Patent Application
20210302900
The present disclosure relates to an electrophotographic image-forming apparatus, such as a laser printer, a copying machine, or a facsimile machine.
In an electrophotographic color-image-forming apparatus, an intermediate transfer system has been known in which a toner image is successively transferred from an image-forming portion of each color to an intermediate transfer member, and the toner images are entirely transferred from the intermediate transfer member to a transfer material.
In such an image-forming apparatus, the image-forming portion of each color has a drum-shaped photosensitive member (hereinafter referred to as a photosensitive drum) as an image-bearing member. The intermediate transfer member is typically an intermediate transfer belt formed of an endless belt. A toner image formed on the photosensitive drum of each image-forming portion is primarily transferred to an intermediate transfer belt by applying a voltage from a primary transfer power supply to a primary transfer member facing the photosensitive drum with the intermediate transfer belt interposed therebetween. The color toner images primarily transferred from the image-forming portion of each color to the intermediate transfer belt are entirely secondarily transferred from the intermediate transfer belt to a transfer material, such as a paper or OHP sheet, by applying a voltage from a secondary transfer power supply to a secondary transfer member in a secondary transfer portion. The color toner images transferred to the transfer material are then fixed to the transfer material by fixing means.
In an image-forming apparatus of the intermediate transfer system, toner remains on an intermediate transfer belt (untransferred toner) after toner images are secondarily transferred from the intermediate transfer belt to a transfer material. Thus, the untransferred toner remaining on the intermediate transfer belt must be removed before a toner image corresponding to another image is primarily transferred to the intermediate transfer belt.
Untransferred toner is typically removed by a blade cleaning system. In the blade cleaning system, untransferred toner is scraped off with a cleaning blade and is collected in a cleaner case. The cleaning blade is located downstream of the secondary transfer portion in the movement direction of the intermediate transfer belt and abuts as a contact member against the intermediate transfer belt. The cleaning blade is typically made of an elastomer, such as a urethane rubber. The cleaning blade is often arranged such that an edge of the cleaning blade is pressed against the intermediate transfer belt in a direction (counter direction) opposite to the movement direction of the intermediate transfer belt.
Japanese Patent Laid-Open No. 2015-125187 (Patent Literature 1) discloses that grooves are formed on the surface of an intermediate transfer belt along the movement direction of the intermediate transfer belt to reduce the abrasion of a cleaning blade. The contact area between the cleaning blade and the intermediate transfer belt is decreased to reduce the friction coefficient between the cleaning blade and the intermediate transfer belt and to reduce the abrasion of the cleaning blade.
Although the durability of the cleaning blade can be improved in Patent Literature 1, to use an image-forming apparatus for longer periods, there is a demand for a cleaning blade with improved durability.
In a configuration in which residual toner on a belt is collected by a contact member that abuts against the belt, the present disclosure improves the durability of the contact member.
An image-forming apparatus according to the present disclosure includes
an image-bearing member configured to bear a toner image,
a developing device, which includes a storage portion configured to accommodate toner and a developing member configured to develop a latent image formed on the image-bearing member with the toner,
a movable endless belt facing the image-bearing member, and
a collecting device, which includes a cleaning blade configured to abut against the belt, and which is configured to collect residual toner on the belt by the cleaning blade,
wherein a ten-point average roughness of an outer peripheral surface of the belt against which the cleaning blade abuts is 0.05 μm or more,
the toner accommodated in the developing device contains toner base particles and an organosilicon polymer on a surface of the toner base particles, and
the cleaning blade has a coating layer on its surface facing the belt after the residual toner on the belt is collected by the cleaning blade into the collecting device, the coating layer containing the organosilicon polymer transferred from the surface of the toner base particles.
Further features of the present disclosure will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Exemplary embodiments of the present disclosure are described below with reference to the accompanying drawings. The dimensions, materials, shapes, and relative arrangement of the components described in these exemplary embodiments should be appropriately changed according to the configuration of the apparatus to which the present disclosure is applied and other conditions, and the scope of the present disclosure is not limited to these embodiments.
The first image-forming portion Sa includes a photosensitive drum 1a, which is a drum-shaped photosensitive member, a charging roller 2a, which is a charging member, a developing device 4a, and a drum cleaning member 5a.
The photosensitive drum 1a is an image-bearing member configured to bear a toner image and is rotationally driven at a predetermined process speed (200 mm/s in the present exemplary embodiment) in the direction of the arrow R1 illustrated in the drawing. The developing device 4a includes a developing container 41a (storage portion) configured to accommodate a yellow toner, and a development roller 42a, which is a developing member configured to bear the yellow toner accommodated in the developing container 41a and to develop a yellow toner image on the photosensitive drum 1a. The drum cleaning member 5a is a member for collecting toner on the photosensitive drum 1a. The drum cleaning member 5a includes a cleaning blade, which comes into contact with the photosensitive drum 1a, and a waste toner box configured to accommodate toner removed from the photosensitive drum 1a by the cleaning blade.
When a controller (not shown) receives an image signal and starts image-forming operation, the photosensitive drum 1a is rotationally driven. In the rotation process, the photosensitive drum 1a is uniformly charged to a predetermined electric potential (charging potential) with a predetermined polarity (negative polarity in the present exemplary embodiment) by the charging roller 2a and is exposed to light emitted from an exposure device 3a in accordance with an image signal. This forms an electrostatic latent image corresponding to a yellow component image of a target color image. The electrostatic latent image is then developed by the developing device 4a at the development position and is visualized as a yellow toner image (hereinafter referred to simply as a toner image). The normal charge polarity of the toner accommodated in the developing device 4a is negative polarity. In the present exemplary embodiment, the electrostatic latent image is reverse-developed with toner charged with the same polarity as the charge polarity of the photosensitive drum by the charging member. The present disclosure, however, can also be applied to an image-forming apparatus in which an electrostatic latent image is positively developed with toner charged with polarity opposite to the charge polarity of the photosensitive drum.
An intermediate transfer belt 10, which is an endless movable intermediate transfer member, abuts against the photosensitive drums 1a to 1d of the image-forming portions Sa to Sd and is stretched by three shafts of a support roller 11, a stretching roller 12, and an opposed roller 13, which are stretching members. The intermediate transfer belt 10 is stretched at a tension of 60 N by the stretching roller 12 and is moved in the direction of the arrow R2 in the drawing as the opposed roller 13 is rotated by a driving force. The intermediate transfer belt 10 in the present exemplary embodiment is composed of a plurality of layers and is described in detail later.
While passing through a primary transfer portion N1a where the photosensitive drum 1a comes into contact with the intermediate transfer belt 10, a toner image formed on the photosensitive drum 1a is primarily transferred to the intermediate transfer belt 10 by applying a positive voltage from a primary transfer power supply 23 to a primary transfer roller 6a. Subsequently, residual toner on the photosensitive drum 1a, which is not primarily transferred to the intermediate transfer belt 10, is collected by the drum cleaning member 5a and is removed from the surface of the photosensitive drum 1a.
The primary transfer roller 6a is a primary transfer member (contact member) facing the photosensitive drum 1a via the intermediate transfer belt 10 and is in contact with the inner peripheral surface of the intermediate transfer belt 10. The primary transfer power supply 23 is a power supply that can apply a positive or negative voltage to primary transfer rollers 6a to 6d. In the present exemplary embodiment, a voltage is applied from the common primary transfer power supply 23 to a plurality of primary transfer members. The present disclosure, however, is not limited to the present exemplary embodiment and can also be applied to a configuration in which a primary transfer power supply is provided for each primary transfer member.
In the same manner, a second magenta toner image, a third cyan toner image, and a fourth black toner image are formed and are successively transferred to the intermediate transfer belt 10. Thus, four color toner images corresponding to the target color image are formed on the intermediate transfer belt 10. While passing through the secondary transfer portion in which a secondary transfer roller 20 comes into contact with the intermediate transfer belt 10, the four color toner images on the intermediate transfer belt 10 are entirely secondarily transferred to the surface of the transfer material P, such as a paper or OHP sheet, fed by the sheet feeder 50.
The secondary transfer roller 20 (secondary transfer member) is a nickel-plated steel bar 8 mm in outer diameter covered with a foam sponge with a volume resistivity of 108 Ω·cm and a thickness of 5 mm composed mainly of NBR and epichlorohydrin rubber and has an outer diameter of 18 mm. The foam sponge had a rubber hardness of 30° at a load of 500 g as measured with an Asker durometer type C. The secondary transfer roller 20 is in contact with the outer peripheral surface of the intermediate transfer belt 10, is pressed at a pressure of 50 N against the opposed roller 13 facing the secondary transfer roller 20 via the intermediate transfer belt 10, and constitutes a secondary transfer portion N2.
The secondary transfer roller 20 is driven to rotate with the intermediate transfer belt 10. When a voltage is applied by a secondary transfer power supply 21, an electric current flows from the secondary transfer roller 20 toward the opposed roller 13. Thus, the toner image on the intermediate transfer belt 10 is secondarily transferred to the transfer material P in the secondary transfer portion. When the toner image on the intermediate transfer belt 10 is secondarily transferred to the transfer material P, the voltage applied from the secondary transfer power supply 21 to the secondary transfer roller 20 is controlled such that a constant electric current flows from the secondary transfer roller 20 to the opposed roller 13 via the intermediate transfer belt 10. The electric current for the secondary transfer is determined in advance according to the environment surrounding the image-forming apparatus 100 and the type of the transfer material P. The secondary transfer power supply 21 is coupled to the secondary transfer roller 20 and applies a transfer voltage to the secondary transfer roller 20. The secondary transfer power supply 21 can output a voltage in the range of 100 to 4000 V.
The transfer material P to which the four color toner images have been transferred in the secondary transfer is then heated and pressed by a fixing device 30, and the four color toners are melted, mixed, and fixed to the transfer material P. Residual toner (untransferred toner) on the intermediate transfer belt 10 after the secondary transfer is cleaned and removed by a belt cleaning device 16 (collecting device) located downstream of the secondary transfer portion N2 in the movement direction of the intermediate transfer belt 10 (hereinafter referred to as a belt conveying direction). The belt cleaning device 16 includes a cleaning blade 16a (contact member), which can abut against the outer peripheral surface of the intermediate transfer belt 10 at a position facing the opposed roller 13, and a cleaner case 16b configured to accommodate toner collected by the cleaning blade 16a. In the following description, the cleaning blade 16a is simply referred to as the blade 16a.
The image-forming apparatus 100 according to the present exemplary embodiment forms a full-color print image through the above operation.
The base layer 82 of the intermediate transfer (endless) belt 10 has a thickness of 80 μm and is formed of poly(ethylene naphthalate) (PEN) resin mixed with an ion conductive agent serving as a conductive agent. The base layer 82 is ion conductive and electroconductive due to ion transfer between polymer chains. Thus, although the resistance value of the base layer 82 fluctuates with the temperature and humidity of the atmosphere, the resistance value is highly uniform in the circumferential direction. In the present exemplary embodiment, the base layer 82 had a volume resistivity of 1×108 Ω·cm or less. The volume resistivity was measured with Hiresta-UP (MCP-HT450) manufactured by Mitsubishi Chemical Corporation equipped with a ring probe type UR (model MCP-HTP12). The volume resistivity was measured at room temperature (23° C.), at a humidity of 50%, and at an applied voltage of 100 V for 10 seconds.
The surface layer 81 of the intermediate transfer belt 10 is formed of an acrylic resin and is formed on the outer peripheral surface of the intermediate transfer belt 10 by applying the acrylic resin to the base layer 82. In the present exemplary embodiment, the surface layer 81 has a thickness of 3 μm.
The surface layer 81 relates to the surface roughness of the intermediate transfer belt 10, as described later, and can therefore be uniformly formed on the surface of the base layer 82 to improve smoothness. More specifically, the acrylic resin may be applied to the entire surface of the base layer 82 by spray coating for a certain period or may be applied from a ring-shaped nozzle to the entire surface of the base layer 82 of the cylindrical intermediate transfer belt 10. In the present exemplary embodiment, the surface layer 81 was formed by spraying a curable resin over the surface of the base layer 82 and irradiating the curable resin with an energy beam, such as ultraviolet light.
The structure of the belt cleaning device 16 is described below.
The belt cleaning device 16 includes the cleaner case 16b and the blade 16a in the cleaner case 16b. The cleaner case 16b constitutes a housing of an intermediate transfer unit (not shown) including the intermediate transfer belt 10. The blade 16a has an elastic portion a1, which abuts against the intermediate transfer belt 10, and a supporting member a2 for supporting the elastic portion a1. The elastic portion a1 is made of a urethane rubber (polyurethane), which is an elastic material, and is bonded to and supported by the supporting member a2 formed of a sheet metal made of a plated steel sheet.
The blade 16a is a plate-like member that is long in the width direction of the intermediate transfer belt 10 (the longitudinal direction of the blade 16a) crossing the belt conveying direction. The elastic portion a1 in the transverse direction has a free end 31b, which abuts against the intermediate transfer belt 10, and a fixed end 31a, which is bonded and fixed to the supporting member a2. The elastic portion a1 has a longitudinal length of 245 mm, a thickness of 2.5 mm, and a hardness of 77 according to JIS K 6253 standard.
The blade 16a is pivotable with respect to the surface of the intermediate transfer belt 10. More specifically, the supporting member a2 is pivotably supported with respect to the surface of the intermediate transfer belt 10 via a pivotal shaft 35 fixed to the cleaner case 16b. When the supporting member a2 is pressed by a pressurizing spring 16c serving as an urging member provided in the cleaner case 16b, the blade 16a rotates on the pivotal shaft 35. Consequently, the free end 31b of the blade 16a is urged (pressed) against the intermediate transfer belt 10.
Facing the blade 16a, the opposed roller 13 is located on the inner peripheral side of the intermediate transfer belt 10. The blade 16a abuts against the surface of the intermediate transfer belt 10 in a direction opposite to the belt conveying direction at a position facing the opposed roller 13. Thus, the blade 16a abuts against the surface of the intermediate transfer belt 10 such that the free end 31b in the transverse direction faces upstream in the belt conveying direction. Thus, as illustrated in
In the present exemplary embodiment, the blade 16a is mounted as described below. As illustrated in
Urethane rubbers and synthetic resins generally have high frictional resistance while sliding, and the blade 16a is likely to curl initially. Thus, an initial lubricant, such as graphite fluoride, may be applied to the free end 31b of the blade 16a in advance.
The rubber hardness of the blade 16a is appropriately determined for the material of the intermediate transfer belt 10 and is preferably 70 or more and 80 or less according to JIS K 6253 standard. A rubber hardness lower than this range may result in an increased abrasion loss during use and lower durability. A rubber hardness higher than the range may result in decreased elastic force and chipping due to friction with the intermediate transfer belt 10. The rubber hardness of the blade 16a is appropriately determined for the material of the intermediate transfer belt 10.
The toner used in the present exemplary embodiment is described below.
The toner in the present exemplary embodiment has protrusions containing an organosilicon polymer on the surface of toner particles. The protrusions are in surface contact with the surface of toner base particles. The surface contact can be rightly expected to suppress the movement, separation, and burying of the protrusions. A cross-sectional observation of the toner was performed with a scanning transmission electron microscope (STEM) to determine the degree of surface contact.
A STEM image 130 in
A cross-sectional image of toner is observed, and a line is drawn along the circumference of the surface of a toner base particle. The cross-sectional image is converted into a horizontal image on the basis of the line along the circumference. In the horizontal image, the length of a line along the circumference in a portion where a protrusion and the toner base particle form a continuous interface is defined as a protrusion width w. The maximum length of the protrusion normal to the protrusion width w is defined as a protrusion diameter d. The length from the top of the protrusion in the line segment forming the protrusion diameter d to the line along the circumference is defined as a protrusion height h.
The protrusion e illustrated in
In
It has been found under the above conditions that an organosilicon compound protrusion with the ratio d/w of the protrusion diameter d to the protrusion width w being 0.33 or more and 0.80 or less is rarely moved, separated, or buried. More specifically, it has been found that when the number percentage P(d/w) of protrusions with a ratio d/w of 0.33 or more and 0.80 or less is 70% or more by number in protrusions with a protrusion height h of 40 nm or more and 300 nm or less, this results in high transferability for extended periods.
Protrusions of 40 nm or more probably produce spacer effects between the surface of toner base particles and a transfer member and improve transferability. On the other hand, protrusions of 300 nm or less probably produce significant effects of suppressing movement, separation, and burying in durability assessment.
It has been found that when the number percentage P(d/w) of protrusions of 40 nm or more and 300 nm or less is 70% or more by number, this results in a higher effect of suppressing the soiling of members while transferability is maintained for extended periods. P(d/w) is preferably 75% or more by number, more preferably 80% or more by number. The upper limit is preferably, but not limited to, 99% or less by number, more preferably 98% or less by number.
Values in the cross-sectional observation of toner with a scanning transmission electron microscope STEM can be determined as described below wherein the width of the horizontal image (the length of a line along the circumference of the surface of a toner base particle) is defined as a perimeter L. That is, Σw/L is preferably 0.30 or more and 0.90 or less, wherein Σw denotes the sum of the protrusion widths w of protrusions with a protrusion height h of 40 nm or more and 300 nm or less among the organosilicon polymer protrusions present in the horizontal image.
Σw/L of 0.30 or more results in higher transferability and a higher effect of suppressing the soiling of members. Σw/L of 0.90 or less results in higher transferability. Σw/L is more preferably 0.45 or more and 0.80 or less.
The fixing percentage of the organosilicon polymer in toner is preferably 80% or more by mass. At a fixing percentage of 80% or more by mass, transferability and the effect of suppressing the soiling of members can be more easily maintained in long-term use. The fixing percentage is more preferably 90% or more by mass, still more preferably 95% or more by mass. The upper limit is preferably, but not limited to, 99% or less by mass, more preferably 98% or less by mass. The fixing percentage may be controlled by the addition rate of the organosilicon compound, the reaction temperature, the reaction time, the reaction pH, and the timing of pH adjustment in the addition and polymerization of the organosilicon compound.
The protrusion height can be determined as described below to improve transferability. In the cumulative distribution of the protrusion height h of protrusions with a protrusion height h of 40 nm or more and 300 nm or less, the protrusion height h80 at a cumulative number of 80% from the smallest of the protrusion height h is preferably 65 nm or more, more preferably 75 nm or more. The upper limit is preferably, but not limited to, 120 nm or less, more preferably 100 nm or less.
In the observation of toner with a scanning electron microscope SEM, the number average diameter of the maximum protrusion diameters R of organosilicon polymer protrusions is preferably 20 nm or more and 80 nm or less, more preferably 35 nm or more and 60 nm or less. In such a range, soiling of members is less likely to occur.
The toner contains an organosilicon polymer with a structure represented by the following formula (1).
R—SiO3/2
R denotes an alkyl group having 1 to 6 carbon atoms or a phenyl group.
In an organosilicon polymer with the structure represented by the formula (1), one of the four valence electrons of the Si atom is bonded to R, and the other three are bonded to an O atom. Two valence electrons of the 0 atom are bonded to Si and constitute a siloxane bond (Si—O—Si). In organosilicon polymers, two Si atoms occupy three 0 atoms, which is represented by —SiO3/2. The —SiO3/2 structure of the organosilicon polymer probably has properties similar to those of silica (SiO2) composed of a large number of siloxane bonds.
In the partial structure represented by the formula (1), R may be an alkyl group having 1 to 6 carbon atoms or an alkyl group having 1 to 3 carbon atoms. Examples of the alkyl group having 1 to 3 carbon atoms include, but are not limited to, a methyl group, an ethyl group, and a propyl group. R may be a methyl group.
The organosilicon polymer can be a polycondensate of an organosilicon compound with a structure represented by the following formula (Z).
In the formula (Z), R1 denotes a hydrocarbon group (an alkyl group) having 1 to 6 carbon atoms, and R2, R3, and R4 independently denote a halogen atom, a hydroxy group, an acetoxy group, or an alkoxy group.
R1 can be an aliphatic hydrocarbon group having 1 to 3 carbon atoms or a methyl group.
R2, R3, and R4 independently denote a halogen atom, a hydroxy group, an acetoxy group, or an alkoxy group (hereinafter also referred to as a reactive group). These reactive groups undergo hydrolysis, addition polymerization, or condensation polymerization and form a cross-linked structure. An alkoxy group having 1 to 3 carbon atoms, such as a methoxy group or an ethoxy group, can be used in consideration of mild hydrolysis at room temperature and precipitation on the surface of toner base particles.
Hydrolysis, addition polymerization, or condensation polymerization of R2, R3, and R4 can be controlled via the reaction temperature, reaction time, reaction solvent, and pH. To produce an organosilicon polymer for use in the present disclosure, one or a combination of organosilicon compounds having three reactive groups (R2, R3, and R4) except R1 in a molecule in the formula (Z) (hereinafter also referred to as a trifunctional silane) may be used.
An organosilicon polymer produced by using an organosilicon compound with the structure represented by the formula (Z) in combination with the following compound may be used, provided that the advantages of the present disclosure are not significantly reduced: an organosilicon compound having four reactive groups per molecule (tetrafunctional silane), an organosilicon compound having two reactive groups per molecule (bifunctional silane), or an organosilicon compound having one reactive group per molecule (monofunctional silane).
The organosilicon polymer content of the toner particles preferably ranges from 1.0% or more by mass and 10.0% or less by mass.
The above specific protrusions may be formed on the surface of toner particles by dispersing toner base particles in an aqueous medium to prepare a toner base particle dispersion liquid and adding an organosilicon compound to the toner base particle dispersion liquid to form the protrusions, thereby preparing a toner-particle dispersion liquid.
The toner base particle dispersion liquid is preferably adjusted to have a solid content of 25% or more by mass and 50% or less by mass. The temperature of the toner base particle dispersion liquid is preferably adjusted to 35° C. or more. The pH of the toner base particle dispersion liquid can be adjusted such that the organosilicon compound is less likely to condense. The pH at which the organosilicon compound is less likely to condense depends on the substance and is preferably within ±0.5 with respect to the pH at which the organosilicon compound is least likely to condense.
The organosilicon compound can be hydrolyzed before use. For example, the organosilicon compound is hydrolyzed in a separate container in a pretreatment. Preferably 40 parts by mass or more and 500 parts by mass or less, more preferably 100 parts by mass or more and 400 parts by mass or less, of water from which ions are removed, such as ion-exchanged water or RO water, per 100 parts by mass of the organosilicon compound is used for hydrolysis. The hydrolysis conditions preferably include a pH range of 2 to 7, a temperature range of 15° C. to 80° C., and a time range of 30 to 600 minutes.
The resulting hydrolysate and the toner base particle dispersion liquid are mixed and adjusted to the pH suitable for condensation (preferably 6 to 12 or 1 to 3, more preferably 8 to 12). The protrusions are easily formed by adjusting the amount of hydrolysate such that the amount of the organosilicon compound is 5.0 parts by mass or more and 30.0 parts by mass or less per 100 parts by mass of the toner base particles. The formation of the protrusions by condensation is preferably performed in the temperature range of 35° C. to 99° C. for 60 minutes to 72 hours.
The pH can be adjusted in two steps to control the protrusion shape on the surface of the toner particles. The protrusion shape on the surface of the toner particles can be controlled by appropriately adjusting the holding time before adjusting the pH, appropriately adjusting the holding time before adjusting the pH in the second step, and condensing the organosilicon compound. For example, holding in the pH range of 4.0 to 6.0 for 0.5 to 1.5 hours and then in the pH range of 8.0 to 11.0 for 3.0 to 5.0 hours is preferred. The protrusion shape can also be controlled by adjusting the condensation temperature of the organosilicon compound in the range of 35° C. to 80° C.
For example, the protrusion width w can be controlled by the addition amount of the organosilicon compound, the reaction temperature, and the reaction pH and the reaction time in the first step. For example, the protrusion width tends to increase with the reaction time in the first step.
The protrusion diameter d and the protrusion height h can also be controlled by the addition amount of the organosilicon polymer, the reaction temperature, and the pH in the second step. For example, the protrusion diameter d and the protrusion height h tend to increase with the reaction pH in the second step.
A specific method for producing toner is described below, but the present disclosure is not limited thereto. Toner base particles can be produced in an aqueous medium, and protrusions containing an organosilicon polymer can be formed on the surface of the toner base particles.
Toner base particles can be produced by a suspension polymerization method, a dissolution suspension method, or an emulsion aggregation method, particularly the suspension polymerization method. In the suspension polymerization method, the organosilicon polymer tends to be uniformly deposited on the surface of the toner base particles, the organosilicon polymer has high adhesiveness, and the environmental stability, the effect of inhibiting a component that reverses the amount of electrical charge, and the durability and stability thereof are improved. The suspension polymerization method is further described below.
The suspension polymerization method is a method for producing toner base particles by granulating a polymerizable monomer composition containing a polymerizable monomer capable of producing a binder resin and an optional additive agent, such as a colorant, in an aqueous medium and polymerizing the polymerizable monomer contained in the polymerizable monomer composition.
If necessary, a release agent and another resin may be added to the polymerizable monomer composition. After the completion of the polymerization process, the produced particles can be washed by a known method and collected by filtration. The temperature may be increased in the latter half of the polymerization process. To remove unreacted polymerizable monomers or by-products, the dispersion medium may be partly evaporated from the reaction system in the latter half of the polymerization process or after the completion of the polymerization process.
The toner base particles thus produced can be used to form organosilicon polymer protrusions by the above method.
The toner may contain a release agent. Examples of the release agent include, but are not limited to, petroleum waxes and their derivatives, such as paraffin waxes, microcrystalline waxes, and petrolatum, montan waxes and their derivatives, Fischer-Tropsch waxes and their derivatives, polyolefin waxes and their derivatives, such as polyethylene and polypropylene, natural waxes and their derivatives, such as carnauba wax and candelilla wax, higher aliphatic alcohols, fatty acids, such as stearic acid and palmitic acid, and acid amides, esters, and ketones thereof, hydrogenated castor oil and its derivatives, plant waxes, animal waxes, and silicone resin.
The derivatives include oxides, block copolymers with vinyl monomers, and graft modified products. The releasing agents may be used alone or in combination. The release agent content is preferably 2.0 parts by mass or more and 30.0 parts by mass or less per 100 parts by mass of the binder resin or a polymerizable monomer forming the binder resin.
A polymerization initiator may be used in the polymerization of the polymerizable monomer. The amount of polymerization initiator to be added preferably ranges from 0.5 to 30.0 parts by mass per 100 parts by mass of the polymerizable monomer. A polymerization initiator may be used alone, or a plurality of polymerization initiators may be used in combination.
A chain transfer agent may be used in the polymerization of the polymerizable monomer to control the molecular weight of a binder resin constituting the toner base particles. The preferred addition amount ranges from 0.001 to 15.000 parts by mass per 100 parts by mass of the polymerizable monomer.
A crosslinking agent may be used in the polymerization of the polymerizable monomer to control the molecular weight of a binder resin constituting the toner base particles. The preferred addition amount ranges from 0.001 to 15.000 parts by mass per 100 parts by mass of the polymerizable monomer.
When an aqueous medium is used in the suspension polymerization, the following dispersion stabilizers can be used for particles of the polymerizable monomer composition: tricalcium phosphate, magnesium phosphate, zinc phosphate, aluminum phosphate, calcium carbonate, magnesium carbonate, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, calcium metasilicate, calcium sulfate, barium sulfate, bentonite, silica, and alumina. The following organic dispersants may be used: poly(vinyl alcohol), gelatin, methylcellulose, methylhydroxypropylcellulose, ethylcellulose, a carboxymethylcellulose sodium salt, and starch. Commercially available nonionic, anionic, and cationic surfactants can also be used.
The toner may contain any colorant, such as a known colorant.
The colorant content preferably ranges from 3.0 to 15.0 parts by mass per 100 parts by mass of the binder resin or a polymerizable monomer capable of forming the binder resin.
A charge control agent, such as a known charge control agent, can be used in the production of toner. The amount of charge control agent to be added preferably ranges from 0.01 to 10.00 parts by mass per 100 parts by mass of the binder resin or polymerizable monomer.
The toner particles may be directly used as toner. If necessary, an organic or inorganic fine powder may be externally added to the toner particles. The organic or inorganic fine powder preferably has a particle size of one tenth or less the weight-average particle diameter of the toner particles in terms of durability when added to the toner particles.
Examples of the organic or inorganic fine powder include:
(1) flowability imparting agents: silica, alumina, titanium oxide, carbon black, and fluorocarbon,
(2) abrasives: metal oxides (for example, strontium titanate, cerium oxide, alumina, magnesium oxide, and chromium oxide), nitrides (for example, silicon nitride), carbides (for example, silicon carbide), and metal salts (for example, calcium sulfate, barium sulfate, and calcium carbonate),
(3) lubricants: fluoropolymer powders (for example, vinylidene fluoride and polytetrafluoroethylene) and fatty acid metal salts (for example, zinc stearate and calcium stearate), and
(4) charge control particles: metal oxides (for example, tin oxide, titanium oxide, zinc oxide, silica, and alumina) and carbon black.
The organic or inorganic fine powder may be subjected to surface treatment to improve the flowability of the toner and uniformize the charging of the toner. Examples of treatment agents for hydrophobic treatment of the organic or inorganic fine powder include unmodified silicone varnishes, modified silicone varnishes, unmodified silicone oils, modified silicone oils, silane compounds, silane coupling agents, organosilicon compounds, and organotitanium compounds. These treatment agents may be used alone or in combination.
The organosilicon polymer of the present exemplary embodiment is characteristically transferred from the toner base particles when the toner is collected from the intermediate transfer belt 10 by the blade 16a. This is because the collected toner base particles become dense and rub against each other near the blade 16a, and the friction causes the organosilicon polymer to be transferred from the toner base particles.
The organosilicon polymer is characteristically soft and easily deformed. Thus, the organosilicon polymer transferred from the toner base particles can be compressed and stretched under a certain pressure. Thus, the organosilicon polymer transferred from the toner base particles near the blade 16a is pressed between the blade 16a and the intermediate transfer belt 10 and extends on the surface of the blade 16a.
In the present exemplary embodiment, the organosilicon polymer in the toner is transferred from the toner base particles, is extended between the blade 16a and the intermediate transfer belt 10 in the blade nip portion Nb, and is located on the surface of the blade 16a. This suppresses the direct contact between the intermediate transfer belt 10 and the blade 16a and improves the durability of the blade 16a. The organosilicon polymer extended on the surface of the blade 16a in the present exemplary embodiment is described below with reference to
As illustrated in
In the present exemplary embodiment, the blade 16a is in contact with the intermediate transfer belt 10 at a pressure of 50 gf/cm. This pressure is defined as a linear pressure applied to the contact position between the intermediate transfer belt 10 and the blade 16a and is measured at the contact position between the intermediate transfer belt 10 and the blade 16a with a film pressure measuring system (trade name: PINCH, manufactured by Nitta Corporation). The linear pressure is calculated by first measuring the total pressure at the contact position with the film pressure measuring system and dividing the measured total pressure by the contact length of the blade 16a. The contact length of the blade 16a in the present exemplary embodiment (the length of the blade 16a in contact with the intermediate transfer belt 10 in the width direction of the intermediate transfer belt 10) is 245 mm.
After residual toner on the intermediate transfer belt 10 is collected by the blade 16a, the organosilicon polymer transferred from the surface of the toner base particles remains near the blade nip portion Nb and forms the blocking layer 70. The organosilicon polymer in the blocking layer 70 is pressed under the pressure of the blade 16a and is stretched in the blade nip portion Nb. The organosilicon polymer thus extended comes into contact with each other and is flatten in the blocking layer 70.
As illustrated in
Next, the adhesion of the organosilicon polymer remaining in the blocking layer 70 to the blade 16a is described below with reference to
As illustrated in
As illustrated in
The surface roughness of the intermediate transfer belt 10 is described in detail below. First, a method for measuring the surface roughness of the intermediate transfer belt 10 is described below.
The surface roughness of the intermediate transfer belt 10 is defined by a 10-point roughness average Rz in the thickness direction of the intermediate transfer belt 10 (hereinafter simply referred to as a surface roughness Rz). The surface roughness Rz of the intermediate transfer belt 10 in the present exemplary embodiment was measured with a surface roughness tester (trade name: Surfcom 1500SD, manufactured by Tokyo Seimitsu Co., Ltd.). The measurement conditions included a measurement length of 1.25 mm, a cut-off wavelength of 0.25 mm, and a measurement reference length of 0.25 mm in the belt width direction perpendicular to the belt conveying direction.
The surface roughness Rz of the intermediate transfer belt 10 can be such that the organosilicon polymer passes through the blade nip portion Nb, whereas the toner particles do not pass through the blade nip portion Nb. More specifically, the size of the organosilicon polymer in the present exemplary embodiment (the size of the protrusions on the toner surface described above) is approximately 50 nm, and the surface roughness Rz can be 0.05 μm or more so that the organosilicon polymer can pass through the blade nip portion Nb. The surface roughness Rz of the intermediate transfer belt 10 can be small enough to prevent the toner particles from passing through the blade nip portion Nb. The average particle diameter of the toner in the present exemplary embodiment is 8 μm, and therefore the surface roughness Rz can be less than 8 μm. In the present exemplary embodiment, the surface roughness Rz is 0.10 μm.
<Adhesion of Organosilicon Polymer to Blade 16a>
Next, the principle of adhesion of the organosilicon polymer passing through the blade nip portion Nb to the blade 16a in the present exemplary embodiment is described below.
In the present exemplary embodiment, the surface layer 81 of the intermediate transfer belt 10 is formed of an acrylic resin, and the elastic portion a1 of the blade 16a in contact with the intermediate transfer belt 10 is formed of a urethane rubber, which is an elastic material. A particulate resin may be dispersed in the surface layer 81 formed of the acrylic resin. In such a case, the size of resin particles to be dispersed can be appropriately changed to control the surface roughness of the intermediate transfer belt 10.
The measurement of the adhesion strength between the acrylic resin constituting the surface layer 81 of the intermediate transfer belt 10 and the organosilicon polymer and the adhesion strength between the urethane rubber constituting the elastic portion a1 of the blade 16a and the organosilicon polymer is described below.
The adhesion strength between the organosilicon polymer and the object can be measured with a scanning probe microscope (hereinafter referred to as an SPM). The scanning probe microscope (SPM) has a probe, a cantilever for supporting the probe, and a displacement measuring device for detecting the bending of the cantilever and can be used to observe the surface profile of a sample by scanning and detecting an atomic force (attractive force or repulsive force) between the probe and the sample.
The adhesion strength of the organosilicon polymer used in the present exemplary embodiment on the intermediate transfer belt 10 or the blade 16a was measured with the SPM. More specifically, a cantilever with a contact silica portion was used as a lever, and after the cantilever was pressed against the intermediate transfer belt 10 by a predetermined pressing force, a force necessary for detaching the cantilever from the intermediate transfer belt 10 was measured. The organosilicon polymer was considered to have properties similar to silica from the viewpoint of its composition, and the adhesion strength between the cantilever with the silica portion and the object was measured as the adhesion strength between the organosilicon polymer and the object. The adhesion strength Fi between the organosilicon polymer and the intermediate transfer belt 10 was measured by this method. The adhesion strength Fc between the blade 16a and the organosilicon polymer was also measured by the method.
The predetermined pressing force for pressing the cantilever against the object in the measurement of the adhesion strength can be the force for pressing the blade 16a against the intermediate transfer belt 10. In the present exemplary embodiment, the pressing force F for pressing the blade 16a against the intermediate transfer belt 10 is 50 gf/cm, and the contact width of the probe of the SPM is 10 nm. Thus, the pressing force of the cantilever for measuring adhesion strength can be 500 nN. Furthermore, to compare the magnitude relationship of adhesion strength, the adhesion strength at a preferred pressing force may be estimated from the result measured at a pressing force that is not the preferred pressing force. In the present exemplary embodiment, the latter method was used to estimate the magnitude relationship between the adhesion strength Fi and the adhesion strength Fc at 500 nN from the results measured at pressing forces of 50 and 100 nN.
According to the above measurement method, the adhesion strength between the silica and the urethane rubber, that is, the adhesion strength Fc between the organosilicon polymer and the blade 16a was 7 nN at a pressing force of 50 nN and 12 nN at a pressing force of 100 nN. The adhesion strength between the silica and the acrylic resin, that is, the adhesion strength Fi between the organosilicon polymer and the intermediate transfer belt 10 was 5 nN at a pressing force of 50 nN and 6 nN at a pressing force of 100 nN. Thus, in the measurement at a pressing force of either 50 or 100 nN, the adhesion strength Fc was higher than the adhesion strength Fi. Furthermore, it can be inferred from the above measurement results that the adhesion strength Fc is 52 nN and the adhesion strength Fi is 14 nN at a pressing force of 500 nN. Thus, it is found from these results that the adhesion strength between the blade 16a and the organosilicon polymer is higher than the adhesion strength between the intermediate transfer belt 10 and the organosilicon polymer.
Thus, due to the difference in adhesion strength of the organosilicon polymer between the blade 16a made of the urethane rubber and the intermediate transfer belt 10 made of the acrylic resin, the organosilicon polymer can adhere to the blade 16a. In the present exemplary embodiment, the acrylic resin is used as a material of the intermediate transfer belt 10, and the urethane rubber is used as a material of the blade 16a. However, the blade 16a and the intermediate transfer belt 10 may be made of any material, provided that the adhesion strength Fc between the blade 16a and the organosilicon polymer is higher than the adhesion strength Fi between the intermediate transfer belt 10 and the organosilicon polymer.
As described above, in the present exemplary embodiment, the organosilicon polymer in the blocking layer 70 extended in the blade nip portion Nb adheres to the elastic portion a1 of the blade 16a and forms the coating layer 61 between the elastic portion a1 and the intermediate transfer belt 10. The coating layer 61 between the elastic portion a1 and the intermediate transfer belt 10 over the entire region of the blade 16a in the width direction of the intermediate transfer belt 10 can reduce the abrasion of the blade 16a in the blade nip portion Nb.
Next, the advantages of the present exemplary embodiment are described below with reference to Comparative Example 1 in which toner containing no organosilicon polymer is used. Comparative Example 1 is substantially the same as the present exemplary embodiment except that the toner contains no organosilicon polymer. In the following description, therefore, components in Comparative Example 1 described in the present exemplary embodiment are denoted by the same reference numerals and letters and are not described again.
The toner in Comparative Example 1 was produced by a method of producing toner base particles and then mixing an external additive with the toner base particles without forming organosilicon polymer protrusions among the methods of producing the toner of the present exemplary embodiment. Toner containing no organosilicon polymer as in Comparative Example 1 does not form the coating layer 61 between the intermediate transfer belt 10 and the blade 16a. Thus, when approximately 20 k sheets of the transfer material P are fed, friction occurs between the blade 16a and the intermediate transfer belt 10, and the abrasion of the front edge of the blade 16a causes faulty cleaning.
Table 1 shows the presence or absence of abrasion of the blade 16a and the presence or absence of faulty cleaning in Comparative Example 1 and the present exemplary embodiment.
The presence or absence of abrasion of the blade 16a was determined by measuring the abrasion loss of the elastic portion a1 of the blade 16a after feeding 20k sheets of the transfer material P. More specifically, after feeding 20k sheets of the transfer material P, the contact state of the blade 16a with the intermediate transfer belt 10 was released, the elastic portion a1 was observed under a microscope, and the abrasion loss was measured in comparison with the inspection result of the elastic portion a1 before feeding the sheets.
The microscope used to measure the abrasion loss is a confocal microscope (OPTELICS, manufactured by Lasertec Corporation). The measurement conditions included an observation area of 100 μm square, a measurement wavelength of 546 nm, and a scan frequency of 0.1 μm in a direction perpendicular to the contact position of the blade 16a. The abrasion loss of the blade 16a used in this evaluation was the maximum value in the longitudinal direction of the blade 16a. In Table 1, after 20 k sheets of the transfer material P were fed, an abrasion loss of 0.5 μm or more of the elastic portion a1 was judged to be the presence of abrasion, and an abrasion loss of less than 0.5 μm of the elastic portion a1 was judged to be the absence of abrasion.
Table 1 shows that in the present exemplary embodiment the organosilicon polymer can adhere to the blade 16a and form the coating layer 61 between the intermediate transfer belt 10 and the blade 16a, thereby improving the durability of the blade 16a.
Next, the relationship between the surface roughness Rz of the intermediate transfer belt 10 and faulty cleaning is described below with reference to Table 2. Modification Examples 1 to 5 and Comparative Examples 2 and 3 in Table 2 are substantially the same as the present exemplary embodiment except that the surface roughness Rz of the intermediate transfer belt 10 is different. In the following description, therefore, components in Modification Examples 1 to 5 and Comparative Examples 2 and 3 described in the present exemplary embodiment are denoted by the same reference numerals and letters and are not described again. In Modification Examples 1 to 5 and Comparative Examples 2 and 3 in Table 2, particles were dispersed in the surface layer 81 made of the acrylic resin, and the particle size of the dispersed particles was changed to adjust the surface roughness Rz.
As described above, when the toner containing the organosilicon polymer is used, the organosilicon polymer adheres to the front edge of the blade 16a in contact with the intermediate transfer belt 10 and forms the coating layer 61. The thickness of the coating layer 61 correlates with the amount of organosilicon polymer passing through the blade nip portion Nb and correlates with the surface roughness Rz of the intermediate transfer belt 10. The coating layer 61 on the blade 16a is examined as described below.
As in the measurement of the abrasion of the blade 16a, the measurement conditions included an observation area of 100 μm square, a measurement wavelength of 546 nm, and a scan frequency of 0.1 μm in a direction perpendicular to the contact position of the blade 16a. The thickness of the coating layer 61 in the width direction of the intermediate transfer belt 10 was defined by measuring the thickness at randomly selected ten positions over the entire longitudinal length of the blade 16a and averaging the measurements.
The thickness of the coating layer 61 in Table 2 is the thickness of the coating layer 61 adhering to the blade 16a after the 10k sheets of the transfer material P were fed. To determine the presence or absence of abrasion in Table 2, after the 10k sheets of the transfer material P were fed, an abrasion loss of 0.3 μm or more of the blade 16a was judged to be “the presence of abrasion”, and an abrasion loss of less than 0.3 μm of the blade 16a was judged to be “the absence of abrasion”
The evaluation of the cleaning performance in Table 2 shows the level of faulty cleaning in image formation after the 10k sheets of the transfer material P were fed. In Table 2, “O” represents the occurrence of no faulty cleaning, “Δ” represents the occurrence of acceptable slight faulty cleaning, and “X” represents the occurrence of unacceptable faulty cleaning.
Table 2 shows that the thickness of the coating layer 61 increases with the surface roughness Rz. This is because the amount of the blocking layer 70 passing through the blade nip portion Nb increases with the surface roughness Rz. An excessively thick coating layer 61 at the front edge of the blade 16a between the blade 16a and the intermediate transfer belt 10 partially collapses due to friction with the moving intermediate transfer belt 10, which may cause a problem. That is, the partial collapse of the coating layer 61 may form a space through which toner passes and may cause faulty cleaning.
Although a thick coating layer 61 can improve the durability of the blade 16a, when the coating layer 61 has a thickness greater than or equal to the size of toner particles, the toner may pass through and impair the cleaning performance. To improve the durability of the blade 16a and simultaneously suppress faulty cleaning, therefore, the surface roughness Rz of the intermediate transfer belt 10 can be smaller than the toner particle size.
As described above, in the present exemplary embodiment, the surface roughness Rz of the intermediate transfer belt 10 can be 0.05 μm or more to reduce the abrasion of the blade 16a. Furthermore, the surface roughness Rz can be smaller than 8 μm to reduce the occurrence of faulty cleaning. As shown in Table 2, to further reduce the occurrence of faulty cleaning due to the passing of toner, the surface roughness Rz of the intermediate transfer belt 10 is more desirably less than 2 μm.
Although the organosilicon polymer is deposited from the surface of the toner base particles in the present exemplary embodiment, the present disclosure is not limited to this embodiment, provided that the organosilicon polymer can be continuously supplied to maintain the extension of the organosilicon polymer.
Although the intermediate transfer belt 10 has the multilayer structure with the base layer and the surface layer in the present exemplary embodiment, the intermediate transfer belt 10 may have a monolayer structure or a multilayer structure with three or more layers. If at least the adhesion strength between the organosilicon polymer and the blade 16a is higher than the adhesion strength between the organosilicon polymer and the surface of the intermediate transfer belt 10, and the surface roughness Rz of the intermediate transfer belt 10 satisfies the range described in the present exemplary embodiment, then the same advantages as in the present exemplary embodiment can be achieved.
Although the image-forming apparatus 100 of the intermediate transfer system with the intermediate transfer belt 10 has been described in the present exemplary embodiment, the present disclosure is not limited to this embodiment. For example, the exemplary embodiment can also be applied to an image-forming apparatus of a direct transfer system with a conveying belt that electrostatically bears and conveys the transfer material P. When a contact member, such as a cleaning blade, is used as a cleaning member to collect residual toner on a conveying belt, an image-forming apparatus of the direct transfer system can also have the same advantages as the exemplary embodiment by utilizing the configuration of the exemplary embodiment.
In the exemplary embodiment 1, the surface roughness Rz of the intermediate transfer belt 10 is adjusted by dispersing resin on the surface of the intermediate transfer belt 10 made of the acrylic resin. The exemplary embodiment 2 is different from the exemplary embodiment 1 in that the surface roughness Rz is adjusted by forming grooves on the surface of an intermediate transfer belt 210 as a structure for allowing the extended organosilicon polymer to pass between the intermediate transfer belt 210 and the blade 16a. The exemplary embodiment 2 is substantially the same as the exemplary embodiment 1 except that the grooves are formed on the surface of the intermediate transfer belt 210. Thus, the components described in the exemplary embodiment 1 are denoted by the same reference numerals and letters and are not described again.
As illustrated in
The groove width W is preferably less than half the average particle diameter of 8 μm of the toner in order to prevent the toner from pathing through. The surface layer 281 has a thickness of 3 μm, and the grooves 84 does not reach the base layer 282 and are formed only in the surface layer 281. In the present exemplary embodiment, the grooves 84 are present in the entire circumference of the intermediate transfer belt 210 along the movement direction (belt conveying direction) of the intermediate transfer belt 210.
The amount of extended organosilicon polymer to adhere to the blade 16a can be increased or decreased by increasing or decreasing the number of the grooves 84 on the intermediate transfer belt 210. The interval I is preferably 10 μm or more and 100 μm or less, particularly preferably 10 μm or more and 20 μm or less from the viewpoint of sufficiently ensuring the contact time between the blade 16a and the grooves 84.
Next, a method of forming the grooves 84 on the intermediate transfer belt 210 is described below. The grooves 84 can be formed by a known method, such as polishing, cutting, or imprinting. The intermediate transfer belt 210 with the grooves on its surface in the present exemplary embodiment can be produced by appropriately selecting and using one of such forming methods. In particular, imprinting utilizing the photocurability of an acrylic resin serving as a base material of a microfabricated surface has low processing costs and high productivity.
In addition to the process of providing the grooves 84 on the surface of the intermediate transfer belt 210 to adjust the surface roughness Rz, for example, the surface roughness Rz of the intermediate transfer belt 210 can also be adjusted by forming irregularities by polishing on the surface of the intermediate transfer belt 210. To form irregularities by polishing on the surface of the intermediate transfer belt 210, a lapping film (Lapika #2000 (trade name), manufactured by KOVAX Corporation) may be used. Fine abrasive particles uniformly dispersed in the lapping film can form a uniform profile without deep scratches or uneven polishing and can form grooves by polishing.
Imprinting in the present exemplary embodiment is described in detail below with reference to
When the grooves 84 are formed by imprinting, as illustrated in
To form the grooves 84 in the intermediate transfer belt 210, the die 92 is heated with a heater (not shown) to a temperature of 130° C., which is higher by 5° C. to 15° C. than the glass transition temperature of poly(ethylene naphthalate). While the heated die 92 abuts against the core 91, the core 91 is rotated once at a circumferential velocity of 264 mm/s, and then the die 92 is separated from the core 91. While the core 91 is rotated, the die 92 rotates with the rotation of the core 91. In the present exemplary embodiment, surface profile processing is performed as described above to form the grooves 84 on the surface layer 281 of the intermediate transfer belt 210.
To form the grooves 84 as in the present exemplary embodiment, as illustrated in
The grooves of the intermediate transfer belt 210 in the present exemplary embodiment are further described below. First, toner in a deep part of excessively deep grooves cannot be cleaned off, and therefore the groove depth D is preferably 4 μm or less. When the grooves are too shallow, the grooves are difficult to process, and the blade 16a easily follows the surface of the intermediate transfer belt 210, making it difficult to improve the durability of the blade 16a. The groove depth D is therefore preferably 0.05 μm or more.
The grooves 84 form a space between the intermediate transfer belt 210 and the blade 16a. The organosilicon polymer passing through the space can adhere to the blade 16a and form the coating layer 61 between the intermediate transfer belt 210 and the blade 16a as in the exemplary embodiment 1. This can improve the durability of the blade 16a. The surface roughness Rz of the intermediate transfer belt 210 in the present exemplary embodiment is in the same range as in the exemplary embodiment 1.
In a modification example of the present exemplary embodiment, for uniform adhesion of the organosilicon polymer to the blade 16a, as illustrated in
Thus, the formation of the grooves 84 on the intermediate transfer belt 210 and the extended organosilicon polymer passing through the blade nip portion Nb can form the coating layer 61 between the blade 16a and the intermediate transfer belt 210 as in the exemplary embodiment 1. Thus, the present exemplary embodiment can have the same advantages as the exemplary embodiment 1.
In the present exemplary embodiment, the pressure of the blade 16a applied to the intermediate transfer belt 10 is changed to alter the extension of the organosilicon polymer, thereby optimizing the thickness of the coating layer 61 on the blade 16a depending on the surface roughness Rz of the intermediate transfer belt 10. More specifically, the adhesion of the organosilicon polymer to the blade 16a depends on the pressure. Components described in the exemplary embodiment 1 are denoted by the same reference numerals and letters and are not described again in the present exemplary embodiment.
A high pressure of the blade 16a results in high followability between the intermediate transfer belt 10 and the blade 16a, which prevents the organosilicon polymer from passing through the surface roughness Rz of the intermediate transfer belt 10. Thus, the pressure of the blade 16a can be increased to optimize the amount of the organosilicon polymer passing through a wider range of the surface roughness Rz of the intermediate transfer belt 10.
For example, when the surface roughness Rz of the intermediate transfer belt 10 is larger than that of the exemplary embodiment 1 and is 0.4 μm, the pressure of the blade 16a is 80 gf/cm, which is higher than 50 gf/cm of the exemplary embodiment 1. This can reduce the passing of the organosilicon polymer as compared with that at a pressure of 50 gf/cm and optimize the amount of the organosilicon polymer passing through.
Table 3 shows the adhesion of the organosilicon polymer to the blade 16a at different pressures of the blade 16a. Table 3 shows the surface state of the intermediate transfer belt 10 and deposits on the blade 16a after 1 k sheets of the transfer material P were fed and after the blade 16a was removed. In Table 3, the deposit on the blade 16a indicates the adhesion of the organosilicon polymer on the removed blade 16a.
The blocking layer 70 on the intermediate transfer belt 10 in Table 3 indicates the amount of the blocking layer 70 remaining on the intermediate transfer belt 10 after the blade 16a was removed. The evaluation criteria include the presence of the blocking layer 70 over the entire surface of the intermediate transfer belt 10 in a direction perpendicular to the rotational direction, partial presence of the blocking layer 70, and the absence of the blocking layer 70. The partial presence means that the blocking layer 70 is held on the removed blade 16a and is partially absent on the intermediate transfer belt 10 and that the blocking layer 70 has cleaning performance when the blade 16a is in contact with the intermediate transfer belt 10.
Table 3 shows that an increased pressure of the blade 16a applied to the intermediate transfer belt 10 results in an increased amount of deposit on the blade 16a and an increased amount of the blocking layer 70. In other words, an increased pressure results in an increased amount of the organosilicon polymer extending near the blade nip portion Nb. The results also show that the pressure required for extending the organosilicon polymer is 30 gf/cm or more in the present exemplary embodiment.
Thus, the amount of the organosilicon polymer extended by the blade 16a can be changed by altering the pressure of 30 gf/cm or more according to the surface roughness of the intermediate transfer belt 10. Thus, the amount of adhered organosilicon polymer can be controlled by the surface roughness Rz of the intermediate transfer belt 10.
The exemplary embodiment 4 is different from the exemplary embodiment 1 in that toner is dispersed in a belt cleaning device 316 for uniform adhesion of the organosilicon polymer to a blade 316a in the longitudinal direction (in the width direction of the intermediate transfer belt 10). The present exemplary embodiment can reduce the difference in the amount of toner collected by the blade 316a in the longitudinal direction and can uniformly improve the durability of the blade 316a in the longitudinal direction. In the following description, the components described in the exemplary embodiment 1 are denoted by the same reference numerals and letters and are not described again.
A minute movement of the intermediate transfer belt 10 in a direction perpendicular to the rotational direction during rotation and the operation of rotating the rotating member 56 to scrape off toner can convey toner densely aggregated in part of the blade nip portion Nb toward a region with a lower toner density. Thus, such different collecting positions at which toner is collected by the rotating member 56 can disperse toner in the longitudinal direction, and the coating layer 61 can be formed between the blade 316a and the intermediate transfer belt 10 in the entire region in the longitudinal direction.
Toner supplied from the rotating member 56 to the conveying member 57 is conveyed in the width direction of the intermediate transfer belt 10 in
Although the toner circulation performance in the longitudinal direction is improved with the stirring member 55 in the present exemplary embodiment, any method of improving the toner circulation performance in the longitudinal direction without the rotating member 56 and the conveying member 57 may be used.
For example, when the installation angle θa of the collection surface of the elastic portion a1 is 90 degrees or more and less than 180 degrees with respect to the gravitational direction, the elastic portion a1 can be placed as illustrated in
A specific circulation mechanism is described in detail below with reference to
In this circulation mechanism, toner is repeatedly collected and circulated on the upstream side of the elastic portion a1 in the belt conveying direction. Thus, the toner is conveyed and dispersed in the longitudinal direction even in a region where the amount of collected toner is small. Thus, even in a non-printing region where toner is not essentially supplied, toner containing the organosilicon polymer is supplied by the toner circulation, and the organosilicon polymer forms the coating layer 61.
Thus, the coating layer 61 can be formed on the entire surface of the blade 16a due to the toner circulation performance in the longitudinal direction and can reduce the abrasion of the blade 16a on the entire surface.
Thus, the present exemplary embodiment can have the same advantages as the exemplary embodiment 1.
In a configuration in which residual toner on a belt is collected by a contact member that abuts against the belt, the present disclosure can improve the durability of the contact member.
While the present disclosure has been described with reference to exemplary embodiments, it is to be understood that the disclosure is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2020-060755 filed Mar. 30, 2020, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020-060755 | Mar 2020 | JP | national |
