JPH01257963A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain an electrophotographic sensitive body good in chargeability, rapid in potential decay due to exposure to light, high in sensitivity, and further small in dependence of potential decay on an electric field by combining an electric charge generating layer containing a specified bisazo pigment with a charge transfer layer containing a benzidine derivative. CONSTITUTION:The charge generating layer contains one of the bisazo pigments represented by formula I and the charge transfer layer contains one of the benzidine derivatives represented by formula II and embodied by formula III. In formulae I and II, X is optionally substituted aralkyl, aryl, or a heterocyclic group; R1 is alkyl or alkoxy; one of R2 and R3 is >=2C alkyl and the other is H, alkyl, alkoxy, or substituted amino, thus permitting the obtained electrophotographic sensitive body to be freed of trailing of potential and almost freed of residual potential.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an electrophotographic photoreceptor having a layer structure in which a charge generation layer and a charge transport layer are functionally separated.

Conventional technology Conventional electrophotographic photoreceptors include those with a single-layer photoconductive layer and those with a multilayer photoconductive layer, but in recent years, in particular, organic photoconductive materials have been bonded with resin etc. as a photoconductive layer, and a charge transport layer has been developed. Various proposals have been made regarding an organic electrophotographic photoreceptor having a layer structure in which a charge generation layer and a charge generation layer are functionally separated, and various charge generation materials and charge transport materials have also been proposed. For example, known charge generating materials include polycyclic quinone pigments, perylene pigments, indigo pigments, bisbenzimidazole pigments, quinacridone pigments, phthalocyanine pigments, monoazo pigments, bisazo pigments, trisazo or polyazo pigments, and charge transporting materials. Examples include amine compounds, hydrazone compounds, pyrazoline compounds, oxazole compounds, oxadiazole compounds, stilbene compounds,
Carbazole compounds and the like are known. Various proposals have also been made to use these charge-generating materials and charge-transporting materials in combination. (For combinations with disazo pigments, see, for example, JP-A-60-163048, JP-A-60-163048;
-146250, 61-107250, 61-
(No. 69072, No. 61-48864, etc.) Problems to be Solved by the Invention By the way, it is possible to obtain satisfactory electrophotographic characteristics in a laminated electrophotographic photoreceptor in which a charge generation layer and a charge transport layer are functionally separated. In order to achieve this, it is necessary to satisfy the following conditions: 1. Charges are efficiently generated in response to the light absorbed by the charge-generating material, and 2. The generated charges are efficiently injected into the charge transport material and transported. It is said that That is, 1
Even if condition 1 is satisfied, if condition 2 is not satisfied, satisfactory photoresponsiveness cannot be obtained.

In addition, when the electrophotographic photoreceptor is one in which a charge generation layer and a charge transport layer are laminated in this order, and light irradiation is performed from the charge transport layer side, the following conditions must be met in order to obtain high sensitivity:
It is necessary that the charge transport layer be sufficiently transparent to the light that activates the charge generation layer.

In order to create an electrophotographic photoreceptor using a charge-generating material and a charge-transporting material, the above-mentioned conditions must be met, including sensitivity, acceptance potential, potential retention, potential stability, residual potential, and spectroscopy. Electrophotographic properties such as properties, strength, durability,
A material must be selected that satisfies all aspects, including usage characteristics such as stain resistance, and manufacturing stability and quality stability when manufactured by coating. However, it is extremely difficult to select a combination of materials that satisfies all of these points. I haven't found anything satisfying.

The present invention was made in view of the above circumstances, and by finding a combination of materials that satisfies all of the requirements for an electrophotographic photoreceptor.
The purpose is to provide an excellent electrophotographic photoreceptor.

Means and Action for Solving the Problems The above-mentioned nine objects of the present invention are as follows: ) [wherein A is the formula (wherein X represents a substituted or unsubstituted aralkyl group, aryl group, or heterocyclic group]] A bisazo pigment represented by the following formula is used as the charge transport material of the charge transport layer: Throwing coins (I
I> R3R3 (wherein R1 represents an alkyl group or an alkoxy group,
R2 and R3°, one of which represents an alkyl group having 2 or more carbon atoms, and the other represents a hydrogen atom, an alkyl group, an alkoxy group, or a substituted amino group) can do.

That is, the electrophotographic photoreceptor of the present invention is one in which a photosensitive layer consisting of a charge generation layer and a charge transport layer is provided on a conductive substrate, and the charge generation layer is necessarily represented by the above-mentioned -I>. The charge transport layer contains a bisazo pigment, and the charge transport layer is a bisazo pigment.
) It is characterized by containing a benzidine compound represented by:

The present invention will be explained in detail below.

In the present invention, the bisazo pigment contained in the charge generation layer is represented by the above-mentioned -Isen (I>), and specifically, the following compounds may be mentioned.

E F
)-CI
C1 knee 19! -24 Knee 41 In the present invention, the particle size of these bisazo pigments is 2#1
It is preferable that it is below.

Binder resins for dispersing bisazo pigments include well-known hazes, such as polycarbonates, polyarylates, polystyrenes, polyesters, polyvinyl butyrals, methacrylic acid ester polymers or copolymers, vinyl acetate polymers or copolymers, cellulose esters. Alternatively, ether, polybutadiene, polyurethane, epoxy resin, etc. are used.

On the other hand, as the charge transport material in the charge transport layer, benzidine compounds represented by the above-mentioned -Isen (II) are used, and among these, those represented by -Isen (1) are preferred.

<In the formula, one of R2 and R3 has 2 carbon atoms.
The above-mentioned alkyl group is shown, and the other is a hydrogen atom, an alkyl group, an alkoxy group, or a substituted amino group) Among these, particularly preferable ones are shown in the following structural formula (IV).
and (V).

The compound represented by the above-mentioned (I[[)] has extremely high solubility in solvents, for example, high solubility in toluene, chlorobenzene, 1.1.2-trichloroethane, tetrahydrofuran, 1,4-dioxane, cyclohexanone, etc. has.

For example, the solubility of the compounds represented by the structural formulas (IV) t3 and (V) in toluene and chlorobenzene is as shown in Table 1 below, and the compounds have higher solubility than other compounds.

Table 1 The compounds have very high solubility in solvents and are therefore useful in forming layers by dip coating. That is, the amount of solvent used can be reduced, and the viscosity of the solution can be increased, making it possible to make the charge transport layer thicker, and also slowing down the rate at which the object to be coated is pulled up during dip coating. However, the predetermined film thickness of 1111 can be obtained, and on the other hand, because the pulling speed can be slowed down, uneven parts of the film thickness at the ends of the object to be coated in the pulling direction (parts where the coating liquid drips) can be obtained.
There is an advantage that the electrophotographic photoreceptor can be used for a longer period of time.

Specific examples of these benzidine compounds include the following.

Since these compounds do not have film-forming properties by themselves, they are used in combination with resins that have good film-forming properties. Examples of resins that can be used include polycarbonate, polyacrylate, polyester, polyarylate, polystyrene,
Styrene-acrylonitrile copolymer, polysulfone,
Examples include polymethacrylate ester, styrene-methacrylate copolymer, and the like. Among these, polycarbonate is preferred.

To explain in more detail the method for producing the electrophotographic photoreceptor of the present invention, first, the charge generation layer is formed by dispersing a bisazo pigment in a binder resin solution and coating the solution. As the dispersing means, commonly used ones such as a ball mill, roll mill, sand mill, attritor, etc. can be used. The blending ratio of bisazo pigment and binder resin is 40:1
-1:4, preferably 20:1-1:2. If the ratio of bisazo pigment is too high, the stability of the coating solution will decrease, and if it is too low, the sensitivity will decrease, so
It is desirable to keep it within the above range. Further, as the solvent for the binder resin, any solvent can be used as long as it is soluble, but it is desirable to select a solvent that has good pigment dispersibility. Further, a plurality of solvents may be used in combination.

The charge transport layer is formed by dissolving a benzidine compound represented by (II) and a film-forming resin in a solvent that dissolves both, and applying the solution.

The mixing ratio of the former and the latter is 5:1 to 1:5, preferably 3:1 to 1:3. If the former ratio is too high, the mechanical strength of the charge transport layer will decrease, and if it is too low, the sensitivity will decrease, so it is desirable to keep it within the above range.

In the electrophotographic photoreceptor of the present invention, the layer structure of the photosensitive layer formed on the conductive substrate may include a charge transport layer provided on the charge generation layer, or a charge transport layer provided on the charge transport layer. A generation layer may also be provided. The thickness of the charge generation layer is 0.05 to 511! ! i, the thickness of the charge transport layer is 5
In addition, in the electrophotographic photoreceptor of the present invention, it is preferable to provide a charge injection blocking layer between the photosensitive layer and the conductive substrate.

Example Next, the present invention will be explained with reference to Examples and Comparative Examples.

Example 1 1 part by weight of polyvinyl butyral resin (trade name: BLX, manufactured by Miki Kagaku Co., Ltd.) was dissolved in 40 parts by weight of cyclohexanone, and 3 parts by weight of Exemplified Compound I-4 was added thereto as a charge generating material. Then, the mixture was well dispersed using a paint shaker, and the resulting dispersion was applied onto an aluminum sheet using an applicator and dried to form a charge generating layer. The dry film thickness was 0.2JIJr1.

Next, on this charge generation layer, 31 parts by weight of the exemplified compound (1), which is a charge transport material, and a polycarbonate resin (trade name: NILEXAN 145, manufactured by GE Corporation, molecular weight: 35,000~
40,000) Apply a homogeneous solution consisting of 1 part by weight and 15 parts by weight of dichloromethane with an applicator,
It was dried to form a charge transport layer. The dry film thickness is 2 (1
It was 171.

The electrophotographic photoreceptor sheet thus prepared was tested using an electrostatic copying paper tester (5P-428, manufactured by Kawaguchi Electric Seisakusho ■).
The characteristics were evaluated as follows.

First, after negatively charging by -6KV corona discharge, 2
The surface potential VpO (VOIt
), then irradiate the surface with light using a tungsten lamp so that the illumination intensity is 5 lux, find the time until the surface potential reaches ■pO 172, and calculate the exposure amount E.
1/2 (lux-sec) was calculated. Vpo=-1
050V, E1/2=2.21ux-sec.

Examples 2 to 8 Electrophotographic photoreceptors were prepared in the same manner as in Example 1, except that the charge-generating materials and charge-transporting materials in Example 1 were replaced by those shown in Table 2. It was evaluated as follows. The results are shown in Table 2.

Table 2 Comparative Example 1 An electrophotographic photoreceptor was prepared in the same manner as in Example 2, except that a compound represented by the following structural formula was used as the charge transport material, and evaluation was performed in the same manner. .

Comparative Example 2 An electrophotographic photoreceptor was prepared in the same manner as in Example 4, except that a compound represented by the following structural formula was used as the charge transport material, and evaluated in the same manner.

Comparative Example 3 An electrophotographic photoreceptor was prepared in the same manner as in Example 7, except that a compound represented by the following structural formula was used as the charge transport material, and evaluated in the same manner.

Comparative Example 4 An electrophotographic photoreceptor was prepared in the same manner as in Example 8, except that a compound represented by the following structural formula was used as the charge transport material, and evaluated in the same manner.

The results are shown in Table 3.

Table 3 Effects of the Invention In the present invention, by combining the charge generation layer containing the above-mentioned bisazo pigment and the charge transport layer containing the above-mentioned benzidine compound, the charging property is good and the potential decay due to light irradiation is fast. Therefore, an electrophotographic photoreceptor can be obtained which has high sensitivity, has little electric field dependence of potential attenuation, and is easily attenuated by light even at a relatively low potential, that is, has no tailing of the potential and almost no residual potential. Further, the electrophotographic photoreceptor of the present invention includes:
It has the characteristics of good potential stability, low temperature and humidity dependence, extremely low optical fatigue, no deterioration in chargeability due to light, and no so-called optical memory effect, making it very easy to use.

The electrophotographic photoreceptor of the present invention is effectively used in electrophotographic copying machines, but can also be applied to various printers, microfilm readers, electrophotographic engraving systems, etc. that apply xerography technology.

Patent applicant Fuji Xerox Co., Ltd. Agent
Patent Attorney Tsuyoshi Okibe

Claims (2)

[Claims] (1) In a laminated electrophotographic photoreceptor in which a photosensitive layer consisting of a charge generation layer and a charge transport layer is provided on a conductive substrate, the charge generation layer has the following general formula (I) ▲ Numerical formula, chemical formula, table, etc. ▼(I) [Where A is a formula ▲There are mathematical formulas, chemical formulas, tables, etc.▼ or ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (However, X is a substituted or unsubstituted aralkyl group, aryl group, or heterocycle The charge transport layer contains a bisazo pigment represented by the following general formula (II) ▲ Numerical formula, chemical formula, table, etc. ▼ (II) (In the formula, R_1 represents an alkyl group or an alkoxy group. , R_2 and R_3, one of which represents an alkyl group having 2 or more carbon atoms, and the other represents a hydrogen atom, an alkyl group, an alkoxy group, or a substituted amino group. Electrophotographic photoreceptor. (2) The electrophotographic photoreceptor according to claim 1, wherein the benzidine compound is represented by the following general formula (III). ▲There are mathematical formulas, chemical formulas, tables, etc.▼(III) (In the formula, one of R_2 and R_3 represents an alkyl group having 2 or more carbon atoms, and the other represents a hydrogen atom, an alkyl group, an alkoxy group, or a substituted amino group. (indicates the group)