JPH10221875A - Photoreceptor for liquid development and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the photoreceptor for liquid development small in occurrences of image quality defects due to cracking and abrasion and the like on the surface of the photosensitive layer even in the case of repeating developments using the liquid developer for a long period. SOLUTION: This photoreceptor for liquid development is provided on a conductive substrate with the photosensitive layer and a surface protective layer and this protective layer is formed by an network polymer obtained by combining a compound having a hydroxyl group with a compound having an isocyanate group, and at least one of the compounds each having a hydroxyl group is a charge transfer material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photosensitive member for liquid development having a surface protective layer containing a charge transporting material, and
The present invention relates to an image forming method using the photoconductor.

[0002]

2. Description of the Related Art In recent years, electrophotographic technology has been widely used in the fields of copiers, laser beam printers, facsimile machines, and the like, because high speed and high printing quality can be obtained. Electrophotographic photoreceptors used in these electrophotographic techniques have conventionally been selenium, selenium-tellurium alloy,
Those using inorganic photoconductive materials such as selenium-arsenic alloy and cadmium sulfide are widely known.

On the other hand, studies on electrophotographic photoreceptors using organic photoconductive materials, which are inexpensive and have excellent advantages in terms of manufacturability and disposability as compared with electrophotographic photoreceptors using these inorganic photoconductive materials, have also been made. It is becoming active. Above all, a function-separated organic layered photoconductor in which a charge generation layer that generates charges by exposure and a charge transport layer that transports charges is laminated has sensitivity, chargeability,
Further, it is excellent in electrophotographic properties such as its repetition stability, and various proposals have been made and put to practical use.

On the other hand, at present, a single-layer type organic photoreceptor has system advantages (reducing ozone generation and uniform charging) in terms of manufacturability, manufacturing cost, and positive chargeability. However, there is a problem that the electrical performance is inferior to that of the laminated photoreceptor, and there is still room for research and development.

An electrophotographic developer for developing a latent image formed on a photoreceptor as described above includes a dry powder developer, which is generally widely used, and toner particles dispersed in a liquid. Wet liquid developers are known. Recently, due to the demand for colorization and high image quality, the latter liquid developer that can use toner particles having a smaller particle size has attracted attention.

However, when a liquid developer is applied to an electrophotographic photoreceptor having a charge transport layer in which a conventionally proposed general charge transport material is molecularly dispersed in a binder resin, the charge transport property is reduced. There are problems that the material elutes, the binder resin swells and cracks occur, the mechanical strength is reduced, the electrophotographic properties are reduced, and the performance of the photoreceptor is lost from the initial stage. .

In order to improve these drawbacks, a charge transporting polymer compound, 2-methoxy-9,10-
Photoreceptors for liquid development using a polyester obtained from a dicarboxylic acid mainly containing anthracenediol for a charge transport layer have been proposed (JP-A-58-102946 and JP-A-58-102947).

However, when these charge transporting high molecular compounds are used as a photosensitive layer in combination with a liquid developer,
Although good characteristics can be obtained at an early stage, they have not yet had sufficient characteristics in the long term. That is, the photosensitive layer formed using these charge-transporting polymer compounds is brought into contact with a liquid developer in a copying machine, and when used repeatedly for a long time, the components of the photosensitive layer are locally changed to the liquid developer. The solvent elutes or swells, which in turn causes cracks.As a result, image quality defects occur, the surface of the photosensitive layer is worn away, the thickness of the photoreceptor changes, the charging potential decreases, and the sensitivity decreases. Changes. Further, fogging occurs in the copy, or the copy density decreases. Furthermore, surface wear scratches on the photoconductor,
There is also a problem that an image quality defect occurs due to toner filming or the like.

[0009]

SUMMARY OF THE INVENTION Accordingly, the present invention has been made to solve the above-mentioned problems, and has been found to provide an image quality defect due to cracks and a defect due to surface wear of a photosensitive layer even after repeated development with a liquid developer for a long period of time. It is an object of the present invention to provide a photoconductor for liquid development in which the occurrence of the like is difficult to occur and an image forming method using the photoconductor.

[0010]

Means for Solving the Problems The present inventors have conducted intensive studies on the material of the surface protective layer in order to solve such problems, and as a result, using a specific material, The present inventors have found that the electrical characteristics and the image quality maintenance can be maintained even in long-term contact and repeated development, and have completed the present invention. The configuration of the present invention is as follows.

(1) In a photoconductor for liquid development comprising a photosensitive layer and a surface protective layer provided on a conductive support, the surface protective layer comprises a compound having a hydroxy group and a compound having a plurality of isocyanate groups. A photoreceptor for liquid development, wherein the photoreceptor comprises a compound having a network structure by bonding, and at least one of the compounds having a hydroxy group is a charge transporting material.

(2) The compound having a hydroxy group is
The photoconductor for liquid development according to the above (1), further comprising a charge transporting material having at least one hydroxy group and a binder having at least two hydroxy groups.

(3) The above (1) or (2), wherein at least one of the charge transporting materials having a hydroxy group is one represented by the following structural formulas (A) to (C).
The photoconductor for liquid development according to the above.

[0014]

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(Wherein R ₁ , R ₂ and R ₃ are a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or 1 to 5 carbon atoms) Represents an amino group substituted with an alkyl group in the range of 2, T represents an aliphatic portion and may be a branched divalent hydrocarbon group having 1 to 10 carbon atoms, and n is 0 or 1.)

[0016]

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(R ₄ is a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkyl group having 1 to 5 carbon atoms substituted by a halogen atom, an alkoxy group having 1 to 5 carbon atoms, A group, a phenyl group, or a halogen atom as a substituent, an alkyl group having 1 to 5 carbon atoms, an alkyl group having 1 to 5 carbon atoms substituted with a halogen atom, or a alkyl group having 1 to 5 carbon atoms. Represents a phenyl group containing an alkoxy group, T is a divalent hydrocarbon group which may be branched and has 1 to 10 carbon atoms in an aliphatic portion, and n is 0 or 1.
It is. )

[0018]

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(R ₅ is hydrogen or an alkyl group having 1 to 5 carbon atoms, X is hydrogen, an alkyl group having 1 to 5 carbon atoms, a phenyl group, or a halogen atom as a substituent;
C represents an alkyl group having 1 to 5 carbon atoms, an alkyl group having 1 to 5 carbon atoms substituted with a halogen atom, or a phenyl group containing an alkoxy group having 1 to 5 carbon atoms; The group represents a divalent hydrocarbon group having 1 to 10 carbon atoms which may be branched, and Ar ₁ , Ar ₂ , and Ar _{3 each} represent a phenyl group, a naphthyl group, or an anthracene group; It may be substituted with a plurality of halogen atoms, alkyl groups having 1 to 5 carbon atoms, or alkoxy groups having 1 to 5 carbon atoms. )

(4) The photoconductor for liquid development according to any one of the above (1) to (3), wherein at least one of the compounds having an isocyanate group is a polyisocyanate-modified product.

(5) An image in which an electrostatic charge image is formed on a photosensitive member having a photosensitive layer and a surface protective layer provided on a conductive support, and this electrostatic charge image is developed with a liquid developer to obtain a visible image An image forming method, comprising using the photoconductor for liquid development according to any one of the above (1) to (4).

[0022]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a photoconductor for liquid development comprising a photosensitive layer and a surface protective layer provided on a conductive support, wherein the surface protective layer comprises a compound having a hydroxy group and an isocyanate group. And a compound having a plurality of is bonded to each other to form a network structure, and at least one of the compounds having a hydroxy group is a charge-transporting material having a hydroxy group, which is repeatedly developed with a liquid developer for a long time. However, the present invention succeeded in suppressing the occurrence of cracks in the photosensitive layer and preventing the occurrence of image quality defects and defects due to surface wear of the photosensitive layer when forming an image using such a photoconductor.

The surface protective layer of the present invention comprises a film crosslinked in a network by reacting a compound having a hydroxy group and a compound having a plurality of isocyanate groups with each other. At least one kind of the compound having a hydroxy group is obtained by introducing a hydroxy group into a charge transporting material.

As such a charge transporting material, a material in which a hydroxy group is introduced directly or indirectly into a conventionally used charge transporting material with an appropriate substituent interposed therebetween can be used. Although the number of substitution of the hydroxy group of the charge transporting material may be one or more, in order to form a network structure by crosslinking, a charge transporting material having two or more hydroxy groups is used, or two or more hydroxy groups are used. It is necessary to simultaneously include at least one or more binders having a hydroxy group.

As the charge transporting material having a hydroxy group, those represented by the above structural formulas (A), (B) and (C) have particularly good electrical properties, abrasion resistance and resistance to a solvent in a liquid developer. It is suitable for. Specific examples of the compound represented by the structural formula (A) are shown in Tables 1 and 2 below.

[0026]

[Table 1]

[0027]

[Table 2]

Tables 3 and 4 below show specific examples of the compound represented by the structural formula (B). Tables 5 and 6 show specific examples of the substituent T shown in the structural formula (B).

[0029]

[Table 3]

[0030]

[Table 4]

[0031]

[Table 5]

[0032]

[Table 6]

Further, specific examples of the compound represented by the structural formula (C) are shown in Tables 7 and 8 below.
Tables 9 and 10 show specific examples of the substituent Ar ₁ shown in the structural formula (C).
Tables 11 and 12 show specific examples of r ₂ and Ar ₃ .

[0034]

[Table 7]

[0035]

[Table 8]

[0036]

[Table 9]

[0037]

[Table 10]

[0038]

[Table 11]

[0039]

[Table 12]

In the present invention, as the binder which can be used simultaneously with the charge transporting material having a hydroxy group, monomers, oligomers and polymers having a plurality of hydroxy groups can be used. Specific examples of the monomer / oligomer include glycols such as ethylene glycol and propylene glycol, and polyethylene glycols. Also, various polymers having a hydroxy group such as acrylic polyol and polyester polyol can be used.

Compounds which form a network structure by an addition reaction with the above-mentioned compound having a hydroxy group include:
A polyisocyanate compound having a plurality of isocyanate groups, preferably three or more isocyanate groups can be used.

Specific examples of the polyisocyanate include tolylene diisocyanate (TDI), diphenylmethane diisosocyanate (MDI), 1,5-naphthylene diisocyanate, tolidine diisocyanate, 1,6-hexamethylene diisocyanate, xylene diisocyanate, and lysine. Isocyanate, tetramethylxylene diisocyanate, 1,3,6-hexamethylene triisocyanate, lysine ester triisocyanate, 1,6,11-undecane triisocyanate, 1,8-isocyanate-4-isocyanatomethyloctane, triphenylmethane triisocyanate It is a polyisocyanate using monomers such as isocyanate and tris (isocyanatephenyl) thiophosphate.

However, from the viewpoints of easy handling, film-forming properties of the finally obtained crosslinked film, and cracking resistance, it is necessary to use a derivative such as a derivative or a prepolymer obtained from a polyisocyanate monomer. More desirable. Examples of these include a urethane-modified product obtained by modifying a polyol with an excess of an isocyanate compound, a buret-modified product obtained by modifying a compound having a urea bond with an isocyanate compound,
Particularly preferred are modified allophanates in which isocyanates are added to urethane groups, and also modified isocyanurates and modified carbodiimides.

Blocked isocyanates which are included in the above modified polyisocyanate and reacted with a blocking agent for temporarily masking the activity of isocyanate groups can also be preferably used.

In order to form the surface protective layer of the present invention,
A charge transporting material having a hydroxy group which is an essential component and a polyisocyanate compound, and, if necessary, a binder or a solvent having a hydroxy group are added and mixed, and then applied onto the photosensitive layer and then subjected to crosslinking polymerization. To form a film.

The mixing ratio is preferably adjusted so that the number of all hydroxy groups is substantially equal to the number of all isocyanate groups. In particular, if an excessive hydroxy group remains, the hydrophilicity of the surface of the surface protective layer increases, and the image characteristics under high temperature and high humidity deteriorate. Therefore, care must be taken including reaction conditions.

The content of the charge transporting material in the surface protective layer of the present invention is determined by the molecular weight of the hydroxy group-containing compound and the molecular weight of the isocyanate compound. In order to maintain the electrical properties of the photoreceptor while maintaining mechanical strength, the content of the charge transporting material portion is 5 to 90 parts by weight, preferably 20 to 70 parts by weight, with the entire surface protective layer being 100 parts by weight. It is desirable to be within the range. Since the surface protective layer of the present invention incorporates the charge transporting material by covalent bonds, it is possible to introduce more charge transporting materials than in a normal charge transporting layer.

The surface protective layer of the present invention may be added with various binder resins in order to improve its film formability and flexibility. As this kind of binder resin, it is preferable to use one having compatibility with the film after cross-linking polymerization, and for example, various polymers such as polycarbonate resin, polyester resin, acrylic resin, polyvinyl alcohol resin and polyamide resin may be used. it can. However, in order to maintain the mechanical strength and the electrical characteristics, it is desirable that the content of these binder resins in the surface protective layer is not more than 60 parts by weight based on 100 parts by weight of the entire surface protective layer.

In order to carry out cross-linking polymerization of the surface protective layer of the present invention, the surface protective layer may be heated after coating on the photosensitive layer. Since the addition reaction between the hydroxy group and the isocyanate group depends on the reactivity between the compounds used, no catalyst or the like is required, and only heating is required. When a solvent is used at the time of coating, heat treatment is performed simultaneously with or subsequent to the drying step.

In order to accelerate the crosslinking reaction, a catalyst such as a monoamine, a diamine, a triamine, a cyclic amine, an alcoholamine, or an etheramine may be added according to a conventional method.

The liquid developer used in the present invention is:
A widely used one can be widely used. That is, a liquid developer containing toner particles in which a dye or pigment is dispersed in a binder resin, an electrically insulating liquid, and a charge control agent can be used.

Dyes or pigments used in the liquid developer include inorganic pigments such as carbon black, navy blue and titanium oxide; azo pigments such as fast yellow, pyrazolone red, disazo yellow, chelate red, brilliant carmine and para brown; Phthalocyanine pigments such as copper phthalocyanine, chlorinated copper phthalocyanine, and metal-free phthalocyanine; selected from organic pigments such as quinacridone, anthraquinone, perylene, perinone, thiaindigo, and dioxazine, as well as disperse dyes and oil-soluble dyes. can do.

Examples of the binder resin used in the liquid developer include acrylic resins such as polyacrylates and polymethacrylates; polystyrenes; polyethylene-acrylic acid copolymers; and polyethylene-based vinyl acetate copolymers. Other polyvinyl chloride resins; nitrocellulose; alkyd resins; phenolic resins; polyester resins; polyvinyl butyral resins; polyisocyanate resins; polyurethane resins; epoxy resins, but are not limited thereto.

The electrically insulating liquid used in the liquid developer usually has a dielectric constant of 3.5 or less and a volume resistance of 10 ⁷ Ωc.
m or more of a hydrocarbon solvent is used. Preferred examples thereof include aliphatic hydrocarbons and aromatic hydrocarbons having a boiling point in the range of 150 to 220 ° C., and mixtures thereof.
L. H (main component is isoparaffin), Shell Sol A and B manufactured by Shell Co., Ltd., Naphthesol L. manufactured by Nippon Petrochemical Co., Ltd.
M. H and the like.

Examples of the charge control agent used in the liquid developer include, but are not limited to, cobalt naphthenate, zinc naphthenate, copper naphthenate, manganese naphthenate, lecithin, cobalt octylate, zirconium octylate, and the like. It is not something to be done. Among these, lecithin having a phosphotidylethanolamine or phosphoditylserine content of 40 to 90 parts by weight is desirable. As the ratio of each of the above components of the liquid developer, any ratio used in the art can be used.

The electrophotographic photosensitive member of the present invention will be described with reference to a schematic sectional view. 1 to 4 are cross-sectional views showing specific examples of the electrophotographic photosensitive member of the present invention.
3 shows a case where the photosensitive layer has a laminated structure, and FIGS. 3 and 4 show a case where the photosensitive layer has a single layer structure. The photoreceptor of FIG. 1 has a laminated structure in which a photosensitive layer in which a charge generation layer 1, a charge transport layer 2, and a surface protection layer 5 are formed on a conductive support 3,
The photoreceptor shown in FIG. 2 has a laminated structure in which an undercoat layer 4 is provided on a conductive support 3 and a charge generation layer 1, a charge transport layer 2 and a surface protection layer 5 are formed on the conductive layer. . The photosensitive member of FIG. 3 has a single-layered photosensitive layer in which a photoconductive layer 6 and a surface protective layer 5 are formed on a conductive support 3.
The photoreceptor has a single-layer structure in which an undercoat layer 4 is provided on a conductive support 3 and a photoconductive layer 6 and a surface protective layer 5 are formed thereon.

Examples of the conductive support of the photoreceptor of the present invention include:
Metals such as aluminum, nickel, chromium, and stainless steel; and plastic films provided with thin films such as aluminum, titanium, nickel, chromium, stainless steel, gold, vanadium, tin oxide, indium oxide, and ITO, or conductivity imparting Paper and plastic films coated with or impregnated with an agent; These conductive supports are used in an appropriate shape such as a drum shape, a sheet shape, and a plate shape, but are not limited thereto. Further, if necessary, various processes can be performed on the surface of the conductive support within a range that does not affect the image quality. For example, anodic oxide film treatment, thermal hydroxylation treatment, chemical treatment and coloring treatment of the surface, irregular reflection treatment such as graining, and the like can be performed.

In the present invention, it is preferable to provide an undercoat layer between the conductive support and the photosensitive layer. This undercoat layer
As an adhesive layer that prevents charge injection from the conductive support into the photosensitive layer during charging of the photosensitive layer, and that integrally holds the photosensitive layer on the conductive support. It functions as a layer for preventing reflection of body light.

As the binder resin used for the undercoat layer, polyamide resin, vinyl chloride resin, vinyl acetate resin, phenol resin, polyurethane resin, melamine resin, benzoguanamine resin, polyimide resin, polyethylene resin,
Polypropylene resin, polycarbonate resin, acrylic resin, methacrylic resin, vinylidene chloride resin, polyvinyl acetal resin, vinyl chloride-vinyl acetate copolymer,
Polyvinyl alcohol resin, water-soluble polyester resin,
Known materials such as nitrocellulose, casein, gelatin, polyglutamic acid, starch, starch acetate, amino starch, polyacrylic acid, polyacrylamide, zirconium chelate compound, titanyl chelate compound, titanyl alkoxide compound, organic titanyl compound, silane coupling agent, etc. Can be mentioned. These materials can be used alone or in combination of two or more. Further, the undercoat layer can be mixed with fine particles such as titanium oxide, aluminum oxide, silicon oxide, zirconium oxide, barium titanate, and silicone resin.

The coating method for forming the undercoat layer may be a conventional method such as a blade coating method, a Meyer bar coating method, a spray coating method, a dip coating method, a bead coating method, an air knife coating method, and a curtain coating method. Is adopted. The thickness of the undercoat layer is 0.01 to 10 μm, preferably 0.05
An appropriate range is from 2 μm to 2 μm.

The charge generation layer can be formed by forming the charge generation material by vacuum evaporation or by dispersing and applying the charge generation material to a binder resin in an organic solvent. As the charge generation material used in the present invention, amorphous selenium, crystalline selenium-tellurium alloy, selenium-arsenic alloy,
Other inorganic photoconductive materials such as selenium compounds and selenium alloys, granular selenium, zinc oxide, titanium oxide, phthalocyanine, squarium, anthantrone, perylene, azo, anthraquinone, pyrene, pyrylium salts, thiapyrylium Organic pigments such as salts and dyes can be mentioned.

Among these charge generating materials, photoreceptors using phthalocyanine pigments, particularly metal-free phthalocyanine, titanyl phthalocyanine, and gallium phthalocyanine, are available at near infrared semiconductor laser wavelengths (780 to 830 nm).
m) shows high sensitivity and shows stable electric characteristics over a long period of time.

More specifically, when the Bragg angle (2θ ± 0.2 °) of the X-ray diffraction spectrum by CuKα is at least 6.8 °, 12.8 °, 15.8 ° and 26.0 °, the strong diffraction is obtained. Gallium phthalocyanine showing a precipitation peak, CuKα
Angle of the X-ray diffraction spectrum (2θ ± 0.
2 °) is at least 7.5 °, 9.9 °, 12.5 °,
Hydroxygallium phthalocyanine having strong diffraction peaks at 16.3 °, 18.6 °, 25.1 ° and 28.3 ° (see FIG. 5), Bragg angle of X-ray diffraction spectrum by CuKα (2θ ± 0. 2 °) is at least 7.4
Chlorogallium phthalocyanine having strong diffraction peaks at °, 16.6 °, 25.5 ° and 28.3 ° can be mentioned as a preferable example.

Further, in the visible light wavelength region, an anthrone-based pigment exhibits stable electrical properties over a long period of time, and granular selenium, particularly granular trigonal selenium, exhibits stable electrical properties over a long period of time. The characteristics of higher sensitivity are shown in FIG.

Examples of the binder resin of the charge generation layer include polyvinyl acetal resins such as polyvinyl butyral resin, polyvinyl formal resin, partially acetalized polyvinyl acetal resin in which a part of butyral is modified with formal or acetoacetal, and polyamide resin. Resin, polyester resin, modified ether type polyester resin, polycarbonate resin, acrylic resin, polyvinyl chloride resin,
Polyvinylidene chloride resin, polystyrene resin, polyvinyl acetate resin, vinyl chloride-vinyl acetate copolymer,
Silicone resin, phenol resin, phenoxy resin, melamine resin, benzoguanamine resin, urea resin, polyurethane resin, poly-N-vinylcarbazole resin, polyvinyl anthracene resin, polyvinyl pyrene, and the like can be used.

Among them, polyvinyl acetal resin, vinyl chloride-vinyl acetate copolymer, phenoxy resin and modified ether type polyester resin are particularly suitable for the above-mentioned phthalocyanine or anthantrone pigments and granular trigonal selenium. It is possible to provide a coating solution in a dispersed state which is dispersed and stable over a long period of time without aggregating the pigment. By using the coating solution, a coating film can be formed uniformly, and as a result, the photoreceptor can be formed. Has been improved, and image quality defects can be significantly suppressed. The resin is not limited to these as long as it is a resin capable of forming a film in a normal state. These binder resins can be used alone or in combination of two or more. The mixing ratio of the charge generation material and the binder resin is 5: 1 to 1 by volume.
A range of 1: 2 is preferred.

Solvents used for preparing the coating solution include methanol, ethanol, n-propanol, n
-Butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, chlorobenzene, methyl acetate,
Commonly used organic solvents such as n-butyl acetate, dioxane, tetrahydrofuran, methylene chloride, chloroform and the like can be used alone or in combination of two or more.

As a method of applying the coating liquid, a commonly used method such as a blade coating method, a Meyer bar coating method, a spray coating method, a dip coating method, a bead coating method, an air knife coating method, a curtain coating method, and the like are used. be able to.

The thickness of the charge generation layer is 0.01 to 5 μm,
Preferably, the range is 0.1 to 2.0 μm. If the thickness is less than 0.01 μm, it is difficult to form the charge generation layer uniformly, and if it exceeds 5 μm, the electrophotographic properties tend to be significantly reduced.

The charge transport layer contains at least a charge transport material and a binder resin. As the charge transport material,
p-benzoquinone, chloranyl, bromoanil, quinone compounds such as anthraquinone, tetracyanoquinodimethane compounds, fluorenone compounds such as 2,4,7-trinitrofluorenone, xanthone compounds, benzophenone compounds, cyanovinyl compounds, ethylene Examples thereof include electron-withdrawing substances such as compounds, triarylamine compounds, benzidine compounds, arylalkane compounds, aryl-substituted ethylene compounds, stilbene compounds, anthracene compounds, and hydrazone compounds. These charge transport materials can be used alone or in combination of two or more.

Examples of the binder resin include polycarbonate resin, polyester resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinylidene chloride resin, polystyrene resin, polyvinyl acetate resin, styrene-butadiene copolymer, and vinylidene chloride-acrylonitrile copolymer. Polymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, silicone resin, silicone-alkyd resin, phenol-formaldehyde resin, styrene-acrylic resin, styrene-alkyd resin, poly- Known resins such as N-vinylcarbazole and polysilane can be used.

Further, an antioxidant may be added to the charge transport layer. Since the charge transport layer is not the outermost layer, it does not come into direct contact with the oxidizing gas, but these oxidizing gases may penetrate the surface protective layer and penetrate to the charge transport layer. is there. As the antioxidant, hindered phenol-based or hindered amine-based antioxidants are preferable, and organic sulfur-based antioxidants, phosphite-based antioxidants, dithiocarbamate-based antioxidants, thiourea-based antioxidants, and benzimidazole-based antioxidants A well-known antioxidant such as may be used. The addition amount of the antioxidant is suitably 15 parts by weight or less, more preferably 10 parts by weight or less based on 100 parts by weight of the surface protective layer.

Solvents used for forming the charge transport layer include aromatic hydrocarbons such as benzene, toluene, xylene and chlorobenzene, ketones such as acetone and 2-butanone, and halogenated solvents such as methylene chloride, chloroform and ethylene chloride. Ordinary organic solvents such as aliphatic hydrocarbons, cyclic or linear ethers such as tetrahydrofuran, ethyl ether and dioxane can be used alone or in combination of two or more. The method for applying the charge transport layer can be the same as that for the charge generation layer. The thickness of the charge transport layer is in the range of 5 to 50 μm, preferably 10 to 40 μm.

When a single-layer type photosensitive layer is formed, it is composed of the above-mentioned charge generating substance and a binder resin. As the binder resin, those similar to the binder resins used for the charge generation layer and the charge transport layer can be used. The content of the charge generating substance in the single-layer type photosensitive layer is 10 to 85 parts by weight, preferably 20 to 5 parts by weight, per 100 parts by weight of the photosensitive layer.
A range of 0 parts by weight is suitable. Note that an antioxidant may be added to the single-layer type photosensitive layer, if necessary, for the same reason as in the case of the charge transport layer. The addition amount is 15 parts by weight or less,
Preferably, the amount is 10 parts by weight or less.

In the image forming method using the liquid developer according to the present invention, a compound having a hydroxy group and a compound having an isocyanate group are allowed to react with each other on the surface protective layer to form a network-crosslinked film. This suppresses image quality defects due to cracks. Further, since the surface protective layer has excellent abrasion resistance, corona discharge resistance, and toner filming resistance, the photoreceptor does not have any problem even when used repeatedly for a long time, and the electrophotographic characteristics do not deteriorate. As a result, the image forming method of the present invention can maintain high repetition stability, exhibit high printing durability, and exhibit excellent image quality even when repeatedly performed for a long time using a copying machine and a printer. A copy image can be provided.

[0076]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto. In the examples and comparative examples, “parts” means parts by weight.

[Example 1] (Preparation of photoreceptor) Zirconium compound (Orgatics ZC540, manufactured by Matsumoto Pharmaceutical Co., Ltd.) on an aluminum substrate
10 parts, silane compound (manufactured by Japan Junker Co., A111
0) 1 part, 40 parts of isopropanol and 20 of butanol
And a solution composed of the following components, prepared by a dip coating method, and dried by heating at 150 ° C. for 10 minutes to form a film having a thickness of 0.1 μm.
Was formed.

Next, as a charge generation material, X shown in FIG.
1 part of hydroxygallium phthalocyanine having a line diffraction spectrum, 1 part of a carboxyl-modified vinyl chloride-vinyl acetate copolymer (manufactured by Union Carbide, VMCH),
And 100 parts of chlorobenzene were dispersed together with glass beads in a sand mill for 1 hour. The obtained coating solution is applied on the undercoat layer by a dip coating method,
The resultant was dried by heating at 100 ° C. for 10 minutes to form a charge generation layer having a thickness of 0.25 μm.

In addition, 8 parts of a benzidine compound represented by the following structural formula (1) and 12 parts of a polycarbonate resin represented by the following structural formula (2) are dissolved in 80 parts of monochlorobenzene, and the obtained coating solution is subjected to the above-mentioned charge generation. The resultant was applied on the layer by a dip coating method and dried by heating at 115 ° C. for 60 minutes to form a charge transport layer having a thickness of 20 μm.

[0080]

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[0081]

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Then, 3 parts of the exemplified compound (A-2) as a charge transporting material having a hydroxy group, and 2 parts of a burette-modified polyisocyanate represented by the following structural formula (3) (a molar ratio of about 3 Vs. 2)
Dissolved in a solvent consisting of 5 parts of methyl ethyl ketone and 5 parts of cyclohexanone, spray-coated on the charge transport layer, dried at room temperature for 10 minutes, and then heated at 130 ° C. for 60 minutes to form a surface protective layer having a thickness of 4 μm. Thus, an electrophotographic photosensitive member was completed.

[0083]

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(Preparation of Liquid Developer) A charge controlling agent was prepared by mixing 20 parts of lecithin containing 90 parts of phosphatidylserine and 80 parts of Isopar M manufactured by Exxon Chemical Company.
After 1 part of carbon black, 20 parts of ethylene-vinyl acetate copolymer, and 75 parts of the above-mentioned Isopar M were dispersed in a sand mill for 10 hours, the liquid had a solid content ratio (carbon black + ethylene-vinyl acetate copolymer) of the whole. The toner liquid was diluted with the above Isopar M so as to be 3 parts. Then, 100 parts of the toner liquid and 1 part of the charge control agent were mixed to obtain a liquid developer.

(Test Method) A copier (FX) manufactured by Fuji Xerox Co., Ltd.
2700), and performed a copy running test of up to 50,000 copies under the environment of 20 ° C. and 45% RH using the above liquid developer. evaluated. Table 13 shows the results.

[0086]

[Table 13]

Comparative Example 1 A photoreceptor was prepared in the same manner as in Example 1 except that the surface protective layer of the photoreceptor was omitted, and a similar test was conducted. Table 13 shows the results.

Comparative Example 2 In Example 1, the charge transport layer of the photoreceptor was replaced with 8 parts of a hydrazone compound represented by the following structural formula (4) and 12 parts of a polycarbonate resin represented by the following structural formula (5) by monochlorobenzene. Dissolved in 80 parts, the obtained coating solution was applied on the charge generation layer of the photoreceptor of Example 1 by dip coating, and dried by heating at 115 ° C. for 60 minutes.
A photoreceptor similar to that of Example 1 was prepared and a similar test was conducted except that a charge transport layer having a thickness of 20 μm was formed and the surface protective layer was omitted. Table 13 shows the results.

[0089]

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[0090]

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Example 2 In Example 1, instead of the compound (A-2) of the charge transporting material having a hydroxy group, the compound (B-7) 1 was added to the surface protective layer of the photoreceptor.
And 1 part of the polyisocyanate represented by the above structural formula (3) (about 3 to 2 in molar ratio) is dissolved in 5 parts of cyclohexanone, and applied on the charge transport layer of the photoreceptor of Example 1 by dip coating. And dried at room temperature for 10 minutes.
A photoconductor was prepared in the same manner as in Example 1 except that a surface protective layer having a thickness of 4 μm was formed, and the same test was conducted. Table 13 shows the results.

Example 3 In Example 1, instead of Exemplified Compound (A-2) of the charge transporting material having a hydroxy group, which was added to the surface protective layer of the photoreceptor, Exemplified Compound (C-10)
3 parts and 2 parts (about 3 to 2 in molar ratio) of a polyisocyanate represented by the following structural formula (6) as a compound having isocyanate are dissolved in 5 parts of methyl ethyl ketone and 5 parts of cyclohexanone. After spray coating on the charge transport layer and drying at room temperature for 10 minutes,
A photoconductor was prepared in the same manner as in Example 1 except that a surface protective layer having a thickness of 5 μm was formed by heating at 50 ° C. for 60 minutes, and a similar test was performed. Table 13 shows the results.

[0093]

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Comparative Example 3 In Example 1, the charge transporting layer of the photoreceptor was prepared by dissolving 20 parts of a charge transporting polymer compound represented by the following structural formula (7) in 80 parts of tetrahydrofuran.
The obtained coating solution was applied on the charge generation layer of the photoreceptor of Example 1 by a dip coating method, and dried by heating at 115 ° C. for 60 minutes to form a charge transport layer having a thickness of 20 μm. A photoreceptor similar to that of Example 1 was prepared, and a similar test was performed, except that the omission was omitted. Table 13 shows the results.

[0095]

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(Results) As is clear from Table 13, the photoreceptors of Examples 1 to 3 showed little surface wear even after running 50,000 sheets, and the image quality after copying 50,000 sheets was good. Was.
On the other hand, in Comparative Examples 1 and 3, the wear on the surface of the photoconductor progressed to about three times that of the embodiment. In Comparative Example 1, a crack was generated on the surface of the photoconductor after copying 1000 sheets, and the pattern corresponding to the crack was copied. Printed out above. In Comparative Example 2, the charge transport material was eluted after 500 copies, resulting in a decrease in the sensitivity of the photoreceptor. As a result, a decrease in image density occurred, and the evaluation was stopped after 100 copies. In Comparative Example 3, printout occurred on the surface of the photosensitive member after copying 20,000 sheets, and the image density decreased after copying 30,000 sheets.

[0097]

According to the present invention, by adopting the above-mentioned constitution, even if the liquid developer is repeatedly developed for a long period of time, defects such as image quality defects due to cracks on the electrophotographic photosensitive member and defects due to surface wear of the photosensitive layer. , And high image quality can be maintained for a long period of time.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing one example of the electrophotographic photosensitive member of the present invention.

FIG. 2 is a cross-sectional view schematically showing another example of the electrophotographic photosensitive member of the present invention.

FIG. 3 is a cross-sectional view schematically illustrating another example of the electrophotographic photosensitive member of the present invention.

FIG. 4 is a cross-sectional view schematically showing another example of the electrophotographic photosensitive member of the present invention.

FIG. 5 is a powder X-ray diffraction spectrum of hydroxygallium phthalocyanine used in Examples (using CuKα).

Claims (5)

[Claims] 1. A liquid developing photoreceptor comprising a photosensitive layer and a surface protective layer provided on a conductive support, wherein the surface protective layer bonds a compound having a hydroxy group and a compound having a plurality of isocyanate groups to each other. A photoreceptor for liquid development, wherein the photoreceptor has a network structure, and at least one of the compounds having a hydroxy group is a charge transporting material. 2. The liquid developer according to claim 1, wherein the compound having a hydroxy group contains a charge transporting material having at least one hydroxy group and a binder having at least two hydroxy groups. Photoreceptor. 3. The liquid developing device according to claim 1, wherein at least one of the charge transporting materials having a hydroxy group is represented by the following structural formulas (A) to (C). Photoconductor. Embedded image (Wherein R ₁ , R ₂ and R ₃ represent a hydrogen atom, a halogen atom,
Represents an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or an amino group substituted with an alkyl group having 1 to 2 carbon atoms; Represents a divalent hydrocarbon group which may be branched, represented by Formulas 1 to 10, and n is 0 or 1. ) (R ₄ is a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, and 1 to 5 carbon atoms substituted with a halogen atom.
, An alkoxy group having 1 to 5 carbon atoms, a phenyl group, or a halogen atom as a substituent, an alkyl group having 1 to 5 carbon atoms, and 1 to 5 carbon atoms substituted with a halogen atom. Wherein T is a phenyl group containing an alkyl group having 1 to 5 carbon atoms or an alkoxy group having 1 to 5 carbon atoms, and T is a divalent hydrocarbon which may be branched and has 1 to 10 carbon atoms in an aliphatic portion. The group, n, is 0 or 1. ) (R ₅ is hydrogen or an alkyl group having 1 to 5 carbon atoms, X is hydrogen, an alkyl group having 1 to 5 carbon atoms, a phenyl group, or a halogen atom as a substituent,
5 represents an alkyl group in the range of 5, an alkyl group in the range of 1 to 5 carbon atoms substituted with a halogen atom, or a phenyl group containing an alkoxy group in the range of 1 to 5 carbon atoms; Ar ₁ , Ar ₂ , and Ar ₃ each represent a divalent hydrocarbon group which may be branched, and may represent a phenyl group, a naphthyl group, or an anthracene group; It may be substituted with a halogen atom, an alkyl group having 1 to 5 carbon atoms, or an alkoxy group having 1 to 5 carbon atoms. ) 4. The photoconductor for liquid development according to claim 1, wherein at least one of the group of compounds having an isocyanate group is a modified polyisocyanate. 5. An image forming method in which an electrostatic charge image is formed on a photosensitive member having a photosensitive layer and a surface protective layer provided on a conductive support, and the electrostatic charge image is developed with a liquid developer to obtain a visible image. 5. An image forming method, comprising using the photoconductor for liquid development according to claim 1.