JP4648909B2 - Electrophotographic photosensitive member and image forming apparatus using the same - Google Patents

Description

  The present invention relates to an electrophotographic photosensitive member and an image forming apparatus using the same. More particularly, the present invention relates to an electrophotographic photosensitive member used for electrophotographic image formation and an image forming apparatus using the same.

  An electrophotographic image forming apparatus (hereinafter also referred to as an electrophotographic apparatus) used as a copying machine, a printer, a facsimile apparatus, or the like forms an image through the following electrophotographic process. First, a photosensitive layer of an electrophotographic photosensitive member (hereinafter also simply referred to as a photosensitive member) provided in the apparatus is uniformly charged to a predetermined potential by a charger, and a laser beam or the like irradiated from an exposure unit according to image information To form an electrostatic latent image. The developer is supplied from the developing means to the formed electrostatic latent image, and the electrostatic latent image is developed by attaching colored fine particles called toner, which is a component of the developer, to the surface of the photoreceptor. It is visualized as a toner image. The formed toner image is transferred from the surface of the photoreceptor to a transfer material such as recording paper by a transfer unit, and fixed by a fixing unit.

  During the transfer operation by the transfer means, not all the toner on the surface of the photoconductor is transferred to the recording paper and transferred, but a part of the toner remains on the surface of the photoconductor. Further, the paper dust of the recording paper that comes into contact with the photoconductor during transfer may remain attached to the surface of the photoconductor. Such foreign matters such as residual toner and adhered paper dust on the surface of the photoconductor adversely affect the quality of the formed image and are removed by the cleaning device. In recent years, cleaner-less technology has advanced, and residual toner is collected by a so-called developing and cleaning system, which is a cleaning function added to the developing means without having an independent cleaning means. After the surface of the photoreceptor is cleaned in this way, the surface of the photosensitive layer is neutralized by a static eliminator or the like, and the electrostatic latent image disappears.

  An electrophotographic photoreceptor used in such an electrophotographic process is configured by laminating a photosensitive layer containing a photoconductive material on a conductive substrate made of a conductive material. Conventionally, an electrophotographic photosensitive member using an inorganic photoconductive material (hereinafter referred to as an inorganic photosensitive member) has been used as the electrophotographic photosensitive member. As a typical inorganic photoreceptor, a selenium photoreceptor using a layer made of amorphous selenium (a-Se) or amorphous selenium arsenic (a-AsSe) as a photosensitive layer, zinc oxide (chemical formula: ZnO) Alternatively, a layer made of zinc oxide-based or cadmium sulfide-based photosensitive member using cadmium sulfide (chemical formula: CdS) dispersed in a resin together with a sensitizer such as a dye as a photosensitive layer, and a layer made of amorphous silicon (a-Si) There are amorphous silicon type photoconductors (hereinafter referred to as a-Si photoconductors) used for the photosensitive layer.

  However, inorganic photoreceptors have the following drawbacks. Selenium photoreceptors and cadmium sulfide photoreceptors have problems with heat resistance and storage stability. Since selenium and cadmium are toxic to the human body and the environment, photoreceptors using these must be recovered after use and disposed of properly. Also, zinc oxide photoconductors have the disadvantages of low sensitivity and low durability, and are rarely used at present. In addition, the a-Si photoreceptor, which is attracting attention as a non-polluting inorganic photoreceptor, has advantages such as high sensitivity and high durability, but is manufactured using a plasma chemical vapor deposition method. It is difficult to form a uniform film, and image defects are likely to occur. In addition, the a-Si photosensitive member has disadvantages that productivity is low and manufacturing cost is high.

As described above, since the inorganic photoreceptor has many drawbacks, development of a photoconductive material used for the electrophotographic photoreceptor has progressed, and instead of the inorganic photoconductive material conventionally used, An organic photoconductive material, that is, an organic photoconductor (abbreviation: OPC) is frequently used. An electrophotographic photoreceptor using an organic photoconductive material (hereinafter referred to as an organic photoreceptor) has some problems in sensitivity, durability, environmental stability, etc., but is toxic, manufacturing cost and material design. In terms of the degree of freedom, etc., there are many advantages over inorganic photoreceptors. The organic photoreceptor also has an advantage that the photosensitive layer can be formed by an easy and inexpensive method typified by a dip coating method. Because of these many advantages, organic photoreceptors are gradually becoming the mainstream of electrophotographic photoreceptors. Also, due to recent research and development, the sensitivity and durability of organic photoreceptors have been improved, and at present, organic photoreceptors have been used as electrophotographic photoreceptors except in special cases. Yes.

  In particular, the performance of organic photoreceptors has been remarkably improved by the development of function-separated photoreceptors in which a charge generation function and a charge transport function are assigned to different substances. In addition to the above-mentioned advantages of the organic photoconductor, the function-separated type photoconductor has an advantage that a photoconductor having an arbitrary characteristic can be relatively easily manufactured with a wide selection range of materials constituting the photosensitive layer. ing.

  There are two types of function-separated type photoreceptors: a laminated type and a single layer type. In the laminated type functionally separated photoreceptor, a laminated photosensitive layer in which a charge generation layer containing a charge generation material responsible for charge generation and a charge transport layer containing a charge transport material responsible for a charge transport function are laminated Is provided. The charge generation layer and the charge transport layer are usually formed in a form in which the charge generation material and the charge transport material are each dispersed in a binder resin as a binder. In addition, in the single layer type functional dispersion type photoreceptor, a single layer type photosensitive layer in which a charge generation material and a charge transport material are dispersed together in a binder resin is provided.

  In the electrophotographic apparatus, the above-described charging, exposure, development, transfer, cleaning, and charge removal operations are repeatedly performed on the photosensitive member under various environments. Therefore, in addition to high sensitivity and excellent photoresponsiveness, the photoreceptor is required to have excellent environmental stability, electrical stability, and durability (press life) against mechanical external force. Specifically, it is required that the surface layer of the photoreceptor is not easily worn by rubbing with a cleaning member or the like.

  As prior art for improving the printing durability of the photosensitive layer, there is a technique for providing a protective layer on the outermost surface layer of the photoreceptor (Patent Document 1), a technique for imparting lubricity to the protective layer (Patent Document 2), and protection. A technique for curing a layer (Patent Document 3) and a technique for containing filler particles in a protective layer (Patent Document 4) are known. These protective layers are basically desired to be as thin as possible from the viewpoint of not inhibiting the basic function of the photosensitive layer. In addition, the provision of the protective layer causes various harmful effects. For example, when the photoreceptor and the protective layer have a discontinuous layer structure, the protective layer may be peeled off due to long-term use. In addition, the exposed portion potential increases due to repeated use over a long period of time. On the contrary, when the protective layer and the photosensitive layer are dissolved in a continuous layer structure, that is, when the photosensitive layer is dissolved by the protective layer coating solution to be subsequently applied, the image characteristics of the photosensitive layer are deteriorated depending on the dissolution state.

  Among them, the technology for incorporating filler particles gives a new influencing factor on the characteristics of the photoreceptor, that is, control of the dispersibility of the filler particles. That is, the characteristics cannot be defined only by the amount of filler particles added. Patent Document 5 discloses that the printing durability is improved by adding up to about 0.1 to 10% by weight with respect to the total solid content of the protective layer. However, for example, it is easily presumed that protective layers having completely different dispersion states have different image characteristics / electrical characteristics / printing durability of the photoconductor even with the same addition amount. In addition, when the dielectric constant of the protective layer is nonuniform, image thickening and toner scattering may occur at the edge when black solid images are output, and the dispersion state of the filler particles inside the protective layer is thus considered to be a photoconductor. It can be seen that this greatly affects the properties of

When printing durability is improved, as an adverse effect, image blur and image flow due to the influence of a charged product or the like adhering to the surface of the photoreceptor (drum) occur particularly under high temperature and high humidity. In order to eliminate these adverse effects, a technique for providing a uniform and inactive drum surface by a method of designing a photoconductor that “shaves” to some extent or a method of devising a cleaning means is disclosed (Patent Document 6). .
In the function-separated type photoconductor, if a wear-resistant effect can be imparted to the outermost surface, an extra step is not included in the production process, so that there is a great cost advantage compared to the case where a protective layer is imparted. Further, it is possible to avoid the above-described adverse effects caused by providing the photosensitive layer and the protective layer in a stacked manner. However, on the other hand, it is necessary to consider new issues on the system. For example, when filler particles are added to improve the printing durability, traps over the entire charge transport layer of several tens of μm occur between the filler particles and the polymer bulk (binder resin) contained in the photosensitive layer. As a result, the risk of increasing the residual potential of the exposed portion becomes extremely large as compared with the case where it is added to the protective layer. In addition, in the case of a multilayer photoreceptor, image defects may occur due to non-uniformity of the layer in the vicinity of the interface between the charge generation layer and the charge transport layer, which may be due to the interaction between the filler particles and the charge generation layer. is there.

  Conventionally, it has been practiced to enhance the printing durability of a photoreceptor and to specify the physical properties of the photoreceptor surface where scratches or the like do not occur over a long period of time. Not only the physical properties of the surface of the electrophotographic photoreceptor, but also one of the indices for evaluating material properties, particularly mechanical properties, is hardness. Hardness is defined as the stress from the material against the indentation of the indenter. Attempts have been made to quantify the mechanical properties of the film constituting the surface of the electrophotographic photosensitive member by using this hardness as a physical parameter for knowing the physical properties of the material. For example, a scratch strength test, a pencil hardness test, a Vickers hardness test, and the like are widely known as test methods for measuring hardness. However, in any of the hardness tests, there is a problem in measuring the mechanical properties of a material that exhibits complicated behavior such as plasticity and elasticity (including a delay component), such as a film composed of an organic substance.

  For example, the Vickers hardness test evaluates the hardness by measuring the length of an indentation on the film. However, this reflects only the plasticity of the film, and it is impossible to accurately evaluate the mechanical properties of a deformed form including a large proportion of elastic deformation such as organic matter. Therefore, the mechanical properties of the film composed of organic materials must be evaluated in consideration of various properties.

In view of the above situation, in an electrophotographic photosensitive member having an organic photosensitive layer as the outermost surface layer, the physical properties for judging the long-term wear resistance, durability and operational stability of the organic photosensitive layer are, for example, plastic work The rate (plastic deformation rate, η _plast ,%), elastic power (elastic deformation rate, η _HU ,%), and the like are known (for example, Patent Document 7). The plastic work rate is a percentage of the ratio of the plastic deformation work to the sum of the plastic deformation work (energy required for plastic deformation) and the elastic work (energy required for elastic deformation). Further, the elastic work rate is a percentage of the ratio of the elastic deformation work to the sum of the plastic deformation work and the elastic work. Therefore, the sum of the plastic power and the elastic power is 100 (%).

In Patent Document 8, specifically, the elastic work rate (elastic deformation rate) is set to 48 to 65%, and the universal hardness value (Hu) by the universal hardness test specified in DIN 50359-1 is set. It is described that it is set to 150 to 220 N / mm ² . Furthermore, it is described that the mechanical deterioration of the outermost surface layer is prevented by defining that Hu is larger than that of the intermediate transfer member.

However, when mixed with structures such as the above filler particles that have extremely different mechanical property values from the surrounding organic composition such as resin, the property values required for the outermost surface layer also change naturally. Will be. In patent document 9, the mechanical characteristic value of the surface layer containing filler particles is defined by the above plastic deformation rate and Hu. However, when the specified mechanical property value Hu is realized by a coating mainly composed of a combination of a conventional binder resin and filler particles, the hardness is conspicuous and the brittleness may be deteriorated. Is considered difficult to maintain.

  On the other hand, as a means to ensure image stability over a long period of time, the surface free energy of the outermost surface layer is reduced (lower γ), and the adhesion to various contact members such as toner and cleaning blades is reduced. A means having the cleanliness of the outermost surface layer is conceivable. As a typical example, there is a means of providing a silicone or fluorine-based modifying group in the resin of the outermost surface layer to reduce the gamma (Patent Document 10). Moreover, the same improvement effect is found by adding fluorine-based fine particles and the like. Furthermore, the surface free energy can also be reduced by forcing a long-chain fatty acid salt to adhere to the outermost surface layer from the outside. By performing these processes, high-quality image formation is realized. However, in using these, there is a drawback that it is difficult to ensure a stable characteristic value over a long period of time due to, for example, wear and deterioration of the resin component. For this reason, the increase in the number of sheets used causes deterioration of the cleaning property and the image quality deteriorates. In addition, in the case of attaching to the surface from the outside, securing a stable supply means becomes an issue, and realization of a stable low-gamma surface is a substantially difficult issue.

Japanese Unexamined Patent Publication No. 57-30846 JP-A-1-23259 JP 61-72256 A JP-A-1-172970 JP-A-1-205171 JP 2004-61560 A JP 2002-6526 A JP 2005-250455 A JP 2004-212562 A JP 2004-205542 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide an electrophotographic photosensitive member that is excellent in mechanical / electrical durability and capable of outputting a highly durable image without abnormal images even when used repeatedly for a long time, and an image forming apparatus using the same. Is to provide.

Thus, according to the present invention, an electrophotographic photosensitive member having at least a charge generation layer and a charge transport layer in this order on a conductive substrate,
The outermost surface layer of the electrophotographic photoreceptor contains filler particles,
The filler particles in the primary dispersion coating solution for the charge transport layer for forming the outermost surface layer are measured by a light scattering particle size distribution measuring device, and the dispersion state corresponding to the primary particle diameter is maintained.
Filler particles in the outermost surface layer are represented by the following formula (1).
1.0 × 10 ⁻³ ≦ (df × b ³ ) / (dm × a ³ ) ≦ 2.5 × 10 ^-2 (1)
(In the formula, a means the average distance between filler particles (nm), b means the average filler particle diameter (nm), df means the density of filler particles (g / cm ³ ), and dm is the maximum. plus average density of the solid surface layer fraction (g / cm ^{3) of} means) fully,
The outermost surface layer, the surface film hardness test (test conditions: 25 ℃ / 50% RH, the maximum load: 5 mN) when subjected ^{to, 200N / mm 2 ~350N / mm} 2 plastic hardness value (Hpl), An electrophotographic photosensitive member having an elastic power of 40% to 60% is provided.
Furthermore, according to the present invention, there is provided an image forming apparatus comprising a photoconductor, a charging unit, an exposure unit, a developing unit, and a transfer unit, wherein the photoconductor includes the electrophotographic photoconductor.

  According to the present invention, an electrophotographic photosensitive member that has excellent printing durability, does not cause image defects due to sudden scratches, etc., even over long-term use, and retains electrical stability, and the same are used. An image forming apparatus can be provided.

Hereinafter, the present invention will be described in detail.
FIG. 1 is a partial cross-sectional view showing a simplified configuration of an electrophotographic photosensitive member 1 according to a first embodiment of the present invention. The electrophotographic photoreceptor 1 (hereinafter abbreviated as “photoreceptor”) of this embodiment is a cylindrical conductive substrate 11 made of a conductive material and a layer laminated on the outer peripheral surface of the conductive substrate 11. A charge generation layer 12 containing a charge generation material, and a charge transport layer 13 which is further laminated on the charge generation layer 12 and contains a charge transport material. The charge generation layer 12 and the charge transport layer 13 constitute a photosensitive layer 14. That is, the photoreceptor 1 is a multilayer photoreceptor.
Further, as shown in FIG. 4, a laminated type photoreceptor in which an intermediate layer 15 is provided between the conductive substrate 11 and the charge generation layer 12 may be used.

(Conductive substrate)
The conductive substrate 11 serves as an electrode of the photoreceptor 1 and also functions as a support member for the other layers 12 and 13. In addition, although the shape of the electroconductive base | substrate 11 is cylindrical shape in FIG. 1, it is not limited to this, A column shape, a sheet form, an endless belt shape, etc. may be sufficient.

  As the conductive material constituting the conductive substrate 11, for example, a single metal such as aluminum, copper, zinc, nickel, or titanium, or an alloy such as an aluminum alloy or stainless steel can be used. Also, without being limited to these metal materials, metal (aluminum, gold, silver, copper, zinc, nickel, titanium) foil on the surface of polymer materials such as polyethylene terephthalate, nylon or polystyrene, hard paper or glass Laminated, metal (aluminum, gold, silver, copper, zinc, nickel, titanium) vapor deposited material, or conductive polymer, tin oxide, indium oxide or other conductive compound layer deposited or applied A thing etc. can also be used. These conductive materials are used after being processed into a predetermined shape.

  If necessary, the surface of the conductive substrate 11 is irregularly reflected within a range that does not affect the image quality, such as anodic oxide film treatment, surface treatment with chemicals or hot water, coloring treatment, or roughening the surface. Processing may be performed. In an electrophotographic process using a laser as an exposure light source, the wavelengths of the laser light are uniform. For this reason, the laser beam reflected on the surface of the photoconductor and the laser beam reflected inside the photoconductor cause interference, and interference fringes due to this interference may appear on the image, resulting in an image defect. By performing the above-described treatment on the surface of the conductive substrate 11, image defects due to interference of laser light having the same wavelength can be prevented.

(Charge generation layer)
The charge generation layer 12 contains, as a main component, a charge generation material that generates charges by absorbing light. The main component means that the component contains an amount capable of expressing its main function. Substances effective as a charge generation substance include monoazo pigments, bisazo pigments, azo pigments such as trisazo pigments, indigo pigments such as indigo or thioindigo, perylene pigments such as peryleneimide or perylene anhydride, anthraquinone or Polycyclic quinone pigments such as pyrenequinone, phthalocyanine pigments such as metal phthalocyanine or metal-free phthalocyanine, triphenylmethane dyes represented by methyl violet, crystal violet, knight blue, victoria blue, erythrosine, rhodamine B, rhodamine 3R Acridine dyes typified by acridine orange, frappeosin, thiazine dyes typified by methylene blue, methylene green, oxazine dyes typified by capri blue, meldra blue, etc. Qualylium dyes, pyrylium salts and thiopyrylium salts, thioindigo dyes, bisbenzimidazole dyes, quinacridone dyes, quinoline dyes, lake dyes, azo lake dyes, dioxazine dyes, azurenium dyes, triallylmethane dyes, xanthenes Examples thereof include organic photoconductive materials such as cyano dyes, cyanine dyes, and triphenylmethane dyes, and inorganic photoconductive materials such as selenium and amorphous silicon. These charge generation materials may be used alone or in combination of two or more.
Among the above charge generation materials, the following general formula (A):

(Wherein, X ¹ , X ² , X ³ and X ⁴ each represent a halogen atom, an alkyl group or an alkoxy group, and r, s, y and z each represents an integer of 0 to 4)
It is preferable to use an oxotitanium phthalocyanine compound represented by the formula:
Examples of the halogen atom represented by X ¹ , X ² , X ³ and X ⁴ in the general formula (A) include fluorine, chlorine, bromine and iodine atoms.
Examples of the alkyl group represented by X ¹ , X ² , X ³ and X ⁴ include C _{1 to} C ₄ alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, and t-butyl groups. It is done.
Further, the alkoxy groups represented by X ¹ , X ² , X ³ and X ⁴ include C ₁ -C ₄ alkoxy groups such as methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, and t-butoxy groups. Can be mentioned.

  Since the oxotitanium phthalocyanine compound represented by the general formula (A) is a charge generation material having high charge generation efficiency and high charge injection efficiency, the charge generation layer 12 using the compound absorbs light. As a result, a large amount of charge is generated, and the generated charge can be efficiently injected into the charge transport material contained in the charge transport layer 13 without being accumulated therein, and is smoothly transported to the surface of the photosensitive layer 14.

  Examples of the oxotitanium phthalocyanine compound represented by the general formula (A) include Moser, Frank H, and Arthur L., et al. Phthalocyanine Compounds by Thomas, Reinhold Publishing Corp. , New York, 1963, and the like.

For example, among the oxotitanium phthalocyanine compounds represented by the general formula (A), in the case of unsubstituted oxotitanium phthalocyanine in which r, s, y, and z are 0, phthalonitrile and titanium tetrachloride are heated and melted. Or dichlorotitanium phthalocyanine is synthesized by heating in a suitable solvent such as α-chloronaphthalene and then hydrolyzed with a base or water.
Alternatively, oxotitanium phthalocyanine can be produced by reacting isoindoline with titanium tetraalkoxide such as tetrabutoxytitanium in a suitable solvent such as N-methylpyrrolidone.

Examples of optional components other than the charge generation material contained as the main component include sensitizing dyes, binder resins, antioxidants, leveling agents, and plasticizers.
Examples of sensitizing dyes include triphenylmethane dyes such as methyl violet, crystal violet, knight blue and victoria blue, erythrosine, rhodamine B, rhodamine 3R, acridine dyes such as acridine orange and frapeosin, methylene blue and Examples include thiazine dyes typified by methylene green, oxazine dyes typified by capri blue and meldra blue, cyanine dyes, styryl dyes, pyrylium salt dyes, and thiopyrylium salt dyes. The sensitizing dye is preferably used in a proportion of 10 parts by weight or less, more preferably in a proportion of 0.5 to 2.0 parts by weight with respect to 100 parts by weight of the charge generating substance.

  As a method for forming the charge generation layer 12, the above-described charge generation material is vacuum-deposited on the surface of the conductive substrate 11, or the charge generation layer coating obtained by dispersing the above-described charge generation material in a suitable solvent. The method etc. which apply | coat a liquid to the surface of the electroconductive base | substrate 11 are mentioned. Among these, in a binder resin solution obtained by mixing a binder resin as a binder in a solvent, a charge generating material is dispersed by a conventionally known method to prepare a coating solution for a charge generating layer, A method of applying the obtained coating solution to the surface of the conductive substrate 11 is preferably used. Hereinafter, this method will be described.

  Examples of the binder resin used for the charge generation layer 12 include polyester resin, polystyrene resin, polyurethane resin, phenol resin, alkyd resin, melamine resin, epoxy resin, silicone resin, acrylic resin, methacrylic resin, polycarbonate resin, and polyarylate resin. , Phenoxy resins, polyvinyl butyral resins and polyvinyl formal resins, and copolymer resins containing two or more of the repeating units constituting these resins. Specific examples of the copolymer resin include insulating resins such as vinyl chloride-vinyl acetate copolymer resin, vinyl chloride-vinyl acetate-maleic anhydride copolymer resin, and acrylonitrile-styrene copolymer resin. Can do. The binder resin is not limited to these, and a commonly used resin can be used as the binder resin. One kind of these resins may be used alone, or two or more kinds thereof may be mixed and used.

  Examples of the solvent for the charge generation layer coating solution include halogenated hydrocarbons such as tetrachloropropane and dichloroethane, ketones such as acetone, isophorone, methyl ethyl ketone, acetophenone, and cyclohexanone, and esters such as ethyl acetate, methyl benzoate, and butyl acetate. , Tetrahydrofuran (THF), dioxane, dibenzyl ether, ethers such as 1,2-dimethoxyethane or dioxane, aromatic hydrocarbons such as benzene, toluene, xylene, mesitylene, tetralin, diphenylmethane, dimethoxybenzene, dichlorobenzene , Sulfur-containing solvents such as diphenyl sulfide, fluorine-based solvents such as hexafluoroisopropanol, and aprotic polar solvents such as N, N-dimethylformamide or N, N-dimethylacetamide are used. . Moreover, the solvent which mixed 2 or more types of these solvents can also be used. Among these solvents, non-halogen organic solvents are preferably used in consideration of the global environment.

In the charge generation layer 12 including the charge generation material and the binder resin, the ratio W1 / W2 between the weight W1 of the charge generation material and the weight W2 of the binder resin is 10/100 (10/100). It is preferably 200/100 or less (200/100) or less. If the ratio W1 / W2 is less than 10/100, the sensitivity of the photoreceptor 1 may be lowered, which is not preferable. When the ratio W1 / W2 exceeds 200/100, not only the film strength of the charge generation layer 12 decreases, but also the dispersibility of the charge generation material may decrease and coarse particles may increase. For this reason, surface charges other than those that should be erased by exposure are reduced, and image fogging, particularly fogging of an image called black spots where toner adheres to a white background and minute black spots are formed may increase. The ratio W1 / W2 is more preferably 50/100 or more and 150/100 or less.

The charge generation material may be previously pulverized by a pulverizer before being dispersed in the binder resin solution. Examples of the pulverizer used for the pulverization treatment include a ball mill, a sand mill, an attritor, a vibration mill, and an ultrasonic disperser.
Examples of the disperser used when dispersing the charge generating substance in the binder resin solution include a paint shaker, a ball mill, and a sand mill. As a dispersion condition at this time, it is preferable to select an appropriate condition so that impurities are not mixed due to wear of members constituting the container and the disperser.

  Examples of the coating method for the charge generation layer coating liquid include a spray method, a bar coating method, a roll coating method, a blade method, a ring method, and a dip coating method. Among these coating methods, an optimum method can be selected in consideration of the physical properties and productivity of coating. Among these coating methods, the dip coating method is a method in which a substrate is immersed in a coating tank filled with a coating solution, and then a layer is formed on the surface of the substrate by pulling it up at a constant speed or a sequentially changing speed. It is. As described above, the dip coating method is relatively simple and excellent in terms of productivity and cost. Therefore, it is frequently used for producing an electrophotographic photosensitive member. In addition, in order to stabilize the dispersibility of a coating liquid, the apparatus used for the dip coating method may be provided with a coating liquid dispersing apparatus represented by an ultrasonic generator.

  The film thickness of the charge generation layer 12 is preferably 0.05 μm or more and 5 μm or less, and more preferably 0.1 μm or more and 1 μm or less. If the film thickness of the charge generation layer 12 is less than 0.05 μm, the light absorption efficiency is lowered, and the sensitivity of the photoreceptor 1 may be lowered, which is not preferable. If the thickness of the charge generation layer 12 exceeds 5 μm, the charge transfer within the charge generation layer 12 becomes the rate-determining step in the process of erasing the surface charge of the photosensitive layer 14, and the sensitivity of the photoreceptor 1 may decrease. It is not preferable.

(Charge transport layer)
A charge transport layer 13 is provided on the charge generation layer 12. The charge transport layer 13 is mainly composed of a charge transport material having the ability to accept and transport the charge generated by the charge generation material contained in the charge generation layer 12, and filler particles that improve the durability of the photoreceptor. In addition, it can optionally comprise a charge transport material and a binder resin that binds the filler particles. The binder resin is preferably contained in the range of 30 to 80% by weight with respect to the entire charge transport layer. In addition to the charge transport material, the filler particles, and the binder resin, an antioxidant, an ultraviolet absorber, a leveling agent, a plasticizer, and the like may be included. As the charge transport material, a hole transport material and an electron transport material can be used.

Examples of hole transport materials include carbazole derivatives, pyrene derivatives, oxazole derivatives, oxadiazole derivatives, thiazole derivatives, thiadiazole derivatives, triazole derivatives, imidazole derivatives, imidazolone derivatives, imidazolidine derivatives, bisimidazolidine derivatives, styryl compounds, hydrazone compounds, Polycyclic aromatic compounds, indole derivatives, pyrazoline derivatives, oxazolone derivatives, benzimidazole derivatives, quinazoline derivatives, benzofuran derivatives, acridine derivatives, phenazine derivatives, aminostilbene derivatives, triarylamine derivatives, triarylmethane derivatives, phenylenediamine derivatives, stilbene Derivatives, enamine derivatives, benzidine derivatives and the like. Examples of the polymer having a group derived from these compounds in the main chain or side chain include, for example, poly-
Examples thereof include N-vinylcarbazole, poly-1-vinylpyrene, ethylcarbazole-formaldehyde resin, triphenylmethane polymer, poly-9-vinylanthracene, and polysilane.

  Examples of the electron transport material include organic compounds such as benzoquinone derivatives, tetracyanoethylene derivatives, tetracyanoquinodimethane derivatives, fluorenone derivatives, xanthone derivatives, phenanthraquinone derivatives, phthalic anhydride derivatives, and diphenoquinone derivatives.

The charge transport materials are not limited to those listed here, and can be used alone or in admixture of two or more.
Furthermore, as a charge transport material, a compound represented by the following general formula (1) that is resistant to gases such as ozone and NOx generated in the electrophotographic process

(In the formula, R ₁ and R ₂ each represents an alkyl group having 1 to 4 carbon atoms which may be the same or different from each other, or R ₁ and R ₂ are bonded to each other to form a heterocyclic group containing a nitrogen atom. N represents an integer of 1 to 4 and Ar represents an aromatic ring group having a substituted butadienyl group, thereby forming a stable photoreceptor with little image deterioration even after repeated use. It becomes possible to do.

  The binder resin constituting the charge transport layer 13 is not particularly limited, and any resin known in the art can be used. In particular, a resin containing polycarbonate as a main component is preferable for reasons such as improved solubility in organic solvents and improved transparency of the coating film. Here, the main component means to occupy 50% by weight or more of the binder resin, and more preferably in the range of 60 to 100% by weight.

  Examples of resins other than polycarbonate include vinyl polymer resins such as polymethyl methacrylate resin, polystyrene resin, polyvinyl chloride resin, and the like, copolymer resins containing two or more of repeating units constituting these, and polyester resins, Polyester carbonate resin, polysulfone resin, phenoxy resin, epoxy resin, silicone resin, polyarylate resin, polyamide resin, methacrylic resin, acrylic resin, polyether resin, polyurethane resin, polyacrylamide resin, phenol resin, polyphenylene oxide resin, etc. . Moreover, the thermosetting resin which partially bridge | crosslinked these resin is also mentioned. These resins may be used alone or in a mixture of two or more.

Furthermore, the filler particles constituting the charge transport layer 13 are roughly classified into organic fillers and inorganic fillers centered on metal oxides. In general, organic fillers, mainly fluorine-based materials, are used for the purpose of controlling the wettability of the photoreceptor surface and suppressing adhesion of foreign substances, etc., and inorganic fillers are mainly used for the purpose of improving printing durability. Used for. In the present invention, it is preferable to use an inorganic filler. As the inorganic filler, a material having high hardness as a material and easily dispersible in the binder resin is preferable. Examples thereof include oxides such as silicon oxide (silica), titanium oxide, zinc oxide, calcium oxide, and aluminum oxide (alumina), and nitride compounds such as silicon nitride and aluminum nitride. In particular, silicon oxide (silica) having a small difference from the refractive index of components other than the filler particles is suitable as a result of considering light scattering in the charge transport layer.

Since filler particles have a great influence on wear resistance and electrical stability, the filler particles are not simply added, but are defined by the following formula (1) in which the particles are uniformly dispersed and the dispersion state is taken into account. In a range of amounts. When the amount is within this range, a photoreceptor showing good printing durability can be obtained.
1.0 × 10 ⁻³ ≦ (df × b ³ ) / (dm × a ³ ) ≦ 2.5 × 10 ^-2 (1)
In the above formula, a is the average distance between filler particles (nm), b is the average filler particle diameter (nm), df is the density of filler particles (g / cm ³ ), and dm is the average density of solid content in the outermost surface layer ( g / cm ³ ). In addition, a, b, df, and dm can be measured by the following method.

In addition, it is preferable to accurately measure a by TEM cross-sectional observation, but if a uniform dispersion state can be confirmed, a may be obtained as a calculated value from the amount of filler particles added and the volume of the coating film as a medium. .
Although b can be calculated | required correctly by SEM observation, if it is a commercially available filler particle, you may quote from a catalog value.
df may be calculated by measuring the volume and weight of the filler particles before production, or may be a catalog value for a commercial product.
The dm can be obtained by measuring and calculating the volume and weight of the coating film.
Here, the solid content of the outermost surface layer is a coating film of the charge transport layer obtained by applying a coating liquid and drying the solvent to solidify.

  The uniform dispersion state means that the state close to the primary particle diameter in FIG. 2 in the coating solution is fixed even after solidifying as a coating film, and the average particle diameter of the particles in the coating film is the same as before preparation. This refers to a state that is approximately equal to the primary particle diameter of the raw material particles. That is, in this equation, it is assumed that the filler particles are true spheres and have no particle size distribution in a homogeneous solid medium, and these particles are uniformly dispersed in the medium. If the addition amount / particle diameter / density of the filler particles and the density of the medium (more precisely, the density of the entire solid content including the filler particles) are determined, a: the average distance between the filler particles is determined. By substituting the obtained value a into the formula (1), it can be determined whether or not the filler particles satisfy the formula (1).

In other words, equation (1) assumes that the filler particles are uniformly “distributed”. Therefore, in this invention, the addition density | concentration of a filler particle is prescribed | regulated so that dispersion | distribution of the filler particle in a coating liquid / coating film may be uniform, and the said Formula (1) may be satisfy | filled.
Here, a is preferably small in order to minimize the adverse effects on light scattering and electrical carriers (electrons and / or holes) in the system. Specifically, 400 nm or less (primary particle diameter) is preferable. More preferably, the range of a is 20 to 200 nm.

The range of b is preferably 5 to 100 nm, and more preferably 5 to 20 nm. Preferably the range of df is 1.5~7g / cm ^3, more preferably 1.5~3g / cm ^3. Preferably the range of dm is 1 to 2 g / cm ^3, more preferably 1-1.5 g / cm ^3.

In adding the filler particles, various dispersion methods such as a ball mill, a sand mill, an attritor, a vibration mill, an ultrasonic disperser, or a paint shaker can be used to form a uniform particle dispersion state. In order to draw out the excellent characteristics of the electrophotographic photosensitive member, it is desired to grasp the dispersion state in the dispersion liquid for forming the coating film on the outermost surface of the electrophotographic photosensitive member or after the formation of the coating film. In FIG. 2, the same coating solution formulation (polycarbonate resin GH503: manufactured by Idemitsu Kosan Co., Ltd. and TS2040: manufactured by Teijin Chemicals, respectively, 1.55 g and silica (T
S-610: manufactured by Cabot Specialty Chemicals: primary particle size of 17 μm) 3.1 g mixed with 55.9 g of tetrahydrofuran), when two types of dispersion were performed, the particle size distribution state in the coating solution after the dispersion treatment The differences are being compared. In FIG. 2, ◆ indicates the particle size distribution of the silica particles in the primary dispersion coating solution for charge transport layer obtained by dispersing for 5 hours with a ball mill, and □ indicates the coating obtained by dispersing for 5 hours with a paint shaker. The particle size distribution of the silica particle in a liquid is shown. It can be seen that ♦ is stably dispersed to a state close to the primary particle diameter, while □ indicates that micron-order aggregates are formed. Although it is certain that □ indicates that an aggregate is formed by reaggregation, the detailed cause for obtaining this state has not been elucidated. The change in the aggregation state as shown in FIG. 2 directly corresponds to the electrical properties and surface uniformity of the final coating film, and the formation of a uniform dispersion in the dispersion and close to the primary particle diameter Reflected. Therefore, the ◆ dispersion method is preferable because an outermost surface layer having excellent durability can be formed as a result.

In the above, preferred examples of unaggregated filler particles have been given. However, an aggregate of filler particles may be used as long as the formula (1) is satisfied. In the case of an aggregate, “filler particles” in a, b, and df in the formula (1) shall be read as “aggregate”. Moreover, although the dispersion process by a paint shaker is performed on the conditions in which an aggregate is formed in the above, it can also be made to disperse | distribute to the state close | similar to a primary particle diameter by changing conditions.
In addition, the dispersion state of the filler particles in the coating liquid can be evaluated using, for example, a light scattering particle size distribution measuring apparatus.

  However, if only the state of addition of these filler particles is maintained, sudden scratches or the like may occur and image stability over a long period of time may be impaired. That is, it is desired that the coating film of the organic compound mainly composed of the filler particles and the thermoplastic resin surrounding the filler particles has desired mechanical properties.

The elastic power η _HU will be described below. When a solid material is subjected to an indentation load, only a part of the mechanical work W _total consumed by the load is used as plastic deformation work (energy required for plastic deformation) W _plast , and the rest is used when removing the load. The elastic recovery work (elastic deformation work; energy required for elastic deformation) W _elast is released.
The elastic recovery work (elastic deformation work) W _elast includes an instantaneous elastic deformation component and a delayed elastic deformation component.
The elastic power η _HU represents the degree of viscoelasticity of the material and is a parameter that contributes to the elastic recovery of the material. The elastic power η _HU in the present embodiment is obtained as follows.

  The hysteresis line 8 shown in FIG. 3 is obtained from the surface film hardness test. The indentation process (A → B) from the start of the indentation load to the surface of the photoreceptor 1 until the maximum indentation load Fmax is reached (A → B), the indentation maximum Deformation of the unloading process (C → D) from the start of unloading until the load reaches zero (0) until the unloading is completed (B → C). (Indentation depth change) History. In FIG. 3, the vertical axis represents the load (Force), and the horizontal axis represents the repulsive indentation depth (Disp).

In this hysteresis line 8, since the mechanical work amount W _total is W = ∫Fdh, it is represented by the area surrounded by the indentation depth curve (A → B) and the indentation depth h ₁ during the load increase. Among them, the elastic recovery work amount W _elast is expressed by an area surrounded by an indentation depth curve (C → D) and an indentation depth h ₂ during load removal. The ratio of this work is the elastic work η _HU , and the formula (2):
η _HU = W _elast / W _total × 100 (%) (2)
(However, W _total = W _elast + W _plast Is)
Represented by

On the other hand, the hardness value (Hplast) of plastic deformation is given from FIG. That is, in FIG. 3, from the indentation surface area A and the maximum indentation load Fmax at the intersection (hr) between the C intercept of the unloading curve and the X axis when unloading from the maximum indentation position (C), the plasticity is expressed by the following equation. Hardness Hplast is required.
Hplast ＝ Fmax / A (hr)
In the formula, Fmax: maximum indentation load, A (hr): indentation surface area at rebound indentation depth hr.

The elastic power η _HU and the plastic deformation hardness value Hplast can be obtained by a device capable of evaluating the above history by contacting a diamond pyramid indenter (Vickers indenter), for example, a Fischer scope H100V. Of these, the indentation surface area can be determined by measuring the prescribed indenter shape and the surface roughness of the sample surface after measurement.

  It is considered that the main factor for improving the durability of the photoreceptor is to minimize the rubbing of the surface of the photoreceptor due to contact with the cleaning blade and the toner. That is, it is ideal that the surface of the photoreceptor behaves as an elastic body with respect to the force applied during rubbing. However, it is difficult to set conditions for the surface of the photoreceptor mainly composed of organic polymers to behave as an elastic body because of the molecular structure. When the rubber elasticity is forcibly added, the instantaneous elasticity is lowered and the delay elasticity is improved, so that a new adverse effect such as a reduction in cleaning performance appears.

  On the other hand, improvement of the instantaneous elasticity of a coating film mainly composed of a thermoplastic polymer such as polycarbonate generally promotes improvement of the hardness value of plastic deformation. However, an excessive increase in hardness results in a decrease in brittleness. As a result, density unevenness or the like due to generation of scratches or the like occurs, leading to a decrease in printing durability as a photoreceptor.

Therefore, in view of the characteristics of the material on the surface of the organic photoreceptor to which the filler particles are added, the present inventors have conducted extensive studies. As a result, the outermost surface layer of the organic photoreceptor has an elastic power of 40% to 60%. It was found that η _HU is suitable when the plastic deformation hardness value Hplast is 200 N / mm ² or more and 350 N / mm ² or less (test conditions: 25 ° C./50% RH, maximum load: 5 mN). . A more preferable elastic power η _HU is 45 to 60%. A more preferable plastic deformation hardness value Hplast is 250 to 350 N / mm ² .

  In adjusting these physical property values, the charge transfer agent, filler particle type, resin type, and the amount of each component added vary greatly, and simple additivity may not be established depending on the degree of interaction between these components. Absent. However, experimentally, it is often possible to obtain a value close to the physical property value of the component having the largest addition amount among all the components.

  The surface free energy of the charge transport layer 13 as the outermost surface is preferably 20 [mN / m] or more and 35 [mN / m] or less. If it is less than 20 [mN / m], the adhesion force of the toner or the like becomes too small, and the scattering of the component in the machine becomes obvious and defects on the image may occur frequently. On the other hand, when it is larger than 35 [mN / m], the adhesion force of the toner or the like becomes strong on the contrary, the cleaning property by the blade is deteriorated, and an image defect may be caused. More preferable surface free energy is 28 [mN / m] or more and 35 [mN / m] or less.

  Further, the control of the surface free energy of the charge transport layer 13 to the aforementioned range can be performed as follows. A relatively low surface free energy value, for example, a fluorine-based material such as polytetrafluoroethylene (PTFE), a polysiloxane-based material, or the like can be introduced into the photosensitive layer 14 and the content thereof can be adjusted. . As content, 0.01-20 weight% is preferable, More preferably, it is 0.01-5 weight%. It can also be realized by changing the kind of charge generating material, charge transporting material and binder resin contained in the photosensitive layer 14 and the composition ratio thereof. It can also be realized by adjusting the drying temperature when forming the photosensitive layer 14.

  As a result, by adjusting the appropriate surface free energy value of the outermost surface layer of the photoreceptor and the appropriate addition amount of the filler particles of the above formula, it is possible to provide an image having high wear resistance and stable over a long period of time. That is, at the initial stage of actual shooting, proper transfer efficiency of the toner can be maintained by adjusting the appropriate surface free energy, and foreign matters such as paper dust can be removed smoothly via the cleaning blade. Further, the surface free energy increases with the progress of actual shooting, but the above-described proper cleaning property and good image quality can be maintained over a long period of time. Although the detailed mechanism is not clear, it is considered that fine irregularities on the surface due to uniformly arranged filler particles maintain good cleaning properties.

  Various additives may be added to the charge transport layer 13 as necessary. For example, a plasticizer or a leveling agent may be added to the charge transport layer 13 in order to improve the film formability, flexibility, or surface smoothness. Examples of the plasticizer include biphenyl, biphenyl chloride, benzophenone, o-terphenyl, dibasic acid ester (for example, phthalic acid ester), fatty acid ester, phosphate ester, various fluorohydrocarbons, chlorinated paraffin, and epoxy type plasticizer. Etc. Examples of the surface modifier include a silicone leveling agent such as silicone oil, a fluororesin leveling agent, and the like.

  The charge transport layer 13 is formed in the same manner as in the case where the charge generation layer 12 is formed by coating, for example, in a suitable solvent, a charge transport material, a binder resin, filler particles, and, if necessary, the aforementioned additives. Is dissolved or dispersed to prepare a coating solution for a charge transport layer, and the resulting coating solution is applied onto the charge generation layer 12.

  Examples of the solvent for the coating solution for the charge transport layer include aromatic hydrocarbons such as benzene, toluene, xylene, mesitylene, tetralin, diphenylmethane, dimethoxybenzene, monochlorobenzene, dichlorobenzene, halogenated hydrocarbons such as dichloromethane and dichloroethane, Ethers such as tetrahydrofuran, dioxane, dibenzyl ether and dimethoxymethyl ether, ketones such as cyclohexanone, acetophenone and isophorone, esters such as methyl benzoate and ethyl acetate, sulfur-containing solvents such as diphenyl sulfide, hexafluoroisopropanol, etc. And aprotic polar solvents such as N, N-dimethylformamide. One of these solvents may be used alone, or two or more thereof may be mixed and used. In addition, a solvent such as alcohols, acetonitrile or methyl ethyl ketone can be further added to the above-mentioned solvent as necessary. Among these solvents, non-halogen organic solvents are preferably used in consideration of the global environment.

  Examples of the coating method for the charge transport layer coating solution include a spray method, a bar coating method, a roll coating method, a blade method, a ring method, and a dip coating method. Among these coating methods, the dip coating method is particularly excellent in various respects as described above, and is often used when the charge transport layer 13 is formed.

  The film thickness of the charge transport layer 13 is preferably 5 μm or more and 40 μm or less, and more preferably 10 μm or more and 30 μm or less. If the thickness of the charge transport layer 13 is less than 5 μm, the charge retention ability may be lowered, which is not preferable. If the thickness of the charge transport layer 13 exceeds 40 μm, it is not preferable because image degradation may occur due to a decrease in resolution.

(Photosensitive layer)
Each layer of the photosensitive layer 14 is added with one or more sensitizers such as an electron accepting substance and a dye in order to improve sensitivity and further suppress an increase in residual potential and fatigue due to repeated use. Also good.
Examples of the electron acceptor include acid anhydrides such as succinic anhydride, maleic anhydride, phthalic anhydride, and 4-chloronaphthalic anhydride, cyano compounds such as tetracyanoethylene and terephthalmalondinitrile, and 4-nitrobenzaldehyde. Aldehydes, anthraquinones, anthraquinones such as 1-nitroanthraquinone, polycyclic or heterocyclic nitro compounds such as 2,4,7-trinitrofluorenone, 2,4,5,7-tetranitrofluorenone, or diphenoquinone compounds An electron withdrawing material or the like can be used. Moreover, what polymerized these electron-withdrawing materials can also be used.

As the dye, for example, an organic photoconductive compound such as xanthene dye, thiazine dye, triphenylmethane dye, quinoline pigment or copper phthalocyanine can be used. These organic photoconductive compounds function as optical sensitizers.
Further, an antioxidant or an ultraviolet absorber may be added to each layer of the photosensitive layer 14. In particular, it is preferable to add an antioxidant or an ultraviolet absorber to the charge transport layer 13. Thereby, deterioration with respect to oxidizing gas, such as ozone and nitrogen oxides, can be reduced. Moreover, the stability of the coating liquid when forming each layer by coating can be enhanced.

  Moreover, it is preferable to contain antioxidant in the outermost surface layer containing a filler particle. The outermost surface layer containing filler particles is easily oxidized by an active gas during charging of the photoreceptor, such as ozone or NOx, and image blur is likely to occur. Therefore, the presence of an antioxidant can prevent the occurrence of image blur. As the antioxidant, a phenol compound, a hydroquinone compound, a tocopherol compound, an amine compound, or the like is used. Among these, a hindered phenol derivative or a hindered amine derivative, or a mixture thereof is preferably used. The total amount of these antioxidants used is preferably 0.1 to 50 parts by weight, more preferably 1 to 20 parts by weight per 100 parts by weight of the charge transport material. If the amount of the antioxidant used is less than 0.1 parts by weight, it may not be possible to obtain a sufficient effect for improving the stability of the coating solution and improving the durability of the photoreceptor. On the other hand, if it exceeds 50 parts by weight, the photoreceptor characteristics may be adversely affected.

(Other photoconductor configuration examples)
FIG. 4 is a partial cross-sectional view showing a simplified configuration of the electrophotographic photosensitive member 2 according to the second embodiment of the present invention. The electrophotographic photosensitive member 2 is similar to the electrophotographic photosensitive member 1, and corresponding portions are denoted by the same reference numerals and description thereof is omitted.
What should be noted in the electrophotographic photoreceptor 2 is that an intermediate layer (undercoat layer) 15 is provided between the conductive substrate 11 and the photosensitive layer 14.

  If there is no intermediate layer 15 between the conductive substrate 11 and the photosensitive layer 14, charges may be injected from the conductive substrate 11 into the photosensitive layer 14. This charge lowers the chargeability of the photosensitive layer 14, thereby reducing the surface charge other than the portion to be erased by exposure, and as a result, defects such as fogging may occur in the image. In particular, when an image is formed using a reversal development process, a toner image may be formed by attaching toner to a portion where surface charge is reduced by exposure. For this reason, when the surface charge is reduced due to factors other than exposure, fogging of an image called black spot where toner adheres to a white background and a minute black spot is formed occurs, and as a result, the image quality may be significantly deteriorated. That is, when there is no intermediate layer 15 between the conductive substrate 11 and the photosensitive layer 14, the chargeability in a minute region is reduced due to a defect in the conductive substrate 11 or the photosensitive layer 14. The image may be fogged, resulting in a significant image defect.

  In the electrophotographic photosensitive member 2, since the intermediate layer 15 is provided between the conductive substrate 11 and the photosensitive layer 14 as described above, injection of charges from the conductive substrate 11 to the photosensitive layer 14 is prevented. it can. Accordingly, it is possible to prevent the chargeability of the photosensitive layer 14 from being lowered, to suppress the reduction of surface charges other than the portion to be erased by exposure, and to prevent the occurrence of defects such as fogging on the image.

Further, by providing the intermediate layer 15, the surface of the conductive substrate 11 can be covered and a uniform surface can be obtained, so that the film formability of the photosensitive layer 14 can be improved. In addition, the peeling of the photosensitive layer 14 from the conductive substrate 11 can be suppressed, and the adhesion between the conductive substrate 11 and the photosensitive layer 14 can be improved.
For the intermediate layer 15, a resin layer or an alumite layer made of various resin materials is used.

  The resin material constituting the resin layer includes polyethylene resin, polypropylene resin, polystyrene resin, acrylic resin, vinyl chloride resin, vinyl acetate resin, polyurethane resin, epoxy resin, polyester resin, melamine resin, silicone resin, polyvinyl butyral resin, and polyamide. Examples thereof include resins such as resins, and copolymer resins containing two or more of the repeating units constituting these resins. Moreover, casein, gelatin, polyvinyl alcohol, ethyl cellulose, and the like are also included. Among these resins, it is preferable to use a polyamide resin, and it is particularly preferable to use an alcohol-soluble nylon resin. Preferred alcohol-soluble nylon resins include, for example, so-called copolymer nylon obtained by copolymerizing 6-nylon, 6,6-nylon, 6,10-nylon, 11-nylon, 2-nylon and 12-nylon, and N Examples thereof include resins obtained by chemically modifying nylon such as -alkoxymethyl-modified nylon and N-alkoxyethyl-modified nylon.

The intermediate layer 15 may contain metal oxide particles. By containing these particles in the intermediate layer 15, the volume resistance value of the intermediate layer 15 can be adjusted, so that the effect of preventing charge injection from the conductive substrate 11 to the photosensitive layer 14 can be enhanced. In addition, the electrical characteristics of the photoreceptor can be maintained under various environments. The particle diameter is preferably in the range of 0.02 to 0.5 μm.
Examples of the metal oxide particles include titanium oxide, aluminum oxide, aluminum hydroxide, and tin oxide particles.

  The intermediate layer 15 is formed by, for example, preparing the intermediate layer coating solution by dissolving or dispersing the above-described resin in a suitable solvent, and applying the coating solution to the surface of the conductive substrate 11. When the intermediate layer 15 contains the above-described metal oxide particles or the like, for example, these particles are dispersed in a resin solution obtained by dissolving the above-described resin in an appropriate solvent to form an intermediate layer coating solution. Prepare. Next, the intermediate layer 15 can be formed by applying this coating solution to the surface of the conductive substrate 11.

Water, various organic solvents, or a mixed solvent thereof is used as the solvent for the coating solution for the intermediate layer. For example, a single solvent such as water, methanol, ethanol or butanol, or water and alcohols, two or more alcohols, acetone or dioxolane and alcohols, chlorinated solvents such as dichloroethane, chloroform or trichloroethane and alcohols, etc. A mixed solvent is used. Among these solvents, non-halogen organic solvents are preferably used in consideration of the global environment.
As a method for dispersing the aforementioned particles in the resin solution, a general method using a ball mill, a sand mill, an attritor, a vibration mill, an ultrasonic disperser, a paint shaker, or the like can be used.

In the intermediate layer coating solution, the ratio C / D between the total weight C of the resin and the metal oxide and the weight D of the solvent used in the intermediate layer coating solution is 1/99 to 40/60. The ratio is preferably 2/98 to 30/70. The ratio E / F between the weight E of the resin and the weight F of the metal oxide is preferably 90/10 to 1/99, more preferably 70/30 to 5/95.

  Examples of the coating method of the intermediate layer coating liquid include a spray method, a bar coating method, a roll coating method, a blade method, a ring method, and a dip coating method. Among these, the dip coating method is relatively simple and excellent in terms of productivity and cost, as described above, and is often used when the intermediate layer 16 is formed.

  The thickness of the intermediate layer 15 is preferably 0.01 μm or more and 20 μm or less, and more preferably 0.05 μm or more and 10 μm or less. When the film thickness of the intermediate layer 15 is less than 0.01 μm, it becomes difficult to function as the intermediate layer 15 substantially, and it becomes difficult to cover the defects of the conductive substrate 11 and obtain a uniform surface property. As a result, it is difficult to prevent the injection of charges from the conductive substrate 11 to the photosensitive layer 14, and the chargeability of the photosensitive layer 14 may be deteriorated. When the intermediate layer 15 is formed by dip coating, it is difficult to form the intermediate layer 15 and the photosensitive layer 14 cannot be uniformly formed on the intermediate layer 15. This is not preferable because the sensitivity of the photoreceptor may be lowered.

(Photoconductor manufacturing method)
In the method for producing the photoreceptor, it is preferable that a drying step is included in each formation of the charge generation layer 12, the charge transport layer 13, the intermediate layer 15, and the like. The drying temperature of the photoreceptor is suitably about 50 ° C. to about 140 ° C., and particularly preferably about 80 ° C. to about 130 ° C. When the drying temperature of the photoreceptor is less than about 50 ° C., the drying time is prolonged or the solvent is not sufficiently evaporated and remains in the photosensitive layer, which is not preferable. On the other hand, if the drying temperature exceeds about 140 ° C., the electrical characteristics during repeated use deteriorate, and the image obtained using the photoreceptor may be deteriorated.

(Image forming device)
FIG. 5 is an arrangement side view showing a simplified configuration of the image forming apparatus 30 of the present invention. An image forming apparatus 30 shown in FIG. 5 is a laser printer on which the photoreceptor 1 is mounted. Hereinafter, the configuration of the laser printer 30 and the image forming operation will be described with reference to FIG. The laser printer 30 illustrated in FIG. 5 is merely an example of the image forming apparatus of the present invention, and the image forming apparatus of the present invention is not limited by the following description.

  A laser printer 30 as an image forming apparatus includes a photosensitive member 1, a semiconductor laser 31, a rotary polygon mirror 32, an imaging lens 34, a mirror 35, a corona charger 36 as a charging unit, a developing unit 37 as a developing unit, and transfer paper. It includes a cassette 38, a paper feed roller 39, a registration roller 40, a transfer charger 41 as a transfer means, a separation charger 42, a conveyor belt 43, a fixing device 44, a paper discharge tray 45, and a cleaner 46 as a cleaning means. The The semiconductor laser 31, the rotary polygon mirror 32, the imaging lens 34, and the mirror 35 constitute an exposure unit 49. A light emitting diode may be used in place of the semiconductor laser.

  The photoreceptor 1 is mounted on the laser printer 30 so as to be rotatable in the direction of an arrow 47 by a driving unit (not shown). A laser beam 33 emitted from the semiconductor laser 31 is repeatedly scanned in the longitudinal direction (main scanning direction) with respect to the surface of the photoreceptor 1 by the rotary polygon mirror 32. The imaging lens 34 has f-θ characteristics, and the laser beam 33 is reflected by the mirror 35 to form an image on the surface of the photosensitive member 1 for exposure. By scanning the laser beam 33 and forming an image while rotating the photoconductor 1 as described above, an electrostatic latent image corresponding to image information is formed on the surface of the photoconductor 1.

  The corona charger 36, the developing device 37, the transfer charger 41, the separation charger 42 and the cleaner 46 are provided in this order from the upstream side to the downstream side in the rotation direction of the photosensitive member 1 indicated by an arrow 47. The corona charger 36 is provided upstream of the image forming point of the laser beam 33 in the rotation direction of the photoconductor 1 and uniformly charges the surface of the photoconductor 1. Therefore, the surface of the photosensitive member 1 that is uniformly charged with the laser beam 33 is exposed, and a difference occurs between the charge amount of the part exposed by the laser beam 33 and the charge amount of the part that is not exposed. Electrostatic latent image is formed.

  The developing device 37 is provided on the downstream side in the rotation direction of the photosensitive member 1 with respect to the image forming point of the laser beam 33, supplies toner to the electrostatic latent image formed on the surface of the photosensitive member 1, and converts the electrostatic latent image into toner. Develop as an image. The transfer paper 48 accommodated in the transfer paper cassette 38 is taken out one by one by the paper feed roller 39 and is given to the transfer charger 41 by the registration roller 40 in synchronism with the exposure of the photoreceptor 1. The toner image is transferred onto the transfer paper 48 by the transfer charger 41. A separation charger 42 provided in the vicinity of the transfer charger 41 discharges the transfer paper onto which the toner image has been transferred and separates it from the photoreceptor 1.

The transfer paper 48 separated from the photoreceptor 1 is conveyed to the fixing device 44 by the conveying belt 43, and the toner image is fixed by the fixing device 44. The transfer paper 48 on which the image is formed in this manner is discharged toward the paper discharge tray 45. In addition, after the transfer paper 48 is separated by the separation charger 42, the photoreceptor 1 that continues to rotate further cleans foreign matters such as toner and paper dust remaining on the surface by the cleaner 46. The photoreceptor 1 whose surface has been cleaned by the cleaner 46 is neutralized by a neutralizing lamp (not shown) provided together with the cleaner 46 and then further rotated, and a series of image forming operations starting from the charging of the photoreceptor 1 are repeated. .
In addition, it is possible to employ a configuration in which a plurality of photosensitive members are provided to form a superimposed image using a plurality of different toners. This configuration is called a tandem system.

EXAMPLES Hereinafter, although this invention is demonstrated still in detail using an Example, this invention is not limited to the following description content.
First, a photoconductor prepared by forming a photoconductive layer under various conditions on an aluminum cylindrical support having a diameter of 30 mm and a length of 340 mm will be described.

Example 1
Titanium oxide TTO-MI-1 (manufactured by Ishihara Sangyo) 3 g, CM-8000 (manufactured by Toray Industries, Inc.): 3 g of alcohol-soluble nylon resin, 60 g of methanol, and 40 g of 1,3-dioxolane are dispersed in a paint shaker for 10 hours. Thus, an undercoat layer coating solution was prepared. An undercoat layer was formed by forming the prepared undercoat layer coating solution on an aluminum cylindrical support having a diameter of 30 mm and a length of 340 mm by a dip coating method so as to have a film thickness of 0.9 μm. .

  Next, 10 g of butyral resin (ESREC BM-2: Trademark of Sekisui Chemical Co., Ltd.), 1400 g of 1,3-dioxolane, and titanyl phthalocyanine represented by the structural formula (A-1) (for example, known in Patent Registration No. 3569422) The charge generation layer coating solution was prepared by dispersing 15 g with a ball mill for 72 hours. The charge generation layer was formed by depositing the coating solution on the aluminum cylindrical support provided with the undercoat layer so as to have a film thickness of 0.2 μm by a dip coating method.

Next, 0.9 g of two types of polycarbonate resins, GH503 (manufactured by Idemitsu Kosan) and TS2040 (manufactured by Teijin Chemicals) and 1.8 g of silica (TS-610: manufactured by Cabot Specialty Chemicals) were added to 32.4 g of tetrahydrofuran. Mixed. The obtained mixture was subjected to a dispersion treatment with a ball mill for 5 hours using ZrO ₂ beads (φ3 mm) as a medium to prepare a primary dispersion coating solution for a charge transport layer. At this stage, the filler particles are uniformly dispersed and the dispersion state corresponding to the primary particle size (about 17 nm) is maintained. Light scattering particle size distribution analyzer: Microtrac UPA-150 (manufactured by Nikkiso) ) To confirm. Next, 100 g of a butadiene compound represented by the following structural formula (I) (T-405, manufactured by Takasago Inc.) as a charge transport material, 69.1 g of two types of polycarbonate resins GH503 and TS2040, respectively, an antioxidant (Sumilyzer BHT) : Manufactured by Sumitomo Chemical Co.) was dissolved in 984 g of tetrahydrofuran. To this solution, 3.6 g of the primary dispersion coating liquid for charge transport layer was mixed and stirred for 15 hours to prepare a secondary dispersion coating liquid for charge transport layer. This coating solution was applied onto the above-described charge generation layer by a dip coating method, and dried at 130 ° C. for 1 hour to form a charge transport layer having a layer thickness of 28 μm, whereby the photoreceptor of Example 1 was produced. .

(Example 2)
After forming the charge generation layer in the same manner as in Example 1, 1.8 g of the polycarbonate resin (G400) and 1.8 g of silica (TS-610) were mixed in 32.4 g of THF and dispersed in a ball mill for 5 hours. Thus, a primary dispersion coating solution for the charge transport layer was prepared. Next, 100 g of a butadiene compound (T-405) represented by the above structural formula (I), 138.3 g of the polycarbonate resin (G400), and 5 g of an antioxidant (Sumilyzer BHT) are mixed with 984 g of tetrahydrofuran as a charge transport material. And dissolved. A photoconductor was prepared in the same manner as in Example 1 except that the obtained solution was used for the secondary dispersion coating solution for the charge transport layer.

(Example 3)
After forming the charge generation layer in the same manner as in Example 1, the primary dispersion coating liquid for charge transport layer was prepared in the same manner as in Example 2. Next, 100 g of the butadiene compound (T-405) represented by the structural formula (I) as a charge transport material, 13.8 g of the polycarbonate resin (GH503) and 124.4 g (M300: manufactured by Idemitsu Kosan Co., Ltd.), an antioxidant (Sumilyzer BHT) 5 g was mixed with 984 g of tetrahydrofuran and dissolved. A photoconductor was prepared in the same manner as in Example 1 except that the obtained solution was used for the secondary dispersion coating solution for the charge transport layer.

Example 4
After forming the charge generation layer in the same manner as in Example 1, 0.62 g of two types of polycarbonate resins (GH503) and (TS2040) and 1.25 g of silica (TS-610) were mixed with 22.5 g of tetrahydrofuran. The primary dispersion coating solution for the charge transport layer was prepared by carrying out a dispersion treatment with a ball mill for 5 hours. Next, 100 g of the butadiene compound (T-405) represented by the above structural formula (I) as a charge transport material, 69.9 g of the polycarbonate resins GH503 and TS2040, respectively, and 5 g of an antioxidant (Sumilyzer BHT) to 984 g of tetrahydrofuran. Mix and dissolve. A photoconductor was prepared in the same manner as in Example 1 except that the obtained solution was used for the secondary dispersion coating solution for the charge transport layer.

(Example 5)
After forming the charge generation layer in the same manner as in Example 1, 1.55 g of two kinds of polycarbonate resins (GH503) and (TS2040) and 3.1 g of silica (TS-610) were mixed with 55.9 g of tetrahydrofuran. The primary dispersion coating solution for the charge transport layer was prepared by dispersing for 5 hours in a ball mill. Next, 100 g of the butadiene compound (T-405) represented by the structural formula (I) as a charge transport material, 68.5 g of the polycarbonate resins GH503 and TS2040 and 5 g of the antioxidant (Sumilyzer BHT) in 992 g of tetrahydrofuran. Mix and dissolve. A photoconductor was prepared in the same manner as in Example 1 except that the obtained solution was used for the secondary dispersion coating solution for the charge transport layer.

(Example 6)
After the charge generation layer was formed in the same manner as in Example 1, a primary dispersion coating solution for charge transport layer was prepared in the same manner as in Example 5. Next, 100 g of the butadiene compound (T-405) represented by the structural formula (I), 137 g of the polycarbonate resin (G400), and 5 g of the antioxidant (Sumilyzer BHT) are mixed with 984 g of tetrahydrofuran as a charge transport material and dissolved. did. A photoconductor was prepared in the same manner as in Example 5 except that the obtained solution was used for the secondary dispersion coating solution for the charge transport layer.

(Example 7)
After the charge generation layer was formed in the same manner as in Example 1, a primary dispersion coating solution for charge transport layer was prepared in the same manner as in Example 5. Next, 100 g of the butadiene-based compound (T-405) represented by the structural formula (I) as a charge transport material, 13.7 g of the polycarbonate resin (GH503) and 123.3 g of (M300), an antioxidant (Sumilyzer BHT) 5 g was mixed with 984 g of tetrahydrofuran and dissolved. A photoconductor was prepared in the same manner as in Example 5 except that the obtained solution was used for the secondary dispersion coating solution for the charge transport layer.

(Example 8)
After the charge generation layer was formed in the same manner as in Example 1, a primary dispersion coating solution for charge transport layer was prepared in the same manner as in Example 5. Next, 100 g of a butadiene compound (T-405) represented by the above structural formula (I), 123.3 g of the polycarbonate resin (GH503) and polytetrafluoroethylene (PTFE: Lubron L-2: Daikin Industries) as a charge transport material 13.7 g) and 5 g of an antioxidant (Sumilyzer BHT) were mixed and dissolved in 984 g of tetrahydrofuran. A photoconductor was prepared in the same manner as in Example 5 except that the obtained solution was used for the secondary dispersion coating solution for the charge transport layer.

Example 9
After the charge generation layer was formed in the same manner as in Example 1, a primary dispersion coating solution for charge transport layer was prepared in the same manner as in Example 5. Next, 100 g of a butadiene compound (T-405) represented by the above structural formula (I) as a charge transport material, 130.2 g of the polycarbonate resin (GH503), and polytetrafluoroethylene (PTFE: Lubron L-2) 6. 8 g and 5 g of antioxidant (Sumilyzer BHT) were mixed with 984 g of tetrahydrofuran and dissolved. A photoconductor was prepared in the same manner as in Example 1 except that the obtained solution was used for the secondary dispersion coating solution for the charge transport layer.

(Example 10)
After the charge generation layer was formed in the same manner as in Example 1, a primary dispersion coating solution for charge transport layer was prepared in the same manner as in Example 5. Next, 100 g of the butadiene compound (T-405) represented by the structural formula (I) as a charge transport material, 133.6 g of the polycarbonate resin (GH503), and polytetrafluoroethylene (PTFE: Lubron L-2) 3. 4 g and 5 g of an antioxidant (Sumilyzer BHT) were mixed and dissolved in 984 g of tetrahydrofuran. A photoconductor was prepared in the same manner as in Example 5 except that the obtained solution was used for the secondary dispersion coating solution for the charge transport layer.

Example 11
After the charge generation layer was formed in the same manner as in Example 1, a primary dispersion coating solution for charge transport layer was prepared in the same manner as in Example 5. Next, 100 g of a butadiene compound (T-405) represented by the above structural formula (I), 137.0 g of the polycarbonate resin (GH503), and 5 g of an antioxidant (Sumilyzer BHT) are mixed in 984 g of tetrahydrofuran as a charge transport material. And dissolved. A photoconductor was prepared in the same manner as in Example 1 except that the obtained solution was used for the secondary dispersion coating solution for the charge transport layer.

(Example 12)
After the charge generation layer was formed in the same manner as in Example 1, a primary dispersion coating solution for charge transport layer was prepared in the same manner as in Example 5. Next, 100 g of the butadiene compound (T-405) represented by the above structural formula (I) as a charge transport material, 27.4 g and 109.6 g of the polycarbonate resins (GH503) and (TS2040), respectively, an antioxidant ( 5 g (Smilizer BHT) was mixed and dissolved in 984 g of tetrahydrofuran. A photoconductor was prepared in the same manner as in Example 5 except that the obtained solution was used for the secondary dispersion coating solution for the charge transport layer.

(Example 13)
After the charge generation layer was formed in the same manner as in Example 1, a primary dispersion coating solution for charge transport layer was prepared in the same manner as in Example 5. Next, 100 g of the butadiene compound (T-405) represented by the structural formula (I) as a charge transport material, 6.9 g and 130.2 g of the polycarbonate resins (GH503) and (TS2040), respectively, an antioxidant ( 5 g (Smilizer BHT) was mixed and dissolved in 984 g of tetrahydrofuran. A photoconductor was prepared in the same manner as in Example 5 except that the obtained solution was used for the secondary dispersion coating solution for the charge transport layer.

(Example 14)
After the formation of the charge generation layer in the same manner as in Example 1, 2.33 g of the polycarbonate resin: GH503 and TS2040 and 4.65 g of silica (TS-610) were used as the charge transport layer coating solution, respectively, and 83.7 g of tetrahydrofuran. And a dispersion treatment for 5 hours with a ball mill to prepare a primary dispersion coating solution for a charge transport layer. Next, 100 g of the butadiene compound (T-405) represented by the structural formula (I) as a charge transport material, 67.7 g of the polycarbonate resins: GH503 and TS2040, respectively, and 998 g of an antioxidant (Sumilyzer BHT) 599 g. And dissolved. A photoconductor was prepared in the same manner as in Example 5 except that the obtained solution was used for the secondary dispersion coating solution for the charge transport layer.

(Example 15)
After the charge generation layer was formed in the same manner as in Example 1, the primary dispersion coating solution for charge transport layer was prepared in the same manner as in Example 14. Next, 100 g of the butadiene compound (T-405) represented by the structural formula (I), 135.4 g of the polycarbonate resin (G400), and 5 g of the antioxidant (Sumilyzer BHT) are mixed in 998 g of tetrahydrofuran as a charge transport material. And dissolved. A photoconductor was prepared in the same manner as in Example 14 except that the obtained solution was used for the secondary dispersion coating solution for the charge transport layer.

(Example 16)
After the charge generation layer was formed in the same manner as in Example 1, the primary dispersion coating solution for charge transport layer was prepared in the same manner as in Example 14. Next, 100 g of the butadiene-based compound (T-405) represented by the structural formula (I) as a charge transport material, 13.5 g and 121.9 g of the polycarbonate resin; GH503 and M300, respectively, an antioxidant (Sumilyzer BHT) ) 5 g was dissolved in 998 g of tetrahydrofuran. A photoconductor was prepared in the same manner as in Example 14 except that the obtained solution was used for the secondary dispersion coating solution for the charge transport layer.

(Example 17)
A photoconductor was prepared in the same manner as in Example 5 except that the filler particles were changed to alumina (Sumicorundum AA-04: manufactured by Sumitomo Chemical Co., Ltd.).

(Example 18)
A photoconductor was prepared in the same manner as in Example 5 except that the filler particles were changed to silica (X-24-9163A: manufactured by Shin-Etsu Chemical Co., Ltd.).

(Example 19)
A photoconductor was prepared in the same manner as in Example 5 except that the filler particles were changed to silica (SO-E5: manufactured by Admatex).

(Example 20)
Other than changing the charge transport material to 90 g of a triarylamine compound (manufactured by Nippon Distilled Industries Co., Ltd.) represented by the following structural formula (II) and 10 g of a butadiene compound (manufactured by Takasago Fragrance Co., Ltd.) represented by the following structural formula (III). Were prepared in the same manner as in Example 5.

(Example 21)
A photoconductor was prepared in the same manner as in Example 5 except that the charge transport material was changed to 100 g of the triarylamine compound represented by the above structural formula (II) (manufactured by Nippon Distilled Industries).

(Example 22)
A photoconductor was produced in the same manner as in Example 5 except that the charge transport material was changed to 100 g of a styryl compound (Hodogaya Chemical Co., Ltd.) represented by the following structural formula (IV).

(Example 23)
A photoconductor was produced in the same manner as in Example 5 except that the antioxidant (Smizer BHT) was not added to the primary dispersion coating solution for the charge transport layer.

(Comparative Example 1)
Charge by adding 3.1 g of polycarbonate resin (GH503) and 1.55 g of (TS2040) and 3.1 g of silica (TS-610) to 55.8 g of tetrahydrofuran, and dispersing the mixture for 5 hours using a paint shaker. A primary dispersion coating solution for the transport layer was prepared. Thereafter, when the particle size distribution of silica in the coating solution was measured, it was confirmed that a coarse aggregate significantly larger than the primary particle diameter was clearly formed. A photoconductor was prepared in the same manner as in Example 5 except that this primary dispersion coating solution was used.

(Comparative Example 2)
1.2 g of polycarbonate resin (TS2040) and 1.2 g of silica (TS-610) were mixed with 21.6 g of tetrahydrofuran, and dispersed in a ball mill for 5 hours to prepare a primary dispersion coating solution for a charge transport layer. Next, 100 g of the butadiene compound (T-405) represented by the above structural formula (I) as the charge transport material, 69.9 g of each of the polycarbonate resins: GH503 and TS2040, and 5 g of the antioxidant (Sumilyzer BHT) are added to tetrahydrofuran. The mixture was dissolved in 980 g. A photoreceptor was prepared in the same manner as in Example 5 except that 2.4 g of the primary dispersion coating liquid was added to the obtained secondary dispersion coating liquid for charge transport layer and the mixture was further stirred for 15 hours.

(Comparative Example 3)
After preparing the primary dispersion coating solution for charge transport layer in the same manner as in Comparative Example 2, 100 g of the butadiene compound (T-405) represented by the above structural formula (I) as the charge transport material, the polycarbonate resin (J500: Idemitsu) (Product of Kosan) and (G400) were dissolved by mixing 69.5 g of each and 5 g of an antioxidant (Sumilyzer BHT) in 980 g of tetrahydrofuran. A photoconductor was prepared in the same manner as in Comparative Example 2 except that the obtained solution was used as the secondary dispersion coating solution for the charge transport layer.

(Comparative Example 4)
After preparing a primary dispersion coating solution for charge transport layer in the same manner as in Comparative Example 2, the enamine compound represented by the following structural formula (V) was prepared as a charge transport material by the method described in JP-A No. 2004-151666. ) 100 g, 13.9 and 125.1 g of the polycarbonate resins GH503 and M300, respectively, and 2.5 g of an antioxidant (Irganox 1010: manufactured by Ciba Specialty Chemicals) were mixed and dissolved in 980 g of tetrahydrofuran. A photoconductor was prepared in the same manner as in Comparative Example 2 except that the obtained solution was used as the secondary dispersion coating solution for the charge transport layer.

(Comparative Example 5)
After coating up to the charge generation layer in the same manner as in Example 1, a primary dispersion coating solution for charge transport layer was prepared in the same manner as in Example 5. Next, 100 g of the butadiene compound (T-405) represented by the structural formula (I) as a charge transport material, 68.5 g of the polycarbonate resins J500 and G400, respectively, and 5 g of the antioxidant (Sumilyzer BHT) are mixed with 984 g of tetrahydrofuran. And dissolved. A photoconductor was prepared in the same manner as in Example 5 except that the obtained solution was used for the secondary dispersion coating solution for the charge transport layer.

(Comparative Example 6)
After coating up to the charge generation layer in the same manner as in Example 1, a primary dispersion coating solution for charge transport layer was prepared in the same manner as in Example 5. Next, 100 g of an enamine compound represented by the structural formula (V) (prepared by the method described in JP-A No. 2004-151666) as a charge transport material, and 13.7 g and 123.3 g of the polycarbonate resins GH503 and M300, respectively. Then, 5 g of an antioxidant (Irganox 1010) was mixed and dissolved in 984 g of tetrahydrofuran. A photoconductor was prepared in the same manner as in Example 5 except that the obtained solution was used for the secondary dispersion coating solution for the charge transport layer.

(Comparative Example 7)
After forming the charge generation layer in the same manner as in Example 1, 2.5 g of two types of polycarbonate resins (GH503) and (TS2040) and 5.0 g of silica (TS-610) were used as the charge transport layer coating solution. The mixture was mixed with 90 g of tetrahydrofuran and dispersed in a ball mill for 5 hours to prepare a primary dispersion coating solution for charge transport layer. Next, 100 g of the butadiene compound (T-405) represented by the above structural formula (I) as the charge transport material, 67.5 g of the polycarbonate resins GH503 and TS2040, and 5 g of the antioxidant (Sumilyzer BHT) 1005. 6 g was mixed and dissolved. A photoconductor was prepared in the same manner as in Example 5 except that the obtained solution was used for the secondary dispersion coating solution for the charge transport layer.

(Comparative Example 8)
After application to the charge generation layer in the same manner as in Example 1, a primary dispersion coating solution for charge transport layer was prepared in the same manner as in Comparative Example 7. Subsequently, 100 g of the butadiene compound (T-405) represented by the structural formula (I) as a charge transport material, 67.5 g of each of the polycarbonate resins J500 and G400, and 5 g of an antioxidant (Sumilyzer BHT) 1005. 6 g was mixed and dissolved. A photoconductor was prepared in the same manner as in Comparative Example 7 except that the obtained solution was used as the secondary dispersion coating solution for the charge transport layer.

(Comparative Example 9)
After application to the charge generation layer in the same manner as in Example 1, a primary dispersion coating solution for charge transport layer was prepared in the same manner as in Comparative Example 7. Next, 100 g of an enamine compound represented by the structural formula (V) (produced by the method described in JP-A No. 2004-151666) as a charge transport material, and 13.5 g and 121.5 g of the polycarbonate resins GH503 and M300, respectively. Then, 5 g of an antioxidant (Irganox 1010) was mixed with 1005.6 g of tetrahydrofuran and dissolved. A photoconductor was prepared in the same manner as in Comparative Example 7 except that the obtained solution was used as the secondary dispersion coating solution for the charge transport layer.

(Comparative Example 10)
After preparing the primary dispersion coating solution for the charge transport layer in the same manner as in Example 5, 100 g of the butadiene compound (T-405, Takasago Inc.) represented by the above structural formula (I) as the charge transport material, the polycarbonate resin 63 g each of GH503 and TS2040 and 5 g of an antioxidant (Sumilyzer BHT) were mixed and dissolved in 980 g of tetrahydrofuran. A photoreceptor having no filler particles in the outermost surface layer was produced in the same manner as in Example 5 except that the obtained solution was used for the secondary dispersion coating solution for the charge transport layer.

Tables 1 and 2 show the characteristics of the filler particles and the charge transport materials used for Examples 1 to 23 and Comparative Examples 1 to 10. In addition, the measuring method of a, b, df, and dm of filler particles is described below.
[Measuring method of a, b, df and dm]
Since a uniform dispersion state could be confirmed in this example, a was obtained as a calculated value from the amount of filler particles added and the volume of the coating film as a medium.
Since b is a commercially available filler particle, it quoted from the catalog value.
Since df is a commercially available filler particle, the catalog value was quoted.
The dm was obtained by measuring and measuring the volume and weight of the coating film.

Tables 3 and 4 show the filler particle dispersion state, plastic hardness, elastic power, and surface free energy measured by the following methods.
[Dispersed state of filler particles]
About the superiority or inferiority of the dispersed state of the filler particles, the particle size distribution was measured with a particle size distribution measuring device (UPA-150 (manufactured by Nikkiso)). The state in which the filler particles are stably dispersed to a state close to the primary particle diameter (when the distribution is shown) is indicated by ◯, and the state where the micron-order aggregate is formed (when the distribution is indicated) is × It was.
[Plastic hardness value and elastic power measurement (surface film physical property test)]
The elastic power and the plastic hardness value were measured with a Fischer scope H100V (manufactured by Fischer Instruments) in an environment of a temperature of 25 ° C. and a relative humidity of 50%. The measurement conditions were the maximum indentation load W = 5 mN, the required load time to the indentation maximum load 5 seconds, the load holding time t = 5 seconds, and the unloading time 5 seconds.

[Surface free energy (γ) measurement]
The surface free energy (γ) of the outermost surface layer of each of the photoreceptors in the above examples and comparative examples was determined by a contact angle measuring device CA-X (manufactured by Kyowa Interface) and analysis software EG-11 (manufactured by Kyowa Interface). .

Further, each of the photoconductors of Examples 1 to 23 and Comparative Examples 1 to 10 is mounted on a digital copying machine AR-450 (manufactured by Sharp) modified for testing so that the developing device and the surface potential measuring device can be replaced. By forming 100,000 sheets of the character test chart defined in the above, the sensitivity, printing durability and image were evaluated by the following methods.
[Sensitivity (electric property) evaluation]
The developer was removed from the test copying machine, and a surface potential meter (manufactured by Trek Japan: model 344) was attached to the development site instead. Using this copying machine, the surface potential of the photoconductor when it was not exposed to laser light in a normal temperature / normal humidity (N / N) environment at a temperature of 25 ° C. and a relative humidity of 50% was measured. In this state, it was adjusted to −650 V, and exposed to laser light (0.4 μJ / cm ² ), and the initial surface potential of the photoconductor was measured as the exposure potential VL (V). The smaller the absolute value of the exposure potential VL, the higher the sensitivity.
<Criteria>
○: | VL | <90 (V)
Δ: 90 (V) ≦ | VL | <130 (V)
×: 130 (V) ≦ | VL |

[Evaluation of printing durability]
The cleaning blade of the cleaning device provided in the modified AR-450 machine has a pressure at which it contacts the photoreceptor, so-called cleaning blade pressure, is 21 gf / cm (2.06 × 10 ⁻¹ N / cm: initial linear pressure) as an initial linear pressure. It was adjusted. In the N / N environment, the above-mentioned character test chart was formed on 100,000 sheets of recording paper for each photoconductor, and a printing durability test was performed.
The thickness of the photosensitive layer at the start of the printing durability test and after the 100,000 sheets of images were formed was measured using a film thickness measuring device (trade name: F-20-EXR, manufactured by Filmetrics). From the difference between the film thickness at the start of the printing durability test and the film thickness after 100,000 sheets of images were formed, the amount of abrasion per 100,000 revolutions of the photosensitive drum was determined. The printing durability was evaluated from the obtained amount of scraping according to the following criteria. It was evaluated that the greater the amount of shaving, the worse the printing durability.
<Criteria>
◯: scraping amount d <0.8 μm / 100 k rotation Δ: 0.8 μm / 100 k rotation ≦ scraping amount d <1.0 μm / 100 k rotation ×: 1.0 μm / 100 k rotation ≦ scraping amount d

[Image evaluation]
1. Scratch resistance determination In order to investigate the level of deterioration in image quality after the printing test, white streaks due to scratches on the surface of the photoreceptor in a halftone image in which the pulse width of the semiconductor laser is modulated to 80 gradations corresponding to 255 gradations ( The presence or absence of sharp contrast along the drum circumferential direction was observed. The criteria for determining image degradation are as follows.
○: There is no white stripe in the halftone image visually. Good picture.
Δ: Visually confirmed white streaks in the halftone image. There is no problem in actual use.
X: A white streak clearly appears in the halftone image by visual inspection. A level that causes problems in actual use.
2. Judgment of gas resistance In order to investigate the deterioration level of image quality after the printing test, the presence or absence of density unevenness in the halftone image (mainly periodic unevenness that occurs corresponding to the length of the drum circumference along the drum axis direction) Was observed. The criteria for determining density unevenness are as follows.
○: There is no density unevenness in the halftone image visually. Good picture.
Δ: Density unevenness in the halftone image visually. There is no problem in actual use.
X: Density unevenness in the halftone image visually. A level that causes problems in actual use.

[Cleanability evaluation]
The above-mentioned character test chart and recording paper are used in common, and the formed image is visually observed at the initial stage of image formation (≈0k) and 100,000 (100k) sheets. The presence or absence of black streaks due to toner leakage in the photoconductor rotation direction was tested. Further, the fogging amount Wk was obtained by a measuring device to be described later, and the cleaning property was evaluated. The fogging amount Wk of the formed image was obtained by measuring the reflection density using a Z-Σ90 COLOR MEASURING SYSTEM manufactured by Nippon Denshoku Industries Co., Ltd. Specifically, first, the reflection average density Wr of the recording paper before image formation was measured. Next, an image was formed on the recording paper, and after the image formation, the reflection density of each portion of the white background portion of the recording paper was measured. The reflection density Ws of the portion judged to be the most fogged, that is, the portion with the highest density while being a white background portion, was measured. Wk obtained from Wr and Ws by the formula {100 × (Wr−Ws) / Wr} was defined as the fogging amount. The cleaning properties were evaluated from the obtained Wk according to the following criteria.
○: Good. There is no black streak with good clarity. Fog amount Wk is less than 5%.
Δ: No practical problem. The level of sharpness is practically acceptable and the length of black streaks is 2.0 mm or less and 5 or less. Fog amount Wk is 5% or more and less than 10%.
X: Not practical. There is a problem in practical use of sharpness. Exceeding the above Δ range of black lines. Fog amount Wk is 10% or more.

[Comprehensive evaluation]
Based on the determination results of the above five items, the determination is made as follows.
◎: All 5 items ○
○: ○ or △ for all 5 items
×: At least one or more ×
The evaluation results are shown in Tables 5 and 6.

The photoconductors of Examples 1 to 23 using filler particles satisfying 1.0 × 10 ⁻³ ≦ (df × b ³ ) / (dm × a ³ ) ≦ 2.5 × 10 ⁻² were average scraped during 100,000 actual shots. The amount was 0.8 μm or less, and good printing durability was exhibited. Further, it was confirmed that the electrical stability is excellent and the image / cleanability is at a level that does not cause a problem in practical use.

Further, from comparison between Examples 5, 18, and 19, it was found that the electric characteristics using the filler particles having a small particle diameter are more stabilized. Furthermore, from the comparison of the exposure potentials of Examples 5, 18, 19 and Example 17, it was confirmed that silica is slightly superior in electrical stability to alumina. Further, the photoreceptors of Examples 5 and 20 containing specific nitrogen compounds, that is, CTMs of Structural Formula (I) and Structural Formula (III), and Examples 21 containing CTMs other than those described above. Compared with 22, 22, the image density is not uneven even after 100,000 actual shots, and a more stable image is provided. This is presumed that these CTMs are resistant to gases such as O ₃ or NOx generated near the charger during actual shooting. Moreover, it became clear from the comparison of Example 5 and Example 23 that the tolerance with respect to the said gas has improved by introduction | transduction of antioxidant.

Furthermore, it was confirmed by comparison between Example 5 and Examples 8 to 13 that the surface free energy is in the range of 20 to 35 mN / m, so that the cleaning property becomes better.
In Comparative Examples 3 to 6 and 8 to 9, the mechanical characteristic values on the surface of the photoreceptor are not in the specified range, and as a result, adverse effects occur. That is, in Comparative Examples 3, 5, and 8, since the plastic hardness is smaller than the specified value, the plasticity of the outermost surface layer is extremely small. As a result, cleaning failure occurred. On the other hand, in Comparative Examples 4, 6, and 9 in which the plastic hardness is larger than the specified value, the brittleness of the outermost surface layer was conspicuous and scratches were generated on the surface of the photoreceptor.
In Comparative Examples 1 to 4 and 7 to 10 using filler particles outside the range of 1.0 × 10 ⁻³ ≦ (df × b ³ ) / (dm × a ³ ) ≦ 2.5 × 10 ⁻² , all are sensitivity / stable. It was found that the property or the amount of film slip did not reach the desired value.

1 is a schematic partial cross-sectional view of an electrophotographic photosensitive member of the present invention. It is a graph which shows the difference of the aggregated particle diameter by the dispersion conditions of a filler particle. It is a graph which shows the outline | summary of a surface film physical property test. 1 is a schematic partial cross-sectional view of an electrophotographic photosensitive member of the present invention. 1 is a schematic side view of an image forming apparatus of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 Electrophotographic photoreceptor 8 Hysteresis line 11 Conductive substrate 12 Charge generation layer 13 Charge transport layer 14 Photosensitive layer 15 Intermediate layer 30 Laser printer (image forming apparatus)
DESCRIPTION OF SYMBOLS 31 Semiconductor laser 32 Rotating polygon mirror 34 Imaging lens 35 Mirror 36 Corona charger 37 Developing device 38 Transfer paper cassette 39 Paper feed roller 40 Registration roller 41 Transfer charger 42 Separation charger 43 Conveyor belt 44 Fixing device 45 Paper discharge tray 46 Cleaner 47 Arrow 48 Transfer paper 49 Exposure means

Claims (8)

An electrophotographic photoreceptor having at least a charge generation layer and a charge transport layer in this order on a conductive substrate,
The outermost surface layer of the electrophotographic photoreceptor contains filler particles,
The filler particles in the primary dispersion coating solution for the charge transport layer for forming the outermost surface layer are measured by a light scattering particle size distribution measuring device, and the dispersion state corresponding to the primary particle diameter is maintained.
Filler particles in the outermost surface layer are represented by the following formula (1).
1.0 × 10 ⁻³ ≦ (df × b ³ ) / (dm × a ³ ) ≦ 2.5 × 10 ^-2 (1)
(In the formula, a means the average distance between filler particles (nm), b means the average filler particle diameter (nm), df means the density of filler particles (g / cm ³ ), and dm is the maximum. plus average density of the solid surface layer fraction (g / cm ^{3) of} means) fully,
The outermost surface layer, the surface film hardness test (test conditions: 25 ℃ / 50% RH, the maximum load: 5 mN) when subjected ^{to, 200N / mm 2 ~350N / mm} 2 plastic hardness value (Hpl), An electrophotographic photosensitive member having an elastic power of 40% to 60%.   The electrophotographic photosensitive member according to claim 1, wherein the filler particles are made of silicon oxide.   The electrophotographic photosensitive member according to claim 1, wherein the filler particles have a particle size of 100 nm or less. The charge transport layer has the following structural formulas (I) to (IV):

The electrophotographic photosensitive member according to claim 1, further comprising any one or more of amine-based compounds represented by the formula:   The electrophotographic photosensitive member according to any one of claims 1 to 4, further comprising an antioxidant.   The electrophotographic photoreceptor according to claim 1, wherein the outermost surface layer has a surface free energy (γ) of 20 (mN / m) to 35 (mN / m).   The electrophotographic photosensitive member according to claim 6, wherein the outermost surface layer has a surface free energy (γ) of 28 (mN / m) to 35 (mN / m).   An image forming apparatus comprising: a photoconductor, a charging unit, an exposure unit, a developing unit, and a transfer unit, wherein the photoconductor includes the electrophotographic photoconductor according to claim 1.

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