JPS63216059A - Laminated electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To stabilize characteristics against environiental atmosphere, especially, humidity or the like by using polyvinyl alcohol cross-linked by an inorganic copper salt or iron salt for an undercoat layer. CONSTITUTION:The polyvinyl alcohol cross-linked by an inorganic copper (II) or iron (II) salt is used for the undercoat layer formed between a conductive substrate and a photosensitive layer. Said salt is used, preferably, in an amount of 5-10wt.% of said polyvinyl alcohol, thus permitting oxidation, such as discoloration, due to oxidation not to occur on the conductive substrate even under high humidity, and moreover, change of electrophotographic characteristics, especially, sensitivity and residual potential, to be made very little by variance of humidity.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an electrophotographic photoreceptor, and more particularly to an undercoat layer of a laminated electrophotographic photoreceptor.

BACKGROUND OF THE INVENTION Conventionally, inorganic photoconductive substances such as selenium have been widely used in electrophotographic photoreceptors.

In recent years, some organic photoconductive materials have been put into practical use, taking advantage of their advantages such as ease of film formation and production of photoreceptors.

In particular, in the case of organic photoreceptors, a laminated photoreceptor is generally used, which is functionally separated into a charge generation layer containing a pigment or dye that generates charge carriers upon exposure to light, and a charge transport layer that moves the charges in the direction of the electric field. It is being

The thickness of the charge generation layer is preferably 0.5 μm in order to maintain the electrophotographic characteristics of the photoreceptor and its repeatability.
It is also known that it is necessary to:

However, when such a thin charge-generating layer is applied directly onto a conductive support, slight imperfections on the support surface, such as dirt or scratches, tend to cause uneven film thickness such as repellency or unevenness. .

Therefore, when a charge generation layer is formed on a conductive support, a resin layer is generally provided in the middle thereof. This resin layer is generally called an undercoat layer or an intermediate layer.

Materials for forming this undercoat layer include:
It is necessary that the charge generation layer coated thereon is not attacked by the solvent used in the coating solution, and hydrophilic resins such as polyamide, polyvinyl alcohol, casein, and methylcellulose are known.

Problems to be Solved by the Invention However, when such a hydrophilic resin is used in the undercoat layer, there is a drawback that the electrophotographic properties of the resulting photoreceptor are greatly influenced by the environmental atmosphere, especially humidity. .

In view of the above-mentioned problems, the present invention provides a laminated electrophotographic photoreceptor whose characteristics are stable against environmental atmosphere, especially humidity.

Means for Solving the Problems In order to solve the above problems, the laminated electrophotographic photoreceptor of the present invention consists of using polyvinyl alcohol cross-linked with an inorganic copper salt or an inorganic iron salt for the undercoat layer. .

That is, an ammonia alkaline solution containing an inorganic copper salt or a neutral polyvinyl alcohol aqueous solution containing an inorganic iron salt is applied as an undercoat layer onto a conductive support, and is dried and crosslinked. Thereafter, a charge generation layer and a charge transport layer are sequentially laminated thereon to obtain the laminated electrophotographic photoreceptor of the present invention.

The inventors applied an ammonia alkaline solution containing an inorganic copper salt or a neutral polyvinyl alcohol aqueous solution containing an inorganic iron salt to the undercoat layer, dried and crosslinked the undercoat layer, and formed a charge generation layer and a charge transport layer thereon. When laminated sequentially, the resulting photoreceptor has less influence on electrophotographic properties, especially sensitivity and residual potential, due to changes in atmospheric humidity than when non-crosslinked polyvinyl alcohol is used, or It has been found that even when the photoreceptor is left under high humidity, no discoloration is observed on the conductive support, such as the aluminum surface, in contact with the undercoat layer.

This is because the insulation resistance of the undercoat layer changes depending on the amount of moisture absorbed by the undercoat layer under atmospheric humidity, which affects sensitivity, and the absorbed moisture promotes oxidation on the surface of the conductive support. It seems that there are.

The crosslinking agent for polyvinyl alcohol used in the undercoat layer is a water-soluble divalent inorganic copper salt such as cupric sulfate or cupric chloride, or a water-soluble divalent inorganic copper salt such as ferric sulfate or ferric chloride. Any inorganic iron salt of high valence may be used. The amount of inorganic copper salt or inorganic iron salt used is 1 part polyvinyl alcohol.
It is preferably 5 to 10 parts by weight per 00 parts by weight.

EXAMPLE Hereinafter, an example of the present invention will be explained, but the present invention is not limited to the combination shown in the following example.

[Example 1] 5 parts by weight of polyvinyl alcohol (trade name: Gohsenol 0L-05, manufactured by Nippon Gosei Co., Ltd.) are dissolved in 100 parts by weight of distilled water. On the other hand, an aqueous solution in which 0.25 parts by weight of crystalline cupric sulfate was dissolved in a minimum amount of aqueous ammonia was added to the polyvinyl alcohol solution while stirring, and then the precipitated polymer was dissolved in a minimum amount of aqueous ammonia. to dissolve. After drying this on an aluminum plate, the film thickness is 0.2μ.
Rotate the coating so that it becomes m. After coating, it was dried at 100° C. for 1 hour to form a crosslinked polyvinyl alcohol as an undercoat layer.

Next, 1 part by weight of butyral resin (manufactured by Sekisui Chemical Co., Ltd., trade name Nislex E3H-3) was dissolved in 40 parts by weight of ethylene glycol monomethyl ether, and ε-type copper phthalocyanine (manufactured by Toyo Ink Mfg. Co., Ltd., trade name Rio Photon EAR) was dissolved in 40 parts by weight of ethylene glycol monomethyl ether. PC [Liopho
ton ERPC]) was added and dispersed. This dispersion was spin-coated onto the surface of the undercoat layer so that the film thickness after drying was 0.3 μm, and the coating was applied at 100°C for 10 minutes.
A charge generation layer was formed by drying for a period of time. Next, 1 part by weight of p-diethylaminobenzal-N,N-diphenylhydrazone and 1 part by weight of an acrylic resin (trade name BR-50, manufactured by Mitsubishi Rayon Co., Ltd.) were dissolved in 4 parts by weight of toluene. This liquid was applied onto the charge generation layer with a blade and dried at 80° C. for 1 hour to form a charge transport layer with a thickness of 18 μm.

The thus obtained laminated electrophotographic photoreceptor was tested in an electrostatic copying paper tester (EP A-8 manufactured by Kawaguchi Electric Seisakusho Co., Ltd.).
100), the surface potential VO (V) when charged at -5.5 KV, the surface potential V+ (V) when left in the dark for 1 second, and the surface when exposed to 5 lux white light. The exposure amount E 1/2 (1ux-sec) required for the potential to attenuate to 1/2 Vl (V) was measured. The measurement results are shown in Table 1.

Table 1 also shows the appearance of the photosensitive plate when it was left at 40° C. and 90% relative humidity for 10 days.

[Example 2] For a comparative experiment, a sample was prepared using non-crosslinked polyvinyl alcohol for the undercoat layer.

That is, an undercoat layer was prepared in the same manner as in Example 1 using a polyvinyl alcohol coating solution that did not contain crystalline cupric sulfate or aqueous ammonia, and after drying at 100° C. for 1 hour, a charge generation layer of the same composition and a charge generation layer were formed. Transport layers were laminated sequentially. The electrophotographic properties and the appearance when left under high humidity of the obtained photosensitive plate were examined in the same manner as in the examples. The results are also shown in Table 1.

[Example 3] The same composition was used, except that an aqueous solution of crystalline ferric sulfate was used instead of the ammonia alkaline aqueous solution of crystalline cupric sulfate used in Example 1, and it was applied on an aluminum plate, dried, and heated. An undercoat layer having a thickness of 0.4 μm was prepared by crosslinking the resin.

Next, 1 part by weight of butyral resin (manufactured by Sekisui Chemical Co., Ltd., trade name: Nislex BH-3) was dissolved in 40 parts by weight of ethylene glycol monomethyl ether, and τ-type metal-free phthalocyanine (manufactured by Toyo Ink Manufacturing Co., Ltd., trade name: Rio Photon TP) was dissolved. H 278 (Liopho
ton TPH-278)'') was added and dispersed. This dispersion was spin-coated onto the surface of the undercoat layer so that the film thickness after drying was 0.3 μm.
A charge generation layer was formed by drying at 80''C for 1 hour.

Next, 1 part by weight of hydrazone represented by the following structural formula and 1 part by weight of polycarbonate resin (trade name: Tubarex 7030A, manufactured by Mitsubishi Kasei Corporation) were dissolved in 3 parts by weight of methylene dichloride and 3 parts by weight of ethylene dichloride. This liquid was applied onto the charge generation layer with a blade and dried at 80° C. for 1 hour to form a charge transport layer with a thickness of 14 μm.

The thus obtained laminated electrophotographic photoreceptor was placed in an electrostatic copying paper test bag W (EP A 7 manufactured by Kawaguchi Electric Seisakusho Co., Ltd.).
8100) when charged at -5.5 KV. (■), surface potential V+ (V) when left in a dark place for 1 second, exposure amount required for the surface potential to attenuate to 1/2 v l (V) when exposed to 5 lux white light E 1/2 (lux・5e
c) The surface potential VR2 (V) was measured after 2 seconds of exposure.

The same sample was also heated at 40°C and 90% relative humidity for 1
The same characteristics were measured after leaving it for several months. The measurement results are shown in Table 2.

[Example 4] For a comparative experiment, a sample was prepared using uncrosslinked polyvinyl alcohol as the undercoat i.

That is, an undercoat layer was created using a polyvinyl alcohol coating solution that did not contain crystalline ferric sulfate, and after drying at 80° C. for 1 hour, a charge generation layer and a charge transport layer having the same composition as in Example 3 were sequentially laminated. did. The electrophotographic properties of the obtained photosensitive plate were determined in the same manner as in Example 3, and the temperature was 40°C and the relative humidity was 90%.
The characteristics were investigated after being left in an atmosphere for one month. The results are also shown in Table 2.

Table 1 Table 2 Effects of the Invention As above, the laminated electrophotographic photoreceptor of the present invention has been explained in detail. By using a crosslinked hydrophilic resin as an undercoat layer between the photosensitive layer and the photosensitive layer, oxidation such as discoloration does not occur on the conductive support even under high humidity, and the electron Changes in photographic properties, especially sensitivity and residual potential, were extremely small.

Claims (2)

[Claims] (1) In a laminated electrophotographic photoreceptor in which a photosensitive layer consisting of a charge generation layer and a charge transport layer is provided on a conductive support,
A laminate characterized in that polyvinyl alcohol cross-linked with an inorganic salt selected from inorganic copper (II) salts and inorganic iron (II) salts is used for the undercoat layer between the conductive support and the photosensitive layer. type electrophotographic photoreceptor. (2) A laminated electrophotographic photoreceptor according to claim (1), characterized in that a phthalocyanine pigment is used in the charge generation layer.