JPH0519495A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To improve the sensitivity, stability, printing resistance, etc., of an org. electrophotographic sensitive body used for a printer or a copying machine. CONSTITUTION:This electrophotographic sensitive body contains X- phthalocyanine dispersed in a high molecular compd. represented by the formula as a polymer binder. In the formula, at least one of X1 and X2 is Br and at least one of benzene rings has Br substd. for H at <=100% rate of substitution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photosensitive member suitable for a positive charging system used in an electrophotographic system including processes such as charging, exposing, developing and discharging.

[0002]

2. Description of the Related Art As is well known, in an electrophotographic photoreceptor using a photoconductive substance as a photosensitive material, a layer containing a photoconductor is formed on a conductive support to form an electrophotographic photoreceptor. Although constituted, as the photoconductive substance used for such a purpose, selenium, zinc oxide, titanium oxide, an inorganic photoconductor such as cadmium sulfide, or a phthalocyanine pigment,
Organic photoconductors such as disazo pigments are known. Among these electrophotographic photoreceptors, the inorganic photoreceptor having an inorganic photoconductor is not always satisfactory in terms of properties such as thermal stability, durability, etc., and since it has toxicity, in terms of production, There was also a problem in handling.

In addition, an organic photoconductor (OPC) having an organic photoconductor is capable of synthesizing a material having high sensitivity to various wavelengths by a molecular design as compared with an inorganic photoconductor, that it is non-polluting, and productivity and economical efficiency. Since it has advantages such as superiority and low cost, active research and development are currently being conducted.

That is, the organic photoreceptor is basically based on a double layer structure of a charge generation layer (CGL) that absorbs light to generate carriers and a charge transfer layer (CTL) that moves the generated carriers. Therefore, high sensitivity has been achieved. Further, the durability and sensitivity have been remarkably improved in the past, which have been problems of the organic photoconductor, and some of them have been put into practical use, and are now becoming the main force of the electrophotographic photoconductor.

By the way, in the organic photoreceptor having a double layer structure,
The charge generation layer is applied with a thickness of several microns and the charge transfer layer is applied with a thickness of several tens of microns for higher sensitivity, but due to its strength, printing durability, etc., the charge generation layer is It is usually formed on the substrate side, and the charge transfer layer is usually formed on the surface side. Conventionally, in such an organic photoconductor having a double-layer structure, only the one in which the charge transfer layer operates by the movement of holes is put into practical use, and therefore the double-layer photoconductor is of a negative charging type.

[0006]

However, in such a negative charging system, since ozone is generated by the negative charge, the ozone accelerates the oxidative deterioration of the organic photoconductor, so that the life of the organic photoconductor is increased. I have a problem. And
The above-mentioned negative charging type organic photoreceptor has problems in its photosensitivity and printability.

Therefore, in order to solve the problem of the organic photoreceptor of the negative charging system, the development of the organic photoreceptor of the positive charging system is now under way.

By the way, conventionally, in order to realize positive charging, (1) an inverse two-layer structure organic photoconductor in which the charge generation layer and the charge transfer layer are arranged in an inverse relationship to the case of negative charging, (2) various types A single-layer organic photoreceptor in which the charge generation layer and the charge transfer layer are dispersed in a binder polymer, and a single-layer organic photoreceptor in which (3) copper phthalocyanine is dispersed in the polymer are under study.

However, in the inverse two-layer structure according to the method (1), it is impossible to solve the same complication of the manufacturing process as in the case of the negative charging method and the problem of delamination, and it is essentially necessary to reduce the thickness. When a certain charge generation layer is placed on the surface of the photoconductor, the print resistance due to mechanical fatigue such as abrasion becomes a problem, and none of them has been put to practical use.

Further, in the case of the single-layer type positive charging photoreceptor according to the above-mentioned methods (2) and (3), the sensitivity, residual potential, and The charging property is inferior, and in particular, there is a defect that the charging property deteriorates after repeated use, that is, the charging potential gradually decreases. However, these single-layer type electrophotographic photoconductors do not inherently have a problem of print resistance due to mechanical fatigue such as abrasion due to paper or cleaning process which has been a problem in the reverse layer type positive charging method. There is an advantage called. In other words, in the case of a single-layer type photoconductor, mechanical fatigue such as abrasion is considered to have no effect on photosensitivity even if abrasion occurs if the charge generation layer and the charge transfer layer in the layer are evenly dispersed. Because.

By the way, as an organic photoreceptor, a photoconductive resin typified by polyvinylcarbazole (PVK), PVK-2,4,7-trinitrofluorenone (T
Charge transfer complex type represented by NF), phthalocyanine-
BACKGROUND ART Pigment dispersion type typified by a binder, function-separated type photoconductor in which a charge generating substance and a charge transporting substance are used in combination are known.

In the process of manufacturing these photoconductors, generally, when the photoconductive layer, the charge generation layer and the charge transport layer are formed, a mixing and dispersing treatment with a binder polymer is carried out. In the step, a ball mill, an attritor, a sand mill and the like are used to previously dissolve or disperse an appropriate amount of a photoconductive substance, a charge generating substance, a charge transporting substance and a resin together in a solvent. In this case, when the solution is homogeneously dissolved, the quality of the solution or the quality of the solute is small, but in the case of using a pigment, there is a problem that the properties of the pigment change depending on the dispersion treatment conditions. For example, depending on the type of solvent or binder-polymer, dispersion method, dispersion treatment time, solution holding time, etc., the crystal form of the pigment may change or some dissolution phenomenon may occur, resulting in changes in the characteristics of the pigment. Of.

An object of the present invention is to solve the problems of the conventional single-layer type photoreceptor as described above, and to provide a positively charged single-layer type organic photoreceptor having high performance, excellent printing durability and high sensitivity. To obtain a photoconductor for electrophotography.

[0014]

To achieve this object, in the electrophotographic photoreceptor of the present invention, an X-type phthalocyanine is a polymer compound represented by the following general formula (Formula 2) as a binder polymer. It is characterized by being dispersed in.

[0015]

[Chemical 2]

That is, the present inventors have examined positively charged single-layer type organic photoconductors having various constitutions and a processing method thereof in order to solve the conventional problems. As a result, a single-layer type organic photoconductor using X-type phthalocyanine or τ-type phthalocyanine as a charge generation layer and combining this with an appropriate binder polymer exhibits excellent photosensitivity in the positive charging system. Discovered (Japanese Patent Application No. 1-181044)
No.).

The sensitivity of the single-layer type organic photoconductor is significantly higher than that of the conventional single-layer type organic photoconductor, and the sensitivity is 0.5 to 2.
It reaches 0 lux.sec and shows excellent sensitivity to light in a wide wavelength range of 550 to 800 nm. By the way, the single-layer organic photoreceptor is characterized by not containing a charge transfer layer,
This structure is essentially different from the fact that the conventional single-layer type organic photoreceptor is formed of a mixture of a charge generation layer and a charge transfer layer.

Further, the organic photoconductor has the following features as compared with the conventional organic photoconductor. (1) The single-layer structure simplifies the manufacturing process. (2) The sensitivity is far higher than that of the conventional single-layer organic photoconductor. (3) Particularly, the positive charging method shows excellent characteristics. (4) It has excellent stability and chargeability as compared with the conventional single-layer structure organic photoreceptor. (5) It exhibits excellent photosensitivity in a wide range of 550 to 800 nm. (6) Since it has a single layer structure, it is excellent against mechanical fatigue. (7) It has excellent heat resistance because it does not contain a charge transfer layer that is weak against heat.

However, as a result of subsequent examinations, it was found that this organic photoreceptor also has a problem in terms of repeated stability, particularly charging characteristics. That is, when a repeated test was performed using this electrophotographic photoreceptor, fatigue, which is considered to be chemical fatigue due to light and ozone, was observed in electrification voltage, dark decay, and sensitivity in 10,000 or more repeated tests. Was done.

The inventors of the present invention have studied the binder-polymer which constitutes the organic photoreceptor in order to improve this fatigue and further improve the above-mentioned characteristics. It was found that the degree of fatigue and the optical characteristics greatly differ depending on the type. That is, in the case of a certain type of high molecular compound, the electrification voltage, dark decay, and sensitivity are very good, and the same photosensitive characteristics as before the repeated test are obtained.

The characteristic structure of this polymer compound is a copolymer structure represented by the above general formula (Formula 2). This polymer compound has high heat resistance, is easily dissolved in many solvents, and has good dispersibility with a pigment or the like. Generally speaking, the smaller the number of Br group units, the higher the solubility in many organic solvents. Therefore, there is little restriction on the selection of the solvent during coating.

By using such a polymer compound as a binder in combination with X-type phthalocyanine, remarkably good properties were obtained. The dispersion treatment is carried out using a solvent before coating, and a marked change in the characteristics of the solution is observed during this treatment. That is, a part of the X-type phthalocyanine is solubilized and at the same time made into fine particles.
The viscosity increased with time, and the light absorption coefficient of the formed film also increased. Although the cause of this is unknown, it is considered that a new interaction has occurred between the solubilized X-type phthalocyanine molecule and the binder-polymer. This dispersion and mixing can be performed by a ball mill or sand gland method, but the film formation is not limited to a special method, and a bar coater, a calendar coater, a spin coater can be used. -, Blade coater, dip coater, gravure coater, etc., and the formed film is extremely dense and hard and has high heat resistance.

[0023]

Since the positively charged single-layer type organic photoconductor according to the present invention has the above-mentioned constitution especially for the binder polymer, it has the following excellent characteristics as an organic photoconductor as compared with the conventional organic photoconductor. realizable. (1) The single-layer structure simplifies the manufacturing process. (2) The sensitivity is far higher than that of the conventional single-layer organic photoconductor. (3) Particularly, the positive charging method shows excellent characteristics. (4) It has excellent stability and chargeability as compared with the conventional single-layer structure organic photoreceptor. (5) It exhibits excellent sensitivity in the wavelength range of 550 to 800 nm. (6) Since it has a single-layer structure, it has excellent printing resistance. (7) It has excellent heat resistance because it does not contain a charge transfer layer that is weak against heat.

Further, by using the binder polymer of the present invention, since the electrification voltage, the dark decay, and the sensitivity change with time due to repeated use are small, the life as an organic photoreceptor can be extended.

[0025]

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

EXAMPLE 1 An example of the present invention will be described together with a comparative example. X-type metal-free phthalocyanine (XP)
c, Dainippon Ink and Co., Ltd., Fast Gen Blue (Fasto
gen Blue) 8120B) and the polymer compound having the structure represented by the general formula (Formula 2) were dissolved in tetrahydrofuran at a ratio of 1: 4. The compositional ratio of this polymer compound was m: n = 1: 3, and the molecular weight was about 40,000 Mw. The solution after being dispersed and mixed by a ball mill method is applied on an aluminum drum plate by a dip method and treated in air at 150 ° C. for 1 hour to obtain an organic photoreceptor layer (thickness 1
5-20 μm) was formed.

The photosensitivity of the thus obtained organic photoconductor was measured using a EPA-8100 type paper analyzer manufactured by Kawaguchi Denki Co., Ltd., by irradiating it with white light from tungsten to obtain photosensitivity (half-exposure amount, E1) due to positive charging. / 2) is measured,
The photosensitivity after 000 repeated tests was measured in the same manner.
After the measurement was performed 10,000 times, the measurement atmosphere was adjusted to an ozone concentration of about 3 ppm. The measurement results are shown in (Table 1). As is clear from this result, no change was observed in the characteristics of charge position and photosensitivity. As a comparative example, polymethacrylate and polystyrene were used. Comparing the characteristics with the resin of the example, the charge potential was reduced by about 10%, and the dark decay rate of the potential, the sensitivity, and the change with time of the charged voltage were also large.

[0028]

[Table 1]

(Example 2) An organic photosensitizer was prepared in the same manner as in Example 1 except that X-type metal-free phthalocyanine and a polymer compound represented by the general formula (Formula 2) having a composition ratio m: n of 1: 1 were used. Created the body. A mixed solvent of methyl ethyl ketone and cyclohexanone was used as the solvent. The solution after mixing in a ratio of 1: 5 and thoroughly mixed and kneaded is applied on an aluminum plate by a dip method and treated in air at 170 ° C. for 1 hour to obtain an organic photoreceptor layer (thickness 15 to 20 μm) was formed.

The photosensitivity of the thus obtained organic photoconductor was measured by illuminating it with white light of tungsten using an EPA-8100 type paper analyzer manufactured by Kawaguchi Denki Co., Ltd. to obtain photosensitivity (half exposure amount, E1 / 2) is measured and 200
The photosensitivity after the repeated test of 00 times was similarly measured.
Further, the photosensitivity of the photoconductor was measured in an atmosphere of ozone having a concentration of 5 ppm, and the results are shown in (Table 2). As is clear from this result, by using the binder polymer, good charging characteristics, sensitivity characteristics, and ozone resistance can be obtained.

[0031]

[Table 2]

Example 3 The X-type metal-free phthalocyanine of Example 2 and the polymer compound were mixed and dispersed at a ratio of 1: 5 using a cyclohexanone solvent, and the obtained solution was dipped on an aluminum drum. Method and then treated in air at 170 ° C. for 1 hour to form an organic photoreceptor layer (thickness 15 to
20 μm) was formed and a continuous printing resistance test was conducted using this organic photoreceptor. The test was performed using A4 test paper, but no image deletion occurred even after the continuous test of 30,000 sheets. Therefore, it was found that this organic photoreceptor also has excellent abrasion resistance. Furthermore, a printing test was conducted in a high temperature and high humidity environment, but no special image deterioration was observed.

Further, the same experiments as in Examples 1, 2 and 3 were conducted with different composition ratios of polymer compounds or different kinds of solvents. It was similar.

[0034]

As is apparent from the above description, according to the present invention, the electrophotographic characteristics of a single layer type are high in sensitivity and excellent in stability, charging property, sensitivity, printing resistance and heat resistance. It is possible to obtain a positively charged organic photoconductor having the above-mentioned property.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hiroki Kusanagi             3-10-1 Higashisanda, Tama-ku, Kawasaki City, Kanagawa Prefecture             No. Matsushita Giken Co., Ltd.

Claims (3)

[Claims] 1. An electrophotographic photoreceptor comprising an X-type phthalocyanine dispersed as a binder polymer in a polymer compound represented by the following general formula (Formula 1). [Chemical 1] 2. The electrophotographic photoconductor according to claim 1, wherein the composition ratio m: n of the copolymer in the general formula (Formula 1) is 1: 0.5 to 1:10. 3. The photoconductor for electrophotography according to claim 1, wherein the weight ratio of the X-type phthalocyanine and the polymer compound for binder is 1:10 to 1: 1.