JPH0253068A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To improve spectral sensitivity and various other characteristics by providing a photosensitive layer contg. a specific anthoanthrone pigment and bisazo compd. onto a conductive base. CONSTITUTION:The photosensitive layer contg. the anthoanthrone pigment expressed by formula I and the bisazo compd. expressed by formula II are provided. In formula I, X denotes a halogen atom, nitro group; cyano group, acyl group or carboxyl group; (n) denotes 0-4 integer. In formula II, Y denotes a hydrogen atom, halogen atom or nitro group; Z denotes a divalent arom. hydrocarbon group or divalent heterocyclic group contg. a nitrogen atom in the ring. The excellent spectral sensitivity is obtd. by the synergistic effect of the anthoanthrone pigment having good red color reproducibility and the fluorenone bisazo compd. having blue color reproducibility. The higher sensitivity is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an electrophotographic photoreceptor having a photosensitive layer containing an anthrone pigment and a specific hisazo compound, and having improved spectral sensitivity and other characteristics.

BACKGROUND ART Traditionally, electrophotographic photosensitive materials include inorganic photoconductive substances such as amorphous selenium, selenium alloys, cadmium sulfide, and zinc oxide, and organic photoconductive substances such as polyvinylcarbazole and polyvinylcarbazole derivatives. Conductive materials are widely known.

Organic photoconductive materials have advantages over inorganic materials in terms of transparency, film-forming properties, flexibility, manufacturability, and the like. Among organic photoconductive substances, polycyclic quinone pigments such as anthanthrone pigments are good as materials that absorb light and generate electric charges, and have already been reported in Japanese Patent Application Laid-Open No. 82-24295 (No. The characteristics of these polycyclic quinone pigments are that they absorb a large amount of light, can generate and emit charges with high efficiency, have high chemical stability, and are resistant to deterioration due to heat, light, etc. The pigments are difficult to coat, have good pigment dispersibility, and have good stability as paints.

On the other hand, as another example of a material with good properties,
Examples include fluorenone-based bisazo compounds described in No. 182695.

Problems to be Solved by the Invention Among the conventionally proposed pigments mentioned above, anthanthrone pigments absorb relatively short wavelength light well and do not absorb long wavelength light. In the past, when the original to be copied was a red original, the reproduction was good, but when the original was a blue original, the development density was low. On the other hand, fluorenone-based bisazo compounds absorb light with relatively long wavelengths well and absorb little light with steep wavelengths. Therefore, blue originals are well reproduced, but
For red originals, the development density is low.

Figure 2 illustrates the above phenomenon and shows an electrophotographic photoreceptor formed using standard materials, 3 using an anthrone pigment and 4 using a fluorenone-based bisazo compound. It indicates spectral sensitivity. When an anthrone pigment is used, the sensitivity to blue light (450 to 500 nm light) is high, so in the case of a blue original, potential attenuation is large and development is difficult. In the case of a fluorenone-based bisazo compound, it has high sensitivity to red (600 to 700 nm light), so in the case of a red original, potential attenuation is large and development is difficult.

It is an object of the present invention to provide an electrophotographic photoreceptor that improves the respective drawbacks of both of the above and further improves sensitivity to white light.

Means for Solving the Problems The electrophotographic photoreceptor of the present invention comprises an anthrone pigment represented by the following general formula (I) (hereinafter referred to as component A) and the following general formula (n) on a conductive support. It is characterized by having a photosensitive layer containing a bisazo compound (hereinafter referred to as component B) represented by:

(In the formula, X represents a halogen atom, a nitro group, a cyano group, an acyl group, or a carboxyl group, and n represents a number of O to 4) (In the formula, Y represents a hydrogen atom, a halogen atom, or a nitro group, (Z represents a 21dIi aromatic hydrocarbon group or a divalent heterocyclic group containing a nitrogen atom in the ring) In the electrophotographic photoreceptor of the present invention, the photosensitive layer is functionally separated into a charge generation layer and a charge transport layer. It may have a laminated structure. In that case, the charge generation layer contains component A and component B as charge generation materials,
It is preferable that the charge transport layer contains a benzidine compound represented by the following general formula (III) (hereinafter referred to as component C) as a charge transport material.

(In the formula, R1 represents a hydrogen atom, an alkyl group, or an alkoxy group, and R2 and R3 each represent a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, an alkoxycarbonyl group, or a substituted amino group) The layer structure of the photographic photoreceptor will be explained with reference to the drawings. FIG. 3 is a schematic cross-sectional view of an electrophotographic photoreceptor having a photosensitive layer with a single layer structure, in which component A and component B are dispersed in a binder resin containing a charge transport layer on a substrate 6. A photosensitive layer 5 is provided. FIG. 4 is a schematic cross-sectional view of an electrophotographic photoreceptor having a laminated photosensitive layer, in which a charge generation layer 7 and a charge transport layer 8 are provided on a base 6 in a laminated manner. The charge generation layer and the charge transport layer are the fourth
As shown in FIGS. (a) and (b), they may be provided in any order.

In the electrophotographic photoreceptor of the present invention, the photosensitive layer formed on the substrate contains component A and component B as charge generating materials. As component B, for example, the following can be used.

Binder resins for dispersing component A and component B include well-known binder resins, such as polycarbonate, polystyrene, polyvinyl butyral, methacrylic acid ester polymers or copolymers, vinyl acetate polymers or copolymers, cellulose esters or ethers. , polybutadiene, polyurethane,
Epoxy resin or the like is used.

In the present invention, component A has an average particle size of 0.3 to 0.8 pm,
Component B is preferably used with an average particle size of about 0.1 to 0.2 μm. When particles with such particle sizes are mixed and used, component B will enter the gaps between component A, which will increase the packing density of the film and increase the absorbance per unit film thickness. . This means that when these components are used in the charge generation layer, the film thickness can be made thinner, improving light attenuation characteristics, improving cycle characteristics, reducing optical memory, and reducing residual potential. It is defined as something that brings about effects such as reduction. In the present invention, component A and component B have the same dispersibility, stability, coatability, etc. in the same binder resin and the same solvent, so they have the advantage that they can be used in combination. I also need it.

Component A and component B may be mixed using any of the following methods: mixing their powders and then dispersing them, or dispersing each of them and then mixing a dispersion liquid.

The mixing ratio of component A and component B is preferably in the range of about 10:1 to 1:3, although it depends on the priority of color rectification.

Also, the ratio of the sum of component A and component B to the binder resin [yo, 2
The ratio is set to about 0:1 to 1:2.

When applying component A and component B to a functionally separated photosensitive layer,
A charge transport material is also used. When the photosensitive layer has a single layer structure, the charge transport material is contained in the binder resin together with components A and B. When the photosensitive layer has a laminated structure, the charge transport material is contained in the charge transport layer.

As the charge transport material, known ones such as amine compounds, hydrazone compounds, pyrazoline compounds, oxazole compounds, oxadiazole compounds, stilbene compounds, carbazole compounds, etc. are used. Among them, it is preferable to use the above-mentioned component C.

Component C has a large charge transport ability and low electric field dependence, so when combined with a mixture of components A and B, an electrophotographic photoreceptor with high sensitivity, low residual potential, and good potential decay characteristics can be obtained. .

Component C does not have film-forming properties by itself, so when forming a charge transport layer, it is used in combination with a resin that has good film-forming properties. Examples of resins that can be used include polycarbonate, polystyrene, polyester, polystyrene, styrene-acrylonitrile copolymer, polysulfone, polymethacrylate, and styrene-methacrylate copolymer, with polycarbonate being particularly preferred.

When the electrophotographic photoreceptor of the present invention has a laminated structure, the thickness of the charge generation layer is preferably set to about 0.05 to 5 μm, and the thickness of the charge transport layer is preferably set to about 5 to 50 μm.

Further, in the electrophotographic photoreceptor of the present invention, a barrier layer may be formed between the photosensitive layer and the substrate.

The barrier layer is effective in preventing unnecessary charge injection from the substrate, and can increase the chargeability of the photosensitive layer. Furthermore, it is also possible to improve the adhesion between the photosensitive layer and the substrate. Materials constituting the barrier layer include polyvinyl alcohol, polyvinylpyrrolidone, polyvinylpyridine,
Examples include cellulose ethers, cellulose esters, polyamides, polyurethanes, and casein. Among these, polyamides (especially copolymerized nylon, type 8 nylon, etc.) are preferably used. The thickness of the barrier layer is 0.0
The thickness is set to about 5 to 2 μm.

Function: Since the electrophotographic photoreceptor of the present invention has the above configuration,
An anthrone pigment with good red reproducibility and a fluorenone bis7zo compound with good blue reproducibility act synergistically to provide excellent spectral sensitivity. FIG. 1 explains this phenomenon.

Curves 1 and 2 in FIG. 1 show cases where the mixing ratios are different, and in either case, the sensitivity wavelength range of the electrophotographic photoreceptor is expanded.

This is necessary because when the electrophotographic photoreceptor of the present invention is irradiated with white light, the sensitivity wavelength range is wide, resulting in high sensitivity overall. Furthermore, when a halogen lamp with a large amount of long wavelength components is used as a light source, if the electrophotographic photoreceptor has high long wavelength sensitivity, the sensitivity will also be relatively high.

In that case, if you want to emphasize the red reproducibility of the electrophotographic photoreceptor, increase the amount of the anthanthrone pigment (hereinafter referred to as component A) represented by the general formula (I>), and if you want to emphasize the blue reproducibility, , the color reproducibility of the electrophotographic photoreceptor can be adjusted as desired by increasing the amount of the bisazo compound represented by the general formula (n) (hereinafter referred to as component B). Higher sensitivity and better brown color reproducibility than when used alone.

In the present invention, one of the advantages of mixing component B with component A is that in addition to improving blue reproducibility, the relative sensitivity to a halogen lamp is necessarily improved as described above.

One of the advantages of mixing component A with component B is that red color reproducibility must be improved.

Conventionally, when using only component B, it was necessary to put a cyan filter on the halogen lamp and weaken the red light due to the lack of red reproducibility, but by mixing component B with the other components. Using this method eliminates the need for a cyan filter, which has the advantage of reducing costs. In addition, component B has low electron mobility within the compound, and when applied to the charge generation layer of a functionally separated photosensitive layer and used with negative charge, it rarely has the disadvantage of low sensitivity in a low electric field. By mixing these, this drawback is also improved and the optical attenuation characteristics are improved. This is thought to be because component A has relatively high electron mobility, so when used in a negatively charged state, it has the advantage of high sensitivity even in a low electric field, linear potential decay, and low residual potential.

EXAMPLES Hereinafter, the present invention will be explained with reference to Examples and Comparative Examples. Note that "part" means part by weight.

Examples 1 to 2 and Comparative Examples 1 to 2 As component A, dibromanthanthrone having the general formula (I>, where X represents B, r, and n represents 2) was used, and as component B, exemplified compound No. 1 was used. Using.

1 part of polyvinyl butyral resin (trade name BXL, manufactured by Sekisui Chemical ■) was dissolved in 20 parts of cyclohexanone, divided into two parts, and component A and component B were added separately and dispersed using a sand mill apparatus. The average particle size of component A is in the range of 0.3 to 0.5 μm, and the average particle size of component B is in the range of 0.1 to 0.
．． A material in the range of 3 μm was used.

The resulting dispersion containing component A and the dispersion containing component B were mixed at the blending ratio shown in Table 1. In the comparative example,
Components and Component B were added individually.

Table 1 The obtained dispersion liquid was diluted appropriately to prepare a coating liquid.

On the other hand, a methanol/butanol mixed solution of nylon 8 resin (trade name Niratsukamite, manufactured by Dainippon Ink F1M) was applied to an 84#φX310m aluminum pipe.
A barrier layer of 0.8 μm was formed, and the above coating solution was coated on it using a ring coater, and heated at 100°C.
The charge generating layer was dried by heating for 10 minutes to form a charge generating layer having the thickness shown in Table 1.

A charge transport layer was formed on the formed charge generation layer.

That is, N,N'-diphenyl-N.

N'-bis(3-methylphenyl)M, 1'biphenyl]-4,4'-diamine (R1, R in the general formula (In>)
4 parts (2=hydrogen atom, R3-methyl group) as a charge transport material were dissolved in 40 parts of monochlorobenzene together with 6 parts of polycarbonate Z resin, and the resulting solution was coated with a dip coater at a bow rate of 11 cm/min. Coated. 11
It was dried at 0'C for 1 hour to form a charge transport layer with a thickness of 20 μs, thereby obtaining an electrophotographic photoreceptor.

Each of the obtained electrophotographic photoreceptors was installed in a copying machine (product name: FX2700, manufactured by Fuji Xerox 01),
First, we checked the potential. That is, the surface potential of a white original, then the surface potential of a red original with a constant density, and a blue original with a constant density were measured.

The results are shown in Table 2.

Table 2 As is clear from Table 2, in the case of Examples 1 and 2,
The surface potential is high for both the red and blue originals, but in Comparative Example 1, the blue original has a relatively low surface potential, and in Comparative Example 2, the red original has a relatively low surface potential. Ta.

Next, originals with various color schemes were prepared, and the color recirculation properties of the copied images were examined. In the case of Examples 1 and 2, red,
The blue color was also reproduced relatively well, whereas Comparative Example 1
In the case of , the blue color was pale, and in the case of Comparative Example 2, the red color was relatively pale.

On the other hand, in the case of a white original, each side had the same potential and the sensitivity was the same. However, as shown in Table 1, the thickness of the charge generation layer is different on each side, and is thinner in Examples 1 and 2 than in Comparative Examples 1 and 2.
Therefore, the amount of expensive charge-generating material used can be reduced, contributing to cost reduction of electrophotographic photoreceptors.

Next, these electrophotographic photoreceptors were used repeatedly i, ooo times, and immediately after that, the surface potential was measured. The results are shown in Table 3.

As is clear from Table 3, in the case of Comparative Example 2, there was a tendency for the sensitivity to decrease with repeated use. This is considered to contribute to the electron mobility within the compound of component B.

Examples 3 to 4 Electrophotographic photoreceptors were produced and evaluated in the same manner as in Example 1, except that the charge transport material was changed to the following compound.

The results for the charge transport material of Example 4 are shown in Table 4. Example 1 in any case
Compared to cases 2 and 2, the potential for white originals is slightly higher;
The sensitivity was slightly inferior.

Table 4 Table 5 Examples 5-7 Exemplary compound N was used as component B in Example 1.

In place of Example 1, an electrophotographic photoreceptor (Example 5) using exemplified compound NQ15 and an electrophotographic photoreceptor (Example 6) using exemplified compound Nα17 were prepared. Further, an electrophotographic photoreceptor (Example 7) was prepared by replacing the charge transporting material in Example 1 with a compound represented by the following structural formula. The results are shown in Table 5.

Effects of the Invention As is clear from the comparison of the above examples, the electrophotographic photoreceptor of the present invention has the above structure, and therefore contains an anthrone pigment with good red reproducibility and a fluorenone pigment with good blue recyclability. Both bisazo compounds act synergistically and have excellent spectral sensitivity. Furthermore, even when a halogen lamp with many long wavelength components is used as a light source, the sensitivity is relatively high.

Further, in the electrophotographic photoreceptor of the present invention, there is an advantage that the thickness of the charge generation layer can be made thinner than when component A and component B are used alone.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the spectral sensitivity of the electrophotographic photoreceptor of the present invention, FIG. 2 is a graph showing the spectral sensitivity of the conventional electrophotographic photoreceptor, and FIGS. 3 and 4 are graphs showing the spectral sensitivity of the electrophotographic photoreceptor of the present invention, respectively. This is a schematic cross-sectional view of an electrophotographic photoreceptor. 5... Photosensitive layer, 6... Substrate, 7... Charge generation layer,
8... Charge transport layer. Patent applicant Fuji Xerox Co., Ltd. Agent
Patent Attorney Seibu Tsuyoshi 5... Photosensitive layer 6... Basic 7... Charge generation layer 8... Charge transport layer Figure 3 (a) (b) Figure 4

Claims (1)

[Claims] (1) An electrophotographic photoreceptor characterized by having, on a conductive support, a photosensitive layer containing an anthrone pigment represented by the following general formula (I) and a bisazo compound represented by the following general formula (II) . ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) (In the formula, X represents a halogen atom, nitro group, cyano group, acyl group, or carboxyl group, and n represents a number from 0 to 4) ▲Mathematical formulas, chemical formulas , tables, etc.▼(II) (In the formula, Y represents a hydrogen atom, a halogen atom, or a nitro group, and Z represents a divalent aromatic hydrocarbon group or a divalent heterocyclic group containing a nitrogen atom in the ring. (2) the photosensitive layer has a laminated structure in which a charge generation layer and a charge transport layer are functionally separated;
The charge generation layer contains an anthrone pigment represented by the above general formula (I) and the bisazo compound represented by the above general formula (II) as charge generation materials, and the charge transport layer contains a benzidine-based charge transport layer represented by the following general formula (III). The electrophotographic photoreceptor according to claim 1, characterized in that it contains a compound as a charge transport material. ▲There are mathematical formulas, chemical formulas, tables, etc.▼(III) (In the formula, R_1 represents a hydrogen atom, an alkyl group, or an alkoxy group, and R_2 and R_3 each represent a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, or an alkoxycarbonyl group or substituted amino group)