JP2001147543A - Electrophotographic photoreceptor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a good positive electrification type electrophotographic photoreceptor usable in a high-speed copying machine and a high-speed printer by using a new electron transferring organic material as an electric charge transferring material in a photosensitive layer. SOLUTION: In the electrophotographic photoreceptor obtained by disposing a photosensitive layer containing an electric charge generating material and an electric charge transferring material on an electrically conductive substrate, the photosensitive layer contains at least one electron transferring compound of formula I.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoreceptor for electrophotography (hereinafter, also simply referred to as "photoreceptor"), and more particularly, to an electrophotographic method in which a photosensitive layer containing an organic material is provided on a conductive substrate. And a photoreceptor for electrophotography used in printers, copiers and the like.

[0002]

2. Description of the Related Art In the field of electrophotographic photoreceptors, in recent years, studies on electrophotographic photoreceptors using organic photoconductive materials have been advanced, and some of them have been put to practical use with improved sensitivity and durability. is there.

A photoreceptor generally needs a function of retaining surface charges in a dark place, a function of receiving light to generate charges, and a function of receiving light and transporting charges. The so-called single-layer type photoreceptor, which combines these functions in one layer, a layer mainly contributing to charge generation, and a layer contributing to surface charge retention in a dark place and charge transport during photoreception. There is a so-called laminated type photoconductor in which layers separated in function are laminated.

For example, the Carlson process is applied to image formation by electrophotography using these photosensitive members. Image formation by 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 on a document by exposing the charged photoreceptor surface, and forming the formed static image. The latent image is developed by toner, and the developed toner image is fixed on a support such as paper.After the toner image is transferred, the photosensitive member is subjected to static elimination, removal of residual toner, light neutralization, etc. Served for use.

Organic photoreceptors that have been put to practical use have many advantages over conventional inorganic photoreceptors, such as flexibility, film forming properties, low cost, and safety. Improvements such as gender are being promoted.

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 has a charge generation layer mainly composed of a charge generation substance such as a pigment or a dye on a conductive substrate, and a charge transport layer mainly composed of a charge transport substance such as hydrazone or triphenylamine. Layers in order, and due to the nature of the electron-donating charge transporting substance, it becomes a hole transfer type,
It has sensitivity when the surface of the photoreceptor is negatively charged. However, in the case of negative charging, corona discharge used during charging is more unstable than in the case of positive charging, and ozone and nitrogen oxides are generated, which are adsorbed on the photoreceptor surface and cause physical and chemical deterioration. There is also a problem that it is easy and the environment is worsened. From such a point, as a photoreceptor, a positive charging type photoreceptor having a greater degree of freedom of use conditions than a negative charging type photoreceptor has a wider and more advantageous application range.

Therefore, various photoconductors for use in positive charging have been proposed. For example, a method has been proposed 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, and some of them have been put to practical use. However, the single-layer type photoreceptor has insufficient sensitivity for application to a high-speed machine, and further improvement is necessary in terms of repetition characteristics and the like.

A method of forming a photoreceptor by stacking a charge generation layer on a charge transport layer and forming a photoreceptor for positive charge may be considered for the purpose of increasing the sensitivity. However, in this method, since the charge generation layer is formed on the surface, there is a problem in stability at the time of 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 is a problem in that electrical characteristics such as sensitivity are lowered.

Further, there has been proposed a method of forming a photoreceptor by laminating a charge transporting layer having an electron transporting property on the charge generating layer. Such electron transporting substances include, for example, 2, 4, 7
-Trinitro-9-fluorenone and the like are known, but this substance has carcinogenicity and poses a safety problem. In addition, JP-A-50-131941, JP-A-6-5
No. 9483, JP-A-6-123986, JP-A-9-190003, etc., cyano compounds and quinone-based compounds have been proposed, but compounds having sufficient electron transporting ability for practical use can be obtained. The fact was not.

[0010]

Accordingly, an object of the present invention is to use a new electron transporting organic material, which has never been used before, as a charge transporting material so that it can be used in high-speed copying machines and printers. It is an object of the present invention to provide a positively chargeable electrophotographic photoreceptor which can be used in the present invention.

[0011]

Means for Solving the Problems The inventors of the present invention have intensively studied various organic materials in order to achieve the above object, and have conducted many experiments. However, the use of a specific electron-transporting compound represented by the following general formula (I) or (II) as a charge-transporting substance is extremely effective in improving the electrophotographic properties of a photoreceptor. To obtain a highly sensitive photoreceptor that can be used with positive charge,
The present invention has been completed.

That is, the electrophotographic photoreceptor of the present invention comprises an electrophotographic photoreceptor having a photosensitive layer containing a charge generating substance and a charge transporting substance on a conductive substrate. I), (Wherein, R ^{1 to} R ⁴ each independently form a hydrogen atom, an alkyl or alkoxy group having 1 to 8 carbon atoms which may have a substituent, an aryl group or a ring which may have a substituent, R ⁵ and R ⁶ each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms which may have a substituent or an aryl group which may have a substituent, A ¹ represents an oxygen atom or ＝ CR ⁷ R ⁸ (wherein R ⁷ and R ⁸ each independently represent a cyano group or an alkoxycarbonyl group)
Wherein at least one kind of the electron transporting compound represented by the formula (1) is contained.

Another electrophotographic photoreceptor of the present invention comprises:
In an electrophotographic photoreceptor provided with a photosensitive layer containing a charge generating substance and a charge transporting substance on a conductive substrate, the photosensitive layer has the following general formula (II): (Wherein, R ^{10 to} R ¹³ each independently represent a hydrogen atom, an alkyl or alkoxy group having 1 to 8 carbon atoms which may have a substituent, an aryl group or a ring which may have a substituent, R ¹⁴ and R ¹⁵ each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms which may have a substituent or an aryl group which may have a substituent, A ²
Represents an oxygen atom or an electron-transporting compound represented by ＝ CR ¹⁶ R ¹⁷ (wherein R ¹⁶ and R ¹⁷ each independently represent a cyano group or an alkoxycarbonyl group). It is a feature.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Specific examples of the compounds represented by the general formulas (I) and (II) are shown below by the following structural formulas (I-
1) to (I-9) and (II-1) to (II-9).

[0015]

[0016]

The compounds represented by the general formulas (I) and (II) can be synthesized by a usual method. For example, the compounds represented by the structural formulas (I-1) and (II-1) are represented by the following structural formulas (III) and (IV): Can be easily synthesized by oxidizing the compound represented by in an organic solvent (eg, chloroform) using an appropriate oxidizing agent (eg, potassium permanganate).

Hereinafter, a specific configuration of a preferred example of the photosensitive member of the present invention will be described with reference to the drawings. 1 and 2 are schematic cross-sectional views showing various configuration examples of the photoconductor.

FIG. 1 shows an example of the configuration of a so-called single-layer photoreceptor, in which a charge generating substance and a charge transporting substance are dispersed on a conductive substrate 1 in a resin binder (binder). A photosensitive layer 2 of a layer is provided, and a coating layer (protective layer) 6 is further laminated as necessary. This single-layer type photoreceptor can be manufactured 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 on a conductive substrate. Further, if necessary, a coating layer can be applied and formed.

FIG. 2 shows an example of the configuration of a so-called laminated type photoreceptor, in which a charge generation layer 3 mainly composed of a charge generation substance and a charge transport layer 4 containing a charge transport substance are formed on a conductive substrate 1. Are sequentially provided. The laminated photoreceptor is formed 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 produced by applying and drying a dispersion obtained by dissolving or dispersing a charge transport material in a resin binder.

Although not shown, an undercoating layer can be provided between the conductive substrate and the photosensitive layer in any type of photosensitive member. The undercoat layer can be provided as needed for the purpose of preventing injection of unnecessary charges from the conductive substrate into the photosensitive layer, covering defects on the surface of the substrate, and improving the adhesiveness of the photosensitive layer. It is composed of a layer as a component, an oxide film such as alumite, and the like.

Incidentally, any type of photoreceptor of the present invention is
The charge transporting material contains at least one of the electron transporting compounds represented by formula (I) or (II).
Hereinafter, a preferred embodiment of the present invention will be described with reference to the laminated photoconductor shown in FIG. 2, but the present invention is not limited to the following specific examples.

The conductive substrate 1 serves as a support for the other layers at the same time as serving as an electrode of the photoreceptor, and may be cylindrical, plate-like, or film-like. , A metal such as nickel, or a material obtained by performing a conductive treatment on glass, resin, or the like can be used.

The charge generation layer 3 is formed by applying a material in which particles of a charge generation substance are dispersed in a resin binder as described above or by a method such as vacuum evaporation, and receives light to generate a charge. I do. In addition, it is important that the charge generation efficiency is high, and at the same time, the injected property of the generated charge into the charge transporting layer 4 is important. As the charge generating substance, phthalocyanine compounds such as metal-free phthalocyanine and titanyl phthalocyanine, pigments or dyes such as various azo, quinone, indigo, cyanine, squarylium, azurenium, and pyrylium compounds, and selenium or selenium compounds are used to form images. A suitable substance can be selected according to the light wavelength range of the exposure light source used for the exposure. Since the charge generation layer 3 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. In addition, the charge generation layer 3 can be used with a charge generation substance as a main component and a charge transport substance added thereto.

Examples of the resin binder for the charge generation layer 3 include polycarbonate, polyester, polyamide, polyurethane, vinyl chloride resin, phenoxy resin, polyvinyl butyral, diacryl phthalate resin, methacrylic acid ester polymers and copolymers thereof. Can be used in combination as appropriate.

The charge transport layer 4 is a coating film in which a charge transport material is dispersed in a resin binder. The charge transport layer 4 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. Exhibits the function of transporting charges. In the present invention, it is necessary to contain at least one kind of the electron transporting compound represented by the general formula (I) or (II) according to the present invention as such a charge transporting substance.
Other charge transport materials can be included.

As the resin binder for the charge transport layer 4, various polycarbonates, polyesters, polystyrenes, polymers and copolymers of methacrylic esters, and the like can be used.

The charge transport layer 4 contains an amine-based, phenol-based, sulfur-based, phosphite-based, phosphorous-based material for the purpose of preventing ozone deterioration, which is a hindrance in using the photoreceptor. It is also possible to include an antioxidant such as a system.

The coating layer 6 shown in FIG. 1 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 photosensitive layer is sensitive to. It is necessary that the surface charge is neutralized and eliminated by the injection of the generated charge after passing through the photosensitive layer. As a material of the coating layer 6, an organic insulating film forming material such as polyester and polyamide can be used. Also,
It is also possible to use a mixture of these organic materials and inorganic materials such as glass and SiO ₂ , and further, materials such as metals and metal oxides that reduce the electric resistance. As described above, the material of the coating layer 6 is desirably as transparent as possible in the wavelength region where the light absorption of the charge generating substance is maximum.

The film thickness of the coating layer 6 itself depends on the composition of the coating layer 6, but 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.

Incidentally, even in the case of the single-layer type photoreceptor shown in FIG. 1, at least one of the electron transporting compounds according to the present invention represented by the general formula (I) or (II) is contained in the photosensitive layer 2. It is necessary to contain, but other materials, etc.,
The same ones as used for the above-described laminated photoreceptor can be used, and there is no particular limitation. Preferably, a hole transport material is contained together with the electron transport compound of the general formula (I) as the charge transport material. As such a hole transport material, a benzidine derivative, a triphenylamine derivative, or the like is preferable. Also, in this case, the preferable addition amount
The amount of the electron transporting material is preferably 10 to 60% by weight, more preferably 15 to 50% by weight, and the hole transporting material is preferably 10 to 60% by weight, based on the entire material contained in the photosensitive layer forming coating film. Is 0 to 60% by weight, more preferably 20 to 50% by weight
It is.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments. Example 1 20 parts by weight of x-type metal-free phthalocyanine (H ₂ Pc)
100 parts by weight of the compound represented by the structural formula (I-4) is mixed with 100 parts by weight of a polyester resin (trade name: Byron 200: manufactured by Toyobo Co., Ltd.) and tetrahydrofuran (TH
F) A coating solution was prepared by kneading with a solvent for 3 hours using a mixer, and the outer diameter of the conductive substrate was 30 mm and the length was 260 m.
m, and a photosensitive layer was applied and formed so that the film thickness after drying was 15 μm, to produce a single-layer type photoreceptor.

Example 2 2 parts by weight of x-type metal-free phthalocyanine (H ₂ Pc), 40 parts by weight of the compound represented by the above structural formula (I-1), And a polycarbonate resin (PCZ-200, manufactured by Mitsubishi Gas Chemical Co., Ltd.)
100 parts by weight were kneaded with methylene chloride for 3 hours using a mixer to prepare a coating solution, and a photosensitive layer was formed on an aluminum support so that the film thickness after drying was about 20 μm. A photoreceptor was prepared.

Example 3 2 parts by weight of titanyl phthalocyanine (TiOPc), 40 parts by weight of the compound represented by the structural formula (II-1), 60 parts by weight of a benzidine derivative represented by the formula and 100 parts by weight of a polycarbonate resin (BP-PC, manufactured by Idemitsu Kosan Co., Ltd.) are kneaded with methylene chloride for 3 hours by a mixer to prepare a coating liquid, A photosensitive layer was applied and formed on the body so that the film thickness after drying was about 20 μm, thereby producing a single-layer type photosensitive body.

Example 4 In Example 3, the following formula was used instead of titanyl phthalocyanine: And using the above-mentioned structural formula (I-2) instead of the compound of the above-mentioned structural formula (II-1).
A single-layer type photoreceptor was prepared in the same manner as in Example 3 except that the compound was used.

Example 5 70 parts by weight of titanyl phthalocyanine (TiOPc)
A coating solution was prepared by kneading 30 parts by weight of a vinyl chloride copolymer (trade name: MR-110, manufactured by Nippon Zeon Co., Ltd.) with methylene chloride for 3 hours using a mixer to form a coating solution of about 1 μm on an aluminum support. To form a charge generation layer. Next, 100 parts by weight of the compound represented by the structural formula (II-2) and a polycarbonate resin (PCZ-
200 parts of Mitsubishi Gas Chemical Co., Ltd.) and 0.1 part by weight of silicone oil were mixed with methylene chloride,
This coating solution was applied on the charge generation layer so as to have a thickness of about 7 μm to form a charge transport layer, thereby producing a laminated photoreceptor.

Example 6 In Example 3, the following formula was used instead of titanyl phthalocyanine: A bisazo pigment represented by the formula (II)
A single-layer photoreceptor was prepared in the same manner as in Example 3, except that the compound of the structural formula (II-4) was used instead of the compound of -1).

Example 7 In Example 3, the following formula was used instead of titanyl phthalocyanine: A bisazo pigment represented by the formula (II)
A single-layer type photoreceptor was prepared in the same manner as in Example 3, except that the compound of the structural formula (II-5) was used instead of the compound of -1).

Evaluation of Photoreceptor The electrophotographic characteristics of the photoreceptor prepared in the above-mentioned examples were evaluated by the following methods. The initial surface potential when the photoreceptor surface is positively charged by performing a corona discharge of +4.5 kV on the photoreceptor in a dark place is set to Vs (V). Surface potential Vd when held
(V) was measured, and subsequently, the illuminance 100
A time (second) until the surface potential Vd is reduced to half by irradiating white light of looks (lx) is obtained, and the sensitivity E _1/2 (lx ·
s).

Also, a white light having an illuminance of 100 lux
The surface potential upon irradiation for 2 seconds was defined as residual potential Vr (V). In Examples 1 to 5, since high sensitivity at a long wavelength can be expected, electrophotographic characteristics when monochromatic light having a wavelength of 780 nm was used were also measured. That is, the same measurement is performed up to Vd, and then a 1 μW monochromatic light (780 nm) is irradiated instead of white light, and a half-attenuation exposure (μJ / cm
² ) was determined, and the residual potential Vr (V) when this light was irradiated on the photoreceptor surface for 10 seconds was measured. The results of the measurement are shown in Table 1 below.

[0041]

[Table 1]

[0042]

As described above, according to the present invention, the electron transporting compound represented by the above general formula (I) or (II) is used as a charge transporting substance in a photosensitive layer provided on a conductive substrate. By using this, it is possible to obtain a photosensitive member having high sensitivity and excellent electrical characteristics in positive charging. In addition, a suitable substance can be selected as the charge generating substance in accordance with the type of the exposure light source. Obtainable. Furthermore, if necessary, a coating layer can be provided on the surface to improve durability.

[Brief description of the drawings]

FIG. 1 is a schematic structural cross-sectional view of a single-layer type electrophotographic photoreceptor of one example of the present invention.

FIG. 2 is a schematic structural cross-sectional view of a laminated electrophotographic photosensitive member according to another example of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 conductive substrate 2 photosensitive layer 3 charge generation layer 4 charge transport layer 5 photosensitive layer (lamination) 6 covering layer (protective layer)

Claims (2)

[Claims] 1. An electrophotographic photosensitive member having a photosensitive layer containing a charge-generating substance and a charge-transporting substance on a conductive substrate, wherein the photosensitive layer has the following general formula (I): (Wherein, R ^{1 to} R ⁴ each independently form a hydrogen atom, an alkyl or alkoxy group having 1 to 8 carbon atoms which may have a substituent, an aryl group or a ring which may have a substituent, R ⁵ and R ⁶ each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms which may have a substituent or an aryl group which may have a substituent, A ¹ represents an oxygen atom or ＝ CR ⁷ R ⁸ (wherein R ⁷ and R ⁸ each independently represent a cyano group or an alkoxycarbonyl group)
A photoconductor for electrophotography, comprising at least one of the electron transporting compounds represented by the formula: 2. An electrophotographic photoreceptor having a photosensitive layer containing a charge generating substance and a charge transporting substance on a conductive substrate, wherein the photosensitive layer has the following general formula (II): (Wherein, R ^{10 to} R ¹³ each independently represent a hydrogen atom, an alkyl or alkoxy group having 1 to 8 carbon atoms which may have a substituent, an aryl group or a ring which may have a substituent, R ¹⁴ and R ¹⁵ each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms which may have a substituent or an aryl group which may have a substituent, A ²
Represents an oxygen atom or an electron-transporting compound represented by ＝ CR ¹⁶ R ¹⁷ (wherein R ¹⁶ and R ¹⁷ each independently represent a cyano group or an alkoxycarbonyl group). A photoconductor for electrophotography, characterized by