JP2785282B2 - Electrophotographic photoreceptor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electrophotographic photosensitive member comprising a conductive support, an undercoat layer, and a photosensitive layer.

2. Description of the Related Art Conventionally, electrophotographic photoreceptors have been broadly classified into those using inorganic pigments and those using organic pigments as charge generation materials. In addition, a function-separated type electrophotographic photoconductor in which functional layers having respective functions are stacked is often used. Such a function-separated type electrophotographic photoreceptor has many advantages in terms of material selection and electrophotographic characteristics. As the function-separated type, an organic photoreceptor, that is, an electrophotographic photoreceptor using an organic pigment as a charge generating material is often used. Further, a material in which an inorganic pigment such as selenium is dispersed in a binder resin to form a charge generation layer and an organic polymer layer laminated as a charge transport layer is also used.

In such a function-separated type electrophotographic photoreceptor, an organic charge generation layer and an organic charge transport layer are provided on a conductive substrate.
At this time, in order to prevent unnecessary charge injection from the conductive substrate into these layers or to enhance the adhesion between the conductive substrate and these layers, a subbing layer is provided between them. Provision is often made.

Materials used for the undercoat layer include polyvinyl alcohol, polyvinyl pyrrolidone, polyvinyl pyridine,
Examples include cellulose ethers, cellulose esters, polyamide, polyurethane, casein, gelatin, polyglutamic acid, starch, starch acetate, amino starch, polyacrylic acid, polyacrylamide, etc. A material which is not affected by the solvent of the coating solution for the applied charge generation layer or charge transport layer and does not cause a problem in electrical characteristics is selected. Among them, the polyamide resin has the advantages of excellent adhesiveness as described above and little problem in electrical characteristics.

Problems to be Solved by the Invention However, an electrophotographic photoreceptor using a polyamide-based resin for an undercoat layer, when used for a long period of time, is likely to cause dot-like white spots in the obtained copy image. This causes a problem that there is a limit to the number of copies that can be obtained with good quality copy / print. In particular, in an environment with high humidity, the number of sheets for which good copies / prints can be obtained tends to decrease, and there is a problem that the life of the electrophotographic photosensitive member is shortened.

An object of the present invention is to provide an electrophotographic photoreceptor which does not have the above-mentioned problems even when a polyamide resin is used as an undercoat layer.

Means for Solving the Problems The electrophotographic photoreceptor of the present invention is an electrophotographic photoreceptor obtained by sequentially laminating a conductive support, an undercoat layer and a photosensitive layer, wherein the undercoat layer is N-methoxymethylated. A coating film formed by applying a nylon solution is thermally crosslinked at a temperature of 135 ° C. to 150 ° C., and has an insolubility in a solvent used for the N-methoxymethylated nylon solution. 35% or more.

In the electrophotographic photoreceptor of the present invention, the photosensitive layer may have a single-layer structure, but preferably has a laminated structure in which a charge generation layer and a charge transport layer are functionally separated.

The drawing is a schematic view showing a cross section in the case of a laminated structure, wherein 1 is a charge transport layer, 2 is a charge generation layer, 3 is an undercoat layer,
Reference numeral 4 denotes a conductive support.

In the present invention, as the conductive support, aluminum, copper, stainless steel or other metal drums and sheets, plastic films and paper, etc., laminated with a metal foil such as aluminum, or deposited with aluminum or gold Conductive treatments, such as treated ones, may be mentioned.

The surface of the conductive support can be subjected to various treatments within a range that does not affect the image quality. For example, oxidation treatment or chemical treatment of the surface can be performed.

The undercoat layer is formed by thermally cross-linking a coating film formed by applying a solution of N-methoxymethylated nylon at a temperature of 135 ° C to 150 ° C.

Examples of the solvent used for obtaining the solution of N-methoxymethylated nylon include methanol, ethanol, butanol, n-propyl alcohol, i-propyl alcohol, water, phenol, cresol and the like.

In order to form an undercoat layer, the solution of N-methoxymethylated nylon is coated on a conductive support, and then dried by heating at a temperature of 135 ° C to 150 ° C. The heating and drying must be performed so that the finally formed undercoat layer is crosslinked so that the insolubility of the solution in the N-methoxymethylated nylon solution solvent is 35% or more. If the insolubility is lower than 35%, it absorbs moisture under high temperature and high humidity, and it is easy to deteriorate between the upper layer of the undercoating layer and the base material. As a result, the charge injection blocking performance of the undercoat layer is impaired. The insolubility can be set to a predetermined value by appropriately setting the drying temperature and the drying time.

The thickness of the undercoat layer is 0.05 μm to 10 μm, particularly 0.1 μm to
It is preferable to set it in the range of 2 μm.

A photosensitive layer is formed on the undercoat layer. When the photosensitive layer has a single-layer structure, a known material in which a photosensitive material is dispersed in a binder resin can be used.

When the photosensitive layer has a laminated structure of a charge generation layer and a charge transport layer, any of them may be provided on the undercoat layer.

The charge generation layer is obtained by dispersing a charge generation material in a binder resin, and a known charge generation material is used.
For example, azo dyes such as chlorodiane blue, anthantrone, quinone pigments such as pyrenequinone, quinocyanine pigments, perylene pigments, perinone pigments, indigo pigments, bisbenzimidazole pigments, copper phthalocyanines, phthalocyanine pigments such as vanadyl phthalocyanine, azulhenium salts, square Lithium pigments, quinacridone pigments and the like can be used.

As the binder resin of the charge generation layer, polystyrene resin,
Known materials such as polyvinyl acetal resin, acrylic resin, methacrylic resin, vinyl acetate resin, polyester resin, polyarylate resin, polycarbonate resin, and phenol resin are used.

The charge generation layer is formed by including a charge generation material in a solution of the binder resin and applying the charge generation material on the undercoat layer. As a solvent used for dispersion, methanol, ethanol, n-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve,
Commonly used organic solvents such as acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, dioxane, tetrahydrofuran, methylene chloride and chloroform can be used.

The thickness of the charge generation layer is generally 0.1 μm to 5 μm, preferably 0.2 μm to 2.0 μm.

The charge transport layer is obtained by dispersing a charge transport material in a binder resin.Examples of the charge transport material include polycyclic aromatic compounds such as anthracene, pyrene, and phenanthrene, or indole, carbazole, and imidazole. And the like, a compound having a nitrogen-containing heterocycle, a pyrazoline compound, a hydrazone compound, a triphenylmethane compound, a triphenylamine compound, an enamine compound, a stilbene compound, and the like. Further, as the binder resin, any resin may be used as long as it has a film-forming property, for example, polyester, polysulfone, polycarbonate,
Polymethyl methacrylate or the like is used.

The charge transport layer is prepared by dissolving the binder resin in a solvent and adding the above-described charge transport material thereto to form a solution having a thickness of 5 μm.
It is formed by applying so as to have a thickness of about 30 μm. As the solvent, usually used are aromatic hydrocarbons such as benzene, toluene and xylene; ketones such as acetone and 2-butanone; halogenated hydrocarbons such as methylene chloride, monochlorobenzene and chloroform; tetrahydrofuran and ethyl ether. Organic solvents can be used.

Examples Hereinafter, the present invention will be described with reference to Examples and Comparative Examples.
In addition, "part" means "part by weight".

COMPARATIVE EXAMPLE 1 1 part of 30% N-methoxymethylated 8 nylon was dissolved in a mixed solvent consisting of 3.8 parts of methanol, 2.6 parts of n-butanol and 0.6 part of water, and the solution was applied to an aluminum cylindrical surface having a diameter of about 85 mm. The coating was applied by a dip coating method, dried for about 5 minutes, and then dried at 100 ° C. for 5 minutes to form an undercoat layer having a thickness of about 1.0 μm. The insolubility of the formed undercoat layer with respect to the solvent was measured using a Soxhlet extractor and found to be about 4%.

On this undercoat layer, a dispersion liquid in which 8 parts of brominated anthuanthrone was dispersed in a solution composed of 1 part of polyvinyl butyral and 90 parts of cyclohexanone was applied by a dip coating method, and dried at 100 ° C. for 10 minutes. A charge generation layer having a thickness of about 0.8 μm was formed. Further, on this charge generation layer, a charge transport layer was formed as follows. That is, N, N'-diphenyl-N, N'-bis (3-methylphenyl)-[1,
1′-biphenyl] -4,4′-diamine (5 parts) was used as a charge transporting agent and dissolved together with 6 parts of polycarbonate Z resin in 40 parts of monochlorobenzene, and the resulting solution was applied by a dip coating method. After drying for a time, a charge transport layer having a thickness of 20 μm was formed.

The electrophotographic photoreceptor thus formed is subjected to a surface potential
After being charged to 800 V, image exposure, development, transfer, and fixing were performed according to a normal electrophotographic method, and repeated copying was continued. Under an environment of 28 ° C. and 85% RH, 9,000 to 10,000,
At the time when about 0 sheets were copied, countless minute white spots were generated in the entire halftone copy image having an optical density of 0.3 or more.

When the humidity decreases, the number of sheets before white spots begin to increase increases to about 15,000 at 25 ° C and 50%.
When a copy operation in an environment of 50 ° C. and 50% RH and a copy operation in an environment of 28 ° C. and 85% RH were repeatedly performed in a state where approximately half were mixed, the number of copies occurred from about 12,000 sheets.

The white spots described above are different from the ones generated by nuclei that are mixed in each layer of the photoreceptor, and are different from the conductive bases due to the moisture absorbed by impurities slightly contained in the undercoat layer. It is thought to be caused by the occurrence of a reaction and the generation of fine portions with reduced charge injection stopping ability from the conductive substrate to be held by the undercoat layer.

Example 1 As an undercoat layer, the same solution as in Comparative Example 1 was used, applied on an aluminum cylinder in the same manner and dried, and then the drying temperature was increased to 135 ° C. and dried for 10 minutes.
An undercoat layer having a thickness of about 1.0 μm was formed. The insolubility of the formed undercoat layer with respect to the solvent was measured using a Soxhlet extractor and found to be about 35%.

A charge generation layer and a charge transport layer were formed on the formed undercoat layer in the same manner as in Comparative Example 1, and an electrophotographic photoreceptor was formed.

When the white spot generation state of the electrophotographic photosensitive member was evaluated in the same manner as in Comparative Example 1, the copy operation in an environment of 25 ° C. and 50% RH and the copy operation in an environment of 28 ° C. and 85% RH were as follows. As a result of repeatedly performing the copy operation in a state where the mixture was almost half each, it was confirmed that white spots did not occur up to about 17,000 sheets.

Example 2 Except for drying the undercoat layer at a temperature of 140 ° C. for 10 minutes,
An electrophotographic photosensitive member was formed in the same manner as in Example 1. The solvent insolubility of the undercoat layer was 40%.

When the white spot generation state of this electrophotographic photosensitive member was evaluated in the same manner, no white spot was generated up to about 25,000 sheets.

Example 3 Except for drying the undercoat layer at a temperature of 150 ° C. for 10 minutes,
An electrophotographic photosensitive member was formed in the same manner as in Example 1. The solvent insolubility of the undercoat layer was 55%.

When the white spot generation state of this electrophotographic photosensitive member was evaluated in the same manner, no white spot was generated up to about 50,000 sheets.

As is clear from the comparison between the above Examples and Comparative Examples,
When the solvent insolubility of the undercoat layer is 35% or more, an electrophotographic photosensitive member having a practically sufficient life can be obtained.

Effect of the Invention Since the electrophotographic photoreceptor of the present invention is provided with an N-methoxymethylated nylon layer cross-linked to a specific state as an undercoat layer as described above, the electrophotographic photoreceptor is excellent even in a high humidity environment. A copy image of high quality can be obtained, and even if the electrophotographic photosensitive member is used for a long period of time, the obtained copy image does not have spot-like white spots.

[Brief description of the drawings]

The drawing is a schematic view of the electrophotographic photosensitive member of the present invention. 1 ... charge transport layer, 2 ... charge generation layer, 3 ... undercoat layer, 4 ... conductive support.

──────────────────────────────────────────────────続 き Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G03G 5/00-5/16

Claims (1)

(57) [Claims] 1. An electrophotographic photoreceptor comprising a conductive support, an undercoat layer and a photosensitive layer sequentially laminated, wherein the undercoat layer comprises N
-A coating film formed by applying a solution of methoxymethylated nylon is thermally crosslinked at a temperature of 135 ° C to 150 ° C, and the solvent used for the solution of N-methoxymethylated nylon is An electrophotographic photoreceptor having an insoluble ratio of 35% or more.