JPH03278064A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To enhance sensitivity and stability and to facilitate manufacture by forming the electrophotographic sensitive body composed of a binder polymer and 2 kinds of metal-phthalocycnines molecularly and granularly dispersed into the binder polymer. CONSTITUTION:The electrophotographic sensitive body is composed of the binder polymer and the 2 kinds of metal-phthalocycnines molecularly and granularly dispersed into the binder polymer, thus permitting the electrophotographic sensitive body to be simplified in the manufacturing process by using a positively chargeable single layer type organic photosensitive body, to be high in sensitivity, especially, in the wavelength region of 550 - 800nm, and especially excellent in characteristics in the case of positive charging, superior in stability and chargeability and also in printing resistance and heat resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an electrophotographic photoreceptor that is suitable for positive charging type electrophotography and is substantially composed of a charge generating agent and a binder polymer.

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. 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 materials are being investigated, such as metal-free phthalocyanines, various metal phthalocyanines, 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, which is compatible with semiconductor laser light (780,830 ns). Development of organic photoreceptors with unique characteristics is active. 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.

The binder polymer used for this important purpose is
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 to increase sensitivity, while the CT 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 CT layer on the surface side. In such a structure, only those in which the CTM is operated by the movement of holes have been put into practical use, so the dual layer photoreceptor has a negative charging method. There was a problem in that oxygen in the air turned 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, this two-layer method has problems such as (1) the manufacturing process becomes complicated, and (2) stability becomes a problem due to peeling between layers.

In order to solve this serious problem, development of positively charged organic photoreceptors is currently underway.

Conventionally, in order to achieve positive charging, (1) an inverted two-layer structure in which the CG L layer and CTL layer are configured in the opposite way to the negative charging case;
(2) A one-layer structure in which various CGM and CTM are dispersed in a binder polymer, and (3) A structure in which copper phthalocyanine is dispersed in particulate form in a binder have been studied. The inverted two-layer structure does not solve the same manufacturing process complexity and delamination problems as the negative charging method, and furthermore, the CGL layer, which inherently needs to be thin, is placed on the surface of the photoreceptor, which increases the durability. Problems include decreased printability and deterioration of life characteristics.

On the other hand, single-layer type photoreceptors aimed at positive charging were inferior to two-layer types in terms of sensitivity, charging characteristics (charging charges are 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, residual potential, and repetition stability.

As described above, all conventional oPCs have some kind of problem. Therefore, with a single layer type positively charged photoreceptor, 2
If high sensitivity, residual potential, and charging characteristics similar to those of the layered type can be realized, it would be considered an ideal photoreceptor.The purpose of the present invention is to solve the above-mentioned drawbacks of conventional OPC The object of the present invention is to provide a positively charged single-layer organic photoreceptor that has high performance, high sensitivity, and excellent durability. In particular, the problem to be solved by the present invention is to improve residual potential and repetition stability, which are disadvantages of conventional single-layer positively charged photoreceptors.

Means for Solving the Problems In order to solve the above problems, we investigated positively charged single-layer OPCs having various configurations. the result,
A single-layer O made of a combination of various metal phthalocyanines and an appropriate binder polymer as CGM.
This invention was completed by discovering that PC exhibits excellent photosensitivity when positively charged.

Function: The positively charged single-layer OPC according to the present invention has an unprecedented structure and can realize excellent characteristics as a photoreceptor, and has the following characteristics compared to conventional photoreceptors. .

■ Since it has a single layer structure, the manufacturing process is simple.

■Higher sensitivity than conventional single-layer OPC.

■ Shows excellent characteristics especially in the positive charging method.

■ Excellent stability and chargeability compared to conventional single-layer structure OPC.

(2) Shows excellent sensitivity in the wavelength range of 550 to 8 GOn-.

■ Since it has a single layer structure, it has excellent printing resistance.

■ It has excellent heat resistance because it does not contain CT agents that are sensitive to heat.

Example The present invention will be explained in detail below.

The gist of the present invention is an electrophotographic photoreceptor comprising a binder polymer, a metal phthalocyanine molecularly dispersed in the binder polymer, and a metal phthalocyanine dispersed in particulate form.

The metal phthalocyanine used in the present invention includes various crystalline copper phthalocyanine (abbreviated as CuPc), lead phthalocyanine (PbPc), and tin phthalocyanine (SnPc).
), silicon phthalocyanine (SiPc), vanadium phthalocyanine (■Pc), chloroaluminum phthalocyanine (AICIPc), titanyl phthalocyanine (
TiOPc), chloroindium phthalocyanine (I
ncIPc), chlorogallium phthalocyanine (Gac
IPc), etc. In particular, copper phthalocyanine exhibits excellent photosensitivity, and has T-type, ε-type, β-type,
α-type copper phthalocyanine exhibits particularly excellent properties.
Its sensitivity reaches 1.0 to 2.0 Iux, sec, which is significantly higher sensitivity than conventional single-layer OPC. Further, the OPC of the present invention exhibits excellent sensitivity to light in a wide wavelength range of 550 to 8 GOnw.

The first feature of the structure of the present invention is that it does not contain CTM, and this unique structure is different from conventional single-layer organic photoreceptors that are formed from a mixture of CGM and CTM. They are essentially different configurations. In this manner, the configuration of the present invention does not require CTM, which has been considered essential in the past.

This shows that the metal phthalocyanine added as CGM has charge transfer ability under certain conditions. We investigated various key conditions and found that the key charge transfer ability is due to the metal phthalocyanine molecularly dispersed in the binder polymer. On the other hand, the ability to generate charges is due to the metal phthalocyanine particles dispersed in the binder polymer. That is, the second feature of the present invention is that two types of metal phthalocyanine exist in the monolayer, one in molecular dispersion and one in particulate dispersion. This is essentially different from positively charged single-layer OPC in which particles of metal phthalocyanine are dispersed in a binder.

This organic photoreceptor with a solid structure has the following characteristics compared to conventional photoreceptors.

■ The manufacturing process is simple because it has a single layer structure.

■ Much higher sensitivity than conventional single-layer OPC.

■ Shows excellent characteristics especially in positive charging method.

■ Superior stability and charging performance compared to conventional single-layer OPC.

(2) Shows excellent photosensitivity over a wide range of 550 to 800 nm.

■ Since it has a single layer structure, it has excellent printing resistance.

■ Excellent heat resistance as it does not contain CTM, which is sensitive to heat.

As is clear from the above, in this case, at least a portion of the metal phthalocyanine must be dispersed in the polymer binder in molecular form. In order to achieve such molecular dispersion, it is necessary to dissolve the metal phthalocyanine in an appropriate solvent and to select a polymer that dissolves in this solvent as a binder. The metal phthalocyanine in the state of morphological dispersion and molecular dispersion must be realized in a monolayer.

In order to achieve this stable state, it is generally necessary to conduct sufficient cross-mixing with the binder resin. In the usual cross-mixing method, cross-mixing for one day or more is required to achieve stable molecular dispersion.

Solvents for dissolving metal phthalocyanine suitable for such purposes include nitromenzene, chlorobenzene, dichlorobenzene, dichloromethane, trichloroethylene, chlornaphthalene, Methylnaphthalene, benzene, toluene, xylene, tetrahydrofuran, cyclohexanone, 1,4-dioxane, N-methylpyrrolidone, carbon tetrachloride, bromobutane, ethylene glycol,
Sulfolane, ethylene glycol monobutyl ether,
Examples include acetoxyethoxyethane, pyridine, etc.

On the other hand, solvents such as acetone, cyclohexane, petroleum ether, nitromethane, methoxyethanol, acetonitrile, dimethyl sulfoxide, ethyl acetate, isopropyl alcohol, diethyl ether, methyl ethyl ketone, ethanol, hexane, propylene carbonate, butylamine, water, etc. are generally used for metal phthalocyanine. does not dissolve.

Therefore, in the present invention, these solvents cannot be used alone; when these solvents are used, they must be used in combination with the above-mentioned solvent that dissolves the metal phthalocyanine.

As the binder polymer used in the present invention, it is preferable to use one that dissolves in the solvent that dissolves the metal phthalocyanine listed above. Polymers suitable for these purposes include polyester, polyvinyl acetate, polyvinyl chloride, and polyvinyl chloride. vinylidene chloride, polycarbonate, polyvinyl butyral,
polyvinyl acetoacetal, polyvinyl formal,
Polyacrylonitrile, polymethyl methacrylate, polyacrylate, polyvinylcarbazole, and their copolymers, poly(vinyl chloride/vinyl acetate/vinyl alcohol), poly(vinyl chloride/vinyl acetate/maleic acid), poly(ethylene/ Examples include vinyl acetate), poly(vinyl chloride/vinylidene chloride), and cellulose polymers. These polymers may be used alone or as a mixture of two or more. Of course, as mentioned earlier, 2
It is possible to combine more than one type of solvent, dissolving the metal phthalocyanine with one solvent and dissolving the binder polymer with another solvent, so the binder polymer of the present invention is limited to the above-mentioned polymers. isn't it.

The optimal ratio of the metal phthalocyanine and the binder polymer described above is between 2:1 and 1:10 by weight.

If the amount of metal 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 300μ or more. On the other hand, if the amount of the binder polymer is greater than the above range, the photosensitivity will deteriorate.

CTMs that have been used in conventional single-layer OPCs include hydrazone compounds, oxazole compounds, triphenylmethane compounds, and allylamine compounds, but if these materials are added in an amount of 5% or more to CGM, they will be charged. stability becomes significantly worse. In other words, it can be seen that the conventional CTM has a bad influence on the configuration of the present invention and is essentially unnecessary.

The fact that this birch does not require CTM as a component of the present invention improves the heat resistance stability of the photoreceptor as a side effect. In conventional configurations, the heat resistance of the photoreceptor has been mainly determined by the heat resistance of the CTM. In the present invention, CTM is not included and the metal phthalocyanine is extremely heat resistant, so the heat resistance of the photoreceptor is actually determined by the heat resistance of the binder polymer. Therefore, in the case of polymers exposed to normal light, excellent heat resistance of 150° C. or higher is achieved.

With this key combination of materials, for example, a system using copper phthalocyanine and polyvinyl butyral at a weight ratio of 1:3 (see Example 1) has a half-reduced exposure sensitivity of 1.41 ux due to positive charging, and a high sensitivity of 5 ecO ( Charge potential 530V)
was realized, and the sensitivity at 800 n■ was 2.0 cd/μJ. On the other hand, the sensitivity due to negative charging is 201ux,
sec (charging potential of 150 V), and its characteristics were significantly inferior to those of positive charging. Moreover, this system was very stable, and the characteristics due to positive charging hardly changed even after repeated tests 1000 times. Furthermore, this photoreceptor exhibited excellent heat resistance, and its properties hardly changed even after treatment at 180° C. for 48 hours.

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.

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

Next, this explanation will be explained in more detail (examples and comparative examples will be explained together).

[Example 11] ε-type copper phthalocyanine (abbreviated as εCuPc, manufactured by Toyo Ink ■, Liopoton-ERPC) and polyvinyl butyral (abbreviated as PVB, S-LEC BM-2 manufactured by Suzui Kagaku Kogyo ■) were mixed in a mixed solvent of tetrahydrofuran and chlornaphthalene. After thorough mixing and kneading, the obtained solution was coated on an aluminum drum by the dip method and treated in vacuum at 150°C for 1 hour to form an OPC layer (thickness 10~
20 μm) was formed.

The photosensitive characteristics of the photoreceptor obtained in this way were
Using a PA-8100 paper analyzer, irradiate white light from tungsten to measure photosensitivity due to positive charging (
The half-life exposure amount (Elzx) 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 1000 n- were measured. Table 1 shows the properties when the weight ratio of εCuPc and polyvinyl butyral was varied.

As is clear from the results in the table, the ratio of CuPc to PVB is suitably between 2:1 and 1=10, and in this range of compositions, good charging and sensitivity characteristics can be obtained.

[Comparative Example 1] For comparison, the characteristics when the same configuration as in Example 1 is used but a mixed solvent of acetone and DMF is used as the solvent are shown. Acetone and DMF dissolve PVB but not CuPc, so this manufacturing method does not dissolve CuPc in PVB.
c is mixed in the form of particles, and CuP is dispersed in the form of molecules.
It is considered that c does not exist. The results are shown in Table 2.

Table 2 As shown in this result, the sensitivity due to positive charging, El/□, is significantly worse than the results in Table 1, and for the present invention, part of the XPc is dispersed in the binder polymer in molecular form. I understand that it is necessary to

[Example 2] The properties of γ-type, β-type, and α-type copper phthalocyanine were evaluated in the same manner as in Example 1. CuPc and PVB
Table 3 shows the sensitivity when the ratio of 1:3.

Table 3 From these results, T-type, β-type, α-type copper phthalocyanine ε
It has become clear that it exhibits excellent photosensitivity properties similar to type phthalocyanine.

[Example 31 Photoreceptors made of various metals Pc and PVB (weight ratio 1:3) were prepared in the same manner as in Example 1, and their photosensitive characteristics were measured. The obtained properties are shown in Table 4.

Table 4 As is clear from these results, a photoreceptor with excellent characteristics can be formed regardless of the type of metal when the metal Pc is dispersed in molecular form or in particulate form. I can do it.

[Example +1 CuPc and PVB of the photoconductor produced by the method of Example 1
A sample with a ratio of 1=4 was selected and a continuous printing resistance test was conducted. A test was conducted using A4 test paper, and it was found that it operated stably even after continuous testing of 30,000 sheets. It has been found that the method of the present invention is also superior in terms of rigidity 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 is a positively charged single-layer photoreceptor, and has higher sensitivity and excellent stability than conventional photoreceptors. Furthermore, it is characterized by an extremely easy manufacturing method, and is expected to be applied as an electrophotographic photoreceptor to various recording devices.

Claims (4)

[Claims] (1) An electrophotographic photoreceptor comprising a binder polymer, a metal phthalocyanine molecularly dispersed in the binder polymer, and a metal phthalocyanine dispersed in particulate form. (2) The metal phthalocyanine according to claim 1 is at least one selected from copper phthalocyanine, lead phthalocyanine, tin phthalocyanine, silicon phthalocyanine, vanadium phthalocyanine, chloroaluminum phthalocyanine, titanyl phthalocyanine, chloroindium phthalocyanine, and chlorogallium phthalocyanine. A photoreceptor for electrophotography, characterized in that it is of a type. (3) An electrophotographic photoreceptor in which the weight ratio of the metal phthalocyanine and binder polymer according to claim 1 is in the range of 2:1 to 1:10. (4) A photoreceptor for electrophotography, wherein the crystal type of the copper phthalocyanine according to claim 2 is at least one selected from γ type, ε type, β type, and α type.