JPH0457058A - Electrophotographic photoreceptor - Google Patents

Abstract

PURPOSE:To obtain a sensitive body having superior sensitivity and ensuring superior characteristics of an image by rendering a two-layered structure composed of an electric charge generating layer formed with a mixture of metal-free tau-phthalocyanine with a solvent for the phthalocyanine and a polymer binder and an electric charge transferring layer formed on the electric charge generating layer. CONSTITUTION:A coating liq. for a sensitive body is prepd. by charging tau- phthalocyanine, a solvent having ability to dissolve part of the phthalocyanine and a polymer binder into a reactor and well mixing them by stirring. The optimum weight ratio between the phthalocyanine and the polymer binder is (2:1)-(1:10). A substrate is coated with the coating liq. to form an electric charge generating layer and an electric charge transferring layer is further formed on the electric charge generating layer to obtain a sensitive body.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an electrophotographic photoreceptor for forming electrophotographic images.

Conventional technologyOrganic photoreceptors (abbreviated as OPC) are capable of synthesizing materials with high sensitivity to various wavelengths through molecular design than inorganic photoreceptors, are non-polluting, have superior productivity, are more economical, and are cheaper. It has the following characteristics and is currently undergoing active research and development. Significant improvements have also been made in terms of durability and sensitivity, which have traditionally been considered problems with organic photoreceptors, and some of these improvements have been put into practical use, and are now becoming the mainstay of electrophotographic photoreceptors.

OPC is usually used with a double layer structure consisting of a charge generation layer (abbreviated as CGL) that absorbs light and generates carriers and a charge transfer layer (abbreviated as CTL) that moves the generated carriers. It is being Filter materials (abbreviated as CGM) used in CGL include various perylene compounds,
Various organic materials have been investigated, such as various phthalocyanine compounds, thiapyrylium compounds, anthanthrone compounds, square IJIJium compounds, bisazo compounds, trisazo pigments, and azulenium dyes.

These are often pigments and are applied in particulate dispersed form in a polymeric binder.

On the other hand, materials used for CTL (abbreviated as CTM) include various hydrazone compounds, oxazole compounds,
Triphenylmethane compounds, arylamine compounds, etc. have been developed.

These materials can be formed on a substrate such as a drum or belt by a relatively simple coating method together with a binder polymer. Like this? Binder polymers used for the purpose of , C include polyester resins, polycarbonate resins, acrylic resins, acrylic-styrene resins, and the like. Generally, in a double layer structure, the CG layer is coated with a thickness of 1 to 2 microns or less for high sensitivity, while the CT layer is coated with a thickness of 10 to 20 microns or less.
Applied in micron thickness. At this time, for reasons such as strength and printing durability, the CG layer is usually formed on the substrate side and the CT layer is formed on the surface side. In such a configuration,
Since only CTMs that operate by the movement of holes have been put into practical use, their double-layer photoreceptors are of a negatively charged type.

Problems to be Solved by the Invention However, with such a negative charging method, there is a problem in that the image is easily affected by the surface of the substrate. for example,
When an aluminum drum is used, the influence of the drum surface is mainly due to impurities in the aluminum (particularly inorganic metal impurities) and surface irregularities.

These effects appear as white spots or black spots on the image, which are particularly noticeable under high temperature and high humidity conditions.

In order to solve these problems, methods such as using high-purity drum materials, giving the drum a mirror finish, or applying an undercoat have been considered. However, all of these methods lead to an increase in manufacturing costs. Although the method of providing an undercoat layer is the most excellent method among these methods, this method has the drawback of increasing residual potential.

The purpose of the present invention is to solve the drawbacks of such conventional photoreceptors,
It is an object of the present invention to provide a two-layer negatively charged photoreceptor that is improved so as to obtain high image quality.In particular, the present invention is characterized by a charge generation layer having an unprecedented composition. The purpose is to contain factors that degrade image quality such as white spots and black spots.

Means for Solving the Problems In order to achieve the above object, we investigated charge generation layers made of metal-free phthalocyanine (abbreviated as H,-PC) having various crystal structures and a binder polymer. As a result, a new method for producing a charge generation layer was established in which τ-type H2-PC is stirred with a solvent that dissolves the phthalocyanine and a binder polymer. By providing a charge transfer layer on the charge generation layer obtained by this method,
A photoreceptor with far superior image characteristics and sensitivity characteristics compared to conventional OPC has been obtained.

Function The photoreceptor of the present invention has an unprecedented configuration and can realize excellent characteristics as a photoreceptor, and can realize excellent image characteristics less affected by the substrate than conventional photoreceptors.

Example Examples of the present invention will be described in detail below.

Regarding H2-PC, Xerox Corporation has developed X-type H2-PC with excellent electrophotographic properties, and is conducting research on its synthesis method, the relationship between crystal type and electrophotographic properties, and structural analysis. (USP 3,357,989) Type X H2-
Pc is the β-type synthesized by a conventional method) (2-Pc is made into the α-form by treatment with sulfuric acid, and this is produced by ball milling for a long time. The crystals are clearly different from the conventional α-type and β-type. There is a crystalline phthalocyanine other than the α-type, β-type, and It is obtained by ball milling at ℃ for 20 hours.The present invention is carried out using τ type phthalocyanine among these phthalocyanines as a starting material.

FIG. 1 shows the absorption spectrum of τ-type phthalocyanine. Further, FIG. 2 shows the absorption spectrum of a photoreceptor produced by the method of the present invention. This absorption spectrum is clearly different from the absorption spectrum shown in Figure 1, especially at 650 nm16
The two absorption intensities at 90 nm have increased. This is believed to be based on molecularly dispersed phthalocyanine, indicating that it may be in a crystalline or amorphous state that has been altered by the method of the present invention.

Below, typical techniques of the present invention will be explained. As is clear from the above, the τ-type phthalocyanine is first placed in a reaction vessel together with a solvent capable of dissolving at least a portion of it, and a binder polymer if necessary, and thoroughly stirred and mixed. be done. The important point of the production method of the present invention is to use a soluble solvent and perform sufficient kneading. Generally, creating such a stable state requires one day or more using a normal stirring method.

As this reaction progresses, an increase in solution viscosity, the aforementioned change in absorption spectrum, and improvement in photosensitivity are observed.

FIG. 3 shows an X-ray diffraction diagram of a photoreceptor produced by the method of the present invention.

The degree, time, temperature, etc. of these kneading vary depending on the solvent used and the type of polymer. In order to obtain the most excellent properties as a photoreceptor, the treatment with this solvent may be insufficient or too advanced. To determine the appropriate degree of reaction, use the 75°, 9° X-ray pattern described above.
Diffraction line intensity ratio with around 1° (1,,,,/1.,,)
be between 1 and 01. Solvents suitable for this purpose include nitrobenzene, chlorobenzene, dichlorobenzene, dichloromethane, trichloroethylene, chlornaphthalene, methylnaphthalene, benzene, toluene,
xylene, tetrahydrofuran, cyclohexanone, 1
4-dioxane, N-methylpyrrolidone, carbon tetrachloride, bromobutane, ethylene chloride 1. ．． lcol, sulfolane,
Ethylene glycol monobutyl ether, acetoxyethoxyethane, pyridine, etc. can be mentioned.

As the binder polymer according to the present invention, the above-mentioned H2
- It is better to use a material that dissolves in a solvent that dissolves PC.

Polymers suitable for these purposes include polyester,
Polyvinyl acetate, polyvinyl chloride, polyvinylidene chloride, polycarbonate, polyvinyl butyral, polyvinyl acetoacetal, polystyrene, polyacrylonitrile, polymethyl methacrylate, polyacrylate,
Polycarbazole and their copolymers, poly(vinyl chloride/vinegar/vinyl alcohol), poly(vinyl chloride/vinyl acetate/maleic acid), poly(ethylene/vinyl acetate), poly(vinyl chloride/vinylidene chloride) ), melamine resins, alkyd resins, cellulose polymers, various siloxane polymers, etc. These polymers may be used alone or as a mixture of two or more. Of course, as mentioned earlier, by combining two or more types of solvents,
It is possible to dissolve H2-PC in one solvent and the binder polymer in another solvent.

Therefore, the binder polymer according to the present invention is not limited to the above-mentioned polymers. The optimal ratio of I-b-PC and binder polymer described above is between 2=1 and 1=10 in terms of weight ratio.

The photoreceptor coating liquid prepared by the above method is formed as a charge generation layer on a substrate by a conventional method.

The thickness of this layer is suitably between 0.1 and 5 microns.

In particular, a feature of the charge generation layer of the present invention is that it can work effectively even when it is thicker than conventional charge generation layers. There is a characteristic that it is difficult to receive.

Charge generation layers created using conventional techniques are susceptible to substrate effects. For example, when an aluminum drum is used, it is known that metal impurities contained in the aluminum and surface irregularities affect the image quality.

In particular, this effect often appears as black spots and white areas in the image quality under high temperature and high humidity conditions. However, the charge generation layer according to the present invention is characterized in that it is rarely affected by such effects. Of course, in the present invention, there is no problem in providing a blocking layer or a conductive layer between the substrate and the charge generation layer.

The conductive support serving as the substrate of the organic photoconductive layer is not particularly limited, and can be appropriately selected depending on the intended use. Specifically, metals such as aluminum, glass, paper, or plastics on which a conductive layer is formed by a method such as metal vapor deposition are preferably used.

Moreover, it can take various shapes such as a drum shape, a belt shape, and a sheet shape.

11. The photoreceptor of the present invention is produced by forming a charge transport layer on the charge generation layer. There are no particular limitations on this charge transfer layer, and charge transfer materials commonly used in charge transfer layers can be effectively used. Examples include various hydrazone compounds, oxazole compounds, triphenylmethane compounds, arylamine compounds, and the like. These charge transfer materials are formed on the charge generation layer together with a binder material by a conventional method such as a dipping method or a coating method.

The thickness of this charge transport layer is suitably between 5 and 40 microns, more preferably between 10 and 20 microns.

The sensitivity of the photoreceptor according to the present invention is 08~2.0111X,s
ec, and has higher sensitivity than conventional two-layer OPC.
Moreover, excellent images can be obtained. Also, the OP of the present invention
C exhibits excellent sensitivity to light in the wavelength range of 600 to 800 nm, and has a residual potential of 30 V or less.

The electrophotographic photoreceptor according to the present invention described above can be used in various recording systems such as copying machines, printers, facsimile machines, etc., and its uses are not limited in any way. Note that the electrophotographic photoreceptor according to the present invention is not limited to the above-mentioned example, and for example, if necessary, a surface protective layer made of an insulating resin may be further formed on the organic photoreceptor layer, or a photoreceptor layer may be formed on the photoreceptor layer. It is also possible to provide a blocking layer between the substrate and the substrate.

Next, the present invention will be explained in more detail by way of examples.

[Example 1] τ-type metal-free phthalocyanine (abbreviated as τPc, manufactured by Toyo Ink ■, Liophoton TH
P) ) and polyester (abbreviated as PET, manufactured by Toyobo ■)
Byron 200) was dissolved in tetrahydrofuran at a weight ratio of 1:2, thoroughly mixed, and then kneaded for 2 days. The obtained solution was applied onto an aluminum drum by the dip method and treated in vacuum at 120° C. for 1 hour to form a charge generation layer (thickness: 1 μm). The X-ray diffraction pattern of the photoreceptor thus obtained was measured using an X-ray diffractometer (RAD-B 5YSTEN, manufactured by Rigaku Denki) 13. The light source is CuKa line.

In another container, polycarbonate) (PC1 made by Mitsubishi Gas Chemical ■, Euhiron Z),! :4-dibenzylamino-2
-Methylbenzaldehyde-1-1-diphenylhydrazone (CTC191, manufactured by Anan Perfumery Industry Co., Ltd.) was dissolved in ethyl alcohol at a ratio of 1:2, stirred for 2 hours, and then coated on the charge generation layer. The thickness of the coating layer is 20 microns. After coating, it was dried at 60° C. for 20 minutes to produce a photoreceptor.

In addition, 1-phenyl-1,2,3,4-tetrahydroquinoline-6-carbaldehyde 11'-diphenyhydrazone (CTC-236 manufactured by Anan Fragrance Industry ■) was prepared in the same manner.
), and 9-ethylkerbazole 3-kerboxaldehyde-1-methyl-1 phenylhydrazone (CT-A
), a charge transfer layer was prepared using

Its photosensitive characteristics were evaluated using EPA-8100 manufactured by Kawaguchi Electric.
Using a type paper analyzer, irradiate white light from tungsten to measure the photosensitivity (half-reduced exposure amount, E
1/2), and the photosensitivity after 1000 repeated tests 14... was similarly measured. Furthermore, 400 to 100
The wavelength characteristics were measured in the range of 0 nm. Furthermore, the image quality was excellent even under high temperature and high humidity conditions, with almost no black spots or white spots observed.

In the X-ray diffraction diagram when the weight ratio of phthalocyanine and PET is 1 = 2, the diffraction line intensity ratio (1, , , / Ie, s) is 08, and the intensity ratio in the case of raw material X type H2-PC is 15 The intensity of the diffraction lines was significantly changed compared to the previous one. Table 1 shows the photosensitivity properties of each charge transfer agent.

Table 1 As is clear from these results, an excellent photoreceptor can be produced by the method of the present invention.

[Example 2] A 15″-τ type metal-free phthalocyanine (abbreviated as τPc) and an acrylic resin (abbreviated as PAc, manufactured by Dainippon Ink ■, Acridic) were dissolved in tetrahydrofuran at a weight ratio of 1:2,
After thorough mixing and kneading, the resulting solution was applied onto an aluminum drum by the dip method and treated in vacuum at 120° C. for 1 hour to form a charge generation layer (thickness: 2 μm).

Next, a charge transfer layer was formed in the same manner as in Example 1. The photosensitive characteristics of the photoreceptor obtained in this way were
Using an A-81000 paper analyzer, irradiate white light from tungsten to measure the photosensitivity due to negative charging (
The half-decrease exposure amount, E,/,) was measured, and the photosensitivity after 1000 repeated tests was also measured in the same manner. Furthermore, 400-1
The wavelength characteristics were measured in the range of 000 nm. The results are shown in Table 2. From this result, it was found that the method of the present invention can also be effectively used for polyacrylic acid resin. However, this photoreceptor showed excellent image quality characteristics, with almost no white spots or black spots appearing even under high temperature and high humidity conditions.

Table 2 [Comparative Example 1] For comparison, characteristics are shown for a case where n-butyl alcohol was used as a solvent for forming the charge generation layer using the same structure as in Example 2. n-butyl alcohol is PAc
The τ-type n*-pc does not dissolve. Therefore, in such a manufacturing method, it is considered that τ type H2-PC is mixed in the PAc in the form of particles. Next, the results are shown in Table 3. The photosensitivity was considerably worse than in Example 2, demonstrating the effectiveness of the present invention. In addition, image quality was evaluated using this photoreceptor, and the phenomenon of white spots and black spots became noticeable under high temperature and high humidity conditions.

Table 3 17Ba7 White light from tungsten was irradiated to measure the photosensitivity (half-decreased exposure amount, Ed/2), and the photosensitivity after 1000 repeated tests was also measured in the same manner. Furthermore, 400-1000
The wavelength characteristics in the nm range were measured. The obtained properties are shown in Table 4.

Table 4 [Example 3] τ-type metal-free phthalocyanine (abbreviated as τPc) and various binder polymers were mixed at a ratio of 1=1, dissolved in tetrahydrofuran, thoroughly mixed and kneaded, and the resulting solution was poured into an aluminum drum. Apply on top by dip method and apply in vacuum for 1
A charge generation layer (1 to 2 μm thick) was formed by processing at 20°C for 1 hour.
) was formed. For each sample, the reaction time was adjusted so that the intensity ratio by X-ray diffraction described above was between 0.8 and 0.5.

A charge transfer agent CTC-
A charge transfer layer was formed by using the method of Example 1 using No. 191.

The photosensitive characteristics of the obtained photoreceptor were measured using EPA-8 manufactured by Kawaguchi Denki ■.
Using a 100-inch paper analyzer, it is clear from the results that the method of the present invention can be applied to a wide range of polymers.

[Example 4] A continuous printing resistance test of the photoreceptor produced by the method of Example 1 was conducted. The test was conducted using A4 test paper, but 3
It was found that it operated stably in continuous tests of 10,000 sheets.

As described above, it has been found that the method of the present invention is superior to conventional photoreceptors in terms of printing durability.

Effects of the Invention As described above, by using the electrophotographic photoreceptor according to the present invention, it is possible to easily produce a photoreceptor that has higher sensitivity and excellent image quality characteristics than conventional photoreceptors. The photoreceptor of the present invention is expected to be applied as an electrophotographic photoreceptor to various recording devices.

[Brief explanation of the drawing]

Claims (2)

[Claims] (1) A charge generation layer formed by treating a τ-type metal-free phthalocyanine together with a solvent that dissolves the phthalocyanine and a binder polymer, and a charge transfer layer provided on the charge generation layer. A photoreceptor for electrophotography. (2) The weight ratio of metal-free phthalocyanine and binder polymer in the charge generation layer according to claim 1 is from 2:1 to 1:
Electrophotographic photoreceptor in the range of 10.