JPS6344661A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To enhance electric charge acceptance and charge retentivity and to prevent deterioration of sensitivity by dividing a charge generating layer into multiple layers and lowering the content of a charge generating material in one of these layers. CONSTITUTION:The content of the charge generating material in the layer 2a of the plural charge generating layers 2a, 2b is made lower than that of the other layer 2b, thus permitting injection of excessive charge carriers to be prevented in the dark, and charge acceptance and retentivity to be enhanced. Besides, since the layer 2a contains the charge generating material, and it is allowed to generate charge pairs at the time of exposure and exhibits photoconductivity, deterioration of sensitivity and rise of residual potential can be suppressed.

Description

[Detailed Description of the Invention] [Summary] In an electrophotographic photoreceptor constructed by laminating a charge generation layer and a charge transport layer, the charge generation layer is divided into multiple layers, and the content of a charge generation substance in one of the layers is determined. is reduced to improve charge acceptance and charge retention, and to suppress a decrease in sensitivity.

[Industrial application field]

The present invention relates to an electrophotographic photoreceptor, and particularly to an electrophotographic photoreceptor that improves charge acceptance and charge retention and prevents a decrease in sensitivity.

Electrophotographic systems are widely applied and popular in the fields of laser printers, copying machines, etc.The process involves first uniformly charging the surface of a photoreceptor, either positively or negatively, and then exposing it to light using a laser, LED, etc. An electrostatic latent image is formed on the surface of the photoreceptor. This electrostatic latent image is developed with toner to become a visible image, and then transferred onto paper and fused and fixed by heat or light. Get the print by.

The photoreceptor used here must be easily charged in the dark (charge receptivity), have little dark decay after charging (charge retention), and quickly dissipate surface charge when exposed to light. In addition to characteristics such as (sensitivity), stability of charging and exposure processes in continuous printing, rigidity such as abrasion resistance, environmental pollution resistance, cost, etc. are important conditions.

[Conventional technology]

In order to satisfy the above conditions, functionally separated laminated photoreceptors have been proposed in recent years.

As shown in Fig. 2, this functionally separated laminated photoreceptor has the following features:
It is constructed by laminating a charge generation layer 2 and a charge transport layer 3 on a conductive support 1 .

The charge generation layer 2 is formed by depositing a charge generation substance or by finely dispersing it in a binder resin.
The film thickness is 0.05 to 3μ.

As the charge generating substance, well-known azo pigments, phthalocyanine pigments, perylene pigments, squarylium, etc. are used, and as the binder resin, polyamide, epoxy, polyester, polyvinyl butyral, etc. are used.

The charge transport layer 3 is formed by dissolving the charge transport OI material and the binder resin as usual, and has a film thickness of 7 to 30 μm.

Well-known charge transport substances include chloranil, bromanil,
Electron transporting substances such as trinitrofluorenone and tetranitrofluorenone, or hole transporting substances such as hydrazone compounds, pyrazoline compounds, and oxazole compounds are used, and binder resins include polycarbonate, polyester, and acrylic-styrene. Resins such as are used.

When the surface of this photoreceptor is first positively or negatively charged by an electrophotographic process, a negative (or positive) charge is induced on the trielectric support side. When light is subsequently irradiated, the charge generating substance in the charge generating layer 2 absorbs this light and becomes excited, generating pairs of electrons and holes. When the surface is positively charged, the generated holes flow into the conductive support, while the generated electrons are transported to the surface in the charge transport layer 3 by an electron transporting charge transport material, and the surface is An electrostatic latent image is formed by neutralizing the charge.

In conventional laminated photoreceptors, the charge generation layer 2, which has a high content of charge generation material (i.e., one layer), is directly laminated on the conductive support 1, so a high electric field is applied due to charging. In this case, even in the absence of light irradiation, charge carriers are injected from the conductive support into the charge generation layer in a large amount (and the charge acceptance and charge retention properties are deteriorated).

In order to solve this problem, as shown in FIG. 3, an insulating undercoating layer 4 having a thickness of approximately 0.2 to 5 μm may be provided between the conductive support 1 and the charge generation layer 2. Proposed. As the undercoat layer 4, resins such as polyvinyl alcohol, polyvinyl acecool, polyamide, epoxy, casein, cellulose, etc. are used.

However, since such an undercoat layer 4 is inherently insulative, although the charge acceptance and charge retention properties are improved, problems arise in that the sensitivity is lowered and the residual potential is increased.

An object of the present invention is to provide an electrophotographic photoreceptor that has improved charge acceptance and charge retention without causing a decrease in sensitivity.

[Means for solving problems]

According to the present invention, the above problem can be solved by providing an electrophotographic photoreceptor constructed by laminating a charge generation layer and a charge transport layer on a conductive support, in which the charge generation layer is composed of a plurality of layers, and the charge generation layer is composed of a plurality of layers. The problem is solved by an electrophotographic photoreceptor characterized in that the content of a charge-generating substance contained in one of the charge-generating layers is smaller than the content of a charge-generating substance contained in the other charge-generating layer. .

In the present invention, well-known charge generating substances and binder resins can be used to form the charge generating layer. Further, the charge generating substance and the binder resin in each charge generating layer may be made of the same material or different materials. The thickness of each layer is preferably 0.05 to 1 .mu.m, and the total thickness is preferably 3 .mu.m or less from the viewpoint of sensitivity and charge retention.

As the charge transport layer, a conventionally used charge transport substance dissolved in a binder resin, a photoconductive resin, or the like can be used.

[For production]

By providing a layer with a small content of a charge-generating substance, it is possible to prevent injection of excess charge carriers in the dark, and it is possible to improve charge acceptance and charge retention. Moreover, since this layer contains a charge-generating substance, charge pairs are generated during exposure and exhibits thick conductivity, making it possible to suppress a decrease in sensitivity and an increase in residual potential.

〔Example〕

Embodiments of the present invention will be described below along with comparative examples based on the drawings.

Example l β-type copper phthalocyanine O, S parts Polyester resin 9.5 parts Tetrahydrofuran 90 parts A solution of the above composition was mixed with a ball mill for 20 parts.
After dispersing for a time, a coating solution was prepared by adding 0.3 parts of Coronate L and 400 parts of tetrahydrofuran. The obtained coating solution was applied using a doctor blade onto a polyester film on which aluminum, which would become the conductive support 1, was vapor-deposited to a thickness of about 6,000 mm.
After air drying, it was dried at 140° C. for 1 hour to obtain a first charge generation layer 2a having a thickness of about 0.7 μm.

Next, a coating solution prepared in the same manner as above except that 5 parts of β-type copper phthalocyanine, 5 parts of polyester resin, and 0.15 parts of Coronate L was used was applied onto the previously formed charge generation layer. The second charge generation layer 2b having a thickness of about 0.8 μm was formed by coating and drying in the same manner as described above. The second charge generation J
P-diethylaninobenzaldehyde diphenylhydrapun and polycarbonate (weight ratio 1:1) on 'i2b
A charge transport layer 3 was formed, and an electrophotographic photoreceptor IO according to the present invention was obtained. In this example, the content of the charge generating substance β-type copper phthalocyanine in the charge generating layer 2a is 5%, and the content of the charge generating substance in the charge generating layer 2b is 50%.
Met.

Comparative Example 1 A photoreceptor 10 of Comparative Example 1 (conventional example) was obtained in exactly the same manner as in Example 1 except that the first charge generation layer 2a was not provided.

Comparative Example 2 In Example 1, when forming the first charge generation layer, β
Photoconductor 1 of Comparative Example 2 (conventional example) was prepared in exactly the same manner except that the insulating undercoat layer was formed without adding type fluorocyanine.
I got 0.

The three types of photoreceptors obtained in this way were tested at a corona voltage of -5,
It was charged at 5kV, and after 1 second, a helium-neon laser beam was applied, and the initial potential was determined by a high-speed surface potentiometer with a transparent probe. , half-reduction exposure amount E, /2, and residual potential ■, were measured. Here, (■) is the surface potential after a time 10 times the time required for the surface potential to decrease by half. Also,
In the same way, measurements were made without incident light, and 20
The rate at which the surface potential attenuates per second [)zo was determined. The results are shown in Table 1.

Vo relates to charge acceptance, E, /2 relates to sensitivity, and D2° relates to charge retention.

According to Table 1, it seems that the sensitivity and residual potential of Example are worse than Comparative Example 1, but as is clear from the D2° results, Comparative Example 1 has larger dark decay. This is due to a number of reasons.

Furthermore, in Comparative Example 2, since the first charge generation layer (insulating layer 4) is composed only of resin, which is an insulator, sensitivity and residual potential deteriorate.

In the embodiments of the present invention, only two charge generation layers are shown, but three, four, . . . n layers may of course be used.

However, it is necessary that the content of the charge generating substance, such as the above-mentioned β-type copper phthalocyanine, in one of the plurality of layers is smaller than the content of the charge generating substance in the other layers. It is preferable to set it to about 50% or less.

〔Effect of the invention〕

As explained above, according to the present invention, charge acceptance and charge retention can be improved compared to conventional charge generation layers with fluorescent ones. Furthermore, the sensitivity and residual potential are improved compared to the conventional method using an insulating undercoat layer to solve this problem.

[Brief explanation of drawings]

FIG. 1 is a sectional view for explaining one embodiment of the present invention, and FIGS. 2 and 3 are comparative examples (conventional example) 1.
FIG. DESCRIPTION OF SYMBOLS 1... Conductive support, 2, 2a, 'lb... Charge generation layer, 3... Charge transport layer, 4... Insulating undercoat layer, 10... Anger photoreceptor.

Claims (1)

[Scope of Claims] 1. An electrophotographic photoreceptor configured by laminating a charge generation layer (2) and a charge transport layer (3) on a conductive support (1), comprising: ) is comprised of a plurality of layers, and is characterized in that the content of the charge-generating substance contained in one of the plurality of charge-generating layers is smaller than the content of the charge-generating substance contained in the other charge-generating layers. A photoreceptor for electrophotography.