JP2833192B2 - Electrophotographic photoreceptor - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an electrophotographic photoreceptor, and more particularly, to a photoconductive layer formed on a conductive substrate, represented by the general formula (I): The present invention relates to a photoconductor for electrophotography, comprising a bisazo compound.

[Prior Art] Photoconductors for electrophotography (hereinafter also referred to as photoconductors) are generally widely used in copiers and printers, and various materials have been studied and put into practical use since the invention of the Carlson method.
For example, photoreceptors using inorganic photoconductive substances such as selenium, zinc oxide, and cadmium sulfide are well known, but these have excellent light sensitivity but have problems in moisture resistance, durability, and the like. Selenium and cadmium sulfide have the disadvantage of being toxic. On the other hand, a photoreceptor using an organic photoconductive substance can separate functions into a charge generation material that generates charges by light irradiation and a charge transport material that transports the charges, so that any material can be easily obtained. , More inexpensive and excellent in hygiene, flexibility, heat stability,
In recent years, many photoconductors have been proposed because of their advantages such as film formability. Particularly, a photoconductive organic compound having excellent charge generating ability is described in, for example, phthalocyanine described in U.S. Pat.No. 3,816,118, anthranthrone described in JP-B-60-60052, and JP-A-61-29496. Squarylium, azurenium described in JP-A-50-133550, and the like have been put to practical use.

[Problems to be Solved by the Invention] As described above, an organic material has many advantages that an inorganic material does not have, but at the same time, a material that sufficiently satisfies all the characteristics required for an electrophotographic photoreceptor is not yet available. At present, it has not been obtained, and in particular, the characteristics at the time of high sensitivity and repeated continuous use are poor, and there has been a problem with image defects.

The present invention has been made in view of the above points, and uses a new organic material that has never been used as a charge generating material in the photosensitive layer to provide high sensitivity, excellent repetition characteristics, and excellent durability. It is another object of the present invention to provide an electrophotographic photosensitive member for a copying machine and a printer, which has no image unevenness.

[Means for Solving the Problems] To achieve the above object, according to the present invention, an electrophotographic photoreceptor having a photosensitive layer containing at least one bisazo compound represented by the following general formula (I) And

(In the formula, A represents a substituted or unsubstituted aromatic hydrocarbon, a condensed polycyclic or heterocyclic residue, and R represents any one of a hydrogen atom, a halogen atom, and an alkyl group or an aryl group each of which may be substituted. [Action] There is no known example of using the bisazo compound represented by the general formula (I) 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 conducting a number of experiments on these bisazo compounds, the technical elucidation has not yet been sufficiently completed. It has been found that the use of a specific bisazo compound represented by the above general formula (I) as a charge generating substance is extremely effective in improving electrophotographic properties, and is excellent in repetition characteristics, durability, etc. with high sensitivity, In addition, a good-quality photoreceptor having good dispersibility of the pigment and good applicability and having no image unevenness was obtained.

[Examples] The compound represented by the general formula (I) is represented by the following general formula (II) H ₂ N-A-NH ₂ (II) (wherein A has the same meaning as described above). The amino compound is tetrazotized by a conventional method, and is represented by the following general formula (III) (Wherein R represents the same meaning as described above) and a suitable solvent (eg, N, N
-Dimethylformamide, dimethylsulfoxide, etc.) to easily synthesize. Specific examples of the bisazo compound represented by the general formula (I) thus obtained will be exemplified.

The photoreceptor of the present invention contains the compound represented by the general formula (I) in the photosensitive layer. Depending on how these compounds are applied, FIG. 1, FIG.
It can be used as shown in the figure.

1 to 3 are conceptual sectional views of the photoreceptor of the present invention.
1 is a conductive substrate, 20, 21, and 22 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. A photosensitive layer 20 (usually referred to as a single-layer type photoreceptor) in which a compound of the general formula (I) as the charge generating substance 3 and a charge transporting substance 5 are dispersed in a resin binder is provided on a conductive substrate 1. It is a thing.

FIG. 2 shows a laminate of a charge generation layer 4 containing a compound of the general formula (I), which is a charge generation substance 3, on a conductive substrate 1 and a charge transport layer 6 mainly composed of a charge transport substance 5. (Usually referred to as a laminated photoreceptor).

FIG. 3 shows the reverse layer configuration of FIG. In this case, it is general to further provide a coating layer 7 to protect the charge generation layer 4.

The reason why the two types of layer constitutions shown in FIGS. 2 and 3 are adopted is that even if the layer constitution shown in FIG. This has not been found, and therefore, the layer configuration shown in FIG. 3 is required at this stage as a positive charging type photoconductor.

The photoreceptor shown in FIG. 1 can be prepared 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 on 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 prepared 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 a liquid, drying, and further forming a coating layer.

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

The charge generation layer 4 is formed by applying a material in which particles of the charge generation substance 3 which is a bisazo compound represented by the general formula (I) are dispersed in a resin binder, and receives light to generate charges. In addition, it is important that the charge generation efficiency is high and at the same time, the generated charge is injected into the charge transporting layer 6 and the coating layer 7. The charge generation layer can be mainly composed of a charge generation substance and added with a charge transporting substance or the like. As the resin binder, polycarbonate, polyester, polyamide, polyurethane, vinyl chloride, epoxy, silicone resin, diallyl phthalate resin, butyral resin, polymers and copolymers of methacrylic acid esters, and the like can be appropriately used in combination. .

The proportion of the bisazo compound represented by the general formula (I) is from 5 to 95% by weight, preferably from 50 to 95% by weight, based on the resin binder.
The solvent is 85% by weight, and examples of the solvent include dichloromethane, dichloroethane, ethyl acetate, methyl ethyl ketone, dimethylformamide, and tetrahydrofuran.

The charge transport layer 6 is formed by applying a material in which a hydrazone compound, a pyrazoline compound, a stilbene compound, a triphenylamine compound, an oxazole compound, an oxadiazole compound, or the like is dissolved and dispersed as an organic charge transporting substance in a resin binder. It is formed. In a dark place, it functions as an insulator layer to hold the charge of the photoreceptor, and to transport the charge injected from the charge generation layer when receiving light. As the resin binder, polymers, copolymers, and the like of polycarbonate, polyester, and methacrylate can be used.

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. In addition, these organic materials and glass resin, SiO ₂
It is also possible to use a mixture of an inorganic material such as a material, a metal alkoxy compound having a film forming ability, and a material such as a metal or a metal oxide which reduces electric resistance. The coating material is not limited to an organic insulating film-forming material, and may be formed by an inorganic material such as SiO _2, or a metal, a metal oxide, or the like by a method such as evaporation or sputtering. As described above, it is desirable that the coating material is as transparent as possible in the wavelength region of the light absorption maximum of the charge generation layer.

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.

 Hereinafter, examples of the present invention will be described.

Example 1 10 parts by weight of the compound represented by the compound No. I-1-1 was mixed with 100 parts by weight of a polyester resin (trade name: Byron 200, manufactured by Toyobo) and 1-phenyl-3- (p-diethylaminostyryl) -5- ( 100 parts by weight of p-diethylaminophenyl) -2-pyrazoline (ASPP) and tetrahydrofuran (THF)
A coating liquid is prepared by kneading with a mixer for 3 hours together with a solvent, and is coated on an aluminum-evaporated polyester film (Al-PET) as a conductive substrate by a wire bar method, and the film thickness after drying becomes 15 μm. A photoreceptor was prepared as described above.

Example 2 First, a coating liquid formed by dissolving 100 parts by weight of p-diethylaminobenzaldehyde-diphenylhydrazone (ABPH) and 100 parts by weight of a polycarbonate resin (trade name: Panlite L-1250: Teijin Chemicals) with methylene chloride was subjected to aluminum evaporation. It was applied on a polyester film substrate with a wire bar, and a charge transport layer was formed so that the film thickness after drying was 15 μm. On the thus obtained charge transport layer, the compound
50 parts by weight of the compound represented by No. I-1-2, 50 parts by weight of a polyester resin (trade name: Byron 200, manufactured by Toyobo) and a THF solvent were kneaded with a mixer for 3 hours to prepare a coating solution, and a wire bar was used. The charge generation layer was formed so that the thickness after coating and drying was 0.5 μm.

Example 3 In Example 2, the charge transport material was changed to ABPH,
Α-phenyl-4′-N, N- which is a stilbene compound
A charge transport layer was formed in the same manner as in Example 2 using dimethylaminostilbene, and a charge generation layer was further formed to prepare a photoreceptor.

Example 4 In Example 2, the charge transport material was changed to ABPH,
Tri (p-tolyl) which is a triphenylamine compound
A charge transport layer was formed in the same manner as in Example 2 using an amine, and a charge generation layer was further formed to prepare a photoreceptor.

Example 5 In Example 2, the charge transport material was changed to ABPH,
Using 2,5-bis (p-diethylaminophenyl) -1,3,4-oxadiazole, which is an oxadiazole compound, a charge transport layer was formed in the same manner as in Example 2, and a charge generation layer was further formed. A photoreceptor was made.

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 residual voltage V _r (volt). Table 1 shows the results.

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

Example 6 Compound Nos. I-1-3 to I-1-22, I-2-1 to I
-2-14, I-3-1 to I-3-14, I-4-1 to I-4-
A coating solution is prepared by kneading 100 parts by weight of the compound represented by 14 with 100 parts by weight of a polyester resin (trade name: Byron 200) and a THF solvent by a mixer for 3 hours to prepare a coating solution so that the thickness becomes about 0.5 μm on an aluminum support. To form a charge generation layer. A coating solution of ABPH obtained in the same manner as in Example 2 was applied thereon so as to have a thickness of about 15 μm, thereby preparing 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 surface potential V _s of the photoconductor (V) is the initial surface potential when the corona discharge of -0.6kV was allowed negatively charged surface of the photosensitive member conducted for 10 seconds in the dark, followed by the state was discontinued corona discharge , 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). Table 2 shows the results.

As seen in Table 2, the bisazo compound No. I-
1-3 to I-1-22, I-2-1 to I-2-14, I-3-1
-I-3-14 and I-4-1 to I-4-14 as the charge generating substances also showed good half-attenuation exposure amounts E1 _{/ 2} .

〔The invention's effect〕

According to the present invention, the compound represented by the general formula (I) is used as a charge generating substance on a conductive substrate, so that it has high sensitivity and excellent repetition characteristics even in positive charging and negative charging, and furthermore, it is possible to prevent image unevenness. No good photoreceptor can be obtained. Further, it is possible to improve 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 different embodiments of the photoreceptor of the present invention. DESCRIPTION OF SYMBOLS 1 ... Conductive base, 3 ... Charge generating substance, 4 ... Charge generating layer, 5 ... Charge transporting substance, 6 ... Charge transporting layer, 7 ... Coating layer, 20,21,22 ... Photosensitive layer .

Claims (1)

(57) [Claims] 1. An electrophotographic photosensitive member comprising a photosensitive layer containing at least one of the bisazo compounds represented by the following general formula (I). (In the formula, A represents a substituted or unsubstituted aromatic hydrocarbon, a condensed polycyclic or heterocyclic residue, and R represents any one of a hydrogen atom, a halogen atom, and an alkyl group or an aryl group each of which may be substituted. Represents.)