JPH0915889A - Electrophotographic photoreceptor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor of high performance excellent in charge holding capacity and environmental stability and low in residual potential in the photoreceptor of high sensitivity using TiOPc or τ-type nonmetallic phthalocyanine for charge generating material. SOLUTION: In an electrophotographic photoreceptor of high sensitivity using oxotitanium phthalocyanine for charge generating material, an intermediate layer 11 formed by dispersing a perylene-3,4,9,10-tetracarboxylic acid-bis(phenethylimide) pigment in binder resin is provided between a base body 10 and a charge generating layer 12. Hole injection from the base body is thereby controlled so as to provide the electrophotographic photoreceptor of high charge holding capacity.

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 used for forming an image by an electrophotographic process such as a copying machine, a printer or a facsimile.

[0002]

2. Description of the Related Art In an electrophotographic process, a surface of a photoconductor having photoconductivity is charged by corona discharge or the like, and then is charged.
This is a process for forming an image by performing image exposure to form an electrostatic latent image and visualizing the image by developing with toner. The electrophotographic photoreceptor used in this process needs to have an excellent charging ability in a dark place and an ability to quickly eliminate the charged charge by light irradiation.

Conventionally, an electrophotographic photosensitive member has been made of selenium (S
e), cadmium sulfide (CdS), zinc oxide (Zn)
O), an inorganic photoconductive compound such as amorphous silicon has been used as a main component, but there are problems such as productivity and harmfulness. To overcome these problems, photoconductors containing an organic photoconductive substance as a main component have been actively developed and put into practical use. Furthermore, organic photoconductive substances can have sensitivity in the near infrared wavelength range, which was difficult with inorganic photoconductors, by changing the molecular structure and crystal form. It is very important as a photosensitive member for a digital electrophotographic process using a semiconductor laser having an oscillation wavelength in an infrared wavelength region as a light source.

In an electrophotographic photosensitive member using an organic photoconductive material, a paint containing a charge generating material and a paint containing a charge transport material are sequentially applied to an aluminum (including an aluminum alloy) support, dried, and dried. 2. Description of the Related Art A function-separated type electrophotographic photosensitive member having a generation layer and a charge transport layer formed thereon is widely used.

In particular, in recent years, oxotitanium phthalocyanine (hereinafter referred to as T
Attention has been paid to τ-type metal-free phthalocyanines, and these have been put to practical use as charge generation materials for photoconductors. T
Most photoreceptors using iOPc or τ-type non-metal phthalocyanine for the charge generation layer are negatively charged laminated photoreceptors combined with a hole transport layer.

[0006]

The photoreceptor using the above-mentioned TiOPc or τ-type non-metallic phthalocyanine has a small ionization potential (5.24 eV, τ
Since 5.03 eV of a non-metallic phthalocyanine type (measurement result by a surface analysis apparatus AC-1 manufactured by Riken Keiki), holes are easily injected from the aluminum support, and the charge holding ability of the photoreceptor tends to be low. Therefore, as a method of controlling hole injection from the support, an intermediate layer is often provided between the aluminum support and the charge generation layer.

As the above-mentioned intermediate layer, a polyamide resin,
An undercoat layer formed of an acrylate resin, polyurethane, or the like, or an oxide film formed by anodizing the surface of an aluminum support is used as a single layer or a stacked layer. However, the undercoat layer has the disadvantage that the resistance value changes greatly with changes in temperature and humidity, and when the oxide film is thin, the control of hole injection is insufficient, and when the oxide film is thick, the residual potential of the photoconductor is reduced. There is a drawback to make it expensive.

Therefore, an object of the present invention is to provide a high-sensitivity photoreceptor using TiOPc or τ-type non-metallic phthalocyanine as a charge generating material, which is excellent in charge retention ability and environmental stability, and has high performance with low residual potential. An object of the present invention is to provide an electrophotographic photosensitive member.

[0009]

The electrophotographic photoreceptor according to the present invention is a high-sensitivity photoreceptor using TiOPc or τ-type non-metallic phthalocyanine as a charge generating material, and has a structure between an aluminum support and a charge generating layer. By having an intermediate layer for controlling the injection of holes from the support, it has a high charge retention ability. The intermediate layer is perylene-3,4,9,
A 10-tetracarboxylic acid-bis (phenethylimide) pigment is formed by dispersing in a binder resin. The structural formula of the pigment is as follows.

[0010]

Embedded image The binder resin for dispersing and fixing the pigment, polyvinyl chloride, polyvinyl acetate, polyvinyl butyral, polyvinyl formal, polyester, polyurethane, polycarbonate, acrylic resin, phenol resin alone,
Alternatively, two or more kinds are used in combination. As a method of forming the intermediate layer by dispersing the above-described pigment in a binder resin, specifically, the above-described pigment and the binder resin, toluene, xylene, monochlorobenzene, methyl alcohol, ethyl alcohol, ethyl acetate, methylene chloride, A coating material dissolved or dispersed in a solvent such as tetrahydrofuran or cyclohexane is used, and the coating material is applied on an aluminum support to form an intermediate layer. Further, an additive such as an antioxidant can be used in the paint applied on the aluminum support, if necessary.
Known methods such as a spin coater, an applicator, a spray coater, a bar coater, a dip coater, and a doctor blade are used for these coating methods.

The perylene-3,4,9,10-tetracarboxylic acid-bis (phenethylimide) pigment has a suitably high ionization potential (5.50 eV: the result measured by a surface analyzer AC-1 manufactured by Riken Keiki). When this pigment is used for the intermediate layer, it acts as a barrier against hole injection from the aluminum support, and improves the charge holding ability of the photoreceptor. Further, since the electric resistance of the intermediate layer in a dark place is close to that of the charge generation layer, it hardly affects the residual potential of the photoconductor. In the case where the charge generation material is a dispersion-fixed TiOPc, in order to sufficiently obtain such a result, 20 to 70 parts by weight, preferably 45 to 60 parts by weight of the pigment is dispersed in the binder resin of the intermediate layer. To form an intermediate layer. However, the weight here is 100 in total of the pigment and the binder resin. The thickness of the intermediate layer is 0.1 to 10 μm, preferably 0.1 to 1 μm. If the amount of the dispersed pigment is small, the characteristics of the resin are reflected, leading to an increase in the residual potential and a decrease in environmental stability. If the amount is large, the film-forming property of the intermediate layer is deteriorated, causing problems such as image unevenness and peeling of the organic layer from the support. Occurs. The same effect can be obtained even if the surface of the aluminum support to which the intermediate layer is applied is anodized.

On the other hand, when the charge generating material is a dispersion-fixed τ-type metal-free phthalocyanine, the pigment is added to the binder resin in an amount of 0.1 to obtain the above-mentioned effect sufficiently.
The intermediate layer is formed by dispersing 1 to 3 equivalents (equivalent is a ratio when the binder resin is 1), preferably 0.5 to 2 equivalents. At this time, the thickness of the intermediate layer is 0.01 to 10 μm.
m, preferably 0.05 to 3 μm.

The charge generation layer formed on the intermediate layer has a T
It is formed by iOPc or τ type metal-free phthalocyanine and a binder resin for dispersion fixing, and additives such as an antioxidant and a dispersant are added if necessary.

As the binder resin for fixing the charge generating material dispersedly, polyvinyl chloride, polyvinyl acetate,
Polyvinyl butyral, polyvinyl formal, polyester, polyurethane, polycarbonate, acrylic resin, phenol resin and the like are used alone or in combination of two or more.

Specifically, the charge generation layer is made of TiOPc or τ-type non-metallic phthalocyanine and a binder resin, such as toluene, xylene, monochlorobenzene, methyl alcohol, ethyl alcohol, ethyl acetate, methylene chloride,
Dissolved in solvents such as tetrahydrofuran and cyclohexane,
Alternatively, it is formed by applying a dispersed paint on the intermediate layer. As the solvent used at this time, toluene, xylene, monochlorobenzene, methyl alcohol, ethyl alcohol, ethyl acetate, methylene chloride, tetrahydrofuran, cyclohexane and the like are used, and these solvents are used alone or as a mixture. These coating methods are:
Spin coater, applicator, spray coater,
A known method such as a bar coater, a dip coater, and a doctor blade is used. The thickness of the charge generation layer is 0.05
To 5 μm, preferably about 0.1 to 2 μm.

The charge transport layer formed on the charge generation layer is coated with a paint for the charge transport layer formed by dissolving or dispersing a charge transport material and a binder resin for dispersing and fixing the same in a solvent. It is formed by processing. Additives such as antioxidants, surface lubricants, and ultraviolet absorbers can be used in the charge transport layer coating. Charge-transporting materials include poly-N-vinyl carbazole and derivatives thereof,
Pyrene-formaldehyde condensate and its derivative, polysilane and its derivative, oxazole derivative, oxadiazole derivative, monoarylamine derivative, diarylamine derivative, triarylamine derivative, stilbene derivative, benzidine derivative, pyrazoline derivative,
Known materials such as hydrazone derivatives and butadiene derivatives are exemplified. The charge transport materials can be used alone or in combination of two or more. As the binder resin for dispersing and fixing the charge transporting material, polyvinyl chloride, polyvinyl acetate, polyvinyl butyral, polyvinyl formal, polyester, polyurethane, polycarbonate, acrylic resin, phenol resin and the like are used. These resins can be used alone or in combination of two or more. As the solvent, toluene, xylene, monochlorobenzene, methyl alcohol, ethyl alcohol, ethyl acetate, methylene chloride, tetrahydrofuran, cyclohexane or the like is used. These solvents may be used alone or as a mixture.

The thickness of the charge transport layer is suitably from 5 to 40 μm, preferably from about 15 to 25 μm. A known method such as a spin coater, an applicator, a spray coater, a bar coater, a dip coater, and a doctor blade is used as a method for applying the charge transport layer.

[0018]

In a high-sensitivity electrophotographic photoreceptor using TiOPc or τ-type metal-free phthalocyanine as a charge generation material, a perylene-photosensitive material is provided between an aluminum support and a charge generation layer.
By providing an intermediate layer formed by dispersing 3,4,9,10-tetracarboxylic acid-bis (phenethylimide) pigment in a binder resin, hole injection from the support is controlled, and the charge retention ability is high. An electrophotographic photosensitive member can be provided.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a partial sectional view of an electrophotographic photosensitive member according to the present invention. In FIG. 1, an electrophotographic photoreceptor has an aluminum support 10 and an intermediate layer containing perylene-3,4,9,10-tetracarboxylic acid-bis (phenethylimide) coated on the aluminum support 10. 11
And a charge generation layer 12 applied on the intermediate layer 11 and a charge transport layer 13 applied on the charge generation layer 12. First, an example in which a oxotitanium phthalocyanine dispersed film is used for the charge generation layer will be described.

(Example 1) First, perylene-3,4
2 parts of 9,10-tetracarboxylic acid-bis (phenethylimide) pigment (parts by weight, the same applies hereinafter) and 2 parts of polyvinyl butyral as a binder resin were dispersed in a ball mill for 24 hours together with 96 parts of tetrahydrofuran as a solvent, and the mixture was subjected to an intermediate treatment. A layer coating was prepared.

2 parts (parts by weight, hereinafter the same) of oxotitanium phthalocyanine having an infrared absorption spectrum shown in FIG. 2 and 2 parts of polyvinyl butyral as a binder resin are dispersed together with 96 parts of tetrahydrofuran in a ball mill for 24 hours to form a charge generation layer. Paint was prepared.

Twenty parts of the charge transport material represented by the chemical formula 2 and 20 parts of polycarbonate (Z-200, manufactured by Mitsubishi Gas Chemical) were dissolved in 60 parts of methylene chloride to prepare a charge transport layer paint.

[0024]

Embedded image The paint for the intermediate layer, the paint for the charge generation layer, and the paint for the charge transport layer are sequentially immersed and coated on an aluminum support whose surface has not been anodized, so that the intermediate layer (0.2 μm) and the charge generation layer (0. 2 μm) and a charge transport layer (20 μm) to form a laminated electrophotographic photoreceptor. For this electrophotographic photoreceptor, the half-life exposure sensitivity, the charge retention rate after 5 seconds from charging, and the residual potential were measured using an electrostatic charging tester (E Kawasaki E
PA8200).

Example 2 A laminated electrophotographic photosensitive member was prepared and evaluated in the same manner as in Example 1 except that an oxidized skin was formed by anodizing the surface of the aluminum support.

Example 3 Perylene-3,4,9,10
-An intermediate layer coating prepared by dispersing 0.4 part (parts by weight, hereinafter the same) of tetracarboxylic acid-bis (phenethylimide) pigment and 3.6 parts of polyvinyl tylal in a ball mill for 24 hours together with 96 parts of tetrahydrofuran. A laminated electrophotographic photoreceptor was prepared and evaluated in the same manner as in Example 1 except for the above.

(Comparative Example 1) An aluminum support surface was anodized to form an oxide film, and then a charge generation layer and a charge transport layer were formed and laminated as in Example 1 without forming an intermediate layer. An electrophotographic photoreceptor was prepared and evaluated.

Comparative Example 2 A laminated electrophotographic photosensitive member was prepared and evaluated in the same manner as in Example 1 except that the intermediate layer was formed of a polyamide resin.

Comparative Example 3 A laminated electrophotographic photosensitive member was prepared and evaluated in the same manner as in Example 2 except that the intermediate layer was formed of a polyamide resin.

The results are shown in Tables 1 and 2. Table 1 shows the evaluation results at a temperature of 25 ° C. and a humidity of 50% at the time of evaluation.
Table 2 shows the evaluation results at a temperature of 35 ° C. and a humidity of 80% at the time of evaluation.

[0031]

[Table 1]

[0032]

[Table 2] Compared to the photoconductor of Comparative Example 1, the photoconductors of Examples 1, 2, and 3 each including the intermediate layer according to the present invention have improved charge retention. In the photoreceptors of Examples 1 and 2, both the residual potential and the half-life exposure sensitivity were the same as those of Comparative Example 1.
An electrophotographic photoreceptor improved in only the charge retention rate was obtained. In Example 3, perylene-3, 4, 9,
Since the amount of the 10-tetracarboxylic acid bis (phenethylimide) pigment is small, the residual potential is greatly increased with respect to environmental changes.

On the other hand, the photoreceptors of Comparative Examples 2 and 3 were prepared by forming an intermediate layer with resin alone without using perylene-3,4,9,10-tetracarboxylic acid-bis (phenethylimide) pigment. The charge retention rate is improved in an environment of 25 ° C. and 50% humidity. However,
These have the disadvantage that the charge retention rate decreases significantly under high temperature and high humidity (35 ° C., 80% humidity) and the disadvantage that the residual potential greatly increases. In the first and second embodiments, the rise of the residual potential with respect to the environmental change is suppressed to 8V.

Next, an example in which a τ-type metal-free phthalocyanine dispersion film is used for the charge generation layer will be described.

Example 4 Perylene-3,4,9,10
-Tetracarboxylic acid-bis (phenethylimide) 0.7
5 parts, polyvinyl butyral resin (BH, manufactured by Sekisui Chemical Co., Ltd.)
-3) With a ball mill, dispersion was performed for 10 hours together with 0.75 part and 30 parts of tetrahydrofuran. Using this as a coating solution, an intermediate layer having a thickness of 0.2 μm was formed on an aluminum plate.

Next, 1 part of τ-type metal-free phthalocyanine was added to polyvinyl butyral resin (BX-1 manufactured by Sekisui Chemical Co., Ltd.) 1
Parts, 15 parts with a ball mill together with 40 parts of tetrahydrofuran
Time dispersion was performed. This coating solution has a dry thickness of 0.2 μm
Was applied on the intermediate layer to form a charge generation layer.

Further, a solution prepared by dissolving 20 parts of a charge transport material represented by the following general formula 3 and 20 parts of a polycarbonate resin (Z-200 manufactured by Mitsubishi Gas Chemical Company) in 100 parts of methylene chloride has a dry film thickness of 20 μm. To form a charge transport layer on the uppermost layer.

[0038]

Embedded image In this way, an electrophotographic photosensitive member having a laminated photosensitive layer is manufactured, and an electrostatic recording paper test apparatus (EP manufactured by Kawaguchi Electric Co., Ltd.)
A-8100), the electrophotographic characteristics were evaluated. That is,
Initial potential (V ₀ ) when charged by corona discharge of −5 kV, residual potential (V _resi ) after irradiating 5 lux of white light for 5 seconds, and exposure amount (E required to reduce initial potential by half) _2/1 ), and the charge retention (DDR) was measured.

Example 5 Perylene-3,4,9,10
-Tetracarboxylic acid-bis (phenethylimide) 0.5
Parts, polyvinyl butyral resin (BH-3) 1.0 part,
A sample was prepared and evaluated in the same manner as in Example 4, except that a coating solution dispersed in a ball mill for 10 hours together with 30 parts of tetrahydrofuran was used.

Example 6 Samples were prepared and evaluated in the same manner as in Example 4 except that the surface of the aluminum plate was anodized to form an oxide film.

Comparative Example 4 A sample was prepared and evaluated in the same manner as in Example 4 except that a polyamide resin (T-8 manufactured by Teijin Limited) was used for the intermediate layer.

Comparative Example 5 A sample was prepared and evaluated in the same manner as in Example 4 except that no intermediate layer was provided.

The results are shown in Tables 3 and 4. Table 3 shows normal temperature and humidity (25 ° C. 50%), and Table 4 shows high temperature and high humidity (35 ° C. 80%).
%). In Comparative Example 5, the charge retention was low because no intermediate layer was provided. However, in Examples 4, 5, and 6 having an intermediate layer containing perylene-3,4,9,10-tetracarboxylic acid-bis (phenethylimide) of the present invention, the charge retention was improved. Further, in Comparative Example 4, the charge retention was improved by providing an intermediate layer of a polyamide resin, but the residual potential was high. However, in Examples 4, 5, and 6, the residual potential also has a low value. Furthermore, in Comparative Example 4, a decrease in charge retention at high temperature and high humidity is observed.

[0044]

[Table 3]

[0045]

[Table 4]

[0046]

As described above, the present invention relates to a high-sensitivity electrophotographic photosensitive member using TiOPc or τ-type metal-free phthalocyanine as a charge-generating material, and a perylene-electrolyte between an aluminum support and a charge-generating layer. 3,4,9,10
By providing an intermediate layer formed by dispersing a tetracarboxylic acid-bis (phenethylimide) pigment in a binder resin, it is possible to provide an electrophotographic photoreceptor having high charge retention ability by controlling hole injection from a support. . Further, it is possible to suppress an increase in the residual potential due to an environmental change. This effect is particularly apparent at 20 to 70 parts by weight of the pigment in the binder resin of the intermediate layer when TiOPc is contained in the charge generating material, and becomes remarkable at 45 to 60 parts by weight. Also,
The effect is that when the τ-type metal-free phthalocyanine is contained in the charge generation material, the pigment is contained in the binder resin in an amount of 0.1 to 0.1%.
Appears particularly at 3 equivalents and becomes significant at 0.5 to 2 equivalents.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view of an electrophotographic photosensitive member manufactured according to the present invention.

FIG. 2 is a characteristic diagram showing an infrared absorption spectrum of oxotitanium phthalocyanine used in Examples.

[Explanation of symbols]

 Reference Signs List 10 aluminum support 11 intermediate layer 12 charge generation layer 13 charge transport layer

Claims (5)

[Claims] 1. An electrophotographic photoreceptor having an intermediate layer between a substrate and a photosensitive layer, wherein oxotitanium phthalocyanine is used as a charge generating material, and the intermediate layer is made of perylene.
An electrophotographic photoreceptor using a 3,4,9,10-tetracarboxylic acid-bis (phenethylimide) pigment. 2. The electron according to claim 1, wherein the photosensitive layer has a charge generation layer using oxotitanium phthalocyanine and a charge transport layer using a hole transport material, and is negatively charged. Photoreceptor. 3. The intermediate layer comprises the perylene-3,4,4.
3. The electrophotographic photoreceptor according to claim 2, wherein 9,10-tetracarboxylic acid-bis (phenethylimide) pigment is formed by dispersing in a binder resin at a ratio of 20 to 70 parts by weight. 4. The photosensitive layer has a charge generation layer using a τ-type metal-free phthalocyanine and a charge transport layer using a hole transport material, and is negatively charged. Electrophotographic photoreceptor. 5. The intermediate layer according to claim 1, wherein the perylene-3,4,9,10-tetracarboxylic acid-bis (phenethylimide) pigment is dispersed in the binder resin at a ratio of 0.1 to 3 equivalents to the resin. 5. The electrophotographic photoreceptor according to claim 4, wherein the electrophotographic photoreceptor is formed.