Photosensitive body for electronic photography, method for producing the same, and electronic photography device equipped with the same

Abstract

The present invention provides an electrophotographic photoreceptor capable of reducing the wear of a photosensitive layer, suppressing the generation of ghost images, and stably obtaining good images. A photoreceptor for electronic photography, comprising a photosensitive layer comprising a charge generating material, a hole transporting material, a first and a second electron transporting material, a resin binder, and an inorganic oxide filler surface-treated with a silane coupling agent on a conductive substrate, wherein the difference ΔSPa between the dipole force term of the Hansen solubility parameters of the first electron transporting material and the silane coupling agent satisfies ΔSPa<2.50, the difference ΔSPb between the dipole force term of the Hansen solubility parameters of the second electron transporting material and the silane coupling agent satisfies ΔSPb<2.50, the difference ΔSPc between the dipole force term of the Hansen solubility parameters of the first and the second electron transporting materials satisfies 0.30<ΔSPc<1.00, the difference ΔSPd between the London dispersion force term of the Hansen solubility parameters of the resin binder and the silane coupling agent satisfies ΔSPd<2.00, and the content ratio of the second electron transporting material to the first and the second electron transporting materials is 3 to 40% by mass.

Description

Technical Field

[0001] The present invention relates to an electrophotographic photoreceptor (hereinafter also simply referred to as "photoreceptor") used in an electrophotographic printer, a copier, a facsimile machine, etc., a method for producing the same, and an electrophotographic device equipped with the same. Background Art

[0002] Electrophotographic photoreceptors have a basic structure in which a photosensitive layer having a photoconductive function is provided on a conductive substrate. In recent years, organic electrophotographic photoreceptors using organic compounds as functional components responsible for generating and transporting electric charges have been actively researched and developed due to their advantages such as material diversity, high productivity, and safety, and have begun to be applied to copiers, printers, etc.

[0003] Generally, a photoreceptor needs to have the function of maintaining surface charges in the dark, the function of receiving light and generating charges, and the function of transporting the generated charges. As a photoreceptor, there are so-called single-layer photoreceptors having a single-layer photosensitive layer having these functions, and so-called laminated (functionally separated) photoreceptors having a photosensitive layer obtained by laminating layers with functions separated into a charge generating layer and a charge transporting layer, wherein the charge generating layer is mainly responsible for generating charges when receiving light, and the charge transporting layer is responsible for maintaining surface charges in the dark and transporting charges generated on the charge generating layer when receiving light.

[0004] The photosensitive layer is usually formed by coating a coating solution obtained by dissolving or dispersing a charge generating material, a charge transporting material, and a resin binder in an organic solvent on a conductive substrate. In particular, for the layer constituting the outermost surface of the organic photoreceptor, polycarbonate having high resistance to friction with paper and a scraper for removing toner, excellent sliding properties, and good light permeability is often used as a resin binder. Among them, bisphenol Z polycarbonate is widely used as a resin binder.

[0005] On the other hand, in recent years, so-called digital machines have become mainstream electronic photographic devices that use monochromatic light such as argon, helium-neon, semiconductor lasers or light-emitting diodes as exposure light sources, digitize information such as images and text, convert them into light signals, irradiate the charged photoreceptor with light, form an electrostatic latent image on the surface of the photoreceptor, and then visualize it with toner.

[0006] As a method for charging a photoreceptor, there are non-contact charging methods in which a charging member such as a corona discharger is not in contact with the photoreceptor, and contact charging methods in which a charging member such as a semi-conductive rubber roller or a brush is in contact with the photoreceptor. Among them, compared with the non-contact charging method, the contact charging method has the advantages of less ozone generation and lower applied voltage due to the occurrence of corona discharge near the photoreceptor. Therefore, a more compact, low-cost, and low-environmental-pollution electronic photographic device can be realized, and it has become the mainstream in medium-sized to small devices.

[0007] As a method for cleaning the surface of the photoreceptor, methods such as scraping with a scraper or cleaning treatment while developing are mainly used. In the cleaning treatment using a scraper, the untransferred residual toner on the surface of the photoreceptor is sometimes scraped off by the scraper and recovered in a recovery box for waste toner or returned to the developer. Therefore, when using such a cleaner using a scraper, it is necessary to set up a recovery box for toner or a space for circulation, and it is necessary to monitor whether the recovery box is full. In addition, if paper scraps or external materials are retained on the scraper, sometimes damage is caused on the surface of the photoreceptor, shortening the life of the photoreceptor. Therefore, sometimes a treatment is set up to recover the toner through a development process, and the residual toner attached to the surface of the photoreceptor is subjected to magnetic or electric attraction before the development process.

[0008] When a cleaning blade is used, the hardness or contact pressure of the blade needs to be increased to improve the cleaning performance, which accelerates the wear of the photoreceptor surface, causes potential fluctuations or sensitivity fluctuations, produces image abnormalities, and causes problems in color balance or reproducibility in color machines.

[0009] In addition, with the increase in the amount of information processed (increase in the number of prints) and the development or popularity of color printers, the printing speed is increasing or the device is miniaturized and component-saving, and it is also required to respond to various usage environments. Under such circumstances, the requirements for photoreceptors with small changes in image characteristics or electrical characteristics due to repeated use or changes in the usage environment (room temperature and environment) are significantly increasing, and in the previous technology, these requirements cannot be fully met at the same time. In particular, there is a strong demand to solve the problem of reduced print density caused by changes in the potential of the photoreceptor in a low temperature environment and to eliminate ghosting. In addition, the generation of cracks caused by the adhesion of sebum from the human body to the surface of the photoreceptor has also become a problem.

[0010] In order to solve these problems, various methods for improving the outermost surface layer of photoreceptors have been proposed. For example, in Patent Documents 1 and 2, in order to improve the durability of the photoreceptor surface, a method of adding fillers to the surface layer of the photosensitive layer is proposed. However, in the method of dispersing the filler in the layer, it is difficult to disperse the filler evenly. In addition, if there are agglomerates of the filler, the permeability of the layer decreases, the filler scatters the exposure light, resulting in uneven charge transport or charge generation, and decreased image characteristics. Moreover, although there is also a method of adding a dispersing material to improve the dispersibility of the filler, in this case, the dispersing material itself affects the photoreceptor characteristics, so it is difficult to achieve a balance between the dispersibility of the filler and the characteristics of the photoreceptor.

[0011] To solve this problem, for example, Patent Documents 3 and 4 propose techniques for improving the content or dispersion state of fillers. However, the effects of these techniques are insufficient, and there is a need to develop an electrophotographic photoreceptor that is excellent in printing durability and repetition stability and can achieve high resolution.

[0012] In addition, Patent Document 5 discloses an organic photoreceptor which has been subjected to multiple surface treatments and, as the final surface treatment, has been subjected to a surface treatment based on a silazane compound, and contains inorganic particles having an average primary particle size (Dp) of 5 to 100 nm in the surface layer. Patent Document 6 discloses an electronic photographic photoreceptor which contains a specified functional material in the photosensitive layer located on the outermost surface and contains silica particles in a specified amount.

[0013] In addition, regarding the improvement of image quality characteristics, electrical characteristics, or elimination of ghost images with respect to environmental changes, for example, Patent Document 7 records the technical idea of ​​an electronic photography photoreceptor that is highly sensitive to environmental changes and extremely stable by combining oxytitanium phthalocyanine with butanediol added as a charge generating material and a naphthalenetetracarboxylic acid diimide compound as a charge transport material in a photosensitive layer. In addition, Patent Document 8 discloses a specific example of a charge generating / transporting layer containing a phthalocyanine compound as a charge generating material and a naphthalenetetracarboxylic acid diimide compound as an electron transport material for a positively charged laminated electronic photography photoreceptor having a laminated photosensitive layer formed on a conductive substrate and having a charge transport layer and a charge generating / transporting layer laminated in sequence. Moreover, Patent Document 9 discloses that in a single-layer positively charged photoreceptor, by using three or more specific electron transport agents at a certain ratio relative to a hole transport material, the crystallization of the photosensitive layer and the generation of transfer memory (ghosting) are suppressed, but the printing resistance is insufficient, and it is not possible to take into account both the suppression of the generation of ghosting and durability.

[0014] Prior art literature

[0015] Patent Literature

[0016] Patent Document 1: Japanese Patent Application Laid-Open No. 1-205171

[0017] Patent Document 2: Japanese Patent Laid-Open No. 7-333881

[0018] Patent Document 3: Japanese Patent Laid-Open No. 8-305051

[0019] Patent Document 4: Japanese Patent Application Publication No. 2006-201744

[0020] Patent Document 5: Japanese Patent Application Publication No. 2006-301247

[0021] Patent Document 6: Japanese Patent Application Publication No. 2015-175948

[0022] Patent Document 7: Japanese Patent Application Publication No. 2015-94839

[0023] Patent Document 8: Japanese Patent Application Publication No. 2014-146001

[0024] Patent Document 9: Japanese Patent Application Publication No. 2018-4695 Summary of the invention

[0025] Technical problem to be solved by the invention

[0026] As described above, various studies have been conducted on improving the photosensitive layer of the photosensitive body. However, in the technology disclosed in the above-mentioned patent documents, the relationship between the materials constituting the photosensitive layer has not been fully studied, and it is impossible to stably ensure good electrical properties and image properties while sufficiently reducing the amount of wear on the surface of the photosensitive body.

[0027] Therefore, an object of the present invention is to solve the above-mentioned problems and to provide an electrophotographic photoreceptor which reduces the wear of the photosensitive layer, suppresses the generation of ghosting, and can stably obtain good images, a method for producing the same, and an electrophotographic apparatus equipped with the same.

[0028] Technical solutions adopted to solve technical problems

[0029] The present inventors have conducted intensive studies and have found that by blending a specific combination of two electron transport materials, a resin binder, and a silane coupling agent surface treated filler in a photosensitive layer, it is possible to provide an electrophotographic photoreceptor having a reduced amount of photosensitive layer wear and a reduced degree of ghost images.

[0030] That is, the first embodiment of the present invention is an electrophotographic photoreceptor comprising a conductive substrate and

[0031] A photosensitive layer comprising a charge generating material, a hole transporting material, a first electron transporting material, a second electron transporting material, a resin binder, and an inorganic oxide filler surface-treated with a silane coupling agent, and disposed on the conductive substrate.

[0032] The difference ΔSPa between the dipole force terms of the Hansen solubility parameters between the first electron transport material and the silane coupling agent satisfies the relationship of ΔSPa<2.50,

[0033] The difference ΔSPb between the dipole force terms of the Hansen solubility parameters of the second electron transport material and the silane coupling agent satisfies the relationship of ΔSPb<2.50.

[0034] The difference ΔSPc between the dipole force terms of the Hansen solubility parameters of the first electron transport material and the second electron transport material satisfies the relationship of 0.30<ΔSPc<1.00, and,

[0035] The difference ΔSPd between the London dispersion force term of the Hansen solubility parameter of the resin binder and the silane coupling agent satisfies the relationship of ΔSPd<2.00, and,

[0036] The ratio of the content of the second electron transport material to the contents of the first electron transport material and the second electron transport material is 3 mass % or more and 40 mass % or less.

[0037] Here, the Hansen solubility parameter is calculated using the Hansen equation that can separate the interaction between molecular forces into a London dispersion force term, an inter-dipole force term, and a hydrogen bonding force term.

[0038] The dipole force term δp of the Hansen solubility parameter is calculated using the following formula.

[0039]

[0040] (Where Fp is the aggregation energy related to the Kreveren and Hoftyzer parameters of the dipoles of each component, and V is the molar volume of each component.)

[0041] In addition, the London dispersion force term δd of the Hansen solubility parameter was calculated using the following formula.

[0042] δd=ΣFd / V(J 1 / 2 / cm 3 / 2 )

[0043] (Where Fd is the aggregation energy of the Kreveren and Hoftyzer parameters related to the London dispersion forces of each component, and V is the molar volume of each component.)

[0044] In addition, in the present invention, in order to obtain the difference between the two materials for each term of the above solubility parameter, the dipole force terms of the Hansen solubility parameter are marked as SPa, SPb and SPc, and the London dispersion force term is marked as SPd.

[0045] In addition, regarding the above formula, the value equivalent to the coagulation energy density and the value of the molar volume of each component are stored in a database for each atomic group (Kreveren and Hoftyzer parameter), which is introduced in the literature.

[0046] The present inventors obtained various items of the Hansen solubility parameters of the photoreceptor material, and studied the correlation between the compatibility between the first electron transport material and the second electron transport material and the silane coupling agent and the filler dispersibility, the correlation between the compatibility between the first and second electron transport materials and the filler dispersibility, and the correlation between the compatibility between the resin binder and the silane coupling agent and the filler dispersibility. As a result of the study, it was found that the difference in the dipole force term between the first and second electron transport materials and the silane coupling agent, and between the first and second electron transport materials, and the difference in the London dispersion force term between the resin binder and the silane coupling agent each showed a high correlation with the filler dispersibility.

[0047] According to the research of the present inventors, among the materials of the photosensitive layer, if the difference in dipole force terms ΔSPa between the first electron transport material and the silane coupling agent, the difference in dipole force terms ΔSPb between the second electron transport material and the silane coupling agent, the difference in dipole force terms ΔSPc between the first electron transport material and the second electron transport material, and the difference in London dispersion force terms ΔSPd between the resin binder and the silane coupling agent respectively satisfy the relationships represented by the following formulas (i) to (iv), a photoreceptor having excellent printing durability and ghost image reduction effect can be obtained.

[0048] ΔSPa<2.50 (i)

[0049] ΔSPb<2.50 (ii)

[0050] 0.30<ΔSPc<1.00 (iii)

[0051] ΔSPd<2.00 (iv)

[0052] It is believed that in the composition of the photosensitive layer, by selecting a combination of materials whose ΔSPa, ΔSPb and ΔSPd values ​​are within the above-mentioned ranges, the filler contained in the photosensitive layer is fully dispersed, the strength of the film is improved, and the wear resistance is improved. Moreover, by selecting a combination of two electron transport materials whose ΔSPc values ​​are within the above-mentioned ranges, the compatibility is also good, the formation of electron traps is suppressed, and the generation of ghosting is reduced.

[0053] The first electron transport material and the second electron transport material are preferably selected from compounds represented by the following general formulae (ET1) and (ET2).

[0054]

[0055] (In formula (ET1), R1 and R2 are the same or different and represent a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group which may have a substituent, a cycloalkyl group, an aralkyl group which may have a substituent, or a halogenated alkyl group. R3 represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an aryl group which may have a substituent, a cycloalkyl group, an aralkyl group which may have a substituent, or a halogenated alkyl group. R4 to R8 are the same or different and represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group which may have a substituent, an aralkyl group which may have a substituent, a phenoxy group which may have a substituent, a halogenated alkyl group, a cyano group, or a nitro group. In addition, two or more groups may be combined to form a ring. The substituent represents a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a hydroxyl group, a cyano group, an amino group, a nitro group, or a halogenated alkyl group.)

[0056]

[0057] (In formula (ET2), R9, R 10 The same or different groups represent a hydrogen atom, a halogen atom, a cyano group, a nitro group, a hydroxyl group, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group which may have a substituent, a heterocyclic group which may have a substituent, an ester group, a cycloalkyl group, an aralkyl group which may have a substituent, an allyl group, an amide group, an amino group, an acyl group, an alkenyl group, an alkynyl group, a carboxyl group, a carbonyl group, a carboxylic acid group, or a halogenated alkyl group. The substituent represents a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a hydroxyl group, a cyano group, an amino group, a nitro group, or a halogenated alkyl group.

[0058] Furthermore, the first electron transport material and the second electron transport material are preferably compounds represented by the following structural formulas (A1) and (A2).

[0059]

[0060] The primary particle size of the inorganic oxide filler is preferably from 1 nm to 300 nm.

[0061] The photosensitive layer may contain the charge generating material, the hole transport material, the first electron transport material, the second electron transport material, the resin binder, and the inorganic oxide filler in a single layer. In this case, in the solid component of the photosensitive layer, the content F (mass %) of the inorganic oxide filler is preferably less than the content E (mass %) of the first electron transport material and the second electron transport material, and the content F satisfies the relationship of 2≤F≤15.

[0062] The photosensitive layer includes a charge transport layer and a charge generation layer sequentially stacked on the conductive substrate, and the charge generation layer may include the charge generation material, the hole transport material, the first electron transport material, the second electron transport material, the resin binder, and the inorganic oxide filler. In this case, in the solid component of the charge generation layer, it is preferred that the content F (mass %) of the inorganic oxide filler is less than the content E (mass %) of the first electron transport material and the second electron transport material, and the content F satisfies the relationship of 2≤F≤15. In addition, in the solid component of the charge generation layer, it is preferred that the content E (mass %) of the first electron transport material and the second electron transport material is greater than the content H (mass %) of the hole transport material, and the content E and the content H satisfy 1.5≤E / H≤10.0.

[0063] A second embodiment of the present invention is a method for producing an electrophotographic photoreceptor, the method comprising the step of forming the photosensitive layer by a dip coating method when producing the electrophotographic photoreceptor.

[0064] Moreover, a third embodiment of the present invention is an electrophotographic apparatus equipped with the above-mentioned electrophotographic photoreceptor.

[0065] Effects of the Invention

[0066] If the above-mentioned embodiment of the present invention is adopted, it is known that the electronic photography characteristics of the photoreceptor can be maintained by a specific combination of materials, and the amount of wear of the photosensitive layer can be reduced, the generation of ghosting can be suppressed, and a good image can be obtained stably for a long time, and the mechanical strength can be improved. It is believed that this is because by mixing a specific combination of two electron transport materials, a resin binder, and a silane coupling agent surface treatment filler in the photosensitive layer as the surface of the photoreceptor, the filler is fully dispersed in the photosensitive layer, and the durability of the photosensitive layer against wear is improved, while the light transmittance of the layer is improved to prevent the scattering of exposure light. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1This is a schematic cross-sectional view showing an example of the positively charged single-layer electrophotographic photoreceptor of the present invention.

[0068] Figure 2 This is a schematic cross-sectional view showing an example of the positively charged laminated electrophotographic photoreceptor of the present invention.

[0069] Figure 3 This is a schematic structural diagram showing an example of the electronic photographing device of the present invention.

[0070] Figure 4 This is a schematic structural diagram showing another example of the electronic photographing device of the present invention.

[0071] Figure 5 It is an explanatory diagram showing an interference fringe image. DETAILED DESCRIPTION

[0072] Hereinafter, specific embodiments of the electrophotographic photoreceptor of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following description at all.

[0073] Figure 1 1 is a schematic cross-sectional view showing an example of an electrophotographic photoreceptor of the present invention, showing a positively charged single-layer photoreceptor. As shown in the figure, in the positively charged single-layer photoreceptor, an undercoat layer 2 and a single-layer photosensitive layer 3 having both charge generation function and charge transport function are sequentially stacked on a conductive substrate 1. In addition, the undercoat layer 2 can also be provided as needed.

[0074] also, Figure 2 1 is a schematic cross-sectional view showing another example of the electrophotographic photoreceptor of the present invention, showing a positively charged laminated photoreceptor. As shown in the figure, the positively charged laminated photoreceptor has a laminated photosensitive layer 6. The laminated photosensitive layer 6 is composed of a charge transport layer 4 having a charge transport function and a charge generating layer 5 having a charge generating function, which are sequentially laminated on a conductive substrate 1 via an undercoat layer 2. In addition, the undercoat layer 2 can also be provided as needed.

[0075] The conductive substrate 1 plays the role of the electrode of the photoreceptor and also serves as a support for each layer constituting the photoreceptor, and can be in any shape such as a cylinder, a plate, a film, etc. As the material of the conductive substrate 1, metals such as aluminum, stainless steel, and nickel, or materials such as glass and resin with conductive treatment applied to the surface can be used.

[0076] The lower coating layer 2 is composed of a layer with resin as the main component or a metal oxide film such as an aluminum oxide film, and can also be set to a laminated structure of an aluminum oxide layer and a resin layer. The lower coating layer 2 is provided as required for the purpose of controlling the injectability of charge from the conductive substrate 1 to the photosensitive layer, or for the purpose of coating the defects on the surface of the conductive substrate 1, improving the bonding property of the photosensitive layer and the conductive substrate 1, etc. As the resin material used for the lower coating layer 2, insulating polymers such as casein, polyvinyl alcohol, polyamide, melamine, cellulose, and conductive polymers such as polythiophene, polypyrrole, polyaniline can be cited, and these resins can be used alone or in a suitable combination. In addition, metal oxides such as titanium dioxide and zinc oxide can also be contained in these resins.

[0077] (Positively charged single-layer photoreceptor)

[0078] In the positively charged single-layer photoreceptor, the single-layer photosensitive layer 3 is a photosensitive layer formed on the undercoat layer 2. The single-layer photosensitive layer 3 is a single-layer positively charged photosensitive layer mainly containing a charge generating material, a hole transporting material, an electron transporting material and a resin binder in a single layer. The photosensitive layer 3 further contains an inorganic oxide filler surface-treated with a silane coupling agent.

[0079] As the charge generating material, X-type metal-free phthalocyanine, α-type oxytitanium phthalocyanine, β-type oxytitanium phthalocyanine, Y-type oxytitanium phthalocyanine, γ-type oxytitanium phthalocyanine, amorphous oxytitanium phthalocyanine can be used alone or in combination, and a suitable material can be selected according to the wavelength range of the exposure light source used for image formation. From the viewpoint of high sensitivity, oxytitanium phthalocyanine with high quantum efficiency is the most suitable.

[0080] As the hole transport material, various hydrazone compounds, styrene compounds, diamine compounds, butadiene compounds, indole compounds and the like can be used alone or in appropriate combination. From the viewpoint of cost and performance, styrene compounds containing a triphenylamine skeleton are suitable.

[0081] The electron transport material includes a first and a second electron transport material. The first and the second electron transport material include, for example, succinic anhydride, maleic anhydride, dibromosuccinic anhydride, phthalic anhydride, 3-nitrophthalic anhydride, 4-nitrophthalic anhydride, pyromellitic anhydride, pyromellitic acid, trimellitic acid, trimellitic anhydride, phthalimide, 4-nitrophthalimide, tetracyanoethylene, tetracyanoquinodimethane, tetrachloroquinone, tetrabromobenzoquinone, o-nitrobenzoic acid, malononitrile, trinitrofluorenone, trinitrothioxanthone, dinitrobenzene, dinitroanthracene, dinitroacridine, nitroanthraquinone, dinitroanthraquinone, thiopyran compound, quinone compound, benzoquinone compound, diphenoquinone compound, naphthoquinone compound, anthraquinone compound, distyrylquinone compound, azomethine compound, naphthalenetetracarboxylic acid diimide compound, etc.

[0082] The first electron transport material and the second electron transport material are preferably selected from an azomethine compound represented by the following general formula (ET1) and a naphthalenetetracarboxylic acid diimide compound represented by the following general formula (ET2). Moreover, as the first electron transport material, the naphthalenetetracarboxylic acid diimide compound represented by the following general formula (ET2) is preferred, and as the second electron transport material, the azomethine compound represented by the following general formula (ET1) is preferred. The naphthalenetetracarboxylic acid diimide compound contributes to potential stability in environmental changes. The azomethine compound contributes to the suppression of ghost images.

[0083]

[0084] (In formula (ET1), R1 and R2 are the same or different and represent a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group which may have a substituent, a cycloalkyl group, an aralkyl group which may have a substituent, or a halogenated alkyl group. R3 represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an aryl group which may have a substituent, a cycloalkyl group, an aralkyl group which may have a substituent, or a halogenated alkyl group. R4 to R8 are the same or different and represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group which may have a substituent, an aralkyl group which may have a substituent, a phenoxy group which may have a substituent, a halogenated alkyl group, a cyano group, or a nitro group. In addition, two or more groups may be combined to form a ring. The substituent represents a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a hydroxyl group, a cyano group, an amino group, a nitro group, or a halogenated alkyl group.)

[0085]

[0086] (In formula (ET2), R9, R 10 The same or different groups represent a hydrogen atom, a halogen atom, a cyano group, a nitro group, a hydroxyl group, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group which may have a substituent, a heterocyclic group which may have a substituent, an ester group, a cycloalkyl group, an aralkyl group which may have a substituent, an allyl group, an amide group, an amino group, an acyl group, an alkenyl group, an alkynyl group, a carboxyl group, a carbonyl group, a carboxylic acid group, or a halogenated alkyl group. The substituent represents a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a hydroxyl group, a cyano group, an amino group, a nitro group, or a halogenated alkyl group.

[0087] Specific examples of electron transport materials such as naphthalenetetracarboxylic acid diimide compounds or azomethine compounds are shown in the following structural formulas A1 to A18. Suitable examples of the first electron transport material and the second electron transport material are a combination of compounds selected from structural formulas A1, A12, A13, A14 and A15, and compounds selected from structural formulas A2 and A11. In addition, the first electron transport material and the second electron transport material are suitably a combination of compounds represented by structural formulas (A1) and (A2).

[0088]

[0089] As the resin binder of the single-layer photosensitive layer 3, various polycarbonate resins such as bisphenol A type, bisphenol Z type, bisphenol A type-biphenyl copolymer, bisphenol Z type-biphenyl copolymer, polyphenylene resin, polyester resin, polyvinyl acetal resin, polyvinyl butyral resin, polyvinyl alcohol resin, vinyl chloride resin, vinyl acetate resin, polyethylene resin, polypropylene resin, acrylic resin, polyurethane resin, epoxy resin, melamine resin, silicone resin, polyamide resin, polystyrene resin, polyacetal resin, polyarylate resin, polysulfone resin, methacrylate polymers and copolymers thereof can be used. In addition, resins of the same type with different molecular weights can be mixed and used.

[0090] Specific examples of suitable resin binders include polycarbonate resins having repeating units represented by the following structural formulas (B1) to (B4), such as bisphenol Z type and bisphenol Z type-biphenyl copolymer.

[0091]

[0092] The weight average molecular weight of the resin binder is preferably 5,000 to 250,000, more preferably 10,000 to 200,000 in a polystyrene-equivalent GPC (gel permeation chromatography) analysis.

[0093] The inorganic oxide filler surface-treated with a silane coupling agent is a material in which a silane coupling agent is attached to the surface of the inorganic oxide filler.

[0094] As inorganic oxide fillers, in addition to microparticles containing silicon dioxide as the main component, microparticles containing aluminum oxide, zirconium oxide, titanium oxide, tin oxide, zinc oxide, etc. as the main component are exemplified. These microparticles have hydroxyl groups on the surface when used, and if the microparticles are mixed in the coating liquid as they are, the microparticles are easily aggregated.

[0095] The primary particle size (particle size) of the inorganic oxide filler is preferably within the range of 1 nm to 300 nm, more preferably 5 nm to 100 nm, and further preferably 10 nm to 50 nm. If the primary particle size of the inorganic oxide filler is less than 1 nm, the dispersion state is sometimes uneven due to agglomeration. On the other hand, if the primary particle size of the inorganic oxide filler exceeds 300 nm, the scattering of light becomes larger and image loss sometimes occurs. In addition, the primary particle size is the number average diameter measured using a scanning microscope that can directly observe the surface shape of the particles.

[0096] As the inorganic oxide filler, fine particles mainly composed of silica are preferred. As a method for manufacturing silica fine particles, a method of manufacturing using water glass as a raw material known as the wet method, a method of reacting chlorosilane or the like in the gas phase known as the dry method, a method using alkoxide as a silica precursor as a raw material, etc. are known. As such silica fine particles, YA010C manufactured by Toyo Tsusho Corporation (Admatechs Co., Ltd.) etc. can be cited.

[0097] The surface treatment of the inorganic oxide filler using a silane coupling agent reduces the cohesiveness between the inorganic oxide fillers by the bonding of the hydroxyl groups on the surface of the inorganic oxide filler and the silane coupling agent.

[0098] As the silane coupling agent, specifically, for example, compounds represented by the following structural formulas C1 to C5 can be cited.

[0099]

[0100] If a large amount of foreign metals are present as impurities in the inorganic oxide filler, during surface treatment, metals different from the normal oxide sites cause defects to occur, the charge distribution on the surface changes, and starting from this site, the filler cohesiveness increases. As a result, the amount of aggregates in the coating liquid or the photosensitive layer increases. Therefore, it is preferred that the filler be of high purity. The content of each metal other than the metal elements constituting the inorganic filler is preferably controlled below 1000 ppm.

[0101] On the other hand, in order to make the surface treatment agent react充分 and improve the activity of the silica surface, it is preferred to add an extremely small amount of foreign metals. The surface treatment agent reacts with the hydroxyl groups present on the surface of silica, but if silica contains a trace amount of other metals, due to the influence caused by the difference in electronegativity between metals, the reactivity of the silanol group (hydroxyl group) adjacent to the other metals present on the surface of silica will be increased. Since the reactivity of this hydroxyl group with the surface treatment agent is high, if it reacts stubbornly with the surface treatment agent and remains, it will become a cause of aggregation compared with other hydroxyl groups. It is considered that after the reaction of these surface treatment agents, by reacting the surface treatment agent with other hydroxyl groups, due to the effect of the surface treatment agent and the effect of reducing the charge bias on the surface caused by the foreign metals on the surface, the cohesiveness between the silicas is greatly improved. In the embodiment of the present invention, when the inorganic oxide contains a trace amount of other metals, the reactivity of the surface treatment agent becomes better, and as a result, the dispersibility based on the surface treatment is improved, which is therefore preferred. The increase in cohesiveness in the case where a large amount of the above foreign metals are present as impurities and the improvement in dispersibility caused by the inclusion of this extremely small amount of foreign metals can be said to be different mechanisms.

[0102] About silicon dioxide, if adding aluminum in the range below 1000ppm, it is conducive to surface treatment. The adjustment of the amount of aluminum in silicon dioxide can be carried out using the method recorded in Japanese Patent Laid-Open 2004-143028 Gazette, Japanese Patent Laid-Open 2013-224225 Gazette, etc., but as long as it can be controlled within the desired range, there is no particular restriction on the adjustment method. Specifically, as a method for more appropriately controlling the amount of aluminum on the surface of silicon dioxide, for example, there is the following method. First, there is a method for controlling the amount of aluminum on the surface of silicon dioxide when manufacturing silicon dioxide particles, after making the silicon dioxide particles grow into a shape smaller than the intended silicon dioxide particle size, adding aluminum alkoxide as an aluminum source, etc. In addition, there is a method of adding silicon dioxide particles in a solution containing aluminum chloride, applying aluminum chloride solution on the surface of silicon dioxide particles, drying it, and firing it, or a method of reacting a mixed gas of an aluminum halide compound and a silicon halide compound, etc.

[0103] In addition, it is known that the structure of silica is such that a plurality of silicon atoms and oxygen atoms form a continuous network bond structure in a ring shape. When containing aluminum, the number of atoms constituting the ring structure of silica is determined by the effect of mixing aluminum and is larger than that of ordinary silica. Due to this effect, the steric hindrance when the hydroxyl groups on the surface of the silica containing aluminum react with the surface treatment agent is milder than that of the ordinary silica surface, resulting in a surface treated silica having improved reactivity with the surface treatment agent and improved dispersibility compared to when ordinary silica reacts with the same surface treatment agent.

[0104] In order to achieve the effects of the embodiment of the present invention, wet-process silica is more suitable for controlling the amount of aluminum. In addition, considering the reactivity of the surface treatment agent, the content of aluminum relative to silica is preferably 1 ppm or more.

[0105] The form of the inorganic oxide is not particularly limited, but in order to reduce the cohesion and obtain a uniform dispersion state, the sphericity of the inorganic oxide is preferably 0.8 or more, more preferably 0.9 or more.

[0106] In addition, when an inorganic oxide is used in the charge transport layer of a photoreceptor that is expected to have a high resolution, it is preferable to consider the influence caused by α rays and the like from the material added to the charge transport layer. For example, taking a semiconductor memory element as an example, although the memory element maintains the type of data stored in memory according to the presence or absence of charge accumulation, the size of the accumulated charge will also become smaller due to miniaturization, and the type of data will change due to a certain degree of charge that changes due to α rays irradiated from the outside, resulting in unexpected data changes. In addition, since the current flowing in the semiconductor element also becomes smaller, the current (noise) generated by α rays is relatively large compared to the size of the signal, and there is a risk of malfunction. Just like this phenomenon, if the influence of the charge transport layer of the photoreceptor on the charge movement is taken into account, it is more preferable to use a material that generates less α rays in the film constituent material. Specifically, it is effective to reduce the concentration of uranium or thorium in the inorganic oxide, preferably thorium is below 30 ppb and uranium is below 1 ppb. As a production method for reducing the amount of uranium or thorium in an inorganic oxide, for example, there is a description in Japanese Patent Application Laid-Open No. 2013-224225, etc. However, the method is not limited to this method as long as the concentration of these elements can be reduced.

[0107] In the combination of the electron transport material, the resin binder, and the silane coupling agent used in the single-layer photosensitive layer 3, it is preferred that a specific relationship is satisfied regarding the Hansen solubility parameter. The difference ΔSPa between the dipole force terms of the Hansen solubility parameter between the first electron transport material and the silane coupling agent satisfies the relationship of ΔSPa<2.50, and the difference ΔSPb between the dipole force terms of the Hansen solubility parameter between the second electron transport material and the silane coupling agent satisfies the relationship of ΔSPb<2.50. The difference ΔSPc between the dipole force terms of the Hansen solubility parameter between the first electron transport material and the second electron transport material satisfies the relationship of 0.30<ΔSPc<1.00. Moreover, the difference ΔSPd between the London dispersion force terms of the Hansen solubility parameter between the resin binder and the silane coupling agent satisfies the relationship of ΔSPd<2.00.

[0108] By selecting materials that satisfy such a relationship, sufficient compatibility can be obtained between the electron transport material, the resin binder and the silane coupling agent, especially between the first electron transport material and the second electron transport material in the single-layer photosensitive layer 3, and the dispersibility of the inorganic oxide filler can be improved. High dispersibility can fully reduce the amount of wear on the surface of the photoreceptor while ensuring good electrical characteristics and image characteristics.

[0109] Regarding the Hansen solubility parameters of the silane coupling agent, ΔSPa and ΔSPb are preferably ΔSPa≤2.40 and ΔSPb≤2.40, and ΔSPd is ΔSPd<1.90, and the smaller these are, the more preferably.

[0110] Regarding the Hansen solubility parameters of the first electron transport material and the second electron transport material, ΔSPc is in the range of 0.30<ΔSPc<1.00, preferably in the range of 0.30<ΔSPc<0.80, and more preferably in the range of 0.30<ΔSPc<0.60. If ΔSPc is below 0.30, since the compatibility between the first electron transport material and the second electron transport material is relatively large, even if a silane coupling agent that satisfies ΔSPa and ΔSPb is selected, a sufficient effect cannot be obtained in filler dispersibility. In addition, if ΔSPc is above 1.00, the compatibility between the two electron transport materials is insufficient, the dispersibility at the molecular level is reduced, and charge traps are formed, so the ghost reduction effect cannot be fully obtained. If it is in the range of ΔSPc<0.60, an excellent ghost reduction effect can be obtained.

[0111] The content of each material relative to the solid content of the single-layer photosensitive layer 3 is as follows. The content of the charge generating material is suitably 0.1 to 5% by mass, more suitably 0.5 to 3% by mass. The content of the hole transport material is suitably 3 to 60% by mass, more suitably 10 to 40% by mass. The content of the electron transport material is suitably 1 to 50% by mass, more suitably 5 to 20% by mass. The content of the inorganic oxide filler surface-treated with a silane coupling agent is suitably 2 to 15% by mass. The content of the resin binder is suitably 20 to 80% by mass, more suitably 30 to 70% by mass. The content of the resin binder can be suitably 20 to 90% by mass, more suitably 30 to 80% by mass, relative to the solid content of the photosensitive layer 3 excluding the inorganic oxide filler.

[0112] The ratio of the content of the electron transport material to the hole transport material is in the range of 1:1 to 1:4, preferably in the range of 1:1 to 1:3. From the viewpoint of the transport balance of holes and electrons, this range of ratios is preferred in sensitivity characteristics, charging characteristics, and fatigue characteristics. The proportion of the content of the second electron transport material relative to the content of the first electron transport material and the second electron transport material is preferably in the range of 3% by mass to 40% by mass. If the content of the second electron transport material is not in the range of 3% by mass to 40% by mass, the improvement of electron injectability is insufficient, and the effect of suppressing ghosting cannot be fully obtained.

[0113] In addition, in the solid content of the single-layer photosensitive layer 3, if the content of the inorganic oxide filler is F (mass %) and the content of the first electron transport material and the second electron transport material is E (mass %), it is preferred that the content F is less than the content E. When the content F is the same as or greater than the content E, the electron injectability of the electron transport material is not sufficiently improved, and there is a possibility that the ghost suppression effect cannot be obtained.

[0114] The ratio of the second electron transport material content E2 (mass %) to the inorganic oxide filler content F (mass %) is preferably in the range of 1 / 15 to 20. If it is set to a ratio other than this, the electron injectability is insufficient and the ghost suppression effect may not be obtained.

[0115] The film thickness of the single-layer photosensitive layer 3 is preferably in the range of 12 to 40 μm, preferably 15 to 35 μm, and more preferably 20 to 30 μm, from the viewpoint of ensuring practically effective performance.

[0116] The single-layer photosensitive layer 3 may contain an antioxidant or a light stabilizer or other anti-degradation agent for the purpose of improving environmental resistance or stability to harmful light, as required. Examples of compounds used for such purposes include chromanol derivatives such as tocopherol, esterified compounds, polyaryl alkane compounds, hydroquinone derivatives, etherified compounds, dietherified compounds, benzophenone derivatives, benzotriazole derivatives, thioether compounds, phenylenediamine derivatives, phosphonates, phosphites, phenolic compounds, hindered phenol compounds, linear amine compounds, cyclic amine compounds, hindered amine compounds, and the like.

[0117] The single-layer photosensitive layer 3 may contain a leveling agent such as silicone oil or fluorine oil in order to improve the homogenization of the formed film or to impart lubricity. In addition to the inorganic oxide filler surface-treated with a silane coupling agent, metal oxide particles such as calcium oxide, metal sulfates such as barium sulfate and calcium sulfate, metal nitride particles such as silicon nitride and aluminum nitride, or fluorine resin particles such as tetrafluoroethylene resin, fluorine-based composite graft polymer resins, etc. may be contained in order to adjust the film hardness or reduce the friction coefficient, impart lubricity, etc. In addition, other known additives may be contained as needed within the range that does not significantly impair the electronic photography characteristics.

[0118] (Positively charged laminated photoreceptor)

[0119] In the case of a positively charged laminated photoreceptor, the laminated photosensitive layer 6 includes a charge transport layer 4 and a charge generation layer 5. The charge transport layer 4 and the charge generation layer 5 are sequentially laminated on the conductive substrate 1. In the positively charged laminated photoreceptor, the charge transport layer 4 includes a hole transport material and a resin binder, and the charge generation layer 5 includes a charge generation material, a hole transport material, a first electron transport material, a second electron transport material, an inorganic oxide filler surface-treated with a silane coupling agent, and a resin binder. An undercoat layer 2 may also be provided between the conductive substrate 1 and the charge transport layer 4.

[0120] As the hole transport material and the resin binder in the charge transport layer 4, the same materials as those exemplified in the single-layer photosensitive layer 3 can be applied. The content of the hole transport material in the charge transport layer 4 is preferably 10 to 80% by mass, more preferably 20 to 70% by mass, relative to the solid content of the charge transport layer 4. The content of the resin binder in the charge transport layer 4 is preferably 20 to 90% by mass, more preferably 30 to 80% by mass, relative to the solid content of the charge transport layer 4. In order to maintain a practically effective surface potential, the film thickness of the charge transport layer 4 is preferably in the range of 3 to 50 μm, and more preferably in the range of 15 to 40 μm.

[0121] As the charge generating material, hole transporting material, first electron transporting material, second electron transporting material, inorganic oxide filler surface-treated with a silane coupling agent, and resin binder in the charge generating layer 5 , the same materials as those exemplified in the single-layer photosensitive layer 3 can be used.

[0122] In the case of a positively charged laminated photoreceptor, the combination of the electron transport material, the resin binder, and the silane coupling agent used in the charge generating layer 5 preferably satisfies the same specific relationship as in the single-layer photosensitive layer 3 with respect to the Hansen solubility parameter.

[0123] The content of each material of the charge generating layer 5 relative to the solid content is as follows. The content of the charge generating material is suitably 0.1 to 5% by mass, more suitably 0.5 to 3% by mass. The content of the hole transport material is suitably 1 to 30% by mass, more suitably 5 to 20% by mass. The content of the electron transport material is suitably 5 to 60% by mass, more suitably 10 to 40% by mass. The content of the inorganic oxide filler surface-treated with a silane coupling agent is suitably 2 to 15% by mass. The content of the resin binder is suitably 20 to 80% by mass, more suitably 30 to 70% by mass.

[0124] The ratio of the content of the second electron transport material to the contents of the first electron transport material and the second electron transport material is preferably in the range of 3 mass % to 40 mass %.

[0125] In the solid component of the charge generation layer 5, if the content of the inorganic oxide filler is F (mass %), the content of the first electron transport material and the second electron transport material is E (mass %), and the content of the hole transport material is H (mass %), the content F is preferably less than the content E, and the content E is preferably greater than the content H (mass %). In addition, the ratio of the content E2 (mass %) of the second electron transport material to the content F (mass %) of the inorganic oxide filler is preferably in the range of 1 / 15 to 20.

[0126] By setting the ratio within these ranges, the electron injectability is improved, the balance of charge transfer with the hole transport material is also improved, and the ghost suppression effect can be effectively obtained.

[0127] The ratio of the content E (mass %) of the electron transport material to the content H (mass %) of the hole transport material is preferably 1.5≤E / H≤10.0, that is, H:E is in the range of 1:1.5 to 1:10, and more preferably in the range of 1:2 to 1:10. The electron transport material includes a first electron transport material and a second electron transport material. Even if the content of the electron transport material relative to the hole transport material increases, due to the use of the first and second electron transport materials, crystallization in the photosensitive layer is suppressed and the filler can be fully dispersed.

[0128] The film thickness of the charge generating layer 5 can be set to be the same as that of the single-layer photosensitive layer 3 of the single-layer photoreceptor. The film thickness is preferably in the range of 3 to 100 μm, and more preferably in the range of 5 to 40 μm.

[0129] In addition, the laminated photosensitive layer 6 may contain a degradation inhibitor such as an antioxidant or a light stabilizer, a leveling agent, and the like, as necessary, similarly to the single-layer photosensitive layer 3 .

[0130] (Method for producing photoreceptor)

[0131] The method for producing a photoreceptor according to an embodiment of the present invention is a method for producing the electrophotographic photoreceptor, comprising the step of forming a photosensitive layer by a dip coating method.

[0132] The method for manufacturing a single-layer photoreceptor includes the steps of dissolving the above-mentioned charge generating material, hole transporting material, first electron transporting material, second electron transporting material, resin binder, and inorganic oxide filler surface-treated with a silane coupling agent in a solvent, dispersing them, and preparing a coating liquid, and applying the coating liquid to the periphery of a conductive substrate through an undercoat layer by dip coating as needed, drying it, and forming a photosensitive layer.

[0133] The manufacturing method of a laminated photoreceptor includes a process of forming a charge transport layer on a conductive substrate and a process of forming a charge generation layer. The process of forming the charge transport layer includes a process of dissolving any hole transport material and a resin binder in a solvent, preparing a coating liquid for forming the charge transport layer, and preparing the process, and applying the coating liquid to the periphery of the conductive substrate through an undercoat layer as needed by a dip coating method, and drying the process. Next, the process of forming the charge generation layer includes dissolving the above-mentioned charge generation material, electron transport material, hole transport material, resin binder, and inorganic oxide filler surface-treated with a silane coupling agent in a solvent, dispersing them, preparing a coating liquid for forming the charge generation layer, and preparing the process, and applying the coating liquid to the above-mentioned charge transport layer by a dip coating method, drying it, and forming the charge generation layer. By such a manufacturing method, a laminated photoreceptor of an embodiment can be manufactured.

[0134] The process of preparing a coating liquid containing an inorganic oxide filler surface-treated with a silane coupling agent may include a process of dispersing a charge generating material and the like in a solvent to prepare a coating liquid A, and a process of dispersing an inorganic oxide filler surface-treated with a silane coupling agent in coating liquid A to prepare a coating liquid B.

[0135] The solvent used in the formation of the photosensitive layer includes, for example, halogenated hydrocarbons such as dichloromethane, dichloroethane, chloroform, carbon tetrachloride, and chlorobenzene; ethers such as dimethyl ether, diethyl ether, tetrahydrofuran, dioxane, dioxolane, ethylene glycol dimethyl ether, and diethylene glycol dimethyl ether; ketones such as acetone, methyl ethyl ketone, and cyclohexanone, and the like can be appropriately selected from the viewpoints of the solubility, liquid stability, and coating properties of various materials.

[0136] Here, the type of solvent used for preparing the coating liquid, coating conditions, drying conditions, etc. can be appropriately selected according to a conventional method and are not particularly limited.

[0137] (Electronic Photographic Device)

[0138] The electronic photographic device of the embodiment of the present invention is a device equipped with the above-mentioned photosensitive body, and can obtain the desired effect by being applied to various machine processes. Specifically, sufficient effects can also be obtained in charging processes such as contact charging methods using charging components such as rollers or brushes, non-contact charging methods using charging components such as corotrons or corona devices, and contact development using developing methods (developers) such as non-magnetic one component, magnetic one component, and two components, and non-contact development methods.

[0139] The electronic photographic device according to the embodiment of the present invention is equipped with the above-mentioned electronic photographic photoreceptor, and can be made into an electronic photographic device for color printing in a tandem mode with a printing speed of 20 ppm or more. In addition, the electronic photographic device according to other embodiments of the present invention is equipped with the above-mentioned electronic photographic photoreceptor, and can be made into an electronic photographic device with a printing speed of 40 ppm or more. In devices that use the photoreceptor strictly, such as high-speed machines that require high charge transport performance in the photosensitive layer or tandem color machines where the influence of discharge gas is large, it is believed that space charge is easily accumulated in devices with short processing time. Ghost images are easily generated in such electronic photographic devices, so the application of the present invention is more useful. In particular, in electronic photographic devices for color printing in a tandem mode and electronic photographic devices that do not have a charge-removing component, ghost images are easily generated, so the application of the present invention is more useful.

[0140] Figure 3 , a simplified structural diagram of an example of a configuration of an electronic photographic device according to an embodiment of the present invention is shown. The electronic photographic device 60 of the present invention shown in the figure is equipped with a photosensitive body 7 including a conductive substrate 1, an undercoat layer 2 formed on the outer peripheral surface thereof, and a photosensitive layer 300. Moreover, the electronic photographic device 60 is provided with at least a charging member and a developer. The electronic photographic device 60 may include a charging device, an exposure device, a developing device, a paper guide device, a transfer device, and a cleaning device arranged at the outer peripheral edge of the photosensitive body 7. In the example shown in the figure, the electronic photographic device 60 is composed of a charging member 21, a charging device including a high-voltage power supply 22 for supplying voltage to the charging member 21, an exposure device including an image exposure member 23, a developer 24 as a developing device including a developing roller 241, a paper guide member 25 as a paper guide device including a paper guide roller 251 and a paper guide 252, and a transfer device including a transfer charger (direct charging type) 26. The electrophotographic device 60 may further include a cleaning device 27 including a cleaning blade 271, and a static eliminating member 28. In addition, the electrophotographic device 60 of the present invention may be a color printer.

[0141] Figure 4, a simplified structural diagram of another structural example of an electronic photographic device according to an embodiment of the present invention is shown. The electronic photographic process in the electronic photographic device shown in the figure represents a monochrome high-speed printer. The electronic photographic device 70 shown in the figure is equipped with a photosensitive body 8 including a conductive substrate 1, an undercoat layer 2 coated on its outer peripheral surface, and a photosensitive layer 300. In the photosensitive body 8 of this embodiment, the undercoat layer 2 is composed of a laminated structure of an aluminum oxide layer 2A and a resin layer 2B. The electronic photographic device 70 also includes a charging device, an exposure device, a developing device, a paper guide device, a transfer device, and a cleaning device arranged at the outer peripheral edge of the photosensitive body 8. In the example shown in the figure, the electronic photographic device 70 includes: a charging device including a charging member 31 and a power supply 32 for supplying an applied voltage to the charging member 31, an exposure device including an image exposure member 33, a developing device including a developing member 34, and a transfer device including a transfer member 35. The electronic photographic device 70 may also include a cleaning device including a cleaning member 36, and a paper guide device.

[0142] Example

[0143] The specific embodiments of the present invention are described in further detail below using examples. The present invention is not limited to the following examples within the scope of its technical content.

[0144] <Production Example of Positively Charged Single-layer Photoreceptor>

[0145] (Example 1)

[0146] As the conductive substrate, a tube made of aluminum and having a thickness of 0.75 mm and cut to a size of φ30 mm×length of 244.5 mm and having a surface roughness (Rmax) of 0.2 μm was used. The conductive substrate had an aluminum oxide layer on the surface.

[0147] (Single-layer photosensitive layer)

[0148] A single-layer photosensitive layer was formed according to the blending amounts shown in Table 1 below. A compound represented by the following structural formula (HT1) as a hole transport material, a compound represented by the above structural formula (A1) as a first electron transport material, a compound represented by the above structural formula (A2) as a second electron transport material, and a polycarbonate resin having a repeating unit represented by the above structural formula (B1) as a resin binder were dissolved in tetrahydrofuran, and after adding oxytitanium phthalocyanine represented by the following structural formula (CG1) as a charge generating material, a dispersion treatment was performed using a sand mill to prepare a coating liquid A. As an inorganic oxide filler surface-treated with a silane coupling agent, a surface-treated silica (YA010C, aluminum content 500 ppm) manufactured by Toyota Tsusho Corporation was prepared, which was surface-treated with a silane coupling agent represented by the above structural formula (C1). The surface-treated silica was mixed in the coating liquid A and dispersed to prepare a photosensitive layer coating liquid B in which the filler was dispersed. The coating liquid B was applied onto the conductive substrate by dip coating and dried at 100° C. for 60 minutes to form a single-layer photosensitive layer with a film thickness of about 25 μm, thereby obtaining a positively charged single-layer photoreceptor.

[0149]

[0150] (Examples 2 to 15 and Comparative Examples 1 to 9)

[0151] A single-layer photosensitive layer was formed in the same manner as in Example 1 except that the type and blending amount of each material were changed according to the conditions shown in Table 1 below, thereby obtaining positively charged single-layer photoreceptors of Examples 2 to 15 and Comparative Examples 1 to 9. The structural formulas of the materials used in Comparative Examples are shown below.

[0152]

[0153] <Production Example of Positively Charged Laminated Photoreceptor>

[0154] (Example 16)

[0155] As the conductive substrate, a tube made of aluminum and having a thickness of 0.75 mm and cut to a size of φ30 mm×length of 254.4 mm and having a surface roughness (Rmax) of 0.2 μm was used. The conductive substrate had an aluminum oxide layer on the surface.

[0156] (Charge transport layer)

[0157] The compound represented by the above structural formula (HT1) as a hole transport material and the polycarbonate resin having a repeating unit represented by the above structural formula (B1) as a resin binder were dissolved in tetrahydrofuran to prepare a coating liquid C. The coating liquid C was applied to the above conductive substrate by dip coating and dried at 100° C. for 30 minutes to form a charge transport layer with a film thickness of 10 μm. The content of the hole transport material and the resin binder relative to the solid content of the charge transport layer was 50.0% by mass, respectively.

[0158] (Charge Generation Layer)

[0159] A charge generating layer was formed according to the blending amounts shown in Table 2 below. The compound represented by the above structural formula (HT1) as a hole transport material, the compound represented by the above structural formula (A1) as a first electron transport material, the compound represented by the above structural formula (A2) as a second electron transport material, and a polycarbonate resin having a repeating unit represented by the above structural formula (B1) as a resin binder were dissolved in tetrahydrofuran, and after adding the oxytitanium phthalocyanine represented by the above structural formula (CG1) as a charge generating substance, a dispersion treatment was performed using a sand mill to prepare a coating liquid D. As an inorganic oxide filler surface-treated with a silane coupling agent, a surface-treated silica (YA010C, aluminum content 500 ppm) manufactured by Toyota Tsusho Corporation was prepared, which was surface-treated with a silane coupling agent represented by the above structural formula (C1). The surface-treated silica was mixed in the coating liquid D and dispersed to prepare a charge generating layer coating liquid E in which the surface-treated silica was dispersed. The coating solution E was applied on the charge transport layer by dip coating and dried at 110° C. for 30 minutes to form a charge generation layer with a thickness of 15 μm. A positively charged laminated photoreceptor having a photosensitive layer with a thickness of 25 μm was obtained.

[0160] (Examples 17 to 32 and Comparative Examples 10 to 20)

[0161] Positively charged laminated photoreceptors of Examples 17 to 32 and Comparative Examples 10 to 20 were obtained in the same manner as in Example 16 except that the types and blending amounts of the materials were changed and the charge generating layer was formed according to the conditions shown in Table 2 below.

[0162] Evaluation of positively charged single-layer photoreceptor

[0163] The single-layer photosensitive bodies of Examples 1 to 15 and Comparative Examples 1 to 9 were assembled into a commercially available printer HL5200DW manufactured by Brother Industries, Ltd., and the photosensitive bodies were evaluated under three environments: 10°C-20% (LL, low temperature and low humidity), 25°C-50% (NN, normal temperature and normal humidity), and 35°C-85% (HH, high temperature and high humidity). The results are shown in Table 3 below.

[0164] <Evaluation of Electrical Characteristics>

[0165] The electrical properties of the photoreceptors obtained in each example and comparative example were evaluated by the following method using a process simulator (CYNTHIA91) manufactured by Gene Technology Co., Ltd. The photoreceptors of Examples 1 to 15 and Comparative Examples 1 to 9 were charged to +650V by corona discharge in a dark place at a temperature of 22°C and a humidity of 50%, and the surface potential V0 immediately after the charging was measured. Then, after leaving the photoreceptors in a dark place for 5 seconds, the surface potential V5 was measured, and the potential retention rate Vk5 (%) after charging for 5 seconds was calculated according to the following calculation formula (1).

[0166] Vk5=V5 / V0×100 (1)

[0167] Next, a halogen lamp was used as a light source, and from the time when the surface potential reached +600 V, 1.0 μW / cm2 of light was irradiated to the photoreceptor using a filter with a spectral range of 780 nm. 2 The photosensitive body was exposed to light for 5 seconds, and the residual potential on the surface of the photoreceptor after exposure for 5 seconds was evaluated as Vr5 (V).

[0168] <Evaluation of Wear Resistance>

[0169] For the photoreceptors obtained in each example and comparative example, 10,000 sheets of A4 paper were printed, the film thickness of the photosensitive layer before and after printing was measured, and the average wear amount (μm) after printing was evaluated. The average wear amount is the value obtained by measuring the film thickness at four points, and averaging the values, the four points being four points obtained by rotating the position of the middle (130 mm from the end) of the long side direction of the photoreceptor by 90° in the circumferential direction.

[0170] <Evaluation of ghost images>

[0171] Printing in HH environment Figure 5 The interference fringe (1on2off) image shown was evaluated for the presence or absence of negative ghosting. The results were as follows: no ghosting was observed as ◎, a little ghosting was observed as ○, ghosting was observed as △, and ghosting was clearly observed as ×.

[0172] <Evaluation of Environmental Stability of Print Density>

[0173] In the three environments of LL, NN, and HH, a solid pattern of 25 mm x 25 mm square was formed on A4 paper, and the print density was measured using a Macbeth densitometer. The difference between the minimum and maximum print density in the three environments was calculated. The results were as follows: when the print density difference was less than 0.1, it was marked as ◎, when it was 0.1 or more and less than 0.2, it was marked as ○, when it was 0.2 or more and less than 0.4, it was marked as △, and when it was 0.4 or more, it was marked as ×.

[0174] Evaluation of positively charged laminated photoreceptor

[0175] The positively charged laminated photoreceptors of Examples 16 to 32 and Comparative Examples 10 to 20 were assembled into a commercially available printer HL3170CDW manufactured by Brother Industries, Ltd., and the photoreceptors were evaluated under three environments: 10°C-20% (LL, low temperature and low humidity), 25°C-50% (NN, normal temperature and normal humidity), and 35°C-85% (HH, high temperature and high humidity). The results are shown in Table 4 below.

[0176] <Evaluation of Electrical Characteristics>

[0177] The electrical properties of the photoreceptors obtained in each example and comparative example were evaluated by the following method using a process simulator (CYNTHIA91) manufactured by Gene Technology Co., Ltd. The photoreceptors of Examples 16 to 32 and Comparative Examples 10 to 20 were charged to +650V by corona discharge in a dark place at a temperature of 22°C and a humidity of 50%, and the surface potential V0 immediately after charging was measured. Then, after leaving it in a dark place for 5 seconds, the surface potential V5 was measured, and the potential retention rate Vk5 (%) after charging for 5 seconds was calculated according to the following calculation formula (1).

[0178] Vk5=V5 / V0×100 (1)

[0179] Next, a halogen lamp was used as a light source, and from the time when the surface potential reached +600 V, 1.0 μW / cm2 of light was irradiated to the photoreceptor using a filter with a spectral range of 780 nm. 2 The photosensitive body was exposed to light for 5 seconds, and the residual potential on the surface of the photoreceptor after exposure for 5 seconds was evaluated as Vr5 (V).

[0180] <Evaluation of Wear Resistance>

[0181] For the photoreceptors obtained in each example and comparative example, 10,000 sheets of A4 paper were printed, the film thickness of the photosensitive layer before and after printing was measured, and the average wear amount (μm) after printing was evaluated. The average wear amount is the value obtained by measuring the film thickness at four points, and averaging the values, the four points being four points obtained by rotating the position of the middle (130 mm from the end) of the long side direction of the photoreceptor by 90° in the circumferential direction.

[0182] <Evaluation of ghost images>

[0183] Printing in HH environment Figure 5 The interference fringe (1on2off) image shown was evaluated for the presence or absence of negative ghosting. The results were as follows: no ghosting was observed as ◎, a little ghosting was observed as ○, ghosting was observed as △, and ghosting was clearly observed as ×.

[0184] <Evaluation of Environmental Stability of Print Density>

[0185] In the three environments of LL, NN, and HH, a solid pattern of 25 mm x 25 mm square was formed on A4 paper, and the print density was measured using a Macbeth densitometer. The difference between the minimum and maximum print density in the three environments was calculated. The results were as follows: when the print density difference was less than 0.1, it was marked as ◎, when it was 0.1 or more and less than 0.2, it was marked as ○, when it was 0.2 or more and less than 0.4, it was marked as △, and when it was 0.4 or more, it was marked as ×.

[0186] [Table 1]

[0187]

[0188] [Table 2]

[0189]

[0190] [Table 3]

[0191]

[0192] [Table 4]

[0193]

[0194] As can be seen from the results in Tables 3 and 4, Examples 1 to 32, in which the photosensitive layer used a combination of two electron transport materials satisfying the above-mentioned Hansen solubility parameter conditions, a resin binder, and an inorganic oxide filler surface-treated with a silane coupling agent, compared with the photosensitive bodies of the comparative examples using different combinations, showed good wear resistance and good electrical characteristics as a photosensitive body, and suppressed the generation of ghost images. In addition, in each example, good results were obtained in terms of environmental stability of print density.

[0195] From the results of the embodiments, it can be seen that as the first electron transport material, the second electron transport material, the resin binder, the inorganic oxide filler and the silane coupling agent, it is particularly suitable to use naphthalenetetracarboxylic acid diimide compounds, azomethine compounds, bisphenol Z or bisphenol Z-biphenyl copolymers, silica particles and compounds represented by structural formulas C1, C2 and C4 respectively.

[0196] Explanation of symbols

[0197] 1 Conductive substrate

[0198] 2. Lower coating

[0199] 2A Aluminum oxide layer

[0200] 2B resin layer

[0201] 3 Single-layer photosensitive layer

[0202] 4 Charge transport layer

[0203] 5 Charge Generation Layer

[0204] 6 Laminated photosensitive layer

[0205] 7, 8 Photoreceptor

[0206] 21, 31 Live components

[0207] 22 High voltage power supply

[0208] 23,33 Image exposure components

[0209] 24 Developer

[0210] 241 Development Roller

[0211] 25 Paper guide

[0212] 251 Paper guide roller

[0213] 252 Paper Guide

[0214] 26 Transfer charger (direct charging type)

[0215] 27 Cleaning device

[0216] 271 Cleaning scraper

[0217] 28. Anti-static components

[0218] 32 Power Supply

[0219] 34 Development member

[0220] 35 Transfer component

[0221] 36 Cleaning components

[0222] 60,70 Electronic photography device

[0223] 300 Photosensitive layer

Claims

1. An electrophotographic photoreceptor comprising Conductive substrate, and The invention comprises a charge generating material, a hole transporting material, a first electron transporting material, a second electron transporting material, a resin binder, an inorganic oxide filler surface-treated with a silane coupling agent, and a photosensitive layer disposed on the conductive substrate. The first electron transport material has a structure represented by the following structural formula A1, A2 or A5, The second electron transport material has a structure represented by the following structural formula A2, A7, A8 or A11, The first electron transport material and the second electron transport material have different structures from each other, and the difference ΔSPa between the dipole force terms of the Hansen solubility parameters between the first electron transport material and the silane coupling agent satisfies the relationship of ΔSPa<2.

50. The difference ΔSPb between the dipole force terms of the Hansen solubility parameters between the second electron transport material and the silane coupling agent satisfies the relationship of ΔSPb<2.50, The difference ΔSPc between the dipole force terms of the Hansen solubility parameters of the first electron transport material and the second electron transport material satisfies the relationship of 0.30<ΔSPc<1.00, and, The difference ΔSPd between the London dispersion force term of the Hansen solubility parameter of the resin binder and the silane coupling agent satisfies the relationship of ΔSPd<2.00, and, The ratio of the content of the second electron transport material to the content of the first electron transport material and the second electron transport material is 3 mass % or more and 40 mass % or less.

2. The electrophotographic photoreceptor according to claim 1, wherein: The first electron transport material and the second electron transport material are compounds represented by the following structural formulas (A1) and (A2); 3. The electrophotographic photoreceptor according to claim 1 or 2, wherein: The primary particle size of the inorganic oxide filler is greater than or equal to 1 nm and less than or equal to 300 nm.

4. The electrophotographic photoreceptor according to claim 1 or 2, wherein: The photosensitive layer contains the charge generating material, the hole transporting material, the first electron transporting material, the second electron transporting material, the resin binder, and the inorganic oxide filler in a single layer.

5. The electrophotographic photoreceptor according to claim 4, wherein: In the solid content of the photosensitive layer, a content F of the inorganic oxide filler in mass % is less than a content E of the first electron transport material and the second electron transport material in mass %, and the content F satisfies the relationship of 2≤F≤15.

6. The electrophotographic photoreceptor according to claim 1 or 2, wherein: The photosensitive layer includes a charge transport layer and a charge generation layer sequentially stacked on the conductive substrate, and the charge generation layer includes the charge generation material, the hole transport material, the first electron transport material, the second electron transport material, the resin binder, and the inorganic oxide filler.

7. The electrophotographic photoreceptor according to claim 6, wherein: In the solid content of the charge generating layer, a content F of the inorganic oxide filler in mass % is less than a content E of the first electron transport material and the second electron transport material in mass %, and the content F satisfies the relationship of 2≤F≤15.

8. The electrophotographic photoreceptor according to claim 6, wherein: In the solid component of the charge generation layer, a content E of the first electron transport material and the second electron transport material in mass % is greater than a content H of the hole transport material in mass %, and the content E and the content H satisfy 1.5≤E / H≤10.

0.

9. A method for producing a photoreceptor for electrophotography, characterized in that: When manufacturing the electrophotographic photoreceptor according to claim 1, The method includes forming the photosensitive layer by dip coating.

10. An electronic photographic device, characterized in that: The electrophotographic photoreceptor according to claim 1 is mounted thereon.

Images