JP2003029436A - Electrophotographic photoreceptor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a positive electrification type electrophotographic photoreceptor having high sensitivity for a copying machine and for a printer by using a new organic material as a charge transporting material in a photosensitive layer. SOLUTION: In the electrophotographic photoreceptor obtained by disposing a photosensitive layer containing a charge generating material and a charge transporting material on an electrically conductive substrate, at least one electron transporting compound of formula (I) is contained as the charge transporting material in the photosensitive layer.

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to an electrophotographic photoreceptor (hereinafter, also simply referred to as a "photoreceptor"), and more particularly, to a photoconductive member containing an organic material on a conductive substrate. The present invention relates to an electrophotographic photosensitive member provided with a photosensitive layer and used for an electrophotographic printer, a copying machine, or the like. 2. Description of the Related Art Conventionally, as a photosensitive layer, an inorganic photoconductive substance such as selenium or a selenium alloy, or an inorganic photoconductive substance such as zinc oxide or cadmium sulfide is dispersed in a resin binder. Is generally used (hereinafter simply referred to as “inorganic photoreceptor”). However, in recent years, an electrophotographic photoconductor using an organic photoconductive substance (hereinafter, also simply referred to as “organic photoconductor”)
Research has progressed, and some of them have been put to practical use with improved sensitivity and durability. A photoreceptor is required to have a function of retaining a surface charge in a dark place, a function of receiving light to generate a charge, and a function of receiving light and transporting a charge. A so-called single-layer type photoreceptor that combines these functions in a single layer, and functions as a layer that mainly contributes to charge generation and a layer that contributes to charge retention and surface charge retention in dark places and charge transport during photoreception. There is a so-called laminated photoconductor in which separated layers are laminated. [0004] For example, the Carlson method is applied to image formation by electrophotography using these photosensitive members. Image formation in this method involves charging a photoreceptor by corona discharge in a dark place, forming an electrostatic latent image such as a character or picture of a document on the charged photoreceptor surface, and forming the electrostatic latent image After the toner image has been transferred, the photoreceptor is subjected to static elimination, removal of residual toner, light elimination, etc., and then reused. Is done. [0005] Practical organic photoreceptors have advantages such as flexibility, film forming property, low cost, and safety as compared with inorganic photoreceptors. Improvements are underway. [0006] Most of the organic photoreceptors are laminated organic photoreceptors in which functions are separated into a charge generation layer and a charge transport layer.
In general, a laminated organic photoreceptor has a pigment,
A charge generation layer containing a charge generation material such as a dye and a charge transport layer containing a charge transport material such as hydrazone and triphenylamine are sequentially formed. And becomes sensitive when the surface of the photoreceptor is negatively charged. However, in the negative charging type, the corona discharge used during charging is unstable compared to the positive charging type, and ozone and nitrogen oxides are generated, which adsorb on the photoreceptor surface and cause physical and chemical deterioration. There is a problem that it is easy to cause and worsens the environment.
From such a point, a positive charging type photoreceptor having a greater degree of freedom in use conditions is more advantageous and broader in application range than a negative charging type photoreceptor. In view of the above, a method has been proposed in which a charge generating substance and a charge transporting substance are simultaneously dispersed in a resin binder and used as a single photosensitive layer for use in a positively charged type, and some of them have been put to practical use. However, the sensitivity of the single-layer photoreceptor is not sufficient for application to a high-speed machine, and further improvement is necessary in terms of repetition characteristics and the like. Further, in order to obtain a function-separated type laminated structure for the purpose of increasing the sensitivity, a method of laminating a charge generating layer on a charge transporting layer to form a photoreceptor and use it in a positive charge type is also conceivable. However, in this method, since the charge generation layer is formed on the surface, there is a problem in stability during repeated use due to corona discharge, light irradiation, mechanical abrasion, and the like. In this case, it has been proposed to further provide a protective layer on the charge generation layer. However, although this improves mechanical wear, it has new problems such as lowering of electrical characteristics such as sensitivity. Furthermore, a method has been proposed in which a photoreceptor is formed by laminating an electron transporting charge transporting layer on the charge generating layer. As an electron transporting material, 2,4,7-trinitro-
Although 9-fluorenone and the like are known, this substance is carcinogenic and has a safety problem. In addition,
-131941, JP-A-6-59483,
JP-A-9-190002, JP-A-9-19000
In JP-A No. 3 and the like, cyano compounds, quinone-based compounds, and the like have been proposed, but in reality, compounds having sufficient electron transporting ability for practical use have not been obtained. SUMMARY OF THE INVENTION An object of the present invention is to provide a high-sensitivity copier and printer by using a new organic material which has never been used as a charge transport material in a photosensitive layer. To provide a positively-charged electrophotographic photoreceptor. Means for Solving the Problems The present inventors have conducted intensive studies on various organic materials in order to achieve the above-mentioned object, and as a result of conducting numerous experiments, the technical elucidation thereof is still not enough. Although not performed, a low reduction potential of the charge transport material is effective for improving electrophotographic properties, and a specific electron transport compound represented by the following general formula (I) is used as the charge transport material. As a result, the present inventors have found that a highly sensitive photoreceptor usable in positive charging can be obtained, and the present invention has been completed. That is, the electrophotographic photoreceptor of the present invention is an electrophotographic photoreceptor having a photosensitive layer containing a charge generating substance and a charge transporting substance on a conductive substrate. (I), (In the formula (I), R ¹ , R ² and R ³ each independently represent a hydrogen atom,
A halogen atom, an alkyl or alkoxy group having 1 to 6 carbon atoms which may have a substituent, a nitro group, a cyano group,
Or an aryl group which may have a substituent;
¹ and R ² each represent a ring-forming residue which may have a substituent; R ¹ , R ² and R ³ may be the same or different, and R ¹ and R ² When there are two or more, each of R ¹ and R ² may be the same or different, and A is an oxygen atom or ＣＲCR ⁵ R ⁶ (where R ⁵ and R ⁶ may be the same or different, respectively) , A cyano group or an alkoxycarbonyl group), m and n are 1
Wherein at least one of the electron-transporting compounds represented by the following formula (1) is contained as a charge-transporting substance: BEST MODE FOR CARRYING OUT THE INVENTION The specific examples of the compounds represented by the above general formula (I) are shown by the following structural formulas (I-1) to (I-13)
Indicated by [0014] [0015] The compound represented by the general formula (I) can be synthesized by a usual method. For example, the compound represented by the structural formula (I-5) has the following structural formula (I-5)
I), The compound of formula (I) is treated with an appropriate oxidizing agent (eg, potassium permanganate) in an organic solvent (eg, methylene chloride).
It can be easily synthesized by oxidizing in a mixed solution of water and an aqueous solution. Hereinafter, a specific configuration of a preferred example of the photosensitive member of the present invention will be described with reference to the drawings. 1 and 2 are schematic cross-sectional views showing various configuration examples of the photoconductor. FIG. 1 shows an example of the configuration of a so-called single-layer type photoreceptor, in which a charge generating substance and a charge transporting substance are dispersed on a conductive substrate 1 in a resin binder (binder). Is provided, and a coating layer (protective layer) 6 is further laminated as necessary. This single-layer type photoreceptor can be manufactured 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. If necessary, the coating layer 6 can be formed by coating. FIG. 2 shows an example of the configuration of a so-called laminated type photoreceptor, in which a charge generation layer 3 mainly composed of a charge generation substance and a charge transport layer 4 containing a charge transport substance are formed on a conductive substrate 1. Are provided in order. The laminated photoreceptor is obtained by vacuum-depositing a charge-generating substance on a conductive substrate or applying a dispersion obtained by dispersing particles of the charge-generating substance in a solvent or a resin binder, drying and coating the dispersion. It can be manufactured by applying and drying a solution in which a charge transport material and a resin binder are dissolved. Although not shown, an undercoat layer can be provided between the conductive substrate and the photosensitive layer in any type of photosensitive member. The undercoat layer can be provided as needed for the purpose of preventing injection of unnecessary charges from the conductive substrate into the photosensitive layer, covering defects on the surface of the substrate, improving the adhesiveness of the photosensitive layer, and the like. It is composed of a layer as a component, an oxide film such as alumite, and the like. Incidentally, any type of photoreceptor of the present invention contains at least one kind of the electron transporting compound represented by the general formula (I) as the charge transporting substance. Hereinafter, a preferred embodiment of the present invention will be described with reference to the laminated type photoreceptor shown in FIG. 2, but the present invention is not limited to the following specific examples. 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, or film-like. Metals such as nickel, glass, synthetic resin, or the like that has been subjected to a conductive treatment can be used. The charge generation layer 3 is formed by applying a material in which particles of a charge generation material are dispersed in a resin binder as described above, or by a method such as vacuum deposition.
Light is received to generate electric charge. In addition, the charge generation efficiency is high, and at the same time, the injection property of the generated charge into the charge transport layer 4 is important, and it is desirable that the electric field is less dependent on the electric field and the injection is good even at a low electric field. As the charge generating material, metal-free phthalocyanine, phthalocyanine compounds such as titanyl phthalocyanine, various azo, quinone, indigo, cyanine,
Pigments or dyes such as squarylium, azulhenium and pyrylium compounds, selenium or selenium compounds are used, and a suitable substance can be selected according to the light wavelength range of an exposure light source used for image formation. Since the charge generation layer only needs to have a charge generation function, its thickness is determined by the light absorption coefficient of the charge generation substance, and is generally 5 μm or less, preferably 2 μm or less. The charge generation layer may be mainly composed of a charge generation substance and may be used by adding a charge transporting substance or the like thereto. As the resin binder for the charge generation layer 3,
Polycarbonate, polyester, polyamide, polyurethane, vinyl chloride, phenoxy resin, polyvinyl butyral, diallyl phthalate resin, methacrylic acid ester polymers and copolymers, and the like can be used in appropriate combination. The charge transport layer 4 is a coating film in which at least one of the compounds represented by the general formula (I) is dispersed as an electron transporting substance in a resin binder. And has the function of transporting the charge injected from the charge generation layer during photoreception. In the present invention, it is necessary to include at least one kind of the compound represented by the general formula (I), which is the electron transporting substance according to the present invention, as the charge transporting substance. May be contained. The preferable addition amount of the electron transporting compound according to the present invention is preferably 10 to 60% by weight based on the entire material contained in the charge transporting layer 4.
More preferably, it is 15 to 50% by weight. As the resin binder for the charge transport layer 4,
Polymers and copolymers of polycarbonate, polyester, polystyrene, and methacrylate can be used. For the purpose of preventing ozone deterioration which is a hindrance in using the photoreceptor, the charge transport layer 4 is made of amine, phenol, sulfur, phosphite, phosphorus, etc. It is also possible to include an antioxidant. The coating layer 6 shown in FIG. 1 has a function of receiving and retaining the charge of corona discharge in a dark place, has a function of transmitting light which the photosensitive layer is sensitive to, and has a function of transmitting light when exposed. It is necessary that the surface charge is neutralized and eliminated by transmitting the generated charges to the photosensitive layer and receiving the generated charges. As the coating material, an organic insulating film forming material such as polyester and polyamide can be applied. In addition, a mixture of these organic materials and an inorganic material such as glass or SiO _2, or a material such as a metal or a metal oxide that reduces electric resistance can be used. 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 arbitrarily set within a range where adverse effects such as an increase in residual potential do not occur when used repeatedly and continuously. In the case of the single-layer type photoreceptor shown in FIG. 1, it is necessary that the photosensitive layer 2 contains at least one of the electron transporting compounds according to the present invention represented by the above general formula (I). However, other materials and the like may be the same as those of the above-described laminated photoreceptor, and are not particularly limited. Preferably, a hole transport material is contained together with the electron transport compound represented by the general formula (I) as the charge transport material. As the hole transporting substance, a benzidine derivative, a triphenylamine derivative, or the like is preferable. In this case, the preferable addition amount is 10 to 60% by weight, more preferably 1 to 60% by weight, of the electron transporting compound according to the present invention, based on the whole material contained in the photosensitive layer forming coating film.
5 to 50% by weight, preferably 10 to 60% by weight, more preferably 20 to 50% by weight for the hole transport material. The present invention will be described below with reference to examples. Example 1 2 parts by weight of x-type metal-free phthalocyanine (H ₂ Pc), 40 parts by weight of a compound represented by the structural formula (I-2), and the following formula (III) as a hole transport material: And a polycarbonate resin (PCZ-200: manufactured by Mitsubishi Gas Chemical Co., Ltd.)
100 parts by weight were mixed with methylene chloride for 3 hours using a mixer to prepare a coating solution, and a photosensitive layer was applied and formed on an aluminum support so that the film thickness after drying was 20 μm. A photoreceptor was prepared. Example 2 2 parts by weight of titanyl phthalocyanine (TiOPc), 40 parts by weight of the compound represented by the above structural formula (I-3), and the following formula (IV) as a hole transport material: 60 parts by weight of a benzidine derivative represented by the following formula and 100 parts by weight of a polycarbonate resin (BP-PC: manufactured by Idemitsu Kosan Co., Ltd.) were kneaded with methylene chloride by a mixer for 3 hours to prepare a coating solution, and the aluminum support was used. A photosensitive layer is applied and formed on the body so that the film thickness after drying is 20 μm,
A single-layer photoreceptor was prepared. Example 3 2 parts by weight of titanyl phthalocyanine (TiOPc), 40 parts by weight of the compound represented by the structural formula (I-4), and the following formula (V) as a hole transport material: And a polycarbonate resin (BP-PC: manufactured by Idemitsu Kosan Co., Ltd.)
80 parts by weight were kneaded with methylene chloride for 3 hours using a mixer to prepare a coating solution, and a photosensitive layer was formed by coating on an aluminum support so that the film thickness after drying was 20 μm. A photoreceptor was prepared. Example 4 In Example 2, the following formula (VI) was used instead of titanyl phthalocyanine: In the same manner as in Example 2, except that a compound represented by the structural formula (I-5) was used instead of the compound represented by the structural formula (I-3), A single-layer photoreceptor was prepared. Example 5 70 parts by weight of titanyl phthalocyanine (TiOPc)
A coating solution was prepared by kneading 30 parts by weight of a vinyl chloride copolymer (trade name: MR-110: manufactured by Nippon Zeon Co., Ltd.) with methylene chloride by a mixer for 3 hours to prepare a coating solution, and the thickness was reduced to about 1 μm on an aluminum support. To form a charge generation layer. Next, 100 parts by weight of the compound represented by the structural formula (I-7) and a polycarbonate resin (PCZ-
200: 100 parts by weight of Mitsubishi Gas Chemical Co., Ltd.) and 0.1 part by weight of silicone oil were mixed with methylene chloride,
A charge transport layer was formed on the charge generation layer obtained as described above so that the film thickness after drying was 10 μm, to produce a laminated photoreceptor. Example 6 In Example 2, the following formula (VII) was used instead of titanyl phthalocyanine: A bisazo pigment represented by the following formula (I)
In place of the compound represented by the formula (3), the structural formula (I-5)
A single-layer type photoreceptor was prepared in the same manner as in Example 2 except that the compound represented by the following formula was used. Example 7 In Example 2, the following formula (VIII) was used instead of titanyl phthalocyanine: A bisazo pigment represented by the following formula (I)
In place of the compound represented by formula -3), the structural formula (I-8)
A single-layer type photoreceptor was prepared in the same manner as in Example 2 except that the compound represented by the following formula was used. The electrophotographic characteristics of the photoreceptor thus obtained were measured as follows. That is, +4.5 in a dark place
The initial surface potential when the surface of the photoreceptor is positively charged by performing a corona discharge of kV is defined as Vs (V), and subsequently, the surface potential Vd (V) when the corona discharge is stopped and held in a dark place for 5 seconds. ) Was measured. Further, in Examples 1 to 5, monochromatic light (780 nm) of 1 μW was irradiated, and in Examples 6 and 7, white light having an illuminance of 100 lux was irradiated to determine the time (second) until Vd became half. Sensitivity E
_1/2 (μJ / cm ² or lx · s). Further, the residual potential Vr when this light is irradiated on the photoreceptor surface for 10 seconds.
(V) was measured. The measurement results are shown in Table 1 below. [Table 1] According to the present invention, since the electron transporting compound represented by the above general formula (I) is used as the charge transporting material in the photosensitive layer, the photosensitive layer has high sensitivity in positive charging and excellent electric characteristics. Photoreceptor can be obtained. In addition, a suitable substance can be selected as the charge generating substance in accordance with the type of the exposure light source. Obtainable. Furthermore, it is possible to improve the durability by providing a coating layer on the surface as needed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic cross-sectional view showing a configuration example of a single-layer type photoreceptor. FIG. 2 is a schematic cross-sectional view illustrating a configuration example of a laminated photoconductor. [Description of Signs] 1 conductive substrate 2 photosensitive layer 3 charge generation layer 4 charge transport layer 5 photosensitive layer (lamination) 6 coating layer

Claims (1)

Claims: 1. An electrophotographic photosensitive member having a photosensitive layer containing a charge generating substance and a charge transporting substance on a conductive substrate, wherein the photosensitive layer has the following general formula (I): (In the formula (I), R ¹ , R ² and R ³ each independently represent a hydrogen atom,
A halogen atom, an alkyl or alkoxy group having 1 to 6 carbon atoms which may have a substituent, a nitro group, a cyano group,
Or an aryl group which may have a substituent;
¹ and R ² each represent a ring-forming residue which may have a substituent; R ¹ , R ² and R ³ may be the same or different, and R ¹ and R ² And when R ¹ and R ² are the same or different, A is an oxygen atom or ＣＲCR ⁵ R ⁶ (where R ⁵ and R ⁶ may be the same or different, respectively) , A cyano group or an alkoxycarbonyl group), m and n are 1
Wherein at least one of the electron-transporting compounds represented by the following formula (1) is contained as a charge-transporting substance: