JPH0830006A - Electrophotographic photoreceptor - Google Patents

Abstract

(57) [Summary] [Object] The present invention provides good adhesion between a photosensitive layer and an undercoat layer of an electrophotographic photosensitive member, increases the residual potential after exposure, and delays the rise of charging. It is an object of the present invention to provide an electrophotographic photosensitive member which is free from problems and does not cause a reduction in image density in the quality of a copied image, and can obtain a copy having no grain background stain. The present invention relates to an electrophotographic photoreceptor comprising a conductive substrate, and an undercoat layer and an electrophotographic photosensitive layer laminated on the layer, wherein the undercoat layer contains a pigment and a resin. The electrophotographic photosensitive member is characterized in that the resin content concentration with respect to the pigment in the vertical direction of the substrate has a gradient, and the resin content concentration is large on the conductive substrate side. Also, after providing an undercoat layer containing a pigment and a resin on a conductive substrate, by treating the undercoat layer with an organic solvent that dissolves only the resin in the undercoat layer, the vertical direction of the conductive substrate can be improved. The electrophotographic photosensitive member is characterized in that the resin content concentration with respect to the pigment in (1) has a gradient.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an electrophotographic photosensitive member having an undercoat layer on a conductive substrate.

[0002]

2. Description of the Related Art Generally, an electrophotographic photosensitive member is obtained by improving adhesion between a conductive substrate and a photosensitive layer, improving adhesion between the substrate and the photosensitive layer, improving coatability of the photosensitive layer, or improving charge injection property from the substrate to the photosensitive layer. An undercoat layer mainly composed of resin is usually provided for the purpose of improving the photosensitivity. For example, JP-A-59
JP-A-84257 proposes an electrophotographic photosensitive member having a resin layer in which a pigment such as TiO ₂ or SnO ₂ is dispersed as an undercoat layer. According to such a photosensitive member, white dots are formed in a black image. That is, it is possible to form a good image that does not occur. However, in the case of an ordinary undercoat layer in which a pigment is simply dispersed in a resin, which aims to suppress charge injection and maintain uniform chargeability of a photosensitive layer, it is presumed that local charge injection is the cause. However, there is a problem that the obtained image is stained. As a means for solving such a problem, it is conceivable to increase the thickness of the undercoat layer or increase the composition ratio of the resin, but with such a solution, the residual potential after exposure becomes large, It was confirmed that new problems such as a slow rise of charging and a decrease in adhesive strength occurred.

[0003]

SUMMARY OF THE INVENTION According to the present invention, the adhesiveness between the photosensitive layer and the undercoat layer of the electrophotographic photosensitive member is good, the residual potential after exposure becomes large, and the rise of charging is delayed. (EN) An electrophotographic photosensitive member which has no problem and does not cause a reduction in image density in the quality of a copied image and can obtain a copy having no grain background stain.

[0004]

The present invention provides an electrophotographic photosensitive member comprising a conductive substrate, an undercoat layer and an electrophotographic photosensitive layer laminated on the layer, wherein the undercoat layer comprises a pigment. An electrophotographic photosensitive member comprising a resin, having a gradient in the resin content concentration relative to the pigment in the vertical direction of the substrate, and having a large resin content concentration on the side of the conductive substrate. Also, after providing an undercoat layer containing a pigment and a resin on a conductive substrate, by treating the undercoat layer with an organic solvent that dissolves only the resin in the undercoat layer, the vertical direction of the conductive substrate can be improved. The electrophotographic photosensitive member is characterized in that the resin content concentration with respect to the pigment in (1) has a gradient. In another embodiment, after an undercoat layer containing a pigment and a thermosetting resin is provided on a conductive substrate, an organic solvent that dissolves only the thermosetting resin monomer is used during the curing of the thermosetting resin. The electrophotographic photosensitive member is characterized in that the concentration of the resin with respect to the pigment in the vertical direction of the conductive substrate is made to have a gradient by treating the coating layer and then proceeding with heat curing.

The electrophotographic photosensitive member is basically composed of a single-layer photosensitive layer containing a photoconductive substance or a laminated structure of two or three layers containing a charge transporting layer and a charge generating layer on a conductive substrate. As described above, an undercoat layer mainly composed of a resin is used for the purpose of improving the adhesiveness between the substrate and the photosensitive layer, improving the coating property of the photosensitive layer, or improving the photosensitive property by improving the charge injection property from the substrate to the photosensitive layer. Is provided. The conductive substrate of the electrophotographic photoreceptor is a metal or alloy such as Al, Ni, Fe, Cu, Au. Or polyester, polyethylene terephthalate, polycarbonate, phenolic resin,
On an insulating substrate such as polyimide or glass, Al, Ag,
A thin film of a metal such as Au or a conductive material such as In ₂ O ₃ or SnO ₂ is used. Between the conductive substrate and the photosensitive layer, for the purpose of adhesion or charge retention,
An undercoat layer of resin or the like is provided.

As the photosensitive layer of the electrophotographic photosensitive member, a photosensitive layer containing dye-sensitized zinc oxide, selenium powder, phthalocyanine pigment, etc. in a binder resin, or an organic photoconductive substance is used. There is a type in which a charge generation layer that generates charge carriers by exposure and a charge transport layer that has the ability to move the generated charge carriers are laminated. In the detailed description of the electrophotographic photosensitive member of the present invention, the above-mentioned laminated type will be described as an example. As the charge-generating pigment, a disazo type, a trisazo type, an azoxybenzene type, a benzimidazole type, and Known are ring quinone-based, indigoid-based, quinaceridone-based, phthalocyanine-based, perylene-based, methine-based, and the like, and any pigment can be used as long as it generates a charge by light irradiation. These charge generating pigments, alone or together with a binder resin, are dispersed in a solvent with a disperser such as a ball mill or an attritor to prepare a coating liquid, and then the coating liquid is applied onto the conductive substrate by dipping coating or spraying. The charge generation layer having a film thickness of 0.5 to 2 μm is formed by coating and drying by an appropriate method such as coating, knife coating and roll coating.

On the other hand, as the charge transport material, poly-N-vinylcarbazole compound, pyrazoline compound, α-phenylstilbene compound, hydrazone compound, diarylmethane compound, triphenylamine compound, divinylbenzene compound, full-vinyl compound. Known compounds such as olein compounds, anthracene compounds, oxadiazole compounds and diaminocarbazole compounds can be used. A coating solution is prepared by dissolving these charge-transporting substances in a solvent together with a resin such as polyurethane, polyester, epoxy resin, polycarbonate, polyvinyl butyral, and poly-N-vinylcarbazole.
By the same method as the formation of the charge generation layer described above,
Form a charge transport layer of -30 μm. The present invention provides a specific undercoat layer between the above-mentioned photosensitive layer of the electrophotographic photosensitive member and the conductive substrate, and the effect of suppressing local charge injection in the photosensitive member is mainly the substrate. It is presumed that it is at the interface between the undercoating layer and the undercoating layer, and the resin concentration of the undercoating layer as a whole is not changed, and the resin concentration is increased near the substrate to achieve the intended purpose. .

The thickness of the undercoat layer is preferably in the range of 0.01 to 10 μm. As the resin used for the undercoat layer, a general organic solvent is used in consideration of coating the photosensitive layer with a solvent thereon. The resin must have high solvent resistance. For example, polyvinyl alcohol, casein, water-soluble resins such as sodium polyacrylate, copolymer nylon,
Alcohol-soluble resin such as methoxymethylated nylon,
Examples thereof include polyurethane, melamine resin phenol resin, alkyd melamine resin, epoxy resin, and other curable resins that form a three-dimensional network structure.

Fine powder pigments such as titanium oxide, silica, alumina, zirconium oxide, tin oxide and indium oxide can be used in the undercoat layer for the purpose of reducing the residual potential for preventing moire. When the fine powder pigment is used, the resin is dissolved in order to increase the resin concentration in the undercoat layer near the substrate. At this time, it is considered that the fine powder pigment in the undercoat layer may fall off. In order to prevent such a phenomenon, it is preferable to use a plurality of resins having different solubilities in the processing solvent as the resin used for the undercoat layer. In the method of increasing the resin concentration in the undercoat layer of the present invention near the substrate, in particular, the method of using the above-mentioned curable resin, the curing of the curable resin is stopped midway, and an unreacted monomer that is easily dissolved in the solvent Take the method of dissolving only the ingredients. As a specific means for eluting the unreacted monomer component of the curable resin, the undercoat layer during curing is exposed to solvent vapor or immersed in a solvent to elute the monomer component. Then
The processing solvent in the undercoat layer is removed, and further curing is performed to form a desired undercoat layer. In the undercoat layer thus obtained, innumerable minute holes are observed on the surface of the layer, and these holes function as a structure effective for increasing the adhesive strength with the photosensitive layer provided thereon. Hereinafter, examples of the present invention will be given.
The present invention will be specifically described.

[0010]

【Example】

Example 1 Alkyd resin (Beckosol 1307-60-EL
30 parts by weight of Dainippon Ink and Chemicals, 20 parts by weight of melamine resin (Super Beckamine G-821-60, manufactured by Dainippon Ink and Chemicals), 90 parts by weight of titanium oxide powder (Tanbake CREL Ishihara Sangyo) Was further added, and 150 parts by weight of methyl ethyl ketone was further added, and the mixture was dispersed by a ball mill for 24 hours to prepare an undercoat layer coating solution. The coating liquid was applied on an aluminum cylindrical substrate, dried at 130 ° C. for 7 minutes, taken out, and the undercoat layer was immersed in a solvent (methyl ethyl ketone) to remove unreacted monomers. Then, it was dried again at 130 ° C. for 16 minutes to form a final undercoat layer.

Next, 14 parts by weight of polyvinyl butyral resin (S-REC BL-S manufactured by Sekisui Chemical Co., Ltd.) was dissolved in 150 parts by weight of cyclohexanone, and the following structural formula 1 was added thereto.

[Chemical formula 1] Structural formula 1 210 parts by weight of cyclohexanone was added and dispersed for 3 hours. Then, the dispersion was taken out into a container and diluted with cyclohexanone. The charge generation layer coating liquid thus obtained was applied onto the undercoat layer and dried at 130 ° C. for 20 minutes to form a charge generation layer of about 0.2 μm. A charge transport layer was further formed on the charge generation layer obtained as described above by the following procedure. 10 parts by weight of a polycarbonate resin (Panlite K1300 manufactured by Teijin Chemicals) and 0.002 parts by weight of silicone oil (KF-50 manufactured by Shin-Etsu Chemical Co., Ltd.) were dissolved in 83 parts by weight of methylene chloride, and the following structural formula 2 was added thereto.

Embedded image Structural formula 2 7 parts by weight of the charge transport material shown in (3) was added to prepare a charge transport layer forming liquid. Applying the forming liquid onto the charge generating layer,
After drying under conditions of 0 ° C. for 20 minutes, a charge transport layer having a thickness of about 20 μm was formed to prepare an electrophotographic photoreceptor of the present invention. The obtained electrophotographic photosensitive member was mounted on a CI-4 laser printer manufactured by C Tech Electronics Co., Ltd.
55% RH at ℃, 15% RH at 10 ℃, 90% at 30 ℃
When images were produced under each environment of RH, good images could be obtained. In addition, when 7,000 images were continuously output, no deterioration in image quality of the obtained images was observed.

Example 2 An electrophotographic photosensitive member was prepared in the same manner as in Example 1 except that the subbing layer of Example 1 was applied and exposed to a solvent vapor of methyl ethyl ketone instead of being immersed in methyl ethyl ketone after the first drying. Created. The obtained electrophotographic photosensitive member was mounted on a CI-4 laser printer manufactured by C Tech Electronics Co., Ltd., and 55% RH at 23 ° C. and 15% RH at 10 ° C.
When the image is displayed under each environment of 30% and 90% RH,
A good image could be obtained. Also, 7,0 continuously
When 00 images were output, no deterioration in image quality of the obtained image was observed.

Comparative Example 1 An electrophotographic photosensitive member was prepared in the same manner as in Example 1, except that the undercoat layer for comparison was prepared by coating the undercoat layer of Example 1 and then drying at 130 ° C. for 20 minutes. It was created. A comparative electrophotographic photosensitive member was manufactured by C-Tech Electronics Co., Ltd.
Mounted on 4 laser printer, 55% R at 23 ℃
When images were produced under the conditions of H, 10 ° C., 15% RH, and 30 ° C., 90% RH, only images with low image density and poor gradation were obtained especially under low temperature and low humidity. Also,
When 7,000 images were continuously output, image deterioration was recognized in each environment. Further, it was observed that the photosensitive layer was peeled off from the undercoat layer near the nail separating the paper and the photoreceptor.

Comparative Example 2 Alkyd resin (Bekkosol 1307-60-EL manufactured by Dainippon Ink and Chemicals, Inc.) of the undercoat layer forming liquid of Example 1
30 parts by weight was changed to 15 parts by weight, and 20 parts by weight of melamine resin (Super Beckamine G-821-60 manufactured by Dainippon Ink and Chemicals, Inc.) was changed to 10 parts by weight to prepare an undercoat layer coating solution. An electrophotographic photosensitive member was prepared in the same manner as in Example 1 except that the coating liquid was coated on a cylindrical aluminum substrate and dried at 130 ° C. for 20 minutes to form an undercoat layer. The obtained electrophotographic photosensitive member was mounted on a CI-4 laser printer manufactured by C Tech Electronics Co., Ltd., and 55% RH at 23 ° C., 15% RH at 10 ° C., 30 ° C.
When an image was produced under each environment of 90% RH, granular scum appeared on the entire surface of the printer paper. Further, when 7,000 images were continuously output, the background stain as described above became more severe.

The electrostatic characteristics of the electrophotographic photoconductors of Example 1 and the comparative photoconductor were measured by a dynamic method using a measuring device (SP-428 manufactured by Kawaguchi Denki Seisakusho).
As the measurement procedure, first, dark decay was performed for 20 seconds at an applied voltage of 6 KV, and exposure was performed for 30 seconds so that the surface illuminance was 6lux. The charging potential is the surface potential V2 after 2 seconds of charging, the sensitivity is the exposure amount E1 / 10 (lux · sec) required for the surface potential to reach from −800 V to −80 V after exposure, and the residual potential is the exposure time of 30 seconds. The subsequent surface potential V30 was measured. After that, irradiation with 5 lux of tungsten light having a color temperature of 2856 K and repeated charging fatigue with application of −6 KV for 3 hours were performed, and then V2, E1 / 10, V3 were again applied in the same manner as described above.
0 was measured. Table 1 shows the measurement results. From the results of Table 1, it was confirmed that the electrostatic characteristics of the example have almost the same characteristics as the comparative example.

[0016]

[Table 1]

[0017]

According to the electrophotographic photoreceptor of the present invention, since the undercoat layer has a gradient in the resin content concentration relative to the pigment in the vertical direction of the conductive substrate, the electrophotographic copying machine and electrophotographic process can be performed. An image from an image output device such as a printer used can be free from a reduction in image density and a background stain.

Claims (3)

[Claims] 1. An electrophotographic photoreceptor comprising a conductive substrate, an undercoat layer and an electrophotographic photosensitive layer laminated on the layer.
The undercoat layer contains a pigment and a resin, and has a gradient in the resin content concentration with respect to the pigment in the vertical direction of the substrate,
An electrophotographic photoreceptor, wherein the content concentration of the resin is high on the side of the conductive substrate. 2. A conductive substrate is provided by providing an undercoat layer containing a pigment and a resin on a conductive substrate, and then treating the undercoat layer with an organic solvent that dissolves only the resin in the undercoat layer. 2. The electrophotographic photosensitive member according to claim 1, wherein the resin content concentration with respect to the pigment in the vertical direction has a gradient. 3. An undercoating layer containing a pigment and a thermosetting resin is provided on a conductive substrate, and then undercoating is performed with an organic solvent that dissolves only the thermosetting resin monomer during the curing of the thermosetting resin. 3. The electrophotographic photosensitive member according to claim 2, wherein the layer is treated and then heat-cured to give a gradient in the resin content concentration with respect to the pigment in the vertical direction of the conductive substrate.