JPH0518420B2 - - Google Patents

Description

[Detailed description of the invention]

FIELD OF THE INVENTION The present invention relates to a method for manufacturing an electrophotographic photoreceptor by dip coating, and particularly to a method for efficiently coating a charge generation layer of a functionally separated electrophotographic photoreceptor. BACKGROUND ART Conventionally, functionally separated electrophotographic photoreceptors have been put into practical use, in which a photosensitive layer is divided into a charge generation layer and a charge transport layer to improve sensitivity, charging characteristics, and the like. These layers are manufactured by dispersing or dissolving the charge-generating pigment or the charge-transporting material in a resin with good film-forming properties, and then coating the mixture. When selecting a binder resin for the charge generation layer, consider the dispersibility for the charge generation substance, the stability of the dispersion, the adhesion to the conductive layer or subbing layer, and the resistance to organic solvents contained in the charge transport layer. It is necessary to consider the properties of the paint, such as solubility and penetration resistance, and the electrophotographic properties of the electrophotographic photoreceptor, such as sensitivity, potential retention, or photohistory properties, depend on the type of binder resin used. Furthermore, since durability characteristics such as storage stability, durability against environmental changes, and durability upon repeated use vary, it is necessary to fully consider these points. Examples of resin materials include polyester, polystyrene, fatty acid cellulose ester resin, poly(meth)acrylic acid esters, polyvinylpyrrolidone, polyvinyl butyral, etc.
Among these, polyvinyl butyral resin (hereinafter referred to as "PVB") effectively satisfies the above characteristics, as described in JP-A-59-64848. Furthermore, as a coating method, dip coating is the best since it provides a seamless and smooth surface on the cylindrical substrate. When applying a charge generation layer dispersed in a PVB solution by dip coating, JP-A-59-64848 states that the concentration of nonvolatile matter should be adjusted to 0.3 to 3% and the coating speed should be 40 cm/min or less. It is stated that. This method reduces the charge generation layer to 0.03
This is the optimal method for obtaining good surface properties and film thickness when coating to a film thickness of ~0.5 μm. Problems to be Solved by the Invention The thickness of the charge generation layer contributes to electrophotographic properties such as acceptance potential, sensitivity, photomemory effect, durability, and environmental characteristics, but depending on the type of pigment, In some cases, it may be desired to make the film thicker, 0.5 to 5 μm. For example, charge-generating pigments include monoazo/disazo/trisazo/or higher polyazo pigments;
Polycyclic quinone pigments, perylene pigments, indigo pigments,
Bisbenzimidazole pigments, phthalocyanine pigments, quinacridone pigments, etc. are known, and when forming a charge generation layer using an azo pigment among these, a film thickness of 0.03 to 0.5 μm is suitable. In the case of other pigments, the optimum film thickness may have to be large. For example, Tokukai Akira
Polycyclic quinones such as anthanthrone, pyranthrone, dibenzpyrenequinone, pyrenequinone, and dibromanthanthrone described in JP-A No. 47-18544, perylene pigments described in JP-A-47-30330; Indigo pigment described in JP-A-47-30331, JP-A-47-
The bisbenzimidazole pigment described in JP-A No. 18543 and the quinacridone pigment described in JP-A-47-30332 are each formed to a thickness of 0.8 μm by vacuum evaporation. If it is applied in the form of a coating liquid, it needs to be even thicker than that. However, it has not been possible to form a thick charge generation layer using conventional, well-known coating methods. Therefore, an object of the present invention is to reduce the film thickness by 0.5 when forming a charge generation layer by dip coating using a coating liquid obtained by dispersing a charge generation pigment in a PVB solution.
The objective is to provide a coating method that allows coating up to 5 μm. Means for Solving the Problems The present invention provides a method for manufacturing an electrophotographic photoreceptor, which comprises forming at least a charge generation layer and a charge transport layer on a substrate. When forming a charge generation layer on a substrate by dip coating using a liquid, the charge generation pigment is selected from polycyclic quinone pigments, perylene pigments, indigo pigments, bisbenzimidazole pigments, phthalocyanine pigments, and quinacridone pigments. Using pigment, the non-volatile content concentration of the coating liquid is 5.
Adjust the pulling speed of the base to ~20% and increase it to 5~40%.
0.5~ by dip coating at cm/min.
It is characterized by obtaining a charge generation layer with a film thickness of 5 μm. The PVB used in the present invention typically has the following structural formula. (In the formula, the respective ratios of l, m and n are m, that is, acetyl group is 5 mol% or less, l, that is, butyral group is 60 to 81 mol%, and n, that is, hydroxyl group is the remainder. ) In the present invention, in order to form a charge generating layer with a thickness of 0.5 to 5 μm by dispersing a charge generating pigment in a PVB solution and applying it by dip coating, the nonvolatile content concentration of the coating liquid must first be adjusted to 5 to 20%. If the non-volatile content is less than 5%, the substrate pulling speed should be increased to 40%.
It is necessary to use a high speed exceeding cm/min, and at such a high speed, the sagging and unevenness of the coating film becomes severe and good results cannot be obtained. Furthermore, if it exceeds 20%, it is difficult to obtain the optimum film thickness no matter how slow the pulling speed is. Further, in the present invention, the pulling speed of the substrate, which is the object to be coated, needs to be 5 to 40 cm/min. If the pulling speed is less than 5 cm/min, the manufacturing efficiency will deteriorate, which is not preferable. 40 again
If it exceeds cm/min, the above-mentioned unfavorable results will be obtained and it is inappropriate. Therefore, in the present invention, the nonvolatile content concentration of the coating liquid is 5 to 20%, and the pulling speed of the substrate is set to 5%.
~40 cm/min is an essential requirement for forming a charge generation layer with a thickness of 0.5 to 5 μm. The formation of the charge generation layer will be described in more detail. The coating liquid can be obtained by dispersing the pigment in a PVB coating liquid, but it may also be prepared by dispersing the pigment only in a solvent and then adding the PVB coating liquid to the dispersion. The blending ratio of pigment and resin in the coating liquid is set to about 40:1 to 1:4, preferably about 20:1 to 1:2.
Since PVB maintains the dispersion stability of the pigment well, aggregation of the pigment is unlikely to occur even without adding a large amount of resin, and from this point of view as well, the use of PVB in the present invention is advantageous. As a method for dispersing the charge-generating pigment in the PVB solution, a conventional method using a ball mill, roll mill, attritor, sand mill, agitator mill, etc. can be applied. For dispersion, it is also effective to use surfactants and various dispersion aids in combination. After the dispersion is completed, a suitable amount of solvent is added to the dispersion liquid to adjust the nonvolatile content concentration to 5 to 20% to obtain a coating liquid. Solvents used for dispersion include alcohols such as propanol and butanol, ketones such as methyl ethyl ketone, methyl butyl ketone, and cyclohexanone, esters such as ethyl acetate and butyl acetate, ethers such as tetrahydrofuran and dioxane,
Suitable are cellosolves such as methoxyethanol and ethoxyethanol, and cellosolve acetates such as methoxyethyl acetate and ethoxyethyl acetate. These solvents may be used alone or in combination. Next, a dip coating apparatus used for coating with the above coating liquid will be explained with reference to FIG. The coating liquid 1 is filled in the coating tank 2 and is further supplied from the supply port 7 at the bottom of the coating tank by the pump 10, and the overflow liquid 4 returns to the tank 11 from the discharge port 6 and is circulated. The cylindrical substrate 3 is raised and lowered by an appropriate method and immersed in the coating tank. A wall surface 5, a lid 8, and a paint receiver 9 are provided at the top of the coating tank. In the present invention, in the charge generation layer coating step,
After the substrate is immersed in the coating solution, the speed at which it is pulled up is controlled at 5 to 40 cm/min. The amount of overflow liquid will differ depending on when the substrate is immersed and when it is pulled up, but this is not a problem. Also, in the middle of the circulatory system,
A filter 12 may also be provided. Next, a charge transport layer is formed on the formed charge generation layer. That is, a charge transporting substance such as an aromatic tertiary amino compound, a hydrazone compound, a pyrazoline compound, an oxazole compound, an oxadiazole compound, a stilbene derivative, a carbazole compound, etc., is used as a material such as polycarbonate, polyarylate, polyester, polystyrene, styrene-acrylonitrile copolymer, or polysulfone. , polymethacrylic acid esters, styrene-methacrylic acid ester copolymers, etc. in an appropriate solvent, and the resulting coating liquid is applied onto the charge generation layer. The thickness of the charge transport layer is preferably about 5 to 50 μm. Further, in the present invention, a barrier layer may be formed between the charge generation layer and the substrate. The barrier layer is effective in preventing unnecessary charge injection from the substrate, and can improve charging characteristics and image quality. Furthermore, adhesion to the substrate can also be improved. Constituent materials for the barrier layer include polyvinyl alcohol, polyvinylpyrrolidone, polyvinylpyridine, cellulose ethers, cellulose esters, polyamide, polyurethane, casein, gelatin, polyglutamic acid, starch, starch acetate, amine starch, polyacrylate, and polyester. Examples include acrylamide. The resistivity of these materials is preferably about 10 ⁵ to 10 ¹⁴ Ω·cm. The thickness of the barrier layer is 0.05~
Approximately 2 μm is suitable. Examples Hereinafter, the present invention will be explained using examples. 1 part (by weight, same hereinafter) of PVB (trade name: BM1, manufactured by Sekisui Chemical Co., Ltd.) was dissolved in 19 parts of cyclohexanone. 8 parts of dibromanthanthrone pigment (CIPigment Red 168) were mixed with 20 parts of this solution, and then dispersed using a sand mill. The average particle size after dispersion was 0.4 μm. Cyclohexanone was further added to the dispersion liquid to prepare coating liquids with various nonvolatile content concentrations. On the other hand, an 84φ×338mm aluminum pipe was used as the base. The above coating liquid was dip coated onto the aluminum pipe using the dip coater shown in FIG. 1 to form a charge generation layer. non-volatile concentration,
Table 1 shows the state of the coating liquid, the pulling speed, and the film thickness.

[Table] Next, a charge transport layer was formed on the formed charge generation layer. That is, N,N'-diphenyl-N,
5 parts of N'-bis(3-methylphenyl)-[1,1'-biphenyl]-4,4'-diamine was used as a charge transport material and dissolved in 40 parts of monochlorobenzene along with 6 parts of polycarbonate Z resin. The solution was applied by a dip coater at a pull rate of 11 cm/min. It was dried at 110° C. for 1 hour to form a charge transport layer with a thickness of 20 μm, thereby obtaining an electrophotographic photoreceptor. For each electrophotographic photoreceptor obtained, −
Apply corona charging to 800V, then
Potential of the part irradiated with white light of 8ergs/ ^cm2 (VBK
shall be. ) and the potential of the part not irradiated with light (denoted as VD) were measured. In addition, we put the electrophotographic photoreceptor into an electronic copying machine and examined copied images.
The results are shown in Table 2.

【table】

[Table] From the above results, the nonvolatile content concentration is 5 to 40 cm/min,
It is also found that when coating is carried out at a pulling rate of 5 to 40 cm/min, a charge generation layer having a thickness of 0.5 to 5 μm can be obtained in good condition. Comparative Example Using the same pigment (dibromanthanthrone) as in Example, dispersion treatment was carried out in the same manner except that only the resin was replaced with the one shown below. However, in all of the obtained dispersions, aggregates of aggregates were present, and a fluid liquid could not be obtained, so that they could not be used for dip coating. ○ Cellulose acetate butyrate resin (Product name: CAB381 manufactured by Eastman Chemical) ○ Polyester resin (Product name: Vylon 200 manufactured by Toyobo Co., Ltd.) ○ Polystyrene resin (Product name: HH102 manufactured by Mitsubishi Monsanto Co., Ltd.) ○ Acrylic resin (Product name: Name: BR80 (manufactured by Mitsubishi Rayon Co., Ltd.) Effects of the Invention By applying the manufacturing method of the present invention, a charge generation layer with a thickness of 0.5 to 5 μm can be efficiently and stably formed, and the electrophotographic photoreceptor This can lead to improved productivity. The electrophotographic photoreceptor obtained by the present invention can be effectively used in electrophotographic copying machines, but it can also be applied to various printers, microfilm readers, electrophotographic engraving systems, etc. that apply xerography technology. be.

[Brief explanation of the drawing]

The drawing is a schematic sectional view of an example of an apparatus used in the manufacturing method of the present invention. 1... Coating liquid, 2... Coating tank, 3... Substrate, 4...
... Overflow liquid, 5 ... Wall surface, 6 ... Discharge port, 7 ... Supply port, 8 ... Lid, 9 ... Receiver,
10...pump, 11...tank, 12...filter.

Claims (1)

[Claims] 1. In a method for manufacturing an electrophotographic photoreceptor, which comprises forming at least a charge generation layer and a charge transport layer on a substrate, a coating liquid comprising a charge generation pigment dispersed in a polyvinyl butyral resin solution is used, and the method is applied by dip coating. When forming the charge generation layer on the substrate, a pigment selected from polycyclic quinone pigments, perylene pigments, indigo pigments, bisbenzimidazole pigments, phthalocyanine pigments, and quinacridone pigments is used as the charge generation pigment, and the nonvolatile content of the coating liquid is An electrophotographic photoreceptor characterized in that a charge generation layer with a thickness of 0.5 to 5 μm is obtained by dip coating with a concentration of 5 to 20% and a substrate pulling speed of 5 to 40 cm/min. manufacturing method.