JP2006178415A - Image forming method and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming method for making an electrophotographic image having high image density and excellent reproduction by preventing occurrence of image irregularity and worm irregularity based on fog easy to occur by a counter developing method and density lowering of an edge part, and to provide an image forming apparatus. <P>SOLUTION: The image forming method comprises forming an electrostatic latent image on an organic photoreceptor, forming a developing brush by a developer containing toner on a cylindrical developing sleeve, bringing the developing brush into contact with the organic photoreceptor and clearly imaging the electrostatic latent image to a toner image. The organic photoreceptor has a photosensitive layer through an intermediate layer on a conductive support. The intermediate layer contains inorganic particles of a number average uniform primary particle diameter of 5-500 nm and film thickness is 0.5-6.0 μm. The image forming method clearly images the electrostatic latent image to the toner image while rotating the developing sleeve in a counter direction to a rotation direction of the organic photoreceptor. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming method and an image forming apparatus used for electrophotographic image formation, and more particularly to an image forming method and an image forming apparatus used for electrophotographic image formation used in the field of copying machines and printers. Is.

  Electrophotographic photoconductors move from inorganic photoconductors such as Se, arsenic, arsenic / Se alloys, CdS, ZnO, etc. to organic photoconductors with excellent advantages such as pollution and ease of manufacture, and various materials are used. Organic photoreceptors (hereinafter simply referred to as photoreceptors) have been developed.

  In recent years, function-separated type photoreceptors in which charge generation and charge transport functions are assigned to different materials have become mainstream, for example, charge generation layers via an intermediate layer containing inorganic particles on a conductive support. In addition, a laminated type photoreceptor in which a charge transport layer is laminated is widely used (Patent Document 1).

  Turning to the electrophotographic process, latent image forming methods are roughly classified into analog image formation using a halogen lamp as a light source and digital image formation using an LED or laser as a light source. Recently, as a hard copy printer for a personal computer, and in an ordinary copying machine, a digital latent image forming method has been rapidly becoming mainstream because of the ease of image processing and the development of a multifunction device.

  In the digital image forming method, an opportunity to produce an original print image is increased, and a demand for high image quality is increasing. Technology for forming a fine latent image on an organic photoreceptor using an exposure light source with a small spot diameter to form a fine dot image and developing it as a toner image in order to improve the image quality of the electrophotographic image Has been developed.

  That is, as a method for developing a latent image on an organic photoconductor, a parallel developing method in which a developing sleeve provided on the organic photoconductor is advanced in a developing region in parallel with the traveling direction of the organic photoconductor (hereinafter referred to as a parallel developing method). In addition, a developing method (hereinafter referred to as a counter developing method: Patent Document 2) that advances in the counter direction is known, but both of them cannot sufficiently solve the problem when forming a high-density dot image.

  In the developing method in which the developing sleeve provided on the organic photoreceptor is advanced in parallel with the traveling direction of the organic photoreceptor, the developability deteriorates in the periphery of the high density image, the density tends to be insufficient, and the photograph has high contrast. The image quality is likely to deteriorate in an image or the like.

  On the other hand, the developing method that proceeds in the counter direction has high developability and can form a high-density dot image, but often the image is fogged or the density is insufficient at the tip.

  It has been found that the above-described phenomena are not sufficiently solved by merely improving the developer, and these phenomena are emphasized or improved by the characteristics of the organic photoreceptor. However, there is no description linking the constitution of the intermediate layer of the organic photoreceptor and these counter development methods.

Recently, a fine unevenness failure called worm-like unevenness has been a problem. Although the cause of this worm-like unevenness has not been clarified, it is considered that the worm-like unevenness is caused by the fact that the relative speed between the photosensitive member and the developing sleeve is high and the frictional charging between the magnetic brush of the developer and the photosensitive member becomes strong. . For this reason, worm-like unevenness tends to occur more easily in the counter development method than in the parallel development method. Further, the worm-like unevenness has a correlation with the frequency of the developing bias, and the worm-like unevenness is reduced as the frequency is increased. However, when the frequency is increased, the sharpness of the image tends to decrease, and it is difficult to satisfy both the reduction of worm-like unevenness and the sharpness of the image.
JP 2004-133018 A JP 2001-125435 A

  The present invention relates to an image forming method that solves the problems of the prior art as described above, that is, solves the problems that easily occur in the counter development method, and stably forms a high-definition digital image. More specifically, it is possible to produce an electrophotographic image with high image density and good color reproducibility by preventing occurrence of fog and worm-like unevenness due to fogging and a decrease in tip density, which are likely to occur in the counter development method. An image forming method and an image forming apparatus are provided.

  In order to eliminate the above-mentioned problems of the present invention, that is, the occurrence of fog and partial density deficiency that are likely to occur in the counter development method, and to obtain a uniform and high-definition electrophotographic image, the constitution of the developer, organic As a result of examining the relationship between the structure of the photoconductor and the development method, in order to prevent fogging in the counter method with excellent developability, density defects at the front end of the image, and worm-like unevenness at the same time, an organic photoconductor is used. The present inventors have found that it is effective to provide a 0.5 to 6.0 μm intermediate layer containing inorganic fine particles in a cured resin with improved charge carrier rectification, and completed the present invention.

  That is, as a result of intensive studies by the present inventors, by using the intermediate layer of the present invention in the counter development method, the density of the front end of the image is reduced, and fine unevenness failure called worm-like unevenness is prevented and sharp. It has been found that the improvement in performance can be improved at the same time. Although it is not clear why the density reduction at the front end of the image and the prevention of fine unevenness called worm-like unevenness and improvement in sharpness were possible at the same time, in the intermediate layer containing the cured resin of the present invention It is presumed that the blocking ability related to the N-type semiconductor particle diameter has the same effect as increasing the developing bias frequency, and contributes to the uniformity of the potential.

That is, the present invention is achieved by having the following configuration.
1. An electrostatic latent image is formed on the organic photoconductor, a developing brush made of a developer containing toner is formed on a cylindrical developing sleeve, the developing brush is brought into contact with the organic photoconductor, and the electrostatic latent image is formed. In the image forming method for developing a toner image, the organic photoreceptor has a photosensitive layer on an electrically conductive support through an intermediate layer, and the intermediate layer has a number average primary particle size of 5 to 500 nm in a cured resin. The electrostatic latent image is visualized as a toner image while the developing sleeve is rotated in the counter direction with respect to the rotation direction of the organic photoreceptor. An image forming method.
2. 2. The image forming method as described in 1 above, wherein the inorganic particles are metal oxides.
3. 3. The image forming method as described in 1 or 2 above, wherein the inorganic particles are titanium oxide.
4). 3. The image forming method as described in 1 or 2 above, wherein the inorganic particles are aluminum oxide.
5. 5. The image forming method according to any one of 1 to 4, wherein the inorganic particles are surface-treated.
6). 6. The image forming method according to any one of 1 to 5, wherein the curable resin is a reaction product of a melamine resin and an oil-free alkyd resin.
7). 6. The image forming method according to any one of 1 to 5, wherein the curable resin is a reaction product of an oil-free alkyd resin and a blocked isocyanate.
8). 6. The image forming method according to any one of 1 to 5, wherein the curable resin is a reaction product of an organometallic compound and a silane coupling agent.
9. Any one of 1 to 8 above, wherein the organic photoreceptor is a laminated organic photoreceptor in which at least a charge generation layer, a charge transport layer, and optionally a surface layer are provided in this order on a conductive support. 2. The image forming method according to item 1.
10. 10. The image forming method according to any one of 1 to 9, wherein a development gap (Dsd) between the organic photoreceptor and the developing sleeve is 0.2 to 0.6 mm.
11. 11. The image formation as described in any one of 1 to 10 above, wherein a biting depth (Bsd) of the magnetic brush in a developing region between the organic photoreceptor and the developing sleeve is 0.0 to 0.8 mm. Method.
12 12. The image forming method as described in 1 to 11 above, wherein a peripheral speed ratio (Vs / Vopc) between the developing sleeve and the organic photoreceptor is 1.2 to 3.0.
13. The difference | V0−Vdc | between the surface potential V0 of the organic photoreceptor and the DC component Vdc of the developing bias applied to the developing sleeve is 100 to 300V, the DC component Vdc of the developing bias is −300V to −650V, 13. The image forming method according to any one of items 10 to 12, wherein the AC component Vac is 0.5 to 1.5 kV, a frequency of 3 to 9 kHz, a duty of 45 to 70%, and a rectangular wave.
14 An electrostatic latent image is formed on the organic photoconductor, a developing brush made of a developer containing toner is formed on a cylindrical developing sleeve, the developing brush is brought into contact with the organic photoconductor, and the electrostatic latent image is formed. A plurality of image forming units each having a developing unit that visualizes a toner image and a transfer unit that transfers a toner image formed on an organic photoreceptor to a transfer medium are provided, and coloring is performed for each of the plurality of image forming units. In the image forming method in which each color toner image is formed on an organic photoreceptor using the changed toner, and each color toner image is transferred from the organic photoreceptor to a transfer medium to form a color image, the organic photoreceptor is conductive. A photosensitive layer is provided on the support via an intermediate layer, and the intermediate layer contains inorganic particles having a number average primary particle size of 5 to 500 nm in the cured resin and has a thickness of 0.5 to 6.0 μm. In the direction of rotation of the organophotoreceptor Image forming method characterized by, and the electrostatic latent image into a toner image while rotating the developing sleeve in the counter direction.
15. An electrostatic latent image is formed on the organic photoreceptor, a developing brush is formed with a developer containing toner on a cylindrical developing sleeve, the developing brush is brought into contact with the organic photoreceptor, and the electrostatic latent image is formed. In the image forming apparatus having a developing unit that visualizes a toner image, the organic photoreceptor has a photosensitive layer through an intermediate layer on a conductive support, and the intermediate layer is a number average primary particle in a cured resin. It contains inorganic particles having a diameter of 5 to 500 nm and a film thickness of 0.5 to 6.0 μm, and the electrostatic latent image is converted into a toner image while rotating the developing sleeve in a counter direction with respect to the rotation direction of the organic photoreceptor. An image forming apparatus characterized in that the image is visualized.
16. An electrostatic latent image is formed on the organic photoconductor, a developing brush made of a developer containing toner is formed on a cylindrical developing sleeve, the developing brush is brought into contact with the organic photoconductor, and the electrostatic latent image is formed. A plurality of image forming units each having a developing unit that visualizes a toner image and a transfer unit that transfers a toner image formed on an organic photoreceptor to a transfer medium are provided, and coloring is performed for each of the plurality of image forming units. In an image forming apparatus for forming a color image by forming a color toner image on an organic photoreceptor using the changed toner, and transferring the color toner image from the organic photoreceptor to a transfer medium, the organic photoreceptor is conductive. A photosensitive layer is provided on the support via an intermediate layer, and the intermediate layer contains inorganic particles having a number average primary particle size of 5 to 500 nm in the cured resin and has a thickness of 0.5 to 6.0 μm. In the direction of rotation of the organophotoreceptor And, an image forming apparatus characterized by visualizing the toner image an electrostatic latent image while rotating the developing sleeve in the counter direction.

  By using the image forming method and the image forming apparatus of the present invention, it is possible to prevent fogging, density defects at the tip, and worm-like unevenness that are likely to occur in the counter development method, and provide an electrophotographic image with good color reproducibility. can do.

Hereinafter, the present invention will be described in detail.
In the image forming method of the present invention, an electrostatic latent image is formed on an organic photoreceptor, a developing brush is formed with a developer containing toner on a cylindrical developing sleeve, and the developing brush is brought into contact with the organic photoreceptor. Then, in the image forming method of visualizing the electrostatic latent image into a toner image, the organic photoreceptor has a photosensitive layer through an intermediate layer on a conductive support, and the intermediate layer is in a cured resin. It contains inorganic particles with a number average primary particle size of 5 to 500 nm and a film thickness of 0.5 to 6.0 μm. The electrostatic latent image is rotated while the developing sleeve is rotated in the counter direction with respect to the rotation direction of the organic photoreceptor. An image is visualized as a toner image.

  The image forming method of the present invention has the above-described configuration, and thus can prevent fogging and uneven density worm-like unevenness at the tip, which are easily generated by the counter development method, and provide a high-quality digital image or color image. Can do.

  First, the organic photoreceptor according to the present invention will be described. The organic photoreceptor according to the present invention has a photosensitive layer through an intermediate layer having a thickness of 0.5 to 6.0 μm on a conductive support, and the intermediate layer has a number average primary particle size in a cured resin. Contains inorganic particles of 5 to 500 nm.

  When the organic photoreceptor has the above-described configuration, it is possible to prevent the occurrence of fogging and the density defect at the tip, which are likely to occur due to the counter development method, and provide a high-quality digital image or color image.

  Hereinafter, the constitution of the organic photoreceptor according to the present invention will be described.

  In the present invention, the organic photoconductor means an electrophotographic photoconductor constituted by providing an organic compound with at least one of a charge generation function and a charge transport function essential to the configuration of the electrophotographic photoconductor. All known organic photoconductors such as a photoconductor composed of an organic charge generating material or an organic charge transport material, a photoconductor composed of a polymer complex with a charge generating function and a charge transport function are contained.

  The structure of the photoreceptor according to the present invention is preferably a structure in which a charge generation layer and a charge transport layer are sequentially laminated as a photosensitive layer on a conductive support. Furthermore, it is preferable to provide an intermediate layer between the conductive support and the photosensitive layer. If necessary, a surface protective layer may be further formed on the photosensitive layer.

  Preferable specific examples of the layer structure of the organic photoreceptor according to the present invention are described below.

Conductive Support The conductive support used in the photoreceptor according to the present invention may be a sheet-like conductive support, but a cylindrical conductive support is preferably used.

  The cylindrical conductive support means a cylindrical support necessary for forming an endless image by rotating, and the cylindricity is preferably 5 to 40 μm, and more preferably 7 to 30 μm.

  This cylindricity is based on JIS standard (B0621-1984). That is, when the cylindrical substrate is sandwiched between two coaxial geometric cylinders, it is represented by the difference in radius at the position where the distance between the two coaxial cylinders is minimum. In the present invention, the difference in radius is represented by μm. The method of measuring the cylindricity is obtained by measuring the roundness of 7 points in total, that is, 2 points 10 mm on both ends of the cylindrical substrate, 4 points of the central part, and 4 points obtained by dividing the distance between the both ends. The measuring device can be measured using a non-contact universal roll diameter measuring machine (manufactured by Mitutoyo Corporation).

As a material for the conductive support, a metal drum such as aluminum or nickel, a plastic drum deposited with aluminum, tin oxide, indium oxide, or the like, or a paper / plastic drum coated with a conductive substance can be used. The conductive support preferably has a specific resistance of 10 ³ Ωcm or less at room temperature.

  As the conductive support used in the present invention, one having an alumite film that has been sealed on the surface thereof may be used. The alumite treatment is usually performed in an acidic bath such as chromic acid, sulfuric acid, oxalic acid, phosphoric acid, boric acid, sulfamic acid, etc., but anodizing treatment in sulfuric acid gives the most preferable result. In the case of anodizing in sulfuric acid, the sulfuric acid concentration is preferably 100 to 200 g / l, the aluminum ion concentration is 1 to 10 g / l, the liquid temperature is about 20 ° C., and the applied voltage is preferably about 20 V. It is not limited. The average film thickness of the anodized film is usually 20 μm or less, particularly preferably 10 μm or less.

  Further, in the organic photoreceptor according to the present invention, the curing is large when the outer diameter of the cylindrical support is 20 to 80 mm. In the case of a cylindrical support having an outer diameter of 20 to 80 mm, the surface linear velocity of the photoconductor in the image forming process tends to be high, and the tip portion density tends to be lowered and fogging tends to occur in the counter development method.

Intermediate Layer The organic photoreceptor according to the present invention is provided with an intermediate layer between the conductive support and the photosensitive layer. The intermediate layer has a structure containing inorganic particles having a number average primary particle size of 5 to 500 nm in the cured resin, thereby free carriers from the conductive support (electrons and holes entering from the conductive support). Thus, the blocking property is improved, the occurrence of black spots and fog is prevented, and the developability is increased, so that the decrease in the density of the tip portion can be prevented, and an electrophotographic image having a sufficient image density can be obtained.

  Here, when the intermediate layer contains inorganic particles having a number average primary particle size of 5 to 500 nm in the cured resin, the inorganic particles having a number average primary particle size of 5 to 500 nm are dispersed in the resin, and the cured resin layer is formed as a whole. It means the structure that is formed.

The inorganic particles used in the intermediate layer according to the present invention are titanium oxide (TiO ₂ ), zinc oxide (ZnO), tin oxide (SnO ₂ ), zirconium oxide, cerium oxide, iron oxide, aluminum oxide, tungsten oxide, bismuth oxide. Metal oxides such as silicon carbide and titanium carbide, metal carbides such as silicon carbide and titanium carbide, titanates such as strontium titanate, calcium titanate and barium titanate, carbonates such as calcium carbonate, metal nitrides such as aluminum nitride, Sulfates such as barium sulfate, copper sulfate, and zinc sulfate are also used. Of these, the use of aluminum oxide, zirconium oxide, and titanium oxide is desirable. In particular, titanium oxide hardly absorbs visible light and near-infrared light and is white, which is preferable for increasing the sensitivity of the photoreceptor. Moreover, as a titanium oxide, a rutile type titanium oxide and an anatase type titanium oxide are preferable. Further, since the refractive index is relatively large, moire generated when an image is written with coherent light such as laser light can be effectively prevented.

  The inorganic particles are preferably subjected to a surface treatment for improving moisture resistance.

  For example, those surface-treated with a polymer containing methylhydrogensiloxane units are preferred. The molecular weight of the polymer containing the methylhydrogensiloxane unit is 1000 to 20000 having a high surface treatment effect. As a result, the moisture resistance and rectifying property of the inorganic particles are improved, and an intermediate layer containing the inorganic particles is used. As a result, the occurrence of black spots is prevented, and it is effective in producing a high-density dot image.

The polymer containing a methylhydrogensiloxane unit is preferably a copolymer of a structural unit of-(HSi (CH ₃ ) O)-and a structural unit other than this (other siloxane unit). As other siloxane units, dimethylsiloxane units, methylethylsiloxane units, methylphenylsiloxane units, diethylsiloxane units, and the like are preferable, and dimethylsiloxane is particularly preferable. The proportion of methylhydrogensiloxane units in the copolymer is 10 to 99 mol%, preferably 20 to 90 mol%.

  The methylhydrogensiloxane copolymer may be any of a random copolymer, a block copolymer, a graft copolymer, etc., but a random copolymer and a block copolymer are preferred. In addition to methylhydrogensiloxane, the copolymerization component may be one component or two or more components.

  In addition, the inorganic particles may be surface-treated with a reactive organosilicon compound represented by the following formula.

(R) _n -Si- (X) _4-n
(In the above formula, Si represents a silicon atom, R represents an organic group in which carbon is directly bonded to the silicon atom, X represents a hydrolyzable group, and n represents an integer of 0 to 3).
In the organosilicon compound represented by the above formula, the organic group in which carbon is directly bonded to the silicon represented by R includes alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl and dodecyl, phenyl , Aryl groups such as tolyl, naphthyl and biphenyl, epoxy-containing groups such as γ-glycidoxypropyl and β- (3,4-epoxycyclohexyl) ethyl, γ-acryloxypropyl and γ-methacryloxypropyl ( (Meth) acryloyl group, hydroxyl group such as γ-hydroxypropyl, 2,3-dihydroxypropyloxypropyl, vinyl group such as vinyl and propenyl, mercapto group such as γ-mercaptopropyl, γ-aminopropyl, N-β Amino-containing groups such as (aminoethyl) -γ-aminopropyl, γ-chloropropyl, 1,1, - trifluoride Oro propyl, nonafluorohexyl, halogen-containing groups such as perfluorooctylethyl, other nitro, and cyano-substituted alkyl group. Examples of the hydrolyzable group for X include alkoxy groups such as methoxy and ethoxy, halogen groups, and acyloxy groups.

  Moreover, the organosilicon compound represented by the above formula may be used alone or in combination of two or more.

  Further, in the case of a specific compound of an organosilicon compound represented by the above formula and n is 2 or more, a plurality of R may be the same or different. Similarly, when n is 2 or less, the plurality of Xs may be the same or different. Moreover, when using 2 or more types of organosilicon compounds represented by the above formula, R and X may be the same or different between the respective compounds.

  The number average primary particle size of the inorganic fine particles contained in these intermediate layers is preferably 5 nm to 500 nm, more preferably 10 nm to 300 nm, and particularly preferably 15 nm to 100 nm. If the thickness is less than 5 nm, the inorganic particles are likely to aggregate in the binder (resin), the uniformity of the intermediate layer is insufficient, the potential characteristics of the photoreceptor are likely to be unstable, and fogging is likely to occur in the counter development. On the other hand, even if the thickness is larger than 500 nm, the uniformity of the composition of the intermediate layer is insufficient, voids or the like are easily formed in the intermediate layer, and similarly the potential characteristics are likely to be unstable. .

  For example, in the case of titanium oxide, the number average primary particle size of the inorganic fine particles is magnified 10,000 times by observation with a transmission electron microscope, and 100 particles are randomly observed as primary particles. Measured as average diameter.

  In the present invention, the thickness of the intermediate layer is set in the range of 0.5 to 6.0 μm. Furthermore, it is desirable to set in the range of 1-5 μm. If the film thickness of the intermediate layer is smaller than 0.5 μm, fog is likely to occur. Conversely, if the film thickness of the intermediate layer exceeds 6.0 μm, the sensitivity of the photosensitive member decreases, the residual potential increases, and the image density increases. Cause a decline.

  The ratio P / R of the inorganic fine particles (P) and the binder resin (R) contained in the intermediate layer according to the present invention is preferably in the range of 0.9 / 1 to 2.5 / 1 by volume. If the P / R ratio of the intermediate layer is less than 0.9 / 1, the characteristics of the intermediate layer depend on the characteristics of the binder resin, and the characteristics of the photoreceptor greatly change due to changes in temperature and humidity and repeated use. When the P / R ratio exceeds 2/1, voids increase in the undercoat layer, and the adhesion with the charge generation layer decreases. When the P / R ratio exceeds 3/1, air accumulates. When the photosensitive layer is applied and dried, it causes bubbles and causes application defects.

  The cured resin as used in the present invention means that there is a resin component insoluble in both methanol and MEK solvents. Actually, 500 mg of the cured intermediate layer containing inorganic fine particles is peeled off from the substrate, left in a 100 ml methanol or MEK solution for 1 hour at room temperature, and then stirred, and if the inorganic particles are not dispersed separately, to decide.

  In order to form a cured resin, the binder can react with the hydroxyl groups of the inorganic particles in the intermediate layer or the hydroxyl group on the surface of the conductive support to form an intermediate layer that is less dependent on temperature and humidity and less likely to cause a decrease in tip concentration. It is preferable to use a resin. That is, by using a curable resin and forming an intermediate layer containing inorganic particles in the temperature and humidity dependency is small, the charge carrier rectification is improved, and image defects such as black spots are prevented. The contrast of the dot latent image is improved, and the dot image is favorably formed.

  The curable resin according to the present invention is at least one thermosetting resin selected from the group consisting of urea resin, melamine resin, phenol resin, epoxy resin, unsaturated polyester resin, alkyd resin and polyurethane resin, or polyamide. A resin obtained by a reaction between at least one resin selected from the group consisting of a resin, a polyester resin, a polyether resin, an acrylic resin, a polyvinyl alcohol resin, and a polyvinyl acetal resin and a curing agent is preferably used. A melamine resin is also preferably used.

  When a melamine resin is used, a combined system with an oil-free alkyd resin is preferable instead of the melamine resin alone.

  When the cured resin is formed using a curing agent, the hydroxyl value of the curable resin is preferably 60 or more. When the hydroxyl value is less than 60, there are few reaction points with the curing agent, so that sufficient crosslinking is not performed, the film formability is deteriorated, and the adhesion between the photosensitive layer and the conductive support tends to be deteriorated. On the other hand, if the hydroxyl value is greater than 150, the moisture resistance is poor when unreacted functional groups remain, and charge tends to be accumulated as a photoconductor in a humid environment. This is not preferable because the density of the dark part and the gradation are lowered due to the increase of the dark part potential. The term “hydroxyl value” as used herein means a value measured by a method defined in JIS K 0070.

  The curable resin used in the present invention is preferably an oil-free alkyd resin containing at least a hydroxyl group and a blocked isocyanate resin.

  Oil-free alkyd resin is a saturated polyester resin consisting of a polybasic acid and a polyhydric alcohol, and has a straight-chain structure linked by ester bonds that do not contain fatty acids. Furthermore, there are many types depending on the modifier. Preferable specific examples of the oil-free alkyd resin containing a hydroxyl group include Beckolite M-6401-50, M-6402-50, M-6603-60, M-6605-60, 46-118, 46-119, 52-584, M-6154-50, M-6301-45, 55-530, 54-707, 46-169-S, M-6201-40-1M, M-6205-50, 54-409 Ink Chemical Industries, Ltd .: trade name of oil-free alkyd resin), Espel 103, 110, 124, 135 (trade name of oil-free alkyd resin, manufactured by Hitachi Chemical Co., Ltd.) and the like.

  The above curing agent is preferably an isocyanate. As the isocyanate, among isocyanates obtained by reacting a polyisocyanate compound with a compound having active hydrogen as a blocking agent, the isocyanate is stable at normal temperature and blocked when heated under predetermined conditions (for example, 50 to 200 ° C.). An isocyanate in which the agent is dissociated and the isocyanate group is regenerated is preferred.

  Examples of the polyisocyanate compound include tolylene diisocyanate, diphenylmethane-4,4'-diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, and polymethylene polypolyisocyanate.

  Examples of the blocking agent include lactams such as caprolactome, oximes such as methyl ethyl ketoxime and acetoxime, and β-diketones such as diethyl malonate and diethyl acetoacetate.

  Examples of these blocked isocyanate resins include isophorone diisocyanate using ε-caprolactam as a blocking agent, trade names of HULS, Inc .: IPDI-B1065, IPDI-B1530, or internally blocked uretdione-linked block isophorone. The product name: IPDI-BF1540 by the Hills (HULS) company which is diisocyanate is mentioned. Moreover, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, diphenylmethane-4,4'-diisocyanate, hexamethylene diisocyanate and the like blocked with oxime can be mentioned. Examples of oximes include formaldehyde oxime, acetoaldoxime, methyl ethyl ketoxime, cyclohexanone oxime, and the like. Examples of blocked isocyanates blocked with oxime include trade names DM-60 and DM-160 manufactured by Meisei Chemical Industry Co., Ltd., Bernock B7-887-60, B3-867, and DB980K manufactured by Dainippon Ink, Inc.

  Another cured resin is also preferably a cured resin formed by the combined use of an organometallic compound and a silane coupling agent.

  As the organometallic compound, those containing zirconium, titanium, aluminum, manganese or the like are used. Of these, silane coupling agents and organozirconium compounds have very high film-forming properties, low residual potential, little change due to the environment, and little change in potential due to repeated use. Since it exhibits excellent characteristics, it can be preferably used. Examples of the silane coupling agent include vinyltrimethoxysilane, γ-methacryloxypropyl-tris (β-methoxyethoxy) silane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, and γ-glycidoxypropyl. Trimethoxysilane, vinyltriacetoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane, N-β- (aminoethyl) Examples include -γ-aminopropylmethylmethoxysilane, N, N-bis (β-hydroxyethyl) -γ-aminopropyltriethoxysilane, and γ-chloropropyltrimethoxysilane. Further, vinyltriethoxysilane, vinyltris (2-methoxyethoxysilane), 3-methacryloxypropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 2- (3,4-epoxy) are particularly preferably used. (Cyclohexyl) ethyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, 3-aminopropyltriethoxysilane, N -Phenyl-3-aminopropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-chloropropyltrimethoxysilane and the like.

  Examples of the organic zirconium compound include zirconium butyrate, zirconium acetylacetonate, acetylacetone zirconium butyrate, zirconium lactate, and zirconium stearate butyrate. In addition, as the organic titanium compound, tetraisopropyl titanate, tetranormal butyl titanate, butyl titanate dimer, tetra (2-ethylhexyl) titanate, titanium acetylacetonate, polytitanium acetylacetonate, titanium octylene glycolate, titanium lactate ammonium salt , Titanium lactate, titanium lactate ethyl ester, titanium triethanolamate, polyhydroxytitanium stearate and the like.

  For the purpose of further improving the film formability of these organometallic compounds, a resin can be added to the organometallic compounds. Acetal resin such as polyvinyl butyral, polyvinyl alcohol resin, casein, polyamide resin, cellulose resin, gelatin, polyurethane resin, polyester resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinyl acetate resin, vinyl chloride-vinyl acetate-anhydrous malein Acid resin, silicon resin, silicon-alkyd resin, phenol-formaldehyde resin, melamine resin, or the like can be used.

  As a solvent for preparing the coating solution for forming the intermediate layer, any known organic solvent such as alcohol, aromatic, halogenated hydrocarbon, ketone, ketone alcohol, ether, ester, etc. Can be selected.

  For example, methanol, ethanol, n-propanol, iso-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, ethyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, Usual organic solvents such as methylene chloride, chloroform, chlorobenzene, and toluene can be used.

  Moreover, the solvent used for these dispersion | distribution can be used individually or in mixture of 2 or more types. When mixing, any solvent can be used as long as it can dissolve the binder resin as the mixed solvent.

  As a method for dispersing the inorganic particles surface-treated with a coupling agent or the like in the binder resin, methods such as a roll mill, a ball mill, a vibrating ball mill, an attritor, a sand mill, a colloid mill, and a paint shaker can be used. Furthermore, as an application method used when providing this undercoat layer, a usual method such as a blade coating method, a wire bar coating method, a spray coating method, a dip coating method, a bead coating method, an air knife coating method, or a curtain coating method is used. Can be used.

Photosensitive layer Charge generation layer (CGL)
The charge generation layer is a layer mainly composed of a charge generation material (CGM), and a binder resin may be used as necessary.

  A known material can be used as the charge generating substance. For example, phthalocyanine pigments such as metal phthalocyanine and metal-free phthalocyanine, azulenium salt pigments, squaric acid methine pigments, azo pigments having a carbazole skeleton, azo pigments having a triphenylamine skeleton, azo pigments having a diphenylamine skeleton, dibenzothiophene skeleton Azo pigments having fluorenone skeleton, azo pigments having oxadiazole skeleton, azo pigments having bis-stilbene skeleton, azo pigments having distyryl oxadiazole skeleton, azo pigments having distyrylcarbazole skeleton, perylene Pigments, anthraquinone or polycyclic quinone pigments, quinoneimine pigments, diphenylmethane and triphenylmethane pigments, benzoquinone and naphthoquinone pigments, cyanine and azomethine pigments, Goido based pigments, and bisbenzimidazole pigments. These charge generation materials can be used alone or as a mixture of two or more.

  When a binder is used as the CGM dispersion medium in the charge generation layer, a known resin can be used as the binder, but the most preferred resins include formal resin, butyral resin, silicone resin, silicone-modified butyral resin, phenoxy resin, and the like. Can be mentioned. The ratio of the binder resin to the charge generating material is preferably 20 to 600 parts by mass with respect to 100 parts by mass of the binder resin. By using these resins, the increase in residual potential associated with repeated use can be minimized. The thickness of the charge generation layer is preferably 0.3 μm to 2 μm.

Charge transport layer (CTL)
The charge transport layer is a layer intended to hold a charged charge and to couple the charge generated and separated in the charge generation layer by exposure to the charged charge that has been held. In order to achieve the purpose of holding the charged charge, it is required that the electric resistance is high. Further, in order to achieve the purpose of obtaining a high surface potential with the charged charge that has been held, it is required that the dielectric constant is small and the charge mobility is good.

  The charge transport layer for satisfying these requirements is composed of a charge transport material (CTM) and a binder resin used as necessary. Such a charge transport layer can be formed by dissolving or dispersing these charge transport materials and a binder resin in an appropriate solvent, and applying and drying them. If necessary, an appropriate amount of additives such as a plasticizer, an antioxidant, and a leveling agent can be added to the charge transport layer in addition to the charge transport material and the binder resin.

  Examples of the charge transporting material include a hole transporting material and an electron transporting material, and the hole transporting material is preferable in the layer structure of the organic photoreceptor according to the present invention.

  The charge transport layer contains a charge transport material (CTM) and a binder resin that disperses and forms a CTM. Other substances may contain additives such as antioxidants as necessary.

  As the charge transport material, a known hole transport property (P-type) charge transport material (CTM) can be used. For example, a triphenylamine derivative, a hydrazone compound, a styryl compound, a benzidine compound, a butadiene compound, or the like can be used. These charge transport materials are usually dissolved in a suitable binder resin to form a layer.

  As the charge transport material according to the present invention, those having relatively high charge mobility, good dispersibility in the binder, and stable potential characteristics are preferable. In particular, the following general formulas (1) and ( The compound 2) is preferred.

(In the general formula (1), R ₁ and R ₁ ′ each represent a hydrogen atom, an alkyl group, an alkoxy group or a halogen atom, and R ₂ , R ₂ ′, R ₃ and R ₃ ′ each represent a hydrogen atom, Represents an alkyl group, an alkoxy group, a halogen atom or a substituted amino group, and m, m ′, n and n ′ each represent an integer of 1 or 2.)

(In the general formula (2), R ₁ represents a hydrogen atom, an alkyl group, an alkoxy group or a halogen atom, and R ₂ and R ₃ represent an alkyl group, a substituted or unsubstituted aralkyl group or a substituted or unsubstituted aryl group. R ₂ and R ₃ may be the same or different, R ₄ and R ₅ represent a hydrogen atom, a lower alkyl group or a substituted or unsubstituted aryl group, and Ar represents a substituted or unsubstituted aryl group And Ar and R ₅ may combine to form a ring.)
Specific examples of the compound of the general formula (1) are shown below.

  Specific examples of the compound of the general formula (2) are shown below.

  The binder resin used for the charge transport layer (CTL) may be either a thermoplastic resin or a thermosetting resin. For example, polystyrene, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, polyvinyl butyral resin, epoxy resin, polyurethane resin, phenol resin, polyester resin, alkyd resin, polycarbonate resin, silicone resin, melamine resin, and these resins A copolymer resin containing two or more of the repeating unit structures. In addition to these insulating resins, high molecular organic semiconductors such as poly-N-vinylcarbazole can be used. Of these, polycarbonate resins are most preferred because of their low water absorption and good CTM dispersibility and electrophotographic characteristics.

  The ratio of the binder resin to the charge transport material is preferably 50 to 200 parts by mass with respect to 100 parts by mass of the binder resin. The total thickness of the charge transport layer is preferably 20 μm or less, and more preferably 10 to 16 μm. When the film thickness exceeds 20 μm, the absorption and scattering of the short wavelength laser in the charge transport layer increase, and the sharpness tends to decrease and the residual potential tends to increase.

  The surface layer of the photoreceptor according to the present invention preferably contains an antioxidant. The surface layer is easily oxidized by an active gas such as NOx or ozone during charging of the photoconductor, and image blur is likely to occur. However, the presence of an antioxidant can prevent image blur. Typical examples of the antioxidants are those that prevent the action of oxygen under conditions of light, heat, discharge, etc. on auto-oxidizing substances present in the organic photoreceptor or on the surface of the organic photoreceptor, It is a substance that has the property of inhibiting.

  Further, it is preferable that the uppermost layer of the photoreceptor according to the present invention contains a fluorine-containing resin fine particle. By including the fluorine-containing resin fine particles in the resurface layer, the transferability of the toner image formed on the surface of the photoreceptor to a transfer material or the like is improved, and the reproducibility of the dot image is improved.

  Solvents or dispersion media used to form layers such as intermediate layers, charge generation layers, and charge transport layers include n-butylamine, diethylamine, ethylenediamine, isopropanolamine, triethanolamine, triethylenediamine, N, N-dimethylformamide, acetone , Methyl ethyl ketone, methyl isopropyl ketone, cyclohexanone, benzene, toluene, xylene, chloroform, dichloromethane, 1,2-dichloroethane, 1,2-dichloropropane, 1,1,2-trichloroethane, 1,1,1-trichloroethane, trichloroethylene, Tetrachloroethane, tetrahydrofuran, dioxolane, dioxane, methanol, ethanol, butanol, isopropanol, ethyl acetate, butyl acetate, dimethyl sulfoxide, methyl cello Lube, and the like. Although this invention is not limited to these, Dichloromethane, 1, 2- dichloroethane, methyl ethyl ketone, etc. are used preferably. These solvents may be used alone or as a mixed solvent of two or more.

  A developing device (developing means) of the counter developing system will be described with reference to FIG. The developing device in FIG. 1 is a contact type two-component type developing device, but the present invention is not limited to this contact type two-component type developing device. For example, a non-contact type one-component type developing device is also employed. it can. In the developing device 102, a developing sleeve 120 (developer carrying member) in which a cylindrical magnet 121 is non-rotatably disposed in an opening of a developing container 110 containing a two-component developer is an organic photoreceptor (image carrier). The developing sleeve 120 is arranged to face the organic photosensitive member 101 rotating in the direction of the arrow, and the developing sleeve 120 rotates counterclockwise so that the developer adsorbed and held on the surface of the developing sleeve 120 and the organic photosensitive member 101 is It is transported to the opposite developing unit. The magnet 121 has a developing magnetic pole N1 on the organic photoreceptor 101 side, and the first conveying magnetic pole S3, the second conveying magnetic pole N2, the third conveying magnetic pole S2, and the second conveying magnetic pole S2 are arranged in the rotational direction of the developing sleeve 120 from the developing magnetic pole N1. 3. It has a pumping magnetic pole S1 constituting a conveying magnetic pole and a separating magnetic pole.

  The developer in the developing container 110 is attracted and held on the developing sleeve 120 by the action of the pumping pole S1 at the position (pumping position) Q on the surface of the developing sleeve 120 corresponding to the pumping magnetic pole S1 of the magnet 121, and the developing blade After the layer thickness is regulated by 122 (developer layer thickness regulating means), the developing part is reached, and a magnetic brush (developing brush) is formed by the action of the developing magnetic pole N1 in the developing part. Develop.

  The developer whose toner density is reduced by the development is held on the developing sleeve 120 and returned to the inside of the developing container 110 by the action of the first and second transport magnetic poles S3 and N2, and the third transport magnetic pole S2 and the pumping magnetic pole S1. At the position (developer dropping position) P on the surface of the developing sleeve 120 where the intermediate magnetic flux density is the smallest, it peels off from the developing sleeve 120 and falls. The developing sleeve 120 from which the developer has been peeled is adsorbed and held by the new developer at the pumping position Q as described above.

  A first agitating and conveying member 123 is installed below the developing sleeve 120 in the developing container 110, and a second agitating and conveying member 124 is further installed via a partition wall 140. These first and second agitating / conveying members 123 and 124 are of a screw type and have a helical screw blade 128 and a plate-like protrusion 130 between the blades.

  The developer having a low toner concentration peeled off from the developing sleeve 120 falls on the first stirring / conveying member 123 and is stirred and conveyed in the axial direction by the first stirring / conveying member 123 in the axial direction. This is passed to the second agitating and conveying member 124 through an opening (not shown). The second agitating / conveying member 124 conveys the developer and the toner replenished from the replenishing port 118 of the developing container 110 in a reverse rotation to the above while agitating, and an opening (not shown) at the other end of the partition wall 140. And return to the first stirring and conveying member 123 side.

A preferred configuration of the counter development method will be described. Here, the gap between the photosensitive member 101 and the developing sleeve 120 in the developing portion near the developing magnetic pole N1 in FIG. 1 is a developing gap (Dsd), and the height of the magnetic brush formed on the developing sleeve 120 by the developing magnetic pole N1. Is called the developing brush height (h).
(1) Development gap (Dsd): 0.2 to 0.6 mm
When Dsd is set to 0.2 to 0.6 mm, development is performed in a strong developing electric field, the binding force of the magnetic carrier to the developing sleeve is increased, and the magnetic carrier is prevented from being transferred to and adhered to the photoconductor. it can. In addition, since the developing electric field at the developing gap is increased, the edge effect is reduced and the developing ability is improved. Accordingly, it is possible to prevent the occurrence of thinning of the horizontal line image and white-out at the rear end (deterioration at the rear end), and improve the developability of the solid image.
(2) Depth of penetration of magnetic brush (Bsd): 0.0 to 0.8 mm, Depth of penetration of magnetic brush (Bsd) = Development brush height (h) −Development gap (Dsd)
By setting the magnetic brush biting depth to 0.0 to 0.8 mm, the pressure contact with the developer in the developing portion is reduced, and the developer is prevented from slipping through the gap between the developing sleeve 120 and the developing blade 122. The Further, it is possible to prevent the development failure of the isolated dot image and the increase in the rough feeling of the halftone image caused by the non-uniform contact of the magnetic brush. When the magnetic brush bite depth is 0 or less, that is, in a non-contact state, the density tends to decrease. When the depth is larger than 0.8 mm, the developer overflows from the nip portion, and uniform image formation cannot be expected.
(3) Peripheral speed ratio (Vs / Vopc) between the developing sleeve and the photoreceptor: 1.2 to 3.0
By setting the peripheral speed ratio of the developing sleeve to the photoreceptor to 1.2 to 3.0, high developability can be obtained. If the peripheral speed ratio is increased too much, the contact frequency of the magnetic brush on the developing sleeve with respect to the photosensitive member increases too much, and the contact state of the magnetic brush with respect to the latent photosensitive member, that is, the mechanical force becomes excessively large. Are likely to fall off, and the carrier is likely to adhere to the photoreceptor, and as a result, the brush image of the magnetic brush is formed on the toner image on the photoreceptor. On the other hand, if the peripheral speed ratio is lowered too much, the chance of contact of the magnetic brush with the photoreceptor is reduced too much, and the developability is lowered. Accordingly, when the peripheral speed ratio is smaller than 1.2, the density is lowered, and when it is larger than 3.0, there is a problem in toner scattering, carrier adhesion, or developing sleeve durability. On the other hand, by setting the peripheral speed ratio within the above range, it is possible to prevent brush eyes. Furthermore, it has the function of preventing the developing effect from becoming excessively high and enhancing the edge effect.
(4) Development bias condition The difference | V0-Vdc | between the surface potential V0 of the photosensitive member and the DC component Vdc of the developing bias applied to the developing sleeve is 100 to 300V, and the DC component Vdc of the developing bias is -300V to -650V. The AC component Vac of the developing bias is preferably 0.5 to 1.5 kV, the frequency is 3 to 9 kHz, the duty is 45 to 70% (the development-side time ratio in the rectangular wave), and the rectangular wave. That is, in a small two-component developing device having an outer diameter of the developing sleeve of φ30 mm or less and an outer diameter of the photosensitive member of φ60 mm or less, the developing nip width is reduced and the developing ability is reduced by making the developing sleeve small. The development bias condition can be improved by the development bias condition.

  Next, the process cartridge and the electrophotographic apparatus according to the present invention will be described. FIG. 2 shows a schematic configuration of an electrophotographic apparatus having a process cartridge having an organic photoreceptor according to the present invention.

  In FIG. 2, reference numeral 11 denotes a drum-shaped organic photoconductor according to the present invention, which is driven to rotate about a shaft 12 in the direction of an arrow at a predetermined peripheral speed. In the rotation process, the organic photoreceptor 11 is uniformly charged with a positive or negative predetermined potential on its peripheral surface by the primary charging unit 13, and then output from an exposure unit (not shown) such as slit exposure or laser beam scanning exposure. The exposure light 14 that is emphasized and modulated corresponding to the time-series electric digital image signal of the target image information is received. In this way, electrostatic latent images corresponding to the target image information are sequentially formed on the peripheral surface of the organic photoreceptor 11.

  The formed electrostatic latent image is then developed with toner by the developing unit 15 and is taken out from a paper feeding unit (not shown) between the organic photoconductor 11 and the transfer unit 16 in synchronization with the rotation of the organic photoconductor 11. The toner image formed and supported on the surface of the organic photoreceptor 11 is sequentially transferred by the transfer means 16 to the fed transfer material 17.

  A transfer material (a support supporting the final fixed image: for example, plain paper, a transparent sheet, etc.) 17 that has received the transfer of the toner image is separated from the organic photoreceptor surface and introduced into the image fixing means 18 for image fixing. When received, the image is printed out as an image formed product (print, copy).

  After the image transfer, the surface of the organic photoconductor 11 is cleaned by removing the transfer residual toner by the cleaning unit 19, and is further subjected to a charge removal process with a pre-exposure light 20 from a pre-exposure unit (not shown). Used repeatedly for image formation. When the primary charging unit 13 is a contact charging unit using a charging roller or the like, pre-exposure is not always necessary.

  In the present invention, a plurality of constituent elements such as the above-mentioned organic photoreceptor 11, primary charging means 13, developing means 15 and cleaning means 19 are housed in a container 21 and integrally combined as a process cartridge. The process cartridge may be configured to be detachable from an electrophotographic apparatus main body such as a copying machine or a laser beam printer. For example, at least one of the primary charging unit 13, the developing unit 15, and the cleaning unit 19 is integrally supported together with the organic photoreceptor 11 to form a cartridge, and is detachable from the apparatus main body using a guide unit 22 such as a rail of the apparatus main body. Process cartridge.

  An embodiment of an electrophotographic printer (hereinafter simply referred to as a printer) will be described as a full-color image forming apparatus to which the present invention is applied.

  FIG. 3 is a schematic configuration diagram of the printer according to the present embodiment. In the drawing, a photosensitive member 56 as a latent image carrier is rotated counterclockwise in the drawing, and its surface is uniformly charged by a charging charger 53 using a corotron, a scorotron or the like, and then a laser optical device (not shown). The electrostatic latent image is carried by scanning with the laser beam L emitted from the laser beam L. Since this scanning is performed based on single-color image information obtained by decomposing a full-color image into yellow, magenta, cyan, and black color information, a single-color electrostatic image of yellow, magenta, cyan, or black is formed on the photosensitive drum 56. A latent image is formed. A revolver developing unit 50 is disposed on the left side of the photosensitive drum 56 in the drawing. This has a yellow developing unit, a magenta developing unit, a cyan developing unit, and a black developing unit in a rotating drum-shaped casing, and each developing unit is sequentially moved to a developing position facing the photosensitive drum 56 by rotation. Move. The yellow developer, magenta developer, cyan developer, and black developer are for developing an electrostatic latent image by attaching yellow toner, magenta toner, cyan toner, and black toner, respectively. An electrostatic latent image for yellow, magenta, cyan, and black is sequentially formed on the photosensitive drum 56, and these images are sequentially developed by the developing units of the revolver developing unit 50, so that a yellow toner image, a magenta toner image, and a cyan toner are developed. A toner image and a black toner image are obtained.

  An intermediate transfer unit is disposed on the downstream side of the photosensitive drum 56 from the development position. This is because the intermediate transfer belt 58 stretched by a tension roller 59a, an intermediate transfer bias roller 57 as a transfer means, a secondary transfer backup roller 59b, and a belt drive roller 59c is driven by rotation of the belt drive roller 59c. Move endlessly clockwise. The yellow toner image, magenta toner image, cyan toner image, and black toner image developed on the photosensitive drum 56 enter the intermediate transfer nip where the photosensitive drum 56 and the intermediate transfer belt 58 are in contact with each other. Then, while being influenced by the bias from the intermediate transfer bias roller 57, the toner image is superimposed and transferred onto the intermediate transfer belt 58 to form a four-color superimposed toner image.

  The surface of the photosensitive drum 56 that has passed through the intermediate transfer nip with the rotation is cleaned of the transfer residual toner by the drum cleaning unit 55. The cleaning unit 55 cleans the transfer residual toner with a cleaning roller to which a cleaning bias is applied. However, a cleaning brush made of a fur brush, a mag fur brush, or a cleaning blade may be used.

  The surface of the photosensitive drum 56 from which the transfer residual toner has been cleaned is discharged by the discharging lamp 54. As the charge removal lamp 54, a fluorescent lamp, a tungsten lamp, a halogen lamp, a mercury lamp, a sodium lamp, a light emitting diode (LED), a semiconductor laser (LD), an electroluminescence (EL), or the like is used. A semiconductor laser is used as the light source of the laser optical device. About these emitted lights, you may make it use only a desired wavelength range by various filters, such as a sharp cut filter, a band pass filter, a near-infrared cut filter, a dichroic filter, an interference filter, and a color temperature conversion filter.

  A transfer unit including various rollers such as a transfer belt, a transfer bias roller, and a drive roller is disposed on the lower side of the intermediate transfer unit in the figure. On the left side of the figure, a conveyance belt 64 and a fixing unit 65 are provided. It is arranged. In the transfer unit, the endlessly moving transfer belt may be moved in the vertical direction in the drawing by a moving means (not shown), and at least one color toner image (yellow toner image) on the intermediate transfer belt 58, When the two-color or three-color superimposed toner image passes through the position facing the paper transfer bias roller 63, the toner image moves to a position where it does not contact the intermediate transfer belt 58. Then, before the leading end of the four-color superimposed toner image on the intermediate transfer belt 58 enters the position facing the paper transfer bias roller 63, it moves to the contact position with the intermediate transfer belt 58 to move to the secondary transfer nip. Form.

  On the other hand, the registration roller pair 61 sandwiching the transfer paper 60 sent from a paper feed cassette (not shown) between the two rollers can superimpose the transfer paper 60 on the four-color superimposed toner image on the intermediate transfer belt 58. It feeds toward the secondary transfer nip at the timing. The four-color superimposed toner image on the intermediate transfer belt 58 is secondarily transferred collectively onto the transfer paper P under the influence of the secondary transfer bias from the paper transfer bias roller 63 in the secondary transfer nip. A full color image is formed on the transfer paper 60 by this secondary transfer.

  The transfer paper 60 on which the full-color image is formed is sent to the paper transport belt 64 by the transfer belt 62.

In the present invention, a toner image transfer medium on a photosensitive member such as an intermediate transfer belt (intermediate transfer member) or a transfer material is generally referred to as a transfer medium.
The conveying belt 64 sends the transfer paper 60 received from the transfer unit into the fixing unit 65.

  The fixing unit 65 conveys the transferred transfer paper 60 while being sandwiched between fixing nips formed by contact between the heating roller and the backup roller.

  The full-color image on the transfer paper 60 is fixed on the transfer paper 60 under the influence of heating from the heating roller and pressure applied in the fixing nip.

  Although not shown, a bias for attracting the transfer paper P is applied to the transfer belt 62 and the conveyance belt 64. In addition, a paper neutralization charger that neutralizes the transfer paper 60 and three belt neutralization chargers that neutralize each belt (intermediate transfer belt 58, transfer belt 62, and conveyance belt 64) are provided. The intermediate transfer unit also includes a belt cleaning unit having the same configuration as that of the drum cleaning unit 55, thereby cleaning the transfer residual toner on the intermediate transfer belt 58.

  FIG. 4 is a modification of the printer according to this embodiment. This apparatus is a so-called tandem printer, and does not share the photosensitive drum 80 for each color, but includes photosensitive drums 80Y, 80M, 80C, and 80Bk for the respective colors. A drum cleaning unit (cleaning means) 85, a charge eliminating lamp 83, and a charging roller (charging means) 84 for uniformly charging the drum are also provided for each color. In FIG. 4, 81 is exposure light, 82 is a developing unit (developing means), 83 is a slow lamp, 86 is a transfer bias roller, 87 is an intermediate transfer belt, 88 is a registration roller for transfer paper 89, and 90 is a transfer roller. Bias roller (transfer means), 91 is a transfer belt, 92 is a transport belt, 93 is a fixing unit, and 94 is a fur brush. In the printer shown in FIG. 3, the charging charger 53 is provided as the drum uniform charging means, but in this printer, the charging roller 84 is provided.

  In the tandem system, it is preferable to configure an image forming unit in which a photoreceptor, a charging unit, an exposure unit, a developing unit, a transfer unit, and the like are combined for each color.

  In the tandem system, latent image formation and development of each color can be performed in parallel, so that the image formation speed can be made much faster than the revolver system.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited by these Examples. In addition, "part" in a sentence represents a mass part.

  A cylindrical conductive aluminum support was cut so that the surface roughness Rz was 0.3 μm, washed with water, dried, and then sequentially coated with the following liquid composition to prepare a photoreceptor. .

Preparation of Photoconductor 1 <Intermediate Layer Coating Solution 1> (UCL-1)
Oil-free alkyd resin (alkyd resin Beckolite M-6401-50 (solid content 50% by mass) (manufactured by Dainippon Ink & Chemicals)) 150 parts Melamine resin Super Becamine G-821-60 (solid content 60% by mass) (large 100 parts Methyl ethyl ketone 500 parts Titanium oxide (methyl hydrogen polysiloxane-treated rutile titanium oxide: number average primary particle size 50 nm) 450 parts A ball mill using the above composition liquid and alumina balls as media Was dispersed for 36 hours to prepare an intermediate layer coating solution 1. This intermediate layer coating solution was applied to an aluminum base tube and dried at 140 ° C. for 20 minutes to form an intermediate layer having a thickness of 3.0 μm.

<Coating liquid 1 for charge generation layer> (CGL-1)
Butyral resin ESREC BMS (manufactured by Sekisui Chemical Co., Ltd.) 5 parts Cyclohexanone 200 parts Charge generation material: (CGM-1) 20 parts The above composition liquid was prepared and dispersed in a ball mill for 72 hours. Next, 210 parts of cyclohexanone was added and dispersed for 5 hours. This was diluted with a mixture of cyclohexanone / methyl ethyl ketone = 2/1 while stirring so that the solid content was 2.0% by mass. The charge generation layer coating solution 1 thus obtained was dip-coated on the intermediate layer and dried at 130 ° C. for 20 minutes to form a charge generation layer having a thickness of about 0.2 μm.

<Coating liquid 1 for charge transport layer> (CTL-1)
Charge transport material (CT2-3) 80 parts Polycarbonate resin Panlite TS2050 (manufactured by Teijin Chemicals Co., Ltd.) 100 parts Sanyo Chemical Co., Ltd. Ionette DS-300 1.0 parts Silicon oil KF-50 (manufactured by Shin-Etsu Chemical Co., Ltd.) 0.02 Part 770 parts or more of tetrahydrofuran was dissolved to prepare a charge transport layer coating solution 1. This liquid coating solution 1 was dip-coated on the charge generation layer CGL and dried at 135 ° C. for 20 minutes to form a charge transport layer having a thickness of 25 μm, thereby preparing a photoreceptor. The photoreceptor 1 is assumed.

Preparation of photoreceptor 2 <Intermediate layer coating solution 2> (UCL-2)
Methoxymethylated nylon fine resin FR-301 (methoxymethylation rate 20%) (manufactured by Lead City) 30 parts Butylated melamine resin Superbecamine G-821-60 (non-volatile content 60%) (Dainippon Ink and Chemicals, Inc.) 50 parts Methanol 200 parts n-Butanol 50 parts Methyl ethyl ketone 250 parts Titanium oxide (methyl hydrogen polysiloxane-treated rutile type titanium oxide: number average primary particle size 8 nm) 240 parts Distributed. Thereafter, 60.0 parts of maleic acid (solid content 10%) dissolved in methanol was added to prepare an intermediate layer coating solution 2. This intermediate layer coating solution was applied onto a cylindrical aluminum support and dried at 140 ° C. for 20 minutes to provide a 5.0 μm intermediate layer.
<Coating liquid 2 for charge generation layer> (CGL-2)
Charge generation material (CGM-2) 24.0 parts Charge generation material: τ-type metal-free phthalocyanine pigment (TPA-891: manufactured by Toyo Ink)
12.0 parts Methyl ethyl ketone 330 parts The above composition was dispersed in a ball mill for 168 hours. After the completion of dispersion, a resin solution prepared by dissolving 12 parts of polyvinyl butyral (ESREC BL-1: manufactured by Sekisui Chemical Co., Ltd.) in 390 parts of methyl ethyl ketone and 1680 parts of cyclohexanone was added and dispersed for 5 hours.

The charge generation layer coating solution 2 thus obtained was dip coated on the intermediate layer and dried at 130 ° C. for 20 minutes to form a charge generation layer having a thickness of about 0.3 μm.
<Coating liquid 2 for charge transport layer> (CTL-2)
Charge transport material (CT2-3) 90 parts Bisphenol Z-type polycarbonate resin Iupilon Z-300 (Mitsubishi Gas Chemical) 100 parts Silicon oil KF-50 (Shin-Etsu Chemical Co., Ltd.) 0.02 parts 1,3-Dioxolane 300 parts Tetrahydrofuran 450 parts Ionette MS-400 (manufactured by Sanyo Chemical Co., Ltd.) 0.7 parts The above composition was dissolved to prepare a coating liquid 2 for a charge transport layer. The charge transport layer coating solution 2 thus obtained was applied onto the charge generation layer and dried at 135 ° C. for 20 minutes to form a charge transport layer having a thickness of 18 μm, thereby preparing a photoreceptor. The photoreceptor 2 is assumed.

Preparation of Photoconductor 3 <Intermediate Layer Coating Solution 3> (UCL-3)
Aluminum oxide (number average primary particle size 50 nm) 80 parts Oil-free alkyd resin (Beckolite M6805-40 (solid content 40 mass%, hydroxyl value 20): manufactured by Dainippon Ink and Chemicals, Inc.) 15 parts Block isocyanate resin (Bernock B3 -867 (solid content 70% by mass): manufactured by Dainippon Ink & Chemicals, Inc. 20 parts Methyl ethyl ketone 100 parts The above composition UCL-3 is dispersed for 72 hours with a ball mill, and this liquid is used to coat on an aluminum support. And it dried at 150 degreeC for 20 minute (s), and produced the intermediate | middle layer with a film thickness of 4.0 micrometers.

<Coating liquid 3 for charge generation layer> (CGL-3)
Charge generation material: τ-type metal-free phthalocyanine (TPA-891: manufactured by Toyo Ink Co.)
12 parts Charge generating material (CGM-2) 24 parts Cyclohexanone 330 parts The above composition was dispersed in a ball mill for 216 hours. After completion of the dispersion, a resin solution prepared by dissolving 6 parts of polyvinyl butyral (XYHL: manufactured by UCC) in 850 parts of methyl ethyl ketone and 1100 parts of cyclohexanone was added and dispersed for 3 hours to prepare a coating solution 3 for charge generation layer. This was applied to the intermediate layer drum and dried at 130 ° C. for 10 minutes to prepare a charge generation layer having a thickness of 0.2 μm.
<Coating liquid 3 for charge transport layer> (CTL-3)
Charge transport material (CT2-4) 8 parts Polycarbonate (Z type: viscosity average molecular weight 50,000) 10 parts Silicone oil (KF-50: manufactured by Shin-Etsu Chemical Co., Ltd.) 0.002 parts Tetrahydrofuran 100 parts A coating solution 3 for charge transport layer was prepared. This was applied onto the charge generation layer and dried at 130 ° C. for 20 minutes to form a charge transport layer having a thickness of 30 μm, thereby preparing a photoreceptor. The photosensitive member 3 is used.

Preparation of photoconductor 4 <Interlayer coating solution 4> (UCL-4)
A photoconductor 4 was produced in the same manner as the photoconductor 1 except that the intermediate layer was changed as follows.

Titanium oxide (methyl hydrogen polysiloxane-treated rutile type titanium oxide: number average primary particle size 400 nm) 80 parts Oil-free alkyd resin (Beckolite M6805-40 (solid content 40% by mass, hydroxyl value 20): Dainippon Ink & Chemicals, Inc. 15 parts Block isocyanate resin (Bernock B7-887-50 (solid content 60% by mass): manufactured by Dainippon Ink & Chemicals, Inc.) 20 parts Methyl ethyl ketone 100 parts The above composition is dispersed in a ball mill for 72 hours, and an intermediate layer coating solution This was applied to an aluminum base tube using this, and dried at 150 ° C. for 20 minutes to prepare an intermediate layer having a thickness of 1.0 μm.
Photoconductor 5
<Intermediate layer coating solution 5> (UCL-5)
Polyvinyl butyral resin: PVB (ESREC BM-S, manufactured by Sekisui Chemical Co., Ltd.) 3 parts n-butyl alcohol 100 parts Titanium oxide (alumina silica-coated rutile titanium oxide: number average primary particle size 90 nm)
30 parts The above composition was dispersed in a sand grind mill for 2 hours to obtain a mill base. In this mill base,
n-Butyl alcohol 40 parts Organic zirconium compound (acetylacetone zirconium butyrate) 20 parts Organic silane compound mixture (γ-aminopropyltrimethoxysilane) 10 parts were additionally mixed and stirred to obtain an intermediate layer coating solution. This was applied onto an aluminum base tube and dried at 150 ° C. for 20 minutes to produce an intermediate layer having a thickness of 1.0 μm.

<Coating liquid 4 for charge generation layer> (CGL-4)
Charge generation material: V-type hydroxygallium phthalocyanine 15 parts Polyvinyl butyral resin (ESREC, manufactured by BM-S Sekisui Chemical Co., Ltd.) 10 parts n-butyl alcohol 300 parts The above composition was dispersed in a sand mill for 4 hours. The obtained dispersion was applied onto the intermediate layer and dried to form a charge generation layer having a thickness of 0.2 μm.

<Coating liquid 4 for charge transport layer> (CTL-4)
Charge transport material (CT2-13) 4 parts Bisphenol Z polycarbonate resin (molecular weight 40,000) 6 parts Chlorbenzene 80 parts By coating and drying using the above composition, a charge transport layer with a film thickness of 20 μm is formed and photosensitive. The body was made. The photoreceptor 5 is used.

Production of Photoreceptor 6 Photoreceptor 6 was produced in the same manner as Photoreceptor 5, except that the intermediate layer was changed as follows.

<Intermediate layer coating solution 6> (UCL-6)
Polyvinyl butyral resin (ESREC BM-S, manufactured by Sekisui Chemical Co., Ltd.) 3 parts n-butyl alcohol 100 parts Titanium oxide (octyltrimethoxysilane-treated anatase-type titanium oxide: number average primary particle size 90 nm) 20 parts Zinc oxide (number average) (Primary particle size 50 nm) 10 parts The above composition was mixed and dispersed in a sand grind mill for 2 hours to obtain a mill base. In this mill base,
n-Butyl alcohol 40 parts Organozirconium compound (acetylacetonezirconium butyrate) 20 parts Organosilane compound mixture (γ-aminopropyltrimethoxysilane) 10 parts were additionally mixed and stirred to obtain an intermediate layer coating solution 6 . This was coated on an aluminum support and dried at 150 ° C. for 20 minutes to produce an intermediate layer having a thickness of 1.0 μm.

Preparation of photoconductor 7 (Comparative Example 1)
A photoconductor 7 was produced in the same manner as the photoconductor 1 except that the intermediate layer was changed as follows.

<Intermediate layer coating solution 7> (UCL-7)
Titanium oxide (methyl hydrogen polysiloxane-treated rutile type titanium oxide: number average primary particle size 50 nm) 180 parts Alcohol-soluble polyamide resin (CM-8000, nylon 6/66/610/12 copolymer manufactured by Toray Industries, Inc.) 40 parts Methanol 500 parts Butanol Dissolve in 125 parts of a solution while heating at 50 ° C., and the resulting liquid is applied as an intermediate layer coating solution 7 onto an aluminum support. Partial drying was performed to prepare an intermediate layer having a thickness of 3.0 μm.

Preparation of photoconductor 8 (Comparative Example 2)
A photoconductor 8 was produced in the same manner as the photoconductor 1 except that the thickness of the intermediate layer was changed to 6.5 μm.

Preparation of photoconductor 9 (Comparative Example 3)
A photoconductor 9 was produced in the same manner as the photoconductor 1 except that the thickness of the intermediate layer was changed to 0.3 μm.

Production of photoconductor 10 (Comparative Example 4)
A photoconductor 10 was produced in the same manner as the photoconductor 1 except that the number average primary particle size of the titanium oxide in the intermediate layer was changed to 4 nm.

Production of photoconductor 11 (Comparative Example 5)
A photoconductor 11 was produced in the same manner as the photoconductor 1 except that the particle size of the titanium oxide in the intermediate layer was changed to 600 nm.

  The structural formulas of charge generating substances CGM-1 and CGM-2 used in the production of the above photoreceptor are shown below.

  In addition, Table 1 below shows the composition of the intermediate layers of the photoreceptors 1 to 11.

Evaluation 1
Counter the resulting photoreceptor with a commercially available full-color multifunction device 8050 (manufactured by Konica Minolta Business Technologies Co., Ltd.) (tandem-type full-color multifunction device 8050 using intermediate transfer and reversal development at a process speed of 220 mm / sec). It was mounted on the development system and the following process conditions) and image evaluation was performed. An original image having a white background portion, a solid black portion, a solid image portion of red, green, and blue, and a character image portion was copied and evaluated on A4 paper. Specifically, a total of 300,000 sentence copy images were printed and evaluated at the start and every 5000 sheets. Evaluation items and evaluation criteria are shown below.

Evaluation condition Photoconductor linear velocity: 220 mm / sec
Magnetic brush bite depth (Bsd); 0.30mm
Development gap (Dsd); 0.28 mm
AC component of development bias (Vac); 1.0 KVp-p
Peripheral speed ratio of developing sleeve to photoreceptor (Vs / Vopc); 2.0
DC component of development bias (Vdc); -500V
Difference between the surface potential V0 of the photoreceptor and the DC component Vdc of the developing bias (| V0−Vdc |); 200V
Frequency: 3kHz and 9kHz
Duty: 50% rectangular wave For image evaluation, printing was performed at room temperature.

Image evaluation: Reduced density at tip end A halftone image of 300,000 sheets was prepared and evaluated.

  (Double-circle): Generation | occurrence | production of density | concentration fall of a front-end | tip part is not seen, but a halftone image is reproduced clearly (very good).

  ○: The halftone image is clearly reproduced, but there is a drop in the tip density of less than 0.04 in reflection density (no problem in practical use).

  X: The half-tone image has a drop in tip density of 0.04 or more in reflection density (practically problematic).

At the start of fogging, a densitometer “RD-918” (manufactured by Macbeth) was used for the 300,000th sheet, and the fog density was measured at a relative density where the reflection density of A4 paper was 0.000.
A: Less than 0.010 (very good)
○: 0.010 or more and less than 0.020 (a level that causes no problem in practice)
×: 0.020 or more (problematic problems)
Color reproducibility The color of the solid image portion of the secondary color (red, blue, green) in each of the Y, M, and C toners of the first image and the 100th image is measured by “Macbeth Color-Eye 7000”, and CMC The color difference between the first and 100th sheets of each solid image was calculated using the (2: 1) color difference formula.

A: Color difference is 3 or less (good)
×: Color difference is greater than 3 (practical problem and impractical)
Worm-like unevenness A halftone image of 10,000 sheets was observed with a magnifying glass (× 20), and the presence or absence of worm-like unevenness was observed and evaluated.

  A: Unevenness is not observed.

  A: There is no problem although there is some unevenness.

  X: There is unevenness. Visually wavy unevenness is practically problematic.

Sharpness Evaluated by crushing 10,000 characters. 3-point and 5-point character images were formed and evaluated according to the following criteria.

◎: 3 points and 5 points are clear and easily readable ○: 3 points are partially unreadable 5 points are clear and easily readable ×: 3 points are almost unreadable The results are shown in Table 2.

  As is clear from Table 2, in the image evaluation produced by the counter development method, the cured resin contains inorganic particles having a number average primary particle size of 5 to 500 nm and a film thickness of 0.5 to 6.0 μm. Photoconductors 1 to 6 having good properties in all evaluation items of tip density reduction, fogging, color reproducibility, sharpness, and worm-like unevenness, polyamide was used as the binder resin. The photoreceptor 7 has a reduced density at the tip, and sharpness and worm-like unevenness are not solved. The photosensitive member 8 having a film thickness of 6.5 μm causes a decrease in density at the tip portion and a decrease in image density, and the photosensitive member 9 having a film thickness of 0.3 μm generates fog and has a worm-like unevenness. The photoconductor 10 having an average particle diameter of titanium oxide of 4 nm has deteriorated dispersibility of the titanium oxide, causing fogging and a decrease in the concentration of the tip, and also reducing the sharpness. Further, the photoconductor 11 using titanium oxide having an average particle diameter of 600 nm is fogged and the color reproducibility is also deteriorated.

Production of Photoreceptor 21 to Photoreceptor 26 In production of Photoreceptor 1 to Photoreceptor 26, the charge transport material CT2-3 is changed to CT1-27, CT2-4 is changed to CT1-7, and CT2-13 is changed to CT1-51. Photoconductors 21 to 26 were produced in the same manner except that.

  As a result of evaluating the photoconductors 21 to 26 in the same manner as the photoconductors 1 to 6, the photoconductors 21 to 26 obtained almost the same evaluation results as the corresponding photoconductors 1 to 6.

Evaluation 2 (comparative example evaluation)
The evaluation performed in Evaluation 1 was evaluated by a parallel development system in which the traveling directions of the photosensitive member and the developing sleeve proceed in parallel.

Evaluation condition Photoconductor linear velocity: 220 mm / sec
Development sleeve linear velocity: 400 mm / sec, reversal development method As a result, the difference between the example of evaluation 1 and the comparative example does not appear clearly, and in all of the examples and comparative examples, the decrease in tip concentration and the occurrence of fogging are observed. Although not, an electrophotographic image in which the image density was lowered and the color image was also reduced in saturation was obtained.

It is a figure which shows the cross section of the developing device of the counter direction developing method. 1 is a diagram showing an example of a schematic configuration of an electrophotographic apparatus having a process cartridge having an organic photoreceptor according to the present invention. 1 is a schematic configuration diagram of a printer as an example of an image forming apparatus of the present invention. FIG. 2 is a schematic configuration diagram of a modification example of a printer that is an example of the image forming apparatus of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Organic photoreceptor 12 Axis 13 Primary charging means 14 Exposure light 15 Developing means 16 Transfer means 17 Transfer material 18 Fixing means 19 Cleaning means 20 Pre-exposure means 21 Process cartridge container 22 Guide means 101 Organic photoreceptor 102 Developing apparatus 110 Developing container 118 Replenishment port 120 Developing sleeve 121 Magnet 122 Developing blade 123 First conveying member 124 Second conveying member 128 Screw blade 130 Plate-like protrusion 140 Partition N1 Developing magnetic pole N2 Second developing magnetic pole S1 Pumping magnetic pole S2 Third conveying magnetic pole S3 First conveying magnetic pole P Developer drop position Q Pumping position

Claims (16)

An electrostatic latent image is formed on the organic photoconductor, a developing brush made of a developer containing toner is formed on a cylindrical developing sleeve, the developing brush is brought into contact with the organic photoconductor, and the electrostatic latent image is formed. In the image forming method for developing a toner image, the organic photoreceptor has a photosensitive layer on an electrically conductive support through an intermediate layer, and the intermediate layer has a number average primary particle size of 5 to 500 nm in a cured resin. The electrostatic latent image is visualized as a toner image while the developing sleeve is rotated in the counter direction with respect to the rotation direction of the organic photoreceptor. An image forming method. The image forming method according to claim 1, wherein the inorganic particles are a metal oxide. The image forming method according to claim 1, wherein the inorganic particles are titanium oxide. The image forming method according to claim 1, wherein the inorganic particles are aluminum oxide. The image forming method according to claim 1, wherein the inorganic particles are surface-treated. The image forming method according to claim 1, wherein the cured resin is a reaction product of a melamine resin and an oil-free alkyd resin. The image forming method according to claim 1, wherein the cured resin is a reaction product of an oil-free alkyd resin and a blocked isocyanate. The image forming method according to claim 1, wherein the curable resin is a reaction product of an organometallic compound and a silane coupling agent. 9. The organic photoconductor of claim 1, wherein the organic photoconductor is a laminated organic photoconductor in which at least a charge generation layer, a charge transport layer, and optionally a surface layer are provided in this order on a conductive support. The image forming method according to claim 1. The image forming method according to claim 1, wherein a developing gap (Dsd) between the organic photoreceptor and the developing sleeve is 0.2 to 0.6 mm. 11. The image according to claim 1, wherein a biting depth (Bsd) of the magnetic brush in a developing region between the organic photoreceptor and the developing sleeve is 0.0 to 0.8 mm. Forming method. The image forming method according to claim 1, wherein a peripheral speed ratio (Vs / Vopc) between the developing sleeve and the organic photoreceptor is 1.2 to 3.0. The difference | V0−Vdc | between the surface potential V0 of the organic photoreceptor and the DC component Vdc of the developing bias applied to the developing sleeve is 100 to 300V, the DC component Vdc of the developing bias is −300V to −650V, The image forming method according to claim 10, wherein the AC component Vac is 0.5 to 1.5 kV, the frequency is 3 to 9 kHz, the duty is 45 to 70%, and a rectangular wave. An electrostatic latent image is formed on the organic photoreceptor, a developing brush is formed with a developer containing toner on a cylindrical developing sleeve, the developing brush is brought into contact with the organic photoreceptor, and the electrostatic latent image is formed. A plurality of image forming units each having a developing unit that visualizes a toner image and a transfer unit that transfers the toner image formed on the organic photosensitive member to a transfer medium are provided, and coloring is performed for each of the plurality of image forming units. In the image forming method in which each color toner image is formed on an organic photoreceptor using the changed toner, and each color toner image is transferred from the organic photoreceptor to a transfer medium to form a color image, the organic photoreceptor is conductive. A photosensitive layer is provided on the support via an intermediate layer, and the intermediate layer contains inorganic particles having a number average primary particle size of 5 to 500 nm in the cured resin and has a thickness of 0.5 to 6.0 μm. In the direction of rotation of the organophotoreceptor Image forming method characterized by, and the electrostatic latent image into a toner image while rotating the developing sleeve in the counter direction. An electrostatic latent image is formed on the organic photoconductor, a developing brush made of a developer containing toner is formed on a cylindrical developing sleeve, the developing brush is brought into contact with the organic photoconductor, and the electrostatic latent image is formed. In the image forming apparatus having a developing unit that visualizes a toner image, the organic photoreceptor has a photosensitive layer through an intermediate layer on a conductive support, and the intermediate layer is a number average primary particle in a cured resin. It contains inorganic particles having a diameter of 5 to 500 nm and a film thickness of 0.5 to 6.0 μm, and the electrostatic latent image is converted into a toner image while rotating the developing sleeve in a counter direction with respect to the rotation direction of the organic photoreceptor. An image forming apparatus characterized in that the image is visualized. An electrostatic latent image is formed on a cylindrical organic photoreceptor, an electrostatic latent image is formed on a cylindrical current organic photoreceptor carrying a developer containing toner, and toner is contained in a cylindrical developing sleeve. Forming a developing brush by a developing agent, bringing the developing brush into contact with an organic photoreceptor, and developing the electrostatic latent image into a toner image; and a toner image formed on the organic photoreceptor as a transfer medium A plurality of image forming units having transfer means for transferring to each other are provided, each color toner image is formed on an organic photoreceptor using toner whose color is changed for each of the image forming units in the plurality of arrays, and each color toner image In an image forming apparatus for forming a color image by transferring a toner from an organic photoreceptor to a transfer medium, the organic photoreceptor has a photosensitive layer through an intermediate layer on a conductive support, and the intermediate layer is contained in a cured resin. Number average primary particle size 5-500n The electrostatic latent image is visualized as a toner image while the developing sleeve is rotated in the counter direction with respect to the rotation direction of the organic photoreceptor. An image forming apparatus.

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