JPH0895280A - Electrophotographic photoreceptor - Google Patents

Abstract

(57) [Abstract] [Purpose] An electrophotographic photoreceptor having excellent durability and high image quality by suppressing an increase in residual potential of a protective layer made of organopolysiloxane and preventing cracks without lowering hardness. I will provide a. In an organic photoreceptor in which a protective layer or an intermediate layer and a protective layer are laminated on a photosensitive layer, the protective layer comprises a mixture of organopolysiloxane, colloidal silica, a conductive metal oxide and / or an acrylic resin. Characteristic electrophotographic photoreceptor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly durable electrophotographic photoreceptor having a protective layer.

[0002]

2. Description of the Related Art Electrophotographic photoreceptors using a so-called Carlson process include electrophotographic photoreceptors using organic substances. For example, poly-N-vinylcarbazole and 2,
A photoreceptor composed of 4,7-trinitrofluorenone-9-one (US Pat. No. 3,484,237) and a photoreceptor prepared by sensitizing poly-N-vinylcarbazole to a pyrylium salt dye. JP-B-48-25658), a photoreceptor containing an organic pigment as a main component (JP-A-47-37543).
(Japanese Patent Laid-Open No. 3), a photoconductor containing a eutectic complex composed of a dye and a resin as a main component (JP-A-47-10735), and a photoconductor obtained by dye-sensitizing a triphenylamine compound (US Pat. 180,730), a photoreceptor using an amine derivative as a charge transport material (JP-A-57-195254), and a photoreceptor using poly-N-vinylcarbazole and an amine derivative as a charge transport material (JP-A-58-58). 115
5), a photoconductor using a benzidine compound among polyfunctional tertiary amine compounds as a photoconductive material (U.S. Pat. No. 3,265,496, Japanese Patent Publication No. 39-11546, Japanese Patent Publication No. 53-27033). ) And so on. However, since these organic photoreceptors mainly use a plastic resin such as polycarbonate for the charge transport layer, a sharp copy image cannot be obtained due to abrasion and abrasion by a cleaning blade or paper in a copying machine. The life of the photoconductor is suppressed. Therefore, an organopolysiloxane thin film formed of a curable silicon compound such as a hydrolyzed condensate of an alkoxysilane is formed on an organic photoconductor, and a hard protective layer is provided to improve wear resistance. The idea is to extend life. In this case, in order to increase the durability of the organic photoconductor 3 to 10 times, a protective layer having a thickness of at least 2 μm or more is required.

However, a film formed only of organopolysiloxane has a drawback that cracks occur when the thickness exceeds 1 μm. Therefore, by mixing colloidal silica as described in JP-B-5-46940, flexibility is improved. It has been proposed that the film be provided with this method, and by this method, a crack-free film can be formed up to approximately 5 μm. On the other hand, if it exceeds 1 to 2 μm, the residual potential becomes large and the background stains on the image, so that it cannot be used as a protective layer of a photoreceptor. As described in JP-A-1-263660, it has been proposed to mix an acrylic resin such as acrylic polyol which has the effect of lowering the flexibility and the residual potential. According to this method, it is possible to form a film having neither crack nor residual potential up to about 5 μm. However, in order to obtain this effect, it is necessary to add 30 to 50% by weight of an acrylic resin in the protective layer, and the hardness of the film is significantly reduced, so that sufficient durability cannot be obtained.

A method has been proposed in which a conductive metal oxide is added in order to reduce the residual potential of the protective layer made of organopolysiloxane, but this structure causes more cracks than the organopolysiloxane alone. Will occur. Therefore, in order to prevent cracks, a method of mixing colloidal silica or a resin has been proposed. In JP-A-3-135575, a thermosetting silicone resin (hydrolyzed condensate of organoalkoxysilane) and an acrylic polymer are mixed on a photoreceptor, and a conductive metal oxide is further dispersed. However, although there is no problem of residual potential, it is necessary to add 30 to 50% by weight or more of an acrylic resin in order to prevent cracks, which lowers the hardness of the film and lowers the durability. Further, in JP-A-5-341551, a protective layer is formed on a photoreceptor by a thermosetting silicone resin (hydrolyzed condensate of organoalkoxysilane), a urethane elastomer, colloidal silica and a conductive metal oxide. However, since urethane-based resin has the effect of increasing the residual potential, if the ratio of the conductive metal oxide is small, the residual potential is large, and conversely, if the ratio of the conductive metal oxide is large, the film becomes brittle. It has the drawback of cracking.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional drawbacks, and specifically, suppresses the increase in residual potential of the protective layer made of organopolysiloxane, and the hardness. The present invention provides an electrophotographic photoreceptor having excellent durability and high image quality by preventing cracks without decreasing the value.

[0006]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that the above problems can be achieved by adding a specific substance to a protective layer composed of organopolysiloxane and colloidal silica. The present invention has been completed. That is,
The present invention is the following (1) to (3). (1) In an organic photoreceptor having a protective layer or an intermediate layer and a protective layer laminated on a photosensitive layer, the protective layer comprises a mixture of organopolysiloxane, colloidal silica and a conductive metal oxide. body. (2) An electrophotographic photoreceptor in which a protective layer or an intermediate layer and a protective layer are laminated on a photosensitive layer, wherein the protective layer comprises a mixture of organopolysiloxane, colloidal silica and an acrylic resin. (3) In an organic photoreceptor in which a protective layer or an intermediate layer and a protective layer are laminated on a photosensitive layer, the protective layer is composed of a mixture of organopolysiloxane, colloidal silica, a conductive metal oxide and an acrylic resin. An electrophotographic photosensitive member.

The photosensitive layer of the photosensitive member used in the present invention is an organic photosensitive member and may have either a laminated structure of a charge generating layer and a charge transporting layer or a single layer structure having a charge generating and transporting function. I don't care. When the layer structure is a single layer type, a photosensitive layer in which a charge generating substance and a charge transporting substance are dispersed in a binder is provided on a conductive substrate. In the case of the function separation type, a charge generating layer containing a charge generating substance and a binder, and a charge transporting layer containing a charge transporting substance and a binder are formed on the substrate. The transport layers may be laminated in reverse. In the case of the function separation type, a charge transport material may be contained in the charge generation layer. Particularly, in the case of the positive charging structure, the sensitivity is good.

An intermediate layer may be provided between the photosensitive layer and the substrate in order to improve the adhesiveness and the charge blocking property. The surface protective layer of the present invention is laminated on the photosensitive layer, and its structural example is shown in FIGS. Here, FIG. 1 shows a function-separated type organic photoreceptor, and FIG. 2 shows a function-integrated type organic photoreceptor. For the surface protective layer, the polymer compound composition of the present invention, a mixture of a charge transporting material and a polymer compound composition, or a polymer compound composition having a charge transporting ability can be used. When the charge transport material is added, it is preferably contained in an amount of 0 to 200% by weight, more preferably 30 to 100% by weight, based on the polymer compound composition. The thickness of the surface protective layer is 0.01
If it is at least μm, it can be preferably used, and 0.5 μm
It is more preferable that the above is satisfied. When the charge transport ability is not given, 0.01 to 10 μ is preferable, and 0.1 to 2
More preferably, it is μm. An intermediate layer may be provided between the surface protective layer and the photosensitive layer in order to prevent mixing of both layers. Each layer constituting the photoreceptor of the present invention will be described below.

(1) Substrate (undercoat layer) This photosensitive layer is formed on a conductive substrate, and the substrate is A
Metals or alloys such as 1, Ni, Fe, Cu and Au, or metals such as Al, Ag and Au or indium oxide, tin oxide and the like on an insulating substrate such as polyester, polyethylene terephthalate, polycarbonate, phenol, polyimide and glass. A thin film of the conductive material is used. In addition, an undercoat layer made of a resin or the like may be provided for the purpose of adhesion between the substrate and the photosensitive layer and charge retention. (2) Charge Generation Layer As the charge generation pigment contained in the charge generation layer, disazo type, trisazo type, azoxybenzene type, benzimidazole type, polycyclic quinone type, indigoid type, quinakeridone type, phthalocyanine type, perylene are used. Known types include methine type and methine type pigments, and any pigment can be used as long as it is a pigment that generates an electric charge upon irradiation with light. These pigments alone or together with a binder resin are dispersed in a solvent with a dispersing machine such as a ball mill or an attritor to prepare a coating solution, which can be prepared by an appropriate method such as dipping coating, spray coating, knife coating, or roll coating. It can be formed and the film thickness is set to 1 μm or less.

(3) Charge Transport Layer As organic charge transport materials used in the charge transport layer, poly-N-vinylcarbazole compounds, pyrazoline compounds, α-phenylstilbene compounds, hydrazone compounds, diarylmethane compounds, Conventionally known compounds such as triphenylamine compounds, divinylbenzene compounds, fluorein compounds, anthracene compounds, oxadiazole compounds and diaminocarbazole compounds can be used. These charge-transporting substances are dissolved in a solvent together with resins such as polyurethane, polyester, epoxy resin, polycarbonate, polyvinyl butyral, and poly-N-vinylcarbazole to prepare a coating solution, and dipping coating, spray coating, knife coating roll coating, etc. The charge transport layer having a film thickness of 10 to 50 μm can be formed by an appropriate method. (4) Intermediate layer When a protective film is formed on the photosensitive layer, the adhesive force between the two is weak, and when the number of copies is increased, peeling may occur between both layers, and an image may not be formed on that portion. In order to prevent such peeling, a method of providing an intermediate layer between the photosensitive layer and the protective layer can be used. The intermediate layer is polyacrylic acid that firmly adheres to both the photosensitive layer and the protective layer,
Resins such as polymethylmethacrylate, polyethylmethacrylate, polyvinyl butyral, and polyvinyl formal are selected, and a solution obtained by dissolving these in a solvent can be formed by an appropriate method such as dipping coating, spray coating, knife coating, or roll coating. . The film thickness is 0.1
1.0 μm is preferable.

(5) Protective Layer The organopolysiloxane can be formed by heat-curing a hydrolysis-condensation product of an organoalkoxysilane. The hydrolysis-condensation product of this organoalkoxysilane is R ¹ _x Si (OR ² ) _y (R ¹ is a C1-5 alkyl group, phenyl group, vinyl group, NH ₂ , SH, Cl, epoxy group, acrylic Represents a C1-5 alkyl group having a group, R ² represents hydrogen, a C1-5 alkyl group, x is 0 to 2, y is 2 to 4 and x + y = 4. It is prepared by adding a catalyst such as hydrochloric acid to silane to accelerate the hydrolysis condensation reaction. The solvent used in the coating liquid for protective layer is preferably a solvent that does not attack the photosensitive layer (charge transport layer), and alcoholic solvents such as methanol, ethanol and isopropanol are mainly used.

Next, the substances used for producing the protective layer of the photoreceptor of the present invention will be described in more detail below. Organopolysiloxane includes tetraalkoxysilane, trialkoxyalkylsilane, dialkoxydialkylsilane and other organosilanes, trichloroalkylsilane,
A hydrolyzate of a silane compound such as an organohalogensilane such as dichlorodialkylsilane, or a hydrolyzate of a mixture of two or more thereof, or an initial condensation reaction product thereof dissolved or dispersed in a solvent as a non-volatile solid content. As the alkoxy group and the alkyl group of the silane compound, a methoxy group, an ethoxy group, an isopropoxy group, a t-butoxy group,
Examples thereof include lower groups having about 1 to 4 carbon atoms such as glycidoxy group, methyl and ethyl. Examples of the acrylic resin used together with the organopolysiloxane include homopolymers or copolymers of acrylic monomers such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, and butyl methacrylate. The average molecular weight of the acrylic polymer is limited to 6000 or less. When the average molecular weight exceeds 6000, as described above, the solubility in the coating liquid decreases and a uniform film cannot be formed. Because.

Examples of the conductive metal oxides include simple metal oxides such as tin oxide, titanium oxide, indium oxide and antimony oxide, and solid solutions of tin oxide and antimony oxide. A thermosetting resin or a thermoplastic resin other than those described above can be used together with the binder resin forming the protective layer as long as the characteristics of the film are not impaired. Other binder resins other than the above are curable acrylic resins; alkyd resins; unsaturated polyester resins; diallyl phthalate resins; phenol resins; urea resins; benzoguanamine resins; melamine resins; styrene polymers; styrene-acrylic copolymers. Polymer: olefin polymer such as polyethylene, ethylene-vinyl acetate copolymer, chlorinated polyethylene, polypropylene, ionomer; polyvinyl chloride;
Examples are vinyl chloride-vinyl acetate copolymers; polyvinyl acetate; saturated polyesters; polyamides; thermoplastic polyurethane resins; polycarbonates; polyarylates; polysulfones; ketone resins; polyvinyl butyral resins; polyether resins.

In the protective layer, conventionally known sensitizers such as terphenyl, halonaphthoquinones and acenaphthylene; 9-
Fluorene compounds such as (N, N-diphenylhydrazino) fluorene and 9-carbazolyliminofluorene;
Various additives such as a conductivity-imparting agent; an antioxidant such as an amine-based or phenol-based agent; a deterioration inhibitor such as an ultraviolet absorber such as a benzophenone-based agent; a plasticizer can be contained. The thickness of the protective layer is 0.1 to 10 μm, and particularly 2 to
It is preferably within the range of 5 μm. The photosensitive member of the present invention is not limited to the above-mentioned examples with respect to the structure other than the protective layer, and may have the same structure as the conventional one using the same material as the conventional one.

Examples of the solvent that constitutes the coating liquid for the protective layer by dissolving or dispersing the components of the above organopolysiloxane, colloidal silica, conductive metal oxide and / or acrylic resin include isopropyl alcohol; −
Hexane, octane, cyclohexane, and other aliphatic hydrocarbons; benzene, toluene, xylene, and other aromatic hydrocarbons; dichloromethane, dichloroethane, carbon tetrachloride, chlorobenzene, and other halogenated hydrocarbons; dimethyl ether, diethyl ether, tetrahydrofuran, ethylene glycol Examples include ethers such as dimethyl ether, ethylene glycol diethyl ether, and diethylene glycol dimethyl ether; ketones such as acetone, methyl ethyl ketone, and cyclohexanone; esters such as ethyl acetate and methyl acetate; dimethylformamide; dimethyl sulfoxide and the like, and these alone or Used as a mixture of two or more kinds. The coating solution for the protective layer containing the organopolysiloxane or the like can be cured only by heating without using a catalyst depending on the conditions, but usually in order to complete the curing reaction smoothly and uniformly A catalyst can be used. As a curing catalyst,
Various substances such as inorganic or organic acids and alkalis such as amines can be used. Further, if necessary, a conventionally known curing aid or the like can be used in combination.

In the present invention, the weight ratio of organopolysiloxane to colloidal silica is 100: 1 to 100: 3.
0, the weight ratio of organopolysiloxane to conductive metal oxide is 100: 10 to 100: 100, and the weight ratio of organopolysiloxane to acrylic resin is 100: 1 to 10
It is 0:30. The method for preparing the protective layer of the photoreceptor of the present invention is to add a colloidal silica, a conductive metal oxide and / or an acrylic resin and a conductive metal oxide to a hydrolysis-condensation product of an organoalkoxysilane to prepare a protective layer. Create a coating solution. This solution can be used to form the protective layer by an appropriate method such as dipping coating, spray coating, knife coating, or roll coating, and the film thickness is arbitrarily set, but 1 to 10 μm is preferable. The colloidal silica is selected from an aqueous dispersion having a particle size of 10 to 50 nm or an alcohol dispersion. By mixing colloidal silica, cracks can be prevented without lowering the hardness of the film. If the particle size is smaller than 10 nm, cracks cannot be prevented.

The acrylic resin is preferably alcohol-soluble, and the residual potential can be lowered by mixing it. At the same time, cracks can be prevented, but on the other hand, the hardness is lowered, so that it is preferably used in an amount of 30% by weight or less. The residual potential can be lowered by mixing the conductive metal oxide. As the conductive metal oxide, tin oxide, indium oxide, antimony oxide, a dispersion liquid obtained by dispersing a solid solution of these in an alcohol solvent, or a colloid liquid is used. It is preferable that these particles have an average particle diameter of 0.3 μm or less, preferably 0.1 μm or less so that visible light is transmitted.

[0018]

EXAMPLES The present invention will be described in detail below with reference to examples and comparative examples. Example 1 (1) Substrate 0.5 mm thick Al plate (2) Subbing layer coating liquid Soluble nylon (Toray: Alamine CM-8000) 5 parts by weight Methanol 95 parts by weight The above is mixed and dissolved to form a coating liquid. did. (3) Coating liquid for charge generation layer Butyral resin (Sekisui Chemical Co., Ltd .: S-REC BLS) 7 parts by weight Tetrahydrofuran 145 parts by weight The above are mixed and dissolved to prepare a disazo pigment 10 of the following structural formula (I).
Parts by weight were added and dispersed by a ball mill for 72 hours. Further, 200 parts by weight of cyclohexanone was added and dispersion was carried out for 1 hour. Dilute it with cyclohexanone while stirring,
The solid content was 2.0% by weight.

[0019]

[Chemical 1]

(4) Coating liquid for charge transport layer Polycarbonate (Teijin: Panlite C-1400) 10 parts by weight Charge transfer agent having the following structural formula (II) 7 parts by weight Tetrahydrofuran 83 parts by weight A coating liquid is prepared according to the above composition. did.

[0021]

[Chemical 2]

(5) Coating Liquid for Intermediate Layer Polyethylmethacrylate (Scientific Polymer Products: # 308) 3 parts by weight Methylcellosolve 97 parts by weight The above components were mixed and dissolved to prepare a coating liquid. (6) Protective Layer Coating Liquid Keeping 10 parts by weight of 0.01N hydrochloric acid at 0 to 10 ° C., 25 parts by weight of methyltrimethoxysilane and 10 parts by weight of tetraethoxysilane were gradually dropped with stirring and then left to stand. , A hydrolysis-condensation product of organoalkoxysilane was prepared. Next, while stirring this, 10 parts by weight of colloidal silica (Nissan Chemical: Snowtex 20) and 45 parts by weight of isopropyl alcohol were added. Further, 80 parts by weight of a tin oxide colloid methanol solution (Nissan Chemical Co., Ltd.) was mixed to prepare a coating liquid A for the protective layer.

(7) Coating and film formation A coating liquid for undercoat layer is blade-coated on a substrate, and the coating liquid is applied at 100 ° C. for 1 hour.
It was dried by heating for 0 minutes to obtain a film thickness of 0.3 μm. The charge generation layer coating solution is blade-coated on top of it,
It was dried by heating for 0 minutes to obtain a film thickness of 0.2 μm. The charge transport layer coating solution is blade-coated on it, and the temperature is increased to 120 ° C for 2
It was dried by heating for 0 minutes to obtain a film thickness of about 19 μm. After the photosensitive layer was formed by the above procedure, the intermediate layer coating solution was blade-coated and dried to obtain a film thickness of 0.25 μm. Finally, the coating solution A for the protective layer is blade coated, and the coating is performed at 120 ° C. for 6 hours.
A protective layer was prepared by heating and drying for 0 minutes.

(8) Evaluation The following two items were evaluated for the prepared samples. The results are shown in Table 1. Wear amount by Taber type wear test (wear wheel: CS
Residual potential (potential 30 seconds after charging exposure, manufactured by Kawaguchi Denki:
EPA8100) Presence of cracks

[0025]

[Table 1]

Example 2 (1) Substrate, coating solution The same coating solution as in Example 1 was used for the substrate and the undercoat layer, the charge generation layer, the charge transport layer and the intermediate layer. The coating solution B for the protective layer was prepared by mixing the following substances with 100 parts by weight of the mixture of the hydrolyzed condensate of organoalkoxysilane prepared in Example 1 and colloidal silica to prepare the coating solution B for the protective layer. Poly 2-hydroxyethyl acrylate (Scientific Polymer Products: # 850) 20 parts by weight Isopropyl alcohol 60 parts by weight (2) Coating and film formation Each coating solution was coated and film-formed in the same manner as in Example 1. (3) Evaluation The prepared samples were evaluated as in Example 1 (abrasion amount, residual potential, cracks). The results are shown in Table 2.

[0027]

[Table 2]

Example 3 (1) Substrate, coating solution The same coating solution as in Example 1 was used for the substrate and the undercoat layer, the charge generation layer, the charge transport layer and the intermediate layer. The protective layer coating liquid was prepared by mixing the following substances with 100 parts by weight of the mixture of the hydrolyzed condensate of organoalkoxysilane and colloidal silica prepared in Example 1 to prepare a protective layer coating liquid C. Poly-2-hydroxyethyl acrylate (Scientific Polymer Products: # 850) 15 parts by weight Tin solution of colloidal tin oxide in methanol (Nissan Chemical Co., Ltd.) 65 parts by weight (2) Coating and film formation Each coating solution is applied and formed in the same manner as in Example 1. Filmed (3) Evaluation The prepared samples were evaluated as in Example 1 (abrasion amount, residual potential, cracks). Table 3 shows the results.

[0029]

[Table 3]

Comparative Example 1 (1) Substrate, coating solution The same coating solution as in Example 1 was used for the substrate and the undercoat layer, the charge generation layer, the charge transport layer, and the intermediate layer. Coating solutions D and E for protective layer were prepared by the following method. The following substances were mixed with 100 parts by weight of the mixture of the hydrolyzed condensate of organoalkoxysilane prepared in Example 1 and colloidal silica. D. 60 parts by weight of isopropyl alcohol The following substances were mixed with 100 parts by weight of the hydrolysis-condensation product of the organoalkoxysilane prepared in Example 1.

E. Poly 2-hydroxyethyl acrylate (Scientific Polymer Products: # 850) 20 parts by weight Isopropyl alcohol 60 parts by weight (2) Coating and film formation A sample having a photosensitive layer formed on a substrate by the same method as in Example 1 is designated as F. The intermediate layer and the protective layer coating liquids D and E were formed on F by the same method as in Example 1. (3) Evaluation The prepared samples were evaluated as in Example 1 (abrasion amount, residual potential, cracks). The results are shown in Table 4.

[0032]

[Table 4]

[0033]

As described above, according to the present invention, it is possible to form a protective layer which is hard and has excellent abrasion resistance, but does not cause cracks and has a small residual potential on the organic photoconductor, so that the durability is improved. It is possible to provide a high-quality electrophotographic photoreceptor having excellent properties.

[Brief description of drawings]

FIG. 1 shows the structure of a function-separated type organic photoreceptor.

FIG. 2 shows a structure of a function-integrated organic photoreceptor.

[Explanation of symbols]

 1 Substrate 2 Subbing Layer 3 Charge Generation Layer 4 Charge Transport Layer 5 Intermediate Layer 6 Protective Layer 7 (Single Layer) Photosensitive Layer

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Naoki Imahashi 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (3)

[Claims] 1. An organic photoreceptor having a protective layer or an intermediate layer and a protective layer laminated on a photosensitive layer, wherein the protective layer comprises a mixture of organopolysiloxane, colloidal silica and a conductive metal oxide. Photoreceptor. 2. An organic photoconductor having a protective layer or an intermediate layer and a protective layer laminated on a photosensitive layer, wherein the protective layer comprises a mixture of organopolysiloxane, colloidal silica and acrylic resin. body. 3. An organic photoreceptor having a protective layer or an intermediate layer and a protective layer laminated on a photosensitive layer, wherein the protective layer comprises a mixture of organopolysiloxane, colloidal silica, a conductive metal oxide and an acrylic resin. Characteristic electrophotographic photoreceptor.