阅读说明：本技术 电子照相感光体、其制造方法以及电子照相装置 (Electrophotographic photoreceptor, method for producing the same, and electrophotographic apparatus ) 是由 竹内胜 小林广高 朱丰强 于 2019-01-25 设计创作，主要内容包括：本发明以低廉的价格提供在液体显影方式中具有足够的耐溶剂性和耐裂性、并且电特性也优良的电子照相感光体、其制造方法及电子照相装置。其是包括导电性基体(1)、依次设置在导电性基体上的电荷产生层(3)和电荷传输层(4)的电子照相感光体。电荷传输层含有作为粘合剂树脂的具有下述通式(1)表示的结构的共聚聚碳酸酯树脂,<Image he="123" wi="700" file="DDA0002601562350000011.GIF" imgContent="drawing" imgFormat="GIF" orientation="portrait" inline="no"></Image>并且含有作为空穴传输物质的具有下述通式(2)表示的结构的化合物。<Image he="419" wi="700" file="DDA0002601562350000012.GIF" imgContent="drawing" imgFormat="GIF" orientation="portrait" inline="no"></Image>(The invention provides an electrophotographic photoreceptor having sufficient solvent resistance and crack resistance in a liquid development system and excellent electrical characteristics, a method for manufacturing the same, and an electrophotographic apparatus at low cost. The electrophotographic photoreceptor comprises a conductive substrate (1), a charge generation layer (3) and a charge transport layer (4) which are sequentially provided on the conductive substrate. The charge transport layer contains a copolymerized polycarbonate resin having a structure represented by the following general formula (1) as a binder resin, and a compound having a structure represented by the following general formula (2) as a hole-transporting substance.)

1. An electrophotographic photoreceptor, comprising:

a conductive substrate,

An electrophotographic photoreceptor comprising a charge generation layer and a charge transport layer provided in this order on the conductive substrate,

the charge transport layer contains a copolymerized polycarbonate resin having a structure represented by the following general formula (1) as a binder resin,

in the formula (1), R₁～R₂The same or different, represent a hydrogen atom, an alkyl group having 1 to 10 carbon atoms or a fluoroalkyl group having 1 to 10 carbon atoms, m and n are numbers satisfying 0.4. ltoreq. n/(m + n) 0.6. ltoreq. the chain end group is a 1-valent aromatic group or a 1-valent fluorine-containing aliphatic group,

and a compound having a structure represented by the following general formula (2) as a hole-transporting substance,

in the formula (2), R₃～R₂₀The same or different, represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an aryl group or an aryl-substituted alkenyl group, and a represents an integer of 0 to 2.

2. The electrophotographic photoreceptor according to claim 1, wherein a mass ratio H/(B + H) representing a ratio of a mass (H) of the hole transporting substance in the charge transporting layer to a sum of a mass (B) of the binder resin and a mass (H) of the hole transporting substance satisfies the following formula (3),

H/(B + H) is more than or equal to 20 mass percent and less than or equal to 50 mass percent (3).

3. The electrophotographic photoreceptor according to claim 1, wherein the film thickness of the charge transport layer is 25 μm or less.

4. The electrophotographic photoreceptor of claim 1, wherein the charge generation layer contains Y-type oxytitanium phthalocyanine as a charge generation material.

5. The electrophotographic photoreceptor according to claim 1, wherein the electrical characteristic test apparatus for the photoreceptor is used to measure the moving time of the probe from exposure to potential at an initial static potential of-1000V, the exposure light wavelength of 650nm, and the exposure amount of 1.0 μ J/cm²Initial sensitivity V measured under the conditions of (1)_LThe absolute value of (-V) is 80 or less.

6. The electrophotographic photoreceptor according to claim 1, wherein a elution amount of the hole-transporting material from the charge-transporting layer when the electrophotographic photoreceptor is immersed in a hydrocarbon solvent contained in a liquid developer at room temperature for 100 hours is5 × 10^-8g/cm³The following.

7. A method for producing an electrophotographic photoreceptor, comprising the step of forming the charge generating layer and the charge transporting layer by a dip coating method in producing the electrophotographic photoreceptor according to claim 1.

8. An electrophotographic apparatus, comprising: an electrophotographic photoreceptor according to claim 1; a charging device for charging the electrophotographic photoreceptor; an exposure device for exposing the charged electrophotographic photoreceptor to form an electrostatic latent image on the surface; a developing device for forming a toner image by developing the electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a liquid developer in which a toner is dispersed in a hydrocarbon solvent; a transfer device for transferring the toner image formed on the surface of the electrophotographic photoreceptor to a recording medium.

Technical Field

The present invention relates to an electrophotographic photoreceptor (hereinafter, also simply referred to as "photoreceptor") used in a copying machine, a printer, and the like of an electrophotographic system, a method for producing the same, and an electrophotographic apparatus, and more particularly, to a negatively charged laminated electrophotographic photoreceptor for liquid development, which has excellent solvent resistance and good electrical characteristics, by containing a specific binder resin and a hole transport material in a charge transport layer, a method for producing the same, and an electrophotographic apparatus of a liquid development system.

Background

In the electrophotographic process, as development methods for visualizing an electrostatic latent image on a photoreceptor, there are roughly a dry development method using a powder toner and a liquid development method using a liquid developer in which a toner is dispersed in an insulating liquid. In general office use, a dry developing system apparatus is mainly used. On the other hand, in the liquid development system, since a toner (particle diameter: 0.1 to 2 μm) having a smaller particle diameter than that of the powder toner (particle diameter: 5 to 8 μm) can be used and a higher resolution can be achieved than in the dry development system, the liquid development system device has advantages of obtaining a high image quality close to offset printing and coping with high speed, and is increasingly used in a new commercial printing system such as on-demand printing (japanese: オンデマンド printing) as a substitute for offset printing.

On the other hand, as for photoreceptors which are the core of the electrophotographic process, inorganic photoreceptors using inorganic photoconductive materials such as selenium and selenium alloys, zinc oxide, and cadmium sulfide have been mainly used in the past, but recently, development of organic photoreceptors using organic photoconductive materials has been actively conducted by taking advantage of the advantages such as non-pollution, film-forming properties, and lightweight properties. Among them, in a so-called functional separation laminated organic photoreceptor including a photosensitive layer in which a charge generation layer and a charge transport layer having separated functions are laminated, since each layer is formed of a material suitable for each function, there are many advantages such as easy controllability of characteristics, and the like, and the organic photoreceptor becomes a mainstream organic photoreceptor. The charge generation layer mainly functions as a layer that generates charges when receiving light, and the charge transport layer mainly functions as a layer that holds an electrostatic potential in a dark place and transports charges when receiving light.

When such an organic photoreceptor is used in a liquid development system, the solvent resistance of the photosensitive layer to an organic solvent contained in a liquid developer is important. Since high insulation is required as a solvent for a liquid developer, hydrocarbon solvents such as isoparaffin are often used. If such a hydrocarbon solvent is brought into contact with the photoreceptor for a long time, the charge transport material contained in the charge transport layer may be eluted into the liquid developer, causing various problems. That is, there are cases where the charge transport ability and sensitivity are reduced due to elution of the charge transport material, and there are cases where cracking (cracking) or the like occurs due to internal stress and swelling of the binder resin by the hydrocarbon solvent, resulting in reduction in durability.

In order to solve this problem, for example, patent document 1 proposes forming a surface protective layer made of a thermosetting resin on the surface of a photoreceptor to prevent the charge transport agent from dissolving into a liquid developer. However, in such a photoreceptor, a side effect of sensitivity reduction and a new problem of high manufacturing cost are caused by newly providing a surface protective layer.

Patent document 2 proposes that the crack resistance in a liquid developing system is improved by using a specific polyarylate resin in the photosensitive layer, but although some improvement is confirmed, the crack resistance is insufficient and the electrical characteristics are poor, and thus the practical performance is not sufficient.

Patent document 3 proposes to improve crack resistance and the like by using a polycarbonate resin having an inorganic value/organic value (I/O value) of 0.37 or more, particularly in the range of 0.37 to 0.45, as a binder resin for a charge transport layer and by adjusting the molecular weight of a hole transport agent to 900 or more, particularly in the range of 900 to 1547.1. However, even in such a photoreceptor, the effect of preventing the dissolution of the charge transport agent into the liquid developer is insufficient, and the crack resistance cannot be said to be sufficient.

Patent document 4 discloses a specific triphenylamine derivative, a charge transport material using the triphenylamine derivative, and an electrophotographic photoreceptor, and patent document 5 discloses an electrophotographic photoreceptor in which a specific binder resin, a hole transport material, an electron transport material, and an antioxidant are used in a charge transport layer, and the mass ratio of the hole transport material in the charge transport layer is specified.

Disclosure of Invention

Technical problem to be solved by the invention

The present invention has been made in view of the above-described circumstances, and an object thereof is to provide an electrophotographic photoreceptor which can be mounted on a liquid developing system, has sufficient solvent resistance and crack resistance to hydrocarbon solvents, and has excellent electrical characteristics, a method for producing the electrophotographic photoreceptor, and an electrophotographic apparatus, at low cost.

Technical scheme for solving technical problem

The present inventors have conducted extensive studies to solve the above problems, and as a result, have found that solvent resistance and crack resistance can be improved while maintaining excellent sensitivity characteristics by incorporating a specific binder resin and a hole transporting substance in a charge transporting layer of an electrophotographic photoreceptor, thereby completing the present invention.

That is, the first aspect of the present invention is an electrophotographic photoreceptor comprising a conductive substrate, a charge generation layer and a charge transport layer provided in this order on the conductive substrate,

the charge transport layer contains a copolymerized polycarbonate resin having a structure represented by the following general formula (1) as a binder resin,

(in the formula (1), R₁～R₂The same or different, represent a hydrogen atom, an alkyl group having 1 to 10 carbon atoms or a fluoroalkyl group having 1 to 10 carbon atoms, m and n are numbers satisfying 0.4. ltoreq. n/(m + n) of 0.6 or less, and a chain end group is a 1-valent aromatic group or a 1-valent fluorine-containing aliphatic group)

And a compound having a structure represented by the following general formula (2) as a hole-transporting substance,

(in the formula (2), R₃～R₂₀The same or different, represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an aryl group or an aryl-substituted alkenyl group, and a represents an integer of 0 to 2).

Here, the mass ratio H/(B + H) indicating the ratio of the mass (H) of the hole-transporting substance in the charge transport layer to the sum of the mass (B) of the binder resin and the mass (H) of the hole-transporting substance preferably satisfies the following formula (3).

H/(B + H) is not less than 20% by mass and not more than 50% by mass (3)

The film thickness of the charge transport layer is preferably 25 μm or less. In addition, the charge generation layer preferably contains Y-type oxytitanium phthalocyanine as a charge generation material.

The photoreceptor was measured at an initial electrostatic potential of-1000V, a moving time from exposure to potential of 0.03s, and an exposure light wavelength using an electrical characteristic testing apparatus for the photoreceptor650nm, exposure 1.0 muJ/cm²Initial sensitivity V measured under the conditions of (1)_LThe absolute value of the (-V) is preferably 80 or less, and the amount of elution of the hole-transporting material from the charge-transporting layer when the electrophotographic photoreceptor is immersed in a hydrocarbon solvent contained in a liquid developer at room temperature for 100 hours is preferably 5 × 10^-8g/cm³The following.

In addition, a second aspect of the present invention is a method for manufacturing an electrophotographic photoreceptor, including a step of forming the charge generation layer and the charge transport layer by a dip coating method in manufacturing the electrophotographic photoreceptor.

In addition, a third aspect of the present invention is an electrophotographic apparatus comprising: the electrophotographic photoreceptor; a charging device for charging the electrophotographic photoreceptor; an exposure device for exposing the charged electrophotographic photoreceptor to form an electrostatic latent image on the surface; a developing device for forming a toner image by developing the electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a liquid developer in which a toner is dispersed in a hydrocarbon solvent; a transfer device for transferring the toner image formed on the surface of the electrophotographic photoreceptor to a recording medium.

Effects of the invention

According to the present invention, the electrophotographic photoreceptor having excellent sensitivity characteristics, a small amount of elution of a hole transporting substance even when contacted with a hydrocarbon solvent used as a developer for liquid development, and excellent solvent resistance and crack resistance, a method for producing the electrophotographic photoreceptor, and an electrophotographic apparatus can be provided by the above-described configuration.

Drawings

Fig. 1 is a schematic cross-sectional view showing an example of the electrophotographic photoreceptor of the present invention.

Fig. 2 is a schematic configuration diagram showing an example of an electrophotographic apparatus of the present invention.

Detailed Description

Embodiments of the electrophotographic photoreceptor of the present invention will be described in detail below with reference to the drawings.

Fig. 1 is a schematic cross-sectional view showing an example of the electrophotographic photoreceptor of the present invention. The photoreceptor shown in the figure is an electrophotographic photoreceptor including a conductive substrate 1, a charge generation layer 3 and a charge transport layer 4 provided in this order on the conductive substrate 1. In the electrophotographic photoreceptor, a charge generation layer 3 and a charge transport layer 4 are provided on a conductive substrate 1 via an intermediate layer 2. The intermediate layer is provided as needed, and the charge generation layer 3 and the charge transport layer 4 may be provided directly on the conductive substrate 1. The electrophotographic photoreceptor may be a negatively charged laminated photoreceptor applied to a negatively charged process.

(conductive substrate)

The conductive substrate 1 functions as an electrode of the photoreceptor and also serves as a support for other layers, and may be any of cylindrical, plate-like, and film-like, and is generally cylindrical. As the material of the conductive substrate 1, a known aluminum alloy such as JIS3003 system, JIS5000 system, JIS6000 system, etc., a metal such as stainless steel, nickel, etc., or a material obtained by applying a conductive treatment to glass, resin, etc., is used.

When the conductive substrate 1 is made of an aluminum alloy, it can be finished to a substrate with a predetermined dimensional accuracy by extrusion or drawing, or by injection molding when it is made of a resin material. Further, the surface of the base body may be processed to have an appropriate surface roughness by cutting with a diamond turning tool or the like as necessary. Then, the surface of the substrate can be cleaned by degreasing and washing with an aqueous detergent such as a weakly alkaline detergent.

The intermediate layer 2 may be provided as needed on the surface of the conductive substrate 1 cleaned as described above.

(intermediate layer)

The intermediate layer 2 is composed of a layer containing a resin as a main component, an oxide film such as an aluminum oxide film, or the like, and is provided as necessary for the purpose of preventing injection of unnecessary electric charges from the conductive substrate 1 into the charge generation layer 3, covering defects on the substrate surface, improving adhesiveness of the charge generation layer, or the like.

As the resin material forming the intermediate layer 2, one of a polycarbonate resin, a polyester resin, a polyvinyl acetal resin, a polyvinyl butyral resin, a polyvinyl alcohol resin, a vinyl chloride resin, a vinyl acetate resin, polyethylene, polypropylene, an acrylic resin, a polyurethane resin, an epoxy resin, a melamine resin, a silicone resin, a polyamide resin, a polystyrene resin, a polyacetal resin, a polyarylate resin, a polysulfone resin, a polymer of a methacrylate, a copolymer thereof, and the like can be used, or two or more of them can be used in an appropriate combination. Further, the same kind of resins having different molecular weights may be used in combination.

The resin material may contain fine particles of a metal oxide such as silicon oxide, titanium oxide, zinc oxide, calcium oxide, aluminum oxide, or zirconium oxide, fine particles of a metal sulfate such as barium sulfate or calcium sulfate, fine particles of a metal nitride such as silicon nitride or aluminum nitride, an organometallic compound, a silane coupling agent, a product of an organometallic compound and a silane coupling agent, or the like. Their content may be arbitrarily set within a range capable of forming a layer.

In the case of the intermediate layer 2 mainly composed of a resin, a hole transporting substance and an electron transporting substance may be contained for the purpose of imparting charge transportability, reducing charge traps, and the like. As such a hole transporting substance and an electron transporting substance, the same substances as those used in the charge transport layer 4 described below can be used. The content of the hole-transporting substance and the electron-transporting substance is preferably 0.1 to 60% by mass, more preferably 5 to 40% by mass, based on the solid content of the intermediate layer 2.

Further, other known additives may be contained in the intermediate layer 2 as necessary within a range not significantly impairing the electrophotographic characteristics.

One layer may be used as the intermediate layer 2, but two or more different kinds of layers may be stacked and used. The thickness of the intermediate layer 2 is also determined by the formulation composition of the intermediate layer 2, and can be arbitrarily set within a range in which adverse effects such as increase in residual potential do not occur when the intermediate layer is repeatedly used continuously, and is preferably 0.1 to 10 μm.

(Charge generation layer)

The charge generation layer 3 is provided on the conductive substrate 1 or the intermediate layer 2. The charge generation layer 3 is formed by a method such as coating a coating solution in which particles of a charge generation material are dispersed in a binder resin, and the charge generation layer 3 generates a charge upon receiving light. It is desirable that the charge generation layer 3 has high charge generation efficiency and charges are easily injected into the charge transport layer 4.

The charge generating material is not particularly limited as long as it has optical sensitivity to the wavelength of the exposure light source, and organic pigments such as phthalocyanine pigments, azo pigments, quinacridone pigments, indigo pigments, perylene pigments, polycyclic quinone pigments, anthrone pigments, benzimidazole pigments, and the like can be used, for example. The charge generation layer 3 preferably contains Y-type oxytitanium phthalocyanine as a charge generation material. By using Y-type oxytitanium phthalocyanine as a charge generating material in the charge generating layer 3, an electrophotographic photoreceptor more excellent in sensitivity characteristics, electrical characteristics, stability and the like can be provided in the case of using a hole transporting material and an electron transporting material in combination.

The charge generation layer 3 may be formed by: the charge generating material is dispersed or dissolved in a binder resin such as a polyester resin, a polyvinyl acetate resin, a polymethacrylate resin, a polycarbonate resin, a polyvinyl butyral resin, or a phenoxy resin, and a coating liquid prepared therefrom is applied to the conductive substrate 1 or the intermediate layer 2.

The content of the charge generating material in the charge generating layer 3 is preferably 20 to 80% by mass, and more preferably 30 to 70% by mass, based on the solid content in the charge generating layer 3. The content of the binder resin in the charge generation layer 3 is preferably 20 to 80% by mass, and more preferably 30 to 70% by mass, based on the solid content in the charge generation layer 3. The thickness of the charge generation layer 3 may be usually 0.1 to 0.6. mu.m.

By providing the charge transport layer 4 on the charge generation layer 3, a photoreceptor can be obtained.

(Charge transport layer)

The charge transport layer 4 contains at least a copolymerized polycarbonate resin having a structure represented by the above general formula (1) as a binder resin and a compound having a structure represented by the above general formula (2) as a hole transport substance. Since the copolymerized polycarbonate resin having the structure represented by the above general formula (1) has high toughness, by using it as a binder resin, an effect that cracking is not easily caused even if internal stress is generated in the charge transport layer 4 can be obtained. Further, the compound having the structure represented by the above general formula (2) has a feature of being hardly dissolved out even when immersed in a hydrocarbon solvent for a long period of time. Therefore, by using the above-described specific combination as the binder resin and the hole-transporting substance used in the charge transport layer 4, even when the charge transport layer 4 is in contact with a hydrocarbon solvent used as a developer for liquid development for a long time, elution of the hole-transporting substance from the charge transport layer 4 into the solvent can be suppressed. By the composition of the charge transport layer, an electrophotographic photoreceptor having excellent solvent resistance and crack resistance and excellent sensitivity characteristics can be realized at low cost. Further, it is not necessary to provide a surface protective layer in order to avoid contact between the charge transport layer and the solvent.

Specific examples of the copolymerized polycarbonate resin having the structure represented by the general formula (1) which constitutes the binder resin of the charge transport layer 4 include, but are not limited to, the copolymerized polycarbonate resins described below.

The ratio of m to n is preferably 0.4. ltoreq. n/(m + n). ltoreq.0.6, and the chain end group is preferably a 1-valent aromatic group or a 1-valent fluorine-containing aliphatic group.

As the binder resin of the charge transport layer 4, the copolymerized polycarbonate resin represented by the above general formula (1) must be used, but if necessary, other known resins may be used as long as the effects of the present invention are not significantly impaired.

As another resin that can be used as the binder resin of the charge transport layer 4, for example, one of a polycarbonate resin other than the copolymerized polycarbonate resin represented by the above general formula (1), a polyarylate resin, a polyester resin, a polyvinyl acetal resin, a polyvinyl butyral resin, a polyvinyl alcohol resin, a vinyl chloride resin, a vinyl acetate resin, a polyethylene resin, a polypropylene resin, a polystyrene resin, a thermoplastic resin such as an acrylic resin, a polyamide resin, a ketone resin, a polyacetal resin, a polysulfone resin, and a polymer of methacrylic acid ester, a thermosetting resin such as an alkyd resin, an epoxy resin, a silicone resin, a urea resin, a phenol resin, an unsaturated polyester resin, a polyurethane resin, and a melamine resin, and a copolymer thereof, or two or more of them may be used in an appropriate combination. In addition, in the binder resin of the charge transport layer 4, the ratio of the inorganic value to the organic value (I/O value) may be less than 0.37.

Specific examples of the compound having a structure represented by the above general formula (2) which constitutes the hole transport material of the charge transport layer 4 include the following compounds, but are not limited thereto.

The compound having a structure represented by the above general formula (2) can be produced, for example, by the method described in international publication No. 2017/138566.

In the charge transport layer 4, other known hole transport substances may be used as needed within a range not significantly impairing the effects of the present invention. Examples of the other known hole-transporting substances include hydrazone compounds, pyrazoline compounds, pyrazolone compounds, and the like,An oxadiazole compound,

One kind of the azole compound, the arylamine compound, the benzidine compound, the stilbene compound, the styryl compound, the enamine compound, the butadiene compound, the polyvinylcarbazole, the polysilane, or the like may be used, or two or more kinds of them may be used in appropriate combination.

Here, in the charge transport layer 4, the mass ratio H/(B + H) of the ratio of the mass (H) of the hole-transporting substance to the sum of the mass (B) of the binder resin and the mass (H) of the hole-transporting substance preferably satisfies the following formula (3).

H/(B + H) is not less than 20% by mass and not more than 50% by mass (3)

Thereby, high solvent resistance can be achieved while maintaining appropriate sensitivity characteristics. This is because, since the charge mobility of the hole-transporting substance represented by the above general formula (2) is large, even in the case of using a small amount of the hole-transporting substance satisfying the above formula (3), excellent sensitivity characteristics can be obtained. Further, since the amount of the hole-transporting substance can be reduced, the elution amount of the hole-transporting substance into a hydrocarbon solvent used as a liquid developer can be suppressed, and thus, from the results, an electrophotographic photoreceptor excellent in solvent resistance and crack resistance can be provided.

In addition, for the purpose of reducing the residual potential and improving the sensitivity characteristics by efficiently transporting electrons accumulated in the charge transport layer 4, an electron transport material may be contained in the charge transport layer 4 within a range in which the effects of the present invention are not significantly impaired.

Specific examples of the electron-transporting substance that can be used in the charge transport layer 4 include, but are not limited to, compounds having the structures represented by the following formulas (E-1) to (E-6).

In addition, a conventionally known electron-transporting substance may be used in combination. Examples of the electron-transporting substance (acceptor compound) include succinic anhydride, maleic anhydride, dibromosuccinic anhydride, phthalic anhydride, 3-nitrophthalic anhydride, 4-nitrophthalic anhydride, pyromellitic acid, trimellitic anhydride, phthalimide, 4-nitrophthalimide, tetracyanoethylene, tetracyanoquinodimethane, tetrachlorobenzoquinone, tetrabromobenzoquinone, o-nitrobenzoic acid, malononitrile, trinitrofluorenone, trinitrothioxanthone, dinitrobenzene, dinitroanthracene, dinitroacridine, nitroanthraquinone, dinitroanthraquinone, thiopyran compound, quinone compound, benzoquinone compound, diphenoquinone compound, naphthoquinone compound, azo quinone compound, anthraquinone compound, diiminoquinone compound, One of these compounds may be used, or two or more thereof may be used in appropriate combination.

The charge transport layer 4 may contain a conventionally known deterioration preventing agent such as an antioxidant, a radical scavenger, a singlet quencher, and an ultraviolet absorber, within a range not significantly impairing the effect of the present invention, for the purpose of improving weather resistance and stability against harmful light.

Examples of such a compound include chromanol derivatives such as tocopherol, esterified compounds, polyarylalkane compounds, hydroquinone derivatives, etherified compounds, diethoxylated compounds, benzophenone derivatives, benzotriazole derivatives, thioether compounds, phenylenediamine derivatives, phosphonate esters, phosphite esters, phenol compounds, hindered phenol compounds, linear amine compounds, cyclic amine compounds, hindered amine compounds, biphenyl derivatives, and the like.

The charge transport layer 4 may further contain a leveling agent such as silicone oil or fluorine-based oil for the purpose of improving the leveling property of the formed film and imparting lubricity.

The charge transport layer 4 may contain fine particles of a metal oxide such as silicon oxide (silicon dioxide), titanium oxide, zinc oxide, calcium oxide, aluminum oxide (aluminum oxide), or zirconium oxide, a metal sulfate such as barium sulfate or calcium sulfate, a metal nitride such as silicon nitride or aluminum nitride, fluorine-based resin particles such as tetrafluoroethylene resin, or a fluorine-based comb graft polymer resin for the purpose of reducing the friction coefficient, imparting lubricity, or the like.

The content of the binder resin in the charge generation layer 4 is preferably 20 to 90% by mass, and more preferably 30 to 80% by mass, based on the solid content of the charge transport layer 4. The total content of the hole transport material and the optional electron transport material in the charge transport layer 4 is preferably 10 to 80 mass%, more preferably 20 to 70 mass%, based on the solid content of the charge transport layer 4.

The thickness of the charge transport layer 4 is preferably 25 μm or less, more preferably 5 to 25 μm, and still more preferably 10 to 25 μm. The charge transport layer 4 having such a thickness can realize good coatability, uniformity of film thickness, and high resolution while maintaining a practically effective surface potential.

In the photoreceptor according to the embodiment of the present invention, the hole transport material represented by the general formula (2) has excellent compatibility with the binder resin represented by the general formula (1), and also has high charge mobility and high injection efficiency from the charge generating material, and therefore, the charge transport layer 4 has excellent durability and sensitivity characteristics even if it is a thin film. The electrophotographic photoreceptor including the charge transport layer 4 is a high-sensitivity photoreceptor as follows: an electric characteristic test device for a photoreceptor is used to measure the moving time of a probe from exposure to potential of 0.03s, the wavelength of exposure light of 650nm and the exposure amount of 1.0 muJ/cm at an initial static potential of-1000V²Initial sensitivity V measured under the conditions of (1)_LThe absolute value of (-V) is preferably 80 or less. The initial sensitivity V_LThe absolute value of (a) is preferably 70 or less, more preferably 60 or less.

Further, according to the photoreceptor of the embodiment of the present invention, when the photoreceptor is immersed in a hydrocarbon solvent contained in a developer for liquid development at room temperature for 100 hours, the elution amount of a hole transport material from a charge transport layer can be 5 × 10^-8g/cm³Here, as the hydrocarbon solvent contained in the developer for liquid development, for example, ISOPAR L (manufactured by Exxon Mobil, Inc. (エクソンモービル)) which is an isoalkane hydrocarbon can be mentioned, and the amount of elution of the hole-transporting substance is preferably 4 × 10^-8g/cm³The following.

The photoreceptor according to the embodiment of the present invention has the effects of being excellent in solvent resistance and cracking resistance and also excellent in sensitivity characteristics when used in an electrophotographic apparatus for liquid development, and therefore is useful as an electrophotographic photoreceptor for liquid development, and is particularly suitable as a negatively charged laminated electrophotographic photoreceptor for liquid development.

[ method for producing electrophotographic photoreceptor ]

The manufacturing method according to an embodiment of the present invention includes a step of forming the charge generation layer and the charge transport layer by a dip coating method in manufacturing the photoreceptor. By using the dip coating method, a photoreceptor having good appearance quality and stable electrical characteristics can be manufactured at low cost while ensuring high productivity. In the production of the photoreceptor, the points other than the point of using the dip coating method are not particularly limited, and the production can be carried out by a conventional method. The manufacturing method may further include a step of preparing a conductive substrate, and a step of dip-coating the charge generation layer and the charge transport layer in this order on the conductive substrate.

Specifically, first, an arbitrary charge generating material and an arbitrary binder resin or the like are dissolved and dispersed in a solvent to prepare a coating liquid for forming a charge generating layer, and the coating liquid for the charge generating layer is applied to the outer periphery of a conductive substrate via an intermediate layer as necessary, and dried to form the charge generating layer. Next, the predetermined binder resin and the hole transport material, and an optional electron transport material and additives are dissolved in a solvent to prepare a coating liquid for forming a charge transport layer, and the coating liquid for the charge transport layer is applied onto the charge generation layer and dried to form a charge generation layer, thereby forming a photoreceptor. Here, the kind of the solvent used for the preparation of the coating liquid, the coating conditions, the drying conditions, and the like may be appropriately selected according to a conventional method, and are not particularly limited.

[ electrophotographic apparatus ]

An electrophotographic apparatus of an embodiment of the present invention includes: the photoreceptor; a charging device for charging the photoreceptor; an exposure device for exposing the charged photoreceptor to form an electrostatic latent image on the surface; a developing device for forming a toner image by developing the electrostatic latent image formed on the surface of the photoreceptor with a liquid developer in which a toner is dispersed in a hydrocarbon solvent; and a transfer device for transferring the toner image formed on the surface of the photoreceptor to a recording medium. An electrophotographic device for liquid development having excellent durability can be provided by providing an electrophotographic photoreceptor having a small amount of elution of a hole transporting material, excellent solvent resistance and cracking resistance, and excellent sensitivity characteristics even when immersed in a hydrocarbon solvent used as a liquid developer for a long period of time. The electrophotographic apparatus may further include a fixing device for fixing the toner image transferred to the recording medium.

Fig. 2 is a schematic configuration diagram showing an example of an electrophotographic apparatus of the present invention. The illustrated electrophotographic apparatus includes: a charging roller 12 as a charging device disposed at an outer peripheral edge portion of the electrophotographic photoreceptor 11, an exposure light source 13 as an exposure device, a liquid developer 14 as a developing device including a developing roller 14a and a liquid developer 14b, a transfer device 15 as a transfer device, and a fixing roller 17 as a fixing device; can be used as a color printer. In the figure, the transfer material 16 may be a recording medium such as paper. In the figure, reference numeral 18 denotes a cleaning blade, and 19 denotes a light source for charge removal.