JPH11271990A - Electrophotographic photoreceptor and method of manufacturing the same - Google Patents

Abstract

(57) [Problem] To provide a novel electrophotographic photoreceptor. SOLUTION: In an electrophotographic photoreceptor having a layer in which a charge generating agent is dispersed in a binder polymer, a block copolymer having an alcohol-soluble monomer component and an alcohol-insoluble monomer component is used as the binder polymer. .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrophotographic photosensitive member used for a copying machine or the like. More specifically, the present invention relates to an electrophotographic photoreceptor in which a specific block copolymer is used as a binder polymer of a layer in which a charge generating agent is dispersed to improve performance such as improvement in sensitivity and reduction in residual potential.

[0002]

2. Description of the Related Art Photoreceptors using inorganic photoconductive materials such as selenium, cadmium sulfide, and zinc oxide have been used as electrophotographic photoreceptors, but recently, non-polluting products have been manufactured. And organic photoconductive compounds (OPCs) having many advantages such as easy handling, good image quality, and easy to obtain photoconductors of various shapes such as drums, sheets and belts. So-called OPC using
Photoconductors have been used for copiers and printers, and the ratio has been increasing year by year. OPC photoconductors have many advantages over conventional inorganic photoconductors.

Many attempts have been made to improve the sensitivity and durability of OPC photosensitive members. The first commercially available OPC photoconductor was polyvinyl carbazole (PV).
K) and a photoreceptor utilizing a sensitizing effect of a charge transfer complex formed by mixing an electron-withdrawing compound, 2,4,7-trinitrofluorenone (TNF). However, a number of charge-transfer complex-type OPC photoconductors have been developed since then, but those having performance exceeding PVK-TNF-based photoconductors have not been put to practical use. At present, a photoreceptor called a function-separated type, in which the functions of generating and transporting charge carriers are separated and assigned to different compounds, is mainly put to practical use. Function-separated photoreceptors can combine compounds with high charge carrier generation efficiency and high transport efficiency compounds, and have a wide selection of materials with excellent durability, high sensitivity and durability. It is a type that can obtain a photosensitive member with excellent properties.

There are two types of function-separated type photoreceptors: a stacked type in which a charge generating material and a charge transporting material are separated into separate layers and stacked, and a single-layer type included in the same photosensitive layer. However, in each case, the charge generation material absorbs light to generate charges, and the generated charges are injected into the charge transport material,
The process of transferring charges between molecules of a charge transport material is performed in a photoconductor. Therefore, the sensitivity of the photoreceptor depends on the charge generation efficiency, injection efficiency, and transport efficiency, and the charge generation material with high generation efficiency and charge transport material with high transport efficiency, and the charge generation material with high injection efficiency and transport material have high A combination has been selected.

[0005] Such a function-separated type charge generation layer includes:
Pigments that absorb visible light or near-infrared light are often used. This pigment is generally ground into submicron particles,
It is often dispersed and mixed with a binder polymer in a solvent, and then applied to form a film. The binder polymer often functions as a dispersant that prevents the pigment particles pulverized in the dispersion liquid from reaggregating, in addition to the function as a binder in forming a film. In general, a dispersion having excellent stability is adsorbed on the surface of pigment particles and acts as a barrier for carrier separation and transport, resulting in a decrease in characteristics such as a decrease in sensitivity and an increase in residual potential. To date, almost no binder polymer having excellent dispersion stability and excellent characteristics as an electrophotographic photosensitive member has been obtained. It is known that block copolymers exhibit excellent properties as dispersants. This is because one block in the block copolymer is adsorbed on the particle surface, and the other block enhances the affinity with the solvent and prevents aggregation of the particles.

[0006]

DISCLOSURE OF THE INVENTION The present invention is characterized in that the dispersion has excellent stability, does not act as a barrier for carrier separation or transport even when adsorbed on the surface of pigment particles, and has the characteristics of decreasing sensitivity and increasing residual potential. An object of the present invention is to construct an electrophotographic photoreceptor using a binder polymer which does not bring about a reduction in image quality.

[0007]

Means for Solving the Problems The present inventors have developed an electrophotographic photoreceptor having a layer in which a charge generating agent composed of an organic pigment is dispersed, in which a block copolymer having a special structure is dispersed. The inventors have found that the binder polymer exhibits extremely excellent properties, and have reached the present invention. That is, the gist of the present invention is to provide an electrophotographic photoreceptor having a layer in which a charge generator composed of an organic pigment is dispersed in a binder polymer, wherein the binder polymer is a block copolymer,
And an electrophotographic photoreceptor characterized in that at least one of the monomer components of the block copolymer forms a polymer having high solubility or affinity for alcohol when formed into a homopolymer, and production thereof. Be in the way.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In producing an electrophotographic photosensitive member,
In order to form a film by dispersing and applying a pigment, a binder polymer is generally required. This binder polymer has the function of improving the dispersion stability of the pigment particles in the solvent, and improving the mechanical properties of the film and the adhesion to the substrate. When the dispersion characteristics of the dispersion liquid change, the viscosity of the liquid changes or the pigment particles settle, leading to deterioration in productivity. On the other hand, the binder polymer adsorbed on the surface hinders the contact between the pigment surface and the charge transport molecule, and causes adverse effects such as a decrease in sensitivity and an increase in residual potential.

A polymer material added as a dispersing agent for stably dispersing the fine particles of the organic pigment in the solvent generally prevents the pigments from aggregating by adsorbing on the surface of the fine particles. For example, polyvinyl butyral, which is most frequently used, is strongly adsorbed on the surface of a pigment even in an organic solvent to stabilize the dispersion. However, polyvinyl butyral is a compound of hydrocarbon and oxygen whose skeleton is saturated, and the adsorbed part is considered to be a high barrier against charge separation and charge injection.If the amount of polyvinyl butyral actually used is increased, the sensitivity is reduced. And an increase in the residual potential. However, if the amount of polyvinyl butyral is not reduced or used at all, disadvantages such as poor dispersion stability of the pigment liquid and poor adhesion of the layer to the substrate are observed.

In the case where one of the block copolymers is composed of an alcohol-soluble or high-affinity part and an insoluble part in the other, the block copolymer is present on the pigment particle surface when coexisting with organic pigment fine particles in alcohol. When the coalesced portion is adsorbed and the alcohol-soluble portion faces outward and the insoluble portion contacts the pigment surface, the affinity of the particle surface for alcohol is improved, and the dispersion is stabilized. This situation is schematically illustrated in FIGS. 1 and 2 using one compound of the invention as an example. FIG. 1 schematically shows a block copolymer, in which each block is represented by a rectangle and an ellipse.
FIG. 2 shows how molecules are adsorbed on the pigment surface when the organic pigment is dispersed in alcohol.
Since the alcohol-soluble portion is directed outward to stabilize the dispersion, the alcohol-insoluble portion comes into contact with the pigment surface, and this portion should be made into a structure that is convenient for charge separation and charge injection. If this is the case, it is possible to prevent a decrease in electrical characteristics.

In a photoelectric conversion material such as an electrophotographic photoreceptor containing a pigment and a charge transporting molecule (CTM), the pigment molecule absorbs light to generate charge carriers. In a sex CTM, electrons are injected into the CTM. The mechanism by which charge carriers are generated is such that electron transfer occurs between impurities such as oxygen contained in pigment particles in the excited state (exciton) of pigment molecules, and electron transfer occurs between CTM on the pigment surface. There are many things to think about. In any case, carrier injection and carrier generation occur on the surface of the pigment particles, and it is important what state they are in.

The component for improving the electric characteristics is preferably an unsaturated hydrocarbon, an aromatic compound or a heterocyclic compound, rather than a saturated hydrocarbon. Further, those having a charge transporting ability are preferable, and in a system in which holes are injected or generated, a system in which the component has a low ionization potential and easily accepts holes is preferable, and a system in which electrons are injected or generated. It is preferable that the component has a low electron affinity and easily accepts electrons. In the present invention, a block copolymer is a polymer compound obtained from a plurality of types of monomer components. A chain composed of a single type of monomer forms a block in a polymer, and two or more types of the block form a block. It refers to what is linked by joining. For example, it is synthesized from two types of monomers A and B. AAA... AABBB... BBB or a structure including a plurality of these.
The repeating number of each monomer is 2 or more. Further, if such a structure is partially present, the rest may include a polymer obtained by randomly polymerizing a plurality of monomers. The block copolymer has a structure in which a plurality of polymers having different functions are integrated into one, and various functions can be designed.

When the molecular weight is too small, the mechanical strength of the polymer is deteriorated. When the molecular weight is too large, there are disadvantages such as increased difficulty in production and increased viscosity of the solution, which makes handling difficult. 1000-50
Thousands, preferably about 3000 to 100,000 can be used. Further, the monomer component having a charge transporting ability or the monomer component forming a homopolymer soluble in alcohol is contained in the block copolymer in a mole fraction of 1 to 99%, preferably 5 to 95%. Is good.

The monomer which forms a homopolymer which is soluble or has a high affinity in alcohol means one which dissolves or swells in isopropyl alcohol when the homopolymer has a molecular weight of about 10,000. Many monomers that form a homopolymer that is soluble or have a high affinity for alcohol include a hydroxyl group, and one hydroxyl group is contained in an alkyl methacrylate such as hydroxyethyl methacrylate (hereinafter abbreviated as HEMA), hydroxypropyl methacrylate, or hydroxybutyl methacrylate. Those having two or more substitutions are exemplified.

[0015]

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The monomer component which is insoluble in alcohol when formed into a homopolymer is preferably a monomer component having a charge transporting ability. The component having a charge transporting ability is generally a low molecular compound contained in a charge transporting layer of a layered electrophotographic photosensitive member, and is classified into a compound which transports holes and a compound which transports electrons. The charge transporting agent that transports holes is easily oxidized to become a cation, and the cation radical (hole carrier) is used to transfer electricity by hopping to the next molecule. Such components include carbazole, indole, imidazole, oxazole, pyrazole, oxadiazole, pyrazoline, heterocyclic compounds such as thiadiazole,
Many of them have an aniline derivative, a hydrazone compound, an aromatic amine derivative, a stilbene derivative, or a group having these compounds.

An electron transporter is easily reduced to an anion, and is used to transfer electricity by hopping the anion radical (electron carrier) to the next molecule. Many of such components have an electron-withdrawing substituent such as a nitro group, a cyano group, and a carbonyl group. Examples of materials containing such a polymerizable charge transport material include, for example, those disclosed in
-180852, JP-A-61-20953, JP-A-1-20952
179164, JP-A-4-133065, JP-A-6-2
56428, JP-A-5-040350, JP-A-5-04
5922 and the like. Even if it is not contained in the monomer, it can be introduced after polymerization by reaction with a polymer. Such an example is disclosed in
323630. Taking triphenylamine as an example of the charge transporting material and taking a monomer as an example, the following can be mentioned.

[0018]

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The block copolymer of the present invention can be synthesized by a living polymerization method in which active species during polymerization are not deactivated in a reaction system by anionic polymerization, cationic polymerization, radical polymerization or the like. That is, a desired block copolymer can be obtained by polymerizing one monomer and polymerizing another monomer from its active terminal. In addition, the components (A
In the case of a -B type block, a group capable of reacting and binding to each other may be added to the terminals of A and B), and then reacted to form a block copolymer. Furthermore, there is also a method in which an initiator having two or more active groups at which polymerization starts under different conditions is used, and one block is formed from one active group, and then another block is formed from another active group.

The block copolymer of the present invention may be directly synthesized by polymerization, or may be synthesized from another easily copolymerizable block copolymer by a polymer reaction. In particular, in the living polymerization method, there are restrictions on the types of monomers that can be polymerized.Therefore, it is necessary to protect a group active in the polymerization system with a protecting group and to remove the protecting group after polymerization to obtain a desired polymer. Often. For example, in anionic living polymerization, a hydroxyl group or an amino group is polymerized by protecting it with a trialkylsilyl group or the like, and by a deprotecting group of the obtained polymer,
A desired block copolymer can be obtained.

When the block copolymer of the present invention is used as a binder polymer for a pigment having photoconductivity, an increase in sensitivity and a decrease in residual potential are observed. The pigment having photoconductivity referred to herein is an electrophotographic photoreceptor, which is an organic dye compound (pigment) hardly soluble in a solvent used as fine particles (for example, particles of 1 μm or less) and absorbs light. And capable of generating carriers. As examples thereof, various organic pigments and dyes such as phthalocyanine, azo dye, quinacridone, squarylium, polycyclic quinone, pyrylium salt, thiapyrylium salt, indigo, thioindigo, anthantrone, pyranthrone and cyanine can be used. Among them, metals such as metal-free phthalocyanine, copper, indium chloride, gallium chloride, gallium hydroxide, tin, oxytitanium, zinc, oxyvanadium, and hydroxysilicon,
Alternatively, azo pigments such as phthalocyanines, monoazo, bisazo, trisazo, and polyazos coordinated with metal oxides, chlorides, and hydroxides are preferable. Examples of particularly preferred organic pigments include azo pigments having the following coupler.

[0022]

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Here, Z represents an aromatic ring or a heterocyclic ring which may have a substituent. Examples of more specific azo pigments include the following.

[0024]

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Here, R ¹ and R ² represent a hydrogen atom, a monovalent organic group such as a lower alkyl group or an alkoxy group in which the hydrogen atom may be substituted by a fluorine atom, a halogen atom and the like. The ratio between the block copolymer of the present invention and the pigment is not particularly limited, but generally, the azo compound 100
5 to 500 parts by weight, preferably 20 to 3 parts by weight based on parts by weight
00 parts by weight of binder resin are used. In addition, a dispersion stabilizer, a coating improver, and a dye, an electron-withdrawing compound, and other additives for improving performance may be added.

By dispersing such an organic pigment, mixing with the material of the present invention, and applying the mixture to a conductive support, a high-performance carrier generation layer can be produced. Although photoconductivity can be used by itself, a charge transport agent can be used to produce a higher-performance photoreceptor. This may be a single-layer constitution in which it is mixed with an organic pigment, or a two-layer constitution as a layer separate from the carrier generation layer. As the charge transporting agent, a low molecular weight compound having a carrier transporting ability dissolved in a polymer, or a low molecular weight compound having a charge transporting ability or a substance having a high molecular weight bonded to a polymer can be considered, but both can be used. .

Various forms are known for the photosensitive layer of the electrophotographic photosensitive member, and any of the photosensitive layers of the electrophotographic photosensitive member of the present invention may be used. For example, a photosensitive layer in which a charge generating agent particle that generates charge carriers with extremely high efficiency when absorbing light and a compound having a charge transporting ability is added to a binder, a charge transporting layer including a compound having a charge transporting ability and a binder, and Examples of the photosensitive layer include charge generating particles that generate charge carriers with extremely high efficiency of absorption, or a layer obtained by laminating a charge generating layer formed of the particles and a binder.

Among them, a typical example to which the block copolymer of the present invention can be applied is a laminate type structure. This is a photosensitive member having, on a conductive support, a photosensitive layer containing the block copolymer of the present invention and the pigment exhibiting photoconductivity described above, and a layer containing a charge transport material. In addition, a layer for improving performance such as electric characteristics and mechanical characteristics such as an intermediate layer such as an adhesive and a blocking layer, and a protective layer may be provided. The charge generation layer and the charge transport layer may be stacked in any order. However, since the charge generation layer is thin and easily damaged by mechanical damage, the charge transport layer is usually stacked on the charge generation layer.

As the conductive support, any of those used for known electrophotographic photosensitive members can be used. Specific examples include metal drums and sheets of aluminum, copper, and the like, and laminates and vapor-deposits of these metal foils. Furthermore, metal powder, carbon black, copper iodide,
Examples thereof include plastic films, plastic drums, and paper, which are obtained by applying a conductive material such as a conductive polymer or a polymer electrolyte together with an appropriate binder and conducting a conductive treatment. In addition, a conductive plastic sheet or drum containing a conductive substance such as metal powder, carbon black, or carbon fiber, or a plastic film having a conductive metal oxide layer such as tin oxide or indium oxide on its surface. And the like. A well-known barrier layer which is usually used may be provided between the conductive support and the charge generation layer. As the barrier layer, for example, an anodized aluminum film, aluminum oxide, inorganic layers such as aluminum hydroxide, polyvinyl alcohol, casein, polyvinylpyrrolidone, polyacrylic acid, celluloses, gelatin,
An organic layer of starch, polyurethane, polyimide, polyamide, or the like, an organic layer in which fine particles of aluminum oxide or titanium oxide are dispersed, and the like are used.

This is because a metal such as aluminum, nickel or iron or a metal on which a metal is deposited, or a conductive substrate such as a polymer composite or a conjugated polymer in which conductive particles such as metal or carbon black are dispersed are used. In addition, a dispersion film of pigment particles using the block copolymer of the present invention as a binder polymer is 0.0
A film (charge transport layer) formed by dissolving or dispersing a charge transport substance in a binder polymer such as polycarbonate, polystyrene, PMMA, polyester, polysulfone, polyamide, and polyimide is formed.
It is formed about 50 μm. On the conductive substrate,
As the intermediate layer, a polymer film in which a metal oxide such as alumina or titania is dispersed may be used, or a protective layer may be formed on the charge transport layer.

The charge transporting material used in combination with the compound of the present invention is generally classified into two types, an electron transporting material and a hole transporting material, and both can be used for the photoreceptor of the present invention. Mixtures thereof can also be used. Examples of the electron transporting material include electron-withdrawing compounds having an electron-withdrawing group such as a nitro group, a cyano group, and an ester group.
Examples include nitrated fluorenone such as 7-trinitrofluorenone and 2,4,5,7-tetranitrofluorenone, and tetracyanoquinodimethane. Further, as a hole transport material, an electron-donating organic photoconductive compound,
For example, carbazole, indole, imidazole, oxazole, thiazole, oxadiazole, pyrazole, pyrazoline, thiadiazole, benzoxazole, benzothiazole, heterocyclic compounds such as naphthothiazole, diarylalkane derivatives such as diphenylmethane, triarylalkanes such as triphenylmethane Derivatives, triarylamine derivatives such as triphenylamine, phenylenediamine derivatives, N-phenylcarbazole derivatives, diarylethylene derivatives such as stilbene, hydrazone compounds, etc., and particularly, substituted amino such as dialkylamino group and diphenylamino group. Group, or an electron-donating group such as an alkoxy group or an alkyl group, or an electron substituted by a aromatic group substituted by these electron-donating groups Large compound of given properties and the like. Further, polymers having a group consisting of the above compounds in the main chain or side chain, such as polyvinyl carbazole, polyglycidyl carbazole, polyvinyl pyrene, polyvinyl phenyl anthracene, polyvinyl acridine, and pyrene-formaldehyde resin, may also be used.

The carrier transporting material may be used as a mixture of two or more kinds. When the charge transport material is a polymer compound having a film-forming property, a binder resin may not be particularly used, but may be mixed for improving flexibility and the like. When the charge transport material is a low molecular compound, a binder resin is used for forming a film. The above-mentioned binder resins are used, and the amount of the binder resin is usually 50 to 3000 parts by weight, preferably 70 to 1 part by weight, per 100 parts by weight of the charge transporting material.
000 parts by weight.

Examples of the binder resin for such a charge transport material include polymers and copolymers of vinyl compounds such as styrene, vinyl acetate, acrylates, methacrylates, vinyl alcohol and ethyl vinyl ether, phenoxy resins, polysulfones, and the like. Polyvinyl acetal, polycarbonate, polyester, polyamide,
Examples include polyurethane, cellulose, ester, cellulose ether, epoxy resin, silicon resin and the like.

Solvents for adjusting the coating solution include ethers such as tetrahydrofuran and 1,4-dioxane; ketones such as methyl ethyl ketone and cyclohexanone; aromatic hydrocarbons such as toluene and xylene; N, N-dimethylformamide, acetonitrile , N-methylpyrrolidone,
Aprotic polar solvents such as dimethyl sulfoxide; esters such as ethyl acetate, methyl formate, and methyl cellosolve acetate; solvents that dissolve hydrazone-based compounds such as chlorinated hydrocarbons such as dichloroethane and chloroform. Of course, it is necessary to select a material that dissolves the binder from these. In addition to the above, various additives can be used in the charge transport layer in order to improve the performance and the mechanical strength and durability of the coating film. Examples of such additives include electron-withdrawing compounds and dyes, stabilizers such as UV-absorbing agents and antioxidants, coatability improvers, plasticizers, and crosslinking agents.

Examples of the electron-withdrawing compound include chloranil, 2,3-dichloro-1,4-naphthoquinone, 2-methylanthraquinone, 1-nitroanthraquinone and 1-nitroanthraquinone.
Quinones such as chloro-5-nitroanthraquinone, 2-chloroanthraquinone and phenanthrenequinone; 4
Aldehydes such as -nitrobenzaldehyde, ketones such as 9-benzoylanthracene, indandione, 3,5-dinitrobenzophenone, 3,3 ', 5,5'-tetranitrobenzophenone, phthalic anhydride and 4-chloronaphthalic anhydride Compounds such as acid anhydrides, tetracyanoethylene, terephthalalmalononitrile, 4-nitrobenzalmalononitrile, 4-benzoyloxybenzalmalonenitrile, and 4- (p-nitrobenzoyloxy) benzalmalononitrile 3-benzalphthalide, 3- (α-cyano-p-nitrobenzal) phthalide, 3- (α-cyano-p-nitrobenzal) -4,
And phthalides such as 5,6,7-tetrachlorophthalide.

In the case of a single-layer type photoreceptor, the photoreceptor can be obtained by dissolving or mixing a charge transporting material in a dispersion of the block copolymer of the present invention and a pigment. It can be obtained by applying a liquid. It becomes a laminated type function-separated type photoconductor. The thickness of the charge generation layer is 0.05 to 5 μm, preferably 0.1 to 2 μm.
The thickness of the single-layer type photosensitive layer is usually 5 to 50 μm, preferably 1 to 50 μm.
0 to 30 μm. The application to the electrophotographic photoreceptor has been described above, but the block copolymer of the present invention can be widely applied to other applications. For example, a solar cell, an organic electroluminescence, an optical sensor, and the like utilize the electric conduction of an organic substance similar to an electrophotographic photosensitive member, and the description in the application to electrophotography can be applied. Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited to these Examples.

[0037]

EXAMPLES Example 1 (Synthesis of N, N-diphenylaminostyrene (hereinafter abbreviated as DPA)) Triphenylphosphine (40.4 g) was dissolved in dimethylformamide (DMF), and 32.2 g of methyl iodide was added thereto. The mixture was added dropwise at 30 ° C. or lower for 30 minutes, and the mixture was stirred for 5 minutes after completion of the addition. To this, 28.5 g of N, N-diphenylaminobenzaldehyde was added. 55.6 g of a methanol solution of 28% sodium methylate was added dropwise in 20 minutes. During this time, heat generation was observed, and the mixture was ice-cooled so as not to exceed 30 ° C. After the dropwise addition, the mixture was heated on a hot water bath at 45 ° C. for 1 hour, and TLC confirmed that the raw materials had disappeared. The reaction solution was allowed to cool, poured into 1.5 liters of water at about 30 ° C., and stirred.
The resulting precipitate was filtered and washed with 200 ml of cold methanol. This was dissolved by heating in 135 ml of ethanol, filtered while hot, allowed to cool, and further cooled with ice, and the resulting crystals were filtered.
Washed with cold methanol. This was repeated twice and dried under reduced pressure to obtain 15.5 g of pale yellow powdery crystals. Melting point 91-9
The structure was confirmed at 2 ° C., mass spectrum and NMR.

(Polymerization of Block Copolymer) All polymerization experiments were performed by the break seal method under ultra-high vacuum (10 ⁻⁶ mmHg). DPA was dried under high vacuum in the presence of P ₂ O ₅ for 72 hours. Methacrylic acid (tetramethylsilyloxyethyl) (hereinafter abbreviated as HEMA-TMS) was distilled in the presence of calcium under hydrogen and further purified by ultrahigh vacuum distillation in the presence of trioctylaluminum. First, DPA1
0.1 mmol was polymerized at −78 ° C. for 1.5 hours using THF as a solvent and 0.176 mmol of s-butyllithium as an initiator. There diphenylethylene 0.3
56 mmol was added and left for 15 minutes. 0.778 mmol of lithium chloride was added thereto, and HEMA-TMS was added.
10.0 mmol was added and polymerized at -78 ° C for 0.5 hour. Thereafter, the polymerization reaction was stopped by adding methanol from which dissolved gas had been removed. The polymerization solution was filtered to remove glass fragments and concentrated under reduced pressure to minimize the solvent THF. This is n
-Injection into 400 ml of hexane gave a block polymer precipitate. The obtained polymer was dissolved in THF to give n-
Purification was performed twice by a reprecipitation method injecting into hexane to obtain 3.64 g (yield 90%) of white powder. FIG. 3 shows the IR spectrum of the obtained polymer film. It is considered that the band derived from the OH group was observed because part of the trimethylsilyl group was eliminated during the post-treatment.

The following treatment was carried out to completely deprotect the obtained block copolymer. Block polymer3.
10 g was dissolved in THF 30 ml, and 2N hydrochloric acid 3.9 m
1 was added dropwise to adjust the pH to 2, followed by stirring at room temperature for 3 hours. The reaction solution was concentrated under reduced pressure, dissolved in a small amount of THF, poured into hexane, and the deposited precipitate was filtered. This was reprecipitated with THF-hexane. This was further dissolved in THF, 1.56 g of triethylamine was added dropwise, and the mixture was stirred at room temperature for 2 hours. After concentration under reduced pressure, the mixture was poured into hexane and reprecipitated with THF-hexane and dichloromethane-hexane. Furthermore, it is dissolved in 400 ml of methylene chloride, and 3 ml with 350 ml of water.
After washing twice, the organic layer was concentrated under reduced pressure to a minimum amount, poured into hexane, and reprecipitated again with dichloromethane-hexane. The obtained precipitate was filtered and dried to obtain 2.47 g of a white powder. This IR spectrum is shown in FIG.

(Preparation of coating solution) 0.86 g of the disazo pigment shown below was suspended in 30 g of isopropanol, 50 ml of glass beads were added, and the mixture was stirred for 9 hours at 3200 rpm in a 100 ml stainless steel beaker with ice cooling. Distributed processing was performed. A solution obtained by dissolving 0.4 g of the block copolymer obtained in the above method in 4 g of THF was added to 14.4 g of this dispersion, and isopropanol was added so that the solid content concentration became 2.6% by weight. Adjusted. This mixture was further ultrasonically dispersed in an ultrasonic cleaner. The condition is that the weight ratio of the disazo pigment to the block copolymer is 1: 1, but the amount of the block copolymer is reduced, and the dispersions of 1: 0.6 and 1: 0.3 are also used. Prepared.

[0041]

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The dispersion state was determined by measuring a dispersion index and used as a standard. The dispersion index here was obtained by diluting a pigment dispersion with a dispersion solvent and determining the ratio (%) of the absorbance at 640 nm and 530 nm. The azo pigment used was 530 nm
Has strong absorption, but hardly any absorption at 640 nm, and the absorbance at 530 nm is 640 nm due to absorption of the pigment.
The absorbance in nm is due to the scattering of the pigment particles. Therefore, the dispersion index is an amount related to the non-uniformity of the refractive index of the liquid, and can be easily used to observe the change in the dispersion state. However, since the absolute value includes not only the particle size of the pigment particles but also the refractive index of the polymer and the solvent contained therein and the scattering by the aggregate of the polymer alone, the focus here is only on the change with time. As a result of measuring the dispersion index of the above dispersion, it was observed that the dispersion index did not change at all even after storage at room temperature for 2 months or more, as shown in FIG. The viscosity of the liquid did not change either.

(Preparation of photoreceptor) The dispersion obtained as described above was placed on an aluminum deposition layer deposited on a polyester film by a wire bar so that the weight after drying was 0.4 g / m ^2. After the application, it was dried to form a charge generation layer. The hydrazone compound shown below

[0044]

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A solution prepared by dissolving 90 parts of 100 parts of a polycarbonate resin (manufactured by Mitsubishi Chemical Corporation, Novarex 7025, trade name) in a mixed solvent of 585 parts of tetrahydrofuran and 315 parts of dioxane was applied to a thickness of 28 microns.
After drying, the characteristics as an electrophotographic photosensitive member were measured. As a result, the half-life exposure amount by white light is 0.54 lux · s
ec. First, the half-exposure amount is set at 50
negatively charged by a μA corona current, and then exposed to 1 lux of white light, with a surface potential of -450 V to -225 V
It was determined by measuring the amount of exposure required to decay to.

Comparative Example 1 Example 1 was repeated except that polyvinyl butyral (trade name “Denka Butyral” # 6000-C, manufactured by Denki Kagaku Kogyo KK) was used instead of the block copolymer.
An electrophotographic photoreceptor was produced in exactly the same manner as described above. As a result of measuring the characteristics as an electrophotographic photosensitive member, the white light sensitivity is
It was 0.86 lux · sec. Comparative Example 2 In a dispersion containing only pigment particles to which no block copolymer was added, it was observed that the dispersion index gradually increased. In a dispersion containing no binder, the dispersion state changed due to aggregation of the particles. (FIG. 5). Comparative Example 3 In Example 1, instead of isopropanol as a dispersion solvent,
When pentoquinone was used, the dispersion index was observed to increase gradually, and it was found that the dispersion state was changed by the aggregation of particles (FIG. 6). It was also observed that the viscosity of the liquid increased with time.

[0047]

As is apparent from the above, the present invention provides a binder polymer which acts as a dispersant for a pigment and provides a photoreceptor which is effective for dispersion stabilization and has excellent electrophotographic properties. Things.

[Brief description of the drawings]

FIG. 1 is a schematic view of a block copolymer of the present invention.

FIG. 2 is a conceptual diagram in which the block copolymer of the present invention stabilizes the dispersion of an organic pigment.

FIG. 3 is an IR absorption spectrum (before deprotection group treatment) of the block copolymer in Example 1.

FIG. 4 is an IR absorption spectrum (after deprotection group treatment) of the block copolymer in Example 1.

FIG. 5 shows the change over time of the dispersion index of the isopropanol pigment dispersion containing the block copolymer of Example 1, and the change over time of the dispersion index of the pigment dispersion containing no binder.

FIG. 6 is a graph showing the change over time in the dispersion index of a pentoquinone pigment dispersion containing the block copolymer of Example 1.

Claims (6)

[Claims] 1. An electrophotographic photoreceptor having a layer in which a charge generating agent comprising an organic pigment is dispersed in a binder polymer, wherein the binder polymer is a block copolymer, and a monomer component of the block copolymer is used. At least one of which forms a polymer having high solubility or affinity for alcohol when formed into a homopolymer. 2. The electrophotographic photoreceptor according to claim 1, wherein the block copolymer is a homopolymer, and a monomer component that forms a polymer having high solubility or affinity for alcohol, and a homopolymer. An electrophotographic photoreceptor that is a block copolymer containing a monomer component that forms a polymer that is insoluble in alcohol when subjected to heat treatment. 3. The electrophotographic photoreceptor according to claim 2, which has at least a charge transporting ability of a monomer component which forms a polymer insoluble in alcohol when formed into a homopolymer. 4. The electrophotographic photoreceptor according to claim 1, wherein the monomer component which forms a polymer which is soluble or has a high affinity for alcohol when formed into a homopolymer contains a hydroxyl group. An electrophotographic photoreceptor that is a monomer component. 5. The electrophotographic photosensitive member according to claim 1, wherein the organic pigment is an azo pigment having the following coupler. Embedded image (In the formula, Z represents an aromatic ring or a heterocyclic ring which may have a substituent.) 6. The method for producing an electrophotographic photoreceptor according to claim 1, wherein a binder polymer and an organic pigment are coexistent, dispersed in an alcohol solvent, and coated. A method for producing an electrophotographic photosensitive member, comprising forming a layer in which a charge generating agent is dispersed.