JPH0715583B2 - Electrophotographic photoreceptor - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an electrophotographic photoreceptor for forming an electrostatic latent image.

Conventional Technology Conventionally, as electrophotographic photoreceptors, selenium, selenium alloys,
Those using an inorganic photoconductive material such as zinc oxide or cadmium sulfide have been mainly used. However, the electrophotographic photosensitive member using the inorganic photoconductive material, manufacturability, cost,
There was a problem in terms of flexibility.

In recent years, in order to solve the drawbacks of inorganic photoconductive materials, electrophotographic photoreceptors using organic photoconductive materials have been actively researched, such as polyvinylcarbazole and 2,4,7-trinitrofluorenone. An electrophotographic photoreceptor using a charge transfer complex, an electrophotographic photoreceptor using a eutectic complex of a pyrylium salt and alkylidene diarylene, and the like are known. Also x
− Type metal-free phthalocyanine pigment has a higher charge generation efficiency than α-type and β-type metal-free phthalocyanine, and has absorption up to a long wavelength region.Therefore, a semiconductor laser having an emission spectrum near 800 nm is used as a light source. It is known that the material is suitable as a photoreceptor for a laser printer, and an electrophotographic photoreceptor (JP-B-48-4338) in which the material is dispersed in a binder resin is also known. In addition, recently, an electrophotographic photosensitive member has been proposed in which the functions of absorbing light and generating electric charges and the function of transporting the generated electric charges are divided into separate materials (see, for example, JP-A-58-16247). Gazette), for example, a laminated type containing a bisazo pigment / pyrazoline derivative is put to practical use.

Problems to be Solved by the Invention However, electrophotographic photoreceptors using these organic photoconductive materials have low photosensitivity and have not been sufficient as photoreceptors. Further, a laminated electrophotographic photosensitive member having a charge-generating layer and a charge-transporting layer whose functions are separated from each other has not been sufficiently satisfactory in practical use.

By the way, in order to obtain satisfactory electrophotographic characteristics in a laminated type electrophotographic photoconductor in which a charge generation layer and a charge transport layer are functionally separated, as previously proposed, 1. It is necessary to satisfy the following conditions: efficiently generate electric charges with respect to the generated light, and 2. efficiently inject and transfer the generated electric charges into the charge transport material. That is, if the condition 1 is satisfied but the condition 2 is not satisfied,
Satisfactory photoresponsiveness cannot be obtained.

In addition, when the electrophotographic photosensitive member is one in which a charge generating layer and a charge transporting layer are laminated in this order, and light irradiation is performed from the charge transporting layer side, the conditions that must be met in order to obtain high sensitivity are:
It is necessary that the charge transport layer is sufficiently transparent to the light that is active in the charge generation layer.

In order to prepare an electrophotographic photosensitive member using the above-mentioned known charge generating material and charge transporting material, the above-mentioned conditions are satisfied, and sensitivity, receptive potential, potential holding property, potential stability, residual A set of materials that satisfies all the points such as electrophotographic characteristics such as electric potential and spectral characteristics, usage characteristics such as strength, durability and stain resistance, manufacturing stability when manufacturing by coating, quality stability, etc. Choosing a match is very difficult.

For example, as a material satisfying the above condition 1, more materials have been proposed in the past, and it is known that disazo pigments such as chlordian blue have a relatively high charge generation efficiency. In order to achieve this, it did not yet have sufficient photoresponsiveness.

Further, with respect to the charge transport layer, even if the charge generating material generates a sufficient charge, satisfactory electrophotographic characteristics cannot be obtained unless it is combined with a charge transport material that efficiently injects and carries the charge. It is known that the injectability in Condition 2 is related to some extent to the difference in ionization potential between the charge generating material and the charge transporting material, but it is only the result for a predetermined material, and It lacks the property, and the relation with the electrophotographic characteristics has not been clarified yet. It is considered that this is because the injection property largely depends on other properties of the charge generation material and the charge transport material. And as an electrophotographic photoreceptor,
It is considered that the magnitude of the influence of the factors affecting the injection property differs among various materials, and the effect of improving the injection property is not uniform.

The present invention has been made in view of the above circumstances, and provides an excellent electrophotographic photoreceptor by finding a combination of materials satisfying all the requirements required for an electrophotographic photoreceptor. The purpose is to do.

That is, an object of the present invention is to provide an electrophotographic photosensitive member which is excellent in electrophotographic characteristics such as photosensitivity, chargeability, cycle stability of potential and residual potential and which is effective in various electrophotographic processes.

Another object of the present invention is to provide an electrophotographic photosensitive member which has high sensitivity, high flexibility, is easy to manufacture and is low in cost.

Means for Solving the Problems The present inventors have found that the x-type metal-free phthalocyanine pigment has high charge generation efficiency, but has low mobility for transporting the generated charge and is insufficient in practical use. In consideration of the above, the charge-transporting material that can obtain an electrophotographic photoreceptor having excellent electrophotographic characteristics when used in combination with the x-type metal-free phthalocyanine pigment has been studied, and as a result, the following general formula (I It was found that the above object can be achieved by using the compound represented by the formula (1) and the compound represented by the general formula (II) in combination, and the present invention has been completed.

The electrophotographic photoreceptor of the present invention comprises a photosensitive layer provided on a conductive support, and the photosensitive layer contains an x-type metal-free phthalocyanine pigment as a charge generating material, and as a charge transporting material, It is characterized by containing at least one compound represented by the following general formula (I) and at least one compound represented by the following general formula (II).

(In the formula, R ₁ represents a hydrogen atom, an alkyl group or an alkoxy group, R ₂ represents a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, an alkoxycarbonyl group or a substituted amino group, and R ₃ represents an alkyl group, an alkoxy group. Represents a group, a halogen atom, an alkoxycarbonyl group or a substituted amino group) (In the formula, R ₄ , R ₅ and R ₆ each represent a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, an alkoxycarbonyl group or a substituted amino group.) The present invention is described in detail below.

The x-type metal-free phthalocyanine pigment used in the present invention refers to metal-free phthalocyanine having a crystal form defined as x-type, as described in JP-B-44-14106 and JP-A-49-4338.

On the other hand, examples of the compound represented by the general formula (I) include the following.

The following are examples of the compound represented by the general formula (II).

In the present invention, the x-type metal-free phthalocyanine pigment and the compounds represented by the general formulas (I) and (II) are contained in a photosensitive layer formed on a conductive support. Even if it has a single layer structure as shown in FIG.
As shown in FIGS. 1 and 2, a function-separated type laminated structure may be used. However, the latter is preferable in order to obtain more excellent electrophotographic characteristics.

In FIG. 1, a charge generating material 2 is formed on a conductive support 1.
Is formed, and the charge transport layer 5 containing the charge transport material 4 is formed on the charge generation layer 3, which is used as a negative charging type.

In contrast to FIG. 1, in FIG. 2, the charge transport layer 5 containing the charge transport material 4 is formed on the conductive support 1, and the charge generation layer containing the charge generation material 2 is formed thereon. It is used as a positively charged type.

In FIG. 3, a photoconductive layer 6 is formed on a conductive support 1, and a charge generating material 2 is formed in the photoconductive layer.
And the charge transport material 4 are included in a mixed state. This material may be used in either positive charging or negative charging, but it is preferably used in positive charging.

The conductive support used in the present invention is a metal plate made of aluminum, nickel, chromium, stainless steel or the like, a metal drum or a metal foil, and aluminum, titanium, nickel, chromium, SUS, gold, vanadium, tin oxide. , A plastic film provided with a thin film of indium oxide, ITO, or the like, or paper or a plastic film coated or impregnated with a conductivity-imparting agent.

The charge generation layer is formed by dispersing an x-type metal-free phthalocyanine pigment in a binder resin solution and applying the dispersion. As the dispersing means, commonly used ones such as a ball mill, a roll mill, a sand mill, an attritor and the like can be used. The compounding ratio of the x-type metal-free phthalocyanine pigment and the binder resin is 40: 1 to 1:10, preferably 20: 1 to 1: 3.
If the ratio of the x-type metal-free phthalocyanine pigment is too high, the stability of the coating solution decreases, and if it is too low,
Since the sensitivity is lowered, it is desirable to set it in the above range.
As the solvent for the binder resin, any solvent can be used as long as it is soluble and can be applied, but it is desirable to select a solvent having good pigment dispersibility. Also, a plurality of solvents may be used in combination.

Known binder resins, for example, polycarbonate, polystyrene, polyester, polyvinyl butyral, methacrylic acid ester polymer or copolymer, vinyl acetate polymer or copolymer, cellulose ester or ether, polybutadiene, polyurethane, epoxy resin. Are used. These may be used in combination.

The particle size of the x-type metal-free phthalocyanine pigment after dispersion is 1
μm or less is preferable. If the particle size is too large, the stability of the coating material may deteriorate and the image quality may deteriorate.

The thickness of the charge generation layer is 0.01 μm to 5 μm, preferably about 0.03 μm to 2 μm. When the film thickness is larger than the above range, problems such as a decrease in charging property, an increase in dark decay, and a decrease in repeated stability are caused.
The sensitivity decreases.

The charge transport layer is formed by dispersing at least one compound represented by the general formula (I) and at least one compound represented by the general formula (II) in a resin for film formation. In this case, these two compounds can be used in an arbitrary mixing ratio, but when they are almost equivalent, it is preferable to use them in a ratio.
The compounding ratio of these two compounds and the resin is 5: 1 to 1: 1.
5, preferably 3: 1 to 1: 3. If the former ratio is too high, the mechanical strength of the charge transport layer will decrease, and if it is too low, the sensitivity will decrease, so the above range is preferred.

The film-forming resin is used for forming a film because the compound does not have film-forming property by itself, and may be a resin having high compatibility with the compound and high film-forming property. Anything will do. Examples of usable resins include polycarbonate, polyacrylate, polyester, polystyrene, styrene-acrylonitrile copolymer, polysulfone, polymethacrylic acid ester,
Examples thereof include styrene-methacrylic acid ester copolymers and vinyl polymers.

The charge transport layer is obtained by dissolving the compound and the resin in a solvent,
It is formed by applying. The solvent used depends on the resin, but any solvent can be used as long as it can dissolve both the compound and the resin.

The thickness of the charge transport layer is preferably about 5 to 50 μm.

In many cases, in the electrophotographic photoreceptor of the present invention, it is preferable to provide a barrier layer between the photosensitive layer and the conductive support. The barrier layer is effective in preventing unnecessary injection of charges from the support, and has the action of increasing the chargeability of the photosensitive layer and improving the image quality. Further, it also has the function of improving the adhesiveness between the photosensitive layer and the conductive support. As the material forming the barrier layer, polyvinyl alcohol, polyvinylpyrrolidone, polyvinylpyridine, cellulose ethers, cellulose esters, polyamide, polyurethane, casein, gelatin, polyglutamic acid, starch,
Starch acetate, amino starch, polyacrylic acid salt, polyacrylamide, silane coupling agent, zirconium chelate, titanium chelate and the like can be mentioned. The resistivity of these materials is preferably about 10 ⁵ to 10 ¹⁴ Ω · cm. The film thickness of the barrier layer is set to about 0.01 to 2 μm.

Further, if necessary, a protective layer may be provided on the photosensitive layer. This protective layer is used to prevent chemical deterioration of the photosensitive layer having a laminated structure during charging and to improve the mechanical strength of the photosensitive layer.

The protective layer is formed by containing a conductive material in a suitable binder. As the conductive material, a metallocene compound such as N, N'-dimethylferrocene, N, N'-diphenyl-N, N'-bis- (3-methylphenyl)-[1,1'-
Materials such as aromatic amino compounds such as biphenyl] -4,4'-diamine, metal oxides such as antimony oxide, tin oxide, titanium oxide, indium oxide, and tin oxide-antimony oxide can be used. It is not limited to. As the binder resin used for this protective layer, known resins such as polyamide resin, polyurethane, polyester resin, epoxy resin, polyketone resin, polycarbonate, polyvinylketone resin, polystyrene and polyacrylamide resin can be used. It is not limited to the above.

This protective layer is preferably configured so that its electric resistance is 10 ⁹ to 10 ¹⁴ Ω · cm. Electric resistance is 10 ¹⁴ Ωcm
When it is above the above value, the residual potential is increased, resulting in a copy with a lot of fog, and when it is 10 ⁹ Ω · cm or less, the image is blurred and the resolution is deteriorated. Furthermore, this protective layer is
It must be constructed so as not to substantially interfere with the passage of the light used for imagewise exposure.

The thickness of the protective layer used in the present invention is 0.5 to 20 μm,
A range of 1 to 10 μm is preferable.

This protective layer can be formed by a commonly used coating method such as a blade coating method, a wire bar coating method, a spray coating method, a dip coating method, a bead coating method and a curtain coating method.

According to the present invention, by using at least one of each of the compound represented by the general formula (I) and the compound represented by the general formula (II) as the charge transport material, the charge generation efficiency is high, The x-type metal-free phthalocyanine, which had a substantially low sensitivity due to its low charge-transporting property, was compensated for by its low charge-transporting ability, resulting in a substantially high-sensitivity electrophotographic photoreceptor. It is supposed that it will be.

Examples Hereinafter, the present invention will be described with reference to Examples.

Example 1 1 part by weight of x-type metal-free phthalocyanine pigment, polyvinyl butyral resin (B-90; 10 from Mitsubishi Monsanto Kasei Co., Ltd.)
10 parts by weight of cyclohexanone solution by weight and 60 parts by weight of cyclohexanone were dispersed by a grinder mill for 5 hours, the resulting dispersion was applied to an aluminum sheet with an applicator, and dried at 120 ° C for 10 minutes to form a charge generation layer. Was formed. The film thickness was measured and found to be 0.4 μm. Next, 3 parts by weight of each of the exemplified compounds I-36 and II-19 and 4 parts by weight of a polycarbonate resin (trade name: Lexan 145, manufactured by GE; molecular weight 35000/40000) were dissolved in 40 parts by weight of dichloromethane. In addition to the obtained solution, the obtained coating solution was applied onto the charge generation layer with an applicator to form a charge transport layer. After drying at 120 ° C. for 1 hour, the film thickness was measured and found to be 21 μm.

The electrophotographic photosensitive sheet thus produced was wrapped around an 84 mmφ aluminum pipe and evaluated as follows by an electrophotographic characteristic evaluation apparatus.

First, charge the photoreceptor so that the current flowing to it is -10 μA.
The surface potential 1 second after the charging was measured and defined as Vpo (volt). After that, static electricity was removed with a tungsten lamp, and the potential after static elimination was measured, and this was taken as the residual potential VR. This operation
It was repeated 100 times and the stability was examined.

Then, adjust the charging current so that VPO becomes -800V,
Exposure amount E (erg / c) of monochromatic light of 800 nm 0.3 seconds after charging
m ² ), exposure was performed, the potential at 0.7 seconds after exposure (1 second after charging) was measured, and the attenuation rate of the potential from VPO was calculated as dV / dE. The results are shown in Table 1.

Comparative Example 1 Polycarbonate (bisphenol Z type, molecular weight 30
000) 10 parts by weight was dissolved in 40 parts by weight of monochlorobenzene, 1 part by weight of x-type metal-free phthalocyanine was further added thereto, and dispersed by a paint shaker for 2 hours to prepare a coating solution. This coating solution was applied onto an aluminum sheet with a wire bar and dried to form a 19 μm photoconductive layer. Evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

Comparative Examples 2 and 3 As the charge transport material, each of the exemplified compounds I-36 and II-19 used in Example 1 was used alone. That is,
3 parts by weight of Exemplified Compound I-36 or 6 of Exemplified Compound II-19
Parts by weight and polycarbonate resin (trade name: Lexan 145,
4 parts by weight of GE; molecular weight 35000/40000) was dissolved in 28 parts by weight of dichloromethane, and the obtained coating solution was applied in the same manner on the charge generation layer formed in the same manner as in Example 1 to obtain an electrophotographic image. A photoconductor sheet was prepared. The obtained electrophotographic sheet was evaluated in the same manner as in Example 1.
The results are shown in Table 1.

Comparative Example 4 Except that the exemplified compound I-2 was used as the charge transport material,
An electrophotographic photosensitive sheet was prepared by the same method as in Comparative Example 2 and evaluated in the same manner. The results are shown in Table 1.
The combination of the charge generating material and the charge transporting material in this comparative example is the same as that disclosed in JP-A-58-16247.

Examples 2 to 4 Electrophotographic photoreceptor sheets were prepared in the same manner as in Example 1 except that the combination of the compounds shown in Table 1 was used as the charge transport material, and the same evaluation was performed. The results are shown in Table 1.

From the results of Table 1, in the case of the present invention in which the compounds represented by the general formulas (I) and (II) are used in combination, the photosensitivity (dV / dE) is higher than that in the case of using those compounds alone. ) And the charging property (VPO2) are improved.

EFFECTS OF THE INVENTION In the present invention, as is clear from a comparison between Examples and Comparative Examples, an x-type metal-free phthalocyanine pigment is used as a charge generating material, and a compound represented by the general formula (I) is used as a charge transporting material. By using both of the compounds represented by the general formula (II) in combination, the photosensitivity of the photoconductive layer using the x-type metal-free phthalocyanine pigment is increased, and
The effect is that the photosensitivity and the charging property of the electrophotographic photosensitive member are improved as compared with the case where the both compounds are used alone. Further, the electrophotographic photosensitive member of the present invention is excellent in potential cycle stability and residual potential, and is highly flexible and easy to manufacture.

[Brief description of drawings]

1, FIG. 2 and FIG. 3 are schematic diagrams for explaining the constitution of the electrophotographic photosensitive member of the present invention. 1 ... Conductive support, 2 ... Charge generating material, 3 ... Charge generating layer, 4 ... Charge transporting material, 5 ... Charge transporting layer, 6 ...
… Photoconductive layer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Eiichi Aonuma 1600 Takematsu, Minami Ashigara City, Kanagawa Prefecture Fuji Xerox Co., Ltd. Takematsu Plant (72) Inventor Ryosaku Igarashi 1600 Takematsu, Minami Ashigara City, Kanagawa Prefecture Fuji Xerox Co., Ltd. Takematsu On-site (72) Inventor Koichi Yamamoto 1600 Takematsu, Minamiashigara-shi, Kanagawa Fuji Xerox Co., Ltd.Takematsu Office (72) Inventor Taketoshi Hoshizaki 1600 Takematsu, Minamiashigara-shi, Kanagawa Fuji Xerox Co., Ltd. Takematsu Office (56) Reference Documents JP-A-58-203446 (JP, A) JP-A-61-53647 (JP, A)

Claims (2)

[Claims] 1. An electrophotographic photoreceptor comprising a photosensitive layer provided on a conductive support, wherein the photosensitive layer contains an x-type metal-free phthalocyanine pigment as a charge generating material, and the following charge transporting material: An electrophotographic photoreceptor comprising at least one compound represented by the general formula (I) and at least one compound represented by the following general formula (II). (In the formula, R ₁ represents a hydrogen atom, an alkyl group or an alkoxy group, R ₂ represents a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, an alkoxycarbonyl group or a substituted amino group, and R ₃ represents an alkyl group, an alkoxy group. Represents a group, a halogen atom, an alkoxycarbonyl group or a substituted amino group) (In the formula, R ₄ , R ₅ and R ₆ each represent a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, an alkoxycarbonyl group or a substituted amino group.) 2. A charge generation layer containing an x-type metal-free phthalocyanine pigment, a compound represented by the general formula (I) and a compound represented by the general formula (II) on a conductive support. A charge transporting layer containing one type of each is sequentially laminated to form a charge transport layer.
The electrophotographic photosensitive member according to the item.