JP2000338691A - Production of electrophotographic photoreceptor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize the occurrence of a film sag part to the utmost simply by effectively manipulating coating application conditions in a process for producing an electrophotographic photoreceptor by a dip coating application method. SOLUTION: This process for producing the electrophotographic photoreceptor is a coating application method for producing a cylindrical substrate having a coating film on the outer peripheral surface of the substrate by mounting one end of the substrate at a supporting member to close the substrate, immersing the substrate into a coating liquid in the state of holding the other end open and pulling up the substrate, in which the coating application coefficient [S] of the cylindrical substrate is 0.5 to 0.9 when the radius of the outside diameter of the cylindrical substrate is defined as [r], the radius of the bore of a coating application tank as [R] and the coating application coefficient expressed by equation: S= (R2-r2)}/R2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an electrophotographic photosensitive member used in an apparatus such as a PPC copying machine, a laser beam printer, and a facsimile, and more particularly to a method for forming a coating film by a dip coating method. It is about the method.

[0002]

2. Description of the Related Art A method of immersing an object to be coated in a coating solution and then pulling the object vertically to the liquid surface for coating is known as a dip coating method. This dip coating method is also used as a typical method for manufacturing an electrophotographic photosensitive member. However, on the upper part of the coating film applied by the dip coating method, a portion where the film thickness is smaller than the stable film thickness (film sagging)
May occur. Since the characteristics of this portion do not satisfy the specifications as an electrophotographic photosensitive member, various methods for shortening the film sag have been studied.

For example, as a method of suppressing sagging by a coating apparatus, (1) JP-A-59-127049, JP-A-59-174844 and JP-A-2-4470 disclose the following methods.
A method of reducing the concentration of solvent vapor in the coating tank or near the surface of the coating liquid during the coating process has been adopted.However, when gas is supplied or exhausted, airflow unevenness tends to occur, and circumferential unevenness of the film thickness is reduced. Likely to happen. Also, (2) JP-A-59-
Japanese Patent Application Laid-Open Nos. 225771, 60-227261 and 5-111656 employ a method in which coating is performed while generating a uniform airflow in the circumferential direction, and there is a limit to the effect of reducing film sagging. Further, (3) JP-A-4-2191
In No. 69, a method is employed in which a negative pressure is generated around the coating liquid surface by applying an ascending airflow to the coating film on the surface of the object to be coated, and outside air is sucked around the liquid surface based on the negative pressure. ,
These remain problems in the complexity of the coating apparatus and in the compatibility with the simultaneous multi-dip coating method.

Another method for shortening the film sag is
The coating solution with an additive such as a thickener to the charge transport layer forming solution.
A method for suppressing coating sagging by forming a xotropy
JP-A-6-266126) is also known, but the addition amount is 1 to 1.
5 wt% (coating liquid ratio) is required, so the additive
High ratio, residual potential of electrostatic characteristics as photoreceptor
(V _R) And other side effects
Due to stickiness, it is difficult for bubbles to escape etc.
Not in. In addition, only the upper part is partially double (or multiple)
Coating method (JP-A-59-80364, JP-A-5-80364)
No. 66854) and increase the coating speed only at the upper end.
Method (Japanese Unexamined Patent Application Publication No. 10-26835).
In the case of a coating solution with solvent MDC, which has a small sag suppression effect
Even if the suppression effect may be small, the size of the sagging of the coating film
In the case of a thin THF, the effect is insufficient, and it is difficult to increase the film thickness.

In addition, a porous body having a specific surface area of not less than 3000 m ² / m ^2, such as a hollow cylinder or a cylinder having a hole in the center, is provided on the outer peripheral surface of the jig for holding an object to be coated, and an air supply portion is provided. A method of forming and uniformly supplying gas from the air supply section in the circumferential direction of the object to be coated (see JP-A-10-216616), the outer diameter d of the cylindrical base and the inner diameter of the cylindrical coating liquid tank or the prismatic coating liquid. The ratio D / d to the diameter D of a circle having an area equivalent to the area of the cross section of the tank is

[0006]

(Equation 1) Dip coating apparatus (JP-A-61-149268),
In the dip coating method of the overflow method, the difference D−d between the outer diameter d of the cylindrical substrate and the inner diameter D of the cylindrical coating tank is 3
Method of performing dip coating under the condition of 0 mm or more
No. 235562), when forming a function-separated type organic electrophotographic photoreceptor by a dip coating method in an overflow method, the inner diameter of the coating tank is 2R (mm), the diameter of the cylindrical conductive substrate is 2r (mm), Immersion speed V in coating liquid (mm / s)
Where πr ² / πR2 × V> 5 (where R> r + 1 (mm)), a method using a coating tank, a photoreceptor substrate, and a substrate immersion speed (JP-A-6-250412) Etc. are known.

[0007]

In any case, in the prior art, problems caused by dripping of the coating solution include the following. That is, since a coating film thinner than the target film thickness is formed at the upper end of the outer peripheral portion of the base, there are portions where the characteristics as the electrophotographic photosensitive member do not satisfy the standard. As a countermeasure, it is conceivable to lengthen the size of the cylindrical substrate and cut out only a portion having a uniform film thickness. However, it is disadvantageous in terms of high cost and miniaturization of copiers, laser beam printers and other devices. . Therefore, it is necessary to minimize the sagging of the coating start portion and minimize the portion outside the effective image area.

Here, the sagging and coating conditions are such that the sagging length decreases as the film thickness decreases, the sagging length decreases as the viscosity increases, and the sagging length increases as the coating coefficient increases. The relationship is that the film thickness becomes uniform as the film thickness increases, the film thickness becomes uniform as the viscosity decreases, and the coating coefficient decreases as the coating coefficient decreases. The film thickness becomes uniform. Thus, it can be seen that the sagging and the uniformity of the film thickness are opposite phenomena. It is an object of the present invention to make the sagging length shorter and to make the film thickness uniform by utilizing these features.

As a practical problem, in the actual production of an electrophotographic photosensitive member, the type of solvent, the solid content concentration of a coating solution, the length and diameter of a photosensitive substrate, the coating thickness, and the like may be changed. In the method (1), conditions must be determined for each manufacturing condition, and there is a disadvantage that a great deal of labor is required. The present invention has been made in view of the above-described circumstances, and its purpose is to obtain a target film thickness and sagging length with respect to a change in manufacturing conditions by an easy operation. It is another object of the present invention to provide a method for manufacturing an electrophotographic photoreceptor which can industrially produce an electrophotographic photoreceptor.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method and apparatus for manufacturing an electrophotographic photosensitive member by a dip coating method, in which the occurrence of a film dripping portion is reduced as much as possible simply by effectively controlling the coating conditions. To be

[0011]

Means for Solving the Problems The present invention provides the following (1) to
It has the configuration of (4). (1) With one end of the cylindrical base attached to the support member and closed, and the other end released, the base is immersed in a coating solution from the released end and pulled up to coat the outer peripheral surface of the base. In the coating method for producing a substrate having a film, when the coating coefficient represented by the relational expression (1) with the radius [r] of the outer diameter of the cylindrical substrate and the radius [R] of the inner diameter of the coating tank is [S], A method for producing an electrophotographic photosensitive member, wherein the coating coefficient [S] is 0.5 or more and 0.9 or less. S = {(R ² −r ² )} / R ² (1)

(2) Coating coefficient [S] is 0.5 or more and 0.9
The method for producing an electrophotographic photoreceptor according to the above (1), which provides a charge transport layer having a viscosity of 200 to 400 mPa · s below.

(3) The method for producing an electrophotographic photosensitive member according to the above (1), wherein the cylindrical substrate is formed by laminating at least two layers of a charge generation layer and a charge transport layer on a conductive substrate.

(4) The electrophotographic photosensitive member according to the above (1), wherein the cylindrical substrate is formed by laminating at least three layers of an undercoat layer, a charge generation layer and a charge transport layer on a conductive substrate. Production method.

By using the coating conditions represented by the above relational expression (1), it is possible to provide an electrophotographic photosensitive member having a charge transport layer having a short film sagging length and a uniform film thickness. That is, as the coating coefficient decreases, the film thickness becomes uniform,
As the sagging length decreases and the coating coefficient increases, the sagging length decreases, but the variation in film thickness increases. The conditions under which the contradictory relations settled down well were set by a relational expression. In addition, the higher the viscosity, the shorter the sagging length, but the greater the variation in film thickness, and the lower the viscosity, the more uniform the film thickness but the longer the sagging length. Therefore, in addition to the above relational expression, the viscosity was also specified.

The cylindrical substrate that can be used in the present invention has a volume resistivity of 1.0 × 10 ¹⁰ Ωcm or less, for example, aluminum, nickel, chromium, or the like.
Copper, tin oxide, indium oxide, etc. deposited on a sheet-like or seamless belt-like plastic film to form an endless belt, a seamless belt made of nickel, iron, beryllium-copper alloy, etc., aluminum, nickel-cobalt alloy, stainless steel, etc. To D. I, I.I. I,
Pipes that have been surface-treated by cutting, superfinishing, polishing, or the like after being formed into a tube by a method such as extrusion or drawing can be used.

In the electrophotographic photosensitive member of the present invention, an undercoat layer can be provided between the cylindrical conductive substrate and the photosensitive layer. The undercoat layer serves as an adhesive layer for preventing charge injection from the conductive substrate into the photosensitive layer in the photosensitive layer having a laminated structure during charging, and for integrally bonding and holding the photosensitive layer to the conductive substrate. Or the effect of preventing light reflected from the conductive support. The undercoat layer is generally made of a resin as a main component, but considering that the photosensitive layer is coated thereon with a solvent, these resins should be resins having high solubility resistance to general organic solvents. Is desirable. Such resins include polyvinyl alcohol, casein, water-soluble resins such as sodium polyacrylate, copolymerized nylon, alcohol-soluble resins such as methoxymethylated nylon, polyurethane, melamine resin, alkyd-melamine resin, epoxy resin, and the like. Curable resins that form a three-dimensional network structure are exemplified.

In order to prevent moiré and reduce residual potential, fine powder of a metal oxide, such as titanium oxide, silica, alumina, zirconium oxide, tin oxide or indium oxide, may be added to the undercoat layer. Good. These undercoat layers can be formed using an appropriate solvent and a coating method as in the above-described photosensitive layer.

Further, as the undercoat layer of the present invention, a metal oxide layer formed by a sol-gel method using a silane coupling agent, a titanium coupling agent, a chromium coupling agent or the like is also useful.

In addition to the above, the undercoat layer of the present invention contains Al ₂ O ₃
Provided by anodic oxidation, organic substances such as polyparaxylylene (parylene), SiO, SnO ₂ , TiO ₂ , IT
Those provided with an inorganic substance such as O and CeO ₂ by a vacuum thin film manufacturing method can also be used favorably. The thickness of the undercoat layer is suitably from 3 to 7 μm.

The charge generation layer is a layer containing a charge generation material as a main component. Inorganic and organic materials are used for the charge generating material. Representative examples thereof include monoazo pigments, disazo pigments, trisazo pigments, perylene pigments, perinone pigments, quinacridone pigments, quinone condensed polycyclic compounds, and squaric acid dyes. Phthalocyanine pigments, naphthalocyanine pigments, azulhenium salt dyes, selenium, selenium-tellurium, selenium-arsenic alloys, amorphous silicon, and the like.

The charge generating materials may be used alone or in combination of two or more. The charge generation layer, together with a binder resin appropriately using a charge generation material, tetrahydrofuran, cyclohexanone, dioxane, 2-butanone,
It can be formed by dispersing in a ball mill, an attritor, a sand mill or the like using an appropriate solvent such as dichloroethane and applying a dispersion. At this time, it is effective that the charge generating substance has a particle size of 5 μm or less, preferably 2 μm or less, and optimally 0.5 μm or less in volume average particle diameter. The coating can be performed by a dip coating method, a spray coating method, a bead coating method, or the like.

As the binder resin used as appropriate,
Polyamide, polyurethane, polyester, epoxy resin, polyketone, polycarbonate, silicone resin,
Acrylic resin, polyvinyl butyral, polyvinyl formal, polyvinyl ketone, polystyrene, polyacrylamide and the like are used. The amount of the binder resin appropriately used is 0 to 1 part by weight of the charge generation material.
~ 2 parts by weight is suitable.

The thickness of the charge generation layer used in the present invention is generally from 0.1 to 5 μm, preferably from 0.2 to 2 μm.

The charge transport layer in the electrophotographic photoreceptor of the present invention is formed by including a charge transport substance in a suitable binder. As the charge transport material, 2,5-bis (p
Oxadiazole derivatives such as -diethylaminophenyl) -1,3,4-oxadiazole, 1,3,5-triphenyl-pyrazoline, 1- [pyridyl- (2)]-
Pyrazoline derivatives such as 3- (p-diethylaminostyryl) -5- (p-diethylaminophenyl) pyrazoline; aromatic tertiary amino compounds such as triphenylamine, styryltriphenylamine and dibenzylaniline; Aromatic tertiary diamino compounds such as diphenyl-N, N'-bis (3-methylphenyl) -1,1-biphenyl-4,4'-diamine; 3- (4'-dimethylaminophenyl) -5; 1,2, such as 6-di- (4'-methoxyphenyl) -1,2,4-triazine
4-triazine derivatives, hydrazone derivatives such as 4-diethylaminobenzaldehyde-1,1-diphenylhydrazone, quinazoline derivatives such as 2-phenyl-4-styryl-quinazoline, 6-hydroxy-2,3-di (p-methoxyphenyl) -Benzofuran derivatives such as benzofuran, p- (2,2-diphenylvinyl)-
Α-stilbene derivatives such as N, N-diphenylaniline, “Journal of Imaging Sci”
ence "29: 7-10 (1985), carbazole derivatives such as N-ethylcarbazole, poly-N-vinylcarbazole such as poly-N-vinylcarbazole and derivatives thereof, poly-
γ-carbazolylethyl glutanate and derivatives thereof,
Further, known charge transporting substances such as pyrene, polyvinylpyrene, polyvinylanthracene, polyvinylacridine, poly-9-biphenylanthracene, pyrene-formaldehyde resin, and ethylcarbazole formaldehyde resin can be used, but are not limited thereto. Absent. These charge transport materials can be used alone or in combination of two or more.

Further, as the binder resin in the charge transport layer, polycarbonate resin, polyester resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinylidene chloride resin, polystyrene resin, polyvinyl acetate resin, butylene-butadiene copolymer , Vinylidene chloride-acrylonitrile copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, silicone resin, silicone-alkyd resin, phenol-formaldehyde resin, styrene-alkyd resin, poly A known resin such as -N vinylcarbazole can be used, but is not limited thereto. These binder resins can be used alone or in combination of two or more.

In the present invention, a plasticizer or a leveling agent may be added to the charge transport layer. As the plasticizer, those used as general plasticizers for general resins such as dibutyl phthalate and dioctyl phthalate can be used as they are, and the amount of the plasticizer is suitably about 0 to 30% by weight based on the binder resin. As the leveling agent, silicone oils such as dimethyl silicone oil and methyl phenyl silicone oil, and polymers or oligomers having a perfluoroalkyl group in a side chain are used. % Is appropriate.

Further, if necessary, a protective layer may be provided on the charge transport layer. This protective layer is used to prevent the charge transport layer from being chemically altered during charging of the photosensitive layer having a laminated structure, and to improve the mechanical strength of the photosensitive layer.
Further, the above-described charge transporting material may be added to the protective layer. Further, as the binder resin used for this protective layer, polyamide resin, polyurethane resin, polyester resin,
Known resins such as epoxy resin, polyketone resin, polycarbonate, polyvinyl ketone resin, polystyrene, and polyacrylamide resin can be used. Also,
The protective layer must be configured so as not to substantially impede the passage of light used for image exposure.

Materials used for this include ABS resin, ACS resin, olefin-vinyl monomer copolymer, chlorinated polyether, allyl resin, phenol resin, polyacetal, polyamide, polyamideimide,
Polyacrylate, polyallyl sulfone, polybutylene, polybutylene terephthalate, polycarbonate,
Polyether sulfone, polyethylene, polyethylene terephthalate, polyimide, acrylic resin, polymethylpentene, polypropylene, polyphenylene oxide,
Examples include resins such as polysulfone, AS resin, AB resin, BS resin, polyurethane, polyvinyl chloride, polyvinylidene chloride, and epoxy resin.

For the purpose of improving the abrasion resistance, a fluorine resin such as polytetrafluoroethylene, a silicone resin and an inorganic material such as titanium oxide, tin oxide and potassium titanate are dispersed in these resins. And the like can be added. As a method of forming the protective layer,
A normal coating method is employed. The thickness of the protective layer used in the present invention is 0.5 to 20 μm, preferably 1 to 10 μm.
Is appropriate. In addition to the above, known materials such as iC and a-SiC formed by a vacuum thin film manufacturing method can be used as the protective layer.

In the present invention, another intermediate layer may be provided between the photosensitive layer and the protective layer. In the middle layer,
Generally, a binder resin is used as a main component. These resins include polyamide, alcohol-soluble nylon,
Water-soluble polyvinyl butyral, polyvinyl butyral,
Polyvinyl alcohol and the like. As a method for forming the intermediate layer, a normal coating method is employed as described above.
The thickness of the intermediate layer is suitably about 0.05 to 2 μm.

FIG. 1 is a schematic sectional view of a dip coating apparatus suitable for the present invention. A predetermined coating liquid 9 is stored in the coating tank 6, and the tray 3 is provided around a side wall 16 of the coating tank 6. The coating liquid 9 is sent out of the preliminary tank 8 by a liquid sending pump 10, supplied through a filter 11 from a supply port 12 into the coating tank 6 as shown by an arrow B, and further over the upper edge of the side wall 16. The coating liquid 13 overflowing in the circumferential direction of the coating tank 6 is collected in the receiving tray 3, is returned as return liquid 14 from the return pipe 7, and is discharged to the preliminary tank 8. After the liquid supply pump 10 is stopped and the coating tank lid 2 is fully opened, the cylindrical substrate 1 starts immersion from the opening 4, passes through the vapor layer 5, enters the coating liquid surface 15, and immerses in the direction indicated by the arrow A. I do.

[0033]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples. Example 1 The following materials were dissolved to prepare a charge transport layer coating solution. 7 parts by weight of the charge transporting agent represented by the following structural formula 1 10 parts by weight of polycarbonate 83 parts by weight of dichloromethane

[0034]

Embedded image

This coating solution was applied by dip coating to a cylindrical cylindrical mirror substrate made of aluminum having an inner diameter of 150 mm and an outer diameter of 100 mm and dried at 110 ° C. for 20 minutes to form a charge transport layer.

The thickness of the charge transport layer is measured using a light interference type thickness meter, and the change in a minute section from the start of coating is zero.
Alternatively, the coating length until the coating length becomes constant is defined as the sagging length, and those having a ratio of the sagging length of less than 10% to the entire coating length are regarded as good products. The uniformity of the coating film was evaluated on a three-point scale.
Evaluation was made as Δ when the thickness was 5 μm or more and less than 1.0 μm, and as X when the thickness was 1.0 μm or more.

The experiments of Examples 2 and 3 and Comparative Examples 1 and 2 were carried out using the same coating liquid as in Example 1 and changing the inner diameter of the coating tank and the outer diameter of the substrate as shown in Table 1 below. However, when the condition represented by the relational expression (1) defined in the present invention is satisfied, the sag length is less than 10%, and when the condition is not satisfied, the sag length is 10% or more. ,
When the film thickness was in the range of 1.0 μm or more, it was impossible to obtain a uniform film having good quality and variation.

[0038]

[Table 1]

Example 4 A charge transport layer was formed in the same manner as in Example 1. At this time, the outer diameter of the cylindrical mirror substrate was 80 mm, and the inner diameter of the coating tank was 15 mm.
Dip coating was performed at 0 mm. Hereinafter, the experiments of Examples 4 to 9 were carried out by changing the viscosity as shown in Table 2 below in addition to the inner diameter of the coating tank and the outer diameter of the base using the same coating liquid as in Example 1, and as a result, When claim 1 of the invention is satisfied,
Good quality is obtained. When satisfying claim 2 in addition to claim 1, a higher quality and uniform coating film having a sag length of less than 10% and a variation in film thickness of less than 0.5 μm can be obtained.

[0040]

[Table 2]

Example 10 The following materials were dissolved to prepare an undercoat layer coating solution. 5 parts by weight of soluble nylon (Alamine CM-800
0, manufactured by Toray Co., Ltd.) Methanol 95 parts by weight This coating solution was coated with a coating tank having an inner diameter of 150 mm and an outer diameter of 100 m.
m on a cylindrical substrate made of aluminum,
After drying at 10 ° C. for 10 minutes, an undercoat layer having a thickness of 3 μm was formed.

Next, a charge generation layer coating solution having the following composition was prepared. The charge generating agent represented by the following structural formula 1 10 parts by weight Polyvinyl butyral 7 parts by weight Tetrahydrofuran 145 parts by weight

[0043]

Embedded image

This coating solution was placed in a ball mill and milled for 72 hours. Further, 200 parts by weight of cyclohexanone was added and dispersed for 1 hour. The liquid after the dispersion was further diluted and prepared with cyclohexanone to prepare a charge generating layer coating liquid. This coating solution was dip-coated on the aluminum cylindrical substrate on which the undercoat layer was formed, and dried at 100 ° C. for 10 minutes to form a 0.1 μm-thick charge generation layer.

Next, a charge transport layer was formed in the same manner as in Example 1. Hereinafter, coating under the conditions shown in Table 3 below,
The image evaluation was performed on a real machine in a three-step evaluation.

[0046]

[Table 3]

[0047]

By using the coating conditions specified in the present invention, it is possible to provide an electrophotographic photosensitive member having a charge transport layer having a short film sagging length and a uniform film thickness.

[Brief description of the drawings]

FIG. 1 is an explanatory view of an apparatus suitable for carrying out a manufacturing method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylindrical substrate 2 Coating tank lid 3 Receiving tray 4 Opening 5 Solvent vapor layer 6 Coating tank 7 Return piping 8 Preliminary tank 9 Coating liquid 10 Liquid sending pump 11 Filter 12 Supply port 13 Overflowing coating liquid 14 Return liquid 15 Coating liquid level 16 Side wall

Claims (4)

[Claims] 1. An outer peripheral surface of a cylindrical substrate, wherein one end of the cylindrical substrate is attached to a support member and closed, and the other end is released. The substrate is immersed in a coating solution from the released end and pulled up. In the coating method for producing a substrate having a coating film, the coating coefficient represented by the relational expression (1) with the radius [r] of the outer diameter of the cylindrical substrate and the radius [R] of the inner diameter of the coating tank was defined as [S]. In this case, the coating coefficient [S] is 0.5 or more and 0.9 or less. S = {(R ² −r ² )} / R ² (1) 2. The method for producing an electrophotographic photoreceptor according to claim 1, wherein a charge transport layer having an application coefficient [S] of 0.5 to 0.9 and a viscosity of 200 to 400 mPa · s is provided. 3. The method according to claim 1, wherein the cylindrical substrate is formed by laminating at least two layers of a charge generation layer and a charge transport layer on a conductive substrate. 4. The method for producing an electrophotographic photosensitive member according to claim 1, wherein the cylindrical substrate is formed by laminating at least three layers of an undercoat layer, a charge generation layer and a charge transport layer on a conductive substrate. .