JP2537715B2 - Electrophotographic photoreceptor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photosensitive member, and more particularly to a zinc oxide photosensitive member sensitive to long wavelength laser light.

[0002]

2. Description of the Related Art In recent years, so-called digital type electrophotographic printers (laser beam printers) using a semiconductor laser as a light source have been widely used as output printers for computers. The feature of this method is
It is possible to freely create and edit an image on the display using a computer. The created image is recorded on a photoconductor by electrophotography using an LED or a semiconductor laser as a light source, and toner-developed into a visible image. .
The toner image on the photoconductor is transferred to plain paper or fixed as it is to become a permanent image.

As the photoconductor having photoresponsiveness to the above-mentioned LED and semiconductor laser, many compounds such as selenium, selenium-tellurium, selenium-arsenic, cadmium sulfide, phthalocyanine, organic photoconductor, zinc oxide are known. Of these, zinc oxide is the most excellent in terms of pollution-free, low cost, and easy handling in the method of fixing the visible image on the photoconductor as it is without transferring it.

By the way, conventionally known zinc oxide photoreceptors are sensitized with dyes such as rose bengal, rhodamine, eosin, and bromphenol blue. In this case, since they have photoresponsive sensitivity in the visible light region, they are LEDs or semiconductors. It is not sensitive to the long wavelength range of lasers. Therefore, sensitizing zinc oxide with a cyanine dye has been carried out as a means of imparting sensitivity to the zinc oxide photoconductor in the long wavelength region. For example, JP-A-57-46245, JP-A-58-42055, and JP-A-61-275760.
JP-A No. 62-108258 and JP-A No. 62-108258 propose that a zinc oxide photoreceptor sensitized with a cyanine dye can be used as a lithographic printing plate as a plate-making material which is sensitive to laser light.

However, since the cyanine dye-sensitized zinc oxide photoreceptor according to the prior art has a marked background coloration, when the photoreceptor is used as a full-color recording paper by direct electrophotography without a transfer step, a clear color image is obtained. There is a problem that is not obtained. Therefore, in order to make the background of the photoconductor as white as possible, it is possible to reduce the addition amount of the cyanine dye as much as possible. It caused a problem that it could not be done. In order to solve this, the present inventors have proposed to maintain the photosensitivity and improve the whiteness of the background by specifying the acid value of the binder of the zinc oxide photoconductor (Japanese Patent Application No. Hei 10 (1999) -135242). 3-
109573). However, the zinc oxide photoconductor has a problem that the photosensitivity in the long wavelength region is not yet sufficient.

Further, when the zinc oxide photoreceptor is used as a master for lithographic printing, the coloring of the background is not a serious problem, and therefore the amount of the cyanine dye added can be increased in order to increase the photosensitivity. However, since cyanine dyes are expensive, it is desired to keep the photosensitivity and use the amount thereof as small as possible.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve these problems, and maintains good sensitivity to long-wavelength laser light with a small amount of cyanine dye added. And to improve the whiteness of the background and to provide a cyanine dye-sensitized zinc oxide photoreceptor that can be used as a color recording medium.

[0008]

As a result of extensive studies to solve these problems, the present invention contains a p-phenylenediamine derivative in a photoconductive layer of a zinc oxide photoreceptor sensitized with a cyanine dye. It was found that a remarkable sensitizing effect appears by virtue of this, and the present invention was achieved. That is, the present invention relates to an electrophotographic photosensitive member comprising a support and a photoconductive layer containing zinc oxide sensitized with a cyanine dye and a binder as main components. I)

Embedded image (In the formula, R represents an alkyl group or a phenyl group), and a p-phenylenediamine derivative is contained.

In this case, typical p-phenylenediamine derivatives include those represented by the following structural formulas (1) to (3).

Embedded image

By adding these p-phenylenediamine derivatives to the cyanine dye in an amount of 10 to 200%, the amount of the cyanine dye added can be minimized, and a zinc oxide photoreceptor having practically sufficient sensitivity can be obtained. I got it successfully.

The zinc oxide used in the present invention is a so-called indirect method (French method) zinc oxide which is usually used for an electrophotographic photoreceptor, for example, metallic zinc as a raw material, or a so-called direct method which is directly produced from zinc ore. (American law)
Zinc oxide is applied.

In the present invention, the cyanine dye for sensitizing the zinc oxide is, for example, the following structural formula (1
Examples thereof include 1) to (16), but the invention is not limited thereto.

Embedded image

To sensitize zinc oxide using a cyanine dye, for example, (1) a solution of a cyanine dye and zinc oxide are mixed, and the cyanine dye is adsorbed on the zinc oxide surface in advance, and then the binder is added. Method of adding solution, (2) Add cyanine dye solution, zinc oxide, binder solution at the same time,
There are a method of mixing and dispersing, a method of (3) mixing and dispersing zinc oxide and a binder and then adding a cyanine dye solution, and any of them can be applied to the present invention.

As the binder used in the present invention, a vinyl resin such as polyacrylate, polymethacrylate, polystyrene resin, polyvinyl acetate or polyvinyl chloride,
Alternatively, copolymers of these vinyl resins, silicone resins, polyester resins, etc. may be mentioned. In this case, as the ester residue constituting the ester of acrylic acid ester or methacrylic acid ester, a methyl group, an ethyl group,
n-propyl group, isobutyl group, n-hexyl group, 2-
Ethyl-1-hexyl group, 2-hydroxyethyl group, 3
-Hydroxybutyl group and the like.

As the styrene derivative, there are styrene derivatives such as methylstyrene, ethylstyrene, vinylbenzoic acid, etc. in addition to styrene, and it is also possible to copolymerize them with acrylic acid ester and methacrylic acid ester, if necessary. . If necessary, acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid or their anhydrides can be used as a copolymerization component.

Examples of the support applicable to the present invention include electrically treated paper, a polyester film deposited with a metal such as aluminum, or a metal foil, and it is preferable to use the support properly according to the application.

The electrophotographic photosensitive member of the present invention is prepared by uniformly mixing and dispersing a mixture of zinc oxide, a binder and a solvent with a disperser such as a paint conditioner, a kedi mill or a sand mill, and thereby obtaining a coating liquid for a photoconductive layer. Is produced by coating and drying on a support by a coating method such as blade coating, reverse coating, rod coating or knife coating. At that time, cyanine dye sensitization to zinc oxide,
The above means may be appropriately selected and applied to the present invention.

The compounding ratio of zinc oxide and the binder is zinc oxide 10
With respect to 0 parts by weight, the binder is preferably 5 to 30 parts by weight. When the amount of the binder is less than 5 parts by weight, the strength of the photoconductive layer is lowered, and when it is more than 30 parts by weight, the sensitivity is lowered. The residual potential rises.

Examples of the solvent for the binder include aromatic hydrocarbons such as toluene and xylene, ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone, alcohols such as methanol, ethanol, propanol and butanol, acetic acid esters and acetic acid. Acetates such as butyl and amyl acetate, cyclic ethers such as dioxane and tetrahydrofuran, and halogenated hydrocarbons such as methylene chloride and ethylene chloride can be used.

[0020]

The present invention will be described in detail below with reference to examples. Examples 1 to 4 Coating solutions for photoconductive layers having the compounding ratios shown in Table 1 were prepared. At that time, the coating liquid was prepared by the following procedure. In addition,
The amount of the p-phenylenediamine derivative added represents a ratio with respect to the amount of cyanine dye (solid content), and the other components represent parts by weight.

[Table 1]

The monomer composition of styrene / n-butyl methacrylate / methyl acrylate / acrylic acid is 20 /
A binder solution was prepared by using a copolymer of 30/40 / 0.5 and using toluene as a solvent so that the solid content was 40%. Further, the cyanine dye of structural formula (11) (NK125 manufactured by Japan Photosensitive Dye Research Institute) was dissolved in a mixed solvent of methanol / chloroform = 1/1 to give 0.25
% Dye solution was made. The obtained binder solution was mixed with toluene and a cyanine dye solution, and then zinc oxide for electrophotography was added and dispersed for 40 minutes with a paint conditioner to obtain a coating liquid for a photoconductive layer. A predetermined amount of N-isopropyl-N'-phenyl-p-phenylenediamine (Antage 3C manufactured by Kawaguchi Chemical Industry Co., Ltd.) was added to the coating solution as a p-phenylenediamine derivative. The obtained coating liquids were applied to the aluminum vapor-deposited surface of a support made of an aluminum vapor-deposited polyester film (thickness: 75 μm) with a wire bar to give a thickness of 1
A 5 μm photoconductive layer was formed to prepare the electrophotographic photoreceptors of the present invention shown in Examples 1 to 4, respectively.

Comparative Examples 1 to 2 In Examples 1 to 4, the coating liquid for a photoconductive layer having the compounding ratio shown in Table 1 was used without containing N-isopropyl-N'-phenyl-p-phenylenediamine. Was coated on the aluminum vapor-deposited surface to form a photoconductive layer, and a comparative electrophotographic photosensitive member was prepared.

The photoconductors obtained in Examples 1 to 4 and Comparative Examples 1 and 2 were subjected to photosensitivity measurement under the following conditions using an electrostatic paper analyzer (EPA8100) manufactured by Kawaguchi Electric Co., Ltd. The obtained results are shown in Table 2. Static 1 Charging -6KV Exposure intensity 2 μm (wavelength 780 nm) Dark decay 2 seconds Here, E1 / 2 and E1 / 10 have surface potentials of 1 / E, respectively.
It represents the exposure energy (μJ / cm 2) required to decay to 2 and 1/10. Further, the color tone was measured with a dye meter manufactured by Nippon Denshoku Co., Ltd. and displayed as L, a and b. as a result,
By adding N-isopropyl-N'-phenyl-p-phenylenediamine to the photoconductive layer, the photosensitivity in the long wavelength region is significantly improved, the whiteness is increased, and the residual potential is significantly reduced. showed that. In particular, in comparison with Comparative Example 2, the electrophotographic photoreceptor of the present invention maintained sufficient whiteness while adding N-isopropyl-N'-phenyl-p-phenylenediamine, thereby adding the cyanine dye in the conventional amount. It was found that the same level of photosensitivity can be obtained by 1/3 of the above.

[0024]

[Table 2]

Examples 5 to 8 Coating solutions for photoconductive layers having the compounding ratios shown in Table 3 (the compounding ratios of the respective components have the above-mentioned meanings) were prepared.

[Table 3] At that time, the coating liquid was prepared according to the procedure described below according to Examples 1 to 4. That is, methyl methacrylate / ethyl methacrylate / 2-ethylhexyl acrylate /
The monomer composition ratio of acrylic acid is 15/15/10/0.
A binder solution having a solid content concentration of 40% was prepared by using the copolymer of 4 as a solvent in toluene. Next, the cyanine dye of the structural formula (12) described above (N
K2421) 0.25% methanol solution was prepared and p
-N-isopropyl- as a phenylenediamine derivative
Instead of N′-phenyl-p-phenylenediamine,
Using N-1,3-dimethylbutyl-N′-phenyl-p-phenylenediamine, a photoconductive layer coating solution was prepared in the same manner as in Examples 1 to 4, and aluminum vapor-deposited polyester film was vapor-deposited on aluminum. 15μ thick on the surface
m to form a photoconductive layer, and the electrophotographic photoreceptors of the present invention shown in Examples 5 to 8 were obtained.

Comparative Example 3 In Examples 5 to 8, N-1,3-dimethylbutyl-
A photoconductive layer containing no N'-phenyl-p-phenylenediamine was formed on the aluminum vapor-deposited surface of the support to prepare an electrophotographic photoreceptor for comparison.

The electrophotographic photoreceptors obtained in Examples 5 to 8 and Comparative Example 3 were operated in the same manner as in Examples 1 to 4 using an electrostatic paper analyzer (EPA8100) manufactured by Kawaguchi Electric Co., Ltd. The characteristics of the photoconductor were evaluated and the obtained results are shown in Table 4. As a result, N-1,3-dimethylbutyl-N′-phenyl-p
-It was shown that the addition of phenylenediamine to the photoconductive layer significantly improved the photosensitivity in the long wavelength region and significantly reduced the residual potential.

[Table 4]

[0028]

INDUSTRIAL APPLICABILITY In a zinc oxide photosensitive material sensitized with a cyanine dye, the electrophotographic photosensitive material of the present invention containing a p-phenylenediamine derivative in the photosensitive layer remarkably improves electrophotographic photosensitivity. Therefore, the amount of the cyanine dye added can be greatly reduced, and thus, the present invention can be applied to a color recording medium that requires whiteness. In addition, since the amount of expensive cyanine dye used can be reduced, the photoreceptor can be provided under inexpensive manufacturing conditions.

Claims (1)

(57) [Claims] 1. An electrophotographic photosensitive member comprising a support and a photoconductive layer containing zinc oxide sensitized with a cyanine dye and a binder as main components, the photoconductive layer having the following general formula (I): [Chemical 1] An electrophotographic photoreceptor comprising a p-phenylenediamine derivative represented by the formula (wherein R represents an alkyl group or a phenyl group).