JPH01257955A - 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. In formulae I and II, X is H, halogen, or nitro; A is a divalent aromatic hydrocarbon group or such a heterocyclic group having N in the ring; each of R1 and R2 is H, alkyl, alkoxy, halogen, alkoxycarbonyl, or substituted amino, thus permitting the electrophotographic sensitive body to be superior in 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 photodecay, even when 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 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, lazoline 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, JP-A-54-22
834@, No. 56-94360, No. 57-20574
No. 2-205747, No. 57-204042-2040
No. 53, No. 57-197544-197551, No. 5
8-122544 to 122551, 61-67
No. 865, No. 61-124949, No. 61-
132953, 62-115452, etc.)
Problems to be Solved by the Invention In order to obtain satisfactory electrophotographic properties in a laminated electrophotographic photoreceptor in which a charge generation layer and a charge transport layer are functionally separated, 1. The charge generation material absorbs It is necessary to satisfy the following conditions: 2. The generated charge is efficiently injected into the charge transport material and transported. 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-mentioned circumstances, and by finding a combination of materials that satisfies all of the requirements for an electrophotographic photoreceptor, it is possible to create an excellent 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 the following charge-generating material for a charge-generating layer: A bisazo pigment represented by A represents a divalent aromatic hydrocarbon group or a divalent heterocyclic group containing a nitrogen atom in the ring is used as the charge transport material of the charge transport layer. > (wherein R1 and R2 each represent a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, an alkoxycarbonyl group, or a substituted amino group).

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

The present invention will be explained in detail below.

In the present invention, the bisazo pigment to be contained in the charge generation layer is shown in the above-mentioned formula (1), but specifically, compounds having the structural formula shown in the table below can be used.

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

Binder resins for dispersing bisazo pigments include well-known ones, such as polycarbonate, polystyrene, polyester, polyvinyl butyral, methacrylic acid ester polymers or copolymers, vinyl acetate polymers or copolymers,
Cellulose esters or ethers, polybutadiene, polyurethane, epoxy resins, etc. are used.

On the other hand, as the charge transporting material in the charge transporting layer, benzidine compounds represented by the above-mentioned formula (n) are used, and specific examples include compounds having the structural formulas shown in the table below.

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, polystyrene, styrene-acrylonitrile copolymer, polysulfone, polymethacrylate, and styrene-methacrylate copolymer. 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-based compound indicated by the symbol ([) 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 0.05 to 5μ, and the thickness of the charge transport layer is 5 to 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: B [x, manufactured by Tsukisui Kagaku Co., Ltd.) was dissolved in 40 parts by weight of cyclohexanone, and 3 parts by weight of Exemplary Compound I-1 as a charge generating material was dissolved therein. Parts by weight were added, followed by thorough dispersion 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 film thickness after drying was 0.2 μm.

Next, on this charge generation layer, 1 part by weight of Exemplary Compound I [-181, which is a charge transport material, and a polycarbonate resin (trade name Nilexane 145, manufactured by GE, molecular weight = 35.000) were applied.
~40,000> A homogeneous solution consisting of 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 20
It was μs.

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

First, after negatively charging by -6KV corona discharge, 2
Leave it in the dark for a second, and the surface potential VO (voIt) at that time
Then, using a tungsten lamp, irradiate the surface with light so that the illumination intensity is 5 lux, calculate the time until the surface potential reaches 175 of VO, and calculate the exposure 1fE1.
15 (lux-sec) was calculated. VO--985,
E 115 = 6.1 lux -sec.

Examples 2 to 6 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 1. They were evaluated in the same way. The results are shown in Table 1.

Table 1 Comparative Example 1 In Example 1, the following structural formula (I
An electrophotographic photoreceptor was prepared in the same manner as in Example 1 except that the compound represented by [I] was used, and evaluation was performed in the same manner.

C2I(5 Comparative Example 2 In Example 3, the above structural formula (I
An electrophotographic photoreceptor was prepared in the same manner as in Example 3, except that the compound represented by [I] was used, and evaluation was performed in the same manner.

These results are shown in Table 2.

Table 2 Effects of the Invention In the present invention, by combining the charge generation layer containing the above-mentioned bisazo pigment 7 and the charge transport layer containing the above-mentioned benzidine-based compound, the chargeability is good, and the potential decreases due to light irradiation. It is possible to obtain an electrophotographic photoreceptor that has high sensitivity and high sensitivity, and has little electric field dependence of potential attenuation, and is easily attenuated by light even at a relatively low potential, that is, has no potential trailing and almost no residual potential. In addition, the electrophotographic photoreceptor of the present invention has good potential stability, low temperature and humidity dependence, extremely little optical fatigue, and no deterioration in charging properties due to light, the so-called optical memory effect, making it very usable. It has the characteristic of being 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 Seibe

Claims (1)

[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, X represents a hydrogen atom, a halogen atom, or a nitro group, and A represents a divalent aromatic hydrocarbon group or a divalent heterocyclic group containing a nitrogen atom in the ring.) The charge transport layer contains the bisazo pigment shown below, and the charge transport layer has the following general formula (II) ▲ Numerical formula, chemical formula, table, etc. An electrophotographic photoreceptor comprising a benzidine compound represented by a halogen atom, an alkoxycarbonyl group, or a substituted amino group.