JP2629752B2 - Electrophotographic photoreceptor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electrophotographic photoreceptor, and more particularly to a photosensitive layer formed on a conductive substrate.

[Conventional technology]

Conventionally, photoconductors for electrophotography (hereinafter also referred to as photoconductors)
Examples of the photosensitive material include inorganic photoconductive substances such as selenium or a selenium alloy, inorganic photoconductive substances such as zinc oxide and cadmium sulfide dispersed in a resin binder, poly-N-vinyl carbazole or polyvinyl. An organic photoconductive substance such as anthracene, an organic photoconductive substance such as a phthalocyanine compound or a bisazo compound dispersed in a resin binder, or a material obtained by vacuum evaporation is used.

The photoreceptor must have the function of retaining surface charges in a dark place, the function of receiving light to generate charges, and the function of receiving light and transporting charges. A so-called single-layer type photoreceptor that combines functions and a layer that separates functions into a layer that mainly contributes to charge generation and a layer that contributes to charge retention and surface transport in dark places and charge transport during photoreception. There is a laminated photoreceptor. For image formation by electrophotography using these photoconductors, for example, the Carlson method is applied. Image formation in this method involves charging a photoreceptor in a dark place by corona discharge, forming an electrostatic latent image such as a character or picture on a document by exposing the charged photoreceptor surface, and forming the formed electrostatic The latent image is developed with toner, and the developed toner image is fixed on a support such as paper. The photoreceptor after transfer of the toner image is subjected to charge elimination, removal of residual toner, light charge elimination, etc., and then reused. To be served.

In recent years, electrophotographic photoreceptors using organic materials have been put to practical use due to advantages such as flexibility, thermal stability, and film forming properties. For example, poly-N-vinyl carbazole and
A photoreceptor comprising 2,4,7-trinitrofluoren-9-one (described in U.S. Pat. No. 3,484,237) and a photoreceptor containing an organic pigment as a main component (described in JP-A-47-37543) ), And a photoreceptor having a eutectic complex comprising a dye and a resin as a main component (described in JP-A-47-10735). Further, many new azo compounds and perylene compounds have been put to practical use.

[Problems to be solved by the invention]

As described above, organic materials have many advantages that inorganic materials do not have. However, at present, there is still no material that sufficiently satisfies all the characteristics required for electrophotographic photoreceptors. In particular, there was a problem in light sensitivity and characteristics in repeated continuous use.

The present invention has been made in view of the above points,
An object of the present invention is to provide an electrophotographic photoreceptor excellent in photosensitivity for a copying machine and a printer by using a new organic material which has not been used as a charge generating material in the photosensitive layer.

[Means for solving the problem]

The above object is achieved according to the present invention by the general formula Wherein R ₁ , R ₂ , R ₃ and R ₄ are a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group or an aryl group, and A is a coupler residue. This is achieved by providing a photosensitive layer.

The azo compound of the general formula used in the present invention is synthesized by reacting the corresponding diazonium salt and coupler with a base in a suitable organic solvent such as N, N-dimethylformamide (DMF) to cause a coupling reaction. can do. Specific examples of the azo compound of the general formula thus obtained are as follows.

The photoreceptor of the present invention contains an azo compound represented by the above general formula in the photosensitive layer. Depending on how these azo compounds are applied, the photoreceptor shown in FIG. 1, FIG. 2 or FIG. It can be used as follows.

1 to 3 are conceptual sectional views of the photoreceptor of the present invention.
1 is a conductive substrate, 2A, 2B and 2C are photosensitive layers, 3 is a charge generating material, 4 is a charge generating layer, 5 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 referred to as a single-layer type photoreceptor) in which an azo compound as a charge generating substance 3 and a charge transporting substance 5 are dispersed in a resin binder on a conductive substrate 1. Things.

FIG. 2 shows a photosensitive layer 2B (usually composed of a laminate of a charge generation layer 4 containing an azo compound as a charge generation substance 3 and a charge transport layer 6 mainly composed of a charge transport substance 5 on a conductive substrate 1). (A configuration referred to as a stacked photoconductor).

 FIG. 3 shows the reverse layer configuration of FIG.

The reason why the layer structure shown in FIGS. 2 and 3 is adopted is that the layer structure shown in FIG. 2 is usually used as a negative charging system. Even if the layer configuration shown in FIG.
At present, there is no charge transport material suitable for this. Accordingly, as a photoreceptor of the positive charging type, as already proposed by the present inventors, the layer configuration shown in FIG. 3 can be mentioned.

The photoreceptor shown in FIG. 1 can be produced by dispersing a charge generating substance in a solution in which a charge transporting substance and a resin binder are dissolved, and applying this dispersion to a conductive substrate.

In the photoreceptor of FIG. 2, a dispersion obtained by dispersing particles of a charge generating substance in a solvent or a resin binder on a conductive substrate was applied and dried, and the charge transporting substance and the resin binder were dissolved thereon. It can be produced by applying and drying a solution.

The photoreceptor shown in FIG. 3 is obtained by applying a solution in which a charge transporting substance and a resin binder are dissolved on a conductive substrate, drying the solution, and then dispersing the particles of the charge generating substance in a solvent or a resin binder. It can be prepared by applying and drying a liquid.

The conductive substrate 1 serves as an electrode of the photoreceptor and serves as a support for the other layers, and may be cylindrical, plate-like, film-like, or made of aluminum, stainless steel, nickel, or the like. A conductive material may be applied to metal, glass, resin, or the like.

The charge generation layer 4 is formed by applying a material in which particles of the charge generation material 3 represented by an azo compound represented by a general formula are dispersed in a resin binder, and receives light to generate charges. In addition, the charge generation efficiency is high, and at the same time, the injected property of the generated charge into the charge transport layer 6 and the coating layer 7 is demanded. It is desirable that the electric field is less dependent and the injection is good even at a low electric field. The charge generation layer may be mainly composed of a charge generation substance, to which a charge transport substance or the like is added. As the resin binder, polycarbonate,
Polyester, polyamide, polyurethane, epoxy,
It is possible to use a suitable combination of a polymer and a copolymer of a silicone resin and a methacrylate ester.

The charge transport layer 6 is formed by applying a material in which a hydrazone compound, a pyrazoline compound, a styryl compound, a triphenylamine compound, an oxazole compound, an oxadiazole compound, or the like is dissolved and dispersed as an organic charge transport material in a resin binder. In a dark place, it functions as an insulator layer to retain the charge of the photoreceptor, and at the time of receiving light, exhibits a function of transporting charge injected from the charge generation layer. Examples of the resin binder include polycarbonate, polyester, polyamide, polyurethane, epoxy, silicone resin, and methacrylate polymers and copolymers.

The coating layer 7 has a function of receiving and holding the charge of the corona discharge in a dark place, and has a performance of transmitting light which the charge generation layer is sensitive to. It is necessary that the surface charge is neutralized and eliminated by receiving the generated charge. As the coating material, an organic insulating film forming material such as polyester and polyamide can be applied. It is also possible to use a mixture of these organic materials with an inorganic material such as glass resin or silicon dioxide, or a material such as a metal or a metal oxide that reduces the electric resistance. The coating material is not limited to an organic insulating film forming material, but may be an inorganic material such as silicon dioxide, or a metal, metal oxide, or the like, formed by a method such as vapor deposition or sputtering. As described above, it is desirable that the coating material is as transparent as possible in the wavelength region where the light absorption of the charge generating substance is maximum.

Although the thickness of the coating layer itself depends on the composition of the coating layer, it can be set arbitrarily within a range where adverse effects such as an increase in residual potential do not occur when repeatedly used continuously.

[Action]

There is no known example of using the azo compound represented by the above general formula in a photosensitive layer. The present inventors have conducted intensive studies on various organic materials in order to achieve the above object, and as a result of carrying out a number of experiments on these azo compounds, the technical elucidation has not yet been sufficiently completed. The azo compound represented by the general formula is used as a charge generating substance in the photosensitive layer of a single-layer or laminated photoreceptor, and has been found to be extremely effective in improving electrophotographic properties, and has excellent photosensitivity. The photoreceptor was obtained.

〔Example〕

 Hereinafter, examples of the present invention will be described.

Example 1 50 parts by weight of the azo compound represented by the above compound No. 1 was mixed with 100 parts by weight of a polyester resin and 1-phenyl-3- (p-
A coating solution was prepared by kneading with 100 parts by weight of diethylaminostyryl) -5- (p-diethylaminophenyl) -2-pyrazoline (ASPP) and a solvent of tetrahydrofuran (THF) for 3 hours to prepare a coating solution, and aluminum deposition as a conductive substrate was performed. A photosensitive layer was formed on a polyester film by coating by a wire bar method to form a photosensitive layer so that the film thickness after drying was 15 μm.

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 100 parts by weight of a polycarbonate resin were mixed in a 1: 1 solvent mixture of THF and dichloromethane.
A solution prepared by mixing the solution with 700 parts by weight was applied to an aluminum-evaporated polyester film substrate by a wire bar method, and a charge transport layer was formed so that the film thickness after drying was 15 μm. On the charge transport obtained in this way,
50 parts by weight of the azo compound represented by the compound No. 1, 50 parts by weight of a polyester resin, 50 parts by weight of PMMA, and 3 parts together with a THF solvent.
The coating solution was adjusted by kneading with a time mixer, applied by a wire bar method, and a charge generation layer was formed so that the film thickness after drying was 0.5 μm, thereby producing a photoreceptor shown in FIG.

Example 3 In Example 2, a charge transport layer was formed in the same manner as in Example 2 except that the charge transport material was changed to ABPH and α-phenyl-4′-N, N-dimethylaminostilbene, a styryl compound, was used. Further, a charge generation layer was formed to prepare a photoreceptor.

Example 4 In Example 2, a charge transport layer was formed in the same manner as in Example 2 except that triphenylamine compound tri (p-tolyl) amine was used instead of ABPH as the charge transport material, and a charge generation layer was further formed. Then, a photoreceptor was prepared.

Example 5 In Example 2, the charge transporting substance was changed to ABPH, and the oxadiazole compound 2,5-bis (p-diethylaminophenyl) -1,3,4-oxadiazole was used. Similarly, a charge transport layer was formed, and further, a charge generation layer was formed to prepare a photoreceptor.

The electrophotographic characteristics of the photoreceptor thus obtained were measured using an electrostatic recording paper tester “SP-428” manufactured by Kawaguchi Electric.

The photoconductor surface potential V _s (volts) is the initial surface potential when the surface of the photoconductor is positively charged by performing a +6.0 kV corona discharge in a dark place for 10 seconds, and then the corona discharge is stopped. , The surface potential V _d (volts) when kept in a dark place for 2 seconds is measured, and then the time until the V _d is halved by irradiating the surface of the photoreceptor with white light having an illuminance of 2 lux (seconds)
Was determined and defined as a half-attenuation exposure amount E _1/2 (looks / second). The surface potential when white light having an illuminance of 2 lux was irradiated for 10 seconds was defined as a residual potential V _r (volt).

As can be seen from Table 1, Examples 1, 2, 3, 4, and 5 exhibited good half-attenuation exposure and residual potential.

Example 6 100 parts by weight of the azo compounds represented by the compounds No. 2 to No. 30 were kneaded together with 100 parts by weight of a polyester resin and a THF solvent by a mixer for 3 hours to prepare a coating solution. It was applied so as to have a thickness of about 0.5 μm to form a charge generation layer. Onto this, a coating solution for forming a charge transport layer using ASPP obtained by the same method as that prepared in Example 2 was applied to a thickness of about 15 μm to prepare a photoreceptor.

The electrophotographic characteristics of the photoreceptor thus obtained were measured using an electrostatic recording paper tester “SP-428” manufactured by Kawaguchi Electric. Table 2 shows the results.

The surface of the photoreceptor was subjected to a −6.0 kV corona discharge in a dark place for 10 seconds to be negatively charged, and then the surface potential V _d (volt) was measured when the corona discharge was stopped and kept in a dark place for 2 seconds. Then, the surface of the photoreceptor was irradiated with white light having an illuminance of 2 lux, and the time (second) until _Vd became approximately half was determined to be a half-attenuated exposure amount E _1/2 (lux second). The surface potential when white light having an illuminance of 2 lux was irradiated for 10 seconds was defined as a residual potential V _r (volt). Both the half-attenuation exposure amount and the residual potential are good.

[Effects of the Invention] According to the present invention, since the azo compound represented by the above general formula is used as a charge generating substance on a conductive substrate, an excellent photosensitive member having high sensitivity even in positive charging and negative charging is obtained. be able to. Further, it is possible to improve the durability by providing a coating layer on the surface as needed.

[Brief description of the drawings]

1, 2 and 3 are conceptual sectional views showing one embodiment of the photoreceptor of the present invention. DESCRIPTION OF SYMBOLS 1 ... Conductive base material, 2A, 2B, 2C ... Photosensitive layer, 3 ... Charge generating material, 4 ... Charge generating layer, 5 ... Charge transporting material, 6 ...
... charge transport layer, 7 ... coating layer.

Claims (1)

(57) [Claims] (1) General formula Wherein R ₁ , R ₂ , R ₃ and R ₄ are a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group or an aryl group, and A is a coupler residue. An electrophotographic photosensitive member comprising a photosensitive layer.