JP3114394B2 - Electrophotographic photoreceptor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photosensitive layer of an electrophotographic photoreceptor, and more particularly to a charge transport material used for the photosensitive layer.

[0002]

2. Description of the Related Art Conventionally, photosensitive materials for electrophotographic photoreceptors (hereinafter also referred to as photoreceptors) include inorganic photoconductive substances such as selenium or selenium alloys, and organic photoconductive substances such as phthalocyanine compounds or bisazo compounds. A material dispersed in a binder or the like or a material subjected to vacuum deposition is used.

A photoreceptor is required to have a function of retaining a surface charge in a dark place, a function of receiving light to generate a charge, and a function of receiving light and transporting a charge. A so-called single-layer type photoreceptor that combines these functions,
There is a so-called laminated photoreceptor in which a layer which is functionally separated is laminated on a layer mainly contributing to charge generation and a layer contributing to charge retention and surface charge transport in a dark place. For image formation by electrophotography using these photoconductors, for example, the Carlson method is applied. Image formation in this method is performed by charging a photoreceptor by corona discharge in a dark place, forming an electrostatic latent image such as a character or a picture of a document on the charged photoreceptor surface,
The formed electrostatic latent image is developed with toner, and the developed toner image is fixed on a support such as paper. After the transfer of the toner image, the photoconductor is subjected to static elimination, removal of residual toner, light neutralization, and the like. After that, it is reused.

In recent years, many applications of photoconductive organic compounds having excellent charge transporting ability to photoreceptors have been proposed due to their advantages such as flexibility, thermal stability, and film forming properties. For example, oxadiazole compounds include US Pat.
No. 7, Japanese Patent Publication No. 59-2 as a pyrazoline compound
No. 023, and Japanese Patent Publication No. Sho 5
Various charge transport materials are known from JP-A-5-42380, JP-A-57-101844, JP-A-54-150128, and the like.

[0005]

As described above, an organic material has many advantages that an inorganic material does not have, but at the same time, a material that sufficiently satisfies all the characteristics required for an electrophotographic photosensitive member can be obtained. At present, there is a problem in sensitivity and characteristics in repeated continuous use. The present invention has been made in view of the above points, and its purpose is to use a new organic material that has never been used as a charge transport material in the photosensitive layer, thereby achieving high sensitivity and excellent repetition characteristics. An object of the present invention is to provide an electrophotographic photosensitive member for a copying machine and a printer.

[0006]

According to a first aspect of the present invention, there is provided a photosensitive layer having a dithienylbenzene derivative represented by the following general formula (I):

[0007]

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(Wherein R ₁ , R ₂ , R ₃ and R ₄ each represent a hydrogen atom, a halogen atom, an alkyl group or an alkoxy group, and R ₅ and R ₆ each represent a substituted or unsubstituted aryl group. According to the second aspect of the present invention, there is provided a photosensitive layer, which is achieved by including a dithienylbenzene derivative represented by the following general formula (II).

[0009]

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Wherein R ₁₃ , R ₁₄ , R ₁₅ and R ₁₆ each represent a hydrogen atom, a halogen atom, an alkyl group or an alkoxy group, and R ₁₁ , R ₁₂ , R ₁₇ and R ₁₈ each represent a substituted or unsubstituted Represents an aryl group.)

[0011]

The use of the dithienylbenzene derivative represented by formula (I) or (II) in a photosensitive layer has not been known. The present inventors have made intensive studies on various organic materials to achieve the above object, and as a result of conducting a number of experiments on these dithienylbenzene derivatives, the technical elucidation has not yet been sufficiently completed. It has been found that the use of a dithienylbenzene derivative having a specific structure represented by the above general formula (I) or (II) as a charge transporting substance is extremely effective in improving electrophotographic properties, and is repeated with high sensitivity. As a result, a photosensitive member having excellent characteristics was obtained.

[0012]

EXAMPLES The dithienylbenzene derivative of the general formula (I) or (II) used in the present invention can be synthesized by a usual method. That is, the following general formula (III
) Or (IV) and a reagent represented by the following general formula (V) in an appropriate organic solvent (eg, dimethylformamide, dimethoxyethane, etc.) in the presence of an alkali to easily synthesize the aldehyde. can do.

[0013]

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Specific examples of the dithienylbenzene derivative represented by the general formula (I) are as follows.

[0015]

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[0016]

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[0017]

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Specific examples of the dithienylbenzene derivative represented by the general formula (II) are as follows.

[0019]

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The photoreceptor of the present invention contains the above-mentioned dithienylbenzene derivative in the photosensitive layer.
Depending on the application of these dithienylbenzene derivatives, they can be used as shown in FIG. 1, FIG. 2, or FIG. FIG. 1 is a cross-sectional view showing a single-layer type photoreceptor according to an embodiment of the present invention, FIG. 2 is a cross-sectional view showing a negatively-charged laminated type photoreceptor according to an embodiment of the present invention, and FIG. 1 is a cross-sectional view showing a positively-charged laminated photoreceptor according to the embodiment. 1
Is a photosensitive substrate, 20, 21 and 22 are photosensitive layers, 3 is a charge generation material, 4 is a charge generation layer, 5 is a charge transport material, 6 is a charge transport layer, and 7 is a coating layer.

FIG. 1 shows that a charge generating substance 3 is placed on a conductive substrate 1.
And a photosensitive layer 20 (usually referred to as a single-layer type photoreceptor) in which a dithienylbenzene derivative as a charge transporting substance 5 is dispersed in a resin binder (binder). FIG. 2 shows a photosensitive layer 21 (FIG. 2) formed by laminating a charge generating layer 4 mainly composed of a charge generating substance 3 and a charge transporting layer 6 containing a dithienylbenzene derivative as a charge transporting substance 5 on a conductive substrate 1. (A configuration generally called a laminated photoconductor).

FIG. 3 shows a layer configuration reverse to that of FIG.
In this case, it is general to further provide a coating layer 7 to protect the charge generation layer 4. The reason for using the two types of layer constitutions shown in FIGS. 2 and 3 is that even if the layer constitution shown in FIG. 2 which is usually used as a negative charging method is used in the positive charging method, a charge transport material suitable for this is still found. Therefore, it is necessary for the photoconductor of the positive charging type to have the layer configuration shown in FIG. 3 at this stage.

The photoreceptor shown in FIG. 1 can be prepared by dispersing a charge generating substance in a solution in which a charge transporting substance and a resin binder are dissolved, and applying this dispersion to a conductive substrate. The photoreceptor in FIG. 2 is obtained by vacuum-depositing a charge-generating substance on a conductive substrate, or applying a dispersion obtained by dispersing particles of the charge-generating substance in a solvent or a resin binder, drying and coating the dispersion. It can be prepared by applying and drying a solution in which a charge transport material and a resin binder are dissolved.

In the photoreceptor shown in FIG. 3, a solution in which a charge transporting substance and a resin binder are dissolved is applied to a conductive substrate and dried, and a charge generating substance is vacuum-deposited thereon, or particles of the charge generating substance are deposited. It can be prepared by applying and drying a dispersion obtained by dispersing in a solvent or a resin binder, and further forming a coating layer. The conductive substrate 1 serves as an electrode of the photoreceptor and serves as a support for the other layers, and may be cylindrical, plate-like, or film-like. The material may be aluminum, stainless steel, nickel, or the like. It is possible to use metal, glass, resin, or the like which is subjected to a conductive treatment.

The charge generation layer 4 is formed by applying a material in which the particles of the charge generation substance 3 are dispersed in a resin binder as described above, or by a method such as vacuum deposition. Occurs. In addition, it is important that the charge generation efficiency is high and at the same time, the generated charge is injected into the charge transporting layer 6 and the coating layer 7. As the charge generating substance, phthalocyanine compounds such as metal-free phthalocyanine and titanyl phthalocyanine, various azo, quinone, indigo pigments, dyes such as cyanine, squarylium, azurenium, and pyrylium compounds, and selenium or selenium compounds are used. A suitable substance can be selected according to the light wavelength range of the exposure light source used. Since the charge generation layer only needs to have a charge generation function,
The film thickness is determined by the light absorption coefficient of the charge generating substance and is generally 5 μm or less, preferably 1 μm or less. The charge generation layer can be mainly composed of a charge generation substance and added with a charge transporting substance or the like. As resin binder, polycarbonate, polyester,
Polyamide, polyurethane, vinyl chloride, phenoxy resin, polyvinyl butyral, diallyl phthalate resin,
Methacrylic acid ester polymers and copolymers can be used in appropriate combination.

The charge transport layer 6 is a coating film in which a dithienylbenzene derivative represented by the above general formula (I) or (II) is dispersed as an organic charge transport material in a resin binder. It has the function of retaining the charge of the photoreceptor and transporting the charge injected from the charge generation layer when receiving light. As the resin binder, polymers and copolymers of polycarbonate, polyester, polystyrene and methacrylate can be used.

The coating layer 7 has a function of receiving and holding the charge of the corona discharge in a dark place, and has a performance of transmitting light which the charge generating layer is sensitive to.
It is necessary to reach the charge generation layer and neutralize the surface charge by injection of the generated charge. As the coating material, an organic insulating film forming material such as polyester and polyamide can be applied. In addition, these organic materials can be mixed with an inorganic material such as a glass resin and SiO _2, and a material such as a metal or a metal oxide that reduces electric resistance. As described above, it is desirable that the coating material is as transparent as possible in the wavelength region where the light absorption of the charge generating substance is maximum.

Although the thickness of the coating layer itself depends on the composition of the coating layer, it can be arbitrarily set within a range where adverse effects such as an increase in residual potential do not occur when used repeatedly and continuously. Example 1 50 parts by weight of x-type metal-free phthalocyanine (H ₂ Pc) and dithienylbenzene derivative 1 represented by the above formula I-1
00 parts by weight of polyester resin (trade name: Byron 20)
0: 100 parts by weight of Toyobo) and tetrahydrofuran (T
HF) The mixture was kneaded with a solvent by a mixer for 3 hours to prepare a coating solution, and the solution was applied on an aluminum-evaporated polyester film (Al-PET) as a conductive substrate by a wire bar method, and the film thickness after drying was obtained. Was made to be 15 μm. Example 2 100 parts by weight of a dithienylbenzene derivative represented by the above formula I-2 and 100 parts by weight of a polycarbonate resin (trade name: Panlite L-1225: manufactured by Teijin Chemicals) were dissolved in methylene chloride. The coating liquid was applied on an aluminum-evaporated polyester film substrate with a wire bar, and a charge transport layer was formed so that the film thickness after drying was 15 μm. On the charge transporting layer thus obtained, 1
50 hours of pulverized titanyl phthalocyanine (TiOP
c) 50 parts by weight of polyester resin (trade name: Byron 2)
00: Toyobo) 50 parts by weight together with a THF solvent for 3 hours
A coating solution was prepared by kneading with a mixer, applied by a wire bar, and a charge generation layer was formed so that the film thickness after drying was 1 μm. Example 3 In Example 2, the following structural formula (V) was used instead of TiOPc.
A photoconductor was prepared by the same way as that of Example 2 except that the squarylium compound represented by I) was used and the charge transporting substance was changed to the dithienylbenzene derivative represented by the above chemical formula II-1.

[0029]

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Example 4 In Example 2, chlorodiamble, which is a bisazo pigment, was used in place of TiOPc, and the charge transporting substance was changed to the dithienylbenzene derivative represented by the above formula I-4. Similarly, a photoreceptor was prepared. The electrophotographic characteristics of the photoreceptor thus obtained were measured using an electrostatic recording paper tester “SP-428” manufactured by Kawaguchi Electric.

The surface potential V _S (V) of the photosensitive member is +
This is the initial surface potential when the photoreceptor surface is positively charged by a corona discharge of 6.0 kV, and the time until the surface potential is reduced to half by irradiating the surface of the photoreceptor with white light having an illuminance of 2 lx (s) ) To obtain the half-attenuated exposure amount E _1/2 (lx · s)
And In addition, the surface potential when white light having an illuminance of 2 lx was irradiated for 10 seconds was defined as a residual potential V _r (V). For Examples 1 to 3, high sensitivity with long wavelength light can be expected.
Therefore, the electrophotographic characteristics when monochromatic light having a wavelength of 780 nm was used were also measured. That is, a half-attenuated exposure amount (μJ / cm ² ) is obtained by irradiating 1 μW monochromatic light (780 nm) instead of white light, and the residual potential V _r ( V) was measured. Table 1 shows the measurement results.

[0032]

[Table 1] As can be seen from Table 1, Examples 1, 2, 3, and 4 show the same characteristics with respect to the half-attenuated exposure amount and the residual potential, and also show good surface potential. Further, in Examples 1 to 3, high sensitivity was exhibited even with light having a long wavelength of 780 nm, and it can be seen that the light emitting device was sufficiently usable for a semiconductor laser printer. Example 5 A coating solution obtained by kneading 50 parts by weight of an x-type metal-free phthalocyanine and 50 parts by weight of a vinyl chloride copolymer (trade name: MR-110: manufactured by Zeon Corporation) together with methylene chloride by a mixer for 3 hours in the same manner as in Example 2. Was prepared and coated on an aluminum support to a thickness of about 1 μm to form a charge generation layer. Next, 100 parts by weight of a dithienylbenzene derivative represented by the chemical formula I-6, 100 parts by weight of a polycarbonate resin (Panlite L-1250), and 0.1 parts of silicone oil
Parts by weight with methylene chloride and add about 1 part over the charge generating layer.
It was applied so as to have a thickness of 5 μm to form a charge transport layer.

In the photoreceptor thus obtained, good results were obtained with Vs = −780 V and E _1/2 = 2.2 lx · s. Example 6 In Example 5, a bisazo pigment represented by the following structural formula (VII) was used in place of metal-free phthalocyanine, and the charge transporting substance was changed to a dithienylbenzene derivative represented by chemical formula II-2. A photoreceptor was prepared in the same manner as described above.

In the photoreceptor thus obtained, Vs = −680 V and E _1/2 = 3.0 lx · s, which were good results.

[0035]

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[0036]

According to the present invention, since the dithienylbenzene derivative represented by the general formula (I) or (II) is used as a charge transporting substance on a conductive substrate, high sensitivity can be obtained even in positive charging and negative charging. In addition, a photoreceptor having excellent repetition characteristics can be obtained. In addition, a charge generating substance can be selected according to the type of an exposure light source. Can be obtained.
Furthermore, if necessary, a coating layer can be provided on the surface to improve the durability.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a single-layer photoconductor according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a negatively-charged laminated photoreceptor according to an embodiment of the present invention;

FIG. 3 is a cross-sectional view showing a positively charged laminated photoconductor according to an embodiment of the present invention.

[Brief description of reference numerals]

 REFERENCE SIGNS LIST 1 conductive substrate 3 charge generating material 4 charge generating layer 5 charge transporting material 6 charge transporting layer 7 coating layer 20 photosensitive layer 21 photosensitive layer 22 photosensitive layer

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-136949 (JP, A) JP-A-3-122650 (JP, A) JP-A-2-153358 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) G03G 5/06

Claims (7)

(57) [Claims] 1. A photosensitive layer having the following general formula (I):
A photoconductor for electrophotography, comprising a dithienylbenzene derivative represented by the formula (1) as a charge transporting substance. Embedded image (In the formula, R ₁ , R ₂ , R ₃ and R ₄ each represent a hydrogen atom, a halogen atom, an alkyl group or an alkoxy group, and R ₅ and R ₆ each represent a substituted or unsubstituted aryl group.) 2. A photosensitive layer having the following general formula (II):
A photoconductor for electrophotography, comprising a dithienylbenzene derivative represented by the formula (1) as a charge transporting substance. Embedded image (Wherein R ₁₃ , R ₁₄ , R ₁₅ and R ₁₆ each represent a hydrogen atom, a halogen atom, an alkyl group, or an alkoxy group;
R ₁₁ , R ₁₂ , R ₁₇ and R ₁₈ each represent a substituted or unsubstituted aryl group. ) 3. The electrophotographic photoconductor according to claim 1, wherein the photoconductive layer is formed by laminating a charge generation layer and a charge transport layer. 4. The electrophotographic photoreceptor according to claim 1, wherein the dithienylbenzene derivative has R ₁ as a methyl group,
R ₂ , R ₃ , and R ₄ are each a hydrogen atom, and R ₅ and R ₆ are each a p-tolyl group. 5. The electrophotographic photosensitive member according to claim 1, wherein
Thus, the dithienylbenzene derivative is represented by R₁, R_FourIs methyl
Group, R_Two, R_Three, Are each a hydrogen atom, R_Five, R ₆But
Electrophotographic feeling characterized by each being a phenyl group
Light body. 6. The electrophotographic photoreceptor according to claim 2, wherein the dithienylbenzene derivative is R ₁₁ , R ₁₂ , R ₁₇ , R
_18. An electrophotographic photoconductor, wherein ₁₈ is a phenyl group, R ₁₃ and R ₁₆ are each a methyl group, and R ₁₄ and R ₁₅ are each a hydrogen atom. 7. The electrophotographic photoreceptor according to claim 2, wherein the dithienylbenzene derivative has R ₁₁ and R ₁₈ as phenyl groups, R ₁₂ and R ₁₇ as p-tolyl groups, respectively.
R ₁₃ and R ₁₆ each represent a hydrogen atom, and R ₁₄ and R ₁₅ each represent a methyl group.