JPS6319659A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain the titled body having improved cycle stability and anti-environment property by constituting a carrier generating substance which is used to the carrier generating layer, from an azopigment or a phthalocyanine pigment, and an electron transfer substance which is used to the electron transfer layer from a Lewis acid, respectively. CONSTITUTION:The titled body is formed by laminating the positive hole transfer layer 12, the carrier generating layer 13 and the electron transfer layer 14 on a conductive substrate 11, in this order. The carrier generating substance and the electron transfer substance are composed of a combination of the specific substances respectively. Namely, the electron transfer substance is composed of the Lewis acid in the case that the carrier generating substance is made of the azopigment or the phthalocyanine pigment. The electron transfer substance is composed of a pyrazoline derivative or a hydrazone derivative in the case that the carrier generating substance is made of a polymethine coloring matter or an aquarinic acid coloring matter. As the trapping of the carrier does not occur at interfaces between each layers, the titled body has the excellent cycle stability in case of continuously using said body. And, as the carrier generated layer does not appear to the surface of the titled body, the titled body having the excellent anti-environment and less tendency for generating a change of the characteristics and a good durability is obtd. even in case that the surface of the titled body wears out.

Description

[Detailed description of the invention] [Technical field to which the invention pertains] The present invention relates to an electrophotographic photoreceptor, and more specifically, an electrophotographic photoreceptor that has excellent cycle stability, has high mechanical strength, and can be used with positive charging. It is related to.

[Prior art and its problems]

As a photoreceptor for electrophotography (hereinafter also simply referred to as a photoreceptor), it must be able to be charged to the required potential by corona discharge in a dark place, have little charge leakage, and have the ability to quickly discharge when irradiated with light. is required. Therefore, the photoconductive material used for the photosensitive layer of the photoreceptor must have a large charging ability in the dark and a low leakage current, and must have the ability to generate a large amount of carriers when irradiated with light. It is desired to have excellent transportation ability to quickly transport carriers.

As photoconductive materials with such performance, non-chemical photoconductive substances such as amorphous selenium alloys, zinc oxide, and cadmium sulfide have been used in the past, but in recent years, flexibility, resistance (impact resistance, Organic photoconductive materials have been attracting attention because of their thermal stability, film-forming properties, high sensitivity to long wavelength light, and low cost.

Furthermore, recently, there has been active research into functionally separated photoreceptors in which the performance of the photoreceptor is improved by assigning the aforementioned carrier generation function and carrier transport function to different substances. In such functionally separated type photoreceptors, many methods have been proposed that use organic dyes or pigments as carrier generating substances, such as azo pigments, phthalocyanine pigments, and indigo pigments.

These include polymethine dyes and squaric acid dyes.

Image formation on organic photoreceptors is usually performed using a negative corona charging method. However, since a large amount of ozone is generated in negative corona charging, the surface of the photoreceptor becomes oxidized by ozone during charging. Therefore, it is necessary to take measures to prevent ozone deterioration and to take measures against ozone in the copying machine itself.

On the other hand, positive corona charging has many advantages over negative corona charging, such as more stable corona discharge, less ozone generation, and easier production of compatible developers. It is more convenient. Therefore, the development of photoreceptors that can be used with positive charging is progressing, for example, using a binder in the photosensitive layer.

A single-layer photoreceptor containing a carrier-generating substance and further adding an electron-donating substance can be positively charged and has been put into practical use, but it is not always satisfactory in terms of photosensitivity, stability of characteristics, and durability. do not have.

Furthermore, many attempts have been made to realize the use of functionally separated laminated photoreceptors with positive charging, but none have reached the stage of practical use.

As shown in FIG. 2, this is a functionally separated type photoreceptor with a structure in which a carrier transport layer 2 is provided on a conductive substrate 1 and a carrier generation layer 3 is laminated thereon.The carrier transport layer 2 is used for hole transport. Attempts have been made to make positive charging possible by forming the battery with a material with a high capacity.

For example, a carrier generation layer formed by mixing a carrier generation substance containing a bisazo compound as a main component with a binder resin is provided on a carrier transport layer formed by mixing a styryl compound or an amine derivative as a carrier transport substance with a binder resin. A photoreceptor is disclosed (Japanese Patent Application Laid-Open No. 60-2503
Publication No. 46). Many photoreceptors have been proposed that have such a layer structure and can be used with positive charging (Japanese Patent Publication No. 47-2
1760, Special Publication No. 13344, etc.)
. However, during image formation, the surface of the photoreceptor comes into contact with a magnetic brush, transfer paper, and a toner cleaning blade and is subject to abrasion. At this time, if the surface of the photoreceptor is made of organic matter, the abrasion resistance will be weak, causing a problem that the surface will be scraped. Particularly in the case of the above-mentioned layer structure, the carrier generation layer on the surface is scraped off, resulting in a large change in characteristics such as photosensitivity.

Further, since the carrier generation layer is directly exposed to ozone, it deteriorates and the carrier generation ability changes, and the characteristics change significantly with repeated use.

In addition, as shown in FIG. 3, a carrier generation layer 3 is provided on a conductive substrate 1, and a carrier transport layer 2 is provided thereon, and the carrier transport layer 2 is formed of a material with a high electron transport ability and is positively charged. There are also attempts to make photoreceptors that can be used in For example, a pyrazoline derivative is used as a carrier transport material on the carrier generation layer 3 in which methine squarate dye is used as a carrier generation material, and this is mixed with a binder to transport carriers.
A photoreceptor in which a
3460), and many others (Japanese Unexamined Patent Application Publication No. 1973-
48334, JP-A-49-1231, JP-A-52-77730, etc.). However, since such a photoreceptor with the L configuration has a slow charging speed during corona charging, when used in a normal copying machine, not only does background smear occur on the image due to a decrease in surface potential, but it also makes it difficult to make multiple copies. If you do so, the characteristics will change. That is, it has disadvantages of poor cycle stability and memory phenomenon.

By the way, when a photoconductor is produced by laminating a carrier generation layer and a carrier transport layer, the behavior of carriers at the interface is important, and the optimal combination of the carrier generation material and carrier transport material to be used is important. It is known that there is a
. A carrier transporting substance that is effective for one carrier-generating substance is not necessarily effective for other carrier-generating substances, and a carrier-generating substance that is effective in combination with a certain carrier-generating substance may not be effective for other carrier-generating substances. Combinations with other substances may not necessarily be effective. If the combination of these two substances is inappropriate, the injection efficiency of carriers from the carrier generation layer to the carrier transport layer will be poor, and the sensitivity of the photoreceptor will be reduced. Furthermore, carriers will be trapped at the boundary between the two layers, resulting in a residual potential. increases, and cycle stability worsens. Various combinations of specific carrier-generating substances and carrier-transporting substances have been considered for photoreceptors with the above two layer configurations, but at present there are still organic material-based materials that have been put into practical use with positive charging. There is no photoreceptor.

JP-A-60-49342 proposes a bipolar electrophotographic photoreceptor, in which a hole transport layer is provided on a conductive substrate, and a carrier generation layer and an electron transport layer are further laminated in sequence. The body is disclosed as a positively charging laminated photoreceptor. In this photoreceptor, the carrier generation layer receives light and generates electrons and holes at approximately equal concentrations.
Electrons move to the interface with the electron transport layer, and holes move to the interface with the hole transport layer, and are injected into the respective layers. Since it is necessary for both electron and hole carriers to move rapidly in this way, the carrier generation layer is required to have a thin film thickness, and is in the range of 0.05 μm to 1 μm.

However, it is difficult to uniformly form such a thin film in mass production using, for example, a coating method, and if it is formed by, for example, vapor deposition, it requires a large device for the vapor deposition, which is technically difficult. There is a problem that industrial productivity is inferior.

[Purpose of the invention]

The present invention has been made in view of the above points, and is suitable for use with positive charging, has excellent cycle stability and environmental resistance, has little characteristic fluctuation even when the surface is mechanically abraded, and The purpose of the present invention is to provide an electrophotographic photoreceptor suitable for mass production.

[Key points of the invention]

The object of the present invention is to provide a hole transport layer on a conductive substrate.

A carrier-generating material used in a sensitive body having a structure in which a carrier-generating layer and an electron-transporting layer are sequentially laminated.

When the electron-transporting substance is a combination of specific substances, that is, when the carrier-generating substance is an azo pigment or a phthalocyanine pigment, a Lewis acid is used as the electron-transporting substance, and a polymethine dye or a squaric acid dye is used as the carrier-generating substance. When used, this is achieved by using a pyrazoline derivative or a hydrazone derivative as an electron transport material.

[Embodiments of the invention]

Examples of the present invention will be described below.

FIG.

12 is a hole transport layer, 13 is a carrier generation layer, and 14 is an electron transport layer.

The conductive substrate 11 serves as an electrode for the photoreceptor and at the same time serves as a support for the other layers, and may be in the form of a film, plate, or cylinder, and may be made of aluminum, stainless steel, or the like. It may also be made of metal, glass, ceramic, resin, or the like, whose surface is subjected to conductive treatment.

The hole transport layer 12 is a layer formed by dispersing an organic charge transport substance in a binder resin, and serves as an insulating layer in the dark to maintain the surface charge of the photoreceptor, and when receiving light, the carrier generation layer 13 It functions to transport more injected holes.

Formation of the hole transport layer 12 includes a hole transport material, a binder resin,
This is done by applying a homogeneous mixture of solvents and the like and drying it. Well-known hole transport substances include aromatic tertiary amino and tertiary diamino compounds, polyvinylcarbazole compounds, pyrazoline derivatives, quinazoline conductors, triazine monoconductors, benzofuran derivatives,
Oxadiazole derivatives, triphenylmethane derivatives,
Hydrazone derivatives and the like can be used. Further, as the binder resin, all general binder resins such as known electrically insulating and film-forming thermoplastic or thermosetting resins can be used. Examples of suitable binder resins include, but are not limited to, saturated polyester resins, polyamide resins, acrylic resins, polycarbonate resins, ethylene-vinyl acetate! Thermoplastic binder resins such as polyvinyl chloride and cellulose esters, thermosetting binders such as Evokin resin, urethane resins, phenol resins, and thermosetting acrylic resins. Further, as the solvent, for example, ether solvents such as tetrahydrofuran, aromatic hydrocarbons such as toluene, xylene, etc. are used.

Next, a carrier generating layer 13 is formed by applying a homogeneous mixture consisting of a carrier generating substance, a binder resin as described above, a solvent, etc. onto the hole transport layer 12 formed as described above and drying it. be done.

Next, on the carrier generation layer 13 formed as described above, a homogeneous mixture consisting of an electron transport substance, the binder resin as described above, a solvent, etc. is applied and dried to form an electron transport layer 14. . This electron transport layer 14
holds a positive charge as an insulating layer in the dark, and when exposed to light, transmits light with a wavelength to which the carrier generation layer is sensitive, generating hole-electron pairs within the carrier generation layer, and further injecting electrons from this layer. and transports it to the photoreceptor surface,
It has the ability to eliminate positive charges held on its surface. Therefore, it is desirable that the electron transport layer 14 be as transparent as possible in the wavelength range where the light absorption of the charge generating substance contained in the carrier generating layer is maximum.

The carrier-generating substance and the electron-transporting substance can be an electron-accepting substance, i.e., a Lewis acid (e.g., especially 2,4.7) IJ nitro-9, when azo i++ or phthalonanine@ material is used as the carrier-generating substance. - Combinations with fluorenone are preferred. Further, when a polymethine dye or a squaric acid dye is used as a carrier generating substance, the electron transporting substance is preferably combined with a hydrazone derivative or a pyrazoline derivative.

Generally, the film thickness of the carrier generation layer 13 is 0.005μlT1
~10 μm 1 The film thickness of the hole transport layer 12 and the electron transport layer 14 may be 1 μlT1 to 100 μm.

Hereinafter, preferred embodiments of the present invention will be described in detail by way of example.

Example 1 Hole transport material 1-phenyl-3-(P-diethylaminostyryl)-5-(paradiethylamine phenyl)-2
-Pyrazoline (ASPP: Anan +=+!ri 100
Part by weight dissolved in 700 parts by weight of tetrahydrofuran (TI-1F) and polymethyl methacrylate polymer (P
A cylindrical container is filled with a coating liquid made by mixing 100 parts by weight of MMΔ (manufactured by Tokyo Kasei) with 700 parts by weight of toluene, and the outer periphery of an aluminum drum with an outer diameter of 60 mm and a mirror-finished surface. A hole transport layer was formed by coating on top by a dip coating method so that the film thickness after drying was 10 μm.

On the hole transport layer obtained in this way, 1
Metal-free phthalonanine crushed for 50 hours (manufactured by Tokyo Kasei)
50 parts by weight and 100 parts by weight of ASPP were mixed with 100 parts of polyester resin (trade name Byron 200: manufactured by Toyobo) by BaT.
A coating solution prepared by kneading with an HF solvent in a ball mill for 3 hours was applied by the same dip coating method as described above to form one layer of scratch generation so that the film thickness after drying was 2 μm. Further, on this carrier generation layer, a coating solution prepared by dissolving 100 parts by weight of an electron transport substance 2,4°7 trinitro-9-fluorenone (TNF: manufactured by Tokyo Kasei) and 100 parts by weight of Vylon 200 in 500 parts by weight of THF was applied by dip coating. A photoreceptor was prepared by coating and forming a seal for electron transport so that the film thickness after drying was 5 μm.

Practical Can Example 2 A bisazo compound having the following structural formula was ground into particles of 1 μm or less using a ball mill. 1 part by weight of the pulverized fine particles of the bisazo compound and 30 parts by weight of N,N-dimethylformamide (DMF), which is a polar organic solvent, were subjected to ultrasonic dispersion treatment for 2 hours using an ultrasonic homogenizer, so that the fine particles of the bisazo compound A homogeneously dispersed) suspension was made in a polar organic solvent. Add polymethyl methacrylate (
Add 1 part of PMMΔ) and 6 parts by weight of toluene, mix well with a magnetic stirrer to prepare a uniform coating solution, and apply this coating solution on the hole transport layer prepared according to Example 1. Applied by dip coating method, film thickness after drying is 1.5
A carrier generation layer having a diameter of .mu.m was formed, and an electron transport layer was further laminated thereon in accordance with Example 1 to obtain a photoreceptor.

Example 3 A solution prepared by dissolving 10 parts by weight of polymethine dye (IR-820: manufactured by Nippon Kayaku Co., Ltd.) in 500 parts by weight of tetrahydrofuran (THF) and polymethyl methacrylate (PMMA)
) A uniform coating solution was prepared by mixing 10 parts by weight with a solution obtained by dissolving 10 parts by weight in 60 parts by weight of toluene.

This coating solution was applied by dip coating onto the hole transport layer prepared according to Example 1, and the film thickness after drying was 1.5 μm.
A carrier generation layer having a thickness of m was formed.

Next, the same coating solution as that used to form the hole transport layer in Example 1 was applied thereon by dip coating to form an electron transport layer with a film thickness of 5 μm after drying, thereby forming a photoreceptor. .

Comparative Example 1.2.3 Except for not providing an electron transport layer; respectively Example 1.
A photoreceptor was prepared according to 2.3, and a comparative example 1°2.3 was prepared.

In order to evaluate the electrophotographic characteristics of these photoreceptors, a copying test was conducted using a commercially available plain paper copying machine, and the resulting image quality was evaluated. All of the photoreceptors of the examples obtained images of good quality, and even after 1000 continuous copies, there was no change in image density, no memory phenomenon occurred, and the cycle stability was excellent. No disturbance occurred. The photoreceptors of these examples are positively charged and are fully usable for practical use.

On the other hand, with respect to the photoreceptor of the comparative example, a good image was initially obtained, but disturbances were observed in the image after 1000 copies. This is due to the carrier generation layer on the surface being abraded by friction, resulting in poor durability.

There is a problem with cycle stability.

〔Effect of the invention〕

According to the invention, a hole transport layer on a conductive substrate.

A carrier-generating substance used in a photoreceptor having a structure in which a carrier-generating layer and an electron-transporting layer are sequentially attached.

Select electron transport materials and create a specific combination of materials. By optimizing this combination of materials, carriers are not trapped at the interfaces of each layer (good injection is performed, carrier transport is performed smoothly,
A photoreceptor that is positively charged and is fully usable for practical use can be obtained. In addition, since carrier transportability is good, the thickness of the carrier generation layer is 1 μm.
It is possible to increase the thickness to a certain extent, from m to 3 μm, and it is possible to form a carrier generation layer by, for example, a coating method, and it is possible to mass-produce at low cost. Since there are no carrier traps at the interfaces of each layer, cycle stability is excellent when the photoreceptor is used continuously. Also, since the carrier generation layer is not exposed on the surface, it has excellent environmental resistance and the surface is not mechanically abraded. It has good durability with little variation in characteristics.

Furthermore, since the carrier-generating substance of the present invention has the ability to generate carriers even with light in the infrared region, the photoreceptor of the present invention can be expected to be used as a photoreceptor for semiconductor laser beam printers.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view showing the layer structure of one embodiment of the photoreceptor of the present invention, and FIGS. 2 and 3 are schematic sectional views showing the layer structure of different examples of conventional photoreceptors. be. 11 conductive substrate, 12 hole transport layer, 13 carrier generation layer, 14 electron transport layer.

Claims (1)

[Claims] 1) An electrophotographic photoreceptor in which a hole transport layer, a carrier generation layer, and an electron transport layer are sequentially laminated on a conductive substrate, in which a carrier generation substance used in the carrier generation layer is 1. An electrophotographic photoreceptor, wherein the electron transport material used in the electron transport layer is an azo pigment or a phthalocyanine pigment, and a Lewis acid. 2) In an electrophotographic photoreceptor in which a hole transport layer, a carrier generation layer, and an electron transport layer are sequentially laminated on a conductive substrate, the carrier generation substance used in the carrier generation layer is a polymethine dye or squaric acid. 1. An electrophotographic photoreceptor, which is a dye, and the electron transport material used in the electron transport layer is a pyrazoline derivative or a hydrazone derivative.