Patent Grant
8879976
This application is based upon and claims the benefit of priority from provisional U.S. Patent Application 61/419,435 filed on Dec. 3, 2010, the entire contents of which are incorporated herein by reference.
Embodiments described herein relate to an image forming apparatus using a toner which can be decolorized by heating and to an image forming and erasing method using the image forming apparatus.
Conventionally, in order to reduce the amount of CO2 emission by reducing energy required for the recycling of paper and the production of paper by reusing paper, an image forming apparatus using a decolorizable toner which is decolorized by heating for forming an image by a known electrophotographic process and a decolorizing apparatus which heats paper having a decolorizable toner image formed thereon so as to change the image in a colored state to a decolorized state are proposed in the form of separate bodies.
However, in order to decolorize a toner image by a conventional decolorizing apparatus, for example, it was necessary to heat paper at 120 to 150° C. for about 2 hours, and there was a disadvantage that a large amount of electric power was required for erasing an image.
The accompanying drawings, which is incorporated in and constitute a part of this specification, illustrates an embodiment of the invention and together with the description, serve to explain the principles of the invention.
Reference will now be made in detail to the present embodiment of the invention, an example of which is illustrated in the accompanying drawing.
An image forming apparatus according to an embodiment includes: an image erasing section including a first member which has an elastic layer and heats a recording medium having a thermally decolorizable toner image on the toner image side and a second member which forms a nip together with the first member and erases the toner image by allowing the recording medium to pass through the nip in cooperation with the first member; an image forming section which transfers a thermally decolorizable toner image onto the recording medium on which the toner image is erased to form an unfixed toner image; and an image fixing section including a third member which does not have an elastic layer and heats the recording medium on the unfixed toner image side and a fourth member which forms a nip together with the third member and fixes the unfixed toner image by allowing the recording medium to pass through the nip in cooperation with the third member.
Further, an image forming and erasing method according to an embodiment includes: allowing a recording medium having a thermally decolorizable toner image to pass through a nip formed by a first member which has an elastic layer and heats the recording medium on the toner image side and a second member which is in press-contact with the first member to erase the toner image; transferring a thermally decolorizable toner image onto the recording medium on which the toner image is erased to form an unfixed toner image; and allowing the recording medium to pass through a nip formed by a third member which does not have an elastic layer and heats the recording medium on the unfixed toner image side and a fourth member which is in press-contact with the third member to fix the unfixed toner image.
Further, an image forming apparatus according to an embodiment includes: an image forming section which transfers a thermally decolorizable toner image onto a recording medium to form an unfixed toner image; and an image fixing section including a third member which does not have an elastic layer and heats the recording medium on the unfixed toner image side and a fourth member which forms a nip together with the third member and fixes the unfixed toner image by allowing the recording medium to pass through the nip in cooperation with the third member.
Hereinafter, the embodiment will be described with reference to the accompanying drawings. Incidentally, when the same reference numeral is used in the following description, it means that elements assigned with the same reference numeral have the same structure and function.
The scanner 4 includes, for example, a carriage 6 having a light source 5 which irradiates light to the original document table 2, reflecting mirrors 7a, 7b, and 7c which reflect the light of the light source 5 reflected from the original document, a variable magnification lens block 8 which magnifies the reflected light, and a CCD (charge coupled device) 9. The carriage 6 is reciprocatably provided along the lower surface of the original document table 2.
The carriage 6 moves forth while lighting the light source 5, so that the original document placed on the original document table 2 is exposed to light. The reflected light image of the original document by this light exposure is projected onto the CCD 9 via the reflecting mirrors 7a, 7b, and 7c and the variable magnification lens block 8.
The CCD 9 outputs a digitalized image signal corresponding to the projected reflected light image of the original document to an image processing circuit. This image signal is properly processed by the image processing circuit, and is then output to a laser unit 11 of an image forming section 10. The image forming section 10 executes an image forming process in which a toner image in accordance with the image signal output from the CCD 9 is formed on a recording medium P such as paper.
The image forming section 10 includes an image carrying member 12 having an organic photoconductor (OPC) on a surface thereof, a corona charger 13 for uniformly charging the surface of the image carrying member 12, the laser unit 11 for forming an electrostatic latent image on the image carrying member 12, a developing device 14 provided with a developing roller which supplies a developer to the electrostatic latent image on the image carrying member 12 and achieves development, a transferring roller 15, a cleaner 16 for removing and collecting a transfer residual toner or the like, and a charge eliminating lamp 17 for eliminating a charge from the surface of the image carrying member 12 after transfer.
The image carrying member 12 has an organic photoconductor (OPC) on a surface thereof and rotates at a peripheral speed of 136 mm/sec (the arrow O in
The corona charger 13 is a scorotron corona charger and uniformly and negatively charges the image carrying member 12. The uniformly charged image carrying member 12 is subjected to scanning exposure to laser light 11a at a resolution of 600 dpi by a laser (semiconductor laser) mounted on the laser unit 11 in accordance with an image signal obtained by the scanner 4, and an electrostatic latent image is formed on the image carrying member 12.
The developing device 14 accommodates, for example, a two-component developer, which is composed of a mixture of decolorizable toner having a volume average particle diameter of from 5 to 12 μm and a magnetic carrier having a volume average particle diameter of from 30 to 80 μm and in which the decolorizable toner is negatively charged, and develops the electrostatic latent image on the image carrying member 12 to form a toner image. Incidentally, the developing device 14 is provided with a toner density sensor for detecting the density of the toner in the developer accommodated therein and the decolorizable toner is supplied from a toner cartridge to the developing device 14 in accordance with the detection output of the toner density sensor.
The transferring roller 15 is a conductive roller and a positive transfer bias is applied thereto by a high voltage power source. By the transferring roller to which the transfer bias is applied, the toner image formed on the image carrying member 12 is transferred onto a recording medium P which is fed from a paper feeding section 32, 33, or 34 and conveyed at a predetermined timing by a resist roller pair 18. The toner image transferred onto the recording medium P is fixed by the below-described image fixing section 40, and then the recording medium P is discharged to the outside of the apparatus by a paper discharging roller pair 31.
The cleaner 16 has a cleaning blade 16a which is in contact with the surface of the image carrying member 12 and scrapes off the toner remaining on the image carrying member 12 after transfer with the cleaning blade 16a. The charge eliminating lamp 17 eliminates a charge remaining on the surface of the image carrying member 12. The image carrying member 12 from which a charge is eliminated is used for forming the subsequent electrostatic latent image.
As the paper feeding section having a cassette, a paper feeding section 32 which accommodates unused paper P1 and a paper feeding section 33 which accommodates paper for reuse (paper having a fixed toner image) P2 are provided. Further, a manual paper feeding section 34 which feeds paper from the outside of the apparatus is provided. The apparatus is configured such that the selection of the paper feeding section can be performed from an operation panel, and paper is fed from the paper feeding section 32 or 33 by a pick-up roller 321 or 331 and a separating and conveying roller pair 35 or 36. Further, paper is fed from the manual paper feeding section 34 by a pick-up roller 341.
After a fixed toner image on the paper for reuse P2 fed from the paper feeding section 33 is erased by the below-described image erasing section 20, the paper for reuse P2 is conveyed to the image forming section 10 by a conveying roller pair 39 and the resist roller pair 18 and is used in the above-described image formation. Incidentally, although not shown for convenience in the image forming apparatus 1 according to this embodiment, a known both sides conveying section is provided.
(Image Erasing Section 20)
The image erasing section 20 has a heating member composed of, as a first member which heats the paper for reuse P2 on the side where the toner image is formed (hereinafter also referred to as “on the image side”), a first heating roller 21 which has a diameter of 40 mm and has a halogen lamp 23 as a heating source in the inner side thereof, and as a second member which heats the paper for reuse P2 on the side opposite to the side where the toner image is formed (hereinafter also referred to as “on the pressing side”), a second heating roller 22 which has a diameter of 40 mm and has a halogen lamp 24 as a heating source in the same manner as the first heating roller 21 and is in press-contact with the first heating roller 21. A nip formed by the first heating roller 21 and the second heating roller 22 has a width of about 10.8 mm, and a nip passing time in the image erasing section 20 is about 0.08 sec.
The first heating roller 21 and the second heating roller 22 are provided with temperature sensors (thermistors) 30a and 30b, respectively, which measure the surface temperatures of the respective rollers. The temperature sensors 30a and 30b each output the detected information to a temperature controlling section 300. Based on the input information, the temperature controlling section 300 controls a current supplied to the halogen lamps 23 and 24 each serving as a heating source, and controls the surface temperatures of the first heating roller 21 and the second heating roller 22 to be a predetermined temperature (
(Image Fixing Section 40)
The image fixing section 40 has, as a third member which heats the recording medium P on the side where an unfixed toner image is formed, a heating roller 42 which has a diameter of 45 mm and has a halogen lamp 41 as a heating source in the inner side thereof, as a fourth member which is in press-contact with the heating roller 42 and heats the recording medium P on the side opposite to the side where the toner image is formed, an endless pressing belt 43 which has a diameter of 47 mm and forms a nip such that the nip is wound around the heating roller 42, a belt heating roller 45 which has a diameter of 40 mm, has a halogen lamp 44 as a heating source in the inner side thereof, and heats the pressing belt 43 on the side of the entrance of the nip, a pressing roller 46 which has a diameter of 18 mm and presses the heating roller 42 via the pressing belt 43 on the side of the exit of the nip, a tension roller 47, and a pressing pad 49 which has a width of 10 mm and presses the heating roller 42 via the pressing belt 43 in a central part of the nip and is fixed by a pad holder 48. The nip formed by the heating roller 42 and the pressing belt 43 has a width of about 27 mm, and a nip passing time in the image fixing section 40 is about 0.2 sec.
Similar to the image erasing section 20, the heating roller 42 and the pressing belt 43 are provided with temperature sensors (thermistors) 30c and 30d, respectively, which measure the surface temperatures of the respective members. The temperature sensors 30c and 30d each output the detected information to a temperature controlling section 300. Based on the input information, the temperature controlling section 300 controls a current supplied to the halogen lamps 41 and 44 each serving as a heating source, and controls the surface temperatures of the heating roller 42 and the pressing belt 43 to be a predetermined temperature (
The forms of the heating members of the image erasing section 20 and the image fixing section 40 in the image forming apparatus 1 according to this embodiment can be changed within a range that does not deviate from this embodiment. For example, in the case of the image erasing section 20, other than the combination of a roller with a roller as the combination of the first member with the second member described in the above embodiment, a combination of a belt with a roller, a belt with a belt, a roller with a belt, etc., can be adopted, and also in the case of the image fixing section 40, other than the combination of a roller with a belt as the combination of the third member (on the image fixing side) with the fourth member (on the pressing side) described in the above embodiment, a combination of a belt with a roller, a belt with a belt, a roller with a roller, etc. can be adopted.
In addition, other than the case where the image erasing section 20 to be provided in the image forming apparatus 1 is disposed between the paper feeding section 32 or 33 and the image forming section 10 in the paper conveying path described in this embodiment, the image forming apparatus may be configured such that the apparatus has an operation mode for performing only a decolorizing operation, and by designating the decolorizing operation mode, decolorization is performed by the image erasing section 20 and the paper having been subjected to decolorization is accommodated in a paper feed cassette.
Further, as shown in
Hereinafter, the image forming apparatus according to this embodiment will be more specifically described by showing Examples. Incidentally, in the following description, “part (s)” and “%” are on a mass basis unless otherwise specified.
(Preparation of Decolorizable Toner)
As a decolorizable toner to be used in the evaluation for fixing property and decolorizing property, a capsule-type thermally decolorizable toner prepared by the following chemical method was used.
[1] Preparation of Finely Pulverized Binder Resin Liquid
As a binder resin, a Pes (polyester) resin having a glass transition point (Tg) of 50° C. and a softening point (Ts) of 100° C. was used. A finely pulverized binder resin liquid was prepared with a high-pressure homogenizer using 30 parts of the Pes resin, 3 parts of an anionic emulsifying agent (Neopelex G-15 manufactured by Kao Corporation), and 0.6 parts of a neutralizing agent (dimethylaminoethanol).
[2] Preparation of Finely Pulverized Wax Liquid
A finely pulverized wax liquid was prepared using 30 parts of rice wax in the same manner as in the case of the above binder resin.
[3] Preparation of Encapsulated Color Material
1 part of 3-(2-ethoxy-4-diethylaminophenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide as a leuco dye, 5 parts of 2,2-bis(4-hydroxyphenyl) hexafluoropropane as a color developing agent, and 50 parts of a diester compound of pimelic acid with 2-(4-benzyloxyphenyl)ethanol as a temperature control agent were mixed and dissolved by heating.
In the components dissolved by heating, 20 parts of an aromatic polyvalent isocyanate prepolymer and 40 parts of ethyl acetate were mixed as encapsulating agents. The resulting mixed solution was poured into 250 parts of an aqueous solution of 8% polyvinyl alcohol, and the resulting mixture was emulsified and dispersed. After stirring was continued at 70° C. for about 1 hour, 2 parts of a water-soluble aliphatic modified amine was added thereto as a reaction agent, and stirring was further continued for about 3 hours while maintaining the temperature of the liquid at 90° C., whereby colorless encapsulated color material was obtained.
Further, the resulting encapsulated color material was placed in a freezer (−30° C.) to develop a color, whereby a blue color material was obtained. The volume average particle diameter of this color material was measured using SALD-7000 manufactured by Shimadzu Corporation and found to be 2 μm. The thus obtained color material has a property that the decolorization is initiated at 85° C. and the color is completely erased at 95° C.
[4] Preparation of Toner
283 parts of the finely pulverized binder resin liquid prepared in the above [1], 17 parts of the finely pulverized wax liquid prepared in the above [2], and 10 parts of the encapsulated color material prepared in the above [3] were aggregated at 45° C. using 100 parts of an aqueous solution of 5% aluminum sulfate [Al2(SO4)3]. Then, the temperature of the mixture was raised to 65° C. at a temperature raising speed of 1° C./min to fuse the aggregated particles, followed by washing and drying, whereby a toner was obtained. The amount of the encapsulated color material in the thus obtained toner was 10%.
To the obtained toner, an external additive was added appropriately. The resulting toner is hereinafter referred to as a capsule-type decolorizable toner A. Incidentally, the true specific gravity of the capsule-type decolorizable toner A is in a range of from about 0.9 to 1.2 g/cm3. Further, as for the decolorizing property of the capsule-type decolorizable toner A, since the above-prepared color material is used, the decolorization is initiated at 85° C. and the color is completely erased at 95° C.
(Evaluation of Fixing Property)
The fixing property was evaluated using the capsule-type decolorizable toner A prepared by the above method.
First, in the image forming apparatus 1, an image forming operation was performed and an unfixed toner image was formed on unused paper P1. Then, the formed unfixed toner image was fixed by operating the image fixing section 40.
As shown in
It is necessary that the temperatures of the third member and the fourth member of the image fixing section 40 should be controlled to be in a temperature range in which a toner image can be fixed without decolorizing the image, that is, between the lower limit fixing temperature and the decolorization initiation temperature (including a variation depending on location).
As shown in
Subsequently, by using the above-described fixing method, the fixing property of an unfixed toner image was evaluated for the presence or absence of an elastic layer in each of the heating roller 42 and the pressing belt 43. The combination of the presence or absence of an elastic layer is shown in Table 1.
The fixing property was evaluated for four combinations as shown in Table 1: the case where an elastic layer was not provided between the base body and the release layer for both of the heating roller 42 and the pressing belt 43 (Example 1), the case where an elastic layer was provided only for the pressing belt 43 (Example 2), the case where an elastic layer was provided only for the heating roller 42 (Example 3), and the case where an elastic layer was provided for both of the heating roller 42 and the pressing belt 43 (Example 4). Incidentally, in the case of the heating roller 42, the elastic layer provided was made of silicone rubber having a thickness of 0.8 mm, and in the case of the pressing belt 43, the elastic layer provided was made of silicone rubber having a thickness of 0.2 mm. The evaluation results are shown in
As shown in
<Evaluation of Decolorizing Property>
The decolorizing property when decolorization was performed by the image erasing section 20 was evaluated using paper P2 having a fixed toner image obtained by the image fixing section 40.
First, the decolorizing property of a fixed toner image was evaluated for a combination of the presence or absence of an elastic layer in each of the first heating roller 21 (first member) and the second heating roller 22 (second member) of the image erasing section 20 using paper P2 having a fixed toner image by operating the image erasing section 20 in which the heating roller on the image side served as the first heating roller 21. The combination of the presence or absence of an elastic layer is shown in Table 2.
The decolorizing property was evaluated for four combinations as shown in Table 2: the case where an elastic layer was not provided for both of the first heating roller 21 and the second heating roller 22 (Example 5), the case where an elastic layer was provided only for the second heating roller 22 (Example 6), the case where an elastic layer was provided only for the first heating roller 21 (Example 7), and the case where an elastic layer was provided for both of the first heating roller 21 and the second heating roller 22 (Example 8). The elastic layers provided for the first heating roller 21 and the second heating roller 22 were each made of silicone rubber having a thickness of 1.2 mm. The evaluation results are shown in
As described above, in the image erasing section 20, it is important that a difference between the temperature at which decolorization is actually initiated (γ′) and the high-temperature offset initiation temperature (β) of a fixed image be as large as possible. As shown in
Subsequently, the decolorizing property of a fixed toner image was evaluated for a combination of the presence or absence of an elastic layer in each of the first heating roller 21 and the second heating roller 22 of the image erasing section 20 using paper P2 having a fixed toner image by operating only the image erasing section 20 in which the heating roller on the image side served as the second heating roller 22. The combination of the presence or absence of an elastic layer is shown in Table 3.
The decolorizing property was evaluated for four combinations as shown in Table 3: the case where an elastic layer was not provided for both of the first heating roller 21 and the second heating roller 22 (Example 9), the case where an elastic layer was provided only for the second heating roller 22 (Example 10), the case where an elastic layer was provided only for the first heating roller 21 (Example 11), and the case where an elastic layer was provided for both of the first heating roller 21 and the second heating roller 22 (Example 12). The elastic layers provided for the first heating roller 21 and the second heating roller 22 were each made of silicone rubber having a thickness of 1.2 mm. The evaluation results are shown in
As shown in
As shown in
Subsequently, the image erasing section 20 in which the thicknesses of the elastic layers in the first heating roller 21 and the second heating roller 22 of the image erasing section 20 were changed was operated to decolorize a fixed toner image, and evaluation was performed for the decolorization initiation temperature and the high-temperature offset initiation temperature with respect to the thickness of the elastic layer. The evaluation results are shown in
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions the accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
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