US 2002O197549A1 (19) United States (12) Patent Application Publication (10) Pub. No.: US 2002/0197549 A1 Sakon et al. (43) Pub. Date: Dec. 26, 2002

(54) MULTILAYER ELECTROPHOTOGRAPHIC (30) Foreign Application Priority Data PHOTORECEPTOR, AND IMAGE FORMING METHOD, IMAGE FORMING APPARATUS Nov. 10, 2000 (JP)...... 2OOO-342999 AND PROCESS CARTRIDGE USING THE Apr. 4, 2001 (JP)...... 2001-105675 PHOTORECEPTOR Oct. 4, 2001 (JP)...... 2001-308556 Publication Classification (76) Inventors: Yohta Sakon, Numazu-shi (JP); Akio (51) Int. Cl...... G03G 5/147 Kosuge, Yokohama-shi (JP); Tatsuya (52) U.S. Cl...... 430/66; 430/125; 430/67 Niimi, Numazu-shi (JP); Narihito Kojima, Numazu-shi (JP) (57) ABSTRACT An electrophotographic photoreceptor including at least an electroconductive Substrate; and a photoSensitive layer over Correspondence Address: lying the electroconductive Substrate and including at least OBLON SPIVAK MCCLELLAND MAIER & a charge generation layer, a charge transport layer, and a NEUSTADT PC protective layer including a , wherein the filler is FOURTH FLOOR dispersed in the protective layer So as to occupy an area of 1755JEFFERSON DAVIS HIGHWAY from 3 to 5% of a cross section of the protective layer; the ARLINGTON, VA 2.2202 (US) filler has particle diameter distribution having a peak at a diameter of from 0.2 to 0.3 um; and the particles of the filler (21) Appl. No.: 09/985,368 having a particle diameter of not leSS than 0.3 um occupies an area of from 10 to 30% of the area of all the filler in the (22) Filed: Nov. 2, 2001 croSS Section of the protective layer. Patent Application Publication Dec. 26, 2002 Sheet 1 of 3 US 2002/0197549 A1

FIG. 1 aus

FIG. 2 Patent Application Publication Dec. 26, 2002 Sheet 2 of 3 US 2002/0197549 A1

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15 Patent Application Publication Dec. 26, 2002 Sheet 3 of 3 US 2002/0197549 A1

US 2002/0197549 A1 Dec. 26, 2002

MULTILAYER ELECTROPHOTOGRAPHIC resistance; good chemical Stability against heat, light and PHOTORECEPTOR, AND IMAGE FORMING discharge-induced products (e.g. oZone and Nox), etc. METHOD, IMAGE FORMINGAPPARATUS AND 0017. Above all, a need exists for a photoreceptor having PROCESS CARTRIDGE USING THE a Small diameter because there is a demand for downsizing PHOTORECEPTOR electrophotographic Systems. Therefore, there is a demand for a photoreceptor having good durability against abrasion BACKGROUND OF THE INVENTION increasing in proportion to the number of copies. 0001) 1. Field of the Invention 0018 Thus, mechanical durability, which typically 0002 The present invention relates to a multilayer elec means abrasion resistance, is in Strong demand. However, trophotographic photoreceptor, and to an image forming the conventional organic photoreceptors and the electropho method, an image forming apparatus and a process cartridge tographic processes using these photoreceptors do not have for an image forming apparatus using the photoreceptor. high durability due to the low abrasion resistance of the organic materials used. In addition, the demand for a pho 0.003 2. Discussion of the Background toreceptor having good abrasion resistance has increased 0004 Electrophotographic methods such as the Carlson because the thickness of a photosensitive layer has to be proceSS and its various modified processes are widely used decreased So as to produce higher definition images. for copiers, printers, etc. AS an electrophotographic photo receptor (hereinafter referred to as a photoreceptor) for use 0019. The reason why the thickness of a photosensitive in the electrophotographic method, an organic photoreceptor layer has a particularly big influence on producing higher has been typically used because of its low cost, the ease of definition images is considered as follows. mass producing it, and because it is non-polluting. A mecha 0020. Among positive and negative carriers formed in the nism of forming an electrostatic latent image on a photore charge generation layer of a negatively chargeable multi ceptor include: layer organic photoreceptor by light irradiation, the negative carrier (an electron) is absorbed in the Substrate and the 0005 (1) irradiating a photoreceptor after it has been positive carrier (a hole) is transported through the charge charged; transport layer to the Surface of the photoreceptor to be 0006 (2) the irradiated light is then absorbed in a combined with an electron thereat, resulting in disappear charge generation material of the photoreceptor; ance of the hole. 0007 (3) the light-absorbed charge generation material 0021. Due to the disappearance, the electric field to generates a charge carrier; attract the hole gradually decreases, and the hole moves toward a non-lighted area. 0008 (4) the charge carrier is injected into a charge 0022. This is called a carrier scattering phenomenon in a transport material and transported through the charge direction of the Surface of the photoreceptor, and because of transport layer (or the photosensitive layer) along an it formation of a latent image faithful to the irradiated light electric field generated by the charge, and is prevented. This results in formation of a poor image 0009 (5) the charge carrier neutralizes the charge on having low resolution. the Surface of the photoreceptor to form an electroStatic 0023 The thickness of the charge transport layer has a latent image. big influence on the carrier Scattering phenomenon, and 0.010 Specific examples of organic photoreceptors making the thickneSS Smaller is very effective relative to include the following photoSensitive layers: maintaining good image resolution. 0011 (1) photoconductive resin layers typified by 0024. In addition, laser irradiation is different from irra diation by a halogen lamp, etc. because the incident photon polyvinylcarbazole (PVK); current speed of a laser is about 10 times as fast as that of 0012 (2) charge transfer complex type photosensitive a halogen lamp. Therefore, the density of the formed carriers layers typified by 2,4,7-trinitrofluorenon (PVK-TNF); is extremely high, and the electric field Strength of the charge generation layer decreases because charges flow into the 0013 (3) pigment dispersion type photosensitive lay charge transport layer. Thus, the carrier transport Speed is erS typified by phthalocyanine-binder, and influenced, resulting in late arrival of the carrier formed by 0014 (4) functionally-separated photosensitive layers irradiation of the center portion of the laser beam to the using a combination of a charge generation material Surface of the photoreceptor. The thus formed Space charge and a charge transport material. distribution tends to cause carrier Scattering in a direction parallel to the Surface of the photoreceptor, resulting in 0.015 Among these photoreceptors, the functionally deterioration of image resolution. Separated photoreceptors have attracted attention and come 0025 Japanese Laid-Open Patent Publication No. into practical use. 57-30846 discloses a method for improving abrasion resis 0016 Various organic photoreceptors have been devel tance of an organic photoreceptor, which includes a protec oped. However, in order to make a good photoreceptor tive layer including a filler formed from a metal or a metal requires good electrophotographic properties Such as high oxide. The object of this method is to increase the transpar Sensitivity, high potential, high potential retainability, good ency of the protective layer and prevent an increase of potential Stability, low residual potential and proper spectral residual potential by using a filler having an average particle properties, good mechanical durability Such as high abrasion diameter of not greater than 0.3 um. In addition, Japanese US 2002/0197549 A1 Dec. 26, 2002

Laid-Open Patent Publication No. 4-281461 discloses a using the photoreceptor, by which images having good method, in which a charge transport material is included in image qualities can be produced for a long period of time a protective layer together with a filler to prevent an increase without producing an abnormal image Such as image tailing of residual potential while maintaining good abrasion resis which is produced by a conventional high-abrasion-resis tance. Japanese Laid-Open Patent Publications Nos. tance photoreceptor. 53-133444 and 55-157748 disclose a method, in which an organic acid is included in a protective layer together with 0035 A further object of the present invention is to a filler, and Japanese Laid-Open Patent Publication No. provide a photoreceptor having a Surface layer which is 2-4275 discloses a method, in which an electron accepting abraded in a very Small amount to remove Surface-deterio material is included in a protective layer, to prevent an rating Substances adhered on the Surface layer, and to increase of residual potential. Japanese Laid-Open Patent provide an image forming apparatus and method including Publication No. 8-234455 discloses a method, in which the a cleaner cleaning the deteriorating Substances. It cannot be difference in refractive indeX between a filler in a charge Said that a photoreceptor having the highest possible abra transport layer and the charge transport layer is not less than Sion resistance is always good. It is, instead, preferable that 0.1, and the layer includes 1x10" to 2x10 pieces of filler the Surface of a photoreceptor is abraded in a very Small particles having a particle diameter of from 1 to 3 um per 1 amount by removing Surface-deteriorating Substances to mm°. keep the Surface of the photoreceptor clean. 0036 Briefly these objects and other objects of the 0.026 Further, Japanese Laid-Open Patent Publication present invention as hereinafter will become more readily No. 8-339092 discloses a method, in which a surface layer apparent can be attained by a photoreceptor including at of a photoreceptor includes inorganic particles having a least an electroconductive Substrate; and a photoSensitive Volume average particle diameter of from 1 um to 2 um and layer overlying the electroconductive Substrate and includ a ratio of the number average particle diameter to the weight ing at least a charge generation layer, a charge transport average particle diameter of from 1 to 2. layer; and a protective layer including a filler, wherein the 0027. However, although the photoreceptors produced by filler is dispersed in the protective layer So as to occupy an these methods have good abrasion resistance, these photo area of from 3 to 5% of a cross section of the protective receptors have the following drawbacks: layer; the filler has a particle diameter distribution having a peak at a diameter of from 0.2 to 0.3 um; and the particles 0028 (1) toner film tends to be formed thereon; of the filler having a particle diameter of not less than 0.3 um 0029 (2) the surface thereof is poorly cleaned because occupies an area of from 10 to 30% of the area of all the filler contact of a cleaning blade with the photoreceptors in the cross Section of the protective layer. deteriorates due to agglomeration of a filler in the 0037. In another aspect of the present invention, an image protective layer which is caused by poor dispersion of forming method using the photoreceptor is provided. the filler; and 0038. In yet another aspect of the present invention, an 0030 (3) the electrostatic stability and durability of a image forming apparatus using the photoreceptor is pro the photoreceptor deteriorate. vided. 0031. Therefore, the desired photoreceptor properties 0039. In a further aspect of the present invention, a have not been achieved yet. Particle conditions of inorganic process cartridge using the photoreceptor is provided. particles included in a protective layer have a big influence on the above-mentioned properties of the resultant photo 0040. These and other objects, features and advantages of receptor. This is partly disclosed in Japanese Laid-Open the present invention will become apparent upon consider Patent Publication No. 8-339092. However, the actual par ation of the following description of the preferred embodi ticle conditions of the inorganic particles in the protective ments of the present invention taken in conjunction with the layer are not described therein. Instead, it is only described accompanying drawings. that the particle diameter distribution in a dispersion liquid is Sharp and large particles are not included therein. There BRIEF DESCRIPTION OF THE DRAWINGS fore, a photoreceptor having good electrophotographic prop erties and good durability has not been developed yet. 0041 Various other objects, features and attendant advantages of the present invention will be more fully SUMMARY OF THE INVENTION appreciated as the same becomes better understood from the detailed description when considered in connection with the 0032. Accordingly, an object of the present invention is to accompanying drawings in which like reference characters provide an electrophotographic photoreceptor which can be designate like corresponding parts throughout and wherein: used for a high-durability and high-speed digital electropho tographic image forming apparatus using a laser as a Writing 0042 FIG. 1 is a schematic cross-sectional view of an light Source, and which can produce a high resolution image embodiment of the multilayer electrophotographic photore by the laser irradiation. ceptor of the present invention; 0033. Another object of the present invention is to pro 0043 FIG. 2 is a schematic cross-sectional view of vide a photoreceptor which has high mechanical durability another embodiment of the multilayer electrophotographic while having a thin layer to produce a high-resolution image. photoreceptor of the present invention; 0034). Yet another object of the present invention is to 0044 FIG. 3 is a schematic view illustrating an embodi provide an image forming method, an image forming appa ment of the image forming method and the image forming ratus and a process cartridge for an image forming apparatus apparatus of the present invention; and US 2002/0197549 A1 Dec. 26, 2002

004.5 FIG. 4 is a schematic view illustrating an embodi of the charge generation layer 3 is typically from 0.01 to 5 ment of the process cartridge for an image forming appara tim, and preferably from 0.1 to 2 um. tus of the present invention. 0057 The charge transport layer 4 can be formed by the DETAILED DESCRIPTION OF THE following method: INVENTION 0.058 (1) a charge transport material and a binder resin 0.046 Generally, the present invention provides an elec are dissolved or dispersed in a Suitable Solvent to trophotographic photoreceptor including a charge genera prepare a charge transport coating liquid; and tion layer 3 formed from a charge generation material, 0059 (2) the coating liquid is coated on the substrate charge transport layer 4 formed from a charge transport and dried to form a charge transport material. material and a protective layer 5. The protective layer 5 will be explained later. 0060 A , a leveling agent, etc, can be option ally added to the coating liquid. 0047. An electroconductive substrate 1 is provided as a film, a plastic cylinder or a paper coated with a 0061 Low molecular weight charge transport materials material having a volume resistance of not greater than 10" in the charge transport materials include an electron trans S2 cm, for example, metals. Such as aluminium, nickel, port material and a positive-hole transport material. Specific chromium, nichrome, copper, Silver, gold and platinum, and examples of the electron transport materials include elec metal oxides Such as tin oxides and indium oxides can be tron-accepting materials. Such as chloranil, bromanil, tetra coated by deposition or Sputtering. In addition, a plate of cyanoethylene, tetracyanoquinodimethane, 2,4,7-trinitro-9- metal Such as aluminium, aluminium alloys, nickel and fluorenon, 2,4,5,7-tetranitro-9-fluorenon, 2,4,5,7- Stainless Steel can be used. TubeS formed by tubing Such tetranitroXanthone, 24,8-trinitrothioxanthone, 2,68 metal plates also can be used, the Surface of which is treated trinitro-4H-indeno 1,2-b thiophene-4-one and 1,3,7- by cutting, Super finishing and polishing. trinitrodibenzothiophene-5,5-dioxides. 0.048. The charge generation layer 3 is formed from a 0062) These electron transport materials can be used charge generation material. alone or in combination. 0049 An inorganic or an organic material is used as a 0063 Specific examples of the positive-hole transport charge generation material. Specific examples of the charge materials include electron-releasing materials. Such as generation materials include mono azo pigments, disaZo Oxazole derivatives, oxadiazole derivatives, imidazole pigments, trisaZO pigments, perylene pigments, pery none derivatives, triphenylamine derivatives, 9-(p-diethylami pigments, quinacridone pigments, quinone type condensed nostyrylanthracene), 1,1-bis-(4-dibenzilaminophenyl)pro polycyclic compounds, Squaric acid type dyes, phthalocya pane, Styrylanthracene, Styrylpyrazoline, phenylhydrazone, nine type pigments, naphthalocyanine type pigments, aZu C-phenylstilbene derivatives, thiazole derivatives, triazole lenium Salt type dyes, Selenium, Selenium-tellurium alloys, derivatives, phenazine derivatives, acridine derivatives, ben Selenium-arsenic alloys, and amorphous-Silicon. These Zofuran derivatives, benzimidazole derivatives and charge generation materials can be used alone or in combi thiophene derivatives. nation. 0064. These positive-hole transport materials can be used 0050. The charge generation layer 3 can be formed by the alone or in combination. following method: 0065. When a high molecular weight charge transport 0051 (1) the charge generation material is mixed with material is used, a charge transport layer can be formed by a Solvent Such as tetrahydrofuran, cyclohexane, diox dissolving or dispersing the material in a Suitable Solvent to ane, 2-butanone and dichloroethane optionally together prepare a coating liquid, which is coated on the Substrate and with a binder resin; dried. The high molecular weight charge transport material may be the above-mentioned low molecular weight charge 0.052 (2) the mixture is dispersed with a ball mill, an transport material having a charge transport Substituent in attritor or a Sand mill to prepare a coating liquid; and the main chain or in the Side chain. 0053 (3) the coating liquid is coated on the electro 0066. In addition, a binder resin, a low molecular weight conductive Substrate to form a charge generation layer. charge transport material, a plasticizer, a lubricant and the 0.054 The coating liquid can be coated by a coating like can be added to the high molecular weight charge method Such as dip coating, Spray coating and bead coating. transport material. 0067 Specific examples of the binder resins for use in the 0.055 Specific examples of the binder resins optionally charge transport layer 4 together with the charge transport used include resins, resins, polyes material include or thermosetting resins Such ter resins, epoxy resins, polyketone resins, as resins, Styrene-acrylonitrile copolymers, Sty resins, Silicone resins, acryl resins, polyvinylbutyral resins, rene-butadiene copolymers, Styrene-maleic anhydride polyvinyl formal resins, polyvinyl ketone resins, polySty copolymers, resins, resins, rene resins, and polyacryl resins. The Suitable content of the -vinyl acetate copolymers, polyvinyl acetate binder resin is from 0 to 200 parts by weight per 100 parts resins, resins, polyarylate resins, by weight of the charge generation material. phenoxy resins, polycarbonate resins, cellulose acetate res 0056. The charge generation layer 3 can also be formed ins, ethyl cellulose resins, resins, polyvi by known vacuum thin film forming methods. The thickness nyl formal resins, polyvinyl toluene resins, acrylic resins, US 2002/0197549 A1 Dec. 26, 2002

Silicone resins, epoxy resins, melamine resins, urethane 0078. In addition, a layer of aluminium oxide formed by resins, phenol resins and alkyd resins. anodic oxidation, a layer of an organic compound Such as 0068 Specific examples of the solvents include tetrahy polyparaXylene (parylene) and an inorganic compound Such drofuran, dioxane, toluene, 2-butanone, monochloroben as SiO, SnO2, TiO2, ITO or CeO2 formed by a vacuum thin Zene, dichloroethane, methylene chloride, etc. film forming method can be also used as the undercoat layer. 0069. The thickness of the charge transport layer 4 can be 0079 The thickness of the undercoat layer is preferably Selected from a range of 5 to 30 um according to the required from 0 to 5 lum. properties of the photoreceptor. 0080 A protective layer 5 including a filler is formed on 0070 Specific examples of optionally added the multilayer electrophotographic photoreceptor of the to the charge transport layer include plasticizers for general present invention as a Surface layer to protect the photosen use for resins Such as dibutylphthalate and dioctylphthalate. Sitive layer and to improve durability. Suitable content of the plasticizer is from 0 to 30% by weight per 100% by weight of the binder resin. 0081 Specific examples of the materials for use in the protective layer 5 include resins such as ABS resins, ACS 0071 Specific examples of leveling agents optionally resins, olefin-vinyl monomer copolymers, chlorinated poly added to the charge transport layer 4 include Silicone oils ether resins, allyl resins, phenolic resins, polyacetal resins, Such as dimethyl Silicone oils and methyl phenyl Silicone polyamide resins, polyamideimide resins, polyacrylate res oils, and polymers or oligomers having a perfluoroalkyl ins, polyallylsulfone resins, resins, polybuty group in the Side chains. Suitable content of the leveling leneterephthalate resins, polycarbonate resins, polyetherSul agent is from 0 to 1% by weight per 100% by weight of the fone resins, resins, polyethyleneterephthalate binder resin. resins, resins, acrylic resins, 0.072 The content of the charge transport material resins, resins, polyphenyleneoxide resins, included in the photoSensitive layer of the present invention resins, AS resins, AB resins, BS resins, poly is preferably not less than 40% by weight per 100% by urethane resins, polyvinyl chloride resins, polyvinylidene weight of the charge transport layer. When the content is leSS chloride resins, and epoxy resins. than 40%, there is not enough damping time for the laser beam writing to the photoreceptor in a high-Speed electro 0082. A filler is added to the protective layer 5 to also photographic process. improve abrasion resistance. 0073. The transportability of the charge transport layer of 0083 Specific examples of Such fillers include fine pow the photoreceptor of the present invention is preferably not ders of fluorocarbon resins Such as ; less than 3x10 cm/V's, and more preferably not less than Silicone resins, or inorganic materials. Such as titanium 7x10 cm/V's under a condition of an electric filed oxide, Silica, alumina, Zirconium oxide, tin oxide and potas strength of the charge transport layer ranging from 2.5x10 sium titanate. to 5.5x10 V/cm. The composition of the charge transport layer can be adjusted Such that the transportability is within 0084. The content of the filler added to the protective the range. The transportability can be measured by the layer 5 is preferably from 10 to 40% by weight, and more known TOF method. preferably from 20 to 30% by weight. When the content of the filler is less than 10% by weight, abrasion resistance 0.074. In the multilayer electrophotographic photorecep deteriorates. When the content is greater than 40% by tor of the present invention, an undercoat layer can be weight, the potential of the lighted parts of the photoreceptor formed between the Substrate and the photosensitive layer. Significantly increases and Sensitivity deteriorates. 0075. The undercoat layer typically includes a resin as a main component. Considering that a photosensitive layer is 0085. In addition, an auxiliary agent to improve the coated on the undercoat layer with a Solvent, the resin dispersibility of the filler can be added to the protective layer preferably has good resistance against a general organic 5. Auxiliary agents used for paint, etc. can be used as the Solvent. Specific examples of Such resins include water auxiliary agent. The content of the auxiliary agent is pref Soluble resins Such as polyvinyl alcohol resins, casein and erably from 0.5 to 4% by weight, and more preferably from Sodium; alcohol-Soluble resins Such as 1 to 2% per 100% by weight of the filler. copolymers and methoxymethylated nylon; and ther 0086. In addition, the above-mentioned charge transport mosetting resins forming a three-dimensional network Such material can be added to the protective layer 5, and an as polyurethane resins, melamine resins, alkyd-melamine antioxidant can be optionally added to the protective layer 5. resins and epoxy resins. The antioxidant will be explained later. 0.076 The undercoat layer may include a fine powder of metal oxides Such as titanium oxides, Silica, alumina, Zir 0087 Known methods such as a spray coating method conium oxides, tin oxides and indium oxides to prevent can be used to form the protection layer 5. The thickness of occurrence of moiré in the resultant images and to decrease the protection layer is preferably from 0.5 to 10 um, and the residual potential of the resultant photoreceptor. The more preferably from 4 to 6 um. undercoat layer can be formed using a Suitable Solvent and 0088. In the present invention, it is important to uni a Suitable coating method just as the above-mentioned formly disperse a filler in the protective layer such that the photoSensitive layer can. dispersed filler has the Specific properties mentioned above 0077. The undercoat layer may include a metal oxide to prepare a photoreceptor having good abrasion resistance formed by, for example, a Sol-gel proceSS and the like, using and capable of producing images having good image prop a silane coupling agent, a titanium coupling agent, a chro erties. That is, the protective layer of the present invention mium coupling agent, etc. does not deteriorate the Sensitivity and the electroStatic US 2002/0197549 A1 Dec. 26, 2002

Stability of the photoSensitive layer and it has high resolution 0098. Using a dispersant in the coating liquid is particu properties relative to the imaging light. In addition, Since the larly effective because the dispersion of the filler in the photoreceptor of the present invention has a thin protective protective layer is improved by adding the dispersant. Since layer having good abrasion resistance, high-resolution adding too much dispersant causes an abnormal image, the images can be produced at a high Speed. amount added should be adjusted such that the above 0089 Forming a protective layer including inorganic fine mentioned desired dispersion conditions of the filler can be particles on a photoreceptor considerably improves the obtained. abrasion resistance of the photoreceptor compared with an 0099. In the present invention, the dispersion conditions organic photoreceptor which does not have a protective of a filler are determined as follows: layer. However, a photoreceptor having as high as possible abrasion-resistance is not always good in electrophoto 0100 (1) a part of the protective layer randomly graphic Systems, and it is preferable to control the Surface of Selected is cut off; a photoreceptor So as to be abraded very slightly to maintain 0101 (2) the cross section is treated so as to be good image properties. electroconductive; 0090. It has been determined by the present inventors that 0102 (3) the cross section is photographed using a the abrasion-resistance of the protective layer depends on field emission type Scanning electron microScope; the quantity of inorganic fine particles, i.e., the occupation ratio of the particles, and the particle diameter distribution 0103 (4) the cross section is scanned by an image thereof in any croSS Section of the protective layer. The Scanner to be read by a personal computer; occupation ratio is preferably from 3 to 5%, and the particle 0104 (5) the particle diameter and the area of each diameter distribution preferably has a peak at a diameter of filler in the croSS Section are determined using the from 0.2 to 0.3 um. Image Pro Plus image processing Software manufac 0.091 As a result of the present inventors investigations, tured by Media Cybernetics, L.P., and it has also been found that when the quantity of the filler 0105 (6) the dispersion conditions of the filler are (i.e., the inorganic fine particles) is Small, the abrasion determined from the distribution status of the filler in resistance is not good enough. In contrast, when the quantity the croSS Section. is large, the residual potential increases, and the Sensitivity of the resultant photoreceptor and the resolution of the 0106 An intermediate layer can be formed between the resultant images deteriorate. The particle diameter distribu photosensitive layer and the protective layer in the photo tion also influences the residual potential, and the Sensitivity receptor of the present invention. of the resultant photoreceptor and the resolution of the 0107 A binder resin is typically used as a main compo resultant images. nent in the intermediate layer. Specific examples of binder 0092. In addition, another important thing discussed by resins include polyamide resins, alcohol-Soluble nylon, the inventorS is that the occupation ratio of the particles of water-soluble polyvinylbutyral resins, polyvinylbutyral res the filler having a particle diameter of not less than 0.3 um ins, polyvinylalcohol resins, and the like. The above-men in a cross section of the protective layer is from 10 to 30% tioned conventional coating method can be used as a method of the total filler occupation area therein to prevent abnormal for forming the intermediate layer. The thickness of the imageS Such as image tailing. In addition, the Surface of a intermediate layer is preferably from 0.05 to 2 um. photoreceptor can be abraded very slightly when the quan 0108. In the present invention, for an improvement of tity of the filler having a particle diameter of not less than 0.3 ambience, and above all, for the purpose of preventing the tum is within the range mentioned above. deterioration of the Sensitivity and the increase of the 0093. In this case, the particle diameter of a filler means residual potential of the photoreceptor, the following mate the particle diameter of the primary particles and any rials can be added to each layer of the photoreceptor: Secondary particles of the filler which are formed as an agglomeration of the primary particles. With a filler having 0109 (a) an antioxidant; a relatively large primary particle diameter, the filler is 0110 (b) a plasticizer; preferably dispersed So as to be almost all primary particles. However, agglomeration of the primary particles (i.e., the 0111 (c) an ultraviolet absorbent; Secondary particles) may be present in the protective layer. 0112 (d) a low molecular weight charge transport The particle diameter of the filler is determined including material; and that of the Secondary particles. The primary particles and the Secondary particles can be present together in the protective 0113 (e) a leveling agent. layer. 0114) Specific examples of the antioxidants (a) include phenolic compounds Such as 2,6-di-t-butyl-p-creSol, buty 0094. The above mentioned preferable dispersion condi lated hydroxyanisole, 2,6-di-t-butyl-4-ethylphenol, n-octa tions of the filler in the protective layer can be controlled by decyl-3-3-(4-hydroxy-3,5-di-t-butylphenol), 2.2-methylene controlling the following factors: bis-(4-methyl-6-t-butylphenol), 2.2-methylene-bis-(4-ethyl 0.095 (1) particle diameter and the distribution of a 6-t-butylphenol), 4,4-thiobis-(3-methyl-6-t-butylphenol), material for use as the filler; 4,4-butylidenebis-(3-methyl-6-t-butylphenol), 1,1,3-tris-(2- methyl-4-hydroxy-5-t-butylphenyl)butane, 1,3,5-trimethyl 0096 (2) formulation of a suitable coating liquid; and 2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzil)benzene, tetrakis 0097 (3) coating apparatus and coating conditions. methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate US 2002/0197549 A1 Dec. 26, 2002 methane, bis 3,3-bis(4-hydroxy-3-t-butylphenyl)butyric 0116 Specific examples of the ultraviolet absorbents (c) acid glycol ester and tocopherol; paraphenylenediamine include benzophenone ultraViolet absorbents Such as 2-hy Such as N-phenyl-N-isopropyl-p-phenylenediamine, N,N- droxybenzophenone, 2,4-dihydroxybenzophenone, 2,2,4- di-Sex-butyl-p-phenylenediamine, N-phenyl-N-Sec-butyl-p- trihydroxybenzophenone, 2,2,4,4-tetrahydroxybenzophe phenylenediamine, N,N-di-isopropyl-p-phenylenediamine, none and 2,2-dihydroxy4-methoxybenzophenone; Salicylate N,N-dimethyl-N,N-di-t-butyl-p-phenylenediamine; hydro ultraViolet absorbents Such as phenyl Salicylate and, 2,4-di quinone Such as 2,5-di-t-octylhydroquinone, 2,6-didodecyl t-butylphenyl3,5-di-t-butyl4-hydroxybenzoate; benzotriazole hydroquinone, 2-dodecylhydroquinone, 2-dodecyl-5-chlo ultraviolet absorbents such as (2-hydroxyphenyl)benzotria zole, (2-hydroxy5-methylphenyl)benzotriazole, (2-hy rohydroquinone, 2-t-octyl-5-methylhydroquinone, 2-(2- droxy5-methylphenyl.9benzotriazole and (2-hydroxy3-t-bu octadecenyl)-5-methylhydroquinone; organic Sulfuric tyl5-methlphenyl)5-chlorobenzotriazole; cyanoacrylate compounds Such as dilauryl-3,3-thiopropionate, distearyl-3, ultraViolet absorbents Such as ethyl-2-cyano-3,3-dipheny 3-thiodipropionate and ditetradecyl-3,3-thiopropionate, and lacrylate and methyl 2 organic phosphoric compounds Such as triphenylphosphine, carbomethoxy3(paramethoxy)acrylate; quencher (metal tri(nonylphenyl)phosphine, tri(dinonylphenyl)phosphine, complex) ultraviolet absorbents Such as nickel(2,2thiobis(4- tricreSylphosphine and tri(2,4-dibutylphenoxy)phosphine. t-octyl)phenolate)-n-butylamine, nickeldibutyldithiocar 0115 Specific examples of the plasticizers (b) include bamate and cobaltdicyclohexyldithiophosphate; and HALS (hindered amine) ultraViolet absorbents such as bis(2,2,6,6- phosphoric acid ester plasticizerS Such as triphenyl phoS tetramethyl-4-piperidyl)sebacate, bis(1,2,2,6,6-pentam phate, tricresyl phosphate, trioctyl phosphate, octyldiphenyl ethyl-4-piperidyl)sebacate, 1-2-3-(3,5-di-t-butyl-4-hy phosphate, trichloroethyl phosphate, creSyldiphenyl phoS droxyphenyl)propionyloxyethyl-4-3-(3,5-di-t-nutyl-4- phate, tributyl phosphate, tri-2-ethylhexyl phosphate and hydroxyphenyl)propionyloxy-2,2,6,6-tetramethylpyridine, triphenyl phosphate, phthalic acid ester plasticizerS Such as dimethyl , diethyl phthalate, diisobutyl phthalate, 8-benzyl-7,7,9.9-tetramethyl-3-octyl-1,3,8-triazaspiro 4.5 , diheptyl phthalate, di-2-ethylhexyl phtha undecane-2,4-di-One and 4-benzoyloxy-2,2,6,6-tetrameth late, disooctyl phthalate, di-n-octyl phthalate, dinonyl ylpiperidine. phthalate, , , diun 0117 The present invention provides an electrophoto decyl phthalate, ditridecyl phthalate, dicyclohexyl phthalate, graphic photoreceptor, in which (1) a photosensitive layer butylbenzyl phthalate, butyllauryl phthalate, methyloleyl and a protective layer are overlaid on an electroconductive phthalate, octyldecyl phthalate, dibutyl fumarate and dioctyl Substrate; (2) an undercoat layer and an intermediate layer fumarate; aromatic carboxylic acid ester plasticizerS Such as are optionally formed between the Substrate and the photo trioctyl trimellitate, tri-n-octyl trimellitate and octyl oxyben Sensitive layer, and between the photosensitive layer and the Zoate, dibasic fatty acid ester plasticizerS Such as dibutyl protection layer, respectively; and (3) the protective layer , di-n-hexyl adipate, di-2-ethylhexyl adipate, di-n- includes a filler to improve the abrasion resistance and the octyl adipate, n-octyl-n-decyl adipate, diisodecyl adipate, durability of the photoreceptor. The photoreceptor of the dicapryl adipate, di-2-etylhexyl azelate, dimethyl Sebacate, present invention has good durability, Stability and abrasion diethyl Sebacate, dibutyl Sebacate, di-n-octyl Sebacate, di-2- resistance even when used in a high-Speed electrophoto ethylhexyl Sebacate, di-2-ethoxyethyl Sebacate, dioctyl Suc graphic apparatus Since the filler in the protective layer is cinate, diisodecyl Succinate, dioctyl tetrahydrophthalate and dispersed as mentioned above. In addition, by applying a di-n-octyl tetrahydrophthalate; fatty acid ester derivative lubricant to the Surface of the protective layer, toner filming plasticizerS Such as butyl oleate, glycerin monooleate esters, can be prevented while keeping the good abrasion resistance methyl acetylricinolate, pentaerythritol esters, triacetin and of the photoreceptor. In addition, it is preferable in the image tributyrin, oxyacid ester plasticizerS Such as methyl acetyl forming apparatus of the present invention that repetition of ricinolate, butyl acetylricinolate, butylphthalylbutyl glyco an operation of toner adhesion to the photoreceptor and a late and tributyl acetylcitrate, epoxy plasticizerS Such as collection operation of the toner at the cleaning portion epoxydized Soybean oil, epoxydized linseed oil, butyl when the toner image is not formed is effective to prevent an epoxy Stearate, decyl epoxyStearate, octyl epoxy Stearate, image tailing problem while hardly abrading the Surface of benzyl epoxy Stearate, dioctyl epoxyhexahydrophthalate and the photoreceptor. didecyl epoxyhexahydrophthalate, dihydric alcohol ester 0118. The toner of the present invention may include a plasticizerS Such as diethylene glycol dibenzoate and trieth lubricant. In addition, both a toner including a lubricant and ylene glycol di-2-ethylbutyrate, chlorine-containing plasti a toner not including a lubricant may be used, and the toner cizerS Such as chlorinated paraffin, chlorinated diphenyl, including a lubricant has an effect on keeping the Surface of methyl esters of chlorinated fatty acids and methyl esters of the photoreceptor properly clean when the cleaning opera methoxychlorinated fatty acids, polyester plasticizerS Such tion is performed. as polypropylene adipate, polypropylene Sebacate, polyes ters and acetylated , Sulfonic acid derivative plas 0119) Specific examples of the lubricants for use in the ticizerS Such as p-toluene Sulfonamide, o-toluene Sulfona protective layer include fatty acid metal Soap Such as Zinc mide, p-toluene Sulfoneethylamide, o-toluene Stearate, Zinc laurate, Zinc myristate, calcium Stearate and sulfoneethylamide, toluene sulfone-N-ethylamide and aluminium Stearate; fine powders of fluorocarbon resins p-toluene Sulfone-N-cyclohexylamide, citric acid derivative Such as polytetrafluoroethylene, polyvinylidene fluoride and plasticizerS Such as triethyl citrate, triethyl acetylcitrate, PFA; and fine powders of ethylene resins such as polyeth tributyl citrate, tributyl acetylcitrate, tri-2-ethylhexyl acetyl ylene and polypropylene. Zinc Stearate and calcium Stearate citrate and n-octyldecyl acetylcitrate; and other compounds are preferably used. Such as terphenyl, partially hydrated terphenyl, camphor, 0120 When the quantity of the lubricant applied to the 2-nitro diphenyl, dinonyl naphthalene and methyl abietate. photoreceptor is too much, the quantity thereof on the US 2002/0197549 A1 Dec. 26, 2002 transfer image also becomes too much, resulting in poor 0.130. It is found that a photoreceptor having good dura fixation of the transfer image. When the coefficient of bility, Stability and abrasion resistance is provided even friction of the photoreceptor falls to about 0.1 due to too when used in a high-speed electrophotographic process by much lubricant, the resultant image density deteriorates. For forming a protective layer including a filler as a Surface layer example, when a toner including Zinc Stearate is Supplied to of the photoreceptor and by dispersing the filler in the the Surface of the photoreceptor, the content of the Zinc protective layer as mentioned above. Stearate in the toner is preferably from 0.1 to 0.2% by 0131 Next, the image forming method and the image weight. forming apparatus will be explained using the drawings. 0121. In the image forming apparatus of the present invention, the toner adhesion to the photoreceptor and the 0132 FIG. 3 is a schematic view illustrating an embodi toner collection at the cleaning portion when not producing ment of the image forming method and the image forming an image prevent toner filming while maintaining abrasion apparatus of the present invention. resistance. In addition, adhesion and accumulation of a 0133) A photoreceptor 6 includes a photosensitive layer product on the photoreceptor caused by the charge thereon on an electroconductive Substrate. The photoreceptor 6 is are prevented, because various materials adhered to the shown shaped like a drum, however, it can be shaped like a photoreceptor are cleaned together with the toner. sheet or an endless belt. 0122) The toner adhesion and collection effectively oper 0134) A pre-transfer charger 7, a transfer charger, a ates when the adhered amount of the toner is Suitable for a Separation charger and a pre-cleaning charger 8 are option halftone image and the operating time is about 30 Seconds, using a photoreceptor having a diameter of 30 mm and a ally arranged. Known chargerS Such as corotrons, linear Velocity of 125 mm/sec. Using more toner and a Scorotrons, Solid State chargers and charging rollers are used longer operating time are not preferable because the clean therefor. ing portion is overloaded and the consumption of toner 0.135 A charger 9 may contact the photoreceptor, how increases. ever, it is preferable to arrange the charger 9 closely spaced relative to the photoreceptor Such that a gap of from about 0123. When the diameter and the linear velocity of the 10 to 200 um is formed therebetween to prevent the abrasion photoreceptor are different, the amount of the toner can be of both the photoreceptor and the charger as well as the toner adjusted So as to be Suitable for producing a halftone image. filming problem. Particularly, by forming a gap of about 50 0.124. As mentioned above, the thickness of the layers of tim between the charger and the photoreceptor, good prop the photoreceptor can be made thinner because of the erties for the photoreceptor can be maintained. The reason is improvement of the abrasion resistance thereof, which is that the influence of the charging member on the Surface of preferable for producing an image having high resolution the protective layer can be minimized. and is advantageous for an image forming apparatus. 0.136 The voltage applied to the charger 9 is preferably 0.125. In addition, the present invention provides an a DC voltage overlapped with an AC voltage to stably image forming method including at least a charging process, perform charging in a manner to prevent uneven charging. an image irradiation process, a developing process, a trans However, even though the charge Stability is good in this fer process, a fixing process and a cleaning process, wherein case, the Surface layer of a Standard photoreceptor tends to the above-mentioned multilayer photoreceptor of the present wear excessively as compared with the case in which only invention is used. direct current is applied. The photoreceptor of the present 0.126 Further, the present invention provides an image invention can keep its good properties due to its high forming apparatus including at least a charger, an image abrasion resistance even when a DC voltage overlapped with irradiator, an image developer, a transferer, a fixer and a an AC voltage is applied to the charger. cleaner, wherein the above-mentioned multilayer photore 0.137 As a transfer means, the above-mentioned chargers ceptor of the present invention is used. can be typically used, however, a transfer belt as shown in 0127. When the photosensitive layer is abraded, the elec FIG. 3 is preferably used. tric properties of the photoreceptor Such as chargeability and the capability of fading light change. Therefore, it becomes 0.138. As a light source for an image irradiator 11, a difficult to maintain the quality of the resultant image when discharging lamp 12 and the like, any known illuminators predetermined processes are performed. Such as fluorescent lamps, tungsten lamps, halogen lamps, mercury lamps, Sodium lamps, light emitting diodes (LEDs), 0128. The photosensitive layer is abraded at all portions laser diodes (LDS) and electroluminescense (EL) lamps can where the photoreceptor contacts other image forming units be used. in an electrophotographic process. The unit causing the most abrasion is a cleaning unit Such as a cleaning blade or a 0.139. In order to irradiate with only light having a desired cleaning brush. The abrasion by the other units does not wavelength, various filterS Such as Sharp cut filters, band substantially affect the life of the photoreceptor. pass filters, near infrared cutting filters, dichroic filters, interference filters and color temperature conversion filters 0129. The abrasion caused by the cleaning unit is typi can also be used. cally Separated into two patterns. One is the abrasion caused by the shearing force generated between the photoreceptor 0140. Such light sources can also be used for a transfer and the blade (or the brush), and the other is the abrasion process including light irradiation, a discharging process, a caused by the toner which is sandwiched by the photore cleaning proceSS or a pre-exposure process and the like ceptor and the blade (or brush), and which performs like a process besides the processes shown in FIG. 3, to irradiate grind Stone. the photoreceptor 6. US 2002/0197549 A1 Dec. 26, 2002

0141 Atoner image developed on the photoreceptor 6 by a developing unit 13 is transferred to a transfer sheet 14. However, not all the toner is transferred and the residual toner on the photoreceptor 6 is removed by a fur blush 15 Undercoat layer coating liquid and a cleaning blade 16. The cleaning may be made by only Powder of titanium dioxide 400 the cleaning blush Such as the fur blush and a mag-fur blush. Melamine resin 65 When the photoreceptor 6 that is charged positively (or Alkyd resin 12O negatively) is exposed to imagewise light, an electrostatic 2-butanone 400 latent image having a positive (or negative) charge is formed Charge generation layer coating liquid on the photoreceptor 6. When the latent image is developed Titanyl phthalocyanine 7 with a toner having a negative (or positive) charge, a positive Polyvinyl butyral 5 image can be obtained. In contrast, when the latent image is 2-butanone 400 developed with a toner having a positive (negative) charge, Charge transport coating liquid a negative image can be obtained. Any known developing Polycarbonate 1O methods can be used. In addition, any known discharging Charge transport material 8 methods can also be used. Numeral 17 denotes a registration having the following formula (1) roller, and numeral 19 denotes a separation pick. (1) 0142. The present invention provides an image forming CH method and an image forming apparatus using the electro photographic photoreceptor of the present invention as an image bearing means. The image formation unit as shown in FIG. 3 can be fixedly built in a copier, a facsimile and a printer. In addition, the image formation unit may be built in OCFCH each apparatus in the form of a detachable proceSS cartridge. 0143 FIG. 4 is a schematic view illustrating an embodi ment of the process cartridge of the present invention for an image forming apparatus. C. 0144) Numeral 101 denotes a photoreceptor drum rotat CH ing in a direction indicated by an arrow. Around the photo Tetrahydrofuran 2OO receptor 101, a contact charger 102, an imagewise light Protective layer coating liquid irradiator 103, an image developer 104, a contact transfer device 106, a cleaning unit 107, a discharging lamp 108 and Polycarbonate 1O a fixer 109 are arranged, and a transfer sheet 105 is supplied Charge transport material 7 thereto. having the following formula (2) (2) 0145 The process cartridge of the present invention CH includes at least a charge means, an irradiation means, a developing means, a transfer means, a cleaning means and a discharging means besides a photoreceptor. The photore ceptor 101 is the above-mentioned multilayer photoreceptor of the present invention. OCECH 0146 Having generally described this invention, further understanding can be obtained by reference to certain spe cific examples which are provided herein for the purpose of illustration only and are not intended to be limiting. In the C. descriptions in the following examples, the numbers repre Sent weight ratioS in parts, unless otherwise Specified. CH Fine particles of alumina 6 EXAMPLES (AA-03 from Sumitomo Chemical Co., Ltd. having a particle diameter of 0.3 um) Example 1 Dispersant O.08 (BYK-P104 from BYK Chemie Japan) 0147 An undercoat layer coating liquid, a charge gen Tetrahydrofuran 700 eration layer coating liquid, a charge transport layer coating Cyclohexanone 2OO liquid and a protective layer coating liquid having the following components were coated and dried on an alu minium Substrate in the order mentioned to prepare an 014.9 The dispersant was added at the beginning of the electrophotographic photoreceptor having an under coat mixing. layer 3.5um thick, a charge generation layer 0.15 um thick, a charge transport layer 20 um thick and a protective layer 0150. A random cross section of the protective layer of 5 um thick. the thus prepared photoreceptor was observed by a Scanning 0.148. A spray coating method was used for coating the electron microscope (SEM) to investigate the dispersion protective layer, and a dip coating method was used for conditions of the filler in the protective layer. The occupa coating the other layers. tion ratio of the filler in the area was 3.3%. US 2002/0197549 A1 Dec. 26, 2002

0151. The peak of the particle diameter distribution was 0156 The peak of the particle diameter distribution was 0.2 um, and the occupation ratio of the filler having a particle 0.2 um, and the occupation ratio of the filler having a particle diameter of not less than 0.3 um was 16% of the total area diameter of not less than 0.3 um was 12% of the total area of all the fillers. of all the fillers. 0152. In addition, an equivalent photoreceptor having a diameter of 30 mm was prepared to Set in the electropho O157 The quality of the produced image was good at the tographic process shown in FIG. 3, and its durability was beginning, and also good after 50,000 copies were continu evaluated. The imagewise light was that of a laser beam ously produced though a slight halftone image irregularity having a wavelength of 780 nm, and AC (2 kHz, 1.8 kVpp) was observed. The abrasion loss of the photoreceptor after and DC (-751V) were applied to the charging roller. The 50,000 copies were continuously produced was 2.2 lum. proceSS Speed was 125 mm/sec. 0153. The quality of the produced image was good at the Example 3 beginning, and also good after 50,000 copies were continu 0158. The procedure for preparation and evaluation of the ously produced though a slight halftone image irregularity photoreceptor of Example 1 were repeated except that the was observed. The abrasion loss of the photoreceptor after charge generation coating liquid was changed to the follow 50,000 copies were continuously produced was 1.9 um. ing coating liquid and the parts by weight of the dispersant Example 2 was changed to 0.07, and the laser beam was changed to a laser beam having a wavelength of 655 nm. 0154) The procedure for preparation and evaluation of the photoreceptor of Example 1 were repeated except that the 0159 Charge Generation Coating Liquid

Charge generation coating liquid Bisazo pigment having 12 the following formula (4) (4)

HNOC OH a (O) NEN NEN (O) HC (O) Polyvinylbutyral 2-butanone 2OO Cyclohexanone 400 charge transport material used for coating the charge trans 0160 A random cross section of the protective layer of port layer and the protective layer was changed to a material the thus prepared photoreceptor was observed by a SEM to having the following formula (3). investigate the dispersion conditions of the filler in the protective layer. The occupation ratio of the filler in the area was 3.5%. (3) 0.161 The peak of the particle diameter distribution was 0.3 um, and the occupation ratio of the filler having a particle diameter of not less than 0.3 um was 26% of the total area of all the fillers. O 0162 The quality of the produced image was good at the beginning, and also good after 50,000 copies were continu ously produced though a slight halftone image irregularity was observed. The abrasion loss of the photoreceptor after o 50,000 copies were continuously produced was 2.4 um. Comparative Example 1 0.155) A random cross section of the protective layer of 0163 The procedure for preparation and evaluation of the the thus prepared photoreceptor was observed by a SEM to photoreceptor of Example 1 were repeated except that the investigate the dispersion conditions of the filler in the dispersant was not used. protective layer. The occupation ratio of the filler in the area 0164. A random cross section of the protective layer of was 4.6%. the thus prepared photoreceptor was observed by a SEM to US 2002/0197549 A1 Dec. 26, 2002 investigate the dispersion conditions of the filler in the protective layer. The occupation ratio of the filler in the area was 3.7%. Temperature: 30° C. 0.165. The peak of the particle diameter distribution was Humidity: 90% RH 0.3 um, and the occupation ratio of the filler having a particle diameter of not less than 0.3 um was 43% of the total area of all the fillers. 0.178 Deterioration of the image resolution due to image 0166 The produced image gradually had black stripes tailing was not observed. due to a failure of cleaning after 50,000 copies were con tinuously produced. The abrasion loSS of the photoreceptor Example 6 after 50,000 copies were continuously produced was 2.5 lum. 0179 The procedure for preparation and evaluation of the Comparative Example 2 electrophotographic process of Example 4 were repeated except that a pair of gap members made of a PET film of 50 0167 The procedure for preparation and evaluation of the lum thick having a width of 10 mm were formed on both photoreceptor of Example 2 were repeated except that the Sides of the charging roller in the non-image forming area fine particles of alumina was changed to AA-07 from Such that the charging roller was arranged closely to the Sumitomo Chemical Co., Ltd. having a particle diameter of photoreceptor. 0.7 um. 0168 A random cross section of the protective layer of 0180. The produced image was very good and no half the thus prepared photoreceptor was observed by a SEM to tone image irregularity was observed even after 50,000 investigate the dispersion conditions of the filler in the copies were continuously produced. The abrasion loSS of the protective layer. The occupation ratio of the filler in the area photoreceptor after 50,000 copies were continuously pro was 5.4%, and the peak of the particle diameter distribution duced was 1.3 lim. was 0.6 lim. 0181 At that time, residues such as toner components on 0169. The produced image gradually had black stripes the Surface of the charging roller were hardly observed, and due to a failure of cleaning after 50,000 copies were con the initial condition of the roller was maintained. Therefore, tinuously produced. The abrasion loSS of the photoreceptor the durability of the charging roller is effectively improved after 50,000 copies were continuously produced was 1.8 um. in the electrophotographic process of Example 6. Example 4 Example 7 0170 The procedure for preparation and evaluation of the 0182. The procedure for preparation and evaluation of the electrophotographic process of Example 1 were repeated photoreceptor of Example 1 were repeated except that the except that 0.15% by weight of a zinc stearate powder was fine particles of the alumina were changed to AA-04 from added into the toner Supplied to the developing part. Sumitomo Chemical Co., Ltd. having a particle diameter of 0171 The produced image was very good and no half 0.4 um. tone image irregularity was observed even after 50,000 0183) A random cross section of the protective layer of copies were continuously produced. The abrasion loSS of the the thus prepared photoreceptor was observed by a SEM to photoreceptor after 50,000 copies were continuously pro investigate the dispersion conditions of the filler in the duced was 1.4 lim. protective layer. The occupation ratio of the filler in the area Example 5 was 4.9%. 0172 The procedure for preparation and evaluation of the 0.184 The peak of the particle diameter distribution was electrophotographic process of Example 4 were repeated 0.3 um, and the occupation ratio of the filler having a particle except that the following non-image forming performances diameter of not less than 0.3 um was 28% of the total area were repeated for 20 sec. every time when 1,000 copies were of all the fillers. produced through continuous production of 50,000 copies: 0185. The quality of the produced image was good at the 0173 (1) light irradiation up to the lighted area poten beginning, and also good after 50,000 copies were continu tial; ously produced though a slight halftone image irregularity 0174 (2) the toner image development; and was observed. The abrasion loss of the photoreceptor after 0175 (3) collection of the toner remaining on the 50,000 copies were continuously produced was 2.4 lum. photoreceptor by the cleaner. Further, when images were produced under the environmen 0176) The produced image was very good and no half tal condition of 30° C. 90% RH after 50,000 copies were tone image irregularity was observed even after 50,000 continuously produced, no image tailing was observed and copies were continuously produced. The abrasion loSS of the the Surface of the photoreceptor was kept clean. photoreceptor after 50,000 copies were continuously pro duced was 2.1 lim. Example 8 0177. In addition, images were produced under the fol 0186 The procedure for preparation and evaluation of the lowing environmental conditions of high temperature and photoreceptor of Example 1 were repeated except that the high humidity after 50,000 copies were continuously pro parts by weight of the adding Volume of the dispersant was duced. changed to 0.1. US 2002/0197549 A1 Dec. 26, 2002

0187. A random cross section of the protective layer of Comparative Example 4 the thus prepared photoreceptor was observed by a SEM to investigate the dispersion conditions of the filler in the 0196. The procedure for preparation and evaluation of the protective layer. The occupation ratio of the filler in the area photoreceptor of Example 9 were repeated except that the was 3.2%. fine particles of the alumina were changed to Silica fine particles from Shinetsu Chemical Co., Ltd. having a particle 0188 The peak of the particle diameter distribution was diameter of 0.1 um. 0.2 um, and the occupation ratio of the filler having a particle diameter of not less than 0.3 um was 11% of the total area 0.197 A random cross section of the protective layer of of all the fillers. the thus prepared photoreceptor was observed by a SEM to investigate the dispersion conditions of the filler in the 0189 The quality of the produced image was good at the protective layer. The occupation ratio of the filler in the area beginning, and also good after 50,000 copies were continu was 3.8%. ously produced though a slight halftone image irregularity was observed. The abrasion loss of the photoreceptor after 0198 The peak of the particle diameter distribution was 50,000 copies were continuously produced was 1.8 um. 0.1 um, and the occupation ratio of the filler having a particle Further, when images were produced under the environmen diameter of not less than 0.3 um was 7% of the total area of tal condition of 30° C. 90% RH after 50,000 copies were all the fillers. continuously produced, no image tailing was observed and 0199 The quality of the produced image was good at the the Surface of the photoreceptor was kept clean. beginning, but after 50,000 copies were continuously pro Example 9 duced, a halftone image irregularity was observed, which was believed to be caused by a residue on the surface of the 0190. The procedure for preparation and evaluation of the photoreceptor. The abrasion loSS of the photoreceptor after photoreceptor of Example 3 were repeated except that the 50,000 copies were continuously produced was 2.1 um. fine particles of the alumina were changed to AA-04 from Further, when images were produced under the environmen Sumitomo Chemical Co., Ltd. having a particle diameter of tal condition of 30° C. 90% RH after 50,000 copies were 0.4 um, and that the parts by weight of the adding Volume continuously produced, deterioration of the image resolution of the dispersant was changed to 0.1. due to image tailing was observed. 0191) A random cross section of the protective layer of the thus prepared photoreceptor was observed by a SEM to Example 10 investigate the dispersion conditions of the filler in the 0200. The procedure for preparation and evaluation of the protective layer. The occupation ratio of the filler in the area photoreceptor of Example 9 were repeated except that the was 4.7%. parts by weight of the fine particles of the alumina for the 0.192 The peak of the particle diameter distribution was protective layer coating liquid was changed to 5, and that the 0.3 um, and the occupation ratio of the filler having a particle parts by weight of the adding Volume of the dispersant was diameter of not less than 0.3 um was 21% of the total area changed to 0.08. of all the fillers. 0201 Arandom cross section of the protective layer of 0193 The quality of the produced image was good at the the thus prepared photoreceptor was observed by a SEM to beginning, and also good after 50,000 copies were continu investigate the dispersion conditions of the filler in the ously produced though a slight halftone image irregularity protective layer. The occupation ratio of the filler in the area was observed. The abrasion loss of the photoreceptor after was 3.6%. 50,000 copies were continuously produced was 2.2 lum. 0202) The peak of the particle diameter distribution was Further, when images were produced under the environmen 0.3 um, and the occupation ratio of the filler having a particle tal condition of 30° C. 90% RH after 50,000 copies were continuously produced, no image tailing was observed and diameter of not less than 0.3 um was 15% of the total area the Surface of the photoreceptor was kept clean. of all the fillers. 0203 The quality of the produced image was good at the Comparative Example 3 beginning, and also good after 50,000 copies were continu 0194 The procedure for preparation and evaluation of the ously produced though a slight halftone image irregularity photoreceptor of Example 4 were repeated except that the was observed. The abrasion loss of the photoreceptor after filler and the dispersant were not added to the protective 50,000 copies were continuously produced was 2.6 um. layer of the photoreceptor. Further, when images were produced under the environmen tal condition of 30° C. 90% RH after 50,000 copies were 0.195 The quality of the produced image was good at the continuously produced, no image tailing was observed and beginning, but after 50,000 copies were continuously pro the Surface of the photoreceptor was kept clean. duced, a toner filming occurred on the whole Surface of the photoreceptor. Black Stripes on the produced image and a Comparative Example 5 big halftone image irregularity due to a failure of cleaning were observed. The abrasion loss of the photoreceptor after 0204. The procedure for preparation and evaluation of the 50,000 copies were continuously produced was 4.6 um. photoreceptor of Example 9 were repeated except that the Further, when images were produced under the environmen parts by weight of the fine particles of the alumina for the tal condition of 30° C. 90% RH after 50,000 copies were protective layer coating liquid was changed to 7.5 and that continuously produced, image tailing was observed in every the parts by weight of the adding Volume of the dispersant produced image. was changed to 0.12. US 2002/0197549 A1 Dec. 26, 2002

0205 A random cross section of the protective layer of produced, image tailing was observed. The abrasion loSS of the thus prepared photoreceptor was observed by a SEM to the photoreceptor after 50,000 copies were continuously investigate the dispersion conditions of the filler in the produced was 1.7 um. protective layer. The occupation ratio of the filler in the area 0216) This document claims priority and contains subject was 6.0%. matter related to Japanese Patent Applications Nos. 2000 0206. The peak of the particle diameter distribution was 342.999, 2001-105675 and 2001-308556, filed on Nov. 10, 0.3 um, and the occupation ratio of the filler having a particle 2000, Apr. 4, 2001 and Oct. 4, 2001 respectively, incorpo diameter of not less than 0.3 um was 19% of the total area rated herein by reference. of all the fillers. 0217. Having now fully described the invention, it will be 0207. The quality of the produced image was good at the apparent to one of ordinary skill in the art that many changes beginning, and also good after 50,000 copies were continu and modifications can be made thereto without departing ously produced. However, when images were produced from the Spirit and Scope of the invention as Set forth therein. under the environmental condition of 30° C. 90% RH after 50,000 copies were continuously produced, image tailing What is claimed as new and desired to be secured by Letters was observed. The abrasion loss of the photoreceptor after Patent of the united States is: 50,000 copies were continuously produced was 1.6 um. 1. An electrophotographic photoreceptor comprising: an electroconductive Substrate; and Comparative Example 6 a photoSensitive layer located overlying the electrocon 0208. The procedure for preparation and evaluation of the ductive Substrate including, photoreceptor of Example 9 were repeated except that the a charge generation layer, parts by weight of the fine particles of the alumina for the protective layer coating liquid was changed to 4 and that the a charge transport layer, and parts by weight of the adding Volume of the dispersant was a protective layer comprising a filler, changed to 0.07. wherein the filler is dispersed in the protective layer 0209. A random cross section of the protective layer of Such that in a croSS Section of the protective layer, the the thus prepared photoreceptor was observed by a SEM to filler occupies an area of from 3 to 5% of the cross investigate the dispersion conditions of the filler in the Section, protective layer. The occupation ratio of the filler in the area was 2.4%. wherein the filler has a particle diameter distribution having a peak at a diameter of from 0.2 to 0.3 um, 0210. The peak of the particle diameter distribution was and 0.3 um, and the occupation ratio of the filler having a particle diameter of not less than 0.3 um was 10% of the total area wherein particles of the filler having a particle diameter of all the fillers. of not leSS than 0.3 um occupies an area of from 10 to 30% of the area of the filler in the cross section of 0211 The quality of the produced image was good at the the protective layer. beginning, but after 50,000 copies were continuously pro 2. An image forming method comprising: duced, an apparent halftone image irregularity was charging a photoreceptor with a charger, observed. The abrasion loss of the photoreceptor after 50,000 copies were continuously produced was 4.1 um. irradiating the photoreceptor with imagewise light to form an electroStatic latent image on the photoreceptor; Comparative Example 7 developing the electroStatic latent image with a toner to 0212. The procedure for preparation and evaluation of the form a toner image on a Surface of the photoreceptor; photoreceptor of Example 10 were repeated except that the transferring the toner image to a transfer sheet; parts by weight of the adding Volume of the dispersant was changed to 0.12. fixing the toner image on the transfer sheet; and 0213. A random cross section of the protective layer of cleaning the Surface of the photoreceptor, the thus prepared photoreceptor was observed by a SEM to wherein the photoreceptor comprises: investigate the dispersion conditions of the filler in the protective layer. The occupation ratio of the filler in the area an electroconductive Substrate; and was 3.2%. a photosensitive layer located overlying the electrocon 0214. The peak of the particle diameter distribution was ductive Substrate including, 0.3 um, and the occupation ratio of the filler having a particle a charge generation layer, diameter of not less than 0.3 um was 8% of the total area of all the fillers. a charge transport layer, and 0215. The quality of the produced image was good at the a protective layer comprising a filler, beginning, but after 50,000 copies were continuously pro wherein the filler is dispersed in the protective layer duced, a halftone image irregularity was observed. When Such that in a croSS Section of the protective layer, images were produced under the environmental condition of the filler occupies an area of from 3 to 5% of the 30° C. 90% RH after 50,000 copies were continuously croSS Section, US 2002/0197549 A1 Dec. 26, 2002

wherein the filler has a particle diameter distribution wherein the filler is dispersed in the protective layer having a peak at a diameter of from 0.2 to 0.3 um, Such that in a croSS Section of the protective layer, and the filler occupies an area of from 3 to 5% of the wherein particles of the filler having a particle diam croSS Section, eter of not less than 0.3 um occupy an area of from wherein the filler has a particle diameter distribution 10 to 30% of the area of the filler in the cross having a peak at a diameter of from 0.2 to 0.3 um; Section of the protective layer. and 3. The image forming method of claim 2, further com prising: wherein particles of the filler having a particle diam eter of not less than 0.3 um occupies an area of applying a lubricant on the Surface of the photoreceptor. from 10 to 30% of the area of the filler in the cross 4. The image forming method of claim 2, wherein the Section of the protective layer. toner comprises a lubricant. 10. The image forming apparatus of claim 9, wherein the 5. The image forming method of claim 2, wherein the toner comprises a lubricant. cleaning Step comprises: 11. The image forming apparatus of claim 10, wherein the adhering the toner onto the Surface of the photoreceptor; image developer adheres the toner comprising a lubricant to and the Surface of the photoreceptor when the toner image is not formed, and wherein the cleaner collects the toner adhered collecting the toner, and on the Surface of the photoreceptor. wherein, the cleaning Step is performed at a time when the 12. The image forming apparatus of claim 9, further toner image is not formed. comprising: 6. The image forming method of claim 2, wherein the a toner feeder configured to feed a Second toner compris cleaning Step comprises: ing a lubricant to the image developer. adhering a Second toner comprising a lubricant onto the 13. The image forming apparatus of claim 12, wherein the Surface of the photoreceptor, and image developer adheres the Second toner fed by the toner feeder to the surface of the photoreceptor when the toner collecting the Second toner, image is not formed, and wherein the cleaner collects the wherein the cleaning Step is performed at a time when the Second toner adhered on the Surface of the photoreceptor toner image is not formed. 14. The image forming apparatus of claim 9, wherein the 7. The image forming method of claim 2, wherein the image developer adheres the toner to the Surface of the charging Step is performed while the charger contacts or is photoreceptor when the toner image is not formed, and located in close proximity to the photoreceptor. wherein the cleaner collects the toner adhered on the Surface 8. The image forming method of claim 2, wherein the of the photoreceptor charging Step comprises: 15. The image forming apparatus of claim 9, wherein the applying a DC voltage overlapped with an AC Voltage to charger is one of a contact charger and a proximity charger the photoreceptor by the charger. configured to charge the photoreceptor while close to but not 9. An image forming apparatus comprising: touching the Surface of the photoreceptor. 16. The image forming apparatus of claim 9, wherein the a charger configured to charge a photoreceptor; charger is configured to charge the photoreceptor by apply an image irradiator configured to irradiate the photore ing a DC voltage overlapped with an AC Voltage to the ceptor with imagewise light to form an electroStatic charging member. latent image on a Surface of the photoreceptor, 17. A process cartridge comprising: an image developer configured to develop the electroStatic a photoreceptor comprising a charge generation layer, a latent image with a toner to form a toner image on the charge transport layer and a protective layer comprising photoreceptor; a filler on an electroconductive Substrate; a transferer configured to transfer the toner image to a a charger configured to charge the photoreceptor; transfer sheet; an image irradiator configured to irradiate the photore a fixer configured to fix the toner image on the transfer ceptor with imagewise light to form an electrostatic sheet; and latent image on the photoreceptor; a cleaner configured to clean the Surface of the photore an image developer configured to develop the electrostatic ceptor, latent image with a toner to form a toner image on the wherein the photoreceptor includes, photoreceptor; an electroconductive Substrate, and a transferer configured to transfer the toner image to a a photosensitive layer located overlying the electrocon transfer sheet; and ductive Substrate including, a cleaner configured to clean the Surface of the photore a charge generation layer, ceptor, wherein the photoreceptor includes an electroconductive a charge transport layer, and Substrate and a photoSensitive layer located overlying a protective layer comprising a filler, the lectroconductive Substrate, and further comprising, US 2002/0197549 A1 Dec. 26, 2002 14

a charge generation layer, 20. The process cartridge of claim 17, wherein the toner a charge transport layer, and comprises a lubricant. 21. The proceSS cartridge of claim 20, wherein the image a protective layer comprising a filler, developer adheres the toner comprising a lubricant to the wherein the filler is dispersed in the protective layer Surface of the photoreceptor when the toner image is not Such that in a croSS Section of the protective layer, the formed, and wherein the cleaner collects the toner adhered filler occupies an area of from 3 to 5% of the cross on the Surface of the photoreceptor. Section, 22. The proceSS cartridge of claim 17, further comprising: wherein the filler has a particle diameter distribution having a peak at a diameter of from 0.2 to 0.3 um, a toner feeder configured to feed a Second toner compris and ing a lubricant to the image developer. 23. The proceSS cartridge of claim 22, wherein the image wherein particles of the filler having a particle diameter developer adheres the second toner fed by the toner feeder of not less than 0.3 um occupies an area of from 10 to 30% of the area of the filler in the cross section of to the Surface of the photoreceptor when the toner image is the protective layer. not formed and wherein the cleaner collects the Second toner 18. The process cartridge of claim 17, wherein the charger adhered on the Surface of the photoreceptor. is one of a contact charger and a proximity charger config 24. The proceSS cartridge of claim 17, wherein the image ured to charge the photoreceptor while close to but not developer adheres the toner to the Surface of the photore touching the Surface of the photoreceptor. ceptor when the toner image is not formed, and wherein the 19. The process cartridge of claim 17, wherein the charger cleaner collects the toner adhered on the Surface of the is configured to charge the photoreceptor by applying a DC photoreceptor. Voltage overlapped with an AC voltage to the charging member.