JP2001022107A - Electrophotographic photoreceptor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a positive electrification type electrophotographic photoreceptor having Thigh sensitivity for a copying machine and for a printer by using a specified electronic conductive electric charge transferring material in a photosensitive layer. SOLUTION: A photosensitive layer containing an electric charge generating material and at least, one electronic conductive electric charge transferring material of formula I or II is disposed on an electrically conductive substrate. In the formula I, R1 and R2 are each H, halogen, a residue for forming a ring or the like, R3 and R4 are each 1-8C alkyl or the like, A1 is O or =CR5R6 (R5 and R6 are each cyano or alkoxycarbonyl), (m) is an integer of 1-4 and (n) is an integer of 1-5. In the formula II, R7-R9 are each H, halogen or the like, R10-R13 are each 1-8C alkyl or aryl which may have a substituent, B1 and B2 are each O or =CR14R15 (R14 and R15 are each cyano or aikoxycarbonyl) and (o), (p) and (q) are each an integer of 1-4.

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 for the photosensitive layer.

[0002]

2. Description of the Related Art In a conventional electrophotographic photoreceptor, an inorganic photoconductive substance such as selenium or a selenium alloy and an inorganic photoconductive substance such as zinc oxide or cadmium sulfide are dispersed in a resin binder as a photosensitive layer. I've been using what I did.
In recent years, research on electrophotographic photoreceptors using organic photoconductive materials has been advanced, and the photoreceptors have been put to practical use with improved sensitivity and durability.

An electrophotographic 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 photoreceptor that combines these functions in layers, a layer that mainly contributes to charge generation, and a layer that separates functions into a layer that contributes to surface charge retention and charge transport during photoreception in a dark place There is a laminated type photoconductor. For image formation by electrophotography using these photoconductors, for example, the Carlson method is applied. Image formation by this method involves charging a photoreceptor by corona discharge in a dark place, forming an electrostatic latent image such as a character or picture on an original on the charged photoreceptor surface, and forming a toner on the formed electrostatic latent image. After the toner image is transferred, the photoreceptor is subjected to charge elimination, removal of residual toner, light elimination and the like, and then reused.

[0004] Practical photoreceptors for organic electrophotography have advantages such as flexibility, film forming property, low cost, and safety compared to inorganic photoreceptors. Due to the nature, improvements in sensitivity, durability, etc. are being promoted.

[0005] Most of the organic photoreceptors are laminated photoreceptors in which the functions are separated into a charge generation layer and a charge transport layer. In general, a laminated organic photoreceptor is obtained by sequentially forming a charge generation layer composed of a charge generation substance such as a pigment or a dye and a charge transport layer composed of a charge transport substance such as hydrazone or triphenylamine on a conductive substrate. It is a hole transporting material due to the nature of the charge transporting material, and has sensitivity when the surface of the photoconductor is negatively charged. However, in the case of negative charging, the corona discharge used during charging is more unstable than in the case of positive charging, and ozone and nitrogen oxides are generated, and these are adsorbed on the surface of the photoreceptor and cause physical and chemical deterioration of the photoconductive layer. There is a problem that it is easy to cause and worsens the environment. For this reason, as a photoreceptor, a positive charge type photoreceptor having a greater degree of freedom in use conditions than a negative charge type photoreceptor has a wider and more advantageous application range.

[0006]

Various photoconductors used for positive charging have been proposed. For example, there is a method in which a charge generating substance and a charge transporting substance are simultaneously dispersed in a resin binder and used as a single photosensitive layer. However, sensitivity is insufficient for high-speed applications, and further improvements are required in terms of repetition characteristics. It is also conceivable to use a function separation type laminated structure for the purpose of increasing the sensitivity, to form a photoreceptor by laminating a charge generation layer on the charge transport layer, and to use the photoreceptor with positive charge. In this method, since the charge generation layer is formed on the surface, there is a problem in stability during repeated use due to corona discharge, light irradiation, mechanical wear, and the like. In this case, it has been proposed to further provide a protective layer on the charge generation layer. However, although mechanical wear is improved, there are problems such as a decrease in electrical characteristics such as sensitivity.

As a photoreceptor used for positive charging, there has been proposed a method of forming a photoreceptor by further laminating an electron-conductive charge transport layer on a charge generation layer. As charge transport materials, 2,4,7-trinitro-9-fluorenone and the like are known, but this material is carcinogenic and poses a safety problem. In addition, cyano compounds, quinone compounds and the like are disclosed in JP-A-50-131941, JP-A-6-59483, JP-A-9-59483.
Although proposed in Japanese Patent Application Publication No. 190002 and Japanese Patent Application Laid-Open No. Hei 9-19003, it is the fact that a compound having sufficient electron conductivity for practical use has not been obtained.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has as its object to use a novel electron-conductive charge transporting material for the photosensitive layer to provide a highly sensitive electrophotographic device for copying machines and printers. It is to provide a photoreceptor.

[0009]

According to the present invention, there is provided a photosensitive layer on a conductive substrate, wherein the photosensitive layer contains a charge generating substance and a charge transporting substance. This is achieved by including at least one of the electron-conductive charge transporting substances represented by I) or (II).

[0010]

Embedded image (In the formula (I), R ¹ and R ² are each a hydrogen atom, a halogen atom, an alkyl or alkoxy group having 1 to 8 carbon atoms, an aryl group which may have a substituent, and a residue for forming a ring. R ³ and R ⁴ are a hydrogen atom (except when both are hydrogen atoms), an alkyl group having 1 to 8 carbon atoms,
An aryl group which may have a substituent, A ¹ is an oxygen atom, = CR
⁵ R ⁶ (R ^{5 and} R ⁶ are a cyano group and an alkoxycarbonyl group, respectively), m represents an integer of 1 to 4, and n represents an integer of 1 to 5. )

[0011]

Embedded image (In the formula (II), R ⁷ , R ⁸ and R ⁹ are each a hydrogen atom,
A halogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group which may have a substituent, a residue for forming a ring,
R ¹⁰ , R ¹¹ , R ¹² and R ^{13 each} represent a hydrogen atom (except when both are hydrogen atoms), an alkyl group having 1 to 8 carbon atoms, an aryl group which may have a substituent, B ¹ and B ² Is an oxygen atom, = CR ¹⁴ R ¹⁵ (R ¹⁴ and R ¹⁵ are a cyano group and an alkoxycarbonyl group, respectively), and o, p and q each represent an integer of 1 to 4. In the above invention, it is effective that the photosensitive layer is a single layer type. Further, it is effective that the single-layer type photosensitive layer contains a hole-conductive charge transport material.

The charge transport material of the above general formula (I) or (II) is electron-conductive, and when this charge transport material is used in the photosensitive layer, a positively charged electrophotographic photosensitive member can be obtained. In a single-layer type electrophotographic photoreceptor, when the charge transport material of the general formula (I) or (II) is used together with a hole-conductive charge transport material, the sensitivity of the electrophotographic photoreceptor increases.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Specific examples of the charge transporting material represented by the general formula (I) or (II) include the chemical formulas (I-1) to (I-16), the chemical formulas (II-1) to (II) -16).

[0014]

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[0015]

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[0016]

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[0017]

Embedded image The general formula (I) or the general formula (I) used in the present invention.
The charge transport material shown in I) can be synthesized by a usual method. For example, chemical formula (I-1) or chemical formula
The compound represented by the formula (II-1) has the following chemical formula (III)
) Or by oxidizing the compound represented by the chemical formula (IV) in an organic solvent such as chloroform using an oxidizing agent such as potassium permanganate.

[0018]

Embedded image

[0019]

Embedded image FIG. 1 is a sectional view showing an example of a single-layer type electrophotographic photoconductor of the present invention. FIG. 2 is a cross-sectional view showing an example of the laminated electrophotographic photoconductor of the present invention. 1 is a conductive substrate, 2 and 5 are photosensitive layers, 3 is a charge generation layer, 4 is a charge transport layer, and 6 is a coating layer.

The electrophotographic photoreceptor shown in FIG. 1 is provided with a photosensitive layer 2 in which a charge generating substance and a charge transporting substance are dispersed in a resin binder (binder) on a conductive substrate 1 (single-layer type photosensitive element). (Referred to as the body). General formula (I) or (II)
The electron-conductive charge-transporting material represented by the formula (1) can be used together with a hole-conductive charge-transporting material. If necessary, a coating layer 6 can be provided.

The electrophotographic photoreceptor shown in FIG. 2 has a charge generating layer 3 mainly composed of a charge generating substance on a conductive substrate 1, and a charge transporting substance represented by the above general formula (I) or (II). Photosensitive layer laminated with charge transport layer 4 containing transport material
5 (referred to as a laminated photoreceptor).

The photoreceptor of FIG. 1 has a charge generating substance dispersed in a solution in which a charge transporting substance and a resin binder are dissolved.
The dispersion can be prepared by applying the dispersion on a conductive substrate. As the charge transport material, at least one of the electron-conductive charge transport materials represented by the general formula (I) or (II) is used. If necessary, a coating layer can be applied and formed.

In the photoreceptor shown in FIG. 2, a charge-generating substance is vacuum-deposited on a conductive substrate, or a dispersion obtained by dispersing particles of the charge-generating substance in a solvent or a resin binder is applied and dried. It is created by applying a solution in which a charge transport material and a resin binder are dissolved and drying it.

The conductive substrate 1 serves not only as an electrode of the photoreceptor but also as a support for the other layers. The conductive substrate 1 may be in the form of a cylinder, plate or film, and may be made of a metal such as aluminum, stainless steel, nickel or the like. Alternatively, a material obtained by performing a conductive treatment on glass, resin, or the like can be used.

The charge generating layer 3 is formed by applying a coating liquid in which particles of a charge generating substance are dispersed in a resin binder as described above, or by a method such as vacuum evaporation, and generates light by receiving light. I do. In addition, it is important that the charge generation efficiency is high, and at the same time, the injection property of the generated charge into the charge transport layer 4 is important. It is desirable that injection be good even at a low electric field with little dependence on the electric field. Examples of the charge generating substance include phthalocyanine compounds such as metal-free phthalocyanine and titanyl phthalocyanine, various azo compounds, quinone compounds, indigo compounds, cyanine compounds, squarylium compounds, azurenium compounds, and pigments or dyes such as selenium or selenium compounds. A suitable substance can be selected according to the wavelength range of the exposure light source used for image formation. Since the charge generation layer only needs to have a charge generation function, its thickness is determined by the light absorption coefficient of the charge generation substance and is generally 5 μm or less, preferably 2 μm or less.
It is as follows. The charge generation layer can be mainly composed of a charge generation substance and added with a charge transporting substance or the like. As the resin binder, polycarbonate, polyester, polyamide, polyurethane, vinyl chloride resin, polyvinyl butyral, diallyl phthalate resin, polymers and copolymers of methacrylic acid esters, and the like can be used in appropriate combinations.

The charge transport layer 4 is made of the above-mentioned general formula (I) or
(II) A coating film in which at least one of the charge transport materials shown in (II) is dispersed in a resin binder.It retains the charge of the photoreceptor as an insulator layer in a dark place, and is injected from the charge generation layer when receiving light. It has the function of transporting the electric charge. As the resin binder, a polymer and a copolymer of polycarbonate, polyester, polystyrene, and methacrylate can be used. In order to prevent the deterioration of ozone, which is a hindrance in using the photoreceptor, the charge transport layer 6 is provided with an amine, phenol, sulfur, phosphite, phosphorus, etc. It is also possible to include an agent.

The coating layer 6 has a function of receiving and holding the charge of corona discharge in a dark place, and has a performance of transmitting light which the photosensitive layer responds to. It is necessary to reach the layer and neutralize and extinguish the surface charge by receiving the generated charge. Organic insulating film-forming compounds such as polyester and polyamide can be applied to the coating. Further, these organic compounds and glass resins, inorganic compounds such as SiO ₂ , metals _, metal oxides, and the like can be mixed and used to reduce electric resistance.
As described above, it is desirable that the coating layer 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.

[0028]

EXAMPLES Example 1 X-type metal-free phthalocyanine (H ₂ Pc) 2 parts by weight, 40 parts by weight of the compound represented by the above formula (I-1), 60 parts by weight of the following benzene derivative having hole conductivity, polycarbonate A coating solution was prepared by kneading 80 parts by weight of a resin (PCZ-200: manufactured by Mitsubishi Gas Chemical) with methylene chloride for 3 hours using a mixer.
The photosensitive layer 2 was formed so as to be applied on an aluminum drum having an outer diameter of 30 mm and a length of 260 mm, which is a conductive substrate, and to have a thickness of about 20 μm after drying.

[0029]

Embedded image Example 2 2 parts by weight of titanyl phthalocyanine (TiOPc), 30 parts by weight of the compound represented by the above formula (I-2), 70 parts by weight of the following benzidine derivative having hole conductivity, polycarbonate resin (BP-PC: manufactured by Idemitsu Kosan Co., Ltd.) ) 80 parts by weight were kneaded with methylene chloride for 3 hours using a mixer to prepare a coating solution, and a photosensitive layer 2 was formed on an aluminum conductive substrate so as to have a film thickness of about 20 µm after being stimulated.

[0030]

Embedded image Example 3 2 parts by weight of titanyl phthalocyanine (TiOPc), 30 parts by weight of the compound represented by the above formula (I-5), 60 parts by weight of the following triphenylamine derivative having hole conductivity, a polycarbonate resin (BP-PC: Idemitsu) 80 parts by weight was kneaded with methylene chloride for 3 hours using a mixer to prepare a coating solution, and the film thickness after drying on an aluminum conductive substrate was about 20.
The photosensitive layer 2 was formed to have a thickness of μm.

[0031]

Embedded image Example 4 The procedure of Example 3 was repeated, except that the following squarylium compound was used instead of titanyl phthalocyanine, and the compound represented by the formula (II-1) was used instead of the compound represented by the formula (I-5). Photosensitive layer 2 was formed.

[0032]

Embedded image Example 5 A coating solution was prepared by kneading 70 parts by weight of titanyl phthalocyanine (TiOPc) and 30 parts by weight of a vinyl chloride copolymer (trade name: MR-110: manufactured by Zeon Corporation) with methylene chloride by a mixer for 3 hours. It was applied to a thickness of about 1 μm on a conductive substrate to form a charge generation layer 3. Then the chemical formula
100 parts by weight of the compound represented by (II-4), 100 parts by weight of a polycarbonate resin (PCZ-200: manufactured by Mitsubishi Gas Chemical), and 0.1 part by weight of silicone oil are mixed in methylene chloride, and about 10 parts by weight It was applied to a thickness of μm to form a charge transport layer 4. Example 6 Example 3 was repeated except that a bisazo pigment represented by the following chemical formula was used in place of titanyl phthalocyanine, and a compound represented by formula (II-4) was used in place of the compound represented by formula (I-5). A photosensitive layer 2 was prepared in the same manner as described above.

[0033]

Embedded image Example 7 Example 3 was repeated except that a bisazo pigment represented by the following chemical formula was used instead of titanyl phthalocyanine, and a compound represented by the chemical formula (II-7) was used instead of the compound represented by the chemical formula (I-5). Similarly, a photosensitive layer 2 was formed.

[0034]

Embedded image The electrophotographic characteristics of the photoreceptor thus obtained were measured. Vs (V) is the initial surface potential when the photoreceptor surface is positively charged by performing a +45 kV corona discharge in a dark place, and then the surface when the corona discharge is stopped and kept in a dark place for 5 seconds The potential Vd (V) is measured, and then the surface of the photoreceptor is irradiated with white light having an illuminance of 100 lux to obtain a time (second) until Vd is reduced to half, and the sensitivity E _1/2 (lxs) is obtained. did. Also illuminance
The surface potential when 100 lux of white light was irradiated for 10 seconds was defined as residual potential Vr (V). In Examples 1 to 5, 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, the same measurement was performed up to Vd, and then a 1 μW monochromatic light (780 nm) was applied instead of white light to determine the half-attenuated exposure (μJ / cm ² ). Was measured for residual potential Vr (V). Table 1 shows the measurement results.

[0035]

[Table 1] Electron-conductive charge-transporting material and hole-conductive charge-transporting material are used for the photosensitive layer of a single-layer electrophotographic photoreceptor, or electron-conductive charge transport is used for the charge-transporting layer of a laminated electrophotographic photoreceptor. When a substance is used, a positively chargeable and highly sensitive electrophotographic photosensitive member can be obtained.

[0036]

According to the present invention, a photosensitive layer is provided on a conductive substrate, the photosensitive layer contains a charge generating substance and a charge transporting substance, and the photosensitive layer is represented by the following general formula (I) or (II). Since at least one of the electron-conductive charge-transporting materials is included, a photosensitive member having high sensitivity and excellent electric characteristics in positive charging can be obtained. In addition, a suitable substance can be selected as the charge generating substance according to the type of exposure light source, and a photoreceptor that can be used in a semiconductor laser printer or a copying machine can be obtained using a phthalocyanine compound, a squarylium compound, a bisazo compound, or the like. . Further, 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 showing an example of a single-layer type electrophotographic photoreceptor of the present invention.

FIG. 2 is a cross-sectional view showing an example of a laminated electrophotographic photoconductor of the present invention.

[Explanation of symbols]

 1 conductive substrate 2 photosensitive layer 3 charge generation layer 4 charge transport layer 5 photosensitive layer 6 coating layer

Claims (3)

[Claims] 1. A photosensitive layer on a conductive substrate, wherein the photosensitive layer contains a charge generating substance and a charge transporting substance, and the photosensitive layer has an electron conductive charge represented by the following general formula (I) or (II). An electrophotographic photoreceptor comprising at least one transport material. Embedded image (In the formula (I), R ¹ and R ² are each a hydrogen atom, a halogen atom, an alkyl or alkoxy group having 1 to 8 carbon atoms, an aryl group which may have a substituent, and a residue for forming a ring. R ³ and R ⁴ are a hydrogen atom (except when both are hydrogen atoms), an alkyl group having 1 to 8 carbon atoms,
An aryl group which may have a substituent, A ¹ is an oxygen atom, = CR
⁵ R ⁶ (R ^{5 and} R ⁶ are a cyano group and an alkoxycarbonyl group, respectively), m represents an integer of 1 to 4, and n represents an integer of 1 to 5. ) (In the formula (II), R ⁷ , R ⁸ and R ⁹ are each a hydrogen atom,
A halogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group which may have a substituent, a residue for forming a ring,
R ¹⁰ , R ¹¹ , R ¹² and R ^{13 each} represent a hydrogen atom (except when both are hydrogen atoms), an alkyl group having 1 to 8 carbon atoms, an aryl group which may have a substituent, B ¹ and B ² Is an oxygen atom, = CR ¹⁴ R ¹⁵ (R ¹⁴ and R ¹⁵ are a cyano group and an alkoxycarbonyl group, respectively), and o, p and q each represent an integer of 1 to 4. ) 2. The electrophotographic photosensitive member according to claim 1, wherein the photosensitive layer is a single layer type. 3. The electrophotographic photosensitive member according to claim 2, wherein the photosensitive layer contains a charge transport material having hole conductivity.