JPH08184979A - Electrophotographic photoreceptor and electrophotographic device - Google Patents

Abstract

PURPOSE: To obtain an electrophotographic photoreceptor having the potential characteristic stabilized in all the environments ranging from a low-temp. and low-humidity environment to a high-temp. and high-humidity environment and an electrophotographic device using the photoreceptor by incorporating a powder consisting of a barium sulfate fine particle having a coating layer into the intermediate layer and forming the coating layer with a specified compd. CONSTITUTION: An intermediate layer and a photosensitive layer are formed on a conductive substrate in this order to constitue an electrophotographic photoreceptor 1. The intermediate layer contains a powder consisting of a barium sulfate fine particle having a coating layer, and the coating layer is formed with a compd. selected from a group consisting of indium oxide, zinc oxide, zirconium oxide and cadmium oxide. The electrophotographic device has the photoreceptor 1, a means 2 for charging the photoreceptor 1, a means for image-developing the charged photoreceptor to form an electrostatic latent image and a means 4 for developing the photoreceptor 1 wherein the electrostatic latent image is formed with a toner.

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 an electrophotographic apparatus using this photosensitive member.

[0002]

2. Description of the Related Art An electrophotographic photosensitive member basically comprises a support and a photosensitive layer formed on the support. But,
Covering defects on the support, improving coatability of the photosensitive layer, improving adhesion between the photosensitive layer and the support, protection against electrical breakdown of the photosensitive layer, improving chargeability, charge injection property from the support to the photosensitive layer It is effective to provide an intermediate layer between the photosensitive layer and the support for improving the above. Therefore, the intermediate layer in the electrophotographic photosensitive member is required to have many functions such as covering property, adhesive property, mechanical strength, appropriate conductivity and electric barrier property.

Conventionally, the following types of intermediate layers have been proposed. (I) A resin thin film containing no conductive filler. (Ii) A resin thin film containing a conductive filler. (Iii) A thin film of (i) above laminated on the thin film of (ii) above.

Since the thin film of (i) above does not contain a conductive filler, the electric resistance of the film is high, and moreover, the film thickness must be increased to cover the defects on the support. Therefore, it has a drawback that the residual potential becomes high at the initial and repeated use. In order to put the thin film (i) into practical use, defects on the support should be reduced and the film thickness of the intermediate layer should be extremely small. Need to be thin.

On the other hand, the thin films (ii) and (iii) described above have an advantage that suitable conductivity can be imparted by dispersing the conductive filler, but if the conductive filler has poor dispersibility, the intermediate layer of Electrical characteristics such as resistance and permittivity change, and have a great influence on potential characteristics and image characteristics. In addition, if the dispersibility of the filler is poor, the surface smoothness of the film will be poor, causing coating defects. Further, if the dispersion of the filler is poor, the adhesion to the support and the mechanical strength will also decrease.

So far, as conductive fillers for the intermediate layer, metals (JP-A-58-181054), metal oxides (JP-A-54-151843), and metal nitrides (JP-A-1-1184848). Gazette) etc. have been reported.

[0007]

However, in the electrophotographic photosensitive member using the conventional conductive filler as the filler of the intermediate layer, the environmental dependence such as temperature and humidity is large,
It has been difficult to prepare a photoconductor having stable potential characteristics and image characteristics in all environments from low temperature and low humidity to high temperature and high humidity. For example, under low temperature and low humidity, which causes an increase in the resistance of the intermediate layer, when the photoreceptor was repeatedly used, charges were accumulated in the intermediate layer, and the residual potential and the bright portion potential increased. On the other hand, under high temperature and high humidity which causes a decrease in the resistance of the intermediate layer, the electrical barrier ability of the intermediate layer was decreased, carrier injection from the support was accelerated, and a decrease in the dark area potential was observed during repeated use. As a result, in addition to a decrease in image density under high temperature and high humidity, in the case of an electrophotographic printer that performs reversal development, unnecessary black spots (black spots) and fogging tend to occur in the image. .

As described above, it is considered that the characteristics of the photoconductor are changed due to the change of environment because the dispersibility of the conductive filler is poor. That is, it is considered that a local resistance change occurs due to a decrease in the dispersibility of the conductive filler inside the intermediate layer, which makes the potential characteristics and the image characteristics susceptible to environmental changes.

An object of the present invention is to provide an electrophotographic photoreceptor having stable potential characteristics and image characteristics under all environments from low temperature and low humidity to high temperature and high humidity, and an electrophotographic apparatus using this photoreceptor. It is possible to provide.

[0010]

That is, the present invention provides an electrophotographic photoreceptor having an intermediate layer and a photosensitive layer in this order on a conductive support, the intermediate layer comprising barium sulfate fine particles having a coating layer. An electrophotographic photoreceptor comprising a powder, and the coating layer formed of a compound selected from the group consisting of indium oxide, zinc oxide, zirconium oxide and cadmium sulfide.

The present invention also includes the above electrophotographic photoreceptor,
Charging means for charging the photoconductor, and image exposure means for performing image exposure on the charged photoconductor to form an electrostatic latent image,
An electrophotographic apparatus comprising: a developing unit that develops the photosensitive member on which an electrostatic latent image is formed with toner.

The electrophotographic photosensitive member of the present invention has an intermediate layer and a photosensitive layer on a support in order from the support side. The intermediate layer contains, as a filler, a powder composed of barium sulfate fine particles having a conductive coating layer.

The barium sulfate fine particles have excellent dispersibility. Moreover, since the refractive index of the barium sulfate fine particles is substantially equal to the refractive index of the binder resin, the light transmittance of the intermediate layer does not decrease.

In the present invention, by providing a conductive coating layer on the barium sulfate fine particles, a specific resistance suitable as a filler is obtained. Indium oxide as the coating layer,
A coating layer made of zinc oxide, zirconium oxide, cadmium sulfide is used. The specific resistance of the powder of barium sulfate having a coating layer is preferably 0.1 to 1000 Ωcm, more preferably 1 to 1000 Ωcm.

In the present invention, the powder resistivity is the resistance measuring device Loresta AP manufactured by Mitsubishi Yuka.
It measured using. The powder to be measured is 500 kg / c
The sample was attached to the above measuring device as a coin-shaped sample which was warmed up under a pressure of m ² .

The coverage of the coating layer is preferably 10 to 80% by weight, more preferably 30 to 60% by weight. The coverage of the coating layer is the ratio of the total weight of the coating layer used for this powder to the weight of the powder of fine particles having the coating layer. The average particle diameter of the barium sulfate fine particles having a coating layer is 0.05
.About.1.0 .mu.m, more preferably 0.07 to 0.7 .mu.m. In the present invention, the average particle size of the fine particles is a value measured by the centrifugal sedimentation method. Generally, when the average particle size of the filler is small, it becomes difficult to disperse and re-aggregate easily,
The filler used in the present invention has excellent dispersibility. The content of the filler is 1.0 to 90 with respect to the intermediate layer.
%, And more preferably 5.0 to 80% by weight.

The coating layer contains a dopant for exhibiting conductivity. Dopants include, for example, tin, germanium, lead for indium oxide, aluminum, tin, gallium, indium for zinc oxide, vanadium, niobium for zirconium oxide,
Examples include tantalum. By including the dopant, the specific resistance of the coating layer can be reduced.
The coating layer of indium oxide, zinc oxide, or zirconium oxide containing a dopant is a solid solution in which a dopant atom is incorporated in the crystal lattice of indium oxide, zinc oxide, or zirconium oxide. The content of the dopant is preferably 0.01 to 30% by weight, more preferably 0.05 to 10% by weight, based on the coating layer.

Examples of the binder resin used in the intermediate layer of the present invention include phenol resin, polyurethane, polyamide, polyimide, polyamideimide, polyamic acid, polyvinyl acetal, epoxy resin, acrylic resin,
Melamine resin or polyester is preferable. These resins may be used alone or in combination of two or more. These resins have good adhesion to the support, improve the dispersibility of the filler used in the present invention, and have good solvent resistance after film formation. Among the above resins, phenol resin, polyurethane and polyamic acid are particularly preferable.

The intermediate layer can be formed, for example, by dipping or solvent coating using a Mayer bar or the like.

In order to improve the dispersibility of the filler, the surface of the filler may be treated with a coupling agent (such as a silane coupling agent or a titanium coupling agent) or a treating agent such as silicone oil. Moreover, you may make the said processing agent contain in the binder of an intermediate | middle layer.

The thickness of the intermediate layer is preferably 0.1 to 30 μm, more preferably 0.5 to 20 μm. The volume resistivity of the intermediate layer is 10 ¹³ Ωcm or less, and further 10 ¹² Ωcm or less 10 Ω.
cm or more is preferred. In the present invention, the volume resistivity is obtained by applying an intermediate layer to be measured on an aluminum plate, further forming a gold thin film on this intermediate layer, and measuring the current value flowing between both electrodes of the aluminum plate and the gold thin film by _p It was determined by measuring with an A meter.

In addition to the powder made of barium sulfate fine particles having a coating layer, the intermediate layer may contain a filler made of powder such as zinc oxide or titanium oxide. Furthermore, a leveling agent may be added to enhance the surface properties of the intermediate layer.

The photosensitive layer of the present invention may be a single layer or a laminated structure composed of at least a charge generation layer and a charge transport layer.

When the photosensitive layer is a single layer, a charge generating substance and a charge transporting substance are contained in the same layer to generate and move photocarriers in the same layer.

When the photosensitive layer has a laminated structure, the charge generating layer containing the charge generating substance and the charge transporting layer containing the charge transporting substance may be laminated in the order of the charge generating layer and the charge transporting layer from the support side. And vice versa.

Examples of the charge generating substance include azo pigments (eg, monoazo, bisazo, trisazo, etc.), metal and metal-free phthalocyanine pigments, indigo pigments (eg, indigo, thioindigo), quinone pigments (eg, anthanthrone). , Pyrenequinone, etc.), perylene pigments (eg, perylene anhydride, perylene imide, etc.), squalium dyes, pyrylium, thiopyrylium salts, triphenylmethane dyes, and the like. Further, an inorganic material such as selenium, selenium-tellurium, or amorphous silicon can also be used as the charge generating substance.

The charge transport material includes an electron transport material and a hole transport material. Examples of the electron transport material and the hole transport material include 2,4,7-trinitrofluorenone, 2,
4,5,7-tetranitrofluorenone, chloranil,
And tetracyanoquinodimethane. Examples of the hole-transporting substance include polycyclic aromatic compounds (such as pyrene and anthracene) and heterocyclic compounds (such as carbazole, indole, imidazole, oxazole, thiazole, oxadiazole, pyrazole, pyrazoline, thiadiazole, and triazole), Hydrazone compounds (eg p-diethylaminobenzaldehyde-N, N-diphenylhydrazone, N, N-diphenylhydrazino-3-methylidene-9-ethylcarbazole), styryl compounds (eg α-phenyl-4 ′)
-N, N-diaminostilbene, 5- [4- (di-p-
Trilylamino) benzylidene] -5H-dibenzo [a,
d] dicycloheptene etc.), benzidine compounds, triarylamine compounds and the like.

When the photosensitive layer is a single layer, the thickness of the photosensitive layer is 5
˜100 μm is preferable, and further preferably 10 to 60 μm. The single photosensitive layer preferably contains 10 to 70% by weight, and more preferably 20 to 70% by weight of each of the charge generating substance and the charge transporting substance.

When the photosensitive layer has a laminated structure, the thickness of the charge generation layer is preferably 0.001 to 5 μm, more preferably 0.05 to 2 μm, and the thickness of the charge transport layer is 1 to 40 μm, more preferably 10 μm.
-30 μm is preferable. The charge generation layer preferably contains 10 to 100% by weight, and more preferably 40 to 100% by weight of the charge generation substance. The charge transport layer contains 2 charge transport materials.
The content is preferably 0 to 80% by weight, more preferably 30 to 70% by weight.

The electrophotographic photoreceptor of the present invention can be obtained by vacuum vapor deposition or combining it with a suitable binder resin to form a film on a support.

As the binder resin for the photosensitive layer, for example, polyvinyl acetal, polycarbonate, polystyrene, polyester, polyacetate ester, polymethacrylate ester, acrylic resin, cellulose resin and the like are preferably used.

Free carriers may be injected from the intermediate layer into the photosensitive layer depending on the type of the material of the photosensitive layer, which lowers the charging ability of the photosensitive member and greatly affects the image characteristics.
In such a case, if necessary, a barrier layer having an electric barrier property (for example, a suitable resin thin film) is provided between the intermediate layer and the photosensitive layer to effectively suppress the injection of free carriers. be able to. As a barrier layer,
For example, polyvinyl alcohol, polyvinyl methyl ether, polyacrylic acid, methyl cellulose, ethyl cellulose, polyglutamic acid, casein, starch and other water-soluble resins, polyamide, polyimide, polyamide imide, polyamic acid, melamine resin, epoxy resin, polyurethane and polyglutamic acid ester Resins such as can be used. In particular, polyamide is preferable as the barrier layer in terms of coatability, adhesion, solvent resistance, electric barrier property, resistance and the like. As the polyamide, low crystalline or non-crystalline copolymerized nylon that can be applied in a solution state is suitable. Barrier layer thickness is 0.1-2μ
m is preferred.

In the electrophotographic photoreceptor of the present invention, a protective layer may be provided on the photosensitive layer. The protective layer is mainly composed of resin. Examples of the material forming the protective layer include polyester, polyurethane, polyarylate, polyethylene, polystyrene, polybutadiene, polycarbonate, polyamide, polypropylene, polyimide, polyamideimide, polysulfone, polyallyl ether, polyacetal, nylon, phenol resin, acrylic resin, Examples thereof include silicone resin, epoxy resin, urea resin, allyl resin, alkyd resin, butyral resin and the like. The thickness of the protective layer is 0.05 to 15 μm, and further 1 to
10 μm is preferable.

The support may be a metal or alloy such as aluminum, aluminum alloy, copper, titanium or stainless steel, or a polymer material such as polyethylene terephthalate, polybutylene terephthalate, phenol resin, polypropylene or polystyrene, or hard paper. It can be manufactured using the material. The shape of the support is cylindrical,
A belt shape or a sheet shape is preferable. When the material constituting the support has a high volume resistance, it is necessary to conduct a conductive treatment. The conductive treatment can be performed by forming a conductive thin film on the support or by dispersing a conductive substance in the support.

The electrophotographic photosensitive member of the present invention is not only used in electrophotographic copying machines, but also widely used in electrophotographic application techniques such as laser beam printers, CRT printers, LED printers, liquid crystal printers, facsimiles, and laser plate making. be able to.

The electrophotographic photosensitive member according to the present invention can realize stable potential characteristics and excellent image formation under all environments from low temperature and low humidity to high temperature and high humidity.

Next, an electrophotographic apparatus equipped with the electrophotographic photosensitive member of the present invention will be described. FIG. 1 shows a schematic structure of a transfer type electrophotographic apparatus using the drum type photoreceptor of the present invention. In the figure, 1 is a drum type photoreceptor of the present invention,
It is rotationally driven around the shaft 1a in the arrow direction at a predetermined peripheral speed. In the course of its rotation, the photosensitive member 1 is uniformly charged at its peripheral surface by a predetermined positive or negative potential by a charging means 2, and then at an exposure section 3 an optical image exposure L (slit exposure or slit exposure by an image exposure means not shown). Laser beam scanning exposure). As a result, electrostatic latent images corresponding to the exposed image are sequentially formed on the peripheral surface of the photoconductor. The electrostatic latent image is then toner-developed by the developing means 4, and the toner-developed image is synchronized with the rotation of the photoconductor 1 between the photoconductor 1 and the transfer means 5 from a paper feeding portion (not shown) by the transfer means 5. The images are sequentially transferred onto the surface of the recording material P that has been taken and fed. Recording material P that has received image transfer
Is separated from the surface of the photoconductor and introduced into the image fixing means 8 to undergo image fixing, and is printed out as a copy. After the image transfer, the surface of the photoconductor 1 is cleaned by the cleaning unit 6 to remove the transfer residual toner, and the pre-exposure unit 7 removes the charge to repeatedly use the image. As a uniform charging means 2 for the photoconductor 1, a corona charging device is generally widely used. Also, as the transfer device 5, corona transfer means is generally widely used. The electrophotographic apparatus is configured by integrally combining a plurality of constituent elements such as the photoconductor, the developing unit, and the cleaning unit described above as an apparatus unit, and the unit is configured to be detachable from the apparatus body. May be. For example, the photosensitive member 1 and the cleaning means 6 may be integrated into one device unit, and may be detachably configured by using guide means such as a rail of the device body. At this time, the above apparatus unit may be provided with a charging unit and / or a developing unit. When the electrophotographic apparatus is used as a copying machine or a printer, the light image exposure L uses reflected light or transmitted light from the original, or makes the original read into a signal and scans the laser beam in accordance with this signal. Or driving a light emitting diode array or a liquid crystal shutter array.

[0038]

【Example】

(Example 1) 120 parts by weight of powder (coating rate: 50% by weight, powder specific resistance: 30 Ωcm) comprising barium sulfate fine particles having a coating layer of indium oxide and a resol type phenol resin (Bryaufen J-325, Dainippon Ink and Chemicals) Chemical industry, 70% solid content) 70 parts by weight, 2-methoxy-
About 20 parts of a solution consisting of 100 parts by weight of 1-propanol
Disperse with a ball mill for hours. The average particle size of the filler contained in this dispersion was 0.20 μm.

The dispersion liquid prepared in this manner was used to give an outer diameter of 30.
14 mm, the aluminum cylinder having a length of 360 mm (surface roughness R _max 5 μm) was applied by the dipping method, and 14
By heat-curing for 30 minutes at 0 ° C, thickness 15μm
Was formed. Surface roughness R _max of the intermediate layer at this time
Was 0.5 μm. Incidentally, the roughness R _{ma x}
Is based on JIS B0601.

Next, a copolymer nylon resin (Amilan CM
(8000, manufactured by Toray) 10 parts by weight dissolved in a mixed solution of 60 parts by weight of methanol and 40 parts by weight of butanol is dip-coated on the intermediate layer, and dried by heating at 90 ° C. for 10 minutes to give a thickness of 0.5 μm. Barrier layer was formed.

Next, a solution consisting of 4 parts by weight of oxytitanium phthalocyanine pigment, 2 parts by weight of polyvinyl butyral resin (BX-1, manufactured by Sekisui Chemical Co., Ltd.) and 34 parts by weight of cyclohexanone was dispersed in a sand mill for 8 hours, and then 60 parts by weight of tetrahydrofuran. Parts were added to prepare a dispersion liquid for the charge generation layer. This dispersion was applied onto the above barrier layer by dip coating, and dried by heating at 80 ° C. for 10 minutes to form a charge generation layer. The film thickness of the charge generation layer was 0.2 μm.

Then, 50 parts by weight of a triarylamine compound represented by the following structure:

[0043]

[Outside 1] A solution prepared by dissolving 50 parts by weight of a polycarbonate resin (Iupilon Z-200, manufactured by Mitsubishi Gas Chemical Co., Ltd.) in 400 parts by weight of monochlorobenzene is dip-coated on the charge generation layer and heated and dried at 120 ° C. for 1 hour to give a thickness of 20 μm. Was formed on the charge transport layer.

The electrophotographic photosensitive member of the present invention thus prepared was mounted on a positive development electrophotographic copying machine,
The process of charging-exposure-developing-transfer-cleaning was repeated with a 0.8 second cycle. About this photoreceptor, low temperature and low humidity (15 ° C, 15% RH) and high temperature and high humidity (30 ° C,
The electrophotographic characteristics were evaluated under the environment of 85% RH). As a result, as shown in Table 1, this photoreceptor can form a large difference between the dark portion potential (V _D ) and the light portion potential ( _VL ) at both low temperature and low humidity and high temperature and high humidity. It was possible to obtain sufficient contrast. Further, when images were continuously printed on 10000 sheets of recording paper, both the dark portion potential and the light portion potential were hardly changed in any environment, and an image of extremely excellent image quality was stably obtained.

[0045]

Example 2 The aluminum cylinder was replaced with one having an outer diameter of 30 mm and a length of 260 mm, and the others were
An electrophotographic photosensitive member of the present invention was prepared in the same manner as in Example 1. The obtained electrophotographic photosensitive member was mounted on an electrophotographic printer of reversal development, and the process of charging-exposure-developing-transfer-cleaning was repeated in a cycle of 6 seconds. The electrophotographic characteristics of this photoconductor were evaluated under the environment of low temperature and low humidity (15 ° C., 15% RH) and high temperature and high humidity (30 ° C., 85% RH). As a result, as shown in Table 2, this photoconductor can form a large difference between the dark part potential (V _D ) and the light part potential ( _VL ) even at low temperature and low humidity and high temperature and high humidity. We were able to obtain sufficient contrast. Furthermore, when images were continuously printed on 5000 sheets of recording paper, both the dark part potential and the light part potential hardly changed in any environment, and the image quality was excellent without unnecessary black spot images or fog. The image of was stably obtained.

[0047]

(Examples 3 to 5) The intermediate layer of Example 1 was replaced with an intermediate layer formed by using the following coating liquid, and otherwise the same as in Example 1, except that each of Examples 3 to 5 was changed. An electrophotographic photoconductor of was prepared. The average particle size of the filler contained in the coating liquid for intermediate layer of Example 3 was 0.25 μm. The average particle size of the filler contained in the coating liquid for intermediate layer of Example 4 was 0.23 μm.

The electrophotographic photosensitive members thus prepared were evaluated in the same manner as in Example 1. As a result, these photoreceptors form a large difference between the dark potential (V _D ) and the bright potential ( _VL ) at both low temperature and low humidity and high temperature and high humidity as shown in Table 3. It was possible to obtain sufficient contrast. Furthermore, 1 in succession
When an image was printed on 0000 sheets of recording paper, neither the dark part potential nor the light part potential changed substantially in any environment, and an image of very excellent image quality was stably obtained.

Powder containing barium sulfate fine particles having a coating layer of the coating solution and zinc oxide of Example 3 (covering rate 50% by weight, powder specific resistance 200 Ωcm)
150 parts by weight-70 parts by weight of the same resole type phenolic resin as in Example 1-100 parts by weight of 2-methoxy-1-propanol

Coating liquid of Example 4・ Powder composed of barium sulfate fine particles similar to Example 1
120 parts by weight Polyester polyurethane (Nipporan 2304, made by Nippon Polyurethane) 70 parts by weight 2-Methoxy-1-propanol 100 parts by weight

Coating liquid of Example 5・ Powder composed of barium sulfate fine particles similar to that of Example 3
100 parts by weight Polyamic acid resin having the following structural formula (weight average molecular weight 85
00) 50 parts by weight

[0053]

[Outside 2] -N, N-dimethylacetamide 170 parts by weight

[0054]

[Outside 3]

(Comparative Examples 1 and 2) The intermediate layer of Example 1 was
Electrophotographic photoreceptors of Comparative Examples 1 and 2 were produced in the same manner as in Example 1 except that the intermediate layer formed using the coating liquid described below was used. The average particle size of the filler contained in the coating liquid for intermediate layer of Comparative Example 1 was 0.25 μm.
The average particle size of the filler contained in the coating liquid for intermediate layer of Comparative Example 2 was 0.20 μm.

The electrophotographic photosensitive members thus prepared were evaluated in the same manner as in Example 1. As a result, as shown in Table 4, any of the photoconductors can form a large difference between the dark portion potential (V _D ) and the light portion potential ( _VL ) in the initial stage, and sufficient contrast can be obtained. However, when images were continuously formed on 10000 sheets of recording paper, a drop in dark part potential and a rise in light part potential were observed in all electrophotographic photoconductors under a low temperature and low humidity environment.

Powder of fine particles of titanium oxide having a coating layer of the coating liquid of Comparative Example 1 and antimony-containing tin oxide (ECTT-1, manufactured by Titanium Industry Co., Ltd.)
150 parts by weight-Resol type phenolic resin similar to Example 1 75 parts by weight-Methylcellosolve 60 parts by weight-Methanol 15 parts by weight

Powder of the coating liquid of Comparative Example 2 and tin oxide fine particles containing antimony (T-
100 parts by weight of Mitsubishi Materials) 70 parts by weight of the same polyester polyurethane as in Example 5 80 parts by weight of 2-methoxy-1-propanol

[0059]

[Outside 4]

(Examples 6 to 8) Example 6 (using the intermediate layer of Example 3) was carried out in the same manner as in Examples 3 to 5 except that the aluminum cylinder had an outer diameter of 30 mm and a length of 260 mm. , Example 7 (using the intermediate layer of Example 4)
And an electrophotographic photoreceptor of Example 8 (using the intermediate layer of Example 5) was prepared.

The electrophotographic photosensitive members thus prepared were evaluated in the same manner as in Example 2. As a result, as shown in Table 5, these photoconductors can form a large difference between the dark potential (V _D ) and the light potential ( _VL ) even at low temperature and low humidity and high temperature and high humidity. It was possible to obtain a good contrast. Furthermore, when images were continuously printed on 5000 sheets of recording paper, both the dark part potential and the light part potential hardly changed in any environment, and the image quality was excellent without unnecessary black spot images or fog. The image of was stably obtained.

[0062]

[Outside 5]

(Comparative Examples 3 and 4) Comparative Example 3 (Comparative Example 1) was carried out in the same manner as in Examples 1 and 2 except that the aluminum cylinder had an outer diameter of 30 mm and a length of 260 mm.
Of the electrophotographic photosensitive member of Comparative Example 4 (using the intermediate layer of Comparative Example 2).

The electrophotographic photosensitive members thus prepared were evaluated in the same manner as in Example 2. As a result, as shown in Table 6, any of the photoconductors can form a large difference between the dark portion potential (V _D ) and the light portion potential ( _VL ) in the initial stage, and a sufficient contrast can be obtained. However, when images were continuously formed on 5000 sheets of recording paper, a drop in the dark area potential was observed in any of the electrophotographic photoreceptors under a high temperature and high humidity environment. In the high temperature and high humidity environment, unnecessary black dots were observed on the recording paper from the beginning.

[0065]

[Outside 6]

(Example 9) The dispersion liquid for intermediate layer used in Example 1 was coated on the same aluminum cylinder as in Example 1 by the dipping method, and dried and cured at 140 ° C for 30 minutes to give a thickness of 6 µm. Was formed.

Next, to 5 parts by weight of a bisazo pigment having the following structural formula,

[0068]

[Outside 7] 90 parts by weight of tetrahydrofuran was added and dispersed by a sand mill for 20 hours. A solution of 2.5 parts by weight of butyral resin (BLS, manufactured by Sekisui Chemical Co., Ltd.) in 20 parts by weight of tetrahydrofuran was added to this liquid, and the mixture was further dispersed for 2 hours. To this dispersion, 100 parts by weight of cyclohexanone and 100 parts by weight of tetrahydrofuran were added for dilution, and the intermediate layer was coated with a Mayer bar to a thickness of 0.2 μm to form a charge generation layer.

Then, 50 parts by weight of a styryl compound having the following structural formula,

[0070]

[Outside 8] A solution prepared by dissolving 50 parts by weight of a polycarbonate resin (Iupilon Z-200, manufactured by Mitsubishi Gas Chemical Co., Ltd.) in 400 parts by weight of monochlorobenzene is dip-coated on the charge generation layer, and dried by heating at 120 ° C. for 1 hour to have a thickness of 20 μm. The charge transporting layer was formed to prepare an electrophotographic photoreceptor of the present invention.

The electrophotographic photosensitive member thus prepared was evaluated in the same manner as in Example 1. As a result, these photoreceptors form a large difference between the dark portion potential (V _D ) and the light portion potential ( _VL ) at both low temperature and low humidity and high temperature and high humidity as shown in Table 7. It was possible to obtain sufficient contrast, but when images were continuously printed on 10000 sheets of recording paper, both the dark part potential and the light part potential did not change in any environment, and it was extremely high. Images with excellent image quality were also stably obtained.

[0072]

Example 10 An electrophotographic photosensitive member of the present invention was prepared in the same manner as in Example 9 except that the intermediate layer dispersion liquid used in Example 3 was used.

The electrophotographic photosensitive member thus prepared was evaluated in the same manner as in Example 1. As a result, as shown in Table 8, this photosensitive member is capable of forming a large difference between the dark portion potential (V _D ) and the light portion potential ( _VL ) even at low temperature and low humidity and high temperature and high humidity. It was possible to obtain a good contrast. Further, when images were continuously printed on 10000 sheets of recording paper, both the dark portion potential and the light portion potential were hardly changed in any environment, and an image of extremely excellent image quality was stably obtained.

[0075]

[Brief description of drawings]

FIG. 1 is a side view showing an example of an electrophotographic apparatus using an electrophotographic photosensitive member of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electrophotographic photosensitive member 2 Charging means 3 Exposure part 4 Developing means 5 Transfer means 6 Cleaning means 7 Pre-exposure means 8 Image fixing means

Claims (7)

[Claims] 1. An electrophotographic photoreceptor having an intermediate layer and a photosensitive layer in this order on a conductive support, the intermediate layer containing a powder of barium sulfate fine particles having a coating layer, and the coating layer. Is formed from a compound selected from the group consisting of indium oxide, zinc oxide, zirconium oxide and cadmium sulfide. 2. The electrophotographic photosensitive member according to claim 1, wherein the coating rate of the coating layer is 10 to 80% by weight. 3. The electrophotographic photosensitive member according to claim 2, wherein the coverage is 30 to 60% by weight. 4. The binder resin for the intermediate layer is selected from the group consisting of phenol resin, polyurethane, polyamide, polyimide, polyamideimide, polyamic acid, polyvinyl acetal, epoxy resin, acrylic resin, melamine resin and polyester. The electrophotographic photosensitive member according to claim 1, wherein the electrophotographic photosensitive member is used. 5. A phenol resin as the binder resin,
The electrophotographic photosensitive member according to claim 4, wherein a member selected from the group consisting of polyurethane and polyamic acid is used. 6. The electrophotographic photosensitive member according to claim 1, further comprising a barrier layer between the intermediate layer and the photosensitive layer. 7. The electrophotographic photosensitive member according to claim 1, a charging unit for charging the photosensitive member, an image exposing unit for performing an image exposure on the charged photosensitive member to form an electrostatic latent image, and a static imager. An electrophotographic apparatus, comprising: a developing unit that develops the photoconductor on which an electrostatic latent image is formed with toner.