JPS63261264A - Positively chargeable type electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To enhance sensitively of a photosensitive body and to lower residual potential by forming an electric charge generating layer on a photoconductive layer. CONSTITUTION:The photosensitive body is formed by successively laminating on a conductive substrate the photoconductive layer containing an organic pigment (a) for generating charge and an electron donative charge transfer material (b), and the charge generating layer containing an organic pigment (c) for generating charge. If is preferred to use one or more kinds of tau, tau', zetaand zeta-type metal-free phthalocyanines for the pigment (c), and said phthalocyanines can be used for the pigment (a), and the charge transfer material (b) high or low molecular weight can be used for the material (b). Each of these layers can be formed successively on the conductive substrate by using a desired binder and applying a coating process.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a positively charged electrophotographic photoreceptor having excellent electrophotographic properties.

(Prior Art) In an electrophotographic photoreceptor that uses a photoconductive substance as a photosensitive material, conventional photoconductive substances are used as photoconductive substances.

Inorganic photoconductors such as selenium, zinc oxide, titanium oxide, and cadmium sulfide have been mainly used. However, many of these are generally highly toxic and there are problems in how to dispose of them.

On the other hand, photosensitive materials using organic photoconductive compounds are generally less toxic than those using inorganic photoconductive substances, and also have transparency, flexibility, light weight, surface smoothness, price, etc. Since it is advantageous in terms of, it has been widely studied and put into practical use in recent years.

Among them, composite photoreceptors that separate the functions of charge generation and transport have been rapidly increasing in recent years because they can significantly improve sensitivity, which was a major drawback of conventional photoreceptors using organic photoconductive compounds. progress is being made. Such composite photoreceptors are disclosed in US Pat. No. 3,837,851, for example.
No. 3, No. 871.882, etc.

When these composite photoreceptors are applied to an electrophotographic device using the Carlson method, a static potential is first formed on the surface of the photoreceptor, and then developed with a developer generally called a toner that is charged with opposite signs. The toner image can be transferred and fixed onto another substrate 9, such as paper, to obtain a copy.

(Problems to be Solved by the Invention) Conventional electrophotographic photoreceptors using organic photoconductive compounds generally have a charge generation layer and a hole transfer type charge transport layer laminated in sequence on a conductive layer. , the surface of the photoreceptor is negatively charged. When negative charging is performed by corona discharge, more ozone waves are generated than in the case of positive charging, and the charging tends to be unrestricted or negative. In this respect, it is desirable to use a photoreceptor that functions with positive charging, that is, a positively charged electrophotographic photoreceptor. As a positively charging type electrophotographic photoreceptor, there is a photoreceptor in which a photoconductive layer containing an organic pigment that generates a charge and an electron-donating charge transporting substance is laminated on a conductive layer. This photoreceptor has the advantage of being usable even when negatively charged and being easy to manufacture, but compared to composite photoreceptors, it has inferior electrophotographic properties.
In particular, the sensitivity is low.

Residual potential tends to be high.

An object of the present invention is to overcome the above-mentioned drawbacks and provide a positively charged electrophotographic photoreceptor with excellent electrophotographic properties.

(Means for solving the blackout problem) The present invention achieves the above object by providing yet another charge generation layer on the photoconductive layer.

That is, the present invention provides a photoconductive layer in which a photoconductive layer containing an organic pigment that generates a charge and an electron-donating charge transport substance, and a charge generation layer containing an organic pigment that generates a charge are laminated in sequence on a conductive layer. This invention relates to a charged electrophotographic photoreceptor.

The materials used in the positively charged electrophotographic photoreceptor according to the present invention will be described in detail below.

First, in the present invention, the conductive layer is a conductive material such as conductively treated paper, conductively treated plastic, a plastic film laminated with metal foil such as aluminum, a metal plate, or a metal drum.

The organic pigments that generate charge contained in the photoconductive layer include:
Azoxybenzene series, disazo series, trisazo series, bay
Pigments known to generate charges, such as zimidazole, polycyclic quinoline, indigoid, quinacridone, phthalocyanine, perylene, and methine, can be used. These pigments are described, for example, in JP-A-47-37
No. 54.

JP-A-47-37544, JP-A-47-18543, JP-A-47-18544, JP-A-48-43942
No., JP-A-48-70538, JP-A-49-1231
No., JP-A-49-105536, JP-A-50-752
No. 14, JP-A-50-92738, JP-A-58-18
No. 2640, European Patent Application Publication No. 92,255, etc.

In addition to these, any organic pigment that generates a heavy carrier upon irradiation with light can be used.

Further, as the charge transporting substance contained in the photoconductive layer, polymer compounds such as poly-N-vinylcarbazole, polyvinylpyrene, polyvinylbenzothiophene, polyvinylpyrazoline, etc., and carbazole are used.

3-phenylcarbazole, 2-phenylindole,
Oxadiazole, 1-phenyl-3-(4-diethylaminostyryl)-5-(4-diethylaminophenyl)pyrazoline, hydrazone.

2-phenyl-4-(4-diethylaminophenyl)-
Examples include low molecular weight compounds such as 5-phenyloxazole, triphenylamine, and imidazole, and electron-donating compounds such as derivatives thereof.

Additives such as a binder, a plasticizer, a fluidity imparting agent, and a pinhole inhibitor, which are commonly used in electrophotographic photoreceptors, can be added to the photoconductive layer as necessary.

Examples of the binder include silicone resin, polyamide resin, polyurethane resin, polyester resin, epoxy resin, polyketone resin, polycarbonate resin, polystyrene resin, polymethyl methacrylate resin, and polyacrylamide resin.

Furthermore, thermosetting resins and photocuring resins that are crosslinked by heat and/or light can also be used. In any case, resins that are insulating and capable of forming a film under normal conditions, as well as heat and/or
Alternatively, there is no particular restriction as long as it is a resin that is cured by light and forms a film. Examples of the plasticizer include halogenated paraffin, dimethylnaphthalene, dibutyl phthalate, and the like. Examples of the fluidity imparting agent include Modaflow (manufactured by Monnanto Chemical Co.), Acronal 4F (manufactured by Pasuf Co., Ltd.), and examples of the pinhole inhibitor include benzoin, dimethyl phthalate, and the like. These may be selected and used as appropriate, and the amount thereof may be determined as appropriate.

When the charge-transporting substance is a low-molecular compound, the binder used in the photoconductive layer has a molecular weight of 80 to
450% by weight is preferred, especially 100-30000-3
If the amount of the binder is less than 80% by weight, the photoconductive layer will not be able to maintain sufficient strength and the charging property will tend to decrease.

If it exceeds 450% by weight, the sensitivity of the photoreceptor will quickly decrease. When the charge transport substance is a polymer compound, it is not necessary to use a binder, but for the polymer compound,
It may be used in amounts up to 450% by weight.

The charge-generating organic pigment is preferably used in an amount of 0.1 to 20% by weight, particularly preferably 0.5 to 5% by weight, based on the total amount of the charge transporting substance and binder. 0
．． If the amount is less than 1% by weight, the sensitivity of the photoreceptor tends to decrease, and if it exceeds 20% by weight, the charging property tends to decrease.

Furthermore, other additives may be used if necessary, and in that case, the amount added to the photoconductive layer is preferably 5% by weight or less.

As the charge-generating organic pigment contained in the charge generation layer, any of the organic pigments described above can be used. In this case, the organic pigment contained in the charge-generating layer may be the same as or different from that contained in the photoconductive layer, but the organic pigment contained in the charge-generating layer may be 9%, as disclosed in Japanese Patent Application Laid-open No. 182640/1983 and the European Patent Application. If τ, τ', η, and η' type metal-free phthalocyanine described in Publication No. 92.255 etc. is used, it has high sensitivity even to long wavelengths, so it can be used as an electrophotographic photoreceptor for printers equipped with diode lasers. It is also valid as

Also in the charge generation layer, additives such as the binder, plasticizer, fluidity imparting agent, pinhole suppressor, etc. described above may be used as necessary. The binder can be used in the 400 tonne weight range for the charge generating material. The amount of binder is 4
If it exceeds 00 weights, the electrophotographic properties will deteriorate. Additives such as plasticizers are appropriately used in an amount of 5% by weight or less based on the total amount of organic pigments.

The thickness of the photoconductive layer is preferably 5 to 50 μm.

Particularly preferred is 8 to 20 μm. If the thickness is less than 5 μm, the charging property tends to deteriorate, and if it exceeds 50 μm, the sensitivity tends to decrease. The thickness of the charge generation layer.

o, o o i ~ 10 μm is preferred, 0.2 ~ 9%
5 μm is preferred. 0. If the OO is less than 1 μm, the sensitivity tends to be poor, and if it exceeds 10 μm, the residual potential tends to increase.

Next, the method of forming each layer will be described.

To form a photoconductive layer, a charge generating material, a charge transporting substance, and optionally a binder and additives are mixed with a ketone solvent such as acetone or methyl ethyl ketone, or an ether solvent such as tetrahydrofuran.

Aromatic solvents such as toluene and quinolene, methylene chloride,
Halogenated hydrocarbon solvents such as carbon tetrachloride.

After uniformly dissolving or dispersing in an alcoholic solvent such as methanol, ethanol, propatool, etc.

Coat on the conductive layer and dry.

Next, as for the method of forming the charge generation layer.

When only an organic pigment is used, vacuum deposition can be performed, but after uniformly dissolving or dispersing the organic pigment and optionally a binder and additives in the same solvent as in the case of the photoconductive layer, It can also be formed by coating and drying.

The photoreceptor of the present invention may have a thin adhesive or barrier layer immediately above the conductive layer, and may further have a protective layer over the charge generating layer.

When copying or printing is performed using the electrophotographic photoreceptor according to the present invention, the surface is positively charged as in the conventional case.

After exposure, development is performed, and the image is transferred onto a transfer material such as plain paper and fixed.

(Example) The present invention will be described in detail based on the following examples.
It is not limited to this.

Each material used in the examples below is listed below. Abbreviations are shown in parentheses.

(1) Charge-generating organic pigment τ-type metal-free phthalocyanine (τ-H2PC) (2) Charge-transporting substance 2-(p-diethylaminophenyl)-4-(p-dimethylaminophenyl)-5-(0- Chlorophenyl)-
1,3-Oxazole (OXZ) (3) Binder Polyester resin: Vylon 200 [Toyobo ■Product name] Butyral resin: Nisrex BM-8 [Tanezu Chemical Industry ■Product name] Comparative example τ-HzPc O, 6a , 5.0 g of OXZ, Byron 20014.49, and 80 g of tetrahydrofuran were kneaded for 10 hours using a ball mill. The obtained dispersion was applied onto an aluminum plate using an applicator, and 1
This was dried at 00° C. for 15 minutes to produce a single-layer electrophotographic photoreceptor with a thickness of 15 μm.

Examples 1-2 τ-HxP c 2- Og m Nisrex BM-8
A mixture of 2,0° and methanol 809 was ball milled (
The mixture was kneaded for 8 hours using a 3-inch bot mill (manufactured by Nippon Kagaku Tou Co., Ltd.). Apply the resulting dispersion using an applicator.

It was coated on a photoconductor prepared in the same manner as in the comparative example, and 1
After drying at 00° C. for 1 hour, an electrophotographic photoreceptor having a charge generation layer having the thickness shown in Table 1 was obtained.

The electrophotographic properties of the obtained electrophotographic photoreceptor were measured using an electrostatic recording tester (manufactured by Kawaguchi Denki 5P-428'), and the results are shown in Table 1.

In addition, the initial potential Vo (V) in Table 1 indicates the charged potential when a positive 5 Kv corona is discharged for 10 seconds in dynamic measurement, and the dark decay (VK) indicates the potential when left for 30 seconds in a dark place. It shows the attenuation rate, and the half-decreased exposure amount (Es
o) indicates the amount of light until the potential is halved when irradiated with 101x white light, and residual potential VR (■ indicates 101x white light).
The surface potential after being irradiated with white light for 30 seconds is shown. Table 1
It can be seen from the above that the photoreceptor of Example 1.2 has higher sensitivity and lower residual potential than the photoreceptor of Comparative Example.

Table 1 (Effects of the Invention) Pertaining to the present invention. Above K of the photoconductive layer containing an organic pigment that generates a charge and an electron-donating charge transporting substance.

A positive band type electrophotographic photoreceptor, which is formed by laminating a charge generation layer containing an organic pigment that generates charges, has high sensitivity.

Shows excellent electrophotographic properties with low residual potential.

Claims (1)

[Claims] 1. A photoconductive layer containing an organic pigment that generates a charge and an electron-donating charge transport substance, and a charge generation layer containing an organic pigment that generates a charge are sequentially laminated on the conductive layer. A positively charged electrophotographic photoreceptor. 2. The charge-generating organic pigment contained in the charge-generating layer is
The positively charged electrophotographic photoreceptor according to claim 1, which is at least one of τ, τ', η, and η' type metal-free phthalocyanines.