JP2006154771A - Image forming method, image forming apparatus and organic photoreceptor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming method and an image forming apparatus in which fogging liable to occur in a counter developing system and occurrence of image unevenness due to density lowering of a peripheral part are prevented, and by which an electrophotographic image having high image density and good color reproducibility can be formed, and to provide an organic photoreceptor. <P>SOLUTION: The image forming method comprises: forming an electrostatic latent image on the organic photoreceptor; forming a developing brush with a developing agent containing toner on a cylindrical developing sleeve; and bringing the developing brush in contact with the organic photoreceptor so as to visualize the electrostatic latent image into a toner image. The organic photoreceptor has a photosensitive layer on a conductive support member by way of an intermediate layer, wherein the intermediate layer contains n-type conductive particles having a number average primary order particle size of 5-500 nm in a cured resin and has a thickness of >6 to 30 μm, and the electrostatic latent image is visualized into the toner image while rotating the developing sleeve in a direction counter to the rotating direction of the organic photoreceptor. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming method, an image forming apparatus, and an organic photoreceptor used for forming an electrophotographic image, and more specifically, an image forming method used for forming an electrophotographic image used in the field of copying machines and printers, The present invention relates to an image forming apparatus and an organic photoreceptor (hereinafter also simply referred to as a photoreceptor).

  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 photoconductors 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 the mainstream. For example, a charge generation layer and a charge transport layer are formed on an electrically conductive support via an intermediate layer. Laminated type photoreceptors are 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. In order to improve the image quality of the electrophotographic image, a technique for forming a fine dot image by forming a fine latent image on an organic photoreceptor using an exposure light source having a small spot diameter has been developed. For example, a method of forming a high-definition latent image on an organic photoreceptor using a light source having a spot diameter of 4000 μm ² or less is known (Patent Document 2). An organic photosensitive member capable of forming a high-density and uniform latent image by the dot exposure even when high-density dot exposure is performed with such a small spot diameter, and a development system capable of reproducing the latent image as a toner image. The configuration is not yet fully achieved.

  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) that proceeds 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.
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, the counter development method tends to cause worm-like unevenness more easily than the parallel development method, and is particularly noticeable under high temperature and high humidity. 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.

  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.

That is, it is presumed to be related to the contrast of the electrostatic latent image formed on the organic photoreceptor and the production of reversely charged toner due to the friction between the organic photoreceptor and the developer.
JP 2004-133018 A JP-A-8-272197

  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 object is to provide an image forming method and an image forming apparatus, and to provide an organic photoreceptor applied to the image forming method.

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 the occurrence of fogging in the counter method with excellent developability, the density defect at the leading edge of the image, and the worm-like unevenness under high temperature and high humidity The present inventors have found that it is effective to provide a 6-30 μm intermediate layer containing N-type semiconductive particles in a cured resin with improved charge carrier rectification on the organic photoreceptor.
In other words, by making the counter development method appropriate, the problem of fogging and the density defect at the front end of the image could be improved to some extent, but both the prevention of fine unevenness called worm-like unevenness and the improvement of sharpness are achieved. I couldn't do it. Therefore, as a result of intensive studies by the present inventors, the counter development method achieves the above-mentioned compatibility by using the intermediate layer of the present invention, and further improves the problem of fog generation and density defect at the front end of the image. Found that you can. The reason why it is possible to achieve both the prevention of fine unevenness failure called worm-like unevenness and the improvement of sharpness is not clear, but the N-type semiconductor particles in the intermediate layer containing the cured resin of the present invention It is speculated that the blocking ability related to the diameter has the same effect as if the development bias frequency was raised, particularly under high temperature and high humidity.

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. And an electrostatic latent image appears on the toner image while rotating the developing sleeve in the counter direction with respect to the rotation direction of the organic photoconductor. An image forming method comprising imaging.
2. 2. The image forming method as described in 1 above, wherein the N-type semiconductor particles are titanium oxide particles.
3. 2. The image forming method as described in 1 above, wherein the N-type semiconductor particles are zinc oxide particles.
4). 4. The image forming method according to any one of items 1 to 3, wherein the N-type semiconductor particles are surface-treated.
5. 5. The image forming method according to any one of 1 to 4, wherein the curable resin is a melamine resin.
6). 6. The image forming method according to any one of 1 to 5, wherein the organic photoreceptor is a laminated organic photoreceptor in which at least a charge generation layer and a charge transport layer are provided in this order on an intermediate layer. .
7). 7. The image forming method as described in 6 above, wherein the charge generation layer contains a phthalocyanine pigment as a charge generation material.
8). 8. The image forming method as described in 7 above, wherein the phthalocyanine pigment is a titanyl phthalocyanine pigment or a gallium phthalocyanine pigment.
9. 9. The image forming method according to any one of 1 to 8, wherein a developing gap (Dsd) between the organic photoreceptor and the developing sleeve is 0.2 to 0.6 mm.
10. 10. The image formation as described in any one of 1 to 9 above, wherein a penetration 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.
11. 11. The image forming method as described in 1 to 10 above, wherein a peripheral speed ratio (Vs / Vopc) between the developing sleeve and the organic photoreceptor is 1.2 to 3.0.
12 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 any one of 9 to 11, 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.
13. 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 photoconductor to a transfer medium are arranged, and the coloration is changed for each of the plurality of image forming units. In the image forming method of forming each color toner image on the organic photoconductor using the toner and transferring the color toner image from the organic photoconductor to a transfer medium to form a color image, the organic photoconductor is a conductive support. The intermediate layer has a photosensitive layer on the body, and the intermediate layer contains N-type semiconductor particles having a number average primary particle size of 5 to 500 nm in the cured resin and has a film thickness of more than 6 μm and not more than 30 μm. Of the organophotoreceptor An image forming method comprising developing an electrostatic latent image into a toner image while rotating a developing sleeve in a counter direction with respect to a rotation direction.
14 14. An image forming apparatus using the image forming method according to any one of 1 to 13.
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 rotation direction of the organic photoreceptor In contrast, in an organic photoreceptor used in an image forming method in which an electrostatic latent image is visualized as a toner image while rotating a developing sleeve in a counter direction, the photosensitive layer has an intermediate layer on a conductive support. And the intermediate layer contains N-type semiconductive particles having a number average primary particle size of 5 to 500 nm in a cured resin, and has a film thickness of more than 6 μm and 30 μm or less.

  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. Also, an organic photoreceptor used in the image forming method can be provided.

  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 N-type semiconducting particles having a number average primary particle size of 5 to 500 nm and has a film thickness of more than 6 μm and not more than 30 μm. The developing sleeve is rotated counterclockwise with respect to the rotation direction of the organic photoreceptor. The electrostatic latent image is visualized as a toner image.

  Since the image forming method of the present invention has the above-described configuration, it is possible to prevent the occurrence of fogging, the density defect at the tip, and the occurrence of worm-like unevenness, which are easily generated by the counter development method, and a high-quality digital image or color image can be obtained. Can be provided.

  The organic photoreceptor used in the image forming method of the present invention will be described. The organic photoreceptor of the present invention has a photosensitive layer through an intermediate layer on a conductive support, and the intermediate layer contains N-type semiconductor particles having a number average primary particle size of 5 to 500 nm in a cured resin. And the film thickness is larger than 6 μm and 30 μm or less.

  Since the organic photoconductor has the above-described configuration, it is possible to prevent the occurrence of fogging, the density defect at the tip, and the occurrence of worm-like unevenness, which are likely to occur due to the counter development method. Can be provided. 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 of 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 of the present invention may be a sheet-like conductive support, but a cylindrical conductive support is more preferably used.

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

  In the organic photoreceptor of the present invention, the effect 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 photosensitive member in the image forming process tends to be high, and image unevenness and fog are likely to occur in the counter development method.

Intermediate layer In the present invention, an intermediate layer is provided between the conductive support and the photosensitive layer. The intermediate layer contains N-type semiconductor particles. The N-type semiconductive particle means a particle whose main charge carrier is an electron. That is, since the main charge carrier is an electron, the intermediate layer containing the N-type semiconductor particles in the insulating binder efficiently blocks hole injection from the conductive support, and the photosensitive layer. It has a property of exhibiting transportability with respect to electrons from.

As the N-type semiconductor particles, titanium oxide (TiO ₂ ) and zinc oxide (ZnO) are preferable, and titanium oxide is particularly preferably used.

  The number average primary particle size of the N-type semiconductor 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 it is less than 5 nm, the N-type semiconductive particles tend to aggregate in the binder, the uniformity of the intermediate layer is insufficient, the potential characteristics of the photoreceptor are likely to become 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 N-type semiconductive particles is magnified 10,000 times by observation with a transmission electron microscope, and 100 particles are randomly observed as primary particles. It is measured as the number average diameter of the ferret diameter.

  The titanium oxide particles have anatase, rutile, brookite, and amorphous forms as crystal forms. Among them, the rutile form titanium oxide pigment or the anatase form titanium oxide pigment has a rectifying property of charge passing through the intermediate layer. In other words, the electron mobility is increased, the charging potential is stabilized, the residual potential is prevented from increasing, and a high-density dot image can be formed. preferable.

  N-type semiconductive particles are preferably surface-treated with a polymer containing methylhydrogensiloxane units. The molecular weight of the polymer containing the methyl hydrogen siloxane unit is 1000 to 20000, and the surface treatment effect is high. As a result, the rectifying property of the N-type semiconductor particles is improved, and the N-type semiconductor particles are contained. By using the intermediate layer, 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.

  Further, the N-type semiconductive particles may be those 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.

  Further, prior to the surface treatment of the methylhydrogensiloxane copolymer or the reactive organosilicon compound, the N-type semiconductive particles may be subjected to an inorganic surface treatment such as alumina or silica.

  Prior to the surface treatment of the N-type semiconductor particles, at least one kind of surface treatment selected from alumina, silica, and zirconia may be performed.

  The alumina treatment, silica treatment, and zirconia treatment are treatments for precipitating alumina, silica, or zirconia on the surface of anatase-type titanium oxide. The alumina, silica, and zirconia deposited on these surfaces are water of alumina, silica, zirconia Japanese products are also included.

  The treatment of alumina and silica may be performed simultaneously, but it is particularly preferable to perform the alumina treatment first and then the silica treatment. Further, the amount of treatment of alumina and silica when treating alumina and silica is preferably higher than that of alumina.

  The intermediate layer coating solution prepared for forming the intermediate layer used in the present invention is composed of a binder resin, a dispersion solvent and the like in addition to the N-type semiconductive particles such as the surface-treated titanium oxide.

  The ratio of the N-type semiconductive particles in the intermediate layer is preferably 1.0 to 2.0 times in terms of the volume ratio of the intermediate layer to the binder resin (when the volume of the binder resin is 1). By using the N-type semiconducting particles of the present invention at such a high density in the intermediate layer, the rectifying property of the intermediate layer is increased, and no increase in residual potential or transfer memory occurs even when the film thickness is increased. Therefore, it is possible to effectively prevent black spots and to form a good organic photoreceptor with a small potential fluctuation. Further, such an intermediate layer preferably uses 100 to 200 parts by volume of N-type semiconductive particles with respect to 100 parts by volume of the binder resin.

  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, a binder resin capable of forming an intermediate layer that reacts with a hydroxyl group of inorganic particles in the intermediate layer, a hydroxyl group on the surface of the conductive support, etc., is less dependent on temperature and humidity and hardly causes image unevenness. It is preferable to use it. 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. Melamine resins and phenol resins are also preferably used.

  When a melamine resin or a phenol resin is used, a combination system with polyvinyl butyral (= PVB) or an oil-free alkyd resin is preferable instead of each 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.

  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 N-type semiconductor 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.

  In the present invention, the thickness of the intermediate layer is preferably set in the range of 6 μm to 30 μm, and more preferably in the range of 7 to 25 μm. If the film thickness of the intermediate layer is too thin, the blocking ability is insufficient, the cracks are not sufficiently prevented from occurring, and the effect of worm-like unevenness under high temperature and high humidity is lost. On the contrary, if the film thickness of the intermediate layer exceeds 30 μm, the smoothness of the film surface due to uneven curing of the cured resin is lost, the sensitivity of the photoreceptor is lowered, the residual potential is increased, and fogging and density reduction are caused.

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 the phthalocyanine pigment is used in the CGM, the effect of the present invention is remarkably exhibited. Organic photoreceptors using titanyl phthalocyanine pigments, gallium phthalocyanine pigments, etc. as charge generation materials tend to vary in potential characteristics. However, when the intermediate layer according to the present invention is used, the potential variation is improved and the counter development method is used. Even with this image forming method, it is possible to prevent the occurrence of fogging and to prevent the occurrence of a partial decrease in density at the leading edge of the image.

  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 of 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 transporting material of 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 (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.)
Below, the specific example of a compound of General formula (1) is shown.

  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. Typical examples include the following compound groups.

  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 fluororesin fine particles in the resurface layer, the transferability of the toner image formed on the surface of the photoreceptor to recording paper 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 of the present invention will be described. FIG. 2 shows a schematic configuration of an electrophotographic apparatus having a process cartridge having the organic photoreceptor of the present invention.

  In FIG. 2, reference numeral 11 denotes a drum-shaped organic photoreceptor of the present invention, which is driven to rotate at a predetermined peripheral speed in the direction of an arrow about a shaft 12. 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.

  The transfer material 17 that has received the transfer of the toner image is separated from the surface of the organic photoreceptor, introduced into the image fixing means 18, and subjected to image fixing to be 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 an 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 on the intermediate transfer belt 58 and intermediately transferred 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 onto the transfer paper P at a time 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.

  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. The drum cleaning unit 85, the charge removal lamp 83, and the charging roller 84 for uniformly charging the drum are also provided for each color. 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, 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.

Preparation of Photoconductor 1 <Intermediate Layer Coating Solution 1> (UCL-1)
Zinc oxide particles (number average primary particle size: 10 parts of coupling agent N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane and 200 parts of toluene are mixed with 100 parts of zinc oxide of 50 nm and stirred. Refluxed for 2 hours, and then toluene was distilled off and heat-treated at 135 ° C. for 2 hours) 33 parts Melamine resin (Uban 20SE-60) 6 parts n-butyl alcohol 25 parts Butyral resin: PVB (BM-1, Sekisui Chemical Co., Ltd.) 5 parts Silicone ball (Tospearl 120, manufactured by Toshiba Silicone) 3 parts Leveling agent (Silicone oil SH29PA, manufactured by Toray Dow Corning Silicone)
0.01 part The above composition was prepared and subjected to a dispersion treatment for 2 hours in a sand mill to obtain an intermediate layer coating solution 1. Further, the above coating solution was applied to the outer peripheral surface of a cylindrical aluminum substrate having a diameter of 30 mm and a wall thickness of 1 mm by dip coating, followed by drying and curing at 150 ° C. for 30 minutes to form an intermediate layer having a thickness of 7 μm. .

<Coating liquid 1 for charge generation layer> (CGL-1)
Charge generation material: gallium chloride phthalocyanine (X-ray diffraction spectrum Bragg angle (2θ ± 0.2 °) using CuKα ray is at least 7.4 °, 16.6 °, 25.5 °, 28.3 °) 15 parts vinyl chloride-vinyl acetate copolymer resin (VMCH, manufactured by Nihon Unicar) 10 parts n-butyl alcohol 300 parts The above composition is prepared, dispersed in a sand mill for 4 hours, and charged. A coating solution 1 for generating layer was obtained. This coating solution was dip-coated on the intermediate layer and dried to form a charge generation layer having a thickness of 0.2 μm.
<Coating liquid 1 for charge transport layer>
Charge transport material (CT1-27) 4 parts Bisphenol Z polycarbonate resin (molecular weight: 40,000) 6 parts Chlorbenzene 80 parts The above composition was prepared to obtain a charge transport layer coating solution. This coating solution was applied onto the charge generation layer and dried at 130 ° C. for 40 minutes to form a charge transport layer having a thickness of 25 μm. Thus, photoreceptor 1 was obtained.

Production of Photoreceptor 2 Photoreceptor 2 was produced in the same manner as Photoreceptor 1 except that the thickness of the intermediate layer was changed to 20 μm and the charge transport material was changed from CT1-27 to CT1-7.

Production of Photoreceptor 3 Photoreceptor 3 was produced in the same manner as Photoreceptor 1 except that the thickness of the intermediate layer was changed to 15 μm and the charge transport material was changed from CT1-27 to CT1-21.

Production of Photoreceptor 4 Photoreceptor 4 was produced in the same manner as Photoreceptor 1 except that the thickness of the intermediate layer was changed to 30 μm and the charge transport material was changed from CT1-27 to CT1-51.

Preparation of Photoreceptor 5 <Intermediate Layer Coating Solution 2> (UCL-2)
Titanium oxide (100 parts of titanium oxide having a number average primary particle size: 50 nm is stirred and mixed with 500 parts of toluene, and 15 parts of a coupling agent γ-methacrylopropyltrimethoxysilane is added and stirred for 5 hours. At 120 ° C. for 2 hours. Heat treated (baked), and further heat treated at 190 ° C. for 2 hours and coated) 35 parts Blocked isocyanate (Sumijoule 3175, manufactured by Sumitomo Bayer Urethane Co., Ltd.)
15 parts Butyral resin (BM-1, manufactured by Sekisui Chemical Co., Ltd.) 6 parts Methyl ethyl ketone 44 parts The above composition was prepared and subjected to dispersion treatment for 2 hours with a sand mill using 1 mmφ glass beads to obtain a dispersion. Further, 0.005 parts by mass of dioctyltin dilaurate as a catalyst and 0.01 parts by mass of silicone oil (SH29PA, manufactured by Toray Dow Corning Silicone) are added to the obtained dispersion to obtain a coating solution 2 for an intermediate layer. It was. This coating solution was applied to the outer peripheral surface of an aluminum substrate (diameter 30 mm, wall thickness 1 mm) by a dip coating method, followed by drying and curing at 160 ° C. for 100 minutes. In this way, an intermediate layer having a thickness of 20 μm was formed.
<Coating liquid 2 for charge generation layer> (CGL-2)
Charge generation material: titanyl phthalocyanine pigment (having a maximum diffraction peak at 27.3 ° position of Bragg angle (2θ ± 0.2 °) of X-ray diffraction spectrum using CuKα ray)
15 parts vinyl chloride-vinyl acetate copolymer resin (VMCH, manufactured by Nihon Unicar) 10 parts n-butyl alcohol 300 parts The above composition is dispersed in a sand mill for 4 hours using 1 mmφ glass beads, and used for a charge generation layer. A coating solution was obtained. This coating solution was dip-coated on the intermediate layer and dried to form a charge generation layer having a thickness of 0.2 μm. The charge transport layer coating solution 1 used in the photoreceptor 1 is coated on the charge generation layer and dried at 130 ° C. for 40 minutes to form a 25 μm-thick charge transport layer. A photoreceptor was obtained. The photoreceptor 5 is used.

Preparation of photoreceptor 6 <Interlayer coating solution 3> (UCL-3)
Titanium oxide (100 parts of titanium oxide having a number average primary particle size of 100 nm is stirred and mixed with 500 parts of toluene, and 15 parts by weight of a coupling agent γ-methacrylopropyltrimethoxysilane is added and stirred for 5 hours. Heat treatment (baking) was performed for a further 2 hours after heat treatment at 190 ° C. for 2 hours 60 parts Phenolic resin (J325: manufactured by Dainippon Ink) 15 parts Butyral resin (BM-1, Sekisui) 15 parts Methanol 20 parts Propanol 40 parts The above composition was prepared, and a dispersion was obtained by carrying out dispersion treatment with a sand mill for 2 hours using 1 mmφ crow beads. Furthermore, 0.005 part of dioctyltin dilaurate as a catalyst and 0.01 part of silicone oil (SH29PA, manufactured by Toray Dow Corning Silicone) were added to the obtained dispersion to obtain a coating solution for an intermediate layer. This coating solution was applied to the outer peripheral surface of a cylindrical aluminum substrate (diameter 30 mm, wall thickness 1 mm) by a dip coating method, followed by drying and curing at 160 ° C. for 100 minutes. In this way, an intermediate layer having a thickness of 20 μm was formed.
<Coating liquid 3 for charge generation layer> (CGL-3)
Charge generation material: hydroxygallium phthalocyanine (X-ray diffraction spectrum Bragg angle (2θ ± 0.2 °) using Cu-Kα rays is at least 7.3 °, 16.0 °, 24.9 °, 28.0) 15 parts vinyl chloride-vinyl acetate copolymer resin (VMCH, manufactured by Nihon Unicar) 10 parts n-butyl alcohol 300 parts The above composition was prepared and 1 mmφ glass beads were used. Dispersion was performed for 4 hours in a sand mill to obtain a coating solution for charge generation layer. This coating solution was dip-coated on the intermediate layer and dried to form a charge generation layer having a thickness of 0.2 μm.
The charge transport layer coating solution 1 used in the photoreceptor 1 is applied onto the charge generation layer, and dried at 130 ° C. for 40 minutes to form a charge transport layer having a thickness of 25 μm. Got.

Production of Photoreceptor 7 Photosensitive material except that the average number of titanium oxides used in (UCL-3) of Photoreceptor 1 was changed from 100 nm to 15 nm <Interlayer Coating Solution 4> (UCL-4). In the same manner as the body 6, a photoreceptor 7 was produced.

Production of Photoconductor 8 Photoconductor 8 was produced in the same manner as photoconductor 6 except that the intermediate layer was changed as follows.
<Intermediate layer coating solution 5> (UCL-5)
Titanium oxide (100 parts of titanium oxide having a number average primary particle size of 8 nm is stirred and mixed with 500 parts of toluene, 15 parts of coupling agent γ-methacrylopropyltrimethoxysilane is added and stirred for 5 hours. Heat treatment at 120 ° C. for 2 hours. 60 parts Blocked isocyanate (Sumidule 3175, manufactured by Sumitomo Bayer Urethane Co., Ltd.)
15 parts Butyral resin (BM-1, manufactured by Sekisui Chemical Co., Ltd.) 15 parts Methyl ethyl ketone 85 parts The above composition was prepared, and dispersion treatment was performed by using a 1 mmφ crow bead for 2 hours with a sand mill. Further, 0.005 parts by mass of dioctyltin dilaurate as a catalyst and 0.01 parts by mass of silicone oil (SH29PA, manufactured by Toray Dow Corning Silicone) are added to the obtained dispersion to obtain a coating solution for an intermediate layer. It was. This coating solution was applied to the outer peripheral surface of an aluminum substrate (diameter 30 mm, wall thickness 1 mm) by a dip coating method, followed by drying and curing at 160 ° C. for 100 minutes. In this way, an intermediate layer having a thickness of 20 μm was formed.

Production of Photoreceptor 9 The photoconductor except for <Interlayer Coating Solution 6> (UCL-6) in which the number average primary particle size of titanium oxide used in (UCL-5) of Photoreceptor 8 was changed from 8 nm to 400 nm. In the same manner as in Example 8, a photoreceptor 9 was produced.

Production of photoconductor 10 (Comparative Example 1)
A photoconductor 10 was produced in the same manner as the photoconductor 1 except that the intermediate layer was changed to the following <intermediate layer coating solution 7> (UCL-7).

Zinc oxide particles (number average primary particle size: 10 parts of coupling agent N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane and 200 parts of toluene are mixed with 100 parts of zinc oxide of 50 nm and stirred. While being refluxed for 2 hours, toluene was distilled off and heat-treated at 135 ° C. for 2 hours. 180 parts Alcohol-soluble polyamide resin (CM-8000 manufactured by Toray Industries, nylon 6/66/610/12 copolymer) 40 parts Methanol 500 parts Butanol Dissolve in a solution of 125 parts while heating at 50 ° C., and apply the resulting liquid as an undercoat layer coating liquid onto a φ30 × 340 mm aluminum drum. An intermediate layer having a thickness of 10 μm was produced by drying at 20 ° C. for 20 minutes.

Production of photoconductor 11 (Comparative Example 2)
A photoconductor 11 was produced in the same manner as the photoconductor 1 except that the thickness of the intermediate layer was changed to 5 μm.

Production of photoconductor 12 (Comparative Example 3)
A photoconductor 12 was produced in the same manner as the photoconductor 1 except that the thickness of the intermediate layer was changed to 35 μm.

Preparation of photoconductor 13 (Comparative Example 4)
The number average primary particle diameter of zinc oxide used in (UCL-1) of the photoreceptor 1 was changed from 50 nm to 4 nm <Interlayer coating solution 8> (UCL-8), and the intermediate layer thickness was changed from 7 μm to 20 μm. A photoconductor 13 was produced in the same manner as the photoconductor 1 except for changing to.

Preparation of photoreceptor 14 (Comparative Example 5)
The number average primary particle diameter of zinc oxide used in (UCL-8) of the photoconductor 13 was changed from 4 nm to 600 nm in the same manner as the photoconductor 13 except for <Interlayer coating solution 9> (UCL-9). Thus, a photoreceptor 14 was produced.

  The zinc oxide and titanium oxide used for the production of the photoreceptors 1 to 14 all showed N-type semiconductivity. The composition of the intermediate layers of the photoreceptors 1 to 14 is summarized in Table 1 below.

Evaluation 1 (Evaluation by counter development method)
The obtained photoreceptor was mounted on a commercially available full-color composite machine 8050 (manufactured by Konica Minolta Business Technologies Co., Ltd.) and modified (counter development method and modified to the following process conditions) for image evaluation. 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 conditions The process conditions of the counter development method were evaluated using the following conditions.

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 Development method: Reversal development In image evaluation, printing was performed under high temperature and high humidity (30 ° C., 80 RH%).

Image evaluation Image unevenness (reduced tip book density)
A halftone image of 300,000 sheets was produced and evaluated.

  Rank A: Generation of image unevenness is not observed, and the halftone image is clearly reproduced (very good).

  Rank B: A halftone image is clearly reproduced, but there is image unevenness with a reflection density of less than 0.04 (practically no problem).

  Rank C: Halftone image has image unevenness of 0.04 or more in reflection density (practically problematic).

Image density At the start, a densitometer “RD-918” (manufactured by Macbeth) was used for the 300,000th sheet, and the image density was measured at a relative density with the reflection density of A4 paper set to 0.000.
A: Solid black image is 1.30 or more (very good)
○: Solid black image is 1.00 or more (a level that causes no problem in practical use)
X: Solid black image less than 1.00 (practical problem)
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.

  In the table, PVB represents polyvinyl butyral (butyral resin).

  As is apparent from Table 2, in the image evaluation produced by the counter development method, the cured resin contains N-type semiconductive particles having a number average primary particle size of 5 to 500 nm and a film thickness of more than 6 μm and 30 μm or less. Photoconductors 1 to 9 having an intermediate layer exhibit good characteristics in all evaluation items such as image density, worm-like unevenness, fog, sharpness color, and reproducibility, whereas polyamide is used as a binder resin. In the photosensitive member 10, image unevenness occurs, fogging decreases, sharpness and worm-like unevenness are affected by the frequency of the AC component of the developing bias, and improvement of sharpness and prevention of worm-like unevenness are not compatible. The photoconductor 11 having a film thickness of 5 μm has worm-like unevenness, and the image density, fog, sharpness, and color reproducibility are deteriorated. Although the photoconductor 12 having a film thickness of 35 μm has solved the sharpness and worm-like unevenness, the image density and fog are lowered, and the color reproducibility is deteriorated. Further, the photoreceptor 13 having an average particle diameter of zinc oxide particles of 4 nm has deteriorated dispersibility of the zinc oxide particles and image unevenness, fogging and image density are lowered, and sharpness is also deteriorated. Further, the photoconductor 14 using zinc oxide having an average particle diameter of 600 nm has no worm-like unevenness, but image unevenness and fogging are generated, and color reproducibility and sharpness are deteriorated.

Preparation of Photoreceptor 21 to Photoreceptor 29 In preparation of Photoreceptor 1 to Photoreceptor 9, charge transport material CT1-27 is changed to CT2-2, CT1-7 is changed to CT2-11, CT1-21 is changed to CT2-17, Photoconductors 21 to 29 were produced in the same manner except that CT1-51 was changed to CT2-9.

  As a result of evaluating the photoconductors 21 to 29 in the same manner as the photoconductors 1 to 9, the photoconductors 21 to 29 obtained almost the same evaluation results as the corresponding photoconductors 1 to 9.

Evaluation 2 (Evaluation by parallel development method)
Evaluation performed in Evaluation 1 was performed on the photosensitive members 1 to 14 by a parallel development method in which the traveling directions of the photosensitive member and the developing sleeve are advanced in parallel. As a result, the difference between the example of the evaluation 1 and the comparative example did not appear clearly, and in all of the examples and comparative examples, an electrophotographic image having a reduced image density as compared with the case of the counter development system was obtained.

It is a figure which shows the cross section of the developing device of the counter direction developing method. FIG. 2 is a diagram illustrating an example of a schematic configuration of an electrophotographic apparatus having a process cartridge having the organic photoreceptor of 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 (15)

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. And an electrostatic latent image appears on the toner image while rotating the developing sleeve in the counter direction with respect to the rotation direction of the organic photoconductor. An image forming method comprising imaging. The image forming method according to claim 1, wherein the N-type semiconductor particles are titanium oxide particles. The image forming method according to claim 1, wherein the N-type semiconductor particles are zinc oxide particles. The image forming method according to claim 1, wherein the N-type semiconductor particles are surface-treated. The image forming method according to claim 1, wherein the curable resin is a melamine resin. The image forming apparatus according to claim 1, wherein the organic photoreceptor is a laminated organic photoreceptor in which at least a charge generation layer and a charge transport layer are provided in this order on an intermediate layer. Method. The image forming method according to claim 6, wherein the charge generation layer contains a phthalocyanine pigment as a charge generation material. The image forming method according to claim 7, wherein the phthalocyanine pigment is a titanyl phthalocyanine pigment or a gallium phthalocyanine pigment. The image forming method according to claim 1, wherein a development gap (Dsd) between the organic photoreceptor and the developing sleeve is 0.2 to 0.6 mm. The image according to any one of claims 1 to 9, 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, 12. The image forming method according to claim 9, 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. 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 photoconductor to a transfer medium are provided, and the coloration is changed for each of the plurality of image forming units. In the image forming method of forming each color toner image on the organic photoconductor using the toner and transferring the color toner image from the organic photoconductor to a transfer medium to form a color image, the organic photoconductor is a conductive support. The intermediate layer has a photosensitive layer on the body, and the intermediate layer contains N-type semiconductor particles having a number average primary particle size of 5 to 500 nm in the cured resin and has a film thickness of more than 6 μm and not more than 30 μm. Of the organophotoreceptor An image forming method comprising developing an electrostatic latent image into a toner image while rotating a developing sleeve in a counter direction with respect to a rotation direction. An image forming apparatus using the image forming method according to claim 1. 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 rotation direction of the organic photoreceptor In contrast, in an organic photoreceptor used in an image forming method in which an electrostatic latent image is visualized as a toner image while rotating a developing sleeve in a counter direction, the photosensitive layer has an intermediate layer on a conductive support. And the intermediate layer contains N-type semiconducting particles having a number average primary particle size of 5 to 500 nm in a cured resin and has a film thickness of more than 6 μm and 30 μm or less.

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