JPH0778641B2 - Electrophotographic photoreceptor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electrophotographic photoreceptor, and more specifically, it is repeatedly used in a PPC copying machine, a laser beam printer, a digital copier (copier is a registered trademark of Copier Corporation), and the like. The present invention relates to improvement of the intermediate layer in the electrophotographic photoreceptor.

[Prior Art] Generally, an electrophotographic photosensitive member that is repeatedly used (hereinafter sometimes simply referred to as a "photosensitive member") has good chargeability (prevents unnecessary charge injection and is 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, a conductive pigment such as indium oxide, tin oxide or carbon is added to the intermediate layer (JP-A-58-93063) or a conductive polymer is added (JP-A-58). No. 95744) is proposed. However, in the former case, the chargeability is reduced, so a second intermediate layer consisting only of resin must be formed between the conductive pigment-containing intermediate layer and the photosensitive layer, and in the latter case, the chargeability is reduced. The performance is not deteriorated, but there is a problem in practical use because the sensitivity is lowered.

Further, in a so-called laminated type photoreceptor in which the photosensitive layer has a laminated structure of the charge generation layer and the 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] The present invention provides an electrophotographic photoreceptor having an intermediate layer between a conductive substrate and a photosensitive layer, which is repeatedly used, wherein the intermediate layer is an anionic conductive polymer and titanium oxide not surface-treated. It is characterized by containing a pigment.

By the way, although the present inventor suppresses the increase in residual potential in an environment of low humidity when an anionic conductive polymer is added to the intermediate layer resin, on the other hand, a decrease in the sensitivity that can be observed is a titanium oxide pigment not surface-treated. It was confirmed that it can be solved by further containing it. It was also confirmed that the addition of such a specific titanium oxide 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 photoconductor of the present invention has a structure in which an intermediate layer and a photosensitive layer are sequentially laminated on a conductive substrate. 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; an insulating support (such as a plastic or a plastic film) on which a metal is vapor-deposited or a conductive paint is applied. An example is a manufactured product.

Examples of the anionic conductive polymer used in the intermediate layer include polymers containing sulfonic acid or an alkali metal salt or ammonium salt of sulfonic acid.

Further, the "titanium oxide pigment which has not been surface-treated" used in the intermediate layer is classified into anatase type I described in JIS-K5116.

The intermediate layer may be composed of only the above-mentioned anionic conductive polymer and the titanium oxide pigment which has not been surface-treated, but may contain a binder (low resistance resin) which has been conventionally used. However, the binder that may be used here is water- or alcohol-soluble, considering that it is soluble in the solvent for dissolving the anionic conductive polymer and is not attacked by the photosensitive layer forming liquid applied on the intermediate layer. Is preferred. Specific examples thereof include polyvinyl alcohol, sodium polyacrylate, CMC, casein, sodium alginate, nylon, non-polymerized nylon, and alkoxymethylated nylon.

To form an intermediate layer with these materials, an anionic conductive polymer, titanium oxide pigment not surface-treated,
The solvent and, if necessary, the binder may be placed in a ball mill or the like to disperse the pigment well, and the resulting dispersion may be applied onto a conductive substrate and dried. The thickness of the intermediate layer is 0.3 to 20
It is about μm.

The ratio of the anionic conductive polymer to the softened titanium pigment not surface-treated and the binder cannot be uniformly determined because it varies depending on the materials used, but the total amount of the anionic conductive polymer and the binder is When the amount is 1 part, the titanium oxide pigment not surface-treated is 0.05 to 10 in weight ratio.
Some parts are appropriate. Further, the ratio of the anionic conductive polymer and the binder cannot be uniformly determined, but when the anionic conductive polymer is 1 part, the binder is 0 to 200 parts by weight, preferably 10 to 200 parts by weight. Is appropriate.

The photosensitive layer comprises (1) a charge transfer complex formed by a combination of an electron-donating compound and an electron-accepting compound (USP34842).
37), (2) sensitized by adding a dye to an organic photoconductor (described in JP-B-48-25658), (3) a dispersion of a pigment in a hole or electron active matrix ( JP-A-47-30328, JP-A-47-18545 and the like), (4) Functionally separated charge generation layer and charge transport layer (JP-A-49-105537) , (5) containing a eutectic chain composed of a dye and a resin as a main component
47-10785), (6) Organic photoconductive materials known in the art such as organic pigments or inorganic charge generating materials added to a charge transfer complex (described in JP-A-49-91648). It may be formed on any part of the body.

However, among these, the laminated type photoreceptor of the type (4) is particularly advantageous because it has high sensitivity and various materials can be selected according to the function.

The charge generation layer is an azo pigment, a phthalocyanine pigment, a square pigment, an indigo pigment, a perylene pigment, a selenium powder, a selenium alloy powder, an amorphous silicon powder, a zinc oxide powder, a cadmium sulfide powder, and the like. It is formed by dispersing it in a binder resin solution such as polycarbonate, polyvinyl butyral, or acrylic resin, and coating this on the intermediate layer.
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)
No. 46760) and a charge transporting substance such as polyester, polysulfone, polycarbonate, polymethacrylates, polystyrene, etc. are dissolved in the film-forming resin, and the thickness of the charge generation layer is 10 to 10 μm. 30μ
It may be applied to about m. 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 Water was added to polybeer alcohol (PVA-217 manufactured by Kuraray Co., Ltd.) and the mixture was heated with stirring to prepare an aqueous polyvinyl alcohol solution, which was adjusted to have a solid content concentration of 5.0% by weight.

200g of this polyvinyl alcohol solution in a ball mill,
Anionic conductive polymer [ammonium polystyrene sulfonate (Kanebo NSC VERSA-LC125)] 1.0
g and titanium oxide without surface treatment (J manufactured by Teikoku Kako Co., Ltd.
A-1) 8.0 g was added and dispersed for 5 hours to prepare a coating liquid for the intermediate layer. This solution was applied onto the surface of an aluminum plate having a thickness of 0.2 mm by dip coating and dried at 120 ° C. for 5 minutes.
The thickness of the intermediate layer thus obtained was about 2.5 μm.

Next, dissolve 5 g of polyester resin (manufactured by Toyobo Co., Ltd.) in 150 g of cyclohexanone, and add the following structural formula 10 g of the trisazo pigment of was added and dispersed in a ball mill for 48 hours, and 210 g of cyclohexanone was further added and dispersed for 3 hours. This was taken out into a container so that the solid content became 1.5% by weight, and diluted with cyclohexanone while stirring. The thus obtained coating liquid for charge generation layer was subjected to the above procedure and dried at 120 ° C. for 5 minutes to form a charge generation layer having a thickness of about 0.2 μm.

Furthermore, polycarbonate resin (Panlite K- made by Teijin Ltd.
1300) 12 g was dissolved in 90 g of tetrahydrofuran, and further dissolved in 7 g of a charge transport substance having the following structural formula. The thus-obtained charge transport layer coating liquid was dipped onto the charge generation layer and dried at 120 ° C. for 15 minutes to form a charge transport layer having a thickness of about 18 μm to prepare a laminated electrophotographic photoreceptor. .

Comparative Example 1-a Comparison was made in the same manner as in Example 1 except that the anionic conductive polymer of Example 1 was changed to a cationic conductive polymer [polydimethylarylammonium chloride (CP-280 manufactured by Calgon, USA)]. The photoconductor was created.

Comparative Example 1-b A comparative photoconductor was prepared in exactly the same manner as in Example 1 except that the surface-treated titanium oxide in Example 1 was replaced with surface-treated titanium oxide (Taipaque R-670, Ishihara Sangyo Co., Ltd.). did.

Example 2 10 g of alcohol-soluble copolymer nylon (CM-8000, manufactured by Toray Industries, Inc.) was dissolved in 100 g of methanol. 1 g of anionic conductive polymer [sodium polystyrene sulfonate (Chemistat 6120 manufactured by Sanyo Chemical Co., Ltd.)] and titanium oxide (TA-100 manufactured by Fuji Chitale Co., Ltd.) not surface-treated.
Was added and dispersed in a ball mill for 8 hours to prepare a coating liquid for the intermediate layer.

This solution was dip-coated on the surface of an aluminum plate having a thickness of 0.2 mm and dried at 120 ° C. for 5 minutes. The thickness of the intermediate layer thus obtained was about 3.5 μm.

Next, 5 g of butyral resin (manufactured by Sekisui Chemical Co., Ltd.) was dissolved in 150 g of cyclohexanone, and the same trisazo pigment as in Example 1 was added thereto.
15 g was added and dispersed by a ball mill for 48 hours, and 210 g of cyclohexanone was further added and dispersed for 3 hours. This was taken out into a container and diluted with cyclohexanone while stirring so that the solid content was 2.0% by weight. The charge generation layer coating solution thus obtained is dip-coated on the intermediate layer and the temperature is 120 ° C.
And dried for 5 minutes to form a charge generation layer having a thickness of about 0.2 μm.

Furthermore, polycarbonate resin (Panlite K- made by Teijin Ltd.
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 Comparative example 2 was carried out in the same manner as in Example 2 except that the anionic conductive polymer of the example was changed to a cationic conductive polymer [polydimethylaryl ammonium chloride (CP-280 manufactured by Calgon, USA)]. A photoconductor was created.

Comparative Example 2-b A comparative photoconductor was prepared in exactly the same manner as in Example 2 except that the surface-treated titanium oxide of Example 2 was replaced with the surface-treated titanium oxide (JRNC manufactured by Teikoku Chemical Co., Ltd.).

These samples (2 types of photoconductor of the present invention, 4 types of comparative photoconductor)
Was measured under the following conditions using an Electrostatic Paper Analyzer SP-428 (manufactured by Kawaguchi Electric Co., Ltd.).

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 clear from the description of the examples, by incorporating a specific surface-untreated titanium oxide and anionic conductive polymer in the intermediate layer, fatigue can be obtained with high sensitivity even in a low humidity environment or a room temperature environment. It is possible to obtain a photoconductor with a small amount.

Claims (1)

[Claims] 1. An electrophotographic photoreceptor comprising an intermediate layer between a conductive substrate and a photosensitive layer, which is repeatedly used,
An electrophotographic photosensitive member characterized in that the intermediate layer contains an anionic conductive polymer and a titanium oxide pigment which is not surface-treated.