JPH0619144A - Electrophotographic sensitive body and its production - Google Patents

Abstract

PURPOSE:To provide the electrophotographic sensitive body having a photosensitive layer of a lamination type which has the excellent adhesion to a conductive base, is not degraded in sensitivity and not increased in residual potential in spite of repetitive use over a long period of time and can form high-quality images and its process for production. CONSTITUTION:This electrophotographic sensitive body is constituted by using a diphenic acid aramid resin having the repeating unit expressed by general formula (the symbols in the formula are as stated in specification) as a binder resin for a charge generating layer. The process for production consists in forming the charge generating layer from a coating liquid contg. a diphenic acid aramid resin and a solvent which dissolves this diphenic acid aramid resin and forming a charge transfer layer on this charge generating layer by applying a coating liquid contg. the binder resin and a solvent which dissolves this binder resin but does not dissolve the diphenic acid aramid resin thereon.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photosensitive member used in an image forming apparatus using an electrophotographic method such as an electrostatic copying machine and a laser beam printer, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Electrophotographic methods such as the Carlson process use a corona discharge to uniformly charge the surface of an electrophotographic photosensitive member and a charged electrophotographic photosensitive member surface. An exposure step of forming an electrostatic latent image on the surface by exposure, a developer is brought into contact with the formed electrostatic latent image, and toner contained in the developer causes
A developing process that visualizes the electrostatic latent image into a toner image, a transfer process that transfers the toner image to paper, a fixing process that fixes the transferred toner image, and a residual toner on the photoconductor after the transferring process. And a cleaning step for removing the toner.

Recently, the electrophotographic photosensitive member used in the above-mentioned electrophotographic method is replaced with a main component containing an inorganic photoconductor such as selenium or cadmium sulfide, which is difficult to handle due to toxicity. Various so-called organic photoconductors using organic photoconductive compounds with low toxicity have been proposed. Such an organic photoreceptor has the advantages that it has good processability, is easy to manufacture, and has a high degree of freedom in functional design.

As such an organic photoreceptor, generally,
A function-separated photosensitive layer including a charge generation material that generates an electric charge by light irradiation and a charge transport material that transfers the generated electric charge is used. The function-separated type photosensitive layer includes a laminated type and a single layer type. The laminated type photosensitive layer includes a charge generation layer containing a charge generation material, a binder resin, etc., a charge transport material and a binder. A charge transport layer containing a resin and the like is laminated on a conductive substrate.

Whether the sensitivity characteristics of the laminated photosensitive layer are good or bad is affected by the performance of the charge transport layer, but the effect of the performance of the charge generation layer cannot be ignored. It is known that the performance of the charge generation layer depends largely on the charge generation material, but also depends on the binder resin. For example, when the binder resin acts as a carrier trap, the sensitivity of the photoconductor is lowered and the residual potential is increased.

Further, since a relatively large amount of the charge generating material is added to the charge generating layer, the adhesion strength between the charge generating layer and the conductive substrate tends to be lower than the strength of only the conductive substrate and the binder resin. There is. When the charge generation layer has poor adhesion to the conductive substrate, repeated use of the photoconductor for a long period of time deteriorates the charging property and the sensitivity property with the decrease in the adhesion to the conductive substrate, resulting in a high quality image. The problem arises that it is difficult to form.

It is the binder resin of the charge generation layer that substantially controls the adhesion to the conductive substrate. Therefore, in order to provide the charge generation layer with sufficient adhesion strength, it is necessary to use a binder resin having particularly excellent adhesion to the conductive substrate. Laminated photoreceptors are usually manufactured by forming a charge generation layer on a conductive substrate, applying a coating solution for the charge transport layer by dip coating, etc., and then drying it to form the charge transport layer. It Therefore, the binder resin forming the charge generation layer is required not to be dissolved in the solvent used in the coating liquid for the charge transport layer.

That is, when the charge generating layer is dissolved when the coating liquid for the charge transport layer is applied, the charge generating material and the binder resin are mixed into the coating liquid for the charge transport layer to contaminate the coating liquid. However, it is not possible to produce a photoreceptor having stable characteristics. In addition, when the charge generation layer is dissolved, the film thickness of the charge generation layer itself is reduced, so that the sensitivity of the photoreceptor is lowered and desired photoreceptor characteristics cannot be obtained. Therefore, it is important that the binder resin used for the charge generation layer does not dissolve in the solvent used for the coating liquid for the charge transport layer.

Further, the fact that the binder resin used for the charge generating layer does not adversely affect the dispersibility of the coating liquid for the charge generating layer is
It is important in producing a stable photoconductor. To summarize the above, the binder resin of the charge generation layer does not adversely affect the photoreceptor performance, has good adhesion to the conductive substrate, dissolves in the solvent used to coat the charge generation layer,
It does not dissolve in the solvent for the charge transport layer applied on top of it, does not interfere with the dispersion of the charge generating material in the coating liquid of the charge generating layer prepared by solvent, charge generating material, binder resin, etc. Is required.

As the binder resin for the charge generation layer, phenol resin, acrylic resin, polyester, polycarbonate, nylon, polyvinyl acetate, polyvinyl chloride and the like have been proposed. However, these resins have the above performance,
Not all can be satisfied. For example, nylon and polycarbonate have excellent electrical characteristics,
Poor adhesion to the conductive substrate.

Acetal resins such as polyvinyl butyral and polyvinyl formal are known to satisfy the above-mentioned performance to some extent. However, the photoconductor using an acetal resin as the binder resin of the charge generation layer has a problem that the sensitivity is slightly lowered. For this reason,
Under the present circumstances, the conventional electrophotographic photoreceptor using the above-mentioned conventional binder resin in the charge generation layer cannot sufficiently exhibit the excellent characteristics of the charge generation material and the charge transport material.

The present invention has been made in view of the above circumstances, has excellent adhesion to a conductive substrate, and does not decrease in sensitivity or increase in residual potential even after repeated use over a long period of time.
An object of the present invention is to provide an electrophotographic photosensitive member having a laminated photosensitive layer capable of forming a high quality image, and a manufacturing method thereof.

[0013]

The electrophotographic photosensitive member of the present invention for solving the above problems comprises a charge generating layer containing a charge generating material and a charge transporting material on a conductive substrate. And a charge transport layer, wherein the charge generation layer serves as a binder resin represented by the general formula (1):

[0014]

[Chemical 2]

(Wherein R ¹ , R ² , R ³ , R ⁴ and R ⁵ are the same or different and represent an alkyl group or an alkoxy group, and R ⁶ , R ⁷ , R ⁸ and R ⁹ are the same or different and are hydrogen. It represents an atom or an alkyl group, and a, b, c, and d are the same or different and are 0 to 4)).

Further, in the production method of the present invention for producing the electrophotographic photosensitive member of the present invention, the charge generating material and the repeating unit represented by the general formula (1) are provided on the conductive substrate. A coating solution containing the diphenic acid-type aramid resin and a solvent that dissolves the diphenic acid-type aramid resin is applied and dried to form a charge generation layer, and then a charge transport material and a binder are formed on the charge generation layer. A charge transport layer is formed by applying a coating solution containing a binder resin and a solvent that dissolves the binder resin but does not dissolve the diphenic acid aramid resin, and then dry the coating solution.

In the electrophotographic photosensitive member of the present invention,
The diphenic acid-based aramid resin represented by the general formula (1), which is used as the binder resin for the charge generation layer, satisfies all of the above performances (1) to (3). Therefore, the electrophotographic photosensitive member of the present invention has excellent adhesion to a conductive substrate, and is capable of forming a high-quality image without deterioration in sensitivity or increase in residual potential even after repeated use over a long period of time. The mold is provided with a photosensitive layer.

The mechanism by which the diphenic acid aramid resin represented by the general formula (1) satisfies all the properties required for the binder resin has not been clarified so far, but it is essentially heat-resistant. , Excellent impact resistance, etc., and by introducing a bent portion based on diphenic acid in the structure of a chemically stable aramid resin, flexibility, adhesion, solvent solubility, etc. are improved, It is presumed to be the main cause.

The above diphenic acid aramid resin is
Tetrahydrofuran, normal methylpyrrolidone, dimethylformamide and the like have a very good solubility in polar solvents, but hardly soluble in nonpolar solvents such as benzene, toluene, xylene, etc. It is easy to select a solvent for the charge transport layer and the charge generation layer. Therefore, according to the manufacturing method of the present invention in which the solvent used for the charge transport layer coating liquid and the charge generating layer coating liquid is selected, the charge generating material and the binder resin are mixed in the charge transport layer coating liquid. It is possible to efficiently manufacture the electrophotographic photosensitive member of the present invention without contaminating the coating solution and reducing the film thickness of the charge generation layer itself.

In the diphenic acid aramid resin represented by the general formula (1), the alkyl group is, for example, methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, t-butyl group, pentyl group. Examples thereof include alkyl groups having 1 to 6 carbon atoms such as groups and hexyl groups.
Examples of the alkoxy group include a methoxy group, an ethoxy group, an isopropoxy group, a butoxy group, a t-butoxy group,
A hexyloxy group and the like can be mentioned.

Specific examples of the diphenic acid aramid resin include compounds having repeating units represented by the following formulas (11) and (12).

[0022]

[Chemical 3]

[0023]

[Chemical 4]

The diphenic acid type aramid resin represented by the general formula (1) is obtained by using the diphenic acid dichloride derivative (a) and the aromatic diamine (b) in the case of a usual aramid resin as shown in the following reaction formula. It is produced by copolymerizing in the same manner as.

[0025]

[Chemical 5]

Examples of the charge generating material that constitutes the charge generating layer together with the diphenic acid aramid resin include azo pigments, perylene pigments, anthanthrone pigments, phthalocyanine pigments, indigo pigments, triphenylmethane pigments and slene. Various conventionally known charge generating materials such as pigments, toluidine pigments, pyrazoline pigments, quinacridone pigments and dithioketopyrrolopyrrole pigments can be used. The above charge generating materials are used alone or in combination of two or more.

It should be noted that the above-mentioned charge generation layer may be added with another binder resin used in the charge transport layer described later within a range not impairing the characteristics of the diphenic acid aramid resin. The charge transport layer laminated on the charge generation layer is formed by dispersing a charge transport material in a binder resin, and examples of the charge transport material include tetracyanoethylene, 2,
Fluorenone compounds such as 4,7-trinitro-9-fluorenone, 2,4,8-trinitrothioxanthone,
Nitro compounds such as dinitroanthracene, succinic anhydride, maleic anhydride, dibromomaleic anhydride, 2,5
-Oxadiazole compounds such as di (4-dimethylaminophenyl) -1,3,4-oxadiazole, 9-
Styryl compounds such as (4-diethylaminostyryl) anthracene, carbazole compounds such as polyvinylcarbazole, pyrazoline compounds such as 1-phenyl-3- (p-dimethylaminophenyl) pyrazoline, 1,1
-Hydrazone compounds such as bis (4-diethylaminophenyl) -4,4-diphenyl-1,3-butadiene, indole compounds, oxazole compounds, isoxazole compounds, thiazole compounds, thiadiazole compounds, triazole compounds And other nitrogen-containing cyclic compounds, condensed polycyclic compounds, and the like. These charge transport materials are used alone or in combination of two or more. Note that the binder resin is not always necessary when using a charge transporting material having film-forming properties such as polyvinylcarbazole.

As the binder resin for the charge transport layer, various conventionally known resins can be used. For example, polystyrene, styrene-butadiene copolymer, styrene-
Acrylonitrile copolymer, styrene-maleic acid copolymer, acrylic resin, styrene-acrylic copolymer,
Ethylene-vinyl acetate copolymer, chlorinated polyethylene,
Thermoplastic resins such as polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polycarbonate, polyester, polyester alkyd resin, polyamide, polyurethane, polyarylate, polysulfone, diallyl phthalate resin, ketone resin, polyvinyl butyral resin, polyether resin, etc. , Silicone resin, epoxy resin, phenol resin, urea resin, melamine resin, and other crosslinkable thermosetting resins, and photocurable resins such as epoxy acrylate, urethane acrylate and polyester acrylate. These binder resins can be used alone or in combination of two or more.

The charge generation layer and the charge transport layer are terphenyl, halonaphthaloquinones, acenaphthylene,
It may contain various additives such as fluorenone compounds such as 9-carbazolyliminofluorenone, antioxidants, deterioration inhibitors such as ultraviolet absorbers, plasticizers and sensitizers. In the charge generation layer, the charge generation material and the diphenic acid aramid resin can be used in various ratios, but the charge generation material is 5 to 1000 parts by weight relative to 100 parts by weight of the diphenic acid aramid resin, Especially 30 to 5
It is preferably used in a proportion of 0 parts by weight.

The charge-transporting material and the binder resin constituting the charge-transporting layer can be used in various proportions within a range that does not hinder the transport of charges and a range that does not crystallize. In order to easily transport the electric charge generated in (3), it is preferable to use 10 to 500 parts by weight, and particularly 25 to 200 parts by weight of the charge transport material with respect to 100 parts by weight of the binder resin.

The thickness of the charge generation layer is preferably about 0.01 to 5 μm, more preferably about 0.1 to 3 μm, and the thickness of the charge transport layer is preferably 2 to 100 μm, especially about 5 to 50 μm. As the conductive substrate on which the photosensitive layer is formed, various materials having conductivity can be used, for example, aluminum, copper, tin, platinum, vanadium, molybdenum, chromium, cadmium, titanium, nickel, palladium, Metals such as indium, stainless steel and brass,
Examples include a plastic material obtained by vapor deposition or laminating of the above metal, glass coated with aluminum iodide, tin oxide, indium oxide, or the like.

The conductive substrate may be in the form of a sheet or a drum, and it is sufficient that the substrate itself has conductivity or the surface of the substrate has conductivity. In addition, it is preferable that the conductive substrate has sufficient mechanical strength when used. In each of the layers, the binder resin, charge generating material, charge transporting material and the like exemplified above are dispersed together with an appropriate solvent by a known method, for example, a roll mill, a ball mill, an attritor, a paint shaker or an ultrasonic disperser. The mixture may be mixed to prepare a coating solution, which may be coated and dried by a known means.

As the solvent, various organic solvents can be used. Examples thereof include alcohols such as methanol, ethanol, isopropanol and butanol, aliphatic hydrocarbons such as n-hexane, octane and cyclohexane, benzene, toluene and xylene. Aromatic hydrocarbons, dichloromethane, dichloroethane, carbon tetrachloride, halogenated hydrocarbons such as chlorobenzene, dimethyl ether, diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, ethers such as diethylene glycol dimethyl ether, ketones such as acetone, methyl ethyl ketone, cyclohexanone, acetic acid Examples thereof include esters such as ethyl and methyl acetate, dimethylformamide, dimethyl sulfoxide and the like.

As described above, since the diphenic acid aramid resin has a solubility selectivity, in the production method of the present invention, the polar solvent which dissolves the diphenic acid aramid resin is used for the charge generation layer in the above-mentioned various solvents. Used for coating liquid,
A non-polar solvent that does not dissolve is used in the coating liquid for the charge transport layer. The solvent may be used alone or in combination of two or more.

Further, in the coating liquid, a surfactant, a leveling agent or the like may be used in order to improve the dispersibility of the charge transport material or the charge generating material and the smoothness of the surface of the photosensitive layer.

[0036]

The present invention will be described in detail below with reference to examples and comparative examples. Example 1 40 parts by weight of metal-free phthalocyanine and 2000 parts by weight of tetrahydrofuran were dispersed in a paint shaker for 2 hours, and then 15 parts by weight of the diphenic acid aramid resin represented by the above formula (11) was added and dispersed for another 2 hours. Then, a coating liquid for the charge generation layer was prepared. The coating liquid thus obtained is coated on an aluminum cylinder and dried to a film thickness of 0.1-1.
A charge generation layer of μm was formed.

Onto this charge generation layer, a charge transport layer coating liquid consisting of 200 parts by weight of a charge transport material represented by the following formula (2), 200 parts by weight of a polycarbonate resin, and 925 parts by weight of toluene was dipped. It was applied by a stacking method and dried at 100 ° C. for 1 hour to form a charge transport layer having a film thickness of 5 to 50 μm to obtain a negative charging type laminated photoreceptor.

[0038]

[Chemical 6]

Example 2 Negative charging was performed in the same manner as in Example 1 except that 15 parts by weight of the diphenic acid aramid resin represented by the above formula (12) was used as the binder resin for the charge generation layer. A mold type laminated photoreceptor was obtained. Comparative Example 1 Polyvinyl butyral 1 as a binder resin for the charge generation layer
A negatively chargeable laminated photoreceptor was obtained in the same manner as in Example 1 except that 5 parts by weight was used.

The following tests were carried out on the electrophotographic photoreceptors of the above-mentioned respective Examples and Comparative Examples to evaluate their characteristics. Electrical Properties The electrophotographic photosensitive members prepared in the respective examples and comparative examples were set in a drum sensitivity tester, and the surface potential V ₀ (V) when the surface was charged to around ± 800 V was measured, and then 78
0 nm light intensity 0.016 mW / cm ² , exposure time 1
Exposure was carried out for 2 seconds to obtain a half-exposure amount E1 / 2 (μJ / cm ² ). Further, the surface potential at the time when 0.5 seconds passed immediately after the exposure was determined as the post-exposure potential V _r (V). Repeatability The above electrophotographic photosensitive member was set in a laser beam printer (model LP-2080 manufactured by Mita Kogyo Co., Ltd.) and 100
Surface potential V ₀ ′ after repeating image formation 0 times
(V), to measure the half decay exposure E1 / 2 '(μJ / cm 2) and the potential after exposure V _r' (V). Adhesiveness In accordance with the cross-cut test described in JIS K 5400 "General Test Method for Paints", 16 squares are provided in the photosensitive layer with a cutter knife to make four vertical and horizontal cuts, and a peeling test with cellophane tape is performed. After that, the adhesiveness of the photosensitive layer was evaluated by examining how many cells the coating film remained.

Table 1 shows the above test results.

[0042]

[Table 1]

From the results in Table 1 above, in both Examples 1 and 2, the surface potential was higher and the half-exposure amount was smaller than in Comparative Example 1 in which polyvinyl butyral was used as the binder resin for the charge generation layer. Moreover, since the residual potential was low, it was found that the sensitivity characteristics were excellent. In addition, in each of Examples 1 and 2, the electrical characteristics after repeated exposure did not change much from the initial values, which proved that the durability was excellent. Further, in all of Examples 1 and 2, it was found that after the peeling test using the cellophane tape, the coating films of all 16 cells remained, and the adhesiveness was excellent.

[0044]

According to the present invention, by using a diphenic acid-type aramid resin as the binder resin of the charge generation layer, it is possible to obtain an organic photoreceptor having unprecedentedly excellent electrophotographic characteristics.

Claims (2)

[Claims] 1. An electrophotographic photosensitive member comprising a conductive substrate and a charge generating layer containing a charge generating material and a charge transporting layer containing a charge transporting material laminated on the conductive substrate.
General formula (1) as a binder resin: (Wherein R ¹ , R ² , R ³ , R ⁴ and R ⁵ are the same or different and represent an alkyl group or an alkoxy group, and R ⁶ ,
R ⁷ , R ⁸ and R ⁹ are the same or different and each represents a hydrogen atom or an alkyl group. a, b, c and d are the same or different and are 0 to 4. An electrophotographic photoreceptor containing a diphenic acid-type aramid resin having a repeating unit represented by the formula (1). 2. A charge-generating material, a diphenic acid-type aramid resin having a repeating unit represented by the general formula (1), and a solvent which dissolves the diphenic acid-type aramid resin, on a conductive substrate. After the coating liquid is applied and dried to form the charge generation layer, the charge transport material and the binder resin and the binder resin are dissolved on the charge generation layer, but the diphenic acid aramid resin is not dissolved. A method for producing an electrophotographic photoreceptor, which comprises applying a coating solution containing a solvent and drying the coating solution to form a charge transport layer.