JPH0827545B2 - Electrophotographic photoreceptor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electrophotographic photoreceptor, and more specifically, an improvement of an intermediate layer in an electrophotographic photoreceptor that is repeatedly used in a PPC copying machine, a laser beam printer, a digital copying machine and the like. Regarding

[Prior Art] Generally, an electrophotographic photosensitive member that is repeatedly used (hereinafter sometimes simply referred to as a "photosensitive member") is required to have a good chargeability (to prevent unnecessary charge injection and to be suitable). An intermediate layer is provided between the substrate and the photosensitive layer with a resin having a relatively low resistance, for the purpose of maintaining charge acceptance), and further for improving the adhesion of the photosensitive layer to the substrate. .

As the resin for the intermediate layer, (a) casein, water-soluble resin such as polyvinyl alcohol, (b) polyamide resin such as nylon and copolymerized nylon, and (c) light or thermosetting resin have been used. In the photoconductor on which the intermediate layer is formed, there is a tendency that the intermediate layer has a high resistance at low humidity to increase the residual electric charge, resulting in a decrease in sensitivity.

As a means for solving such inconvenience, addition of a conductive pigment such as indium oxide, tin oxide or carbon to the intermediate layer (JP-A-58-93063) or a conductive polymer (JP-A-58). -95744 publication) and the like have been proposed. However, in the former case, the charging property is reduced, so a second intermediate layer consisting of resin alone must be formed between the conductive pigment-containing intermediate layer and the photosensitive layer, and in the latter case The performance is not deteriorated, but there is a problem in practical use because the sensitivity is lowered.

Furthermore, in a so-called laminated type photoreceptor in which the photosensitive layer is a laminated structure of a charge generation layer and a charge transport layer, in order to prevent moire due to multiple reflection between the substrate and the surface of the charge transport layer, an intermediate layer is formed. It has also been proposed to include in the layer a substance that scatters light. However, even in the case of this photoconductor, a decrease in charging property and an increase in residual potential are recognized by repeated use, and improvement is required similarly to the photoconductor.

[Purpose] An object of the present invention is to provide an electrophotographic photosensitive member which eliminates the humidity dependency (increase of residual potential at low humidity) without affecting the characteristics of the photosensitive member and further improves the characteristic deterioration in repeated use. It is a thing. Another object of the present invention is to provide an organic photosensitive member which is effective for repeated use, in which the photosensitive layer and the substrate are firmly adhered to each other via the intermediate layer, and therefore the mechanical strength is strong and further moire is not generated. (Especially laminated photoconductor)
Is provided.

[Structure] In the electrophotographic photosensitive member of the present invention, which has an intermediate layer between the conductive substrate and the photosensitive layer and is repeatedly used, the intermediate layer contains a conductive polymer and an inorganic white pigment. Is characterized by.

By the way, although the present inventor suppresses the increase in residual potential in a low humidity environment when a conductive polymer is added to the intermediate layer resin, the decrease in sensitivity observed on the other hand is eliminated by further containing an inorganic white pigment. I confirmed to go. Moreover, it was confirmed that the addition of such an inorganic white pigment can prevent the occurrence of moire. The present invention has been completed based on such findings.

The present invention will be described in more detail below. As described above, the photoreceptor of the present invention is formed by laminating an intermediate layer, a charge generation layer and a charge transport layer in this order on a conductive substrate, and the intermediate layer is the charge generation layer. It is designed to be in direct contact with. As the conductive substrate, a metal such as aluminum, nickel or stainless steel; a plastic in which a conductive pigment such as carbon is dispersed;
Examples thereof include an insulating support (such as a plastic or a plastic film) on which a metal is vapor-deposited or a conductive coating is applied.

As the conductive polymer used for the intermediate layer, a polymer containing a sodium sulfonate group, an anionic conductive polymer represented by polystyrene sulfonate which is a polymer containing an ammonium sulfonate group, and a quaternary ammonium salt. A cationic conductive polymer represented by a polymer containing a base can be used.

The inorganic white pigment used in the intermediate layer is titanium dioxide, zinc oxide, zinc sulfide, lead white, lithopone, etc., and has a relatively high refractive index of 1.9 or more in visible light or near infrared light. is there.

The intermediate layer may be composed of only the conductive polymer and the inorganic white pigment described above, but may contain a conventionally used binder (low resistance resin). However, the binder which may be used here is preferably water- or alcohol-soluble one in view of the fact that it is soluble in the solvent for dissolving the conductive polymer and is not attacked by the photosensitive layer forming liquid applied on the intermediate layer. . Specifically, polyvinyl alcohol, sodium polyacrylate, CMC, casein, sodium alginate, nylon, copolymer nylon,
Examples include alkoxymethylated nylon.

To form an intermediate layer using these materials, a conductive polymer, an inorganic white pigment, a solvent and, if necessary, the binder are placed in a ball mill or the like to disperse the pigment well, and the resulting dispersion is placed on a conductive substrate. It can be applied to and dried.
The thickness of the intermediate layer is about 0.3 to 20 μm.

The ratio of the conductive polymer, the inorganic white pigment and the binder cannot be uniformly determined because it depends on the materials used, but the total of the conductive polymer and the binder is 1
When it is defined as parts, the weight ratio of the inorganic pigment is suitably 0.05 to 10 parts. Further, the ratio of the conductive polymer to the binder cannot be uniformly determined, but the ratio of the conductive polymer to 1
When the amount of the binder is, the weight ratio of the binder is 0 to 200 parts, preferably 10 to 200 parts.

The charge generation layer is an azo pigment, a phthalocyanine pigment, an indigo pigment, a perylene pigment, a square pigment,
A charge generating substance such as selenium powder, selenium alloy powder, amorphous silicon powder, zinc oxide powder, and cadmium sulfide powder is dispersed in a binder resin solution such as polyester, polycarbonate, polyvinyl butyral, and acrylic resin, and this is dispersed on the intermediate layer. It is formed by coating.
The appropriate thickness of the charge generation layer is 0.01 to 2 μm.
The charge transport layer is formed of an α-phenylstilbene compound (JP-A-58)
-198043), hydrazone compounds (JP-A-55-55)
No. 46760) and a charge transporting substance such as polyester, polysulfone, polycarbonate, polymethacrylic acid esters, polystyrene, etc. are dissolved in the film-forming resin, and the thickness is 10 to 30 μm on the charge generating layer.
It only has to be applied to a degree. The film-forming resin is used here because the charge-transporting substance generally has a low molecular weight and is poor in film-forming property by itself.

The photoreceptor thus produced is suitable for repeated use, and if necessary, a protective layer similar to the conventional one can be provided on the surface of the photosensitive layer.

 Next, examples and comparative examples will be shown.

Example 1 Alcohol-soluble copolymer nylon (Toray CM-400
0) 10 g was dissolved in 100 g of methanol. 0.8 g of a conductive polymer (polydimethyldiaryl ammonium chloride, CP-280 manufactured by Calgon, Inc., USA) and 5 g of titanium oxide powder (Taipaque R-670 manufactured by Ishihara Sangyo Co., Ltd.) were added, and the mixture was dispersed in a ball mill for 12 hours. . 0.2m of the obtained coating liquid
The aluminum plate (conductive substrate) having a thickness of m was applied by dipping and then dried at 110 ° C. for 5 minutes to form an intermediate layer having a thickness of about 2 μm.

On the other hand, polyester resin (Byron 20 manufactured by Toyobo Co., Ltd.
0) Dissolve 5g in 150g of cyclohexanone, and add the following structural formula Add 10 g of the bisazo pigment represented by
Time dispersion was performed. Subsequently, 210 g of cyclohexanone was added to this product and dispersed for 3 hours, then taken out of the container and diluted with cyclohexanone while stirring so that the solid content was 1% by weight to prepare a charge generation layer forming liquid.

This solution was applied onto the intermediate layer by dip coating and dried at 120 ° C. for 5 minutes to form a charge generation layer having a thickness of about 0.3 μm.

In addition, polycarbonate resin (Tanjin Panlite K-
1300) 12 g was dissolved in 90 g of tetrahydrofuran, and the following structural formula was added to it. A solution in which 7 g of the charge-transporting substance represented by is dissolved is dip-coated on the charge-generating layer, dried at 120 ° C. for 15 minutes, and then dried to about 18 μm.
An m-thick charge transport layer was formed to prepare a laminated electrophotographic photoreceptor.

Comparative Example 1-a A comparative photoconductor was prepared in exactly the same manner as in Example 1 except that the titanium oxide powder was removed from the intermediate layer.

Comparative Example 1-b A comparative photoreceptor was prepared in the same manner as in Example 1 except that the conductive polymer was removed from the intermediate layer.

Example 2 10 g of alcohol-soluble copolymer nylon (Daiamide X-1874 manufactured by Daicel Chemical Industries, Ltd.) was dissolved in 100 g of methanol. Conductive polymer (styrene vinylbenzyl trimethyl ammonium chloride and N- [2- (N, N, N
-Trimethylammonio) ethyl] -N, N-dimethyl-
0.7 g of a copolymer with N-vinylbenzylammonium chloride, Chemistat 6300 manufactured by Sanyo Kasei Co., Ltd. and 7 g of zinc sulfide powder (manufactured by Shimakyu Chemical Co., Ltd.) were added, and the mixture was dispersed in a ball mill for 12 hours. After dipping the obtained coating solution on the surface of an aluminum plate (conductive substrate) with a thickness of 0.2 mm, 110
It was dried at 0 ° C. for 5 minutes to form an intermediate layer having a film thickness of about 3 μm.

On the other hand, 5 g of the same bisazo pigment as in Example 1 was added to 100 g of tetrahydrofuran and dispersed by a ball mill for 48 hours.
Subsequently, 400 g of tetrahydrofuran was added to this and stirred to prepare a charge generation layer forming liquid.

This solution was applied onto the intermediate layer by dip coating and dried at 120 ° C. for 5 minutes to form a charge generation layer having a thickness of about 0.3 μm.

In addition, polycarbonate resin (Tanjin Panlite K-
1300) 12 g was dissolved in 90 g of tetrahydrofuran and the following structural formula A solution prepared by dissolving 7 g of the charge transport material represented by is applied onto the charge generation layer by dip coating, dried at 120 ° C. for 15 minutes, and then dried to about 20 μm.
An m-thick charge transport layer was formed to prepare a laminated electrophotographic photoreceptor.

Comparative Example 2-a A comparative photoreceptor was prepared in exactly the same manner as in Example 2 except that the zinc sulfide powder was removed from the intermediate layer.

Comparative Example 2-b A comparative photoconductor was prepared in exactly the same manner as in Example 2 except that the conductive polymer was removed from the intermediate layer.

Example 3 To 100 g of milk casein (manufactured by Kanto Chemical Co., Inc.), 100 g of water and 0.5 ml of concentrated ammonia water (concentration 38%) were added, and stirred to 70
The casein was dissolved by heating to ℃. Conductive polymer (ammonium polystyrene sulfonate, Kanebo NSC
VERSA-TL125) 1.0g and zinc oxide (Sakai Chemical Co., Ltd.) 5.0g
And were added, and the mixture was dispersed in a ball mill for 5 hours. 0.2mm thick aluminum plate (conductive substrate)
After dip coating on the surface, it was dried at 120 ° C. for 5 minutes to form an intermediate layer having a film thickness of about 2.5 μm.

Butyral resin (Sekisui Chemical's S-REC BL-
S) 5 g was dissolved in cyclohexanone 150 g, and the following structural formula Add 10 g of the trisazo pigment represented by
Dispersion was carried out for 8 hours. Subsequently, 210 g of cyclohexanone was added to this product and dispersed for 3 hours, then taken out of the container and diluted with cyclohexanone while stirring so that the solid content was 1.5% by weight to prepare a charge generation layer forming liquid.

This solution was applied onto the intermediate layer by dip coating and dried at 120 ° C. for 5 minutes to form a charge generation layer having a thickness of about 0.3 μm.

Further, a charge transport layer similar to that in Example 1 was formed on this charge generation layer to prepare a laminated electrophotographic photoreceptor.

Comparative Example 3-a A comparative photoconductor was prepared in exactly the same manner as in Example 3 except that zinc oxide was removed from the intermediate layer.

Comparative Example 3-b A comparative photoconductor was prepared in exactly the same manner as in Example 3 except that the conductive polymer was removed from the intermediate layer.

Example 4 Alcohol-soluble copolymer nylon (CM-800 manufactured by Toray Industries, Inc.
0) 10 g was dissolved in 100 g of methanol. To this, 1 g of a conductive polymer (sodium polystyrene sulfonate, Chemist 6120 manufactured by Sanyo Kasei Co., Ltd.) and 5 g of titanium oxide powder (A-100 manufactured by Ishihara Sangyo Co., Ltd.) were added, and the mixture was dispersed in a ball mill for 12 hours. The obtained coating solution was applied onto the surface of an aluminum plate (conductive substrate) having a thickness of 0.2 mm by dip coating, and then at 5 ° C at 110 ° C.
After drying for a minute, an intermediate layer having a film thickness of about 2 μm was formed.

Then, a charge generation layer similar to that in Example 3 was formed on this intermediate layer.

In addition, polycarbonate resin (Tanjin Panlite K-
1300) 12 g was dissolved in 90 g of tetrahydrofuran and the following structural formula A solution prepared by dissolving 7 g of the charge transport material represented by is applied onto the charge generation layer by dip coating, dried at 120 ° C. for 15 minutes, and then dried to about 20 μm.
An m-thick charge transport layer was formed to prepare a laminated electrophotographic photoreceptor.

Comparative Example 4-a A comparative photoreceptor was prepared in exactly the same manner as in Example 4 except that the titanium oxide powder was removed from the intermediate layer.

Comparative Example 4-b A comparative photoreceptor was prepared in the same manner as in Example 4 except that the conductive polymer was removed from the intermediate layer.

These samples (4 types of photoconductors of the present invention, 8 comparative photoconductors)
The characteristics of the photoconductor of No. 1) were measured using an electrostatic paper analyzer SP-428 (manufactured by Kawaguchi Electric Co., Ltd.) under the following conditions.

Further, charging and exposure under the above conditions were simultaneously performed for 30 minutes to fatigue the photoconductor, and then the photoconductor characteristics were measured.

The above results are shown in Table-1. However, (2) Sensitivity: the amount of exposure required to reduce the potential after exposure to 1/10. (3) Residual potential: The potential after 15 seconds of exposure.

[Effect] As is apparent from the description of the examples, by incorporating a specific inorganic white pigment and a conductive polymer in the intermediate layer in combination, a photoreceptor having high sensitivity and less fatigue in a low humidity environment or a room temperature environment can be obtained. To be

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kiyoshi Masuda 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (72) Hirofumi Yamanami 1-3-6 Nakamagome, Ota-ku, Tokyo Shares Inside Ricoh Company (72) Inventor Satomi Mochizuki 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company Ltd. (56) References JP-A-58-95744 (JP, A) JP-A-60-170861 (JP) , A)

Claims (1)

[Claims] 1. An electrophotographic photosensitive member comprising an electrically conductive substrate, an intermediate layer, a charge generating layer and a charge transport layer, which are laminated in this order, and the intermediate layer is in direct contact with the charge generating layer in an electrophotographic photoreceptor that is repeatedly used. And an intermediate layer containing a conductive polymer and an inorganic white pigment.