JPH01257950A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain an electrophotographic sensitive body almost freed of residual potential by combining an electric charge generating layer containing a specified bisazo pigment with a charge transfer layer containing a benzidine derivative. CONSTITUTION:The electrophotographic sensitive body comprises the charge generating layer containing one of the bisazo pigments represented by formula I and the charge transfer layer containing one of the benzidine derivatives represented by formula II, and in formulae I and II, each of R1-R8 is H or the like; a is an aromatic coupler component; R9 is alkyl or the like; one of R10 and R11 is >=2C alkyl and the other is H or the like. This benzidine compound is embodied by formula III, thus permitting the electrophotographic sensitive body to be superior is chargeability, rapid in decay of potential due to exposure to light, high in sensitivity, small in dependence of the potential decay on the electric field, easy to cause potential decay due to exposure to light, even when comparatively low in potential, small in 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 particular, in recent years, 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 example, Japanese Unexamined Patent Application Publication No. 55-7
No. 3057, 58-7642@, 59-19948
No. 59-214035, No. 60-3634,
61-132955 @, 61-134354 @ Publication) Problems to be Solved by the Invention By the way, it is desirable to have satisfactory electrophotographic properties in a laminated electrophotographic photoreceptor in which a charge generation layer and a charge transport layer are functionally separated. In order to obtain this, the following conditions must be met: 1. The charge generation material must efficiently generate charges in response to the absorbed light, and 2. The generated charges must be efficiently injected into the charge transport material and transported. is required. 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, and conventionally proposed combinations of charge-generating materials and charge-transporting materials do not fully satisfy the above conditions. I haven't found anything satisfying.

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

Means and Effects for Solving the Problems The above-mentioned object of the present invention is to provide a charge generation material of a charge generation layer with the following general formula (I> (wherein R1, R2, R3 and R4 are each a hydrogen atom, represents a halogen atom, an alkyl group, an alkoxy group, or a cyano group, and R5, R6, R7, and R8 each represent a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group,
A bisazo pigment represented by the formula (representing a cyano group or a methylthio group, and A represents an aromatic coupler component) is used as the charge transporting material of the charge transporting layer, and the following general formula (n) 11 is used.
R11 (wherein R9 represents an alkyl group or an alkoxy group,
One of R10 and R11 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 amine group. be able to.

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 a bisazo compound represented by the general formula (I). containing a pigment, and the charge transport layer is represented by the general formula (II).
It is characterized by containing a benzidine compound represented by:

The present invention will be explained in detail below.

In the present invention, the bis7zo pigment contained in the charge generation layer is represented by the above general formula (I>, but specifically, A is represented by the following general formula (1), (2) or (3). The groups shown can be mentioned.

(1) ■
a (wherein Z represents an atomic group necessary to form a polynuclear aromatic ring or a heterocycle by condensing with a benzene ring, R12
and R13 each represent a hydrogen atom, a substituted or unsubstituted alkyl group, an aralkyl group, an aryl group, or a heterocyclic group, and R14 and R15 represent a substituted or unsubstituted alkyl group or aryl group) These bisazo pigments Specific examples include the following:

In the present invention, the particle size of these bisazo pigments is preferably 2s or less.

Binder resins for dispersing bisazo pigments include well-known ones, such as polycarbonate, polystyrene, polyester, polyarylate, polyvinyl butyral, methacrylic acid ester polymers or copolymers, vinyl acetate polymers or copolymers, cellulose esters or 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 general formula (n) are used, and among these, those represented by the general formula (II) are preferred.

11R11 (In the formula, one of RIO and R11 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.) Among these, particularly preferred are the following: Structural formula (IV>
and (V).

The compound represented by the above general formula (I[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) and (V) in toluene and chlorobenzene is as shown in Table 1 below, and the solubility is higher than that of other compounds.

It's 1 o'clock to the 1st table! As such, these compounds have very high solubility in solvents, making them 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, it is possible to obtain a coating film with a predetermined thickness, and on the other hand, it is possible to reduce the pulling speed, thereby reducing uneven parts of the film thickness (parts where the coating liquid drips) at the ends of the object to be coated in the pulling direction. Therefore, there is an advantage that the use of the electrophotographic photoreceptor can be extended.

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 polymethacrylic ester, styrene-methacrylic ester 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 to 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 the general formula (If>) and a film-forming resin in a solvent that dissolves both, and applying the solution.

The blending 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 O,OS~5, and the thickness of the charge transport layer is 5~50μ.
Further, 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 Tsukusui Kagaku Co., Ltd.) was dissolved in 40 parts by weight of cyclohexanone, and exemplified compound ■-1 was added therein as a charge generating material.
3 parts by weight of 4 were added thereto, and then well dispersed using a paint shaker. The resulting dispersion was applied onto an aluminum sheet using an applicator and dried to form a charge generating layer. The film thickness after drying was 0.24.

Next, on this charge generation layer, 31 parts of an exemplary compound which is a charge transporting material and a polycarbonate resin (trade name
Lexan 145, manufactured by GE, molecular weight: 35,000-4
A homogeneous solution consisting of 0,000>1 part by weight and 15 parts by weight of dichloromethane was applied using an applicator and dried to form a charge transport layer. Film thickness after drying is 20μs
Met.

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 applying a corona discharge of V to −6 to negatively charge it, 2
The surface potential VPO (volt
), 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 becomes 1/2 of vPO, and calculate the exposure amount E.
1/2 (lux-sec) was calculated. VPO=-11
1 at 00V, E 1/2=3.01ux-sec
7) Tsuta.

Examples 2 to 10 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 In Example 1, the following structural formula (V
An electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that the compound shown in 1) was used, and evaluation was performed in the same manner. The results are shown in Table 3.

Comparative Example 2 In Example 5, the above structural formula (V
An electrophotographic photoreceptor was prepared in the same manner as in Example 5, except that the compound represented by l> was used, and evaluation was performed in the same manner. The results are shown in Table 3. Comparative Example 3 In Example 6, the above structural formula (V
An electrophotographic photoreceptor was prepared in the same manner as in Example 6, except that the compound shown in 1) was used, and evaluation was performed 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 bis7zo pigment and the charge transport layer containing the above-mentioned benzidine-based compound, the chargeability is good, and when irradiated with light, It is possible to obtain an electrophotographic photoreceptor that exhibits fast potential decay and high sensitivity, and also has low dependence of potential decay on electric field and is easily photo-attenuated even at relatively low potentials, that is, there is no potential tailing and almost no residual potential. It will be done. 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 pyrography technology.

Claims (3)

[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) (In the formula, R_1, R_2, R_3 and R_4 each represent a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, or a cyano group, and
_8 each represents a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, a cyano group, or a methylthio group, and A
represents an aromatic coupler component), and the charge transport layer has the following general formula (II) ▲ Numerical formula, chemical formula, table, etc. ▼ (II) (In the formula, R_9 is an alkyl group or Represents an alkoxy group; one of R_1_0 and R_1_1 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) An electrophotographic photoreceptor characterized by: (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_1_0 and R_1_1 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 (indicates the group) (3) A in the general formula (I) above is represented by the following general formula (
The electrophotographic photoreceptor according to claim 1, which is a group represented by 1), (2) or (3). ▲There are mathematical formulas, chemical formulas, tables, etc.▼▲There are mathematical formulas, chemical formulas, tables, etc.▼▲There are mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, Z is fused with a benzene ring to form a polynuclear aromatic ring or a heterocyclic ring. R_1_2 and R_1_3 each represent a hydrogen atom, a substituted or unsubstituted alkyl group, an aralkyl group, an aryl group, or a heterocyclic group, and R_1_4 and R_1_5 represent a substituted or unsubstituted alkyl group. group or aryl group)