JPH0212257A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To enhance sensitivity and repetition characteristics by incorporating a specified azo compound in a photosensitive layer formed on a conductive substrate. CONSTITUTION:The photosensitive layer 2a contains at least one of the compound represented by formula I in which each of Ar1 and Ar2 is an optionally substituted aromatic hydrocarbon group or an aromatic heterocyclic group, and Cp is a coupler residue. The electrophotographic sensitive body is obtained by forming on the conductive substrate the photosensitive layer 2a containing the azo compound of formula I and an electric generating material dispersed into a binder resin, thus permitting sensitivity both in the case of positive and negative chargings and repetition characteristics to be all enhanced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electrophotographic photoreceptor, and more specifically, an azo compound represented by the general formula (I) is contained in a photosensitive layer formed on a conductive substrate. The present invention relates to an electrophotographic photoreceptor characterized by containing the following.

[Conventional technology]

Conventionally, photosensitive materials for electrophotographic photoreceptors (hereinafter also referred to as photoreceptors) include inorganic photoconductive substances such as selenium or selenium alloys, or inorganic photoconductive substances such as zinc oxide or cadmium sulfide in a resin binder. dispersion, organic photoconductive materials such as poly-N-vinylcarbazole or polyvinylanthracene, organic photoconductive materials such as phthalocyanine compounds or bisazo compounds, or dispersion of these organic photoconductive materials in a resin binder. Those that have been made are used.

In addition, a photoreceptor must have the function of retaining surface charge in the dark, the function of receiving light and generating charge, and the function of receiving light and transporting charge, all of which can be achieved in one layer. A so-called single-layer photoreceptor with the following functions is laminated with functionally separated layers: a layer that mainly contributes to charge generation, and a layer that contributes to surface charge retention in the dark and charge transport during light reception. There is a so-called laminated photoreceptor. For example, the Carlson method is applied to image formation by electrophotography using these photoreceptors. Image formation in this method involves charging the photoconductor in a dark place by corona discharge, forming electrostatic latent images such as letters and pictures on the document by exposing the surface of the charged photoconductor, and This is done by developing the latent image with toner, transferring the developed toner image to a support such as paper, and fixing it. After the toner image is transferred, the photoreceptor is charged, the residual toner is removed,
After photostatic charge removal, etc., it is reused.

In recent years, electrophotographic photoreceptors using organic materials have been put into practical use due to their advantages such as flexibility, thermal stability, and film-forming properties. For example, poly-N-vinylcarbazole and 2
．． 4.7-) dinitrofluoren-9-one (described in US Pat. No. 3,484,237),
Photoreceptor containing organic pigment as main component (Japanese Patent Application Laid-Open No. 47-3754
3), and a photoreceptor whose main component is a eutectic complex consisting of a dye and a resin (described in JP-A-47-10735). Furthermore, many new azo compounds and perylene compounds have been put into practical use.

[Problem to be solved by the invention]

As mentioned above, organic materials have many advantages that inorganic materials do not have, but at present, no material has yet been obtained that fully satisfies all the characteristics required of electrophotographic photoreceptors. In particular, there were problems with photosensitivity and characteristics during repeated and continuous use.

This invention was made in view of the above points, and
An object of the present invention is to provide an electrophotographic photoreceptor with high sensitivity and excellent repeatability by using a new organic material that has never been used as a charge generating substance in the photosensitive layer.

[Means to solve the problem]

In order to achieve the above object, the present invention provides an electrophotographic photoreceptor including a photosensitive layer containing at least one compound represented by the following general formula (H).

[In formula (I), Ar and Ar2 each represent any of the following optionally substituted aromatic hydrocarbon groups and aromatic heterocyclic groups, provided that at the same time, a substituted or unsubstituted phenylene group ), Cρ represents a coupler residue. ] Cρ( in the above general formula (I)
As the coupler residue, those having structures represented by the following general formulas (II) to (V) are suitable.

[In formulas (n) to (V), Z represents a residue that is condensed with a benzene ring to form a polycyclic aromatic ring or a heterozygote, xl is OR, or HN R2R-(R3゜R3 and R3 is a hydrogen atom, or each of the following optionally substituted alkyl or aryl groups.

represents any aromatic heterocyclic group), and X2
and X represent any of the following optionally substituted alkyl groups, aryl groups, and aromatic heterocyclic groups, and X3'J6 and X are hydrogen atoms.

Cyano group, carbamoyl group, carboxyl group, ester group, acyl2. (X represents a hydrogen atom, or any of the following optionally substituted alkyl groups, cycloalkyl groups, alkenyl groups, aryl groups, and aromatic heterocyclic groups) , X, and χB represent a hydrogen atom, a halogen atom, a nitro group, or each of the following optionally substituted alkyl groups and alkoxy groups; represents any one of the groups, and xl. represents either an optionally substituted aryl group or an aromatic heterocyclic group.] Azo compound of the general formula (I) used in this invention are the respective corresponding diazonium salts and couplers in a suitable organic solvent 9 such as N,N-dimethylformamide (
It can be synthesized by reacting with a base in DMF) to cause a coupling reaction.

Specific examples of the azo compound of the general formula (I) thus obtained are as follows.

1j [Function] There is no known example of using an azo compound represented by the above general formula (+) in a photosensitive layer. In order to achieve the above object, the present inventors conducted a number of experiments on these azo compounds while conducting intensive studies on various organic materials. It has been discovered that the use of a specific azo compound represented by the above general formula (+) as a charge-generating substance is effective in improving electrophotographic properties, and a photoreceptor with high sensitivity and excellent repeatability has been developed. I was able to obtain this.

〔Example〕

The photoreceptor of the present invention contains an azo compound represented by the general formula (I) in the photosensitive layer, and depending on how these azo compounds are applied, the photoreceptor may have a photoreceptor shown in FIG. 1, FIG. 2, or FIG. It can be used as shown in Figure 3.

FIGS. 1 to 3 are conceptual cross-sectional views of different embodiments of the photoreceptor of the present invention, where l is a conductive substrate, 2a, 2b,
2c is a photosensitive layer, 3 is a charge generating material, 4 is a charge generating layer, 5
6 is a charge transporting material, 6 is a charge transporting layer, and 7 is a coating layer.

FIG. 1 shows a photosensitive layer 2a (usually The structure is called a single-layer photoreceptor).

FIG. 2 shows a charge-generating layer 4 containing an azo compound represented by the general formula N) as a charge-generating substance 3 and a charge-transporting layer 6 mainly composed of a charge-transporting substance 5 on a conductive substrate 1. A photosensitive layer 2b (commonly referred to as a laminated type photoreceptor) consisting of a laminated layer is provided. A photoreceptor having this structure is normally used in a negative charging method. FIG. 3 shows a photosensitive layer 2c having a layer structure opposite to that in FIG. 2, and is normally used in a positive charging method. In this case, in order to protect the charge generation layer 4, a covering layer 7 is added.
It is common to provide

The reason why the laminated photoreceptor has two types of layer configurations is that even if a photoreceptor with the layer configuration shown in Figure 2 is used for positive charging, a compatible charge transport material has not yet been found. This is because there is no At present, when applying a positive charging method to a laminated type photoreceptor, it is necessary to use a photoreceptor having the layer structure shown in FIG.

The photoreceptor shown in FIG. 1 can be produced by dispersing a charge generating material in a solution containing a charge transporting material and a resin binder, and applying this dispersion onto a conductive substrate.

The photoreceptor shown in Figure 2 is produced by dispersing particles of the charge generating material π in a solvent or resin binder, applying a dispersion liquid on the conductive substrate, drying it, and then dissolving the charge transport material and the resin binder on top of the dispersion. It can be produced by applying a solution and drying it.

The photoreceptor shown in Figure 3 is a dispersion obtained by coating a solution containing a charge transporting substance and a resin binder on a conductive substrate and drying it, and then dispersing particles of a charge generating substance thereon in a solvent or a resin binder. It can be produced by applying a liquid, drying it, and further forming a covering layer 7.

The conductive substrate l functions as an electrode for the photoreceptor and at the same time serves as a support for the other layers, and may be cylindrical, plate-shaped, or film-shaped, and may be made of metal such as aluminum, stainless steel, or nickel. Alternatively, it may be made of glass, resin, or the like and subjected to conductive treatment.

The charge generation layer 4 is formed by applying a material in which particles of the charge generation substance 3 made of the azo compound represented by the general formula (I) are dispersed in a resin binder, and receives light to generate charges. Occur. In addition to the high charge generation efficiency, the ability to inject the generated charges into the charge transport layer 6 and the coating layer 7 is also important, and it is desirable that the charge is less dependent on the electric field and can be easily injected even in a low electric field. The charge generation layer is mainly composed of a charge generation substance, and a charge transport substance or the like may be added thereto. Resin binders include polycarbonate, polyester, and polyamide.

Polyurethane, epoxy, silicone resin, polymers and copolymers of methacrylic acid esters, etc. can be used in appropriate combinations.

The charge transport layer 6 is formed by coating a resin binder with a material in which a hydrazone compound, a pyrazoline compound, a styryl compound, a triphenylamine compound, an oxazole compound, an oxadiazole compound, etc. are dissolved and dispersed as an organic charge transport substance. In the dark, it functions as an insulating layer to hold the charge on the photoreceptor, and when receiving light, it functions to transport the charge injected from the charge generation layer. As a resin binder, polycarbonate, polyester, polyamide,
Polyurethane, epoxy, silicone resin.

Polymers and copolymers of methacrylic acid esters can be used.

The coating layer 7 has the function of receiving and retaining the charges of corona discharge in a dark place, and has the ability to transmit the light to which the charge generation layer is sensitive, and transmits the light upon exposure, and the charge generation layer It is necessary to neutralize and eliminate the surface charges by injecting the generated charges. As the coating material, organic insulating film-forming materials such as polyester and polyamide can be used. In addition, these organic materials and glass resin, S
It is also possible to use a mixture of inorganic materials such as in□ and materials that reduce electrical resistance such as metals and metal oxides. The coating material is not limited to organic insulating film-forming materials, and may also be formed using inorganic materials such as 5102, metals, metal oxides, etc. by methods such as vapor deposition and sputtering. As mentioned above, it is desirable that the coating material be as transparent as possible in the wavelength region where the charge generating substance absorbs maximum light.

The thickness of the coating layer itself depends on the composition of the coating layer, but
It can be set arbitrarily within a range that does not cause adverse effects such as an increase in residual potential when used repeatedly and continuously.

Hereinafter, specific examples of the present invention will be described.

Example 1 50 parts by weight of the azo compound represented by the compound Nα1,
Polyester resin (product name Byron 200: Toyo Hair)
100 parts by weight and 1-phenyl-3-(p-diethylaminostyryl)-5-(p-diethylaminophenyl)-
A coating solution was prepared by kneading 100 parts by weight of 2-pyrazoline (A S P P) and a tetrahydrofuran (THF) solvent in a mixer for 3 hours, and a coating solution was prepared using an aluminum vapor-deposited polyester film (A J!-P E T
), a photosensitive layer was formed by coating using a wire bar method so that the film thickness after drying would be 15 μm, thereby producing a photoreceptor having the structure shown in FIG. 1.

Example 2 First, a solution prepared by dissolving 100 parts by weight of p-diethylaminobenzaldehyde-diphenylhydrazone (ABPH) in 700 parts by weight of tetrahydrofuran (THF) and polycarbonate resin (Panlite-1250: manufactured by Teijin) 1
A coating solution prepared by dissolving 00 parts by weight in 700 parts by weight of a 1:1 mixed solvent of THF and dichloromethane was applied onto an aluminum vapor-deposited polyester film substrate using a wire bar method, and the film was dried. A charge transport layer was formed to have a thickness of 15 μm. On the charge transport layer thus obtained, 50 parts by weight of the azo compound represented by Compound No. 1 and a polyester resin (trade name: Vylon 200
．． Toyo Keiko) 50 parts by weight, PMMA 50 parts by weight in THF
A coating solution was prepared by kneading with a solvent in a mixer for 3 hours and applied using a wire bar method, resulting in a film thickness of 0.5 μm after drying.
A charge generation layer was formed in a thickness of m, and a photoreceptor corresponding to the structure shown in FIG. 3 was produced. However, a coating layer not directly related to this invention was not provided.

Example 3 The charge transport substance in Example 2 was changed from ABPH to α-phenyl-4′-N, which is a styryl compound.

A charge transport layer was formed in the same manner as in Example 2 except that N-dimethylaminostilbene was used, and a charge generation layer was further formed to produce a photoreceptor.

Example 4 A charge transport layer was formed in the same manner as in Example 2 except that the charge transport material in Example 2 was changed from ABPH to tri(p-)lylamine, which is a triphenylamine compound. A layer was formed to produce a photoreceptor.

Example 5 The charge transport substance in Example 2 was changed from ABPH to an oxadiazole compound] 2) 5-bis(p-diethylaminophenyl)-1,3,4-oxadiazole, and the rest was the same as in Example 2. A charge transport layer was formed in the same manner as above, and a charge generation layer was further formed to produce a photoreceptor.

The electrophotographic properties of the photoreceptor thus obtained were measured using an electrostatic recording paper tester RSP-428J manufactured by Kawaguchi Electric. The results are shown in Table 1.

The surface potential V, (volt) of the photoreceptor is +6□0kV in the dark
This is the initial surface potential when corona discharge is performed for 10 seconds to positively charge the surface of the photoreceptor, and then the surface potential is V d when the corona discharge is stopped and the surface is held in the dark for 2 seconds.
(volts), and then the illuminance 2 on the photoreceptor surface.
Calculate the time (seconds) it takes for V to be halved after irradiating lux white light, and calculate the half-attenuation exposure amount E17z (lux seconds)
And so. Further, the surface potential when white light with an illuminance of 2 lux was irradiated for 10 seconds was defined as the residual potential V, (volts).

, 1 Table 1 As seen in Table 1, the photoreceptors of Examples 1 to 5 had surface potential vs. half-attenuation exposure BEI/2. residual potential V,
Both were good.

Example 6 Azo compound 1 represented by the above compounds Nα2 to Nα35
A coating solution was prepared by kneading 100 parts by weight of each of 00 parts by weight of a polyester resin (trade name: Byron 200; Toyo Keiko) and a THF solvent for 3 hours in a mixer, and coated on an aluminum support to a thickness of about 0.5 μm. A charge generation layer was formed by applying the coating. On top of this 1. The charge transport material in Example 2 was changed from ABPH to ASPP, and the coating liquid for a charge transport layer obtained in the same manner as in Example 2 was applied to a thickness of about 15 μm to form a charge transport layer. A photoreceptor having the configuration shown in FIG. 2 was produced.

The electrophotographic properties of the photoreceptor thus obtained were evaluated in the same manner as in Example 1, except that the electrostatic recording paper tester RSP-428J manufactured by Kawaguchi Electric was used, and the charging polarity was changed from positive charging to negative charging. It was measured as follows. The results are shown in Table 2.

Table 2 (Part 2) Table (Part 3) Furthermore, if necessary, a coating layer can be provided on the surface to improve durability.

[Brief explanation of the drawing]

FIGS. 1, 2, and 3 are conceptual cross-sectional views showing different embodiments of the photoreceptor of the present invention. Reference Signs List 1 conductive substrate, 2 a, 2 b, 2 C photosensitive layer, 3 charge generating material, 4 charge generating layer, 5 charge transporting material, 6 - charge transporting layer, 7 coating layer. As seen in Table 2, the azo compound hidden 2~N(L
Also for the photoreceptor using 35, the half-attenuation exposure amount E +/
21 Both residual potential vr were good. [Effects of the Invention] According to the present invention, since the azo compound represented by the general formula (I) is used as a charge generating substance in the photosensitive layer formed on the conductive substrate, the azo compound represented by the general formula (I) is highly charged even in positive and negative charging. A photoreceptor with excellent sensitivity and repeatability can be obtained.

Claims (1)

[Scope of Claims] 1) An electrophotographic photoreceptor comprising a photosensitive layer containing at least one compound represented by the following general formula (I). ▲There are mathematical formulas, chemical formulas, tables, etc.▼ [In formula (I), Ar_1 and Ar_2 each represent one of the following optionally substituted aromatic hydrocarbon groups and aromatic heterocyclic groups (however, , cannot be a substituted or unsubstituted phenylene group at the same time), Cp
represents a coupler residue. 2) In the photoreceptor according to claim 1, Cp (coupler residue) in the general formula (I) is one of the following general formulas (II) to (V). A photoreceptor for electrophotography characterized by the following. ▲There are mathematical formulas, chemical formulas, tables, etc.▼−−−−−−−−−
(II) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼−−−−−(
III) ▲There are mathematical formulas, chemical formulas, tables, etc.▼−−−−−(
IV) ▲There are mathematical formulas, chemical formulas, tables, etc.▼------(V
) [In formulas (II) to (V), Z represents a residue condensed with a benzene ring to form a polycyclic aromatic ring or a heterocycle, and X_1 is OR_1 or NR_2R_3(R_1
, R_2 and R_3 represent a hydrogen atom, or each of the following optionally substituted alkyl groups, aryl groups, and aromatic heterocyclic groups), and X_2 and X_5 each represent the following substituted X_3 and X_6 represent any one of a hydrogen atom, a cyano group, a carbamoyl group, a carboxyl group, an ester group, and an acyl group. , X_4 represents a hydrogen atom, or any of the following optionally substituted alkyl groups, cycloalkyl groups, alkenyl groups, aryl groups, and aromatic heterocyclic groups, and X_7 and X_8 represent hydrogen atoms, halogen represents an atom, a nitro group, or any of the following optionally substituted alkyl groups and alkoxy groups, and X_9 is an alkyl group, an aryl group,
Represents either a carboxyl group or an ester group,
X_1_0 each represents either an optionally substituted aryl group or an aromatic heterocyclic group. ]