invention relates to an electrophotosensitive material.

BACKGROUND OF THE INVENTION

[0002] As an electrophotosensitive material for use in image forming apparatuses such as electrostatic copiers, laser beam printers, plain paper facsimiles and the like, a so-called organic electrophotosensitive material is widespread which comprises a combination of the following components:

[0003] a charge generating material for generating an electric charge (positive hole and electron) when exposed to light;

[0004] a charge transport material for transporting the generated electric charge; and

[0005] a binder resin.

[0006] The charge transport materials fall into two broad categories which include a positive-hole transport material for transporting positive holes of the electric charge, and an electron transport material for transporting electrons.

[0007] The organic electrophotosensitive material has an advantage over an inorganic electrophotosensitive material employing an inorganic semiconductor material in that the organic electrophotosensitive material is fabricated more easily at less production costs than the latter.

[0008] In addition, the organic electrophotosensitive material also has a merit of greater freedom of function design by virtue of a wide variety of options for materials including charge generating materials, charge transport materials, binder resins and the like.

[0009] The organic electrophotosensitive material is constructed by forming a single-layer or multi-layer photosensitive layer over a conductive substrate.

[0010] The single-layer photosensitive layer is formed by dispersing a charge generating material and a charge transport material (a positive-hole transport material and/or an electron transport material) in a binder resin.

[0011] The multi-layer photosensitive layer is formed by forming a lamination of the charge generating layer containing the charge generating material and the charge transport layer containing the charge transport material (the positive-hole transport material or the electron transport material).

[0012] Despite the aforementioned various merits, the organic electrophotosensitive material is susceptible to scratches, mars and the like in an actual use environment, thus suffering a smaller durability than the inorganic electrophotosensitive material.

[0013] With an aim at increasing the durability of the organic electrophotosensitive material by solving the above problem, study has been made on an approach to overlay a surface protective layer on an outermost layer.

[0014] The widely used surface protective layer is exemplified by an organic layer which is preferable in the light of adhesion to and affinity with the organic photosensitive layer, integrity as a lamination, and consistency in the film forming process. A usable surface protective layer includes, for example, a layer of binder resin, and a layer of binder resin having conductive particles, such as of metal oxides, dispersed therein.

[0015] However, the electrophotosensitive material employing such an organic layer as the surface protective layer suffers the drawbacks of an increased residual potential and a lowered chargeability when repeatedly used for image forming processes, and of significant variations in the photosensitivity characteristics due to environmental changes (temperature, humidity and the like).

[0016] In this connection, more recent years have seen investigations made on the use of an inorganic layer as the surface protective layer, the inorganic layer comprising an inorganic material such as metallic elements, carbon and inorganic compounds containing any of these elements, and having high hardness and wear resistance. The inorganic surface protective layer may be laid over the organic photosensitive layer by, for example, the vapor deposition method such as sputtering, plasma CVD, photo CVD or the like.

[0017] The inorganic surface protective layer is employed for the purposes of protecting the organic photosensitive layer and overcoming the above problem. specifically, the electrophotosensitive material with the inorganic surface protective layer laid over the organic photosensitive layer has functions associated with the characteristics of the individual layers thereof, the organic photosensitive layer involved in the generation and transport of the electric charge, the surface protective layer responsible for ensuring the good durability and environmental resistance.

[0018] As compared with the organic surface protective layer, however, the inorganic surface protective layer has a lower ability to achieve a sufficient adhesion to the organic photosensitive layer. Even if adjustments for the deposition process or the deposition conditions may provide the inorganic layer with a sufficient initial adhesion to the organic layer, the inorganic layer is prone to suffer cracks or delamination due to various stresses imposed thereon under the actual use environment or during the long-term storage thereof.

[0019] In the combination of the organic photosensitive layer and the inorganic surface protective layer, which are formed of different materials, there are not attained as good adhering relation, affinity and integrity as in the combination of the organic layers or of the inorganic layers. That is, the organic layer and the inorganic layer are often merely combined with each other through a very small binding strength.

[0020] Accordingly, when subjected to mechanical stresses such as of contact pressure from a cleaning blade of the image forming apparatus, or thermal stresses due to repeated cycles of heating during the operation of the apparatus and cooling during the nonoperation thereof, or temperature changes during storage, the electrophotosensitive material will suffer cracks in the inorganic surface protective layer or delamination of the surface protective layer from the organic photosensitive layer as a result of increased differences between the hardnesses, flexibilities, expansion/shrinkage properties or the like of these layers.

[0021] In the present conditions, therefore, the conventional inorganic surface protective layer is yet to be put to practical use because it has not achieved a sufficient effect to increase the durability of the organic photosensitive layer.

SUMMARY OF THE INVENTION

[0022] It is an object of the invention to provide an organic electrophotosensitive material comprising an inorganic surface protective layer less prone to suffer cracks or delamination and excellent in physical stability, thereby achieving a greater durability as compared with the prior-art products.

[0023] For achieving the above object, the inventors have analyzed and investigated the film forming process for the inorganic surface protective layer.

[0024] As a result, the inventors have discovered that a condition of the surface protective layer initially deposited on the outermost part of the organic photosensitive layer has a significant influence on the physical stability of the surface protective layer subsequently deposited.

[0025] At an initial stage of the film formation, the inorganic material forming the surface protective layer is somehow combined with a part of the material of the organic photosensitive layer that is exposed at the outermost part thereof, thereby forming a nucleus for film growth. A film of the inorganic material grows about the resultant nucleus and thus, the surface protective layer is formed. In the surface protective layer thus formed, the nucleus portion functions as a binding point with the organic photosensitive layer, ensuring the good adhesion between these layers.

[0026] Therefore, the magnitude of binding strength between the organic photosensitive layer and the inorganic material at individual binding points as well as the per-area number of binding points namely the density of the binding points at an interface between the organic photosensitive layer and the surface protective layer give significant influences on the adhesion of the surface protective layer to the organic photosensitive layer and the physical stability of the surface protective layer.

[0027] Specifically, with increase in the binding strength between the organic photosensitive layer and the inorganic material and also in the density of the binding points at the interface between these layers, the surface protective layer is accordingly increased in the adhesion to the organic photosensitive layer, resulting in the greater physical stability.

[0028] As mentioned supra, the typical organic photosensitive layer has a structure wherein low molecular weight functional materials including the charge generating material, charge transport material and the like are dispersed in the binder resin forming the layer.

[0029] From the standpoint of the findings regarding the binding points, it is thought ideal that the binder resin, forming the layer and accounting for a major part thereof, acts as the nucleus of film growth so as to be combined with the inorganic material forming the surface protective layer.

[0030] In the actual process, however, because of the stability and reactivity of the molecules per se or of the reaction site, the formation of the surface protective layer proceeds with some of the low molecular weight materials, that is exposed at the outermost part of the organic photosensitive layer, functioning as the nuclei of film growth, the low-molecular weight materials including the charge generating material, charge transport material and the like which are dispersed in the layer.

[0031] Hence, the properties of the low molecular weight materials, which include the reactivity and binding strength with the inorganic material, the degrees of the compatibility and affinity with the binder resin forming the organic photosensitive layer, the dimensions of the materials themselves (including not only the molecular weight but also the molecular or spatial extent), also significantly affect the adhesion to the organic photosensitive layer and the physical stability of the surface protective layer.

[0032] That is, as the low molecular-weight materials are increased in the reactivity and binding strength with the inorganic material, the surface protective layer is accordingly improved in the adhesion to the organic photosensitive layer and in the physical stability thereof.

[0033] Furthermore, as the low molecular weight materials are increased in the compatibility and affinity with the binder resin forming the organic photosensitive layer as well as in the dimensions thereof, a so-called anchor effect is accordingly increased so that the surface protective layer is also improved in the adhesion to the organic photosensitive layer and the physical stability thereof.

[0034] As to the combined form between the low molecular weight materials and the inorganic material, the most preferred is molecular bond in the light of the magnitude of the binding strength. However, if this bond should change the molecular structure to cause the production of an electric charge trap, the photosensitivity of the electrophotosensitive material might be decreased.

[0035] Therefore, an important consideration in the use of the low-molecular weight materials influence the need to prevent the reaction from transforming the molecular structure to a state reduced in the electrical properties.

[0036] Thus, the inventors have found that a electrophotosensitive material capable of forming preferable images cannot be obtained simply by overlaying on the conventional organic photosensitive layer a surface protective layer containing an inorganic material of a greater hardness.

[0037] Only after the fabrication of electrophotosensitive materials satisfying the various conditions described above, the inventors have finally discovered that the inorganic surface protective layer contributes to the improvement of the durability and environmental resistance of the electrophotosensitive material while maintaining the electrical characteristics of the organic photosensitive layer as they are.

[0038] Taking these findings into consideration, the inventors have made investigation into various materials for forming the organic photosensitive layer. The invention has been achieved by the inventors' study that a suitable material satisfying these requirements is a compound represented by any one of the following formulas (1) to (4): 2

[0039] wherein R1, R2, R3, R4, R5, R6, R7 and R8 are the same or different and each denoting a hydrogen atom, alkyl group, alkoxy group, aryl group, cycloalkyl group or aralkyl group; and out of the groups R1 to R8, two groups bonded to adjacent carbon atoms of the same ring may be linked together to form a condensed ring jointly with the ring; 3

[0040] wherein R9 and R10 are the same or different and each denoting a hydrogen atom, alkyl group, alkoxy group, alkylthio group, aryl group, cycloalkyl group, aryloxy group, arylthio group or a group represented by a formula (2a) 4

[0041] provided that R9 and R10 are not hydrogen atoms at the same time; R9 and R10 may be linked together to form a condensed ring jointly with the ring; R11 denotes a hydrogen atom, halogen atom, alkyl group, alkoxy group, aryl group or aralkyl group; in which formula (2a), R12 denotes an alkyl group, alkoxy group, aryl group or aryloxy group; and ‘a’ denotes an integer of 0 to 4;

[0042] Formula (3) 5

[0043] wherein R13 and R14 are the same or different and each denoting a hydrogen atom, alkyl group, alkoxy group, aryl group, cycloalkyl group or aralkyl group; and

[0044] Formula (4) 6

[0045] wherein R15 denotes a hydrogen atom, halogen atom, alkyl group, alkoxy group, aryl group, cycloalkyl group or aralkyl group; ‘b’ denotes an integer of 0 to 4, provided that when ‘b’ is 2 or more, the two groups R15 bonded to adjacent carbon atoms of the ring may be linked together to form a condensed ring jointly with the ring; A1 denotes an oxygen atom or a group represented by a formula (4a): 7

[0046] in which R16 and R17 are the same or different and each denoting a cyano group or alkoxycarbonyl group; A2 denotes a group represented by a formula (4b): 8

[0047] or a formula (4c): 9

[0048] in which formula (4b), A3 denotes a —N═CH— group or —N═N— group; R18 denotes a hydrogen atom, halogen atom, alkyl group, alkoxy group, aryl group, cycloalkyl group or aralkyl group; and ‘c’ denotes an integer of 0 to 5, provided that when ‘c’ is 2 or more, the groups R18 may be linked together to form a condensed ring jointly with the ring;

[0049] in which formula (4c), R19 and R20 are the same or different and each denoting a hydrogen atom, halogen atom, alkyl group, alkoxy group, aryl group, cycloalkyl group or aralkyl group; ‘d’ denotes an integer of 0 to 4, provided that when ‘d’ is 2 or more, the groups R19 may be linked together to form a condensed ring jointly with the ring; ‘e’ denotes an integer of 0 to 5, provided that when ‘e’ is 2 or more, the two groups R20 bonded to adjacent carbon atoms of the ring may be linked together to form a condensed ring jointly with the ring; and A4 denotes an oxygen atom or a group represented by a formula (4d): 10

[0050] in which R21 and R22 are the same or different and each denoting a cyano group or alkoxycarbonyl group.

[0051] In short, the electrophotosensitive material of the invention comprises the organic photosensitive layer and the inorganic surface protective layer laid over the conductive substrate in this order, wherein at least an outermost part of the organic photosensitive layer that contacts the surface protective layer contains at least one compound selected from the group consisting of a diphenoquinone derivative of the formula (1), a naphthoquinone derivative of the formula (2), a naphthylene diimide derivative of the formula (3) and a quinone derivative of the formula (4).

[0052] The above compounds each having the following features:

[0053] a π-electron conjugated system is spread across the molecules thereof,

[0054] having the carbonyl group or the A1=C< group,

[0055] has a molecular structure spread in a plane-like fashion as a whole, thus having a great molecular or spatial extent.

[0056] In detail,the above compounds each feature a great reactivity with the inorganic material forming the surface protective layer because a π-electron conjugated system is spread across the molecules thereof so that the compounds has a function to attract particularly a metallic element or carbon of the inorganic material at the initial stage of the film forming process.

[0057] Additionally, this function increases the ratio of the molecules of these compounds exposed at the outermost part of the organic photosensitive layer that are combined with the inorganic material to form the nuclei of film growth. This results in a higher density of the binding points at the interface between these layers.

[0058] Furthermore, the higher the density of the binding points, the greater the film growth rate. Therefore, the time for film forming process may be reduced thereby minimizing damage on the organic photosensitive layer during the deposition of the surface protective layer by the vapor deposition method or the like.

[0059] With a π-bond of a double bond in the molecules split off, each of the above compounds is rigidly combined with a metallic element, carbon or the like via molecular bond. Particularly in the π-bond of the carbonyl group in the compounds of the formulas (1) to (3) or of the A1=C< group (including the carbonyl group) in the compound of the formula (4), there is a great difference of electronegativity between carbon and oxygen or between carbon and the group A1. This provides a dipolar resonance structure wherein carbon has a positive polarity while oxygen or the group A1 has a negative polarity. As a result, the compound is increased in reactivity, contributing to a significant increase in the binding strength between the organic photosensitive layer and the inorganic material.

[0060] In addition, each of the compounds has a molecular structure spread in a plane-like fashion as a whole, thus having a great molecular or spatial extent. Furthermore, the compounds are all excellent in compatibility and affinity with the binder resin, presenting a good anchor effect on the binder resin.

[0061] Therefore, the binding strength between the organic photosensitive layer and the inorganic material is increased.

[0062] According to the invention, the physical stability of the inorganic surface protective layer can be improved by increasing the adhesion thereof to the organic photosensitive layer. Thus, the surface protective layer is prevented from suffering the occurrence of cracks and delamination in the actual use environment or during the long-term storage. As a result, the electrophotosensitive material featuring a superior durability to the conventional ones is provided.

[0063] Furthermore, the compounds do not produce a deep electric charge trap even when they are changed in the molecular structures thereof due to the molecular bond with a metal or carbon. In addition, the molecular bond occurs only in a limited part of the compound that is exposed at the outermost part of the organic photosensitive layer, so that a major part of the compound in the organic photosensitive layer maintains its initial state as it is. Hence, there is no fear of reducing the photosensitivity of the electrophotosensitive material.

[0064] Besides the above merits, all the compounds are excellent in compatibility with the binder resin so that a large amount of each compound may be uniformly dispersed in the binder resin without producing particle aggregation. As a result, the electrophotosensitive material of the invention also features good photosensitivity characteristics.

DETAILED DESCRIPTION OF THE INVENTION

[0065] The invention will be described as below.

[0066] In an electrophotosensitive material according to the invention, at least an outermost part of an organic photosensitive layer that is in contact with a surface protective layer contains any one of the above compounds represented by the formulas (1) to (4).

[0067] Examples of the alkyl group in the above formulas include alkyl groups having 1 to 12 carbon atoms, such as methyl, ethyl, n-propyl (n-Pr), isopropyl (i-Pr), n-butyl (n-Bu), isobutyl (i-Bu), sec-butyl (s-Bu), tert-butyl (t-Bu), pentyl (n-amyl), isopentyl (isoamyl), sec-amyl, tert-amyl, neopentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl and the like.

[0068] Examples of the alkoxy group include alkoxy groups having 1 to 12 carbon atoms, such as methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, sec-butoxy, tert-butoxy, pentyloxy, isopentyloxy, neopentyloxy, hexyloxy, heptyloxy, octyloxy, nonyloxy, decyloxy, undecyloxy, dodecyloxy and the like.

[0069] Examples of the aryl group include groups derived from aromatic compounds such as benzene, toluene, xylene, biphenyl, o-terphenyl, m-terphenyl, p-terphenyl, naphthalene, anthracene, phenanthrene, pyrene, indene, azulene, heptalene, biphenylene, fluorene and the like.

[0070] Examples of the aralkyl group include aralkyl groups having 4 to 10 carbon atoms in an aryl potion thereof, such as benzyl, benzhydryl, triphenylmethyl, phenethyl, thenyl, furfuryl and the like.

[0071] Examples of the alkylthio group include those represented by —S—Ra wherein Ra denotes the above alkyl group having 1 to 12 carbon atoms.

[0072] Examples of the aryloxy group include those represented by —O-Φ1 wherein Φ1 denotes the aforesaid aryl group.

[0073] Examples of the arylthio group include those represented by —S-Φ2 wherein Φ2 denotes the aforesaid aryl group.

[0074] Examples of the alkoxycarbonyl group include those represented by —COORb wherein Rb denotes the above alkyl group having 1 to 12 carbon atoms.

[0075] Examples of the cycloalkyl group include cycloalkyl groups having 5 to 12 carbon atoms, such as cyclopentyl, cyclohexyl, 1-cyclohexenyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, cycloundecyl, cyclododecyl and the like.

[0076] Examples of the heterocyclic group include such as thienyl, furyl, pyrrolyl, pyrrolidinyl, oxazoly, isoxazolyl, thiazolyl, isothiazolyl, imidazolyl, 2H-imidazolyl, piperidyl, piperidino, 3-morpholinyl, morpholino and the like. In addition, it may be a heterocyclic group condensed with an aromatic ring.

[0077] These groups may contain a substituent which is exemplified by the above groups and halogen atoms. Other usable substituents include, for example, hydroxyalkyl groups; alkoxyalkyl groups; monoalkyl aminoalkyl groups; dialkyl aminoalkyl groups; halogen-substituted alkyl groups; alkoxycarbonylalkyl groups; carboxyalkyl groups; alkanoyloxyalkyl groups; aminoalkyl groups; amino group; hydroxy group; optionally esterified carboxyl groups; cyano group, nitro group and the like. The substituents are not particularly limited in the position and the number. Diphenoquinone Derivative Among the above compounds, an example of a preferred diphenoquinone derivative of the formula (1) includes at least one selected from the group consisting of a diphenoquinone compound represented by a formula (1-1): 11

[0078] wherein R1a, R2a, R3a, R4a, R5a, R6a, R7a and R8a are the same or different and each denoting a hydrogen atom, alkyl group, alkoxy group, aryl group, cycloalkyl group or aralkyl group; and

[0079] a dinaphthoquinone compound represented by a formula (1-2): 12

[0080] wherein R3b, R4b, R5b and R6b are the same or different and each denoting a hydrogen atom, alkyl group, alkoxy group, aryl group, cycloalkyl group or aralkyl group.

[0081] Specific examples of the diphenoquinone compound of the formula (1-1) include compounds represented by formulas (1-1-1) to (1-1-32). 13

[0082] Specific examples of the dinaphthoquinone compound of the formula (1-2) include compounds represented by formulas (1-2-1) to (1-2-11). 14

[0083] Naphthoquinone Derivative

[0084] An example of a preferred naphthoquinone derivative of the formula (2) includes at least one selected from the group consisting of a naphthoquinone compound represented by a formula (2-1): 15

[0085] wherein R9a denotes an alkyl group, cycloalkyl group or aryl group;

[0086] a naphthoquinone compound represented by a formula (2-2): 16

[0087] wherein R9b and R10b are the same or different and each denoting an alkoxy group, alkylthio group, aryloxy group or arylthio group;

[0088] a naphthoquinone compound represented by a formula (2-3): 17

[0089] wherein R9c denotes an alkyl group or aryl group; and R12c denotes an alkyl group, alkoxy group, aryl group or aryloxy group;

[0090] a diindenopyrazine compound represented by a formula (2-4): 18

[0091] wherein R11d, R21a and R22a are the same or different and each denoting a hydrogen atom, halogen atom, alkyl group, alkoxy group, aryl group or aralkyl group; ‘a’ and ‘f’ are the same or different and each denoting an integer of 0 to 4; and ‘g’ denotes an integer of 0 to 5; a diindenopyrazine compound represented by a formula (2-5): 19

[0092] wherein R11e and R21b are the same or different and each denoting a hydrogen atom, halogen atom, alkyl group, alkoxy group, aryl group or aralkyl group; and ‘a’ and ‘f’ are the same or different and each denoting an integer of 0 to 4; and

[0093] a dioxotetracenedione compound represented by a formula (2-6): 20

[0094] wherein A5 and A6 are the same or different and each denoting an oxygen atom or =N-CN group; and R23a, R23b, R23c and R23d are the same or different and each denoting a hydrogen atom, alkyl group, alkoxycarbonyl group, cycloalkyl group or group represented by a formula (2-6a): 21

[0095] in which R24a, R24b, R24c, R24d and R24e are the same or different and each denoting a hydrogen atom or alkyl group.

[0096] Specific examples of the naphthoquinone compound of the formula (2-1) include compounds represented by formulas (2-1-1) to (2-1-1-6). 22

[0097] Specific examples of the naphthoquinone compound of the formula (2-2) include compounds represented by formulas (2-2-1) to (2-2-23). 23

[0098] Specific examples of the naphthoquinone compound of the formula (2-3) include compounds represented by formulas (2-3-1) to (2-3-11). 24

[0099] Specific examples of the diindenopyrazine compound of the formula (2-4) include compounds represented by formulas (2-4-1) to (2-4-4). 25

[0100] Specific examples of the diindenopyrazine compound of the formula (2-5) include compounds represented by formulas (2-5-1) to (2-5-4). 26

[0101] Specific examples of the dioxotetracenedione compound of the formula (2-6) include compounds represented by formulas (2-6-1) to (2-6-11). 27

[0102] Naphthylene Diimide Derivative

[0103] Specific examples of the naphthylene diimide derivative of the formula (3) include compounds represented by formulas (3-1-1) to (3-1-13). 28

[0104] Quinone Derivative

[0105] An example of a preferred quinone derivative of the formula (4) includes at least one selected from the group consisting of a compound represented by a formula (4-1) 29

[0106] wherein R15a and R18a are the same or different and each denoting a hydrogen atom, halogen atom, alkyl group, alkoxy group, aryl group or aralkyl group; ‘b’ denotes an integer of 0 to 4, provided that when ‘b’ is 2 or more, the two groups R15a bonded to adjacent carbon atoms of the ring may be linked together to form a condensed ring jointly with the ring; ‘c’ denotes an integer of 0 to 5, provided that when ‘c’ is 2 or more, the groups R18a may be linked together to form a condensed ring jointly with the ring; and Ala denotes an oxygen atom or the group represented by the formula (4a);

[0107] a compound represented by a formula (4-2): 30

[0108] wherein R15b, R19b and R20b are the same or different and each denoting a hydrogen atom, halogen atom, alkyl group, alkoxy group, aryl group, cycloalkyl group, hetero cyclic group or aralkyl group; ‘b’, ‘d’ and ‘e’ are the same or different and each denoting an integer of 0 to 4, provided that when ‘d’ is 2 or more, the groups may be linked together to form a condensed ring jointly with the ring; when ‘b’ or ‘e’ is 2 or more, the corresponding two groups bonded to adjacent carbon atoms of each ring may be linked together to form a condensed ring jointly with the ring; A1b denotes an oxygen atom or the group represented by the formula (4a); and A4b denotes an oxygen atom or the group represented by the formula (4d); and a compound represented by a formula (4-3): 31

[0109] wherein R15c and R18c are the same or different and each denoting a hydrogen atom, halogen atom, alkyl group, alkoxy group, aryl group or aralkyl group; ‘b’ denotes an integer of 0 to 4, provided that when ‘b’ is 2 or more, the two groups R15c bonded to adjacent carbon atoms of the ring may be linked together to form a condensed ring jointly with the ring; ‘c’ denotes an integer of 0 to 5, provided that when ‘c’ is 2 or more, the groups R18c may be linked together to form a condensed ring jointly with the ring; and A1c denotes an oxygen atom or the group represented by the formula (4a).

[0110] Specific examples of the compound of the formula (4-1) include compounds represented by formulas (4-1-1) to (4-1-16). 32

[0111] Specific examples of the compound of the formula (4-2) include compounds represented by formulas (4-2-1) to (4-2-20). 33

[0112] Specific examples of the compound of the formula (4-3) include compounds represented by formulas (4-3-1) to (4-3-15). 34

[0113] The above compounds of the formulas (1) to (4) may be used alone or in combination of two or more types. organic electrophotosensitive Layer The organic photosensitive layer includes a single layer type and a multi-layer type, and the invention may be applicable to both of the types.

[0114] The single-layer photosensitive layer is formed by the steps of applying a coating solution to a conductive substrate and drying the solution, the coating solution prepared by dissolving or dispersing in a suitable organic solvent, at least one of the compounds of the formulas (1) to (4), the charge generating material, the charge transport material and the binder resin.

[0115] The single-layer photosensitive layer features a simple layer construction and good productivity.

[0116] Since all the compounds of the formulas (1) to (4) have a function as the electron transport material, the charge transport material may be dispensed with. However, it is preferred to admix the charge transport material in order to attain preferable sensitivity characteristics.

[0117] As to the charge transport material, either of the positive-hole transport material and the electron-transport material may be used according to a charge polarity of the photosensitive layer.

[0118] Furthermore, both polarities charge transport materials may be used in combination with the above charge transport material. A photosensitive layer including such charge transport materials of opposite polarities is advantageous in that a single layer construction is positively and negatively chargeable.

[0119] The multi-layer photosensitive layer is formed by the steps of overlaying on the conductive substrate the charge generating layer containing the charge generating material, applying a coating solution containing the charge transport material and the binder resin onto the resultant charge generating layer, and drying the solution thereby forming the charge transport layer. Otherwise, the multi-layer photosensitive layer may also be obtained by forming the charge transport layer over the conductive substrate, followed by forming thereover the charge generating layer.

[0120] The charge generating layer may further contain a charge transport material of the opposite polarity to that of the charge transport layer.

[0121] There are a great variety of multi-layer photosensitive layers in correspondence to combinations of the orders of the formation of the charge generating layer and charge transport layer and the polarities of the charge transport materials contained in these layers.

[0122] Specific examples of the multi-layer photosensitive layer include the following four types:

[0123] (a) a negative-charge multi-layer photosensitive layer wherein the charge generating layer containing the charge generating material and, as required, the electron transport material is formed over the conductive substrate and then the charge transport layer containing the positive-hole transport material is laid over the charge generating layer;

[0124] (b) a negative-charge multi-layer photosensitive layer wherein the charge transport layer containing the electron transport material is formed over the conductive substrate, and then the charge generating layer containing the charge generating material and, as required, the positive-hole transport material is laid over the charge transport layer;

[0125] (c) a positive-charge multi-layer photosensitive layer wherein the charge generating layer containing the charge generating material and, as required, the positive-hole transport material is formed over the conductive substrate and then, the charge transport layer containing the electron transport material is laid over the charge generating layer; and

[0126] (d) a positive-charge multi-layer photosensitive layer wherein the charge transport layer containing the positive-hole transport material is formed over the conductive substrate and then, the charge generating layer containing the charge generating material and, as required, the electron transport material is laid over the charge transport layer.

[0127] As compared with the positive-charge photosensitive layers (c) and (d), the negative-charge photosensitive layers (a) and (b) are generally more preferred because of more excellent electrical characteristics thereof such as photosensitivity and residual potential.

[0128] In addition, the charge generating layer has quite a small thickness as compared with the charge transport layer and hence, the construction (a) with the charge transport layer laid on the upper side is more preferred.

[0129] According to the invention, the upper layer located at the outermost part of the above multi-layer photosensitive layer and contacting the surface protective layer is required to contain at least one of the compounds of the formulas (1) to (4).

[0130] Examples of a usable charge generating material include powders of inorganic photoconductive materials such as selenium, selenium-tellurium, selenium-arsenic, cadmium sulfide, α-silicon and the like; and a variety of known pigments including phthalocyanine pigments comprising crystalline phthalocyanine compounds of various crystalline forms such as metal-free phthalocyanine represented by a formula (CG-1): 35

[0131] titanyl phthalocyanine represented by a formula (CG-2): 36

[0132] azo pigments, bisazo pigments, perylene pigments, anthanthrone pigments, indigo pigments, triphenylmethane pigments, threne pigments, toluidine pigments, pyrazoline pigments, quinacridone pigments, dithioketopyrolopyrrole pigments and the like.

[0133] The charge generating materials may be used alone or in combination of two or more types such that the photosensitive layer may have sensitivity at a desired wavelength range.

[0134] Particularly, a electrophotosensitive material having photosensitivity in the wavelength range of 700 nm or more is required by digital-optical image forming apparatuses such as laser beam printers, plain paper facsimiles and the like which utilize infrared light such as semiconductor laser beam. Accordingly, phthalocyanine pigments among the above exemplary compounds are preferably employed as the charge generating material.

[0135] Any of the various known electron-transporting compounds may be used as the electron transport material.

[0136] A preferred electron transport material include electron-attracting compounds which include, for example, benzoquinone compounds, diphenoquinone compounds, isatin compounds such as a compound represented by a formula (ET-1): 37

[0137] naphthoquinone compounds, malononitrile, thiopyran compounds, tetracyanoethylene, 2,4,8-trinitrilothioxanthone, fluorenone compounds such as 2,4,7-trinitrilo-9-fluorenone, dinitrobenzene, dinitroanthracene, dinitroacridine, nitroanthraquinone, succinic anhydride, maleic anhydride, dibromomaleic anhydride, 2,4,7-trinitrofluorenoneimine compounds, ethylated nitrofluorenoneimine compounds, tryptantrin compounds, tryptantrinimine compounds, azafluorenone compounds, dinitropyridoquinazoline compounds, thioxanthene compounds, 2-phenyl-1,4-benzoquinone compounds, 2-phenyl-1,4-naphthoquinone compounds, 5,12-naphthacenequinone compounds, α-cyanostilbene compounds, 4′-nitrostilbene compounds, salts formed by reaction between anionic radicals of benzoquinone compounds and cations.

[0138] These materials may be used alone or in combination of two or more types.

[0139] Any of the various known positive-hole transporting compounds may be used as the positive-hole transport material.

[0140] Examples of a particularly preferred positive-hole transport material include benzidine compounds, phenylenediamine compounds, naphthylenediamine compounds, phenantolylenediamine compounds, oxadiazole compounds such as 2,5-di(4-methylaminophenyl)-1,3,4-oxadiazole, styryl compounds such as 9-(4-diethylaminostyryl)anthracene, carbazole compounds such as poly-N-vinylcarbazole having a repeated unit represented by a formula (HT-1): 38

[0141] organic polysilane compounds having a repeated unit represented by a formula (HT-2): 39

[0142] [wherein Ra and Rb are the same or different each denoting an alkyl group, alkoxy group, aryl group or aralkyl group], pyrazoline compounds such as 1-phenyl-3-(p-dimethylaminophenyl)pyrazoline, hydrazone compounds such as diethylaminobenzaldehyde diphenylhydrazone represented by a formula (HT-3): 40

[0143] triphenylamine compounds such as tris(3-methylphenyl)amine, indole compounds, oxazole compounds, isooxazole compounds, thiazole compounds, thiadiazole compounds, imidazole compounds, pyrazole compounds, triazole compounds, butadiene compounds, pyrene-hydrazone compounds, acrolein compounds, carbazole-hydrazone compounds, quinoline-hydrazone compounds, stilbene-hydrazone compounds, diphenylenediamine compounds and the like.

[0144] These compounds may be used alone or in combination of two or more types.

[0145] Examples of a usable binder resin include thermoplastic resins such as styrene polymers, styrene-butadiene copolymers, styrene-acrylonitrile copolymers, styrene-maleic acid copolymers, acrylic polymers, styrene-acryl copolymers, polyethylene, ethylene-vinyl acetate copolymers, chlorinated polyethylene, polyvinyl chloride, polypropylene, copolymers of vinyl chloride and vinyl acetate, polyester, alkyd resins, polyamide, polyurethane, polycarbonate, polyarylate, polysulfone, diarylphthalate resins, ketone resins, polyvinylbutyral resins, polyether resins and the like;

[0146] crosslinking thermosetting resins such as silicone resins, epoxy resins, phenol resins, urea resins, melamine resins and the like; and

[0147] photosetting resins such as epoxy-acrylate, urethane-acrylate and the like.

[0148] These resins may be used alone or in combination of two or more types.

[0149] Where the aforesaid high-molecular positive-hole transport material such as poly-N-vinylcarbazole or organic polysilane compound is used, such a compound also serves as the binder resin and hence, the aforesaid binder resin may be dispensed with.

[0150] Additionally to the above components, the photosensitive layer may further contain any of the various additives such as fluorene compound, ultraviolet absorber, plasticizer, surfactant, leveling agent and the like. For an increased photosensitivity of the electrophotosensitive material, there may be further added a sensitizer such as terphenyl, halonaphthoquinone, acenaphthylene or the like.

[0151] The single-layer photosensitive layer may preferably contain 0.1 to 50 parts by weight or particularly 0.5 to 30 parts by weight of charge generating material, and 5 to 100 parts by weight or particularly 10 to 80 parts by weight of at least one of the compounds of the formulas (1) to (4), based on 100 parts by weight of binder resin.

[0152] The mixing ratio of the charge transport material may be suitably defined based on the charge polarity or construction of the photosensitive layer.

[0153] Where the positive-hole transport material is used alone as the charge transport material, for instance, the mixing ratio of the positive-hole transport material is preferably in the range of 5 to 500 parts by weight or particularly of 25 to 200 parts by weight based on 100 parts by weight of binder resin. It is also possible to employ the aforesaid positive-hole transport material also serving as the binder resin so as to dispense with the binder resin.

[0154] Where the electron transport material is used alone as the charge transport material, for instance, the mixing ratio of the electron transport material is preferably in the range of 5 to 100 parts by weight or particularly of 10 to 80 parts by weight based on 100 parts by weight of binder resin.

[0155] Where the positive-hole transport material and the electron transport material are used in combination as the charge transport material, for instance, these materials may preferably be present in total amount of 20 to 500 parts by weight or particularly of 30 to 200 parts by weight based on 100 parts by weight of binder resin.

[0156] The single-layer photosensitive layer may preferably have a thickness of 5 to 100 μm or particularly of 10 to 50 μm.

[0157] In the multi-layer photosensitive layer of the construction (a), the charge generating layer disposed on the lower side thereof may be formed from the charge generating material alone or from the binder resin in which the charge generating material and, as required, the electron transport material are dispersed. In the latter case, it is preferred that the charge generating material is present in the range of 5 to 1000 parts by weight or particularly of 30 to 500 parts by weight based on 100 parts by weight of binder resin while the electron transport material is present in the range of 1 to 200 parts by weight or particularly of 5 to 100 parts by weight based on 100 parts by weight of binder resin.

[0158] In the construction (a), the charge transport layer disposed on the upper side may preferably contain the positive-hole transport material in the range of 10 to 500 parts by weight or particularly of 25 to 200 parts by weight based on 100 parts by weight of binder resin, and at least one of the compounds of the formulas (1) to (4) in the range of 0.1 to 250 parts by weight or particularly of 0.5 to 150 parts by weight based on 100 parts by weight of binder resin. In this case, as well, the aforesaid positive-hole transport material also serving as the binder resin may be used so as to dispense with the binder resin.

[0159] As to the thickness of the multi-layer photosensitive layer, the charge generating layer may preferably have a thickness of about 0.01 to 5 μm or particularly of about 0.1 to 3 μm, whereas the charge transport layer may preferably have a thickness of about 2 to 100 μm or particularly of about 5 to 50 μm.

[0160] An intermediate layer or barrier layer may be formed between the single-layer or the multi-layer organic photosensitive layer and the conductive substrate or between the charge generating layer and the charge transport layer of the multi-layer photosensitive layer, so long as such a layer does not decrease the characteristics of the electrophotosensitive material.

[0161] Where each layer forming the electrophotosensitive material is formed by the coating method, the charge generating material, charge transport material, binder resin and the like may be dispersed, by mixing, into an organic solvent using a roll mill, ball mill, attritor, paint shaker, ultrasonic disperser or the like, thereby to prepare a coating solution, which may be applied and dried by the known means.

[0162] Examples of a usable organic solvent include alcohols such as methanol, ethanol, isopropanol, butanol and the like;

[0163] aliphatic hydrocarbons such as n-hexane, octane, cyclohexane and the like;

[0164] aromatic hydrocarbons such as benzene, toluene, xylene and the like;

[0165] halogenated hydrocarbons such as dichloromethane, dichloroethane, carbon tetrachloride, chlorobenzene and the like;

[0166] ethers such as dimethyl ether, diethyl ether, tetrahydrofuran, 1,4-dioxane, ethyleneglycol dimethyl ether, diethyleneglycol dimethyl ether and the like;

[0167] ketones such as acetone, methyl ethyl ketone, cyclohexanone and the like;

[0168] esters such as ethyl acetate, methyl acetate and the like; and

[0169] dimethylformaldehyde, dimethylformamide, dimethyl sulfoxide and the like. These solvents may be used alone or in combination of two or more types.

[0170] The coating solution may further contain a surfactant, leveling agent or the like for increasing the dispersibility of the charge generating material and charge transport material, and the surface smoothness of the photosensitive layer.

[0171] Surface Protective Layer

[0172] The inorganic surface protective layer is exemplified by a variety of surface protective layers comprising at least one element selected from the group consisting of metallic elements (the elements on the left side of a line interconnecting boron (B) and astatine (At) in the long-form periodic table) and carbon, or an inorganic compound containing any of these elements.

[0173] The surface protective layer may be formed by any of the various known vapor deposition methods including the chemical vapor deposition methods such as plasma CVD, photo CVD and the like, and the physical vapor deposition methods such as sputtering, vacuum deposition, ion plating and the like.

[0174] In the chemical vapor deposition method such as plasma CVD, there are formed:

[0175] 1. a film comprising carbon (C) and/or silicon (Si) of the 14-group elements, that is, carbon (C) film, silicon (Si) film or silicon-carbon (Si—C) composite film;

[0176] 2. a film comprising a compound containing the aforesaid carbon (C) and/or silicon (Si), and at least one element selected from the group consisting of boron (B) and aluminum (Al) of the 13-group elements; nitrogen (Ni) and phosphorus (P) of the 15-group elements; oxygen (0) and sulfur (S) of the 16-group elements; and fluorine (F), chlorine (Cl) and bromine (Br) of the 17-group elements; the film including, for example, silicon-nitrogen (SiN) composite film, silicon-oxygen (SiO) composite film, carbon-fluorine (CF) composite film, carbon-nitrogen (CN) composite film, carbon-boron (CB) composite film, carbon-oxygen (CO) composite film and the like; and

[0177] 3. a film comprising a compound containing boron (B) and/or aluminum (Al) of the 13-group elements, and at least one element selected from the group consisting of the aforesaid elements including nitrogen (N), phosphorus (P), oxygen (O), sulfur (S), fluorine (F), chlorine (Cl) and bromine (Br), the film including, for example, boron-nitrogen (BN) composite film, aluminum-nitrogen (AlN) composite film and the like.

[0178] These films may contain a fractional amount of hydrogen (H) for improved electrical characteristics of the surface protective layer.

[0179] In the chemical vapor deposition method, a usable raw material gas for introduction of a constituent element of the surface protective layer include the molecules of the constituent elements, and compounds thereof such as oxides, hydrides, nitrides and halides thereof, the compounds capable of presenting a gaseous state under normal temperature and pressure conditions or of being readily gassified under film forming conditions. As required, these compounds may be diluted with a gas such as hydrogen gas (H2), helium gas, argon gas, neon gas or the like.

[0180] Specific examples of the raw material gas include:

[0181] silane gas (SiH4) and disilane gas (Si2H6) for silicon introduction;

[0182] methane gas (CH4), ethane gas (C2H6), propane gas (C3H8) and ethylene gas (C2H4) for carbon introduction;

[0183] fluorine gas (F2), bromine monofluoride gas (BrF), chlorine difluoride gas (ClF2), carbon tetrafluoride gas (CF4) and silicon tetrafluoride gas (SiF4) for fluorine introduction;

[0184] nitrogen gas (N2), ammonia gas (NH3), nitrogen oxide gas (NOx) for nitrogen introduction; and

[0185] boron hydride gas such as diborane gas (B2H6), and tetraborane gas (B4H10) for boron introduction; and the like.

[0186] Similarly, the introduction of the other constituent elements may employ compounds capable of presenting a gaseous state under normal temperature and pressure conditions or of being readily gassified under film forming conditions.

[0187] In the physical vapor deposition method, or particularly in the sputtering or ion plating method, there may be formed films, besides the aforesaid films, which each comprise one or more than one metallic elements selected from the group consisting of, for example, gallium (Ga), indium (In) and the like of the 13-group elements; germanium (Ge), tin (Sn), lead (Pb) and the like of the 14-group elements; arsenic (As), antimony (Sb) and the like of the 15-group elements; and selenium (Se) and the like of the 16-group elements, or which each comprise an inorganic compound comprising any of the above metallic elements.

[0188] Preferred as the inorganic surface protective layer are, for example, the carbon (C) film, silicon-carbon (SiC) composite film and the like.

[0189] The thickness of the inorganic surface protective layer may preferably be in the range of 0.01 to 30 μm or particularly of 0.1 to 10 μm.

[0190] The inorganic film defining the surface protective layer may be in any of the amorphous form, microcrystalline form, and crystalline form. Further, the film may comprise a mixture of amorphous and crystalline particles.

[0191] Conductive Substrate

[0192] The conductive substrate may employ substrates formed from various materials having conductivity. Examples of a usable conductive substrate include those formed from metals such as iron, aluminum, copper, tin, platinum, silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel, palladium, indium, stainless steel, brass and the like; those formed from a plastic material on which any of the above metals is deposited or laminated; and glass substrate coated with aluminum iodide, tin oxide, indium oxide or the like.

[0193] In short, the substrate itself may have the conductivity or the surface thereof may have the conductivity. It is preferred that the conductive substrate has a sufficient mechanical strength in use.

[0194] The conductive substrate may have any form, such as sheet, drum and the like, according to the construction of the image forming apparatus to which the conductive substrate is applied.

EXAMPLES

[0195] The invention will hereinbelow be described by way of reference to examples and comparative examples thereof.

[0196] Single-layer Electrophotosensitive Material

Example 1-1

[0197] Forming Single-layer Photosensitive Layer

[0198] A ball mill was operated for 50 hours for dispersing by mixing 5 parts by weight of crystalline X-type metal-free phthalocyanine as the charge generating material represented by the formula (CG-1); 100 parts by weight of poly-N-vinylcarbazole (number-average molecular weight Mn=9500) serving as the positive-hole transport material and the binder resin and having the repeated unit represented by the formula (HT-1); and 40 parts by weight of diphenoquinone compound represented by the formula (1-1-1) in 800 parts by weight of tetrahydrofuran, thereby to prepare a coating solution for single-layer photosensitive layer.

[0199] Subsequently, the resultant coating solution was dip coated on an aluminum tube as the conductive substrate and then was air dried at 100° C. for 30 minutes. Thus was obtained a single-layer photosensitive layer having a thickness of 25 μm.

[0200] Forming Surface Protective Layer

[0201] The aluminum tube formed with the single-layer photosensitive layer was placed in a chamber of a plasma CVD system. The air within the chamber was evacuated to reach a degree of vacuum of 0.67 Pa while a heater of the system was operated to adjust the temperature of the tube to 50° C.

[0202] Subsequently, methane gas (CH4), silane gas (SiH4) and hydrogen gas (H2) were fed into the chamber at respective flow rates listed below, thereby to adjust the degree of vacuum to 0.47 hPa.

[0203] Methane gas: 208 SCCM

[0204] Silane gas: 2.5 SCCM

[0205] Hydrogen gas: 300 SCCM

[0206] In this state, a high-frequency electric field having a frequency of 13.56 MHz and an output of 133 W was applied for causing glow discharge in the chamber. The plasma CVD process was performed for depositing an amorphous silicon-carbon (Sic) composite film at a film growth rate of 0.2 μm/hr, thereby laying a surface protective layer having a thickness of 0.5 μm over the surface of the single-layer photosensitive layer. Thus was fabricated an electrophotosensitive material of Example 1-1.

Examples 1-2 to 1-6

[0207] Electrophotosensitive materials of Examples 1-2 to 1-6 were fabricated the sameway as in Example 1-1, except that each of the examples used 40 parts by weight of diphenoquinone compound of the formula of a number listed in Table 1.

Comparative Example 1-1

[0208] An electrophotosensitive material of Comparative Example 1-1 was fabricated the same way as in Example 1-1, except that the diphenoquinone compound was dispensed with.

Examples 1-7 to 1-12, Comparative Example 1-2

[0209] Electrophotosensitive materials of Examples 1-7 to 1-12 and Comparative Example 1-2 were fabricated the same way as in Examples 1-1 to 1-6 and Comparative Example 1-1, except that the poly-N-vinylcarbazole was replaced by 80 parts by weight of diethylaminobenzaldehyde diphenylhydrazone as the positive-hole transport material represented by the formula (HT-3), and 100 parts by weight of Z-type polycarbonate (weight-average molecular weight Mw=20,000) as the binder resin.

[0210] Photosensitivity Test (I)

[0211] Each of the electrophotosensitive materials of the above examples and comparative examples was charged at +800±20V and the surface potential V0(V) thereof was measured using a drum sensitivity tester available from GENTEC Co.

[0212] A bandpass filter was used to extract monochromatic light from white light from a halogen lamp as a light source of the tester, the monochromatic light having a wavelength of 780 nm and a half width of 20 nm. The surface of the above electrophotosensitive material was irradiated with the monochromatic light at a light intensity of 10 μW/cm2 for 1.0 second while the half-life exposure E½ (μJ/cm2) was determined by measuring the time elapsed before the surface potential V0(V) decreased to half. On the other hand, the residual potential Vr(V) was determined by measuring a surface potential after a lapse of 0.5 seconds from the start of the light exposure.

[0213] Durability Test (I)

[0214] The electrophotosensitive materials of the above examples and comparative examples were each mounted in the drum sensitivity tester available from GENTEC co. The surface of each electrophotosensitive material was charged and exposed to light under the same conditions as in the photosensitivity test (I) and then was exposed to light (wavelength of 660 nm) from an erase lamp of the tester for static elimination. The process of charging, light exposure and static elimination was consecutively repeated in 2,000 cycles with a rotational speed of the electrophotosensitive material set to 40 rpm. Subsequent to the process repeated in cycles, the electrophotosensitive material was subjected to the photosensitivity test (I) again for determining the surface potential v0(v), half-life exposure E½ (μJ/cm2) and residual potential Vr(V).

[0215] Solvent Resistance Test

[0216] The adhesion between the surface protective layer and the organic photosensitive layer was examined as follows. A pipette was used to apply methanol dropwise to the surface of each of the electrophotosensitive materials of the examples and comparative examples and changes of surface were visually observed. The solvent resistance of each electrophotosensitive material was evaluated based on the following criteria:

[0217] ∘: a electrophotosensitive material having a good solvent resistance, suffering no cracks nor delamination of the surface protective layer;

[0218] Δ: a electrophotosensitive material more or less lower in solvent resistance, suffering cracks spread in the overall surface of the surface protective layer which, however, sustained no delamination; and

[0219] ×: a electrophotosensitive material of an unacceptable solvent resistance, suffering the delamination of the surface protective layer. The results are listed in Table 1.

	TABLE 1
	Initial	After durability test
						HLE			HLE
		P-H		SP	RP	E½	SP	RP	E½
	SPL	TM	DPQ	V0(V)	Vr(V)	(μJ/cm2)	V0(V)	Vr(V)	(μJ/cm2)	SRT
Ex. 1-1	a-SiC	HT-1	1-1-1	812	178	1.251	817	185	1.269	◯
Ex. 1-2	a-SiC	HT-1	1-1-8	788	180	1.305	790	186	1.329	◯
Ex. 1-3	a-SiC	HT-1	1-1-18	798	166	1.201	790	164	1.205	◯
Ex. 1-4	a-SiC	HT-1	1-1-22	809	157	1.155	817	162	1.192	◯
Ex. 1-5	a-SiC	HT-1	1-1-24	814	154	1.112	809	158	1.131	◯
Ex. 1-6	a-SiC	HT-1	1-1-30	788	165	1.154	796	168	1.175	◯
C. Ex. 1-1	a-SiC	HT-1	—	817	205	1.500	745	244	1.785	X
Ex. 1-7	a-SiC	HT-3	1-1-1	780	199	1.401	790	194	1.366	◯
Ex. 1-8	a-SiC	HT-3	1-1-8	780	210	1.437	782	210	1.432	◯
Ex. 1-9	a-SiC	HT-3	1-1-18	804	189	1.324	796	191	1.338	◯
Ex. 1-10	a-SiC	HT-3	1-1-22	782	182	1.273	785	182	1.273	◯
Ex. 1-11	a-SiC	HT-3	1-1-24	780	180	1.226	792	170	1.158	◯
Ex. 1-12	a-SiC	HT-3	1-1-30	790	188	1.283	799	190	1.297	◯
C. Ex. 1-2	a-SiC	HT-3	—	804	232	1.667	748	252	1.810	Δ
SPL: Surface Protective Layer
P-H TM: Positive-hole Transport Material
DPQ: Diphenoquinone compound
SP: Surface Potential
RP: Residual Potential
HLE: Half-life Exposure
SRT: Solvent Resistance Test

[0220] It was found from the results of the solvent resistance test listed in the table that the electrophotosensitive material of Comparative Example 1-1 suffered the delamination of the surface protective layer while the electrophotosensitive material of Comparative Example 1-2 sustained cracks. It was thus concluded that where the photosensitive layer does not contain the diphenoquinone compound of the formula (1-1), the effect to improve the physical stability of the inorganic surface protective layer is not obtained.

[0221] It was also found that the electrophotosensitive materials of these comparative examples were significantly decreased in photosensitivity when formed with the surface protective layer, because they presented, in the initial stage, large residual potentials after light exposure and large half-life exposures.

[0222] Furthermore, the electrophotosensitive materials of these comparative examples were found to have poor durability because they were significantly increased in residual potential and half-life exposure after the durability test.

[0223] In contrast, all the electrophotosensitive materials of Examples 1-1 to 1-12 suffered no cracks nor delamination of the surface protective layer in the solvent resistance test. It was thus concluded that the use of the diphenoquinone compound of the formula (1-1) contributed the improvement of the physical stability of the inorganic surface protective layer.

[0224] It was also found that all the electrophotosensitive materials of these examples were free from serious decrease in photosensitivity when formed with the surface protective layer and thus maintained high photosensitivity, because they had small residual potentials after light exposure and half-life exposures.

[0225] In addition, all the electrophotosensitive materials of these examples were free from significant increase in residual potential and half-life exposure after the durability test. Based on this fact and the results of the solvent resistance test, it was concluded that these electrophotosensitive materials achieved greater improvement in durability than the prior-art products.

Examples 1-13 to 1-24, Comparative Examples 1-3, 1-4

[0226] Electrophotosensitive materials of Examples 1-13 to 1-24 and of Comparative Examples 1-3, 1-4 were fabricated the same way as in Examples 1-1 to 1-12 and Comparative Examples 1-1, 1-2, except that the following procedure was taken to form a surface protective layer of amorphous carbon (C) having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the single-layer photosensitive layer.

[0227] Forming Surface Protective Layer

[0228] The aluminum tube formed with the single-layer photosensitive layer was placed in the chamber of the plasma CVD system. The air within the chamber was evacuated to reach a degree of vacuum of 0.67 Pa while the heater of the system was operated to adjust the temperature of the tube to 50° C.

[0229] Subsequently, methane gas (CH4) and hydrogen gas (H2) were fed into the chamber at respective flow rates listed below, thereby to adjust the degree of vacuum to 0.47 hPa.

[0230] Methane gas: 300 SCCM

[0231] Hydrogen gas: 300 SCCM

[0232] In this state, a high-frequency electric field having a frequency of 13.56 MHz and an output of 200 W was applied for causing glow discharge in the chamber. The plasma CVD process was performed for depositing a film of amorphous carbon (C) at a film growth rate of 0.15 μm/hr, thereby forming the surface protective layer of the aforesaid thickness over the surface of the single-layer photosensitive layer.

[0233] The electrophotosensitive materials of the above examples and comparative examples were subjected to the same photosensitivity test (I), durability test (I) and solvent resistance test as the above and evaluated for the characteristics thereof. The results are listed in Table 2.

	TABLE 2
	Initial	After durability test
						HLE			HLE
		P-H		SP	RP	E½	SP	RP	E½
	SPL	TM	DPQ	V0(V)	Vr(V)	(μJ/cm2)	V0(V)	Vr(V)	(μJ/cm2)	SRT
Ex. 1-13	a-C	HT-1	1-1-1	793	170	1.282	804	177	1.302	◯
Ex. 1-14	a-C	HT-1	1-1-8	793	180	1.336	785	177	1.321	◯
Ex. 1-15	a-C	HT-1	1-1-18	780	172	1.222	798	168	1.194	◯
Ex. 1-16	a-C	HT-1	1-1-22	809	163	1.194	801	159	1.165	◯
Ex. 1-17	a-C	HT-1	1-1-24	788	157	1.150	795	159	1.162	◯
Ex. 1-18	a-C	HT-1	1-1-30	798	161	1.175	803	161	1.169	◯
C. Ex. 1-3	a-C	HT-1	—	793	208	1.563	742	238	1.788	X
Ex. 1-19	a-C	HT-3	1-1-1	785	193	1.378	788	193	1.375	◯
Ex. 1-20	a-C	HT-3	1-1-8	780	195	1.413	788	197	1.427	◯
Ex. 1-21	a-C	HT-3	1-1-18	780	182	1.313	793	177	1.295	◯
Ex. 1-22	a-C	HT-3	1-1-22	801	168	1.264	806	175	1.288	◯
Ex. 1-23	a-C	HT-3	1-1-24	809	167	1.218	814	164	1.211	◯
Ex. 1-24	a-C	HT-3	1-1-30	796	179	1.273	814	176	1.252	◯
C. Ex. 1-4	a-C	HT-3	—	788	222	1.667	746	240	1.792	X

[0234] It was confirmed from the table that if the type of the surface protective layer was changed, the same results as the above were obtained according to the compositions of the single-layer photosensitive layer as the base.

[0235] Specifically, it was found in the solvent resistance test that both the electrophotosensitive materials of Comparative Examples 1-3, 1-4 suffered the delamination of the surface protective layer. It was thus concluded that where the photosensitive layer does not contain the diphenoquinone compound of the formula (1-1), the effect to improve the physical stability of the inorganic surface protective layer is not obtained.

[0236] It was also found that the electrophotosensitive materials of these comparative examples were significantly decreased in photosensitivity when formed with the surface protective layer, because they presented, in the initial stage, large residual potentials after light exposure and large half-life exposures.

[0237] Furthermore, the electrophotosensitive materials of these comparative examples were found to have poor durability because they were significantly increased in residual potential and half-life exposure after the durability test.

[0238] In contrast, all the electrophotosensitive materials of Examples 1-13 to 1-24 suffered no cracks nor delamination of the surface protective layer in the solvent resistance test. It was thus confirmed that the use of the diphenoquinone compound of the formula (1-1) contributed the improvement of the physical stability of the inorganic surface protective layer.

[0239] It was also found that all the electrophotosensitive materials of these examples were free from serious decrease in photosensitivity when formed with the surface protective layer and thus maintained high photosensitivity, because they had small residual potentials after light exposure and half-life exposures.

[0240] In addition, all the electrophotosensitive materials of these examples were free from significant increase in residual potential and half-life exposure after the durability test. Based on this fact and the results of the solvent resistance test, it was concluded that these electrophotosensitive materials achieved greater improvement in durability than the prior-art products.

Examples 1-25, 1-26, Comparative Example 1-5

[0241] Electrophotosensitive materials of Examples 1-25, 1-26 and of Comparative Example 1-5 were fabricated the same way as in Examples 1-11, 1-12 and Comparative Examples 1-2, except that the following procedure was taken to form a surface protective layer of amorphous silicon-nitrogen (SiN) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the single-layer photosensitive layer.

[0242] Forming Surface Protective Layer

[0243] The aluminum tube formed with the single-layer photosensitive layer was placed in the chamber of the plasma CVD system. The air within the chamber was evacuated to reach a degree of vacuum of 0.67 Pa while the heater of the system was operated to adjust the temperature of the tube to 50° C.

[0244] Subsequently, silane gas (SiH4), nitrogen gas (N2) and hydrogen gas (H2) were fed into the chamber at respective flow rates listed below, thereby to adjust the degree of vacuum to 0.47 hPa.

[0245] Silane gas: 15 SCCM

[0246] Nitrogen gas: 150 SCCM

[0247] Hydrogen gas: 75 SCCM

[0248] In this state, a high-frequency electric field having a frequency of 13.56 MHz and an output of 150 W was applied for causing glow discharge in the chamber. The plasma CVD process was performed for depositing a silicon-nitrogen (SiN) composite film at a film growth rate of 0.75 μm/hr, thereby forming the surface protective layer of the aforesaid thickness over the surface of the single-layer photosensitive layer.

Examples 1-27, 1-28, Comparative Example 1-6

[0249] Electrophotosensitive materials of Examples 1-27, 1-28 and of Comparative Example 1-6 were fabricated the same way as in Examples 1-11, 1-12 and Comparative Examples 1-2, except that the following procedure was taken to form a surface protective layer of amorphous carbon-nitrogen (CN) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the single-layer photosensitive layer.

[0250] Forming Surface Protective Layer

[0251] The aluminum tube formed with the single-layer photosensitive layer was placed in the chamber of the plasma CVD system. The air within the chamber was evacuated to reach a degree of vacuum of 0.67 Pa while the heater of the system was operated to adjust the temperature of the tube to 50° C.

[0252] Subsequently, methane gas (CH4), nitrogen gas (N2) and hydrogen gas (H2) were fed into the chamber at respective flow rates listed below, thereby to adjust the degree of vacuum to 0.47 hPa.

[0253] Methane gas: 100 SCCM

[0254] Nitrogen gas: 150 SCCM

[0255] Hydrogen gas: 100 SCCM

[0256] In this state, a high-frequency electric field having a frequency of 13.56 MHz and an output of 150 W was applied for causing glow discharge in the chamber. The plasma CVD process was performed for depositing a carbon-nitrogen (CN) composite film at a film growth rate of 0.10 μm/hr, thereby forming the surface protective layer of the aforesaid thickness over the surface of the single-layer photosensitive layer.

[0257] Examples 1-29, 1-30, Comparative Example 1-7

[0258] Electrophotosensitive materials of Examples 1-29, 1-30 and of Comparative Example 1-7 were fabricated the same way as in Examples 1-11, 1-12 and Comparative Examples 1-2, except that the following procedure was taken to form a surface protective layer of amorphous carbon-boron (CB) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the single-layer photosensitive layer.

[0259] Forming Surface Protective Layer

[0260] The aluminum tube formed with the single-layer photosensitive layer was placed in the chamber of the plasma CVD system. The air within the chamber was evacuated to reach a degree of vacuum of 0.67 Pa while the heater of the system was operated to adjust the temperature of the tube to 50° C.

[0261] Subsequently, methane gas (CH4), diborane gas (B2H6) and hydrogen gas (H2) were fed into the chamber at respective flow rates listed below, thereby to adjust the degree of vacuum to 0.47 hPa.

[0262] Methane gas: 100 SCCM

[0263] Diborane gas: 200 SCCM

[0264] Hydrogen gas: 100 SCCM

[0265] In this state, a high-frequency electric field having a frequency of 13.56 MHz and an output of 150 W was applied for causing glow discharge in the chamber. The plasma CVD process was performed for depositing a carbon-boron (CB) composite film at a film growth rate of 0.10 μm/hr, thereby forming the surface protective layer of the aforesaid thickness over the surface of the single-layer photosensitive layer.

Examples 1-31, 1-32, Comparative Example 1-8

[0266] Electrophotosensitive materials of Examples 1-31, 1-32 and of Comparative Example 1-8 were fabricated the same way as in Examples 1-11, 1-12 and Comparative Examples 1-2, except that the following procedure was taken to form a surface protective layer of amorphous carbon-fluorine (CF) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the single-layer photosensitive layer.

[0267] Forming Surface Protective Layer

[0268] The aluminum tube formed with the single-layer photosensitive layer was placed in the chamber of the plasma CVD system. The air within the chamber was evacuated to reach a degree of vacuum of 0.67 Pa while the heater of the system was operated to adjust the temperature of the tube to 50° C.

[0269] Subsequently, methane gas (CH4), carbon tetrafluoride gas (CF4) and hydrogen gas (H2) were fed into the chamber at respective flow rates listed below, thereby to adjust the degree of vacuum to 0.47 hPa.

[0270] Methane gas: 100 SCCM

[0271] Carbon tetrafluoride gas: 100 SCCM

[0272] Hydrogen gas: 100 SCCM

[0273] In this state, a high-frequency electric field having a frequency of 13.56 MHz and an output of 150 W was applied for causing glow discharge in the chamber. The plasma CVD process was performed for depositing a carbon-fluorine (CF) composite film at a film growth rate of 0.10 μm/hr, thereby forming the surface protective layer of the aforesaid thickness over the surface of the single-layer photosensitive layer.

Examples 1-33, 1-34, Comparative Example 1-9

[0274] Electrophotosensitive materials of Examples 1-33, 1-34 and of Comparative Example 1-9 were fabricated the same way as in Examples 1-11, 1-12 and Comparative Examples 1-2, except that the following procedure was taken to form a surface protective layer of amorphous boron-nitrogen (BN) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the single-layer photosensitive layer.

[0275] Forming Surface Protective Layer

[0276] The aluminum tube formed with the single-layer photosensitive layer was placed in the chamber of the plasma CVD system. The air within the chamber was evacuated to reach a degree of vacuum of 0.67 Pa while the heater of the system was operated to adjust the temperature of the tube to 50° C.

[0277] Subsequently, diborane gas (B2H6), nitrogen gas (N2) and hydrogen gas (H2) were fed into the chamber at respective flow rates listed below, thereby to adjust the degree of vacuum to 0.47 hPa.

[0278] Diborane gas: 200 SCCM

[0279] Nitrogen gas: 150 SCCM

[0280] Hydrogen gas: 150 SCCM

[0281] In this state, a high-frequency electric field having a frequency of 13.56 MHz and an output of 150 W was applied for causing glow discharge in the chamber. The plasma CVD process was performed for depositing a boron-nitrogen (BN) composite film at a film growth rate of 0.08 μm/hr, thereby forming the surface protective layer of the aforesaid thickness over the surface of the single-layer photosensitive layer.

[0282] The electrophotosensitive materials of the above examples and comparative examples were subjected to the same photosensitivity test (I), durability test (I) and solvent resistance test as the above and evaluated for the characteristics thereof. The results are listed in Table 3.

	TABLE 3
	Initial	After durability test
						HLE			HLE
		P-H		SP	RP	E½	SP	RP	E½
	SPL	TM	DPQ	V0(V)	Vr(V)	(μJ/cm2)	V0(V)	Vr(V)	(μJ/cm2)	SRT
Ex. 1-25	a-SiN	HT-3	1-1-24	798	187	1.334	795	190	1.355	◯
Ex. 1-26	a-SiN	HT-3	1-1-30	798	192	1.386	809	190	1.372	◯
C. Ex. 1-5	a-SiN	HT-3	—	812	245	1.787	749	263	1.918	Δ
Ex. 1-27	a-CN	HT-3	1-1-24	801	194	1.389	793	194	1.389	◯
Ex. 1-28	a-CN	HT-3	1-1-30	780	203	1.443	804	205	1.457	◯
C. Ex. 1-6	a-CN	HT-3	—	790	252	1.875	752	270	2.009	Δ
Ex. 1-29	a-CB	HT-3	1-1-24	798	166	1.235	812	164	1.220	◯
Ex. 1-30	a-CB	HT-3	1-1-30	806	175	1.282	812	180	1.319	◯
C. Ex. 1-7	a-CB	HT-3	—	801	222	1.667	746	238	1.787	X
Ex. 1-31	a-CF	HT-3	1-1-24	782	180	1.284	796	182	1.298	◯
Ex. 1-32	a-CF	HT-3	1-1-30	790	187	1.353	796	185	1.339	◯
C. Ex. 1-8	a-CF	HT-3	—	788	232	1.745	734	248	1.865	X
Ex. 1-33	a-BN	HT-3	1-1-24	788	155	1.165	802	157	1.180	◯
Ex. 1-34	a-BN	HT-3	1-1-30	785	155	1.199	789	162	1.253	◯
C. Ex. 1-9	a-BN	HT-3	—	785	203	1.595	752	233	1.831	X

[0283] It was confirmed from the table that if the type of the surface protective layer was further changed, the same results as the above were obtained according to the compositions of the single-layer photosensitive layer as the base.

[0284] Specifically, it was found from the results of the solvent resistance test that all the electrophotosensitive materials of Comparative Examples 1-7 to 1-9 suffered the delamination of the surface protective layer. The electrophotosensitive materials of Comparative Examples 1-5, 1-6 were found to sustain cracks. It was thus concluded that where the photosensitive layer does not contain the diphenoquinone compound of the formula (1-1), the effect to improve the physical stability of the inorganic surface protective layer is not obtained.

[0285] It was also found that the electrophotosensitive materials of these comparative examples were significantly decreased in photosensitivity when formed with the surface protective layer, because they presented, in the initial stage, large residual potentials after light exposure and large half-life exposures.

[0286] Furthermore, the electrophotosensitive materials of these comparative examples were found to have poor durability because they were significantly increased in residual potential and half-life exposure after the durability test.

[0287] In contrast, all the electrophotosensitive materials of Examples 1-25 to 1-34 suffered no cracks nor delamination of the surface protective layer in the solvent resistance test. It was thus confirmed that the use of the diphenoquinone compound of the formula (1-1) contributed the improvement of the physical stability of the inorganic surface protective layer.

[0288] It was also confirmed that all the electrophotosensitive materials of these examples were free from serious decrease in photosensitivity when formed with the surface protective layer and thus maintained high photosensitivity, because they had small residual potentials after light exposure and half-life exposures.

[0289] In addition, all the electrophotosensitive materials of these examples were free from significant increase in residual potential and half-life exposure after the durability test. Based on this fact and the results of the solvent resistance test, it was concluded that these electrophotosensitive materials achieved greater improvement in durability than the prior-art products.

[0290] Multi-layer Electrophotosensitive Material

Example 1-35

[0291] Forming Multi-layer Photosensitive Layer

[0292] The ball mill was operated for dispersing by mixing 2.5 parts by weight of crystalline X-type metal-free phthalocyanine as the charge generating material represented by the formula (CG-1), and 1 part by weight of polyvinylbutyral as the binder resin in 15 parts by weight of tetrahydrofuran, thereby to prepare a coating solution for charge generating layer of the multi-layer photosensitive layer.

[0293] Subsequently, the resultant coating solution was dip coated on the aluminum tube as the conductive substrate and then was air dried at 110° C. for 30 minutes. Thus was formed a charge generating layer having a thickness of 0.5 μm.

[0294] The ball mill was operated for dispersing by mixing 1 part by weight of poly-N-vinylcarbazole (number-average molecular weight Mn=9500) serving as the positive-hole transport material and the binder resin and having the repeated unit represented by the formula (HT-1), and 0.2 parts by weight of diphenoquinone compound represented by the formula (1-1-1) in 10 parts by weight of tetrahydrofuran, thereby to prepare a coating solution for charge transport layer of the multi-layer photosensitive layer.

[0295] Subsequently, the resultant coating solution was dip coated on the above charge generating layer and then was air dried at 110° C. for 30 minutes, thereby to form a charge transport layer having a thickness of 20 μm. Thus was formed a negative-charge multi-layer photosensitive layer.

[0296] Forming Surface Protective Layer

[0297] The plasma CVD process was performed under the same conditions as in Example 1-1, thereby forming a surface protective layer of amorphous silicon-carbon (SiC) composite film having a thickness of 0.5 μm. Thus was fabricated an electrophotosensitive material of Example 1-35.

Examples 1-36 to 1-40

[0298] Electrophotosensitive materials of Examples 1-36 to 1-40 were fabricated the same way as in Example 1-35 except that each of the examples used 0.2 parts by weight of diphenoquinone compound of the formula of a number listed in Table 4.

Comparative Example 1-10

[0299] An electrophotosensitive material of Comparative Example 1-10 was fabricated the same way as in Example 1-35 except that the diphenoquinone compound was dispensed with.

Examples 1-41 to 1-46, Comparative Example 1-11

[0300] Electrophotosensitive materials of Examples 1-41 to 1-46 and Comparative Example 1-11 were fabricated the same way as in Examples 1-35 to 1-40 and Comparative Example 1-10, except that the poly-N-vinylcarbazole was replaced by 0.8 parts by weight of diethylaminobenzaldehyde diphenylhydrazone as the positive-hole transport material represented by the formula (HT-3) and 1 part by weight of Z-type polycarbonate (weight-average molecular weight Mw=20,000) as the binder resin.

[0301] Photosensitivity Test (II)

[0302] Each of the electrophotosensitive materials of the above examples and comparative examples was charged at −800±20V and the surface potential V0(V) thereof was measured using a drum sensitivity tester available from GENTEC Co.

[0303] A bandpass filter was used to extract monochromatic light from white light from a halogen lamp as a light source of the tester, the monochromatic light having a wavelength of 780 nm and a half width of 20 nm. The surface of the above electrophotosensitive material was irradiated with the monochromatic light at a light intensity of 10 μW/cm2 for 1.0 second while the half-life exposure E½ (μJ/cm2) was determined by measuring the time elapsed before the surface potential V0(V) decreased to half. On the other hand, the residual potential Vr(V) was determined by measuring a surface potential after a lapse of 0.5 seconds from the start of the light exposure.

[0304] Durability Test (II)

[0305] The electrophotosensitive materials of the above examples and comparative examples were each mounted in the drum sensitivity tester available from GENTEC Co. The surface of each electrophotosensitive material was charged and exposed to light under the same conditions as in the photosensitivity test (II) and then was exposed to light (wavelength of 660 nm) from an erase lamp of the tester for static elimination. The process of charging, light exposure and static elimination was consecutively repeated in 2,000 cycles with a rotational speed of the electrophotosensitive material set to 40 rpm. Subsequent to the process repeated in cycles, the electrophotosensitive material was subjected to the photosensitivity test (II) again for determining the surface potential V0(V), half-life exposure E½ (μJ/cm2) and residual potential Vr(V).

[0306] The results of the above tests as well as those of the aforementioned solvent resistance test are listed in Table 4.

	TABLE 4
	Initial	After durability test
						HLE			HLE
		P-H		SP	RP	E½	SP	RP	E½
	SPL	TM	DPQ	V0(V)	Vr(V)	(μJ/cm2)	V0(V)	Vr(V)	(μJ/cm2)	SRT
Ex. 1-35	a-SiC	HT-1	1-1-1	−782	−161	0.911	−785	−163	0.922	◯
Ex. 1-36	a-SiC	HT-1	1-1-8	−804	−153	0.911	−805	−158	0.941	◯
Ex. 1-37	a-SiC	HT-1	1-1-18	−812	−164	0.929	−810	−167	0.946	◯
Ex. 1-38	a-SiC	HT-1	1-1-22	−804	−155	0.920	−806	−160	0.950	◯
Ex. 1-39	a-SiC	HT-1	1-1-24	−790	−156	0.885	−798	−154	0.881	◯
Ex. 1-40	a-SiC	HT-1	1-1-30	−809	−158	0.894	−813	−160	0.905	◯
C. Ex. 1-10	a-SiC	HT-1	—	−806	−165	0.938	−782	−192	1.052	X
Ex. 1-41	a-SiC	HT-3	1-1-1	−809	−137	0.985	−798	−139	0.999	◯
Ex. 1-42	a-SiC	HT-3	1-1-8	−780	−140	1.005	−796	−146	1.048	◯
Ex. 1-43	a-SiC	HT-3	1-1-18	−814	−137	1.025	−802	−140	1.047	◯
Ex. 1-44	a-SiC	HT-3	1-1-22	−806	−142	0.985	−801	−148	1.027	◯
Ex. 1-45	a-SiC	HT-3	1-1-24	−790	−138	0.957	−782	−135	0.936	◯
Ex. 1-46	a-SiC	HT-3	1-1-30	−798	−134	0.985	−788	−132	0.970	◯
C. Ex. 1-11	a-SiC	HT-3	—	−814	−147	1.024	−776	−176	1.226	X

[0307] It was confirmed from the table that if the single-layer photosensitive layer was replaced by the multi-layer photosensitive layer, the same results as the above were obtained according to the compositions of the charge-transport layer defining the outermost part thereof.

[0308] Specifically, it was found in the solvent resistance test that both the electrophotosensitive materials of Comparative Examples 1-10, 1-11 suffered the delamination of the surface protective layer. It was thus concluded that where the photosensitive layer does not contain the diphenoquinone compound of the formula (1-1), the effect to improve the physical stability of the inorganic surface protective layer is not obtained.

[0309] It was also found that the electrophotosensitive materials of these comparative examples were significantly decreased in photosensitivity when formed with the surface protective layer, because they presented, in the initial stage, large residual potentials after light exposure and large half-life exposures.

[0310] Furthermore, the electrophotosensitive materials of these comparative examples were found to have poor durability because they were significantly increased in residual potential and half-life exposure after the durability test.

[0311] In contrast, all the electrophotosensitive materials of Examples 1-35 to 1-46 suffered no cracks nor delamination of the surface protective layer in the solvent resistance test. It was thus confirmed that the use of the diphenoquinone compound of the formula (1-1) contributed the improvement of the physical stability of the inorganic surface protective layer.

[0312] It was also confirmed that all the electrophotosensitive materials of these examples were free from serious decrease in photosensitivity when formed with the surface protective layer and thus maintained high photosensitivity, because they had small residual potentials after light exposure and half-life exposures.

[0313] In addition, all the electrophotosensitive materials of these examples were free from significant increase in residual potential and half-life exposure after the durability test. Based on this fact and the results of the solvent resistance test, it was concluded that these electrophotosensitive materials achieved greater improvement in durability than the prior-art products.

Examples 1-47 to 1-58, Comparative Examples 1-12, 1-13

[0314] Electrophotosensitive materials of these examples and comparative examples were fabricated the same way as in Examples 1-35 to 1-46 and Comparative Examples 1-10, 1-11, except that the same procedure as in Examples 1-13 to 1-24 and Comparative Examples 1-3, 1-4 was taken to form a surface protective layer of amorphous carbon (C) having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over a surface of the multi-layer photosensitive layer.

[0315] The electrophotosensitive materials of the above examples and comparative examples were subjected to the same photosensitivity test (II), durability test (II) and solvent resistance test as the above and were evaluated for the characteristics thereof. The results are listed in Table 5

	TABLE 5
	Initial	After durability test
						HLE			HLE
		P-H		SP	RP	E½	SP	RP	E½
	SPL	TM	DPQ	V0(V)	Vr(V)	(μJ/cm2)	V0(V)	Vr(V)	(μJ/cm2)	SRT
Ex. 1-47	a-C	HT-1	1-1-1	−788	−161	1.170	−790	−163	1.184	◯
Ex. 1-48	a-C	HT-1	1-1-8	−809	−166	1.205	−798	−163	1.181	◯
Ex. 1-49	a-C	HT-1	1-1-18	−798	−163	1.204	−795	−169	1.242	◯
Ex. 1-50	a-C	HT-1	1-1-22	−801	−164	1.192	−812	−162	1.177	◯
Ex. 1-51	a-C	HT-1	1-1-24	−798	−162	1.158	−790	−164	1.172	◯
Ex. 1-52	a-C	HT-1	1-1-30	−785	−165	1.181	−798	−170	1.215	◯
C. Ex. 1-12	a-C	HT-1	—	−785	−172	1.216	−748	−198	1.400	X
Ex. 1-53	a-C	HT-3	1-1-1	−814	−141	1.056	−806	−143	1.071	◯
Ex. 1-54	a-C	HT-3	1-1-8	−809	−134	1.077	−814	−139	1.107	◯
Ex. 1-55	a-C	HT-3	1-1-18	−793	−135	1.088	−790	−141	1.116	◯
Ex. 1-56	a-C	HT-3	1-1-22	−817	−144	1.077	−807	−146	1.092	◯
Ex. 1-57	a-C	HT-3	1-1-24	−780	−141	1.056	−793	−143	1.071	◯
Ex. 1-58	a-C	HT-3	1-1-30	−812	−136	1.056	−814	−140	1.077	◯
C. Ex. 1-13	a-C	HT-3	—	−817	−146	1.098	−771	−178	1.339	X

[0316] It was confirmed from the table that if the type of the surface protective layer was changed, the same results as the above were obtained according to the compositions of the charge-transport layer of the multi-layer photosensitive layer as the base.

[0317] Specifically, it was found in the solvent resistance test that both the electrophotosensitive materials of Comparative Examples 1-12, 1-13 suffered the delamination of the surface protective layer. It was thus concluded that where the photosensitive layer does not contain the diphenoquinone compound of the formula (1-1), the effect to improve the physical stability of the inorganic surface protective layer is not obtained.

[0318] It was also found that the electrophotosensitive materials of these comparative examples were significantly decreased in photosensitivity when formed with the surface protective layer, because they presented, in the initial stage, large residual potentials after light exposure and large half-life exposures.

[0319] Furthermore, the electrophotosensitive materials of these comparative examples were found to have poor durability because they were significantly increased in residual potential and half-life exposure after the durability test.

[0320] In contrast, all the electrophotosensitive materials of Examples 1-47 to 1-58 suffered no cracks nor delamination of the surface protective layer in the solvent resistance test. It was thus confirmed that the use of the diphenoquinone compound of the formula (1-1) contributed the improvement of the physical stability of the inorganic surface protective layer.

[0321] It was also confirmed that all the electrophotosensitive materials of these examples were free from serious decrease in photosensitivity when formed with the surface protective layer and thus maintained high photosensitivity, because they had small residual potentials after light exposure and half-life exposures.

[0322] In addition, all the electrophotosensitive materials of these examples were free from significant increase in residual potential and half-life exposure after the durability test. Based on this fact and the results of the solvent resistance test, it was concluded that these electrophotosensitive materials achieved greater improvement in durability than the prior-art products.

Examples 1-59, 1-60, Comparative Example 1-14

[0323] Electrophotosensitive materials of these examples and comparative example were fabricated the same way as in Examples 1-45, 1-46 and Comparative Example 1-11, except that the same procedure as in Examples 1-25, 1-26 and Comparative Example 1-5 was taken to form a surface protective layer of amorphous silicon-nitrogen (SiN) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the multi-layer photosensitive layer.

Examples 1-61, 1-62, Comparative Example 1-15

[0324] Electrophotosensitive materials of these examples and comparative example were fabricated the same way as in Examples 1-45, 1-46 and Comparative Example 1-11, except that the same procedure as in Examples 1-27, 1-28 and Comparative Example 1-6 was taken to form a surface protective layer of amorphous carbon-nitrogen (CN) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the multi-layer photosensitive layer.

Examples 1-63, 1-64, Comparative Example 1-16

[0325] Electrophotosensitive materials of these examples and comparative example were fabricated the same way as in Examples 1-45, 1-46 and Comparative Example 1-11, except that the same procedure as in Examples 1-29, 1-30 and Comparative Example 1-7 was taken to form a surface protective layer of amorphous carbon-boron (CB) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the multi-layer photosensitive layer.

Examples 1-65, 1-66, Comparative Example 1-17

[0326] Electrophotosensitive materials of these examples and comparative example were fabricated the same way as in Examples 1-45, 1-46 and Comparative Example 1-11, except that the same procedure as in Examples 1-31, 1-32 and Comparative Example 1-8 was taken to form a surface protective layer of amorphous carbon-fluorine (CF) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the multi-layer photosensitive layer.

Examples 1-67, 1-68, Comparative Example 1-18

[0327] Electrophotosensitive materials of these examples and comparative example were fabricated the same way as in Examples 1-45, 1-46 and Comparative Example 1-11, except that the same procedure as in Examples 1-33, 1-34 and Comparative Example 1-9 was taken to form a surface protective layer of amorphous boron-nitrogen (BN) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the multi-layer photosensitive layer.

[0328] The electrophotosensitive materials of the above examples and comparative examples were subjected to the same photosensitivity test (II), durability test (II) and solvent resistance test as the above and were evaluated for the characteristics thereof. The results are listed in Table 6.

	TABLE 6
	Initial	After durability test
						HLE			HLE
		P-H		SP	RP	E½	SP	RP	E½
	SPL	TM	DPQ	V0(V)	Vr(V)	(μJ/cm2)	V0(V)	Vr(V)	(μJ/cm2)	SRT
Ex. 1-59	a-SiN	HT-3	1-1-24	−788	−145	1.085	−780	−143	1.087	◯
Ex. 1-60	a-SiN	HT-3	1-1-30	−793	−144	1.064	−804	−138	1.060	◯
C. Ex. 1-14	a-SiN	HT-3	—	−785	−149	1.095	−758	−186	1.367	Δ
Ex. 1-61	a-CN	HT-3	1-1-24	−801	−148	1.132	−801	−144	1.112	◯
Ex. 1-62	a-CN	HT-3	1-1-30	−804	−157	0.902	−804	−158	0.914	◯
C. Ex. 1-15	a-CN	HT-3	—	−793	−148	1.156	−762	−177	1.381	X
Ex. 1-63	a-CB	HT-3	1-1-24	−798	−126	0.951	−790	−134	1.001	◯
Ex. 1-64	a-CB	HT-3	1-1-30	−806	−124	0.951	−817	−134	1.016	◯
C. Ex. 1-16	a-CB	HT-3	—	−793	−137	0.979	−746	−167	1.193	X
Ex. 1-65	a-CF	HT-3	1-1-24	−790	−129	1.000	−788	−132	1.023	◯
Ex. 1-66	a-CF	HT-3	1-1-30	−782	−127	0.991	−788	−138	1.047	◯
C. Ex. 1-17	a-CF	HT-3	—	−793	−139	1.021	−766	−178	1.307	X
Ex. 1-67	a-BN	HT-3	1-1-24	−790	−117	0.903	−780	−120	0.926	◯
Ex. 1-68	a-BN	HT-3	1-1-30	−806	−116	0.895	−814	−114	0.897	◯
C. Ex. 1-18	a-BN	HT-3	—	−780	−117	0.904	−748	−146	1.128	X

[0329] It was confirmed from the table that if the type of the surface protective layer was further changed, the same results as the above were obtained according to the compositions of the charge-transport layer of the multi-layer photosensitive layer as the base.

[0330] Specifically, it was found from the results of the solvent resistance test that both the electrophotosensitive materials of Comparative Examples 1-15 to 1-18 suffered the delamination of the surface protective layer. The electrophotosensitive material of Comparative Example 1-14 was found to sustain cracks. It was thus concluded that where the photosensitive layer does not contain the diphenoquinone compound of the formula (1-1), the effect to improve the physical stability of the inorganic surface protective layer is not obtained.

[0331] It was also found that the electrophotosensitive materials of these comparative examples were significantly decreased in photosensitivity when formed with the surface protective layer, because they presented, in the initial stage, large residual potentials after light exposure and large half-life exposures.

[0332] Furthermore, the electrophotosensitive materials of these comparative examples were found to have poor durability because they were significantly increased in residual potential and half-life exposure after the durability test.

[0333] In contrast, all the electrophotosensitive materials of Examples 1-59 to 1-68 suffered no cracks nor delamination of the surface protective layer in the solvent resistance test. It was thus confirmed that the use of the diphenoquinone compound of the formula (1-1) contributed the improvement of the physical stability of the inorganic surface protective layer.

[0334] It was also confirmed that all the electrophotosensitive materials of these examples were free from serious decrease in photosensitivity when formed with the surface protective layer and thus maintained high photosensitivity, because they had small residual potentials after light exposure and half-life exposures.

[0335] In addition, all the electrophotosensitive materials of these examples were free from significant increase in residual potential and half-life exposure after the durability test. Based on this fact and the results of the solvent resistance test, it was concluded that these electrophotosensitive materials achieved greater improvement in durability than the prior-art products.

[0336] Single-layer Electrophotosensitive Material

Examples 2-1 to 2-5

[0337] Electrophotosensitive materials of Examples 2-1 to 2-5 were fabricated the same way as in Example 1-1, except that each of the examples used 40 parts by weight of dinaphthoquinone compound of the formula of a number listed in Table 7.

Examples 2-6 to 2-10

[0338] Electrophotosensitive materials of Examples 2-6 to 2-10 were fabricated the same way as in Example 1-7, except that each of the examples used 40 parts by weight of dinaphthoquinone compound of the formula of a number listed in Table 7.

[0339] The electrophotosensitive materials of the above examples were subjected to the same photosensitivity test (I), durability test (I) and solvent resistance test as the above and were evaluated for the characteristics thereof. The results as well as those of Comparative Examples 1-1, 1-2 are listed in Table 7.

	TABLE 7
	Initial	After durability test
						HLE			HLE
		P-H		SP	RP	E½	SP	RP	E½
	SPL	TM	DNQ	V0(V)	Vr(V)	(μJ/cm2)	V0(V)	Vr(V)	(μJ/cm2)	SRT
Ex. 2-1	a-SiC	HT-1	1-2-3	814	141	1.035	812	143	1.050	◯
Ex. 2-2	a-SiC	HT-1	1-2-4	782	156	1.072	793	153	1.051	◯
Ex. 2-3	a-SiC	HT-1	1-2-5	780	146	1.001	782	139	0.953	◯
Ex. 2-4	a-SiC	HT-1	1-2-6	812	167	1.154	804	160	1.106	◯
Ex. 2-5	a-SiC	HT-1	1-2-8	790	166	1.200	798	169	1.222	◯
C. Ex. 1-1	a-SiC	HT-1	—	817	205	1.500	745	244	1.785	X
Ex. 2-6	a-SiC	HT-3	1-2-3	788	158	1.143	782	165	1.194	◯
Ex. 2-7	a-SiC	HT-3	1-2-4	817	170	1.209	809	168	1.195	◯
Ex. 2-8	a-SiC	HT-3	1-2-5	780	160	1.097	785	160	1.097	◯
Ex. 2-9	a-SiC	HT-3	1-2-6	814	175	1.264	814	175	1.264	◯
Ex. 2-10	a-SiC	HT-3	1-2-8	793	191	1.303	788	188	1.283	◯
C. Ex. 1-2	a-SiC	HT-3	—	804	232	1.667	748	252	1.810	Δ
DNQ: Dinaphtoquinone compound

[0340] According to the results of the solvent resistance test, all the electrophotosensitive materials of Examples 2-1 to 2-10 suffered no cracks nor delamination of the surface protective layer. It was thus concluded that the use of the dinaphthoquinone compound of the formula (1-2) contributed the improvement of the physical stability of the inorganic surface protective layer.

[0341] It was also confirmed that all the electrophotosensitive materials of these examples were free from serious decrease in photosensitivity when formed with the surface protective layer and thus maintained high photosensitivity, becausethey had small residual potentials after light exposure and half-life exposures.

[0342] In addition, all the electrophotosensitive materials of these examples were free from significant increase in residual potential and half-life exposure after the durability test. Based on this fact and the results of the solvent resistance test, it was concluded that these electrophotosensitive materials achieved greater improvement in durability than the prior-art products.

Examples 2-11 to 2-20

[0343] Electrophotosensitive materials of Examples 2-11 to 2-20 were fabricated the same way as in Examples 2-1 to 2-10, except that the same procedure as in Examples 1-13 to 1-24 was taken to form a surface protective layer of amorphous carbon (C) having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the single-layer photosensitive layer.

[0344] The electrophotosensitive materials of these examples were subjected to the same photosensitivity test (I), durability test (I) and solvent resistance test as the above and were evaluated for the characteristics thereof. The results as well as those of Comparative Examples 1-3, 1-4 are listed in Table 8.

	TABLE 8
	Initial	After durability test
						HLE			HLE
		P-H		SP	RP	E½	SP	RP	E½
	SPL	TM	DNQ	V0(V)	Vr(V)	(μJ/cm2)	V0(V)	Vr(V)	(μJ/cm2)	SRT
Ex. 2-11	a-C	HT-1	1-2-3	793	146	1.086	801	151	1.123	◯
Ex. 2-12	a-C	HT-1	1-2-4	804	157	1.150	795	162	1.187	◯
Ex. 2-13	a-C	HT-1	1-2-5	806	145	1.056	814	145	1.056	◯
Ex. 2-14	a-C	HT-1	1-2-6	804	172	1.222	801	162	1.151	◯
Ex. 2-15	a-C	HT-1	1-2-8	801	166	1.251	809	166	1.251	◯
C. Ex. 1-3	a-C	HT-1	—	793	208	1.563	742	238	1.788	X
Ex. 2-16	a-C	HT-3	1-2-3	814	153	1.150	798	155	1.203	◯
Ex. 2-17	a-C	HT-3	1-2-4	806	171	1.235	801	174	1.257	◯
Ex. 2-18	a-C	HT-3	1-2-5	785	158	1.119	801	151	1.069	◯
Ex. 2-19	a-C	HT-3	1-2-6	793	170	1.283	817	170	1.283	◯
Ex. 2-20	a-C	HT-3	1-2-8	817	179	1.345	814	184	1.383	◯
C. Ex. 1-4	a-C	HT-3	—	788	222	1.667	746	240	1.792	X

[0345] It was confirmed from the table that if the type of the surface protective layer was changed, the same results as the above were obtained according to the compositions of the single-layer photosensitive layer as the base.

[0346] Specifically, it was found from the results of the solvent resistance test that all the electrophotosensitive materials of Examples 2-11 to 2-20 suffered no cracks nor delamination of the surface protective layer. It was thus confirmed that the use of the dinaphthoquinone compound of the formula (1-2) contributed the improvement of the physical stability of the inorganic surface protective layer.

[0347] It was also confirmed that all the electrophotosensitive materials of these examples were free from serious decrease in photosensitivity when formed with the surface protective layer and thus maintained high photosensitivity, because they had small residual potentials after light exposure and half-life exposures.

[0348] In addition, all the electrophotosensitive materials of these examples were free from significant increase in residual potential and half-life exposure after the durability test. Based on this fact and the results of the solvent resistance test, it was concluded that these electrophotosensitive materials achieved greater improvement in durability than the prior-art products.

Examples 2-21, 2-22

[0349] Electrophotosensitive materials of Examples 2-21, 2-22 were fabricated the same way as in Examples 2-7, 2-8 except that the same procedure as in Examples 1-25, 1-26 was taken to form a surface protective layer of amorphous silicon-nitrogen (SiN) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the single-layer photosensitive layer.

Examples 2-23, 2-24

[0350] Electrophotosensitive materials of Examples 2-23, 2-24 were fabricated the same way as in Examples 2-7, 2-8 except that the same procedure as in Examples 1-27, 1-28 was taken to form a surface protective layer of amorphous carbon-nitrogen (CN) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the single-layer photosensitive layer.

Examples 2-25, 2-26

[0351] Electrophotosensitive materials of Examples 2-25, 2-26 were fabricated the same way as in Examples 2-7, 2-8 except that the same procedure as in Examples 1-29, 1-30 was taken to form a surface protective layer of amorphous carbon-boron (CB) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the single-layer photosensitive layer.

Examples 2-27, 2-28

[0352] Electrophotosensitive materials of Examples 2-27, 2-28 were fabricated the same way as in Examples 2-7, 2-8 except that the same procedure as in Examples 1-31, 1-32 was taken to form a surface protective layer of amorphous carbon-fluorine (CF) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the single-layer photosensitive layer.

Examples 2-29, 2-30

[0353] Electrophotosensitive materials of Examples 2-29, 2-30 were fabricated the same way as in Examples 2-7, 2-8 except that the same procedure as in Examples 1-33, 1-34 was taken to form a surface protective layer of amorphous boron-nitrogen (BN) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the single-layer photosensitive layer.

[0354] The electrophotosensitive materials of the above examples were subjected to the same photosensitivity test (I), durability test (I) and solvent resistance test as the above and were evaluated for the characteristics thereof. The results as well as those of Comparative Examples 1-5 to 1-9 are listed in Table 9.

	TABLE 9
	Initial	After durability test
						HLE			HLE
		P-H		SP	RP	E½	SP	RP	E½
	SPL	TM	DNQ	V0(V)	Vr(V)	(μJ/cm2)	V0(V)	Vr(V)	(μJ/cm2)	SRT
Ex. 2-21	a-SiN	HT-3	1-2-4	817	185	1.334	806	187	1.331	◯
Ex. 2-22	a-SiN	HT-3	1-2-5	788	189	1.386	798	197	1.382	◯
C. Ex. 1-5	a-SiN	HT-3	—	812	245	1.787	749	263	1.918	Δ
Ex. 2-23	a-CN	HT-3	1-2-4	796	186	1.389	814	186	1.392	◯
Ex. 2-24	a-CN	HT-3	1-2-5	809	193	1.443	809	193	1.442	◯
C. Ex. 1-6	a-CN	HT-3	—	790	252	1.875	752	270	2.009	Δ
Ex. 2-25	a-CB	HT-3	1-2-4	785	171	1.235	780	171	1.236	◯
Ex. 2-26	a-CB	HT-3	1-2-5	812	173	1.283	801	175	1.281	◯
C. Ex. 1-7	a-CB	HT-3	—	801	222	1.667	746	238	1.787	X
Ex. 2-27	a-CF	HT-3	1-2-4	801	180	1.283	814	180	1.285	◯
Ex. 2-28	a-CF	HT-3	1-2-5	790	187	1.353	801	187	1.351	◯
C. Ex. 1-8	a-CF	HT-3	—	788	232	1.745	734	248	1.865	X
Ex. 2-29	a-BN	HT-3	1-2-4	806	150	1.164	806	153	1.226	◯
Ex. 2-30	a-BN	HT-3	1-2-5	806	155	1.199	812	160	1.238	◯
C. Ex. 1-9	a-BN	HT-3	—	785	203	1.595	752	233	1.831	X

[0355] It was confirmed from the table that if the type of the surface protective layer was further changed, the same results as the above were obtained according to the compositions of the single-layer photosensitive layer as the base.

[0356] According to the results of the solvent resistance test listed in the table, all the electrophotosensitive materials of Examples 2-21 to 2-30 suffered no cracks nor delamination of the surface protective layer. It was thus concluded that the use of the dinaphthoquinone compound of the formula (1-2) contributed the improvement of the physical stability of the inorganic surface protective layer.

[0357] It was also confirmed that all the electrophotosensitive materials of these examples were free from serious decrease in photosensitivity when formed with the surface protective layer and thus maintained high photosensitivity, because they had small residual potentials after light exposure and half-life exposures.

[0358] In addition, all the electrophotosensitive materials of these examples were free from significant increase in residual potential and half-life exposure after the durability test. Based on this fact and the results of the solvent resistance test, it was concluded that these electrophotosensitive materials achieved greater improvement in durability than the prior-art products.

[0359] Multi-layer Electrophotosensitive Material

Examples 2-31 to 2-35

[0360] Electrophotosensitive materials of Examples 2-31 to 2-35 were fabricated the same way as in Example 1-35, except that each of the examples used 0.2 parts by weight of dinaphthoquinone compound of the formula of a number listed in Table 10. Examples 2-36 to 2-40 Electrophotosensitive materials of Examples 2-36 to 2-40 were fabricated the same way as in Example 1-41, except that each of the examples used 40 parts by weight of dinaphthoquinone compound of the formula of a number listed in Table 10.

[0361] The electrophotosensitive materials of the above examples were subjected to the same sensitivity test (II), durability test (II) and solvent resistance test as the above and evaluated for the characteristics thereof. The results as well as those of Comparative Examples 1-10, 1-11 are listed in Table 10.

	TABLE 10
	Initial	After durability test
						HLE			HLE
		P-H		SP	RP	E½	SP	RP	E½
	SPL	TM	DNQ	V0(V)	Vr(V)	(μJ/cm2)	V0(V)	Vr(V)	(μJ/cm2)	SRT
Ex. 2-31	a-SiC	HT-1	1-2-3	−804	−157	0.902	−806	−152	0.873	◯
Ex. 2-32	a-SiC	HT-1	1-2-4	−809	−150	0.894	−812	−151	0.891	◯
Ex. 2-33	a-SiC	HT-1	1-2-5	−804	−155	0.878	−805	−152	0.861	◯
Ex. 2-34	a-SiC	HT-1	1-2-6	−817	−149	0.885	−813	−146	0.867	◯
Ex. 2-35	a-SiC	HT-1	1-2-8	−804	−157	0.911	−812	−158	0.908	◯
C. Ex. 1-10	a-SiC	HT-1	—	−806	−165	0.938	−782	−192	1.052	X
Ex. 2-36	a-SiC	HT-3	1-2-3	−809	−134	0.985	−809	−132	0.970	◯
Ex. 2-37	a-SiC	HT-3	1-2-4	−812	−130	0.976	−802	−138	1.036	◯
Ex. 2-38	a-SiC	HT-3	1-2-5	−802	−138	0.948	−809	−128	0.931	◯
Ex. 2-39	a-SiC	HT-3	1-2-6	−811	−132	0.967	−799	−129	0.945	◯
Ex. 2-40	a-SiC	HT-3	1-2-8	−801	−138	0.995	−809	−136	0.981	◯
C. Ex. 1-11	a-SiC	HT-3	—	−814	−147	1.024	−776	−176	1.226	X

[0362] It was confirmed from the table that if the single-layer photosensitive layer was replaced by the multi-layer photosensitive layer, the same results as the above were obtained according to the compositions of the charge transport layer defining the outermost part thereof.

[0363] According to the results of the solvent resistance test listed in the table, all the electrophotosensitive materials of Examples 2-31 to 2-40 suffered no cracks nordelamination of the surface protective layer. It was thus concluded that the use of the dinaphthoquinone compound of the formula (1-2) contributed the improvement of the physical stability of the inorganic surface protective layer.

[0364] It was also confirmed that all the electrophotosensitive materials of these examples were free from serious decrease in photosensitivity when formed with the surface protective layer and thus maintained high photosensitivity, because they had small residual potentials after light exposure and half-life exposures.

[0365] In addition, all the electrophotosensitive materials of these examples were free from significant increase in residual potential and half-life exposure after the durability test. Based on this fact and the results of the solvent resistance test, it was concluded that these electrophotosensitive materials achieved greater improvement in durability than the prior-art products.

Examples 2-41 to 2-50

[0366] Electrophotosensitive materials of these examples were fabricated the same way as in Examples 2-31 to 2-40, except that the same procedure as in Examples 1-13 to 1-24 was taken to form a surface protective layer of amorphous carbon (C) having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over a surface of the multi-layer photosensitive layer.

[0367] The electrophotosensitive materials of these examples were subjected to the same photosensitivity test (II), durability test (II) and solvent resistance test as the above and were evaluated for the characteristics thereof. The results as well as those of Comparative Examples 1-12, 1-13, are listed in Table 11.

	TABLE 11
	Initial	After durability test
						HLE			HLE
		P-H		SP	RP	E1/2	SP	RP	E1/2
	SPL	TM	DNQ	V0(V)	Vr(V)	(μJ/cm2)	V0(V)	Vr(V)	(μJ/cm2)	SRT
Ex. 2-41	a-C	HT-1	1-2-3	−824	−166	1.169	−817	−163	1.148	∘
Ex. 2-42	a-C	HT-1	1-2-4	−790	−157	1.159	−790	−162	1.186	∘
Ex. 2-43	a-C	HT-1	1-2-5	−798	−161	1.136	−795	−165	1.154	∘
Ex. 2-44	a-C	HT-1	1-2-6	−796	−160	1.148	−799	−162	1.162	∘
Ex. 2-45	a-C	HT-1	1-2-8	−802	−162	1.181	−795	−164	1.196	∘
C. Ex. 1-12	a-C	HT-1	—	−785	−172	1.216	−748	−198	1.400	x
Ex. 2-46	a-C	HT-3	1-2-3	−807	−136	1.056	−792	−133	1.043	∘
Ex. 2-47	a-C	HT-3	1-2-4	−817	−132	1.046	−805	−130	1.030	∘
Ex. 2-48	a-C	HT-3	1-2-5	−782	−132	1.027	−795	−137	1.066	∘
Ex. 2-49	a-C	HT-3	1-2-6	−785	−138	1.032	−793	−131	0.993	∘
Ex. 2-50	a-C	HT-3	1-2-8	−806	−132	1.067	−804	−132	1.061	∘
C. Ex. 1-13	a-C	HT-3	—	−817	−146	1.098	−771	−178	1.339	x

[0368] It was confirmed from the table that if the type of the surface protective layer was changed, the same results as the above were obtained according to the compositions of the charge transport layer of the multi-layer photosensitive layer as the base.

[0369] According to the results of the solvent resistance test listed in the table, all the electrophotosensitive materials of Examples 2-41 to 2-50 suffered no cracks nor delamination of the surface protective layer. It was thus concluded that the use of the dinaphthoquinone compound of the formula (1-2) contributed the improvement of the physical stability of the inorganic surface protective layer.

[0370] It was also confirmed that all the electrophotosensitive materials of these examples were free from serious decrease in photosensitivity when formed with the surface protective layer and thus maintained high photosensitivity, because they had small residual potentials after light exposure and half-life exposures.

[0371] In addition, all the electrophotosensitive materials of these examples were free from significant increase in residual potential and half-life exposure after the durability test. Based on this fact and the results of the solvent resistance test, it was concluded that these electrophotosensitive materials achieved greater improvement in durability than the prior-art products.

Examples 2-51 to 2-52

[0372] Electrophotosensitive materials of these examples were fabricated the same way as in Examples 2-37, 2-38 except that the same procedure as in Examples 1-25, 1-26 was taken to form a surface protective layer of amorphous silicon-nitrogen (SiN) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the multi-layer photosensitive layer.

Examples 2-53, 2-54

[0373] Electrophotosensitive materials of these examples were fabricated the same way as in Examples 2-37, 2-38 except that the same procedure as in Examples 1-27, 1-28 was taken to form a surface protective layer of amorphous carbon-nitrogen (CN) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the multi-layer photosensitive layer.

Examples 2-55, 2-56

[0374] Electrophotosensitive materials of these examples were fabricated the same way as in Examples 2-37, 2-38 except that the same procedure as in Examples 1-29, 1-30 was taken to form a surface protective layer of amorphous carbon-boron (CB) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the multi-layer photosensitive layer.

Examples 2-57, 2-58

[0375] Electrophotosensitive materials of these examples were fabricated the same way as in Examples 2-37, 2-38 except that the same procedure as in Examples 1-31, 1-32 was taken to form a surface protective layer of amorphous carbon-fluorine (CF) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the multi-layer photosensitive layer.

Examples 2-59, 2-60

[0376] Electrophotosensitive materials of these examples were fabricated the same way as in Examples 2-37, 2-38 except that the same procedure as in Examples 1-33, 1-34 was taken to form a surface protective layer of amorphous boron-nitrogen (BN) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the multi-layer photosensitive layer.

[0377] The electrophotosensitive materials of the above examples were subjected to the same photosensitivity test (II), durability test (II) and solvent resistance test as the above and were evaluated for the characteristics thereof. The results as well as those of Comparative Examples 1-14 to 1-18 are listed in Table 12.

	TABLE 12
	Initial	After durability test
						HLE			HLE
		P-H		SP	RP	E1/2	SP	RP	E1/2
	SPL	TM	DNQ	V0(V)	Vr(V)	(μJ/cm2)	V0(V)	Vr(V)	(μJ/cm2)	SRT
Ex. 2-51	a-SiN	HT-3	1-2-4	−812	−133	1.064	−803	−131	1.048	∘
Ex. 2-52	a-SiN	HT-3	1-2-5	−804	−134	1.064	−796	−124	0.993	∘
C. Ex. 1-14	a-SiN	HT-3	—	−785	−139	1.096	−758	−186	1.367	Δ
Ex. 2-53	a-CN	HT-3	1-2-4	−806	−136	1.133	−803	−135	1.131	∘
Ex. 2-54	a-CN	HT-3	1-2-5	−790	−157	0.902	−796	−152	0.873	∘
C. Ex. 1-15	a-CN	HT-3	—	−793	−146	1.156	−762	−177	1.381	x
Ex. 2-55	a-CB	HT-3	1-2-4	−793	−129	0.951	−791	−122	0.936	∘
Ex. 2-56	a-CB	HT-3	1-2-5	−814	−124	0.951	−808	−122	0.936	∘
C. Ex. 1-16	a-CB	HT-3	—	−793	−137	0.979	−746	−167	1.193	x
Ex. 2-57	a-CF	HT-3	1-2-4	−788	−132	0.982	−792	−134	0.997	∘
Ex. 2-58	a-CF	HT-3	1-2-5	−796	−135	0.992	−801	−130	0.965	∘
C. Ex. 1-17	a-CF	HT-3	—	−793	−139	1.021	−766	−178	1.307	x
Ex. 2-59	a-BN	HT-3	1-2-4	−793	−103	0.870	−788	−101	0.954	∘
Ex. 2-60	a-BN	HT-3	1-2-5	−814	−107	0.861	−812	−103	0.841	∘
C. Ex. 1-18	a-BN	HT-3	—	−780	−117	0.904	−748	−146	1.128	x

[0378] It was confirmed from the table that if the type of the surface protective layer was further changed, the same results as the above were obtained according to the compositions of the charge transport layer of the multi-layer photosensitive layer as the base.

[0379] According to the results of the solvent resistance test listed in the table, all the electrophotosensitive materials of Examples 2-51 to 2-60 suffered no cracks nor delamination of the surface protective layer. It was thus concluded that the use of the dinaphthoquinone compound of the formula (1-2) contributed the improvement of the physical stability of the inorganic surface protective layer.

[0380] It was also confirmed that all the electrophotosensitive materials of these examples were free from serious decrease in photosensitivity when formed with the surface protective layer and thus maintained high photosensitivity, because they had small residual potentials after light exposure and half-life exposures.

[0381] In addition, all the electrophotosensitive materials of these examples were free from significant increase in residual potential and half-life exposure after the durability test. Based on this fact and the results of the solvent resistance test, it was concluded that these electrophotosensitive materials achieved greater improvement in durability than the prior-art products.

[0382] Single-layer Electrophotosensitive Material

Examples 3-1 to 3-7

[0383] Electrophotosensitive materials of Examples 3-1 to 3-7 were fabricated the same way as in Example 1-1, except that each of the examples used 40 parts by weight of naphthoquinone compound of the formula of a number listed in Table 13.

Examples 3-8 to 3-14

[0384] Electrophotosensitive materials of Examples 3-8 to 3-14 were fabricated the same way as in Example 1-7, except that each of the examples used 40 parts by weight of naphthoquinone compound of the formula of a number listed in Table 13.

[0385] The electrophotosensitive materials of the above examples were subjected to the same photosensitivity test (I), durability test (I) and solvent resistance test as the above and were evaluated for the characteristics thereof. The results as well as those of Comparative Examples 1-1, 1-2 are listed in Table 13.

	TABLE 13
	Initial	After durability test
						HLE			HLE
		P-H		SP	RP	E1/2	SP	RP	E1/2
	SPL	TM	NQC	V0(V)	Vr(V)	(μJ/cm2)	V0(V)	Vr(V)	(μJ/cm2)	SRT
Ex. 3-1	a-SiC	HT-1	2-1-5	809	196	1.390	795	201	1.455	∘
Ex. 3-2	a-SiC	HT-1	2-2-4	793	178	1.304	801	185	1.355	∘
Ex. 3-3	a-SiC	HT-1	2-2-9	802	183	1.271	798	181	1.257	∘
Ex. 3-4	a-SiC	HT-1	2-3-1	785	162	1.155	795	165	1.176	∘
Ex. 3-5	a-SiC	HT-1	2-3-3	796	163	1.181	788	161	1.167	∘
Ex. 3-6	a-SiC	HT-1	2-3-8	796	175	1.226	788	168	1.198	∘
Ex. 3-7	a-SiC	HT-1	2-3-11	806	170	1.251	795	168	1.236	∘
C. Ex. 1-1	a-SiC	HT-1	—	817	205	1.500	745	244	1.785	x
Ex. 3-8	a-SiC	HT-3	2-1-5	814	219	1.544	809	226	1.593	∘
Ex. 3-9	a-SiC	HT-3	2-2-4	793	206	1.450	802	204	1.436	∘
Ex. 3-10	a-SiC	HT-3	2-2-9	812	204	1.414	795	199	1.383	∘
Ex. 3-11	a-SiC	HT-3	2-3-1	814	188	1.282	815	182	1.261	∘
Ex. 3-12	a-SiC	HT-3	2-3-3	788	187	1.313	804	190	1.334	∘
Ex. 3-13	a-SiC	HT-3	2-3-8	798	192	1.367	780	195	1.388	∘
Ex. 3-14	a-SiC	HT-3	2-3-11	812	198	1.390	796	195	1.369	∘
C. Ex. 1-2	a-SiC	HT-3	—	804	232	1.667	748	252	1.810	Δ
NQC: Naphtoquinone compound

[0386] According to the results of the solvent resistance test listed in the table, all the electrophotosensitive materials of Examples 3-1 to 3-14 suffered no cracks nor delamination of the surface protective layer. It was thus concluded that the use of the naphthoquinone compounds of the formulas (2-1) to (2-3) contributed the improvement of the physical stability of the inorganic surface protective layer.

[0387] It was also confirmed that all the electrophotosensitive materials of these examples were free from serious decrease in photosensitivity when formed with the surface protective layer and thus maintained high photosensitivity, because they had small residual potentials after light exposure and half-life exposures.

[0388] In addition, all the electrophotosensitive materials of these examples were free from significant increase in residual potential and half-life exposure after the durability test. Based on this fact and the results of the solvent resistance test, it was concluded that these electrophotosensitive materials achieved greater improvement in durability than the prior-art products.

Examples 3-15 to 3-28

[0389] Electrophotosensitive materials of Examples 3-15 to 3-28 were fabricated the same way as in Examples 3-1 to 3-14 except that the same procedure as in Examples 1-13 to 1-24 was taken to form a surface protective layer of amorphous carbon (C) having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the single-layer photosensitive layer.

[0390] The electrophotosensitive materials of the above examples were subjected to the same photosensitivity test (I), durability test (I) and solvent resistance test as the above and were evaluated for the characteristics thereof. The results as well as those of Comparative Examples 1-3, 1-4 are listed in Table 14.

	TABLE 14
	Initial	After durability test
						HLE			HLE
		P-H		SP	RP	E1/2	SP	RP	E1/2
	SPL	TM	NQC	V0(V)	Vr(V)	(μJ/cm2)	V0(V)	Vr(V)	(μJ/cm2)	SRT
Ex. 3-15	a-C	HT-1	2-1-5	794	192	1.448	786	210	1.584	∘
Ex. 3-16	a-C	HT-1	2-2-4	795	185	1.360	796	180	1.343	∘
Ex. 3-17	a-C	HT-1	2-2-9	808	181	1.325	817	183	1.340	∘
Ex. 3-18	a-C	HT-1	2-3-1	812	162	1.203	804	160	1.188	∘
Ex. 3-19	a-C	HT-1	2-3-3	804	173	1.231	798	166	1.211	∘
Ex. 3-20	a-C	HT-1	2-3-8	788	172	1.282	785	175	1.304	∘
Ex. 3-21	a-C	HT-1	2-3-11	796	178	1.303	804	179	1.310	∘
C. Ex. 1-3	a-C	HT-1	—	793	208	1.563	742	238	1.788	x
Ex. 3-22	a-C	HT-3	2-1-5	817	213	1.544	804	221	1.631	∘
Ex. 3-23	a-C	HT-3	2-2-4	803	193	1.450	809	190	1.427	∘
Ex. 3-24	a-C	HT-3	2-2-9	796	188	1.413	806	190	1.428	∘
Ex. 3-25	a-C	HT-3	2-3-1	785	170	1.283	780	168	1.268	∘
Ex. 3-26	a-C	HT-3	2-3-3	809	177	1.313	806	179	1.328	∘
Ex. 3-27	a-C	HT-3	2-3-8	804	184	1.367	793	181	1.345	∘
Ex. 3-28	a-C	HT-3	2-3-11	806	185	1.389	796	190	1.427	∘
C. Ex. 1-4	a-C	HT-3	—	788	222	1.667	746	240	1.792	x

[0391] It was confirmed from the table that if the type of the surface protective layer was changed, the same results as the above were obtained according to the compositions of the single-layer photosensitive layer as the base.

[0392] According to the results of the solvent resistance test listed in the table, all the electrophotosensitive materials of Examples 3-15 to 3-28 suffered no cracks nor delamination of the surface protective layer. It was thus concluded that the use of the naphthoquinone compounds of the formulas (2-1) to (2-3) contributed the improvement of the physical stability of the inorganic surface protective layer.

[0393] It was also confirmed that all the electrophotosensitive materials of these examples were free from serious decrease in photosensitivity when formed with the surface protective layer and thus maintained high photosensitivity, because they had small residual potentials after light exposure and half-life exposures.

[0394] In addition, all the electrophotosensitive materials of these examples were free from significant increase in residual potential and half-life exposure after the durability test. Based on this fact and the results of the solvent resistance test, it was concluded that these electrophotosensitive materials achieved greater improvement in durability than the prior-art products.

Examples 3-29 to 3-32

[0395] Electrophotosensitive materials of Examples 3-29 to 3-32 were fabricated the same way as in Examples 3-8, 3-10, 3-12 and 3-13 except that the same procedure as in Examples 1-25, 1-26 was taken to form a surface protective layer of amorphous silicon-nitrogen (SiN) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the single-layer photosensitive layer.

Examples 3-33 to 3-36

[0396] Electrophotosensitive materials of Examples 3-33 to 3-36 were fabricated the same way as in Examples 3-8, 3-10, 3-12 and 3-13 except that the same procedure as in Examples 1-27, 1-28 was taken to form a surface protective layer of amorphous carbon-nitrogen (CN) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the single-layer photosensitive layer.

Examples 3-37 to 3-40

[0397] Electrophotosensitive materials of Examples 3-37 to 3-40 were fabricated the same way as in Examples 3-8, 3-10, 3-12 and 3-13 except that the same procedure as in Examples 1-29, 1-30 was taken to form a surface protective layer of amorphous carbon-boron (CB) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the single-layer photosensitive layer.

Examples 3-41 to 3-44

[0398] Electrophotosensitive materials of Examples 3-41 to 3-44 were fabricated the same way as in Examples 3-8, 3-10, 3-12 and 3-13 except that the same procedure as in Examples 1-31, 1-32 was taken to form a surface protective layer of amorphous carbon-fluorine (CF) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the single-layer photosensitive layer.

Examples 3-45 to 3-48

[0399] Electrophotosensitive materials of Examples 3-45 to 3-48 were fabricated the same way as in Examples 3-8, 3-10, 3-12 and 3-13 except that the same procedure as in Examples 1-33, 1-34 was taken to form a surface protective layer of amorphous boron-nitrogen (BN) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the single-layer photosensitive layer.

[0400] The electrophotosensitive materials of the above examples were subjected to the same photosensitivity test (I), durability test (I) and solvent resistance test as the above and were evaluated for the characteristics thereof. The results as well as those of Comparative Examples 1-5 to 1-9 are listed in Tables 15a and 15b.

	TABLE 15
	Initial	After durability test
						HLE			HLE
		P-H		SP	RP	E1/2	SP	RP	E1/2
	SPL	TM	NQC	V0(V)	Vr(V)	(μJ/cm2)	V0(V)	Vr(V)	(μJ/cm2)	SRT
Ex. 3-29	a-SiN	HT-3	2-1-5	814	231	1.655	804	238	1.705	∘
Ex. 3-30	a-SiN	HT-3	2-2-9	780	212	1.515	793	217	1.531	∘
Ex. 3-31	a-SiN	HT-3	2-3-3	785	202	1.408	809	202	1.411	∘
Ex. 3-32	a-SiN	HT-3	2-3-8	812	203	1.465	801	206	1.478	∘
C. Ex. 1-5	a-SiN	HT-3	—	812	245	1.787	749	263	1.918	Δ
Ex. 3-33	a-CN	HT-3	2-1-5	798	240	1.737	802	248	1.795	∘
Ex. 3-34	a-CN	HT-3	2-2-9	793	203	1.443	796	201	1.432	∘
Ex. 3-35	a-CN	HT-3	2-3-3	812	191	1.389	798	194	1.411	∘
Ex. 3-36	a-CN	HT-3	2-3-8	814	196	1.443	806	200	1.465	∘
C. Ex. 1-6	a-CN	HT-3	—	790	252	1.875	752	270	2.009	Δ
Ex. 3-37	a-CB	HT-3	2-1-5	806	205	1.544	794	215	1.619	∘
Ex. 3-38	a-CB	HT-3	2-2-9	817	170	1.283	806	177	1.343	∘
Ex. 3-39	a-CB	HT-3	2-3-3	793	174	1.235	782	171	1.215	∘
Ex. 3-40	a-CB	HT-3	2-3-8	796	173	1.283	801	178	1.320	∘
C. Ex. 1-7	a-CB	HT-3	—	801	222	1.667	746	238	1.787	x
Ex. 3-41	a-CF	HT-3	2-1-5	809	222	1.616	817	228	1.660	∘
Ex. 3-42	a-CF	HT-3	2-2-9	801	192	1.353	809	197	1.388	∘
Ex. 3-43	a-CF	HT-3	2-3-3	806	182	1.284	809	186	1.296	∘
Ex. 3-44	a-CF	HT-3	2-3-8	788	197	1.354	785	192	1.338	∘
C. Ex. 1-8	a-CF	HT-3	—	788	232	1.745	734	248	1.865	x
Ex. 3-45	a-BN	HT-3	2-1-5	801	192	1.478	804	206	1.586	∘
Ex. 3-46	a-BN	HT-3	2-2-9	810	152	1.200	812	160	1.263	∘
Ex. 3-47	a-BN	HT-3	2-3-3	812	155	1.165	814	155	1.165	∘
Ex. 3-48	a-BN	HT-3	2-3-8	808	157	1.200	812	152	1.162	∘
C. Ex. 1-9	a-BN	HT-3	—	785	203	1.595	752	233	1.831	x

[0401] It was confirmed from the tables that if the type of the surface protective layer was further changed, the same results as the above were obtained according to the compositions of the single-layer photosensitive layer as the base.

[0402] According to the results of the solvent resistance test listed in the tables, all the electrophotosensitive materials of Examples 3-29 to 3-48 suffered no cracks nor delamination of the surface protective layer. It was thus concluded that the use of the naphthoquinone compounds of the formulas (2-1) to (2-3) contributed the improvement of the physical stability of the inorganic surface protective layer.

[0403] It was also confirmed that all the electrophotosensitive materials of these examples were free from serious decrease in photosensitivity when formed with the surface protective layer and thus maintained high photosensitivity, because they had small residual potentials after light exposure and half-life exposures.

[0404] In addition, all the electrophotosensitive materials of these examples were free from significant increase in residual potential and half-life exposure after the durability test. Based on this fact and the results of the solvent resistance test, it was concluded that these electrophotosensitive materials achieved greater improvement in durability than the prior-art products.

[0405] Multi-layer Electrophotosensitive Material

Examples 3-49 to 3-55

[0406] Electrophotosensitive materials of Examples 3-49 to 3-55 were fabricated the same way as in Example 1-35, except that each of the examples used 0.2 parts by weight of naphthoquinone compound of the formula of a number listed in Table 16.

Examples 3-56 to 3-62

[0407] Electrophotosensitive materials of Examples 3-56 to 3-62 were fabricated the same way as in Example 1-41, except that each of the examples used 40 parts by weight of naphthoquinone compound of the formula of a number listed in Table 16.

[0408] The electrophotosensitive materials of the above examples were subjected to the same photosensitivity test (II), durability test (II) and solvent resistance test as the above and were evaluated for the characteristics thereof. The results as well as the those of Comparative Examples 1-10, 1-11 are listed in Table 16.

	TABLE 16
	Initial	After durability test
						HLE			HLE
		P-H		SP	RP	E1/2	SP	RP	E1/2
	SPL	TM	NQC	V0(V)	Vr(V)	(μJ/cm2)	V0(V)	Vr(V)	(μJ/cm2)	SRT
Ex. 3-49	a-SiC	HT-1	2-1-5	−812	−160	0.920	−817	−164	0.943	∘
Ex. 3-50	a-SiC	HT-1	2-2-4	−801	−153	0.912	−798	−151	0.900	∘
Ex. 3-51	a-SiC	HT-1	2-2-9	−792	−158	0.911	−787	−161	0.928	∘
Ex. 3-52	a-SiC	HT-1	2-3-1	−806	−145	0.877	−798	−148	0.895	∘
Ex. 3-53	a-SiC	HT-1	2-3-3	−809	−150	0.893	−802	−154	0.917	∘
Ex. 3-54	a-SiC	HT-1	2-3-8	−796	−157	0.902	−801	−158	0.908	∘
Ex. 3-55	a-SiC	HT-1	2-3-11	−812	−153	0.911	−803	−156	0.929	∘
C. Ex. 1-10	a-SiC	HT-1	—	−806	−165	0.938	−782	−192	1.052	x
Ex. 3-56	a-SiC	HT-3	2-1-5	−812	−140	0.994	−793	−152	1.079	∘
Ex. 3-57	a-SiC	HT-3	2-2-4	−812	−133	0.995	−817	−138	0.991	∘
Ex. 3-58	a-SiC	HT-3	2-2-9	−809	−136	0.994	−802	−133	0.983	∘
Ex. 3-59	a-SiC	HT-3	2-3-1	−802	−133	0.957	−806	−135	0.971	∘
Ex. 3-60	a-SiC	HT-3	2-3-3	−798	−130	0.976	−792	−135	0.981	∘
Ex. 3-61	a-SiC	HT-3	2-3-8	−790	−137	0.986	−804	−134	0.985	∘
Ex. 3-62	a-SiC	HT-3	2-3-11	−795	−138	0.994	−804	−136	0.980	∘
C. Ex. 1-11	a-SiC	HT-3	—	−814	−147	1.024	−776	−176	1.226	x

[0409] It was confirmed from the table that if the single-layer photosensitive layer was replaced by the multi-layer photosensitive layer, the same results as the above were obtained according to the compositions of the charge transport layer defining the outermost part thereof.

[0410] According to the results of the solvent resistance test listed in the table, all the electrophotosensitive materials of Examples 3-49 to 3-62 suffered no cracks nor delamination of the surface protective layer. It was thus concluded that the use of the naphthoquinone compounds of the formulas (2-1) to (2-3) contributed the improvement of the physical stability of the inorganic surface protective layer.

[0411] It was also confirmed that all the electrophotosensitive materials of these examples were free from serious decrease in photosensitivity when formed with the surface protective layer and thus maintained high photosensitivity, because they had small residual potentials after light exposure and half-life exposures.

[0412] In addition, all the electrophotosensitive materials of these examples were free from significant increase in residual potential and half-life exposure after the durability test. Based on this fact and the results of the solvent resistance test, it was concluded that these electrophotosensitive materials achieved greater improvement in durability than the prior-art products.

Examples 3-63 to 3-76

[0413] Electrophotosensitive materials of these examples were fabricated the same way as in Examples 3-49 to 3-62 except that the same procedure as in Examples 1-13 to 1-24 was taken to form a surface protective layer of amorphous carbon (C) having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the multi-layer photosensitive layer.

[0414] The electrophotosensitive materials of the above examples were subjected to the same photosensitivity test (II), durability test (II) and solvent resistance test as the above and were evaluated for the characteristics thereof. The results as well as those of Comparative Examples 1-12, 1-13 are listed in Table 17.

	TABLE 17
	Initial	After durability test
						HLE			HLE
		P-H		SP	RP	E1/2	SP	RP	E1/2
	SPL	TM	NQC	V0(V)	Vr(V)	(μJ/cm2)	V0(V)	Vr(V)	(μJ/cm2)	SRT
Ex. 3-63	a-C	HT-1	2-1-5	−794	−165	1.181	−782	−173	1.238	∘
Ex. 3-64	a-C	HT-1	2-2-4	−785	−165	1.181	−791	−157	1.144	∘
Ex. 3-65	a-C	HT-1	2-2-9	−782	−167	1.182	−780	−165	1.168	∘
Ex. 3-66	a-C	HT-1	2-3-1	−806	−159	1.137	−798	−151	1.115	∘
Ex. 3-67	a-C	HT-1	2-3-3	−814	−162	1.158	−802	−164	1.172	∘
Ex. 3-68	a-C	HT-1	2-3-8	−804	−166	1.170	−812	−158	1.144	∘
Ex. 3-69	a-C	HT-1	2-3-11	−798	−167	1.181	−787	−159	1.154	∘
C. Ex. 1-12	a-C	HT-1	—	−785	−172	1.216	−748	−198	1.400	x
Ex. 3-70	a-C	HT-3	2-1-5	−801	−137	1.067	−782	−147	1.145	∘
Ex. 3-71	a-C	HT-3	2-2-4	−806	−137	1.067	−801	−135	1.051	∘
Ex. 3-72	a-C	HT-3	2-2-9	−817	−132	1.066	−814	−137	1.106	∘
Ex. 3-73	a-C	HT-3	2-3-1	−814	−132	1.026	−817	−127	0.997	∘
Ex. 3-74	a-C	HT-3	2-3-3	−817	−135	1.046	−810	−137	1.061	∘
Ex. 3-75	a-C	HT-3	2-3-8	−804	−141	1.056	−795	−136	1.039	∘
Ex. 3-76	a-C	HT-3	2-3-11	−798	−132	1.067	−804	−138	1.088	∘
C. Ex. 1-13	a-C	HT-3	—	−817	−146	1.098	−771	−178	1.339	x

[0415] It was confirmed from the table that if the type of the surface protective layer was changed, the same results as the above were obtained according to the compositions of the charge transport layer of the multi-layer photosensitive layer as the base.

[0416] According to the results of the solvent resistance test listed in the table, all the electrophotosensitive materials of Examples 3-63 to 3-76 suffered no cracks nor delamination of the surface protective layer. It was thus concluded that the use of the naphthoquinone compounds of the formulas (2-1) to (2-3) contributed the improvement of the physical stability of the inorganic surface protective layer.

[0417] It was also confirmed that all the electrophotosensitive materials of these examples were free from serious decrease in photosensitivity when formed with the surface protective layer and thus maintained high photosensitivity, because they had small residual potentials after light exposure and half-life exposures.

[0418] In addition, all the electrophotosensitive materials of these examples were free from significant increase in residual potential and half-life exposure after the durability test. Based on this fact and the results of the solvent resistance test, it was concluded that these electrophotosensitive materials achieved greater improvement in durability than the prior-art products.

Examples 3-77 to 3-80

[0419] Electrophotosensitive materials of these examples were fabricated the same way as in Examples 3-56, 3-58, 3-60 and 3-61 except that the same procedure as in Examples 1-25, 1-26 was taken to form a surface protective layer of amorphous silicon-nitrogen (SiN) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the multi-layer photosensitive layer.

Examples 3-81 to 3-84

[0420] Electrophotosensitive materials of these examples were fabricated the same way as in Examples 3-56, 3-58, 3-60 and 3-61 except that the same procedure as in Examples 1-27, 1-28 was taken to form a surface protective layer of amorphous carbon-nitrogen (CN) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the multi-layer photosensitive layer.

Examples 3-85 to 3-88

[0421] Electrophotosensitive materials of these examples were fabricated the same way as in Examples 3-56, 3-58, 3-60 and 3-61 except that the same procedure as in Examples 1-29, 1-30 was taken to form a surface protective layer of amorphous carbon-boron (CB) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the multi-layer photosensitive layer.

Examples 3-89 to 3-92

[0422] Electrophotosensitive materials of these examples were fabricated the same way as in Examples 3-56, 3-58, 3-60 and 3-61 except that the same procedure as in Examples 1-31, 1-32 was taken to form a surface protective layer of amorphous carbon-fluorine (CF) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the multi-layer photosensitive layer.

[0423] Examples 3-93 to 3-96

[0424] Electrophotosensitive materials of these examples were fabricated the same way as in Examples 3-56, 3-58, 3-60 and 3-61 except that the same procedure as in Examples 1-33, 1-34 was taken to form a surface protective layer of amorphous boron-nitrogen (BN) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the multi-layer photosensitive layer.

[0425] The electrophotosensitive materials of the above examples were subjected to the same photosensitivity test (II), durability test (II) and solvent resistance test as the above and were evaluated for the characteristics thereof. The results as well as those of Comparative Examples 1-14 to 1-18 are listed in Tables 18a, 18b.

	TABLE 18
	Initial	After durability test
						HLE			HLE
		P-H		SP	RP	E1/2	SP	RP	E1/2
	SPL	TM	NQC	V0(V)	Vr(V)	(μJ/cm2)	V0(V)	Vr(V)	(μJ/cm2)	SRT
Ex. 3-77	a-SiN	HT-3	2-1-5	−812	−133	1.086	−806	−148	1.208	∘
Ex. 3-78	a-SiN	HT-3	2-2-9	−788	−124	1.054	−792	−128	1.078	∘
Ex. 3-79	a-SiN	HT-3	2-3-3	−798	−128	1.064	−814	−133	1.089	∘
Ex. 3-80	a-SiN	HT-3	2-3-8	−783	−134	1.054	−796	−132	1.038	∘
C. Ex. 1-14	a-SiN	HT-3	—	−785	−139	1.095	−758	−186	1.367	Δ
Ex. 3-81	a-CN	HT-3	2-1-5	−790	−138	1.146	−796	−154	1.279	∘
Ex. 3-82	a-CN	HT-3	2-2-9	−801	−155	0.903	−809	−157	0.913	∘
Ex. 3-83	a-CN	HT-3	2-3-3	−798	−136	1.134	−814	−141	1.156	∘
Ex. 3-84	a-CN	HT-3	2-3-8	−809	−154	0.902	−796	−149	0.896	∘
C. Ex. 1-15	a-CN	HT-3	—	−793	−146	1.156	−762	−177	1.381	x
Ex. 3-85	a-CB	HT-3	2-1-5	−788	−133	0.969	−783	−147	1.071	∘
Ex. 3-86	a-CB	HT-3	2-2-9	−790	−129	0.951	−802	−124	0.924	∘
Ex. 3-87	a-CB	HT-3	2-3-3	−817	−131	0.951	−814	−126	0.935	∘
Ex. 3-88	a-CB	HT-3	2-3-8	−788	−126	0.951	−780	−122	0.924	∘
C. Ex. 1-16	a-CB	HT-3	—	−793	−137	0.979	−746	−167	1.193	x
Ex. 3-89	a-CF	HT-3	2-1-5	−809	−135	1.011	−783	−148	1.108	∘
Ex. 3-90	a-CF	HT-3	2-2-9	−804	−135	0.992	−798	−125	0.979	∘
Ex. 3-91	a-CF	HT-3	2-3-3	−801	−134	0.982	−796	−132	0.967	∘
Ex. 3-92	a-CF	HT-3	2-3-8	−802	−130	0.992	−793	−128	0.977	∘
C. Ex. 1-17	a-CF	HT-3	—	−793	−139	1.021	−766	−178	1.307	x
Ex. 3-93	a-BN	HT-3	2-1-5	−804	−106	0.895	−790	−114	0.963	∘
Ex. 3-94	a-BN	HT-3	2-2-9	−793	−102	0.862	−806	−104	0.879	∘
Ex. 3-95	a-BN	HT-3	2-3-3	−812	−110	0.870	−806	−108	0.854	∘
Ex. 3-96	a-BN	HT-3	2-3-8	−817	−112	0.861	−813	−109	0.838	∘
C. Ex. 1-18	a-BN	HT-3	—	−780	−117	0.904	−748	−146	1.128	x

[0426] It was confirmed from the tables that if the type of the surface protective layer was further changed, the same results as the above were obtained according to the compositions of the charge transport layer of the multi-layer photosensitive layer as the base.

[0427] According to the results of the solvent resistance test listed in the table, all the electrophotosensitive materials of Examples 3-77 to 3-96 suffered no cracks nor delamination of the surface protective layer. It was thus concluded that the use of the naphthoquinone compounds of the formulas (2-1) to (2-3) contributed the improvement of the physical stability of the inorganic surface protective layer.

[0428] It was also confirmed that all the electrophotosensitive materials of these examples were free from serious decrease in photosensitivity when formed with the surface protective layer and thus maintained high photosensitivity, because they had small residual potentials after light exposure and half-life exposures.

[0429] In addition, all the electrophotosensitive materials of these examples were free from significant increase in residual potential and half-life exposure after the durability test. Based on this fact and the results of the solvent resistance test, it was concluded that these electrophotosensitive materials achieved greater improvement in durability than the prior-art products.

[0430] Single-layer Electrophotosensitive Material

Examples 4-1 to 4-4

[0431] Electrophotosensitive materials of Examples 4-1 to 4-4 were fabricated the same way as in Example 1-1 except that each of the examples used 40 parts by weight of diindenopyrazine compound of the formula of a number listed in Table 19.

Examples 4-5 to 4-8

[0432] Electrophotosensitive materials of Examples 4-5 to 4-8 were fabricated the same way as in Example 1-7 except that each of the examples used 40 parts by weight of diindenopyrazine compound of the formula of a number listed in Table 19.

[0433] The electrophotosensitive materials of the above examples were subjected to the same photosensitivity test (I), durability test (I) and solvent resistance test as the above and were evaluated for the characteristics thereof. The results as well as those of Comparative Examples 1-1, 1-2 are listed in Table 19.

	TABLE 19
	Initial	After durability test
						HLE			HLE
		P-H		SP	RP	E1/2	SP	RP	E1/2
	SPL	TM	DIP	V0(V)	Vr(V)	(μJ/cm2)	V0(V)	Vr(V)	(μJ/cm2)	SRT
Ex. 4-1	a-SiC	HT-1	2-4-1	817	191	1.328	805	186	1.293	∘
Ex. 4-2	a-SiC	HT-1	2-4-3	797	188	1.364	806	186	1.349	∘
Ex. 4-3	a-SiC	HT-1	2-5-2	809	175	1.282	801	173	1.276	∘
Ex. 4-4	a-SiC	HT-1	2-5-3	796	193	1.340	804	188	1.305	∘
C. Ex. 1-1	a-SiC	HT-1	—	817	205	1.500	745	244	1.785	x
Ex. 4-5	a-SiC	HT-3	2-4-1	812	215	1.476	798	212	1.455	∘
Ex. 4-6	a-SiC	HT-3	2-4-3	806	220	1.529	803	216	1.501	∘
Ex. 4-7	a-SiC	HT-3	2-5-2	796	200	1.437	808	202	1.451	∘
Ex. 4-8	a-SiC	HT-3	2-5-3	796	220	1.516	798	218	1.502	∘
C. Ex. 1-2	a-SiC	HT-3	—	804	232	1.667	748	252	1.810	Δ
DIP: Diindenopyradine compound

[0434] According to the results of the solvent resistance test listed in the table, all the electrophotosensitive materials of Examples 4-1 to 4-8 suffered no cracks nor delamination of the surface protective layer. It was thus concluded that the use of the diindenopyrazine compounds of the formulas (2-4), (2-5) contributed the improvement of the physical stability of the inorganic surface protective layer.

[0435] It was also confirmed that all the electrophotosensitive materials of these examples were free from serious decrease in photosensitivity when formed with the surface protective layer and thus maintained high photosensitivity, because they had small residual potentials after light exposure and half-life exposures.

[0436] In addition, all the electrophotosensitive materials of these examples were free from significant increase in residual potential and half-life exposure after the durability test. Based on this fact and the results of the solvent resistance test, it was concluded that these electrophotosensitive materials achieved greater improvement in durability than the prior-art products.

Examples 4-9 to 4-16

[0437] Electrophotosensitive materials of Examples 4-9 to 4-16 were fabricated the same way as in Examples 4-1 to 4-8 except that the same procedure as in Examples 1-13to 1-24 was taken to form a surface protective layer of amorphous carbon (C) having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the single-layer photosensitive layer.

[0438] The electrophotosensitive materials of the above examples were subjected to the same photosensitivity test (I), durability test (I) and solvent resistance test as the above and were evaluated for the characteristics thereof. The results as well as those of Comparative Examples 1-3, 1-4 are listed in Table 20.

	TABLE 20
	Initial	After durability test
						HLE			HLE
		P-H		SP	RP	E1/2	SP	RP	E1/2
	SPL	TM	DIP	V0(V)	Vr(V)	(μJ/cm2)	V0(V)	Vr(V)	(μJ/cm2)	SRT
Ex. 4-9	a-C	HT-1	2-4-1	804	181	1.347	798	186	1.384	∘
Ex. 4-10	a-C	HT-1	2-4-3	780	187	1.409	785	182	1.371	∘
Ex. 4-11	a-C	HT-1	2-5-2	796	176	1.325	792	170	1.280	∘
Ex. 4-12	a-C	HT-1	2-5-3	793	189	1.384	799	190	1.391	∘
C. Ex. 1-3	a-C	HT-1	—	793	208	1.563	742	238	1.788	x
Ex. 4-13	a-C	HT-3	2-4-1	790	205	1.489	804	203	1.474	∘
Ex. 4-14	a-C	HT-3	2-4-3	796	194	1.516	785	191	1.493	∘
Ex. 4-15	a-C	HT-3	2-5-2	809	192	1.463	798	190	1.448	∘
Ex. 4-16	a-C	HT-3	2-5-3	796	198	1.588	801	203	1.628	∘
C. Ex. 1-4	a-C	HT-3	—	788	222	1.667	746	240	1.792	x

[0439] It was confirmed from the table that if the type of the surface protective layer was changed, the same results as the above were obtained according to the compositions of the single-layer photosensitive layer as the base.

[0440] According to the results of the solvent resistance test listed in the table, all the electrophotosensitive materials of Examples 4-9 to 4-16 suffered no cracks nor delamination of the surface protective layer. It was thus concluded that the use of the diindenopyrazine compounds of the formulas (2-4), (2-5) contributed the improvement of the physical stability of the inorganic surface protective layer.

[0441] It was also confirmed that all the electrophotosensitive materials of these examples were free from serious decrease in photosensitivity when formed with the surface protective layer and thus maintained high photosensitivity, because they had small residual potentials after light exposure and half-life exposures.

[0442] In addition, all the electrophotosensitive materials of these examples were free from significant increase in residual potential and half-life exposure after the durability test. Based on this fact and the results of the solvent resistance test, it was concluded that these electrophotosensitive materials achieved greater improvement in durability than the prior-art products.

Examples 4-17, 4-18

[0443] Electrophotosensitive materials of Examples 4-17, 4-18 were fabricated the same way as in Examples 4-5, 4-8 except that the same procedure as in Examples 1-25, 1-26 was taken to form a surface protective layer of amorphous silicon-nitrogen (SiN) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the single-layer photosensitive layer.

Examples 4-19, 4-20

[0444] Electrophotosensitive materials of Examples 4-19, 4-20 were fabricated the same way as in Examples 4-5, 4-8 except that the same procedure as in Examples 1-27, 1-28 was taken to form a surface protective layer of amorphous carbon-nitrogen (CN) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the single-layer photosensitive layer.

Examples 4-21, 4-22

[0445] Electrophotosensitive materials of Examples 4-21, 4-22 were fabricated the same way as in Examples 4-5, 4-8 except that the same procedure as in Examples 1-29, 1-30 was taken to form a surface protective layer of amorphous carbon-boron (CB) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the single-layer photosensitive layer.

Examples 4-23, 4-24

[0446] Electrophotosensitive materials of Examples 4-23, 4-24 were fabricated the same way as in Examples 4-5, 4-8 except that the same procedure as in Examples 1-31, 1-32 was taken to form a surface protective layer of amorphous carbon-fluorine (CF) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the single-layer photosensitive layer.

Examples 4-25, 4-26

[0447] Electrophotosensitive materials of Examples 4-25, 4-26 were fabricated the same way as in Examples 4-5, 4-8 except that the same procedure as in Examples 1-33, 1-34 was taken to form a surface protective layer of amorphous boron-nitrogen (BN) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the single-layer photosensitive layer.

[0448] The electrophotosensitive materials of the above examples were subjected to the same photosensitivity test (I), durabilitytest (I) and solvent resistance test as the above and were evaluated for the characteristics thereof. The results as well as those of Comparative Examples 1-5 to 1-9 are listed in Table 21.

	TABLE 21
	Initial	After durability test
	HLE		HLE
	P-H		SP	RP	E½	SP	RP	E½
	SPL	TM	DIP	V0(V)	Vr(V)	(μJ/cm2)	V0(V)	Vr(V)	(μJ/cm2)	SRT
Ex. 4-17	a-SiN	HT-3	2-4-1	801	223	1.610	809	225	1.624	∘
Ex. 4-18	a-SiN	HT-3	2-5-3	785	216	1.582	788	219	1.604	∘
C. Ex. 1-5	a-SiN	HT-3	—	812	245	1.787	749	263	1.918	Δ
Ex. 4-19	a-CN	HT-3	2-4-1	809	227	1.675	801	225	1.660	∘
Ex. 4-20	a-CN	HT-3	2-5-3	812	226	1.645	803	228	1.660	∘
C. Ex. 1-6	a-CN	HT-3	—	790	252	1.875	752	270	2.009	Δ
Ex. 4-21	a-CB	HT-3	2-4-1	809	191	1.438	817	194	1.461	∘
Ex. 4-22	a-CB	HT-3	2-5-3	780	192	1.389	798	190	1.375	∘
C. Ex. 1-7	a-CB	HT-3	—	801	222	1.667	746	238	1.787	x
Ex. 4-23	a-CF	HT-3	2-4-1	801	212	1.559	798	209	1.537	∘
Ex. 4-24	a-CF	HT-3	2-5-3	806	208	1.531	801	208	1.511	∘
C. Ex. 1-8	a-CF	HT-3	—	788	232	1.745	734	248	1.865	x
Ex. 4-25	a-BN	HT-3	2-4-1	809	182	1.376	790	175	1.323	∘
Ex. 4-26	a-BN	HT-3	2-5-3	796	174	1.330	812	169	1.292	∘
C. Ex. 1-9	a-BN	HT-3	—	785	203	1.595	752	233	1.831	x

[0449] It was confirmed from the table that if the type of the surface protective layer was further changed, the same results as the above were obtained according to the compositions of the single-layer photosensitive layer as the base.

[0450] According to the results of the solvent resistance test listed in the table, all the electrophotosensitive materials of Examples 4-17 to 4-26 suffered no cracks nor delamination of the surface protective layer. It was thus concluded that the use of the diindenopyrazine compounds of the formulas (2-4), (2-5) contributed the improvement of the physical stability of the inorganic surface protective layer.

[0451] It was also confirmed that all the electrophotosensitive materials of these examples were free from serious decrease in photosensitivity when formed with the surface protective layer and thus maintained high photosensitivity, because they had small residual potentials after light exposure and half-life exposures.

[0452] In addition, all the electrophotosensitive materials of these examples were free from significant increase in residual potential and half-life exposure after the durability test. Based on this fact and the results of the solvent resistance test, it was concluded that these electrophotosensitive materials achieved greater improvement in durability than the prior-art products.

[0453] Multi-layer Electrophotosensitive Material

Examples 4-27 to 4-30

[0454] Electrophotosensitive materials of Examples 4-27 to 4-30 were fabricated the same way as in Example 1-35 except that each of the examples used 0.2 parts by weight of diindenopyrazine compound of the formula of a number listed in Table 22.

Examples 4-31 to 4-34

[0455] Electrophotosensitive materials of Examples 4-31 to 4-34 were fabricated the same way as in Example 1-41 except that each of the examples used 40 parts by weight of diindenopyrazine compound of the formula of a number listed in Table 22.

[0456] The electrophotosensitive materials of the above examples were subjected to the same photosensitivity test (II), durability test (II) and solvent resistance test as the above and were evaluated for the characteristics thereof. The results as well as those of Comparative Examples 1-10, 1-11 are listed in Table 22.

	TABLE 22
	Initial	After durability test
	HLE		HLE
	P-H		SP	RP	E½	SP	RP	E½
	SPL	TM	DIP	V0(V)	Vr(V)	(μJ/cm2)	V0(V)	Vr(V)	(μJ/cm2)	SRT
Ex. 4-27	a-SiC	HT-1	2-4-1	−806	−147	0.830	−798	−142	0.811	∘
Ex. 4-28	a-SiC	HT-1	2-4-3	−808	−148	0.853	−798	−145	0.836	∘
Ex. 4-29	a-SiC	HT-1	2-5-2	−807	−132	0.802	−804	−131	0.796	∘
Ex. 4-30	a-SiC	HT-1	2-5-3	−808	−145	0.838	−801	−148	0.855	∘
C. Ex. 1-10	a-SiC	HT-1	—	−806	−165	0.938	−782	−192	1.052	x
Ex. 4-31	a-SiC	HT-3	2-4-1	−792	−124	0.915	−798	−127	0.937	∘
Ex. 4-32	a-SiC	HT-3	2-4-3	−804	−125	0.923	−812	−130	0.960	∘
Ex. 4-33	a-SiC	HT-3	2-5-2	−814	−123	0.869	−812	−125	0.883	∘
Ex. 4-34	a-SiC	HT-3	2-5-3	−817	−128	0.923	−810	−125	0.901	∘
C. Ex. 1-11	a-SiC	HT-3	—	−814	−147	1.024	−776	−176	1.226	x

[0457] It was confirmed from the table that if the single-layer photosensitive layer was replaced by the multi-layer photosensitive layer, the same results as the above were obtained according to the compositions of the charge transport layer defining the outermost part thereof.

[0458] According to the results of the solvent resistance test listed in the table, all the electrophotosensitive materials of Examples 4-27 to 4-34 suffered no cracks nor delamination of the surface protective layer. It was thus concluded that the use of the diindenopyrazine compounds of the formulas (2-4), (2-5) contributed the improvement of the physical stability of the inorganic surface protective layer.

[0459] It was also confirmed that all the electrophotosensitive materials of these examples were free from serious decrease in photosensitivity when formed with the surface protective layer and thus maintained high photosensitivity, because they had small residual potentials after light exposure and half-life exposures.

[0460] In addition, all the electrophotosensitive materials of these examples were free from significant increase in residual potential and half-life exposure after the durability test. Based on this fact and the results of the solvent resistance test, it was concluded that these electrophotosensitive materials achieved greater improvement in durability than the prior-art products.

Examples 4-35 to 4-42

[0461] Electrophotosensitive materials of these examples were fabricated the same way as in Examples 4-27 to 4-34 except that the same procedure as in Examples 1-13 to 1-24 was taken to form a surface protective layer of amorphous carbon (C) having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the multi-layer photosensitive layer.

[0462] The electrophotosensitive materials of the above examples were subjected to the same photosensitivity test (II), durability test (II) and solvent resistance test as the above and were evaluated for the characteristics thereof. The results as well as those of Comparative Examples 1-12, 1-13 are listed in Table 23.

	TABLE 23
	Initial	After durability test
	HLE		HLE
	P-H		SP	RP	E½	SP	RP	E½
	SPL	TM	DIP	V0(V)	Vr(V)	(μJ/cm2)	V0(V)	Vr(V)	(μJ/cm2)	SRT
Ex. 4-35	a-C	HT-1	2-4-1	−814	−152	1.086	−806	−148	1.057	∘
Ex. 4-36	a-C	HT-1	2-4-3	−788	−158	1.116	−796	−160	1.130	∘
Ex. 4-37	a-C	HT-1	2-5-2	−802	−150	1.058	−814	−148	1.044	∘
Ex. 4-38	a-C	HT-1	2-5-3	−812	−152	1.106	−817	−157	1.142	∘
C. Ex. 1-12	a-C	HT-1	—	−785	−172	1.216	−748	−198	1.400	x
Ex. 4-39	a-C	HT-3	2-4-1	−785	−130	0.990	−788	−128	0.975	∘
Ex. 4-40	a-C	HT-3	2-4-3	−802	−136	1.017	−806	−134	1.002	∘
Ex. 4-41	a-C	HT-3	2-5-2	−798	−122	0.947	−806	−126	0.978	∘
Ex. 4-42	a-C	HT-3	2-5-3	−780	−138	0.990	−785	−132	0.957	∘
C. Ex. 1-13	a-C	HT-3	—	−817	−146	1.098	−771	−178	1.339	x

[0463] It was confirmed from the table that if the type of the surface protective layer was changed, the same results as the above were obtained according to the compositions of the charge transport layer of the multi-layer photosensitive layer as the base.

[0464] According to the results of the solvent resistance test listed in the table, all the electrophotosensitive materials of Examples 4-35 to 4-42 suffered no cracks nor delamination of the surface protective layer. It was thus concluded that the use of the diindenopyrazine compounds of the formulas (2-4), (2-5) contributed the improvement of the physical stability of the inorganic surface protective layer.

[0465] It was also confirmed that all the electrophotosensitive materials of these examples were free from serious decrease in photosensitivity when formed with the surface protective layer and thus maintained high photosensitivity, because they had small residual potentials after light exposure and half-life exposures.

[0466] In addition, all the electrophotosensitive materials of these examples were free from significant increase in residual potential and half-life exposure after the durability test. Based on this fact and the results of the solvent resistance test, it was concluded that these electrophotosensitive materials achieved greater improvement in durability than the prior-art products.

Examples 4-43, 4-44

[0467] Electrophotosensitive materials of these examples were fabricated the same way as in Examples 4-31, 4-34 except that the same procedure as in Examples 1-25, 1-26 was taken to form a surface protective layer of amorphous silicon-nitrogen (SiN) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the multi-layer photosensitive layer.

Examples 4-45, 4-46

[0468] Electrophotosensitive materials of these examples were fabricated the same way as in Examples 4-31, 4-34 except that the same procedure as in Examples 1-27, 1-28 was taken to form a surface protective layer of amorphous carbon-nitrogen (CN) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the multi-layer photosensitive layer.

Examples 4-47, 4-48

[0469] Electrophotosensitive materials of these examples were fabricated the same way as in Examples 4-31, 4-34 except that the same procedure as in Examples 1-29, 1-30 was taken to form a surface protective layer of amorphous carbon-boron (CB) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the multi-layer photosensitive layer.

Examples 4-49, 4-50

[0470] Electrophotosensitive materials of these examples were fabricated the same way as in Examples 4-31, 4-34 except that the same procedure as in Examples 1-31, 1-32 was taken to form a surface protective layer of amorphous carbon-fluorine (CF) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the multi-layer photosensitive layer.

Examples 4-51, 4-52

[0471] Electrophotosensitive materials of these examples were fabricated the same way as in Examples 4-31, 4-34 except that the same procedure as in Examples 1-33, 1-34 was taken to form a surface protective layer of amorphous boron-nitrogen (BN) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the multi-layer photosensitive layer.

[0472] The electrophotosensitive materials of the above examples were subjected to the same photosensitivity test (II), durability test (II) and solvent resistance test as the above and were evaluated for the characteristics thereof. The results as well as those of Comparative Examples 1-14 to 1-18 are listed in Table 24.

	TABLE 24
	Initial	After durability test
	HLE		HLE
	P-H		SP	RP	E½	SP	RP	E½
	SPL	TM	DIP	V0(V)	Vr(V)	(μJ/cm2)	V0(V)	Vr(V)	(μJ/cm2)	SRT
Ex. 4-43	a-SiN	HT-3	2-4-1	−802	−132	0.987	−812	−130	0.972	∘
Ex. 4-44	a-SiN	HT-3	2-5-3	−795	−125	0.970	−785	−122	0.947	∘
C. Ex. 1-14	a-SiN	HT-3	—	−785	−149	1.095	−758	−186	1.367	Δ
Ex. 4-45	a-CN	HT-3	2-4-1	−801	−123	1.032	−796	−133	1.116	∘
Ex. 4-46	a-CN	HT-3	2-5-3	−788	−138	0.823	−782	−136	0.811	∘
C. Ex. 1-15	a-CN	HT-3	—	−793	−148	1.155	−762	−177	1.381	x
Ex. 4-47	a-CB	HT-3	2-4-1	−814	−111	0.845	−805	−109	0.830	∘
Ex. 4-48	a-CB	HT-3	2-5-3	−806	−112	0.816	−804	−110	0.801	∘
C. Ex. 1-16	a-CB	HT-3	—	−793	−137	0.979	−746	−167	1.193	x
Ex. 4-49	a-CF	HT-3	2-4-1	−817	−115	0.912	−809	−117	0.928	∘
Ex. 4-50	a-CF	HT-3	2-5-3	−809	−112	0.896	−817	−117	0.936	∘
C. Ex. 1-17	a-CF	HT-3	—	−793	−139	1.021	−766	−178	1.307	x
Ex. 4-51	a-BN	HT-3	2-4-1	−789	−98	0.790	−796	−101	0.804	∘
Ex. 4-52	a-BN	HT-3	2-5-3	−790	−96	0.753	−782	−98	0.769	∘
C. Ex. 1-18	a-BN	HT-3	—	−780	−117	0.904	−748	−146	1.128	x

[0473] It was confirmed from the table that if the type of the surface protective layer was further changed, the same results as the above were obtained according to the compositions of the charge transport layer of the multi-layer photosensitive layer as the base.

[0474] According to the results of the solvent resistance test listed in the table, all the electrophotosensitive materials of Examples 4-43 to 4-52 suffered no cracks nor delamination of the surface protective layer. It was thus concluded that the use of the diindenopyrazine compounds of the formulas (2-4), (2-5) contributed the improvement of the physical stability of the inorganic surface protective layer.

[0475] It was also confirmed that all the electrophotosensitive materials of these examples were free from serious decrease in photosensitivity when formed with the surface protective layer and thus maintained high photosensitivity, because they had small residual potentials after light exposure and half-life exposures.

[0476] In addition, all the electrophotosensitive materials of these examples were free from significant increase in residual potential and half-life exposure after the durability test. Based on this fact and the results of the solvent resistance test, it was concluded that these electrophotosensitive materials achieved greater improvement in durability than the prior-art products.

[0477] Single-layer Electrophotosensitive Material

Examples 5-1 to 5-4

[0478] Electrophotosensitive materials of Examples 5-1 to 5-4 were fabricated the same way as in Example 1-1 except that each of the examples used 40 parts by weight of dioxotetracenedione compound of the formula of a number listed in Table 25.

Examples 5-5 to 5-8

[0479] Electrophotosensitive materials of Examples 5-5 to 5-8 were fabricated the same way as in Example 1-7 except that each of the examples used 40 parts by weight of dioxotetracenedione compound of the formula of a number listed in Table 25.

[0480] The electrophotosensitive materials of the above examples were subjected to the same photosensitivity test (I), durabilitytest (I) andsolvent resistancetest as the above and were evaluated for the characteristics thereof. The results as well as those of Comparative Examples 1-1, 1-2 are listed in Table 25.

	TABLE 25
	Initial	After durability test
	HLE		HLE
	P-H		SP	RP	E½	SP	RP	E½
	SPL	TM	DOT	V0(V)	Vr(V)	(μJ/cm2)	V0(V)	Vr(V)	(μJ/cm2)	SRT
Ex. 5-1	a-SiC	HT-1	2-6-3	798	186	1.364	788	188	1.379	∘
Ex. 5-2	a-SiC	HT-1	2-6-6	780	199	1.390	790	193	1.348	∘
Ex. 5-3	a-SiC	HT-1	2-6-8	780	188	1.340	785	184	1.311	∘
Ex. 5-4	a-SiC	HT-1	2-6-11	817	178	1.315	806	185	1.356	∘
C. Ex. 1-1	a-SiC	HT-1	—	817	205	1.500	745	244	1.785	x
Ex. 5-5	a-SiC	HT-3	2-6-3	793	216	1.503	802	214	1.489	∘
Ex. 5-6	a-SiC	HT-3	2-6-6	788	217	1.530	796	220	1.551	∘
Ex. 5-7	a-SiC	HT-3	2-6-8	785	215	1.476	782	212	1.455	∘
Ex. 5-8	a-SiC	HT-3	2-6-11	817	211	1.462	807	209	1.448	∘
C. Ex. 1-2	a-SiC	HT-3	—	804	232	1.667	748	252	1.810	Δ
DOT: Dioxotetracenedione compound

[0481] According to the results of the solvent resistance test listed in the table, all the electrophotosensitive materials of Examples 5-1 to 5-8 suffered no cracks nor delamination of the surface protective layer. It was thus concluded that the use of the dioxotetracenedione compound of the formula (2-6) contributed the improvement of the physical stability of the inorganic surface protective layer.

[0482] It was also confirmed that all the electrophotosensitive materials of these examples were free from serious decrease in photosensitivity when formed with the surface protective layer and thus maintained high photosensitivity, because they had small residual potentials after light exposure and half-life exposures.

[0483] In addition, all the electrophotosensitive materials of these examples were free from significant increase in residual potential and half-life exposure after the durability test. Based on this fact and the results of the solvent resistance test, it was concluded that these electrophotosensitive materials achieved greater improvement in durability than the prior-art products.

Examples 5-9 to 5-16

[0484] Electrophotosensitive materials of Examples 5-9 to 5-16 were fabricated the same way as in Examples 5-1 to 5-8 except that the same procedure as in Examples 1-13 to 1-24 was taken to form a surface protective layer of amorphous carbon (C) having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the single-layer photosensitive layer.

[0485] The electrophotosensitive materials of the above examples were subjected to the same photosensitivity test (I), durabilitytest (I) andsolvent resistancetest as the above and were evaluated for the characteristics thereof. The results as well as those of Comparative Examples 1-3, 1-4 are listed in Table 26.

	TABLE 26
	Initial	After durability test
	HLE		HLE
	P-H		SP	RP	E½	SP	RP	E½
	SPL	TM	DOT	V0(V)	Vr(V)	(μJ/cm2)	V0(V)	Vr(V)	(μJ/cm2)	SRT
Ex. 5-9	a-C	HT-1	2-6-3	817	195	1.435	809	193	1.420	∘
Ex. 5-10	a-C	HT-1	2-6-6	798	199	1.461	804	193	1.417	∘
Ex. 5-11	a-C	HT-1	2-6-8	801	187	1.408	809	189	1.423	∘
Ex. 5-12	a-C	HT-1	2-6-11	803	193	1.396	809	195	1.410	∘
C. Ex. 1-3	a-C	HT-1	—	793	208	1.563	742	238	1.788	x
Ex. 5-13	a-C	HT-3	2-6-3	814	215	1.583	804	210	1.536	∘
Ex. 5-14	a-C	HT-3	2-6-6	809	194	1.544	801	192	1.528	∘
Ex. 5-15	a-C	HT-3	2-6-8	780	185	1.489	788	190	1.529	∘
Ex. 5-16	a-C	HT-3	2-6-11	793	191	1.502	801	194	1.526	∘
C. Ex. 1-4	a-C	HT-3	—	788	222	1.667	746	240	1.792	x

[0486] It was confirmed from the table that if the type of the surface protective layer was changed, the same results as the above were obtained according to the compositions of the single-layer photosensitive layer as the base.

[0487] According to the results of the solvent resistance test listed in the table, all the electrophotosensitive materials of Examples 5-9 to 5-16 suffered no cracks nor delamination of the surface protective layer. It was thus concluded that the use of the dioxotetracenedione compound of the formula (2-6) contributed the improvement of the physical stability of the inorganic surface protective layer.

[0488] It was also confirmed that all the electrophotosensLtive materials of these examples were free from serious decrease in photosensitivity when formed with the surface protective layer and thus maintained high photosensitivity, because they had small residual potentials after light exposure and half-life exposures.

[0489] In addition, all the electrophotosensitive materials of these examples were free from significant increase in residual potential and half-life exposure after the durability test. Based on this fact and the results of the solvent resistance test, it was concluded that these electrophotosensitive materials achieved greater improvement in durability than the prior-art products.

Examples 5-17, 5-18

[0490] Electrophotosensitive materials of Examples 5-17, 5-18 were fabricated the same way as in Examples 5-5, 5-7 except that the same procedure as in Examples 1-25, 1-26 was taken to form a surface protective layer of amorphous silicon-nitrogen (SiN) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the single-layer photosensitive layer.

Examples 5-19, 5-20

[0491] Electrophotosensitive materials of Examples 5-19, 5-20 were fabricated the same way as in Examples 5-5, 5-7 except that the same procedure as in Examples 1-27, 1-28 was taken to form a surface protective layer of amorphous carbon-nitrogen (CN) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the single-layer photosensitive layer.

Examples 5-21, 5-22

[0492] Electrophotosensitive materials of Examples 5-21, 5-22 were fabricated the same way as in Examples 5-5, 5-7 except that the same procedure as in Examples 1-29, 1-30 was taken to form a surface protective layer of amorphous carbon-boron (CB) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the single-layer photosensitive layer.

Examples 5-23, 5-24

[0493] Electrophotosensitive materials of Examples 5-23, 5-24 were fabricated the same way as in Examples 5-5, 5-7 except that the same procedure as in ExampLes 1-31, 1-32 was taken to form a surface protective layer of amorphous carbon-fluorine (CF) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the single-layer photosensitive layer.

Examples 5-25, 5-26

[0494] Electrophotosensitive materials of Examples 5-25, 5-26 were fabricated the same way as in Examples 5-5, 5-7 except that the same procedure as in Examples 1-33, 1-34 was taken to form a surface protective layer of amorphous boron-nitrogen (BN) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the single-layer photosensitive layer.

[0495] The electrophotosensitive materials of the above examples were subjected to the same photosensitivity test (I),durability test (I) and solvent resistance test as the above and were evaluated for the characteristics thereof. The results as well as those of Comparative Examples 1-5 to 1-9 are listed in Table 27.

	TABLE 27
	Initial	After durability test
	HLE		HLE
	P-H		SP	RP	E½	SP	RP	E½
	SPL	TM	DOT	V0(V)	Vr(V)	(μJ/cm2)	V0(V)	Vr(V)	(μJ/cm2)	SRT
Ex. 5-17	a-SiN	HT-3	2-6-3	817	233	1.670	817	231	1.656	∘
Ex. 5-18	a-SiN	HT-3	2-6-8	798	222	1.625	802	225	1.647	∘
C. Ex. 1-5	a-SiN	HT-3	—	812	245	1.787	749	263	1.918	Δ
Ex. 5-19	a-CN	HT-3	2-6-3	806	238	1.737	809	236	1.722	∘
Ex. 5-20	a-CN	HT-3	2-6-8	808	234	1.690	817	228	1.647	∘
C. Ex. 1-6	a-CN	HT-3	—	790	252	1.875	752	270	2.009	Δ
Ex. 5-21	a-CB	HT-3	2-6-3	786	197	1.463	796	202	1.501	∘
Ex. 5-22	a-CB	HT-3	2-6-8	791	196	1.437	798	201	1.474	∘
C. Ex. 1-7	a-CB	HT-3	—	801	222	1.667	746	238	1.787	x
Ex. 5-23	a-CF	HT-3	2-6-3	803	224	1.647	812	228	1.676	∘
Ex. 5-24	a-CF	HT-3	2-6-8	788	216	1.572	780	219	1.594	∘
C. Ex. 1-8	a-CF	HT-3	—	788	232	1.745	734	248	1.865	x
Ex. 5-25	a-BN	HT-3	2-6-3	806	184	1.450	817	189	1.489	∘
Ex. 5-26	a-BN	HT-3	2-6-8	788	188	1.401	793	185	1.379	∘
C. Ex. 1-9	a-BN	HT-3	—	785	203	1.595	752	233	1.831	x

[0496] It was confirmed from the table that if the type of the surface protective layer was further changed, the same results as the above were obtained according to the compositions of the single-layer photosensitive layer as the base.

[0497] According to the results of the solvent resistance test listed in the table, all the electrophotosensitive materials of Examples 5-17 to 5-26 suffered no cracks nor delamination of the surface protective layer. It was thus concluded that the use of the dioxotetracenedione compound of the formula (2-6) contributed the improvement of the physical stability of the inorganic surface protective layer.

[0498] It was also confirmed that all the electrophotosensitive materials of these examples were free from serious decrease in photosensitivity when formed with the surface protective layer and thus maintained high photosensitivity, because they had small residual potentials after light exposure and half-life exposures.

[0499] In addition, all the electrophotosensitive materials of these examples were free from significant increase in residual potential and half-life exposure after the durability test. Based on this fact and the results of the solvent resistance test, it was concluded that these electrophotosensitive materials achieved greater improvement in durability than the prior-art products.

[0500] Multi-layer Electrophotosensitive Material

Examples 5-27 to 5-30

[0501] Electrophotosensitive materials of Examples 5-27 to 5-30 were fabricated the same way as in Example 1-35 except that each of the examples used 0.2 parts by weight of dioxotetracenedione compound of the formula of a number listed in Table 28.

Examples 5-31 to 5-34

[0502] Electrophotosensitive materials of Examples 5-31 to 5-34 were fabricated the same way as in Example 1-41 except that each of the examples used 40 parts by weight of dioxotetracenedione compound of the formula of a number listed in Table 28.

[0503] The electrophotosensitive materials of the above examples were subjected to the same photosensitivity test (II), durability test (II) and solvent resistance test as the above and were evaluated for the characteristics thereof. The results as well as those of Comparative Examples 1-10, 1-11 are listed in Table 28.

	TABLE 28
	Initial	After durability test
	HLE		HLE
	P-H		SP	RP	E½	SP	RP	E½
	SPL	TM	DOT	V0(V)	Vr(V)	(μJ/cm2)	V0(V)	Vr(V)	(μJ/cm2)	SRT
Ex. 5-27	a-SiC	HT-1	2-6-3	−796	−144	0.861	−792	−147	0.879	∘
Ex. 5-28	a-SiC	HT-1	2-6-6	−795	−145	0.877	−802	−152	0.919	∘
Ex. 5-29	a-SiC	HT-1	2-6-8	−812	−149	0.846	−809	−144	0.818	∘
Ex. 5-30	a-SiC	HT-1	2-6-11	−793	−139	0.830	−790	−147	0.878	∘
C. Ex.	a-SiC	HT-1	—	−806	−165	0.938	−782	−192	1.052	x
1-10
Ex. 5-31	a-SiC	HT-3	2-6-3	−817	−132	0.948	−808	−137	0.984	∘
Ex. 5-32	a-SiC	HT-3	2-6-6	−814	−133	0.967	−804	−134	0.982	∘
Ex. 5-33	a-SiC	HT-3	2-6-8	−812	−124	0.931	−810	−126	0.946	∘
Ex. 5-34	a-SiC	HT-3	2-6-11	−798	−125	0.923	−792	−128	0.945	∘
C. Ex.	a-SiC	HT-3	—	−814	−147	1.024	−776	−176	1.226	x
1-11

[0504] It was confirmed from the table that if the single-layer photosensitive layer was replaced by the multi-layer photosensitive layer, the same results as the above were obtained according to the compositions of the charge transport layer defining the outermost part thereof.

[0505] According to the results of the solvent resistance test listed in the table, all the electrophotosensitive materials of Examples 5-27 to 5-34 suffered no cracks nor delamination of the surface protective layer. It was thus concluded that the use of the dioxotetracenedione compound of the formula (2-6) contributed the improvement of the physical stability of the inorganic surface protective layer.

[0506] It was also confirmed that all the electrophotosensitive materials of these examples were free from serious decrease in photosensitivity when formed with the surface protective layer and thus maintained high photosensitivity, because they had small residual potentials after light exposure and half-life exposures.

[0507] In addition, all the electrophotosensitive materials of these examples were free from significant increase in residual potential and half-life exposure after the durability test. Based on this fact and the results of the solvent resistance test, it was concluded that these electrophotosensitive materials achieved greater improvement in durability than the prior-art products.

Examples 5-35 to 5-42

[0508] Electrophotosensitive materials of these examples were fabricated the same way as in Examples 5-27 to 5-34 except that the same procedure as in Examples 1-13 to 1-24 was taken to form a surface protective layer of amorphous carbon (C) having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the multi-layer photosensitive layer.

[0509] The electrophotosensitive materials of the above examples were subjected to the same photosensitivity test (II), durability test (II) and solvent resistance test as the above and were evaluated for the characteristics thereof. The results as well as those of Comparative Examples 1-12, 1-13 are listed in Table 29.

	TABLE 29
	Initial	After durability test
	HLE		HLE
	P-H		SP	RP	E½	SP	RP	E½
	SPL	TM	DOT	V0(V)	Vr(V)	(μJ/cm2)	V0(V)	Vr(V)	(μJ/cm2)	SRT
Ex. 5-35	a-C	HT-1	2-6-3	−788	−151	1.137	−796	−155	1.167	∘
Ex. 5-36	a-C	HT-1	2-6-6	−790	−161	1.137	−798	−158	1.116	∘
Ex. 5-37	a-C	HT-1	2-6-8	−796	−151	1.116	−786	−156	1.153	∘
Ex. 5-38	a-C	HT-1	2-6-11	−790	−157	1.106	−788	−154	1.085	∘
C. Ex.	a-C	HT-1	—	−785	−172	1.216	−748	−198	1.400	x
1-12
Ex. 5-39	a-C	HT-3	2-6-3	−801	−136	1.017	−809	−133	0.995	∘
Ex. 5-40	a-C	HT-3	2-6-6	−809	−136	1.017	−806	−134	1.002	∘
Ex. 5-41	a-C	HT-3	2-6-8	−790	−126	0.998	−788	−130	1.030	∘
Ex. 5-42	a-C	HT-3	2-6-11	−798	−128	0.998	−804	−126	0.982	∘
C. Ex.	a-C	HT-3	—	−817	−146	1.098	−771	−178	1.339	x
1-13

[0510] It was confirmed from the table that if the type of the surface protective layer was changed, the same results as the above were obtained according to the compositions of the charge transport layer of the multi-layer photosensitive layer as the base.

[0511] According to the results of the solvent resistance test listed in the table, all the electrophotosensitive materials of Examples 5-35 to 5-42 suffered no cracks nor delamination of the surface protective layer. It was thus concluded that the use of the dioxotetracenedione compound of the formula (2-6) contributed the improvement of the physical stability of the inorganic surface protective layer.

[0512] It was also confirmed that all the electrophotosensitive materials of these examples were free from serious decrease in photosensitivity when formed with the surface protective layer and thus maintained high photosensitivity, because they had small residual potentials after light exposure and half-life exposures.

[0513] In addition, all the electrophotosensitive materials of these examples were free from significant increase in residual potential and half-life exposure after the durability test. Based on this fact and the results of the solvent resistance test, it was concluded that these electrophotosensitive materials achieved greater improvement in durability than the prior-art products.

Examples 5-43, 5-44

[0514] Electrophotosensitive materials of these examples were fabricated the same way as in Examples 5-31, 5-33 except that the same procedure as in Examples 1-25, 1-26 was taken to form a surface protective layer of amorphous silicon-nitrogen (SiN) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the multi-layer photosensitive layer.

Examples 5-45, 5-46

[0515] Electrophotosensitive materials of these examples were fabricated the same way as in Examples 5-31, 5-33 except that the same procedure as in Examples 1-27, 1-28 was taken to form a surface protective layer of amorphous carbon-nitrogen (CN) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the multi-layer photosensitive layer.

Examples 5-47, 5-48

[0516] Electrophotosensitive materials of these examples were fabricated the same way as in Examples 5-31, 5-33 except that the same procedure as in Examples 1-29, 1-30 was taken to form a surface protective layer of amorphous carbon-boron (CB) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the multi-layer photosensitive layer.

Examples 5-49, 5-50

[0517] Electrophotosensitive materials of these examples were fabricated the same way as in Examples 5-31, 5-33 except that the same procedure as in Examples 1-31, 1-32 was taken to form a surface protective layer of amorphous carbon-fluorine (CF) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the multi-layer photosensitive layer.

Examples 5-51, 5-52

[0518] Electrophotosensitive materials of these examples were fabricated the same way as in Examples 5-31, 5-33 except that the same procedure as in Examples 1-33, 1-34 was taken to form a surface protective layer of amorphous boron-nitrogen (BN) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the multi-layer photosensitive layer.

[0519] The electrophotosensitive materials of the above examples were subjected to the same photosensitivity test (II), durability test (II) and solvent resistance test as the above and were evaluated for the characteristics thereof. The results as well as those of Comparative Examples 1-14 to 1-18 are listed in Table 30.

	TABLE 30
	Initial	After durability test
	HLE		HLE
	P-H		SP	RP	E½	SP	RP	E½
	SPL	TM	DOT	V0(V)	Vr(V)	(μJ/cm2)	V0(V)	Vr(V)	(μJ/cm2)	SRT
Ex. 5-43	a-SiN	HT-3	2-6-3	−785	−133	1.015	−782	−136	1.038	∘
Ex. 5-44	a-SiN	HT-3	2-6-8	−796	−132	0.987	−795	−130	0.972	∘
C. Ex.	a-SiN	HT-3	—	−785	−149	1.095	−758	−186	1.367	Δ
1-14
Ex. 5-45	a-CN	HT-3	2-6-3	−796	−129	1.061	−804	−131	1.077	∘
Ex. 5-46	a-CN	HT-3	2-6-8	−806	−138	0.838	−812	−136	0.826	∘
C. Ex.	a-CN	HT-3	—	−793	−148	1.155	−762	−177	1.381	x
1-15
Ex. 5-47	a-CB	HT-3	2-6-3	−809	−118	0.874	−806	−115	0.852	∘
Ex. 5-48	a-CB	HT-3	2-6-8	−801	−111	0.859	−798	−108	0.836	∘
C. Ex.	a-CB	HT-3	—	−793	−137	0.979	−746	−167	1.193	x
1-16
Ex. 5-49	a-CF	HT-3	2-6-3	−801	−122	0.928	−807	−125	0.951	∘
Ex. 5-50	a-CF	HT-3	2-6-8	−788	−118	0.920	−782	−116	0.904	∘
C. Ex.	a-CF	HT-3	—	−793	−139	1.021	−766	−178	1.307	x
1-17
Ex. 5-51	a-BN	HT-3	2-6-3	−796	−103	0.793	−798	−98	0.755	∘
Ex. 5-52	a-BN	HT-3	2-6-8	−789	−94	0.780	−798	−96	0.797	∘
C. Ex.	a-BN	HT-3	—	−780	−117	0.904	−748	−146	1.128	x
1-18

[0520] It was confirmed from the table that if the type of the surface protective layer was further changed, the same results as the above were obtained according to the compositions of the charge transport layer of the multi-layer photosensitive layer as the base.

[0521] According to the results of the solvent resistance test listed in the table, all the electrophotosensitive materials of Examples 5-43 to 5-52 suffered no cracks nor delamination of the surface protective layer. It was thus concluded that the use of the dioxotetracenedione compound of the formula (2-6) contributed the improvement of the physical stability of the inorganic surface protective layer.

[0522] It was also confirmed that all the electrophotosensitive materials of these examples were free from serious decrease in photosensitivity when formed with the surface protective layer and thus maintained high photosensitivity, because they had small residual potentials after light exposure and half-life exposures.

[0523] In addition, all the electrophotosensitive materials of these examples were free from significant increase in residual potential and half-life exposure after the durability test. Based on this fact and the results of the solvent resistance test, it was concluded that these electrophotosensitive materials achieved greater improvement in durability than the prior-art products.

[0524] Single-layer Electrophotosensitive Material

Examples 6-1 to 6-4

[0525] Electrophotosensitive materials of Examples 6-1 to 6-4 were fabricated the same way as in Example 1-1 except that each of the examples used 40 parts by weight of naphthylene diimide derivative of the formula of a number listed in Table 31.

Examples 6-5 to 6-8

[0526] Electrophotosensitive materials of Examples 6-5 to 6-8 were fabricated the same way as in Example 1-7 except that each of the examples used 40 parts by weight of naphthylene diimide derivative of the formula of a number listed in Table 31.

[0527] The electrophotosensitive materials of the above examples were subjected to the same photosensitivity test (I), durabilitytest (I) and solvent resistance test as the above and were evaluated for the characteristics thereof. The results as well as those of Comparative Examples 1-1, 1-2 are listed in Table 31.

	TABLE 31
	Initial	After durability test
						HLE			HLE
		P-H		SP	RP	E½	SP	RP	E½
	SPL	TM	NDI	V0(V)	Vr(V)	(μJ/cm2)	V0(V)	Vr(V)	(μJ/cm2)	SRT
Ex. 6-1	a-SiC	HT-1	3-1-3	809	145	1.049	798	147	1.063	◯
Ex. 6-2	a-SiC	HT-1	3-1-7	798	156	1.112	795	161	1.148	◯
Ex. 6-3	a-SiC	HT-1	3-1-10	796	165	1.154	793	168	1.175	◯
Ex. 6-4	a-SiC	HT-1	3-1-12	806	148	1.035	801	152	1.063	◯
C. Ex. 1-1	a-SiC	HT-1	—	817	205	1.500	745	244	1.785	X
Ex. 6-5	a-SiC	HT-3	3-1-3	795	172	1.183	785	174	1.197	◯
Ex. 6-6	a-SiC	HT-3	3-1-7	784	173	1.226	782	178	1.261	◯
Ex. 6-7	a-SiC	HT-3	3-1-10	788	183	1.264	785	181	1.250	◯
Ex. 6-8	a-SiC	HT-3	3-1-12	812	163	1.158	806	168	1.194	◯
C. Ex. 1-2	a-SiC	HT-3	—	804	232	1.667	748	252	1.810	Δ
NDI: Naphtylenediimide compound

[0528] According to the results of the solvent resistance test listed in the table, all the electrophotosensitive materials of Examples 6-1 to 6-8 suffered no cracks nor delamination of the surface protective layer. It was thus concluded that the use of the naphthylene diimide derivative of the formula (3) contributed the improvement of the physical stability of the inorganic surface protective layer.

[0529] It was also confirmed that all the electrophotosensitive materials of these examples were free from serious decrease in photosensitivity when formed with the surface protective layer and thus maintained high photosensitivity, because they had small residual potentials after light exposure and half-life exposures.

[0530] In addition, all the electrophotosensitive materials of these examples were free from significant increase in residual potential and half-life exposure after the durability test. Based on this fact and the results of the solvent resistance test, it was concluded that these electrophotosensitive materials achieved greater improvement in durability than the prior-art products. Examples 6-9 to 6-16 Electrophotosensitive materials of Examples 6-9 to 6-16 were fabricated the same way as in Examples 6-1 to 6-8 except that the same procedure as in Examples 1-13 to 1-24 was taken to form a surface protective layer of amorphous carbon (C) having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the single-layer photosensitive layer.

[0531] The electrophotosensitive materials of the above examples were subjected to the same photosensitivity test (I), durability test (I) and solvent resistance test as the above and were evaluated for the characteristics thereof. The results as well as those of Comparative Examples 1-3, 1-4 are listed in Table 32.

	TABLE 32
	Initial	After durability test
						HLE			HLE
		P-H		SP	RP	E½	SP	RP	E½
	SPL	TM	NDI	V0(V)	Vr(V)	(μJ/cm2)	V0(V)	Vr(V)	(μJ/cm2)	SRT
Ex. 6-9	a-C	HT-1	3-1-3	806	151	1.117	798	158	1.169	◯
Ex. 6-10	a-C	HT-1	3-1-7	788	157	1.185	785	162	1.223	◯
Ex. 6-11	a-C	HT-1	3-1-10	801	170	1.222	792	172	1.236	◯
Ex. 6-12	a-C	HT-1	3-1-12	796	152	1.093	799	156	1.122	◯
C. Ex. 1-3	a-C	HT-1	—	793	208	1.563	742	238	1.788	X
Ex. 6-13	a-C	HT-3	3-1-3	795	162	1.182	790	164	1.197	◯
Ex. 6-14	a-C	HT-3	3-1-7	812	163	1.273	809	166	1.296	◯
Ex. 6-15	a-C	HT-3	3-1-10	782	170	1.282	785	172	1.297	◯
Ex. 6-16	a-C	HT-3	3-1-12	796	152	1.143	793	150	1.128	◯
C. Ex. 1-4	a-C	HT-3	—	788	222	1.667	746	240	1.792	X

[0532] It was confirmed from the table that if the type of the surface protective layer was changed, the same results as the above were obtained according to the compositions of the single-layer photosensitive layer as the base.

[0533] According to the results of the solvent resistance test listed in the table, all the electrophotosensitive materials of Examples 6-9 to 6-16 suffered no cracks nor delamination of the surface protective layer. It was thus concluded that the use of the naphthylene diimide derivative of the formula (3) contributed the improvement of the physical stability of the inorganic surface protective layer.

[0534] It was also confirmed that all the electrophotosensitive materials of these examples were free from serious decrease in photosensitivity when formed with the surface protective layer and thus maintained high photosensitivity, because they had small residual potentials after light exposure and half-life exposures.

[0535] In addition, all the electrophotosensitive materials of these examples were free from significant increase in residual potential and half-life exposure after the durability test. Based on this fact and the results of the solvent resistance test, it was concluded that these electrophotosensitive materials achieved greater improvement in durability than the prior-art products.

Examples 6-17, 6-18

[0536] Electrophotosensitive materials of Examples 6-17, 6-18 were fabricated the same way as in Examples 6-5, 6-8 except that the same procedure as in Examples 1-25, 1-26 was taken to form a surface protective layer of amorphous silicon-nitrogen (SiN) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the single-layer photosensitive layer.

Examples 6-19, 6-20

[0537] Electrophotosensitive materials of Examples 6-19, 6-20 were fabricated the same way as in Examples 6-5, 6-8 except that the same procedure as in Examples 1-27, 1-28 was taken to form a surface protective layer of amorphous carbon-nitrogen (CN) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the single-layer photosensitive layer.

Examples 6-21, 6-22

[0538] Electrophotosensitive materials of Examples 6-21, 6-22 were fabricated the same way as in Examples 6-5, 6-8 except that the same procedure as in Examples 1-29, 1-30 was taken to form a surface protective layer of amorphous carbon-boron (CB) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the single-layer photosensitive layer.

Examples 6-23, 6-24

[0539] Electrophotosensitive materials of Examples 6-23, 6-24 were fabricated the same way as in Examples 6-5, 6-8 except that the same procedure as in Examples 1-31, 1-32 was taken to form a surface protective layer of amorphous carbon-fluorine (CF) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the single-layer photosensitive layer.

Examples 6-25, 6-26

[0540] Electrophotosensitive materials of Examples 6-25, 6-26 were fabricated the same way as in Examples 6-5, 6-8 except that the same procedure as in Examples 1-33, 1-34 was taken to form a surface protective layer of amorphous boron-nitrogen (BN) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the single-layer photosensitive layer.

[0541] The electrophotosensitive materials of the above examples were subjected to the same photosensitivity test (I), durability test (I) and solvent resistance test as the above and were evaluated for the characteristics thereof. The results as well as those of Comparative Examples 1-5 to 1-9 are listed in Table 33.

	TABLE 33
	Initial	After durability test
						HLE			HLE
		P-H		SP	RP	E½	SP	RP	E½
	SPL	TM	NDI	V0(V)	Vr(V)	(μJ/cm2)	V0(V)	Vr(V)	(μJ/cm2)	SRT
Ex. 6-17	a-SiN	HT-3	3-1-3	812	185	1.315	803	187	1.329	◯
Ex. 6-18	a-SiN	HT-3	3-1-12	798	185	1.277	786	187	1.291	◯
C. Ex. 1-5	a-SiN	HT-3	—	812	245	1.787	749	263	1.918	Δ
Ex. 6-19	a-CN	HT-3	3-1-3	814	191	1.390	805	194	1.412	◯
Ex. 6-20	a-CN	HT-3	3-1-12	813	190	1.359	806	192	1.373	◯
C. Ex. 1-6	a-CN	HT-3	—	790	252	1.875	752	270	2.009	Δ
Ex. 6-21	a-CB	HT-3	3-1-3	793	157	1.183	788	160	1.206	◯
Ex. 6-22	a-CB	HT-3	3-1-12	811	162	1.167	803	160	1.153	◯
C. Ex. 1-7	a-CB	HT-3	—	801	222	1.667	746	238	1.787	X
Ex. 6-23	a-CF	HT-3	3-1-3	801	170	1.265	796	175	1.302	◯
Ex. 6-24	a-CF	HT-3	3-1-12	803	169	1.256	812	172	1.278	◯
C. Ex. 1-8	a-CF	HT-3	—	788	232	1.745	734	248	1.865	X
Ex. 6-25	a-BN	HT-3	3-1-3	814	144	1.116	809	148	1.147	◯
Ex. 6-26	a-BN	HT-3	3-1-12	801	139	1.093	807	141	1.109	◯
C. Ex. 1-9	a-BN	HT-3	—	785	203	1.595	752	233	1.831	X

[0542] It was confirmed from the table that if the type of the surface protective layer was further changed, the same results as the above were obtained according to the compositions of the single-layer photosensitive layer as the base.

[0543] According to the results of the solvent resistance test listed in the table, all the electrophotosensitive materials of Examples 6-17 to 6-26 suffered no cracks nor delamination of the surface protective layer. It was thus concluded that the use of the naphthylene diimide derivative of the formula (3) contributed the improvement of the physical stability of the inorganic surface protective layer.

[0544] It was also confirmed that all the electrophotosensitive materials of these examples were free from serious decrease in photosensitivity when formed with the surface protective layer and thus maintained high photosensitivity, because they had small residual potentials after light exposure and half-life exposures.

[0545] In addition, all the electrophotosensitive materials of these examples were free from significant increase in residual potential and half-life exposure after the durability test. Based on this fact and the results of the solvent resistance test, it was concluded that these electrophotosensitive materials achieved greater improvement in durability than the prior-art products.

[0546] Multi-layer Electrophotosensitive Material

Examples 6-27 to 6-30

[0547] Electrophotosensitive materials of Examples 6-27 to 6-30 were fabricated the same way as in Example 1-35 except that each of the examples used 0.2 parts by weight of naphthylene diimide derivative of the formula of a number listed in Table 34.

Examples 6-31 to 6-34

[0548] Electrophotosensitive materials of Examples 6-31 to 6-34 were fabricated the same way as in Example 1-41 except that each of the examples used 40 parts by weight of naphthylene diimide derivative of the formula of a number listed in Table 34.

[0549] The electrophotosensitive materials of the above examples were subjected to the same photosensitivity test (II), durability test (II) and solvent resistance test as the above and were evaluated for the characteristics thereof. The results as well as those of Comparative Examples 1-10, 1-11 are listed in Table 34.

	TABLE 34
	Initial	After durability test
						HLE			HLE
		P-H		SP	RP	E½	SP	RP	E½
	SPL	TM	NDI	V0(V)	Vr(V)	(μJ/cm2)	V0(V)	Vr(V)	(μJ/cm2)	SRT
Ex. 6-27	a-SiC	HT-1	3-1-3	−798	−135	0.783	−798	−133	0.771	◯
Ex. 6-28	a-SiC	HT-1	3-1-7	−788	−147	0.845	−801	−144	0.828	◯
Ex. 6-29	a-SiC	HT-1	3-1-10	−804	−142	0.831	−801	−137	0.811	◯
Ex. 6-30	a-SiC	HT-1	3-1-12	−790	−135	0.763	−798	−132	0.746	◯
C. Ex. 1-10	a-SiC	HT-1	—	−806	−165	0.938	−782	−192	1.052	X
Ex. 6-31	a-SiC	HT-3	3-1-3	−804	−116	0.847	−796	−114	0.832	◯
Ex. 6-32	a-SiC	HT-3	3-1-7	−817	−132	0.932	−806	−127	0.897	◯
Ex. 6-33	a-SiC	HT-3	3-1-10	−798	−123	0.923	−793	−125	0.938	◯
Ex. 6-34	a-SiC	HT-3	3-1-12	−801	−122	0.846	−798	−116	0.804	◯
C. Ex. 1-11	a-SiC	HT-3	—	−814	−147	1.024	−776	−176	1.226	X

[0550] It was confirmed from the table that if the single-layer photosensitive layer was replaced by the multi-layer photosensitive layer, the same results as the above were obtained according to the compositions of the charge transport layer defining the outermost part thereof.

[0551] According to the results of the solvent resistance test listed in the table, all the electrophotosensitive materials of Examples 6-27 to 6-34 suffered no cracks nor delamination of the surface protective layer. It was thus concluded that the use of the naphthylene diimide derivative of the formula (3) contributed the improvement of the physical stability of the inorganic surface protective layer.

[0552] It was also confirmed that all the electrophotosensitive materials of these examples were free from serious decrease in photosensitivity when formed with the surface protective layer and thus maintained high photosensitivity, because they had small residual potentials after light exposure and half-life exposures.

[0553] In addition, all the electrophotosensitive materials of these examples were free from significant increase in residual potential and half-life exposure after the durability test. Based on this fact and the results of the solvent resistance test, it was concluded that these electrophotosensitive materials achieved greater improvement in durability than the prior-art products.

Examples 6-35 to 6-42

[0554] Electrophotosensitive materials of these examples were fabricated the same way as in Examples 6-27 to 6-34 except that the same procedure as in Examples 1-13 to 1-24 was taken to form a surface protective layer of amorphous carbon (C) having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the multi-layer photosensitive layer.

[0555] The electrophotosensitive materials of the above examples were subjected to the same photosensitivity test (II), durability test (II) and solvent resistance test as the above and were evaluated for the characteristics thereof. The results as well as those of Comparative Examples 1-12, 1-13 are listed in Table 35.

	TABLE 35
	Initial	After durability test
						HLE			HLE
		P-H		SP	RP	E½	SP	RP	E½
	SPL	TM	NDI	V0(V)	Vr(V)	(μJ/cm2)	V0(V)	Vr(V)	(μJ/cm2)	SRT
Ex. 6-35	a-C	HT-1	3-1-3	−814	−141	1.031	−810	−139	1.016	◯
Ex. 6-36	a-C	HT-1	3-1-7	−793	−160	1.126	−798	−155	1.091	◯
Ex. 6-37	a-C	HT-1	3-1-10	−812	−147	1.106	−806	−147	1.106	◯
Ex. 6-38	a-C	HT-1	3-1-12	−798	−145	1.022	−793	−140	0.987	◯
C. Ex. 1-12	a-C	HT-1	—	−785	−172	1.216	−748	−198	1.400	X
Ex. 6-39	a-C	HT-3	3-1-3	−814	−121	0.947	−806	−119	0.931	◯
Ex. 6-40	a-C	HT-3	3-1-7	−817	−124	1.007	−806	−128	1.039	◯
Ex. 6-41	a-C	HT-3	3-1-10	−806	−120	0.956	−801	−117	0.932	◯
Ex. 6-42	a-C	HT-3	3-1-12	−788	−130	0.972	−790	−126	0.942	◯
C. Ex. 1-13	a-C	HT-3	—	−817	−146	1.098	−771	−178	1.339	X

[0556] It was confirmed from the table that if the type of the surface protective layer was changed, the same results as the above were obtained according to the compositions of the charge transport layer of the multi-layer photosensitive layer as the base.

[0557] According to the results of the solvent resistance test listed in the table, all the electrophotosensitive materials of Examples 6-35 to 6-42 suffered no cracks nor delamination of the surface protective layer. It was thus concluded that the use of the naphthylene diimide derivative of the formula (3) contributed the improvement of the physical stability of the inorganic surface protective layer.

[0558] It was also confirmed that all the electrophotosensitive materials of these examples were free from serious decrease in photosensitivity when formed with the surface protective layer and thus maintained high photosensitivity, because they had small residual potentials after light exposure and half-life exposures.

[0559] In addition, all the electrophotosensitive materials of these examples were free from significant increase in residual potential and half-life exposure after the durability test. Based on this fact and the results of the solvent resistance test, it was concluded that these electrophotosensitive materials achieved greater improvement in durability than the prior-art products.

Examples 6-43, 6-44

[0560] Electrophotosensitive materials of these examples were fabricated the same way as in Examples 6-31, 6-34 except that the same procedure as in Examples 1-25, 1-26 was taken to form a surface protective layer of amorphous silicon-nitrogen (SiN) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the multi-layer photosensitive layer.

Examples 6-45, 6-46

[0561] Electrophotosensitive materials of these examples were fabricated the same way as in Examples 6-31, 6-34 except that the same procedure as in Examples 1-27, 1-28 was taken to form a surface protective layer of amorphous carbon-nitrogen (CN) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the multi-layer photosensitive layer.

Examples 6-47, 6-48

[0562] Electrophotosensitive materials of these examples were fabricated the same way as in Examples 6-31, 6-34 except that the same procedure as in Examples 1-29, 1-30 was taken to form a surface protective layer of amorphous carbon-boron (CB) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the multi-layer photosensitive layer.

Examples 6-49, 6-50

[0563] Electrophotosensitive materials of these examples were fabricated the same way as in Examples 6-31, 6-34 except that the same procedure as in Examples 1-31, 1-32 was taken to form a surface protective layer of amorphous carbon-fluorine (CF) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the multi-layer photosensitive layer.

Examples 6-51, 6-52

[0564] Electrophotosensitive materials of these examples were fabricated the same way as in Examples 6-31, 6-34 except that the same procedure as in Examples 1-33, 1-34 was taken to form a surface protective layer of amorphous boron-nitrogen (BN) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the multi-layer photosensitive layer.

[0565] The electrophotosensitive materials of the above examples were subjected to the same photosensitivity test (II), durability test (II) and solvent resistance test as the above and were evaluated for the characteristics thereof. The results as well as those of Comparative Examples 1-14 to 1-18 are listed in Table 36.

	TABLE 36
	Initial	After durability test
						HLE			HLE
		P-H		SP	RP	E½	SP	RP	E½
	SPL	TM	NDI	V0(V)	Vr(V)	(μJ/cm2)	V0(V)	Vr(V)	(μJ/cm2)	SRT
Ex. 6-43	a-SiN	HT-3	3-1-3	−788	−131	0.996	−780	−126	0.958	◯
Ex. 6-44	a-SiN	HT-3	3-1-12	−793	−126	0.978	−796	−124	0.962	◯
C. Ex. 1-14	a-SiN	HT-3	—	−785	−149	1.095	−758	−186	1.367	Δ
Ex. 6-45	a-CN	HT-3	3-1-3	−814	−123	1.031	−812	−121	1.014	◯
Ex. 6-46	a-CN	HT-3	3-1-12	−801	−145	0.823	−796	−138	0.783	◯
C. Ex. 1-15	a-CN	HT-3	—	−793	−148	1.155	−762	−177	1.381	X
Ex. 6-47	a-CB	HT-3	3-1-3	−814	−118	0.838	−802	−115	0.817	◯
Ex. 6-48	a-CB	HT-3	3-1-12	−809	−104	0.810	−801	−106	0.826	◯
C. Ex. 1-16	a-CB	HT-3	—	−793	−137	0.979	−746	−167	1.193	X
Ex. 6-49	a-CF	HT-3	3-1-3	−814	−118	0.937	−793	−126	1.001	◯
Ex. 6-50	a-CF	HT-3	3-1-12	−812	−119	0.904	−817	−121	0.919	◯
C. Ex. 1-17	a-CF	HT-3	—	−793	−139	1.021	−766	−178	1.307	X
Ex. 6-51	a-BN	HT-3	3-1-3	−788	−100	0.786	−780	−97	0.762	◯
Ex. 6-52	a-BN	HT-3	3-1-12	−804	−95	0.767	−796	−100	0.807	◯
C. Ex. 1-18	a-BN	HT-3	—	−780	−117	0.904	−748	−146	1.128	X

[0566] It was confirmed from the table that if the type of the surface protective layer was further changed, the same results as the above were obtained according to the compositions of the charge transport layer of the multi-layer photosensitive layer as the base.

[0567] According to the results of the solvent resistance test listed in the table, all the electrophotosensitive materials of Examples 6-43 to 6-52 suffered no cracks nor delamination of the surface protective layer. It was thus concluded that the use of the naphthylene diimide derivative of the formula (3) contributed the improvement of the physical stability of the inorganic surface protective layer.

[0568] It was also confirmed that all the electrophotosensitive materials of these examples were free from serious decrease in photosensitivity when formed with the surface protective layer and thus maintained high photosensitivity, because they had small residual potentials after light exposure and half-life exposures.

[0569] In addition, all the electrophotosensitive materials of these examples were free from significant increase in residual potential and half-life exposure after the durability test. Based on this fact and the results of the solvent resistance test, it was concluded that these electrophotosensitive materials achieved greater improvement in durability than the prior-art products.

[0570] Single-layer Electrophotosensitive Material

Examples 7-1 to 7-7

[0571] Electrophotosensitive materials of Examples 7-1 to 7-7 were fabricated the same way as in Example 1-1 except that each of the examples used 40 parts by weight of quinone derivative of the formula of a number listed in Table 37.

Comparative Example 7-1

[0572] An electrophotosensitive material of Comparative Example 7-1 was fabricated the same way as in Examples 7-1 to 7-7 except that 40 parts by weight of isatin compound represented by the formula (ET-1) was used instead of the quinone derivative.

Examples 7-8 to 7-14

[0573] Electrophotosensitive materials of Examples 7-8 to 7-14 were fabricated the same way as in Example 1-7 except that each of the examples used 40 parts by weight of quinone derivative of the formula of a number listed in Table 37.

Comparative Example 7-2

[0574] An electrophotosensitive material of Comparative Example 7-2 was fabricated the same way as in Examples 7-8 to 7-14 except that 40 parts by weight of isatin compound represented by the formula (ET-1) was used instead of the quinone derivative.

[0575] The electrophotosensitive materials of the above examples and comparative examples were subjected to the same photosensitivity test (I), durability test (I) and solvent resistance test as the above and were evaluated for the characteristics thereof. The results as well as those of Comparative Examples 1-1, 1-2 are listed in Table 37.

	TABLE 37
	Initial	After durability test
						HLE			HLE
		P-H		SP	RP	E½	SP	RP	E½
	SPL	TM	QC	V0(V)	Vr(V)	(μJ/cm2)	V0(V)	Vr(V)	(μJ/cm2)	SRT
Ex. 7-1	a-SiC	HT-1	4-1-1	801	193	1.340	793	191	1.326	◯
Ex. 7-2	a-SiC	HT-1	4-1-11	814	185	1.305	807	178	1.276	◯
Ex. 7-3	a-SiC	HT-1	4-2-2	810	188	1.387	805	192	1.406	◯
Ex. 7-4	a-SiC	HT-1	4-2-15	808	194	1.403	814	198	1.422	◯
Ex. 7-5	a-SiC	HT-1	4-3-2	806	164	1.200	798	162	1.185	◯
Ex. 7-6	a-SiC	HT-1	4-3-3	802	176	1.272	798	174	1.258	◯
Ex. 7-7	a-SiC	HT-1	4-3-13	810	180	1.251	812	182	1.265	◯
C. Ex. 1-1	a-SiC	HT-1	—	817	205	1.500	745	244	1.785	X
C. Ex. 7-1	a-SiC	HT-1	ET-1	809	198	1.488	753	226	1.769	X
Ex. 7-8	a-SiC	HT-3	4-1-1	814	216	1.502	817	218	1.516	◯
Ex. 7-9	a-SiC	HT-3	4-1-11	817	210	1.437	806	207	1.416	◯
Ex. 7-10	a-SiC	HT-3	4-2-2	782	224	1.544	780	221	1.523	◯
Ex. 7-11	a-SiC	HT-3	4-2-15	809	219	1.544	801	214	1.519	◯
Ex. 7-12	a-SiC	HT-3	4-3-2	802	184	1.324	809	186	1.338	◯
Ex. 7-13	a-SiC	HT-3	4-3-3	817	205	1.438	802	202	1.417	◯
Ex. 7-14	a-SiC	HT-3	4-3-13	814	195	1.367	804	193	1.353	◯
C. Ex. 1-2	a-SiC	HT-3	—	804	232	1.667	748	252	1.810	Δ
C. Ex. 7-2	a-SiC	HT-3	ET-1	806	212	1.653	755	230	1.754	Δ
QC: Quinone compound

[0576] According to the results of the solvent resistance test listed in the table, the electrophotosensitive material of Comparative Example 7-1 suffered the delamination of the surface protective layer similarly to that of Comparative Example 1-1. Similarly to the electrophotosensitive material of Comparative Example 1-2, that of Comparative Example 7-2 was found to sustain cracks in the surface protective layer. It was thus concluded that adding a compound other than those of the formulas (1) to (4) to the photosensitive layer does not contribute the effect to improve the physical stability of the inorganic surface protective layer.

[0577] Furthermore, the electrophotosensitive materials of these comparative examples were found to have poor durability because they were significantly increased in residual potential and half-life exposure after the durability test.

[0578] In contrast, all the electrophotosensitive materials of Examples 7-1 to 7-14 suffered no cracks nor delamination of the surface protective layer in the solvent resistance test. It was thus concluded that the use of the quinone derivative of the formula (4) contributed the improvement of the physical stability of the inorganic surface protective layer.

[0579] It was also confirmed that all the electrophotosensitive materials of these examples were free from serious decrease in photosensitivity when formed with the surface protective layer and thus maintained high photosensitivity, because they had small residual potentials after light exposure and half-life exposures.

[0580] In addition, all the electrophotosensitive materials of these examples were free from significant increase in residual potential and half-life exposure after the durability test. Based on this fact and the results of the solvent resistance test, it was concluded that these electrophotosensitive materials achieved greater improvement in durability than the prior-art products.

Examples 7-15 to 7-28, Comparative Examples 7-3, 7-4

[0581] Electrophotosensitive materials of Examples 7-15 to 7-28 and Comparative Examples 7-3, 7-4 were fabricated the same way as in Examples 7-1 to 7-14 and Comparative Examples 7-1, 7-2 except that the same procedure as in Examples 1-13 to 1-24 was taken to form a surface protective layer of amorphous carbon (C) having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the single-layer photosensitive layer.

[0582] The electrophotosensitive materials of the above examples and comparative examples were subjected to the same photosensitivity test (I), durability test (I) and solvent resistance test as the above and were evaluated for the characteristics thereof. The results as well as those of Comparative Examples 1-3, 1-4 are listed in Table 38.

	TABLE 38
	Initial	After durability test
						HLE			HLE
		P-H		SP	RP	E½	SP	RP	E½
	SPL	TM	QC	V0(V)	Vr(V)	(μJ/cm2)	V0(V)	Vr(V)	(μJ/cm2)	SRT
Ex. 7-15	a-C	HT-1	4-1-1	814	194	1.421	809	191	1.399	◯
Ex. 7-16	a-C	HT-1	4-1-11	806	190	1.360	803	185	1.344	◯
Ex. 7-17	a-C	HT-1	4-2-2	796	201	1.461	804	204	1.483	◯
Ex. 7-18	a-C	HT-1	4-2-15	790	201	1.475	794	198	1.453	◯
Ex. 7-19	a-C	HT-1	4-3-2	805	163	1.232	814	173	1.259	◯
Ex. 7-20	a-C	HT-1	4-3-3	812	178	1.325	804	176	1.310	◯
Ex. 7-21	a-C	HT-1	4-3-13	796	176	1.292	790	184	1.331	◯
C. Ex. 1-3	a-C	HT-1	—	793	208	1.563	742	238	1.788	X
C. Ex. 7-3	a-C	HT-1	ET-1	801	196	1.433	738	221	1.678	X
Ex. 7-22	a-C	HT-3	4-1-1	802	202	1.502	801	200	1.487	◯
Ex. 7-23	a-C	HT-3	4-1-11	798	198	1.437	790	193	1.401	◯
Ex. 7-24	a-C	HT-3	4-2-2	803	203	1.530	796	208	1.568	◯
Ex. 7-25	a-C	HT-3	4-2-15	805	215	1.544	801	208	1.494	◯
Ex. 7-26	a-C	HT-3	4-3-2	808	177	1.334	798	185	1.394	◯
Ex. 7-27	a-C	HT-3	4-3-3	798	193	1.437	804	191	1.422	◯
Ex. 7-28	a-C	HT-3	4-3-13	795	182	1.356	790	185	1.378	◯
C. Ex. 1-4	a-C	HT-3	—	788	222	1.667	746	240	1.792	X
C. Ex. 7-4	a-C	HT-3	ET-1	812	214	1.601	752	232	1.604	X

[0583] It was confirmed from the table that if the type of the surface protective layer was changed, the same results as the above were obtained according to the compositions of the single-layer photosensitive layer as the base.

[0584] Specifically, both the electrophotosensitive material of Comparative Examples 7-3, 7-4 were found to suffer the delamination of the surface protective layer similarly to those of Comparatives Examples 1-3, 1-4. It was thus concluded that adding a compound other than those of the formulas (1) to (4) to the photosensitive layer does not contribute the effect to improve the physical stability of the inorganic surface protective layer.

[0585] Furthermore, the electrophotosensitive materials of these comparative examples were found to have poor durability because they were significantly increased in residual potential and half-life exposure after the durability test.

[0586] In contrast, all the electrophotosensitive materials of Examples 7-15 to 7-28 suffered no cracks nor delamination of the surface protective layer in the solvent resistance test. It was thus concluded that the use of the quinone derivative of the formula (4) contributed the improvement of the physical stability of the inorganic surface protective layer.

[0587] It was also confirmed that all the electrophotosensitive materials of these examples were free from serious decrease in photosensitivity when formed with the surface protective layer and thus maintained high photosensitivity, because they had small residual potentials after light exposure and half-life exposures.

[0588] In addition, all the electrophotosensitive materials of these examples were free from significant increase in residual potential and half-life exposure after the durability test. Based on this fact and the results of the solvent resistance test, it was concluded that these electrophotosensitive materials achieved greater improvement in durability than the prior-art products.

Examples 7-29 to 7-32, Comparative Example 7-5

[0589] Electrophotosensitive materials of Examples 7-29 to 7-32 and Comparative Example 7-5 were fabricated the same way as in Examples 7-8, 7-10, 7-11 and 7-13 and Comparative Example 7-2 except that the same procedure as in Examples 1-25, 1-26 was taken to form a surface protective layer of amorphous silicon-nitrogen (SiN) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the single-layer photosensitive layer.

Examples 7-33 to 7-36, Comparative Example 7-6

[0590] Electrophotosensitive materials of Examples 7-33 to 7-36 and Comparative Example 7-6 were fabricated the same way as in Examples 7-8, 7-10, 7-11 and 7-13 and Comparative Example 7-2 except that the same procedure as in Examples 1-27, 1-28 was taken to form a surface protective layer of amorphous carbon-nitrogen (CN) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the single-layer photosensitive layer.

Examples 7-37 to 7-40, Comparative Example 7-7

[0591] Electrophotosensitive materials of Examples 7-37 to 7-40 and Comparative Example 7-7 were fabricated the same way as in Examples 7-8, 7-10, 7-11 and 7-13 and Comparative Example 7-2 except that the same procedure as in Examples 1-29, 1-30 was taken to form a surface protective layer of amorphous carbon-boron (CB) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the single-layer photosensitive layer.

Examples 7-41 to 7-44, Comparative Example 7-8

[0592] Electrophotosensitive materials of Examples 7-41 to 7-44 and Comparative Example 7-8 were fabricated the same way as in Examples 7-8, 7-10, 7-11 and 7-13 and Comparative Example 7-2 except that the same procedure as in Examples 1-31, 1-32 was taken to form a surface protective layer of amorphous carbon-fluorine (CF) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the single-layer photosensitive layer.

Examples 7-45 to 7-48, Comparative Example 7-9

[0593] Electrophotosensitive materials of Examples 7-45 to 7-48 and Comparative Example 7-9 were fabricated the same way as in Examples 7-8, 7-10, 7-11 and 7-13 and Comparative Example 7-2 except that the same procedure as in Examples 1-33, 1-34 was taken to form a surface protective layer of amorphous boron-nitrogen (BN) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the single-layer photosensitive layer.

[0594] The electrophotosensitive materials of the above examples and comparative examples were subjected to the same photosensitivity test (I), durability test (I) and solvent resistance test as the above and were evaluated for the characteristics thereof. The results as well as those of Comparative Examples 1-5 to 1-9 are listed in Tables 39a, 39b.

	TABLE 39a
	Initial	After durability test
						HLE			HLE
		P-H		SP	RP	E½	SP	RP	E½
	SPL	TM	QC	V0(V)	Vr(V)	(μJ/cm2)	V0(V)	Vr(V)	(μJ/cm2)	SRT
Ex. 7-29	a-SiN	HT-3	4-1-1	806	227	1.625	795	222	1.589	◯
Ex. 7-30	a-SiN	HT-3	4-2-2	801	236	1.656	809	231	1.621	◯
Ex. 7-31	a-SiN	HT-3	4-2-15	813	203	1.442	806	197	1.399	◯
Ex. 7-32	a-SiN	HT-3	4-3-3	798	207	1.515	803	211	1.544	◯
C. Ex. 1-5	a-SiN	HT-3	—	812	245	1.787	749	263	1.918	Δ
C. Ex. 7-5	a-SiN	HT-3	ET-1	814	240	1.766	753	260	1.897	Δ
Ex. 7-33	a-CN	HT-3	4-1-1	809	229	1.705	804	227	1.690	◯
Ex. 7-34	a-CN	HT-3	4-2-2	793	240	1.737	798	233	1.686	◯
Ex. 7-35	a-CN	HT-3	4-2-15	806	213	1.513	809	208	1.477	◯
Ex. 7-36	a-CN	HT-3	4-3-3	809	216	1.589	800	213	1.567	◯
C. Ex. 1-6	a-CN	HT-3	—	790	252	1.875	752	270	2.009	Δ
C. Ex. 7-6	a-CN	HT-3	ET-1	814	248	1.866	760	268	1.905	X
Ex. 7-37	a-CB	HT-3	4-1-1	801	206	1.516	809	208	1.531	◯
Ex. 7-38	a-CB	HT-3	4-2-2	817	210	1.544	809	208	1.529	◯
Ex. 7-39	a-CB	HT-3	4-2-15	814	179	1.345	806	177	1.330	◯
Ex. 7-40	a-CB	HT-3	4-3-3	812	198	1.413	806	195	1.392	◯
C. Ex. 1-7	a-CB	HT-3	—	801	222	1.667	746	238	1.787	X
C. Ex. 7-7	a-CB	HT-3	ET-1	803	211	1.568	754	234	1.742	X

[0595]

	TABLE 39b
	Initial	After durability test
						HLE			HLE
		P-H		SP	RP	E½	SP	RP	E½
	SPL	TM	QC	V0(V)	Vr(V)	(μJ/cm2)	V0(V)	Vr(V)	(μJ/cm2)	SRT
Ex. 7-41	a-CF	HT-3	4-1-1	798	210	1.586	793	210	1.576	◯
Ex. 7-42	a-CF	HT-3	4-2-2	806	214	1.616	814	216	1.631	◯
Ex. 7-43	a-CF	HT-3	4-2-15	802	194	1.408	792	188	1.364	◯
Ex. 7-44	a-CF	HT-3	4-3-3	804	206	1.479	798	203	1.457	◯
C. Ex. 1-8	a-CF	HT-3	—	788	232	1.745	734	248	1.865	X
C. Ex. 7-8	a-CF	HT-3	ET-1	804	222	1.668	751	235	1.745	X
Ex. 7-45	a-BN	HT-3	4-1-1	804	184	1.451	798	188	1.483	◯
Ex. 7-46	a-BN	HT-3	4-2-2	795	192	1.478	801	190	1.463	◯
Ex. 7-47	a-BN	HT-3	4-2-15	806	163	1.287	801	166	1.311	◯
Ex. 7-48	a-BN	HT-3	4-3-3	806	174	1.352	801	172	1.336	◯
C. Ex. 1-9	a-BN	HT-3	—	785	203	1.595	752	233	1.831	X
C. Ex. 7-9	a-BN	HT-3	ET-1	793	196	1.471	756	228	1.688	X

[0596] It was confirmed from the tables that if the type of the surface protective layer was further changed, the same results as the above were obtained according to the compositions of the single-layer photosensitive layer as the base.

[0597] According to the results of the solvent resistance test listed in the tables, all the electrophotosensitive materials of Comparative Examples 7-6 to 7-9 suffered the delamination of the surface protective layer similarly to those of Comparative Examples 1-7 to 1-9. Similarly to the electrophotosensitive materials of Comparative Examples 1-5 and 1-6, those of Comparative Examples 7-5 was found to sustain cracks in the surface protective layer. It was thus concluded that adding a compound other than those of the formulas (1) to (4) to the photosensitive layer does not contribute the effect to improve the physical stability of the inorganic surface protective layer.

[0598] Furthermore, the electrophotosensitive materials of these comparative examples were found to have poor durability because they were significantly increased in residual potential and half-life exposure after the durability test.

[0599] In contrast, all the electrophotosensitive materials of Examples 7-29 to 7-48 suffered no cracks nor delamination of the surface protective layer in the solvent resistance test. It was thus concluded that the use of the quinone derivative of the formula (4) contributed the improvement of the physical stability of the inorganic surface protective layer.

[0600] It was also confirmed that all the electrophotosensitive materials of these examples were free from serious decrease in photosensitivity when formed with the surface protective layer and thus maintained high photosensitivity, because they had small residual potentials after light exposure and half-life exposures.

[0601] In addition, all the electrophotosensitive materials of these examples were free from significant increase in residual potential and half-life exposure after the durability test. Based on this fact and the results of the solvent resistance test, it was concluded that these electrophotosensitive materials achieved greater improvement in durability than the prior-art products.

[0602] Multi-layer Electrophotosensitive Material

Examples 7-49 to 7-55

[0603] Electrophotosensitive materials of Examples 7-49 to 7-55 were fabricated the same way as in Example 1-35 except that each of the examples used 0.2 parts by weight of quinone derivative of the formula of a number listed in Table 40.

Comparative Example 7-10

[0604] An electrophotosensitive material of Comparative Example 7-10 was fabricated the same way as in Examples 7-49 to 7-55 except that 0.2 parts by weight of isatin compound represented by the formula (ET-1) was used instead of the quinone derivative.

Examples 7-56 to 7-62

[0605] Electrophotosensitive materials of Examples 7-56 to 7-62 were fabricated the same way as in Example 1-41 except that each of the examples used 40 parts by weight of quinone derivative of the formula of a number listed in Table 40.

Comparative Example 7-11

[0606] An electrophotosensitive material of Comparative Example 7-11 was fabricated the same way as in Examples 7-56 to 7-62 except that 0.2 parts by weight of isatin compound represented by the formula (ET-1) was used instead of the quinone derivative.

[0607] The electrophotosensitive materials of the above examples and comparative examples were subjected to the same photosensitivity test (II), durability test (II) and solvent resistance test as the above and were evaluated for the characteristics thereof. The results as well as those of Comparative Examples 1-10, 1-11 are listed in Table 40.

	TABLE 40
	Initial	After durability test
						HLE			HLE
		P—H		SP	RP	E½	SP	RP	E½
	SPL	TM	QC	V0(V)	Vr(V)	(μJ/cm2)	V0(V)	Vr(V)	(μJ/cm2)	SRT
Ex.7-49	a-SiC	HT-1	4-1-1	−804	−153	0.911	−798	−158	0.941	◯
Ex.7-50	a-SiC	HT-1	4-1-11	−796	−148	0.869	−798	−143	0.840	◯
Ex.7-51	a-SiC	HT-1	4-2-2	−806	−146	0.885	−814	−151	0.915	◯
Ex.7-52	a-SiC	HT-1	4-2-15	−785	−150	0.894	−788	−153	0.912	◯
Ex.7-53	a-SiC	HT-1	4-3-2	−812	−159	0.903	−814	−157	0.892	◯
Ex.7-54	a-SiC	HT-1	4-3-3	−806	−161	0.911	−809	−158	0.894	◯
Ex.7-55	a-SiC	HT-1	4-3-13	−798	−157	0.902	−792	−149	0.856	◯
C.Ex.1-10	a-SiC	HT-1	—	−806	−165	0.938	−782	−192	1.052	X
C.Ex.7-10	a-SiC	HT-1	ET-1	−796	−167	1.217	−766	−196	1.307	X
Ex.7-56	a-SiC	HT-3	4-1-1	−804	−136	0.995	−793	−141	1.032	◯
Ex.7-57	a-SiC	HT-3	4-1-11	−809	−134	0.949	−798	−132	0.935	◯
Ex.7-58	a-SiC	HT-3	4-2-2	−800	−132	0.967	−804	−134	0.982	◯
Ex.7-59	a-SiC	HT-3	4-2-15	−809	−130	0.975	−798	−133	0.998	◯
Ex.7-60	a-SiC	HT-3	4-3-2	−804	−134	0.985	−809	−137	1.007	◯
Ex.7-61	a-SiC	HT-3	4-3-3	−782	−141	0.995	−788	−136	0.960	◯
Ex.7-62	a-SiC	HT-3	4-3-13	−812	−139	0.986	−806	−132	0.936	◯
C.Ex.1-11	a-SiC	HT-3	—	−814	−147	1.024	−776	−176	1.226	X
C.Ex.7-11	a-SiC	HT-3	ET-1	−780	−153	1.098	−753	−186	1.289	X

[0608] It was confirmed from the table that if the single-layer photosensitive layer was replaced by the multi-layer photosensitive layer, the same results as the above were obtained according to the compositions of the charge transport layer defining the outermost part thereof.

[0609] Specifically, it was found in the solvent resistance test that both the electrophotosensitive materials of Comparative Examples 7-10, 7-11 suffered the delamination of the surface protective layer similarly to those of Comparative Examples 1-10, 1-11. It was thus concluded that adding a compound other than those of the formulas (1) to (4) to the photosensitive layer does not contribute the effect to improve the physical stability of the inorganic surface protective layer.

[0610] Furthermore, the electrophotosensitive materials of these comparative examples were found to have poor durability because they were significantly increased in residual potential and half-life exposure after the durability test.

[0611] In contrast, all the electrophotosensitive materials of Examples 7-49 to 7-62 suffered no cracks nor delamination of the surface protective layer in the solvent resistance test. It was thus concluded that the use of the quinone derivative of the formula (4) contributed the improvement of the physical stability of the inorganic surface protective layer.

[0612] It was also confirmed that all the electrophotosensitive materials of these examples were free from serious decrease in photosensitivity when formed with the surface protective layer and thus maintained high photosensitivity, because they had small residual potentials after light exposure and half-life exposures.

[0613] In addition, all the electrophotosensitive materials of these examples were free from significant increase in residual potential and half-life exposure after the durability test. Based on this fact and the results of the solvent resistance test, it was concluded that these electrophotosensitive materials achieved greater improvement in durability than the prior-art products.

Examples 7-63 to 7-76, Comparative Examples 7-12, 7

[0614] Electrophotosensitive materials of these examples and comparative examples were fabricated the same way as in Examples 7-49 to 7-62 and Comparative Examples 7-10, 7-11 except that the same procedure as in Examples 1-13 to 1-24 was taken to form a surface protective layer of amorphous carbon (C) having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the multi-layer photosensitive layer.

[0615] The electrophotosensitive materials of the above examples and comparative examples were subjected to the same photosensitivity test (II), durability test (II) and solvent resistance test as the above and were evaluated for the characteristics thereof. The results as well as those of Comparative Examples 1-12, 1-13 are listed in Table 41.

	TABLE 41
	Initial	After durability test
						HLE			HLE
		P—H		SP	RP	E½	SP	RP	E½
	SPL	TM	QC	V0(V)	Vr(V)	(μJ/cm2)	V0(V)	Vr(V)	(μJ/cm2)	SRT
Ex.7-63	a-C	HT-1	4-1-1	−814	−157	1.181	−809	−165	1.241	◯
Ex.7-64	a-C	HT-1	4-1-11	−801	−150	1.126	−806	−157	1.179	◯
Ex.7-65	a-C	HT-1	4-2-2	−795	−155	1.148	−809	−163	1.207	◯
Ex.7-66	a-C	HT-1	4-2-15	−809	−162	1.159	−809	−159	1.138	◯
Ex.7-67	a-C	HT-1	4-3-2	−811	−166	1.170	−817	−161	1.135	◯
Ex.7-68	a-C	HT-1	4-3-3	−801	−165	1.181	−796	−160	1.145	◯
Ex.7-69	a-C	HT-1	4-3-13	−806	−163	1.170	−809	−163	1.175	◯
C.Ex.1-12	a-C	HT-1	—	−785	−172	1.216	−748	−198	1.400	X
C.Ex.7-12	a-C	HT-1	ET-1	−801	−169	1.251	−732	−201	1.422	X
Ex.7-70	a-C	HT-3	4-1-1	−795	−137	1.067	−793	−135	1.051	◯
Ex.7-71	a-C	HT-3	4-1-11	−806	−133	1.017	−803	−130	0.994	◯
Ex.7-72	a-C	HT-3	4-2-2	−817	−133	1.037	−814	−131	1.021	◯
Ex.7-73	a-C	HT-3	4-2-15	−812	−140	1.046	−808	−137	1.024	◯
Ex.7-74	a-C	HT-3	4-3-2	−801	−133	1.056	−793	−131	1.040	◯
Ex.7-75	a-C	HT-3	4-3-3	−805	−140	1.067	−810	−142	1.082	◯
Ex.7-76	a-C	HT-3	4-3-13	−809	−141	1.056	−800	−133	0.996	◯
C.Ex.1-13	a-C	HT-3	—	−817	−146	1.098	−771	−178	1.339	X
C.Ex.7-13	a-C	HT-3	ET-1	−790	−156	1.154	−743	−186	1.403	X

[0616] It was confirmed from the table that if the type of the surface protective layer was changed, the same results as the above were obtained according to the compositions of the charge transport layer of the multi-layer photosensitive layer as the base.

[0617] Specifically, it was found in the solvent resistance test that both the electrophotosensitive materials of Comparative Examples 7-12, 7-13 suffered the delamination of the surface protective layer similarly to those of comparative Examples 1-12, 1-13. It was thus concluded that adding a compound other than those of the formulas (1) to (4) to the photosensitive layer does not contribute the effect to improve the physical stability of the inorganic surface protective layer.

[0618] It was also found that the electrophotosensitive materials of these comparative examples were significantly decreased in photosensitivity when formed with the surface protective layer, because they presented, in the initial stage, large residual potentials after light exposure and large half-life exposures.

[0619] Furthermore, the electrophotosensitive materials of these comparative examples were found to have poor durability because they were significantly increased in residual potential and half-life exposure after the durability test.

[0620] In contrast, all the electrophotosensitive materials of Examples 7-63 to 7-76 suffered no cracks nor delamination of the surface protective layer in the solvent resistance test. It was thus concluded that the use of the quinone derivative of the formula (4) contributed the improvement of the physical stability of the inorganic surface protective layer.

[0621] It was also confirmed that all the electrophotosensitive materials of these examples were free from serious decrease in photosensitivity when formed with the surface protective layer and thus maintained high photosensitivity, because they had small residual potentials after light exposure and half-life exposures.

[0622] In addition, all the electrophotosensitive materials of these examples were free from significant increase in residual potential and half-life exposure after the durability test. Based on this fact and the results of the solvent resistance test, it was concluded that these electrophotosensitive materials achieved greater improvement in durability than the prior-art products.

Examples 7-77 to 7-80, Comparative Example 7-14

[0623] Electrophotosensitive materials of these examples and comparative example were fabricated the same way as in Examples 7-56, 7-58, 7-59 and 7-61 and Comparative Example 7-11 except that the same procedure as in Examples 1-25, 1-26 was taken to form a surface protective layer of amorphous silicon-nitrogen (SiN) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the multi-layer photosensitive layer.

Examples 7-81 to 7-84, Comparative Example 7-15

[0624] Electrophotosensitive materials of these examples and comparative example were fabricated the same way as in Examples 7-56, 7-58, 7-59 and 7-61 and Comparative Example 7-11 except that the same procedure as in Examples 1-27, 1-28 was taken to form a surface protective layer of amorphous carbon-nitrogen (CN) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the multi-layer photosensitive layer.

Examples 7-85 to 7-88, Comparative Example 7-16

[0625] Electrophotosensitive materials of these examples and comparative example were fabricated the same way as in Examples 7-56, 7-58, 7-59 and 7-61 and Comparative Example 7-11 except that the same procedure as in Examples 1-29, 1-30 was taken to form a surface protective layer of amorphous carbon-boron (CB) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the multi-layer photosensitive layer.

Examples 7-89 to 7-92, Comparative Example 7-17

[0626] Electrophotosensitive materials of these examples and comparative example were fabricated the same way as in Examples 7-56, 7-58, 7-59 and 7-61 and Comparative Example 7-11 except that the same procedure as in Examples 1-31, 1-32 was taken to form a surface protective layer of amorphous carbon-fluorine (CF) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the multi-layer photosensitive layer.

Examples 7-93 to 7-96, Comparative Example 7-18

[0627] Electrophotosensitive materials of these examples and comparative example were fabricated the same way as in Examples 7-56, 7-58, 7-59 and 7-61 and Comparative Example 7-11 except that the same procedure as in Examples 1-33, 1-34 was taken to form a surface protective layer of amorphous boron-nitrogen (BN) composite film having a thickness of 0.5 μm, instead of the silicon-carbon composite film, over the surface of the multi-layer photosensitive layer.

[0628] The electrophotosensitive materials of the above examples and comparative example were subjected to the same photosensitivity test (II), durability test (II) and solvent resistance test as the above and were evaluated for the characteristics thereof. The results as well as those of Comparative Examples 1-14 to 1-18 are listed in Tables 42a, 42b.

	TABLE 42a
	Initial	After durability test
						HLE			HLE
		P-H		SP	RP	E1/2	SP	RP	E1/2
	SPL	TM	QC	V0(V)	Vr(V)	(μJ/cm2)	V0(V)	Vr(V)	(μJ/cm2)	SRT
Ex. 7-77	a-SiN	HT-3	4-1-1	−814	−144	1.074	−806	−142	1.059	◯
Ex. 7-78	a-SiN	HT-3	4-2-2	−806	−140	1.063	−798	−143	1.086	◯
Ex. 7-79	a-SiN	HT-3	4-2-15	−798	−139	1.033	−806	−141	1.048	◯
Ex. 7-80	a-SiN	HT-3	4-3-3	−814	−133	1.015	−805	−130	0.992	◯
C. Ex. 1-14	a-SiN	HT-3	—	−785	−149	1.095	−758	−186	1.367	Δ
C. Ex. 7-14	a-SiN	HT-3	ET-1	−801	−160	1.125	−750	−193	1.407	X
Ex. 7-81	a-CN	HT-3	4-1-1	−798	−146	1.133	−804	−142	1.102	◯
Ex. 7-82	a-CN	HT-3	4-2-2	−803	−142	1.122	−809	−144	1.138	◯
Ex. 7-83	a-CN	HT-3	4-2-15	−812	−151	0.886	−804	−146	0.857	◯
Ex. 7-84	a-CN	HT-3	4-3-3	−801	−146	0.869	−809	−151	0.899	◯
C. Ex. 1-15	a-CN	HT-3	—	−793	−148	1.155	−762	−177	1.381	X
C. Ex. 7-15	a-CN	HT-3	ET-1	−817	−156	1.254	−752	−186	1.465	X
Ex. 7-85	a-CB	HT-3	4-1-1	−804	−135	0.960	−798	−133	0.946	◯
Ex. 7-86	a-CB	HT-3	4-2-2	−806	−129	0.951	−803	−124	0.914	◯
Ex. 7-87	a-CB	HT-3	4-2-15	−801	−125	0.924	−795	−120	0.887	◯
Ex. 7-88	a-CB	HT-3	4-3-3	−804	−127	0.907	−810	−122	0.871	◯
C. Ex. 1-16	a-CB	HT-3	—	−793	−137	0.979	−746	−167	1.193	X
C. Ex. 7-16	a-CB	HT-3	ET-1	−812	−130	0.979	−753	−160	1.184	X

[0629]

	TABLE 42b
	Initial	After durability test
						HLE			HLE
		P-H		SP	RP	E1/2	SP	RP	E1/2
	SPL	TM	QC	V0(V)	Vr(V)	(μJ/cm2)	V0(V)	Vr(V)	(μJ/cm2)	SRT
Ex. 7-89	a-CF	HT-3	4-1-1	−809	−129	1.002	−805	−127	0.986	◯
Ex. 7-90	a-CF	HT-3	4-2-2	−782	−133	0.992	−785	−125	0.932	◯
Ex. 7-91	a-CF	HT-3	4-2-15	−801	−129	0.964	−792	−132	0.986	◯
Ex. 7-92	a-CF	HT-3	4-3-3	−808	−119	0.946	−803	−122	0.970	◯
C. Ex. 1-17	a-CF	HT-3	—	−793	−139	1.021	−766	−178	1.307	X
C. Ex. 7-17	a-CF	HT-3	ET-1	−804	−141	1.024	−758	−188	1.394	X
Ex. 7-93	a-BN	HT-3	4-1-1	−804	−108	0.887	−806	−110	0.903	◯
Ex. 7-94	a-BN	HT-3	4-2-2	−817	−109	0.878	−809	−112	0.902	◯
Ex. 7-95	a-BN	HT-3	4-2-15	−793	−111	0.853	−798	−106	0.815	◯
Ex. 7-96	a-BN	HT-3	4-3-3	−803	−109	0.838	−808	−111	0.853	◯
C. Ex. 1-18	a-BN	HT-3	—	−780	−117	0.904	−748	−146	1.128	X
C. Ex. 7-18	a-BN	HT-3	ET-1	−790	−120	0.921	−755	−149	1.195	X

[0630] It was confirmed from the tables that if the type of the surface protective layer was further changed, the same results as the above were obtained according to the compositions of the charge transport layer of the multi-layer photosensitive layer as the base.

[0631] According to the results of the solvent resistance test listed in the tables, all the electrophotosensitive materials of Comparative Examples 7-14 to 7-18 suffered the delamination of the surface protective layer. It was thus concluded that adding a compound 1 other than those of the formulas (1) to (4) to the photosensitive layer does not contribute the effect to improve the physical stability of the inorganic surface protective layer. Some of the electrophotosensitive materials were rather decreased in the stability (Comparative Examples 1-14 and 7-14).

[0632] It was also found that the electrophotosensitive materials of these comparative examples were significantly decreased in photosensitivity when formed with the surface protective layer, because they presented, in the initial stage, large residual potentials after light exposure and large half-life exposures.

[0633] Furthermore, the electrophotosensitive materials of these comparative examples were found to have poor durability because they were significantly increased in residual potential and half-life exposure after the durability test.

[0634] In contrast, all the electrophotosensitive materials of Examples 7-77 to 7-96 suffered no cracks nor delamination of the surface protective layer in the solvent resistance test. It was thus concluded that the use of the quinone derivative of the formula (4) contributed the improvement of the physical stability of the inorganic surface protective layer.

[0635] It was also confirmed that all the electrophotosensitive materials of these examples were free from serious decrease in photosensitivity when formed with the surface protective layer and thus maintained high photosensitivity, because they had small residual potentials after light exposure and half-life exposures.

[0636] In addition, all the electrophotosensitive materials of these examples were free from significant increase in residual potential and half-life exposure after the durability test. Based on this fact and the results of the solvent resistance test, it was concluded that these electrophotosensitive materials achieved greater improvement in durability than the prior-art products.

Claims

1. An electrophotosensitive material comprising an organic photosensitive layer and an inorganic surface protective layer laid over a conductive substrate in this order, wherein at least an outermost part of the organic photosensitive layer that contacts the surface protective layer contains at least one compound selected from the group consisting of a diphenoquinone derivative represented by a formula (1):

2. An electrophotosensitive material according to claim 1, wherein the diphenoquinone derivative represented by the formula (1) includes at least one selected from the group consisting of a diphenoquinone compound represented by a formula (1-1):

3. An electrophotosensitive material according to claim 1, wherein the naphthoquinone derivative represented by the formula (2) includes at least one selected from the group consisting of a naphthoquinone compound represented by a formula (2-1):

4. An electrophotosensitive material according to claim 1, wherein the quinone derivative represented by the formula (4) includes at least one selected from the group consisting of a compound represented by a formula (4-1):

5. An electrophotosensitive material according to claim 1, wherein the surface protective layer is a layer formed by a vapor deposition method.

6. An electrophotosensitive material according to claim 1, wherein the surface protective layer comprises at least one element selected from the group consisting of metallic elements and carbon or an inorganic compound containing any of these elements.

7. An electrophotosensitive material according to claim 1, wherein the organic photosensitive layer is a single-layer photosensitive layer comprising a binder resin containing therein a charge generating material and any one of the compounds represented by the formulas (1) to (4).

8. An electrophotosensitive material according to claim 1, wherein the organic photosensitive layer is a multi-layer photosensitive layer comprising a charge generating layer and a charge transport layer laminated in this order, the charge generating layer containing a charge generating material, the charge transport layer comprising a binder resin containing therein any one of the compounds represented by the formulas (1) to (4).