JPH0365959A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain an electrophotographic sensitive body having high performance, high sensitivity, excellent durability, and excellent heat resistance by using at least one kind of a mixture composed of methyl phenyl siloxane and an org. high polymer, a mixture composed of dimethyl siloxane and org. high polymer, etc., as a binder. CONSTITUTION:The subject sensitive body consists of the phthalocyanine dispersed in the form of molecules or X type or tau type phthalocyanine dispersed in the form of particles into the high polymer binder. The methyl phenyl siloxane or dimethyl siloxane is used as the binder. The dimethyl siloxane alone hardly forms a good film and is, therefore, used generally by being crosslinked or in combination with the org. high polymer. While the methyl phenyl siloxane alone has excellent film formability, the methyl phenyl siloxane is used in combination with the various org. high polymers in order to improve the film formability thereof. Thus, the electrophotographic sensitive body which provides the excellent characteristics and has the excellent durability and heat resistance is obtd.

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) have the following advantages: compared to inorganic photoreceptors, materials with high sensitivity to various wavelengths can be synthesized through molecular design, are non-polluting, are superior in productivity and economy, 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.

OPOs are usually used with a double layer structure consisting of a charge generation layer (OGL) that absorbs light and generates carriers and a charge transfer layer (OTL) that moves the generated carriers. It is being Materials used for OGL (abbreviated as CGM) include various perylene compounds,
Various organic materials are being investigated, such as various phthalocyanine compounds, thiapyrylium compounds, anthanthrone compounds, squarylium compounds, bisazo compounds, trisazo pigments, and azulenium dyes.

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.

Furthermore, in recent years there has been an increasing desire to use these organic photoreceptors as photoreceptors for digital recording in laser printers and other devices in the near-infrared region that corresponds to semiconductor laser light (780-830 nm). Organic photoreceptors with sensitive characteristics are being actively developed. As a photoreceptor in such a region, an organic photoreceptor has an advantage over an inorganic photoreceptor in terms of sensitivity.

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 00 layer is coated to a thickness of several microns for high sensitivity, while the 07 layer is coated to a thickness of several tens of microns. At this time, due to its strength, printing durability, etc.
The layer is usually formed on the substrate side, and the 07 layer is formed on the surface side. In such a configuration, only those operated by the movement of holes in the OTM have been put into practical use, so the double layer photoreceptor is of a negative charging type.

Problems to be Solved by the Invention However, such a negative charging method has a problem in that oxygen in the air turns into ozone due to the negative charge used for charging. Ozone is not only harmful to the human body, but also often reacts with photoreceptors, shortening the life of the photoreceptor.

Furthermore, such a two-layer system has problems such as (1) the manufacturing process becomes complicated, and (2) stability becomes a problem due to interlayer peeling and the like.

In order to solve these problems, positive charging type organic photoreceptors are currently being developed.

Conventionally, in order to achieve positive charging, (1) OGL layer and CT
An inverted two-layer structure in which the L layer has a configuration opposite to that of the negatively charged case, and (
2) One-layer structures in which various OGM and OTM are dispersed in a binder polymer have been studied. The inverted two-layer structure does not solve the same problems of manufacturing process complexity and delamination as in the case of the negative charging method.

Furthermore, problems arise in that the OGL layer, which essentially needs to be made thin, is placed on the surface of the photoreceptor, resulting in a decrease in printing resistance and deterioration in life characteristics.

On the other hand, the single-layer type photoreceptor with a positive charge of 0 was inferior to the two-layer type in terms of sensitivity, charging characteristics (charge for charging is difficult to carry), and residual potential. The reason for the poor sensitivity was that charge generation and movement occurred randomly within the single layer, and the problems with single-layer photoreceptors were sensitivity, charging characteristics, and residual potential.

As described above, all conventional OPCs have some kind of problem. Therefore, with a single layer type positively charged photoreceptor, 2
If it can achieve the same high sensitivity, residual potential, and charging characteristics as the layered type, it is considered to be an ideal photoreceptor.

The purpose of the present invention is to solve the above-mentioned drawbacks of conventional OPOs, and to provide an electrophotographic photoreceptor that has high performance, high sensitivity, excellent durability, and extremely high heat resistance. be.

Means for Solving the Problems In order to solve the above problems, we investigated positively charged single-layer organic photoreceptors having various configurations. As a result, it was discovered that an organic photoreceptor made of a combination of X-type phthalocyanine or τ-type phthalocyanine as OGM and a suitable binder polymer exhibits excellent photosensitivity in a positive charging system. We conducted further studies and discovered that durability, heat resistance, and chargeability can be improved by using a specific binder polymer, and have come to realize the present invention.

The first feature of the structure of the present invention is that it does not contain CTM, and this structure is different from conventional single-layer organic photoreceptors that are formed from a mixture of CGM and CTM. They are essentially different configurations. The fact that OTM, which was traditionally thought to be essential, is not required means that the X-type or τ-type phthalocyanine added as OGM has the ability to transfer charges under certain conditions, and that Unlike OTM, it has the ability to move negative charges,
It shows. We investigated various such conditions and clarified that such negative charge transfer ability is due to X-type or τ-type phthalocyanine molecularly dispersed in the ζ-inder polymer. On the other hand, the ability to generate charges is due to the X-type or τ-type phthalocyanine dispersed in particles in the binder polymer. That is, the second feature of the present invention is that two types of X-type or τ-type phthalocyanine exist in the monolayer, one dispersed in molecular form and the other dispersed in particulate form.

As is clear from the above, in this case, at least a portion of the X-type or τ-type phthalocyanine must be dispersed in molecular form in the polymer binder. In order to realize such molecular dispersion, it is necessary to dissolve the X-type or τ-type phthalocyanine in a suitable solvent and to select a polymer that is soluble in this solvent as a binder.

Solvents that dissolve X-type or τ-type phthalocyanine suitable for such purposes include nitrobenzene, chlorobenzene, dichlorobenzene, dichloromethane, trichloroethylene, chlornaphthalene, methylnaphthalene, benzene, toluene, xylene, tetrahydrofuran, cyclohexanone, Examples include 1,4-dioxane, N-methylpyrrolidone, carbon tetrachloride, bromobutane, ethylene glycol, sulfolane, ethylene glycol monobutyl ether, acetoxyethoxyethane, pyridine, and the like.

On the other hand, solvents such as acetone, cyclohexane, petroleum ether, nitromethane, methoxyethanol, dimethylformamide, dimethylacetamide, acetonitrile, dimethylsulfoxide, ethyl acetate, isopropyl alcohol, diethyl ether, methyl ethyl ketone, ethanol, hexane, propylene carbonate, butylamine, water, etc. Does not dissolve X-type or τ-type phthalocyanine.

Therefore, in the present invention, these solvents cannot be used alone. When using these solvents, it is necessary to use them in combination with the above-mentioned solvent that dissolves the X-type or -type phthalocyanine.

Binder polymers used for this purpose include:
Polyester, polyvinyl acetate, polyvinyl chloride, polyvinylidene chloride, polycarbonate, polyvinyl butyral, polyvinyl acetoacetal, polyvinyl formal, polyacrylonitrile, polymethyl methacrylate, polyacrylate, and copolymers thereof, poly(
vinyl chloride/vinyl acetate/vinyl alcohol), poly(
Examples include vinyl chloride/vinyl acetate/maleic acid), poly(ethylene/vinyl acetate), poly(vinyl chloride/vinylidene chloride), and cellulose polymers.

The OPO prepared by such a method had significantly higher sensitivity and excellent durability than conventional positively charged OPO. However, this OPC has the disadvantage that the charging potential decreases with repeated charging tests, and some polymers also have problems with peeling from the substrate and deterioration of printing durability due to the softness of the binder polymer. .

Therefore, in order to solve the above problems, we developed a binder resin for a photoreceptor that is optimal for the configuration of the present invention. As a result, a novel high-performance polymer binder was discovered and the present invention was completed. The polymer binder according to the present invention is methylphenylsiloxane, dimethylsiloxane, methylphenylsiloxane-organic polymer copolymer,
It is a dimethylsiloxane-organic polymer copolymer or a mixture.

As a result of various studies, it was found that this binder polymer has the effect of improving charging characteristics and reducing residual potential compared to ordinary binder polymers. Furthermore, since this binder polymer is tough and has excellent heat resistance, by using it, an OPC with excellent durability and heat resistance can be obtained.

Methylphenylsiloxane or dimethylsiloxane is used as the binder in this invention. Since dimethylsiloxane is difficult to form a good film when used alone, it is generally used after crosslinking or in combination with an organic polymer. Although methylphenylsiloxane has excellent film properties by itself, it is used in combination with various organic polymers to further improve the film properties. For such a composite purpose, a low polymerization type methylphenyl silicone varnish having a silanol type or methoxy group at the terminal is effectively used.

Examples of organic polymers used in combination with the above siloxane include alkyd resin, acrylic resin, carbonate resin, epoxy resin, melamine formaldehyde resin, urea formaldehyde resin, dioctyl phthalate, ethyl cellulose, phenol resin, rosin-modified phenol resin, and styrenated alkyd. It is preferable to use at least one selected from resin, polyester resin, epoxy ester resin, polyimide resin, etc., especially alkyd resin, acrylic resin,
Carbonate resin, polyester resin, and polyimide resin are well used for this purpose.

The optimal ratio of the X-type or τ-type phthalocyanine and the siloxane polymer described above is from 1:1 to 1=10 by weight.
It is between. If the amount of phthalocyanine is greater than this range, the photosensitivity properties (potential attenuation properties due to light) will be excellent, but the charging properties will deteriorate and it will generally be difficult to apply a potential of 300 V or more. On the other hand, if the amount of the binder polymer is greater than the above range, the photosensitivity will deteriorate.

By combining such materials, for example, in a system using X-type phthalocyanine and methylphenylsiloxane at a χ weight ratio of 1:3 (see Example 1), the half-reduced exposure sensitivity due to positive charging is 0.81 ux, sec. High sensitivity (charged potential 7
00 v) was achieved, and the sensitivity at 800 nm was 2.3
It was ci/μJ. On the other hand, the sensitivity due to negative charging was 221 ux, seC (charging potential 110 V), and its characteristics were significantly inferior to those with positive charging. Moreover, this system was very stable, and the characteristics due to positive charging hardly changed even after 5000 repeated tests. Furthermore, this photoreceptor exhibited excellent heat resistance, and its properties hardly changed even after treatment at 200° C. for 48 hours.

Note that OGM dispersed in particulate form, which is a component of the present invention, is not necessarily limited to X-type or τ-type phthalocyanine, and is used in ordinary photoreceptors (3GM can be effectively used. X-shaped or τ
It may be dispersed in a single layer together with type phthalocyanine, or it may be provided as a separate layer on the substrate as a charge generation layer.

In the latter case, the photoreceptor has a two-layer structure.

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.

In the present invention described above, the electrophotographic photoreceptor 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 includes:
It is not limited to the above example; for example, if necessary, a surface protection layer made of an insulating resin may be further formed on the organic photoreceptor layer, or a blocking layer may be provided between the photoreceptor layer and the substrate. You can do it too.

Function: The positively charged single-layer OPO according to the present invention has an unprecedented structure, can realize excellent characteristics as a photoreceptor, and is superior in durability and heat resistance than conventional photoreceptors.

Example Next, the present invention will be further explained by showing examples.

<Example 1> xmm gold metal phthalocyanine
e) 8120B) and methylphenylsiloxane (manufactured by Toshiba Silicone ■, silicone varnish 5TR11γ) solution (
After dissolving THF/xylene y/n-butanol = 2/1/1) and thoroughly mixing and kneading, the resulting solution was applied onto an aluminum drum by the dip method and heated at 160°C in vacuum.
was treated for 1 hour to form an OPC layer (thickness: 10 to 20 μm).

The photosensitive characteristics of the photoreceptor obtained in this way were
Using an iPA-8100 paper analyzer, irradiate white light from tungsten to measure the photosensitivity due to positive charging (half-reduction exposure, E 1/2), and measure the photosensitivity after 6000 repeated tests in the same way. did. Furthermore, 40
The wavelength characteristics were measured in the range of 0 to 11000n. Table 1 shows the properties when the weight ratio of X-type phthalocyanine and 5TR117 was varied.

As is clear from this result, XPc and 5TR117
The appropriate weight ratio is between 1:1 and 1=10, and a boat bottom within this range can provide good charging characteristics and sensitivity characteristics.

<Example 2> τ-type metal-free phthalocyanine (abbreviated as τPc, manufactured by Toyo Ink ■, Liophoton THP)
) and 5TR117 were dissolved by the method of Example 1, and
After mixing and kneading, the obtained solution was applied onto an aluminum drum by the dip method and treated in vacuum at 160° C. for 1 hour to form a 020 layer (thickness: 10 to 20 μm). The photosensitive characteristics of the photoreceptor thus obtained were evaluated by the method of Example 1. Table 2 shows the properties when the weight ratio of τ-type phthalocyanine and 5TR117 was varied.

From these results, it has become clear that τ-type phthalocyanine exhibits excellent photosensitivity characteristics similar to X-type phthalocyanine.

<Example 3> X-type metal-free phthalocyanine (abbreviated as XPc, manufactured by Dainippon Ink ■, Fastogen Blue)
e) Characteristics of 8120B) and various methylphenylsiloxane-organic polymer copolymers and dimethylsiloxane-organic polymer copolymers were evaluated when they were used as binder resins. XPc and various siloxanes were mixed at a ratio of 1:4, dissolved in a mixed solvent of THF and xylene, and thoroughly mixed and kneaded.The resulting solution was coated on an aluminum drum by the dip method and heated at 160°C in vacuum. The treatment was continued for 1 hour to form an OF2 layer (thickness 10-20 μm).

The photosensitive characteristics of the photoreceptor obtained in this way were determined by
Using a PA-8100 paper analyzer, irradiate white light from tungsten to measure photosensitivity due to positive charging (
The half-life exposure amount (E 1/2 ) was measured, and the photosensitivity after repeated testing 500 times was also measured. The results are shown in Table 3.

Table 3 From these results, it can be seen that the binder polymer according to the present invention exhibits excellent photosensitive characteristics in the positive charging system and also has excellent repeatability stability.

Note that the siloxane and the organic polymer do not necessarily have to be made into a copolymer, and the same effect can be obtained by simply mixing them or making them into a composite.

However, in this case, the sensitivity and repetition stability generally tend to be worse than when a copolymer is used.

<Example 4> Of the photoreceptors prepared by the method of Example 1, XPc and 5TR1
17 ratio of 1:4 was selected, and continuous heat resistance tests and printing resistance tests were conducted. Heat resistance test result 200℃,
The properties did not change at all after 48 hours of testing. In addition, in a printability test using A4 test paper, it was found that the printer operated stably over a continuous test of 50,000 sheets. As described above, it has been found that the method of the present invention is superior in terms of printing durability compared to conventional two-layer type photoreceptors or single-layer type photoreceptors.

Effects of the Invention As described above, the electrophotographic photoreceptor according to the present invention uses polysiloxane as a binder polymer, and in this binder polymer, phthalocyanine dispersed in molecular form and phthalocyanine dispersed in particle form are used. It is a positively charged photoreceptor made of X-type 7 thalocyanine or τ-type phthalocyanine, and has higher sensitivity and excellent stability than conventional photoreceptors, and its manufacturing method is also significantly faster. It has the characteristic of being easy to use, and is expected to be applied to various recording devices as an electrophotographic photoreceptor.

Claims (3)

[Claims] (1) Consisting of phthalocyanine molecularly dispersed in a binder polymer, X-type phthalocyanine or τ-type phthalocyanine dispersed in particulate form, and as a binder, methylphenylsiloxane, dimethylsiloxane, methylphenylsiloxane-organic polymer copolymer, It is characterized in that at least one type selected from a dimethylsiloxane-organic polymer copolymer, a mixture of methylphenylsiloxane and an organic polymer, and a mixture of dimethylsiloxane and an organic polymer is used. Photoreceptor for electrophotography. (2) The organic polymer according to claim 1 is an alkyd resin,
An electrophotographic photoreceptor that is at least one selected from acrylic resin, carbonate resin, epoxy resin, polyester resin, and polyimide resin. (3) An electrophotographic photoreceptor in which the weight ratio of the X-type phthalocyanine or τ-type phthalocyanine according to claim 1 and the binder polymer is in the range of 1:1 to 1:10.