JPH0457059A - Electrophotographic photoreceptor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

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 that are highly sensitive to various wavelengths due to molecular design than inorganic photoreceptors, are non-polluting, have excellent productivity, are economical, and are inexpensive. It has the following characteristics and is currently undergoing active research and development. In addition, remarkable improvements have been made in terms of durability and sensitivity, which were conventionally considered problems of organic photoreceptors, and some of these improvements have been put into practical use, and they are now becoming the mainstay of photoreceptors for electrophotography.

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 Materials used for CGL (abbreviated as CGM) include various perylene compounds,
Various organic compounds such as various phthalocyanine compounds, thiapyrylium compounds, anthanthrone compounds, squarylium compounds, bisazo compounds, trisazo pigments, and azulenium dyes have been investigated. 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 are formed on a substrate such as a drum or belt by a relatively simple coating method together with a binder polymer.

Binder polymers used for this purpose include:
Examples include polyester resin, polycarbonate resin, acrylic resin, acrylic-styrene resin, and the like. Generally, in a double layer structure, the CG layer is coated to a thickness of 1 to 2 microns or less for high sensitivity, while the CT layer is coated to a thickness of 10 to 20 microns.・At this time, its strength, printing durability,
For these reasons, the CG layer is usually formed on the substrate side, and the CT layer is usually formed on the surface side. In such a configuration, CT
Since only those that operate by the movement of M or holes have been put into practical use, the double-layer photoreceptor is 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 influenced 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. but,
All of these methods lead to improved manufacturing costs. The method of providing an undercoat layer is perhaps the best method among these methods, but this method has the drawback of increasing residual potential.

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

5'\ ・Means for solving the problem In order to achieve the above objectives, we investigated charge generation layers consisting of metal-free phthalocyanine (abbreviated as H,-PC) with various crystal structures and a binder polymer. I did it. As a result, by stirring X-type (2-PC) with a solvent that dissolves the phthalocyanine and a binder polymer, a new charge-generating layer characterized by partially changing its crystal system was formed. By providing a charge transport layer on the charge generation layer, we have succeeded in inventing a photoreceptor that has far superior image characteristics and sensitivity characteristics compared to conventional OPC.

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 Embodiments of the present invention will be described below with reference to the drawings.

For H2-PC, Xerox or excellent electrophotography 6
・＼ / We have developed X-type H2-Pc with the following characteristics, and are conducting research on its synthesis method, the relationship between crystal type and electrophotographic properties, and structural analysis. (USP 3.357.989) X type H2P
c is produced by converting β-type H2-PC synthesized by a conventional method into α-type by treating with sulfuric acid and subjecting it to long-term ball milling. The crystal is clearly different from the conventional α-type and β-type. Figure 1 shows the Xa diffraction diagram of X-type H2-PC (
(Measurement using CuKα radiation). The diffraction line is 2θ=7.
4. 9.0. 15.1. 16.517.2. 2
0.1. 20.6. 20.7. 21.4. 22
．． 2. 23.8°27.2. 28.5. 30.3
Appears in °. The most intense diffraction line is the one near 75° (corresponding to the interplanar spacing d-11,8A), and if its intensity is 1, then the intensity of the diffraction line near 91° (corresponding to interplanar spacing d
= 9.8A) is 0.66. This strength ratio is hardly affected by the grain type of the crystal. Furthermore, the absorption spectrum of the X-type Hh-PC is clearly different from that of the α-type and β-type.

FIG. 2 shows the absorption spectrum of X-form H2-PC.

This difference in spectra due to the difference in crystals is due to the difference in the scooking state of the Pc molecule in the crystalline state, and it has been reported that the X-type H2-PC has a dimeric structure.

The present invention is carried out using X-type phthalocyanine as a starting material among five of these phthalocyanines. The X-type phthalocyanine is placed in a reaction vessel together with a solvent capable of dissolving a small amount (at least a part of it) and a binder polymer if necessary, and thoroughly stirred and mixed. This is an important point in the manufacturing method of the invention.Generally, in order to create such a stable crosstalk state, it is necessary to
It takes more than a day.

FIG. 3 shows an X-ray diffraction pattern of a photoreceptor obtained by such a method using X-type H2-PC as a starting material. This diffraction diagram is clearly different from the diffraction diagrams shown in FIGS. 1 and 2 shown above. It is also clearly different from the diffraction patterns of α-type and β-type H2-Pc. Here, the X type H2 in Figure 1
-Compare with the X-ray diffraction diagram of PC. In FIG. 3, compared to FIG. 1, the diffraction lines at 2θ-214° or more tend to disappear, and the diffraction lines around 165° tend to increase. The most remarkable change is the most characteristic 75° (d
= 11.8A) Of the two diffraction lines near 91° (d = 9.8A), only the diffraction line near 75° selectively disappears7? It is. This clearly indicates that a part of the crystal system of type X Hs-pc was changed to another crystal type 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 best characteristics as a photoreceptor,
It is not good if the treatment with this solvent is insufficient or progresses too much. To determine the appropriate degree of reaction, the diffraction line intensity ratio (x1.a/I9.B) between the 7, 5°, and 91° areas of the X-ray pattern mentioned above is between 1 and 01. things are desirable.

FIG. 4 shows an example of the absorption spectrum of a photoreceptor produced by the method of the present invention. This absorption spectrum is clearly different from the absorption spectrum in Figure 2, especially at 55Q nm,
The two absorption intensities at 59Q nm have increased. This is thought to be based on molecularly dispersed phthalocyanine, and shows that there are cases where the crystal system changed by the method of the present invention is in an amorphous state.

Solvents suitable for this purpose include nitrobenzene,
Chlorobenzene, dichlorobenzene, dichloromethane,
Trichlorethylene, chlornaphthalene, methylnaphthalene, benzene, toluene, xylene, tetrahydrofuran, cyclohexanone, 14-dioxane, N-methylpyrrolidone, carbon tetrachloride, bromobutane, ethylene glycol, sulfolane, ethylene glycol monobutyl ether, acetoxyethoxyethane, pyridine, etc. can be raised.

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 10-hone chloride/vinyl acetate/vinyl alcohol), poly(
Examples include vinyl chloride/vinyl acetate/maleic acid), poly(ethylene/vinyl acetate), poly(vinyl chloride/vinylidene chloride), melamine resin, alkyd resin, cellulose polymer, various siloxane polymers, and the like. These polymers may be used alone or as a mixture of two or more. Of course, as described above, it is possible to combine two or more types of solvents, so that one solvent dissolves I-h-PC and the other solvent dissolves the binder polymer.

Therefore, the binder polymer according to the present invention is not limited to the above-mentioned polymers. The optimal ratio of H2Pc and binder polymer mentioned above is from 2=1 to 1:
Between 10 and 10.

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

This thickness is suitably between 0.1 and 5 microns.

In particular, the charge generation layer of the present invention is characterized in that it can work effectively even when it is thicker than conventional charge generation layers. Furthermore, the charge generation layer produced by this method is characterized in that it is hardly affected by the substrate.

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.

This effect often appears as black spots or white spots in the image quality, especially 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, plastics, etc. with a conductive layer formed on the surface 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.

The photoreceptor of the present invention is produced by forming a charge transfer 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 from 5 to 40 microns, more preferably from 10 to 20 microns.

The sensitivity of the photoreceptor according to the present invention is 0.6 to 3,01 ux, 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 30V or less.

13. Impressions for electrophotography according to the invention described above
-7 The light object is, for example, a copier, a printer, a facsimile IJ, etc.
It can be used for various recording methods such as , etc., and its uses are not limited in any way. It should be noted that the electrophotographic photoreceptor according to the present invention is not limited to the above examples, and for example, if necessary, a surface protective layer made of an insulating resin may be further formed on the organic photoreceptor base, or a surface protection layer may be formed with the photosensitive layer. It is also possible to provide a blocking layer between the substrates.

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

[Example 1] X-type metal-free phthalocyanine (abbreviated as X-type H2-FC, manufactured by Dai Nippon Ink ■, Fastogen Blue)
n Blue) 81.20B) and polyester (PE
(abbreviated as T, manufactured by Toyobo ■, Byron 200) in a weight ratio of 1:
Dissolve step 2 in tetrahydrofuran, mix thoroughly, then add step 2
It was kneaded for several 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 (1 μm thick). The X-ray diffraction pattern of the photoconductor thus obtained was measured using an X-ray diffractometer (RA
DB 5YSTEN). The light source is Qbo alpha rays.

In a separate container, mix polycarbonate) (PC1 manufactured by Mitsubishi Gas Chemical Co., Ltd., Nipiron 2) and 4-dibe/dylamino-2-methylbenzaldehyde-1-1-diphenylhydrazone (manufactured by Anan Perfume Industry ■, CTC191) at a ratio of 1:2. The solution was dissolved in ethyl alcohol at a ratio of Created.

In addition, 1 phenyl-1,2,3,4 tetrahydroquinoline-6-carbaldehyde 1',1'
-Diphenylhydrazone (manufactured by Anan Kaori ■, CTC-2
36), and 9-ethylcarbazole-3-carboxaldehyde-1-methyl 1-phenylhydrazone (CT
-A) A charge transfer layer was prepared using .

The photosensitive characteristics were evaluated using EPA-8100 paper analyzer manufactured by Kawaguchi Electric.
−/ Exposure to white light to reduce photosensitivity due to negative charging (half exposure amount,
EI/2) was measured, and the photosensitivity after 1000 repeated tests was also measured in the same manner. Furthermore, wavelength characteristics in the range of 400 to 11,000 nm were measured. In addition, the image quality is high temperature,
It was excellent even under 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, , , / 1., ,) is 08, and the intensity ratio in the case of raw material X type H2-PC Compared to No. 15, the diffraction line intensity was significantly changed. 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] X-type metal-free phthalocyanine (X-type H, abbreviated as -PC, manufactured by Dai-Nippon Ink ■, Fastogen Blue)
n Blue) 8120B) and acrylic resin (PAc
(abbreviated as Dainippon Ink ■, acrylic resin) was dissolved in tetrahydrofuran at a weight ratio of 1:2, thoroughly mixed and kneaded, and the resulting solution was coated on an aluminum drum by the dip method, and in vacuum. A charge generation layer (thickness: 2 μm) was formed by processing at 120° C. for 1 hour.

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 evaluated using EP manufactured by J.
Using an A-8100 paper analyzer, white light from tungsten was irradiated to measure the photosensitivity due to negative charging (half exposure, El/+1), and the photosensitivity after 1000 repeated tests was also measured in the same way. . Furthermore, 400 to 10
The wavelength characteristics were measured in the range of 0.00 nm. Table 2 shows the results.
Shown below. From this result, it was found that the method of the present invention can be effectively used for polyacrylic acid resin. Furthermore, this photoreceptor exhibited excellent image quality characteristics, with almost no white spots or black spots appearing even under high temperature and high humidity conditions.

Table 2 18.\-7 Image quality was evaluated using this photoreceptor, and under high temperature and high humidity conditions, white spots and black spots became noticeable.

Table 3 [Comparative Example 1] For comparison, the characteristics are shown when the same structure as in Example 2 was used, but n-butyl alcohol was used as the solvent for forming the charge generation layer.

n-Butyl alcohol dissolves PAc, but forms X H2P.
c does not dissolve. Therefore, in such a manufacturing method, X-type H,-PC is mixed in the PAc in the form of particles, and it is considered that no crystal change occurs. 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, [Example 3]
l/-(Fastogen Blue) 8120B
) and various binder polymers at a ratio of 1=1, dissolved in tetrahydrofuran, thoroughly mixed and kneaded, the resulting solution was applied onto an aluminum drum by the dip method, and heated at 120°C in vacuum for 1 hour. Processing formed a charge generation layer (thickness 1-27+rn). In each test, the reaction time was adjusted so that the intensity ratio by X-ray diffraction as described above was between 0.8 and 0.5.

A charge transfer layer was formed on the thus obtained charge generation layer by the method of Example 1 using charge transfer agent 19/CTC-191. The photosensitive characteristics of the obtained photoreceptor were measured using Kawaguchi Denki E.
Using a PA-8100 paper analyzer, light sensitivity (half exposure, E1
/2), and the photosensitivity after 1000 repeated tests was also measured in the same manner. Furthermore, wavelength characteristics in the range of 400 to 11,000 nm were measured. The obtained properties are shown in Table 4.

Table 4 It can be applied to a wide range of polymers.

[Example 4] A test was conducted using A4 test paper for continuous printing resistance of the photoconductor prepared by the method of Example 1, and the photoconductor operated stably for a continuous test of 30,000 sheets. I found out that it does. In this way, it was found that the method of the present invention is superior in terms of photoreceptor and vinegar printing.

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) treating an X-type metal-free phthalocyanine with a solvent that dissolves the phthalocyanine and a binder polymer;
1. An electrophotographic photoreceptor comprising at least a two-layer structure including a charge generation layer whose crystal system has been partially changed, and a charge transfer layer provided on the charge generation layer. (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.