JPH04101152A - Electrophotographic sensitive body and manufacture of same - Google Patents

Abstract

PURPOSE:To enable photosensitivity of a photosensitive body to be controlled by rendering concentration of an electric charge transfer material lower on the surface of a charge transfer layer than in its inside. CONSTITUTION:A charge generating layer and the charge transfer layer are successively laminated on a conductive substrate, and the concentration of the charge transfer material on the surface of the charge transfer layer is made lower than that in its inside. When the laminate type photosensitive body is formed by coating, a mixture of the charge generating material and the binder or a mixture of the charge transfer material and the binder is dissolved in a solvent to form a coating fluid, and the solvent for dissolving the binder is made different by the kind of the binder, and it is preferred to use the solvent not disolving the underlayer, thus permitting the photosensitivity of the photosensitive body to be controlled only by adjusting drying temperature of the charge transfer layer and accordingly the electrophotographic sensitive body high in sensitivity to be easily obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrophotographic photoreceptor used in copying machines, LD printers, LED printers, etc., and a method for manufacturing the same.

[Prior Art] Conventionally, inorganic compounds such as selenium, cadmium sulfide, and zinc oxide have been widely used as photoconductive materials for electrophotographic photoreceptors. However, while these inorganic compounds have many advantages, they also have various disadvantages. For example, selenium has difficult manufacturing conditions, high manufacturing costs, and tends to crystallize due to temperature and humidity. Cadmium sulfide has poor moisture resistance;
Furthermore, zinc oxide has problems with mechanical strength such as hardness and wear resistance. Furthermore, since these contain chalcogen and heavy metals, there is a risk of developing a pollution problem.

In recent years, in order to overcome the drawbacks of these inorganic compounds, research and development efforts have been actively conducted to develop electrophotographic photoreceptors using various organic photoconductive compounds such as poly-N-vinylcarbazole. Such an organic compound-based electrophotographic photoreceptor has the advantage that it is easier to form a film than an inorganic compound-based electrophotographic photoreceptor, and can provide a highly productive and inexpensive photoreceptor. However, with regard to photoconductive polymers such as poly-N vinyl carbazole, filmability, flexibility, adhesion, etc. are poor when using the polymer alone, and plasticizers, binders, etc. are added to improve these drawbacks. However, this caused problems such as a decrease in photosensitivity and an increase in residual potential.

Recently, there has been active development of functionally separated laminated photoreceptors that separate the charge generation function and charge transport function. Increasingly, the charge transport layer is used as a charge transport layer. In particular, those having good photosensitivity using hydrazone derivatives as a medium have been obtained. In this case, performance such as surface hardness, flexibility, and adhesiveness can be improved by selecting a binder polymer, so a photoreceptor with even better performance can be obtained.

The photosensitivity of a functionally separated photoreceptor is determined by: (a) photocharge generation ability in the charge generation layer, (b) charge injection efficiency from the charge generation layer to the charge transport layer, and (C) charge in the charge transport layer. It is determined by the product of three transport capacities, and development activities are being carried out with the goal of improving each efficiency.

[Problems to be Solved by the Invention] Currently, the correlation between the photosensitivity of a functionally separated photoreceptor in which a charge generation layer and a charge transport layer are laminated on a conductive support and the drying temperature of the charge transport layer is not clearly understood. do not have.

Therefore, the inventors of the present invention have conducted extensive studies on the drying temperature conditions of the charge transport layer in order to clarify this correlation and at the same time improve the photosensitivity of the photoreceptor.

[Means for solving the problem] As a result, it was found that by changing the drying temperature of the charge transport layer, a concentration gradient is generated in the charge transport substance in the charge transport layer. , drying temperature conditions that make the concentration of the charge transport substance on the surface of the charge transport layer lower than the concentration inside the charge transport layer in a photoreceptor in which charge transport layers are laminated in this order, and a conductive support. In the case of a photoreceptor in which a charge transport layer and a charge generation layer are laminated in this order, the drying temperature conditions are such that the concentration of the charge transport substance at the interface between the charge transport layer and the charge generation layer is higher than the concentration inside the charge transport layer. It was discovered that the intended purpose could be achieved, and the present invention was completed.

That is, the gist of the present invention is that in a laminated electrophotographic photoreceptor in which a charge generation layer and a charge transport layer are laminated in this order on a conductive support, the concentration of a charge transport substance on the surface of the charge transport layer is lower than that of the charge transport layer. An electrophotographic photoreceptor characterized in that the density is lower than that in the interior of the charge transport layer, and a laminated electrophotographic photoreceptor in which a charge transport layer and a charge generation layer are laminated in this order on a conductive support. An electrophotographic photoreceptor characterized in that the concentration of the charge transport substance at the interface of the charge generation layer is higher than the concentration inside the charge transport layer, and a method for producing a laminated electrophotographic photoreceptor, in which the charge is A method for producing an electrophotographic photoreceptor, characterized in that the photosensitivity of the photoreceptor is adjusted by creating a concentration gradient in the charge transport substance in the charge transport layer by adjusting the drying temperature of the transport layer.

The present invention will be explained in detail below.

In general, the photosensitivity of a functionally separated laminated photoreceptor depends on (a) the photocharge generation ability in the charge generation layer, (b) the charge injection efficiency from the charge generation layer to the charge transport layer, and <c> the charge in the charge transport layer. It is known that transport capacity is controlled by three products. Therefore, these three efficiencies (a), (b),
If even one of (C) is improved, the photosensitivity of the photoreceptor can be increased.

In order to adjust the photosensitivity of a function-separated layered photoreceptor, the present inventor investigated means for controlling two efficiencies: (b) charge injection efficiency and (C) charge transport ability, and determined the drying temperature of the charge transport layer. I found a way to adjust it.

Specifically, the boiling point of the organic solvent contained in the paint used when forming the charge transport layer of the multilayer photoreceptor by coating is used as an index for setting the drying temperature of the charge transport layer. As a result, when the drying temperature of the charge transport layer changes to above or below the boiling point of the organic solvent contained in the paint, a change appears in the concentration gradient of the charge transport substance in the charge transport layer, as shown in Figure 1. It was found that the concentration of the charge transport substance on the surface of the charge transport layer differs depending on the drying temperature above or below the boiling point of the organic solvent. This is presumably caused by the difference in the mobility of the charge transport substance due to the difference in thermal energy during drying of the charge transport layer. As a method for detecting the concentration of the charge transport substance on the surface of the charge transport layer, the ES shown in Figure 1 is used.
In addition to the CA surface analysis method, the FT-IR-ATR method and the like can be mentioned.

Therefore, (b) is the governing factor of photosensitivity of the laminated photoconductor.
When we investigated the charge injection efficiency and (C) charge transport ability, we found that the two efficiencies (b) and (C) changed by adjusting the drying temperature of the charge transport layer.

For example, in an electrophotographic photoreceptor in which a charge generation layer and a charge transport layer are laminated in this order on a conductive support, as the drying temperature of the charge transport layer increases, (b) charge injection efficiency, (C) charge transport ability ( Figure 2) decreased. This is presumed to be due to the difference in the concentration gradient of the charge transport substance in the charge transport layer.

(b) Methods for measuring charge injection efficiency from the charge generation layer to the charge transport layer include the xerographic ink method and photoacoustic spectroscopy (PAS).
(c) The TOF method (FIG. 2) is well known as a method for measuring the charge transport ability in the charge transport layer.

Based on the above knowledge, a charge generation layer on a conductive support,
In a laminated electrophotographic photoreceptor in which charge transport layers are laminated in this order, the photosensitivity of the photoreceptor is improved by making the concentration of the charge transport substance on the surface of the charge transport layer lower than the concentration inside the charge transport layer. An electrophotographic photoreceptor characterized by an improved charge transport layer and a laminated electrophotographic photoreceptor in which a charge transport layer and a charge generation layer are laminated in this order on a conductive support. Production of an electrophotographic photoreceptor and a laminated electrophotographic photoreceptor, characterized in that the photosensitivity of the photoreceptor is improved by making the concentration of a charge transporting substance higher than the concentration inside the charge transport layer. Regarding a method for producing an electrophotographic photoreceptor, the process comprising adjusting the drying temperature of the charge transport layer to create a concentration gradient in the charge transport substance in the charge transport layer, thereby adjusting the photosensitivity of the photoreceptor. I ended up inventing it.

As the material of the conductive support used in the photoreceptor of the present invention, for example, metals such as aluminum, copper, zinc, stainless steel, chromium, titanium, nickel, molybdenum, vanadium, indium, gold, and platinum, or alloys thereof can be used. Examples include paper and plastic films coated with, vapor-deposited, or laminated with conductive polymers, conductive compounds such as indium oxide, metals such as aluminum, palladium, and gold, or alloys thereof.

Examples of charge-generating materials used in the photosensitive layer include azo pigments, quinone pigments, perylene pigments, indigo pigments, thioindigo pigments, hisbenzimidazole pigments, phthalocyanine pigments, quinacridone pigments, and quinoline pigments. , lake pigments, azo lake pigments, anthraquinone pigments, oxazine pigments, dioxazine pigments, triphenylmethane pigments, azulenium dyes, sufuniarium dyes, pyrylium dyes, triallylmethane dyes, xanthine dyes, thiazine dyes, n-anine dyes, etc. Examples include various organic pigments and dyes, as well as inorganic materials such as amorphous silicon, amorphous selenium, tellurium, selenium-tellurium alloys, cadmium sulfide, antimony sulfide, zinc oxide, and zinc sulfide. These materials are dispersed in a binder resin and applied onto a conductive support, and are used after being formed into a film by means such as vacuum evaporation, sputtering, and CVD.

The charge-generating substance is not limited to those listed here (but can be used alone or in combination of two or more types).

Further, charge transport materials are generally classified into two types: materials that transport electrons and materials that transport holes, and both can be used in the photoreceptor of the present invention.

Examples of electron transport substances include chloranil, bromoanil, tetracyanoethylene, tetracyanoquinodimethane, 2. 4. 7-t') Nitro-9 fluorenone, 2
．． 4. 5. 7-tetranitro 9-fluorenone,
9-dicyanomethylene-2゜4.7-trinitrofluorenone, 9-dicyanomethylene-2,4,5,7-tetranitrofluorenone, 2. 4. 5. 7-tetranitroxanthone, 2. 4. 8-trinidrothioxanthone, tetranitrocarbazole, 2,3-dichloro-5°6-dicyanobenzoquinone, 2. 4. 7-
Examples thereof include organic compounds such as dolinito-o-9,10-phenanthrenequinone, tetrachlorophthalic anhydride, and diphenoquinone derivatives.

Examples of the hole transport substance include pyrene, N-ethylcarbazole, N-isopropylcarbazole, N-phenylcarbazole, N-methyl-2-phenylhydrazino-3-methylidene-9-ethylcarbazole, N-
, N-diphenylhydrazino-3-methylidene-9
-ethylcarbazole, p-N,N-dimethylaminobenzaldehyde diphenylhydrazone, p-N,N-dimethylaminobenzaldehyde diphenylhydrazone,
hydrazones such as p-N, N-diphenylaminobenzaldehyde diphenylhydrazone, 2.5-bis(p
-diethylaminophenyl) 1, 3. 4-oxadiazole, 1-phenyl 3-(p-diethylaminostyryl)-5-(p=nidiethylaminophenylpyrazoline and other pyrazolines, triphenylamine, N,
N, N'N'-tetraphenyl-1,1'-diphenyl-4,4'-diamine, N, N'-diphenyl-N.

Examples include N'-bis(3-methylphenyl)-1,1'biphenyl-4,4'-diamine.

The charge transport materials are not limited to those listed here, and can be used alone or in combination of two or more kinds.

As the binder, it is preferable to use a hydrophobic polymer capable of forming an electrically insulating film. Examples of such high molecular weight polymers include polycarbonate,
Polyester, methacrylic resin, acrylic resin, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyvinyl acetate, styrene-butadiene copolymer, vinylidene chloride-acrylonitrile polymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate- Maleic anhydride copolymer, silicone resin, silicone-alkyd resin, phenol-formaldehyde resin, styrene-
Examples include, but are not limited to, alkyd resins, poly-N-vinylcarbazole, polyvinyl butyral, polyvinyl formal, and polysulfone. These binders may be used alone or in combination of two or more.

Moreover, additives such as plasticizers, sensitizers, and surface modifiers can also be used together with these binders.

Examples of plasticizers include biphenyl, chlorinated biphenyl,
Examples include 0-terphenyl, dibutyl phthalate, diethylene glycol phthalate, dioctyl phthalate, triphenyl phosphoric acid, methylnaphthalene, benzophenone, chlorinated paraffin, polypropylene, polystyrene, and various fluorohydrocarbons.

Examples of the sensitizer include chloranil, tetracyanoethylene, methyl violet, rhodamine B1 cyanine dye, merocyanine dye, biryllium dye, and thiapyrylium dye.

Examples of the surface modifier include silicone oil and fluororesin.

Furthermore, in the present invention, in order to improve the adhesion between the conductive support and the photosensitive layer and to prevent the injection of free charges from the support to the photosensitive layer, it is necessary to add a layer between the conductive support and the photosensitive layer. An adhesive layer or barrier layer can also be provided depending on the requirements. Materials used for these layers include, in addition to the polymer compound used in the binder, casein, gelatin, polyvinyl alcohol, ethyl cellulose, phenolic resin, polyamide, carboxy-methyl cellulose, vinylidene chloride polymer latex, polyurethane, aluminum oxide, Examples include tin oxide and titanium oxide.

When forming a laminated photoreceptor by coating, a paint is used in which a mixture of the charge generating agent and charge transporting substance described above in a binder is dissolved in a solvent, but the solvent used to dissolve the binder varies depending on the type of binder. However, it is preferable to select one from among those that do not dissolve the lower layer. Specific examples of organic solvents include alcohols such as methanol, ethanol, and n-propanol; ketones such as acetone, methyl ethyl ketone, and cyclohexanone;
, N-dimethylformamide, N,N-dimethylacetamide, and other amides; tetrahydrofuran, dioxane, methyl cellosolve, and other ethers; methyl acetate,
Esters such as ethyl acetate; sulfoxides and sulfones such as dimethyl sulfoxide and sulfolane; aliphatic halogenated hydrocarbons such as methylene chloride, chloroform, carbon tetrachloride, and trichloroethane; benzene, toluene, xylene, monochlorobenzene, dichlorobenzene, etc. Examples include aromatics.

As the coating method, coating methods such as dip coating, spray coating, spinner coating, bead coating, wire bar coating, blade coating, roller coating, and curtain coating can be used.

[Example] Hereinafter, the present invention will be explained in more detail with reference to Examples.
Therefore, the present invention is not limited to the examples.

In addition, "parts" in the examples indicate "parts by weight."

A charge generation layer was formed.

Example 1 Two parts of commercially available soluble nylon (trade name: rCM-4000 manufactured by Toshi) were mixed with 75 parts of methanol, 20 parts of toluene, and n-
It was dissolved in 5 parts of butanol and coated on the surface of an aluminum drum to a film thickness of 800A after drying to form a base layer.

Next, 8 parts of titanyl phthalocyanine pigment and commercially available butyral resin (product name: "S-LEC BH-3J Sekisui Chemical Co., Ltd."
1. 1. 2-1 In addition to 300 parts of chlorothane and 200 parts of dichloromethane, a paint obtained by dispersing it in a sand mill is applied on the base layer to a film thickness of 2000 A after drying. 17 parts of a hydrazone compound of structural formula (1), which is a transport substance, 19 parts of a commercially available polycarbonate resin (trade name: "Nipilon Z-200J manufactured by Mitsubishi Gas Chemical Company Ltd."), and 0.85 parts of bis-t-butylhydroxytoluene (BIT). was dissolved in 60 parts of dioxane (boiling point: 101°C) and 40 parts of dichloromethane (boiling point: 40°C), and the resulting paint was applied onto the charge generation layer, and the mixture was heated to a temperature higher than the boiling point of dioxane (101°C), which is a high boiling point solvent. A photoreceptor was prepared by drying at a low temperature (70° C.) for 1 hour to form a charge transport layer with a thickness of 18 μm.

Next, the drying temperature of the charge transport layer is 101, which is the boiling point of dioxane.
A photoreceptor was produced under exactly the same conditions except that the temperature was higher than 130°C.

Here, a photoreceptor obtained by drying at a low temperature was designated as Example 1, and a photoreceptor obtained by drying at a high temperature was designated as Comparative Example 1.

The electrophotographic properties of the photoreceptor thus prepared were tested using an LD printer with a process speed of 6786 mm/min at low temperature and low humidity (5°C/20% RH) and at room temperature and normal humidity (23°C/min).
°C150%RH), high temperature and high humidity (40'C/80%RH)
) Measurements were made under three environments. However, the exposure for photosensitivity measurement was performed using a semiconductor laser with a wavelength of 780 nm at 0.7 mW/cm.
'(0,6 mW/cm" at the photoreceptor surface)
It was performed with the intensity of The results are shown in Table 1. Here ■.

is chargeability, ■ is sensitivity potential, ]■. -V L l represents photosensitivity.

As is clear from the table, the photoreceptor obtained by drying at a temperature lower than the boiling point of dioxane, which is a high boiling point solvent, had improved photosensitivity compared to the photoreceptor dried at a high temperature.

Table 1 Example 2 Structural Formula (2) A base layer and a charge generation layer were formed by the same method as in Example 1, and 17 parts of a hydrazone compound of Structural Formula (2), which is a hole transport material, was added on top of the base layer and a charge generation layer by the same method as in Example 1. 19 parts of polycarbonate resin (trade name: "Nipiron Z-200J" manufactured by Mitsubishi Gas Chemical) and 0.8 parts of bis-t-butylhydroxytoluene (BIT).
A coating obtained by dissolving 5 parts of monochlorobenzene (boiling point: 132°C) in 60 parts of monochlorobenzene (boiling point: 132°C) and 40 parts of dichloromethane (boiling point: 40°C) was applied on the charge generation layer, and a coating material obtained by dissolving 5 parts of monochlorobenzene (boiling point: 132°C) was applied onto the charge generation layer. A photoreceptor was prepared by drying for 1 hour at a temperature (110°C) lower than the boiling point of 132°C to form a charge transport layer with a thickness of 17 μm. This photoreceptor will be referred to as Example 2.

Next, a photoreceptor was produced under exactly the same conditions except that the drying temperature of the charge transport layer was higher (140°C) than the boiling point of monochlorobenzene, 132°C. This photoreceptor is referred to as Comparative Example 2.

The electrophotographic properties of the thus obtained photoreceptor were measured in the same manner as in Example 1. The results are shown in Table 2.

Regarding this result as well, the photoreceptor dried at a temperature lower than the boiling point of monochlorobenzene, which is a high boiling point solvent, had higher photosensitivity than the one dried at a high temperature.

Table 2 [Effects of the Invention] According to the present invention, in a function-separated electrophotographic photoreceptor in which a charge generation layer and a charge transport layer are laminated on a conductive support, the drying temperature of the charge transport layer can be adjusted. The photosensitivity of the photoreceptor can be adjusted, and a highly sensitive electrophotographic photoreceptor and a method for manufacturing the same can be provided by extremely easy means.

[Brief explanation of drawings]

FIG. 1 is a graph showing the depth-profi of the charge transport material concentration in the charge transport layer of an electrophotographic photoreceptor, and FIG. Drying temperature (°C) of charge transport layer and charge drift mobility (cm) in sequentially laminated electrophotographic photoreceptor
” / sec -V). Agent Patent Attorney Katsutoshi Takahashi Procedural Amendment (Voluntary) February 27, 1991 Commissioner of the Patent Office Toshi Uematsu Toshiaki Uematsu Display of the Case 1990 Patent No. 219727 2, Name of the invention Electrophotographic photoreceptor and its manufacturing method 3, Relationship with the person making the amendment Patent applicant No. 35-58 Sakashita 3-chome, Itabashi-ku, Tokyo (288) Inu Nippon Ink Representative of Kagaku Kogyo Co., Ltd.
Shigeru Kuni Kawamura 4, Agent 6-20-3 Nihonbashi, Chuo-ku, Tokyo 103, Statement of Contents of Amendment No. 19 Jisetsu 1 Revise [mW/cm2 paddy in line 13 to "mWJ". Line 2 and Specification No. 1 5. Detailed explanation of one invention in the specification to be amended - ○ Column procedural amendment (voluntary) March 5, 1991 Commissioner of the Patent Office Toshi Uematsu Toshi 1. Indication of the case 1990 Patent No. 219727 No. 2, Name of the invention Electrophotographic photoreceptor and its manufacturing method 3, Relationship with the person making the amendment Patent applicant No. 35-58 Sakashita, Itabashi-ku, Tokyo (288> Inu Nippon Ink Chemical Representative of Kogyo Co., Ltd.
Shigeru Kuni Kawamura 4, Agent: 3-7-20-6, Nihonbashi, Chuo-ku, Tokyo 103, details of the amendment as per the attached sheet. Figure May 2nd, 1991

Claims (1)

[Scope of Claims] 1. In an electrophotographic photoreceptor in which a charge generation layer and a charge transport layer are laminated in this order on a conductive support, the concentration of a charge transport substance on the surface of the charge transport layer is lower than that of the charge transport layer. An electrophotographic photoreceptor characterized in that the density is lower than that inside the electrophotographic photoreceptor. 2. In an electrophotographic photoreceptor in which a charge transport layer and a charge generation layer are laminated in this order on a conductive support, the concentration of the charge transport substance at the interface between the charge transport layer and the charge generation layer is lower than that inside the charge transport layer. An electrophotographic photoreceptor characterized by having a density greater than that at . 3. In a method for manufacturing an electrophotographic photoreceptor in which a charge generation layer and a charge transport layer are laminated on a conductive support, the concentration of the charge transport substance in the charge transport layer is adjusted by adjusting the drying temperature of the charge transport layer. 1. A method for producing an electrophotographic photoreceptor, the method comprising providing a gradient to adjust the photosensitivity of the photoreceptor.