JPH09197690A - Dip-coating method and device used for it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form an excellent coating film by keeping a solid portion density of a coating liquid for forming a photosensitive layer having high viscosity, which is applied to a base body of an electrophotographic sensitive body, at a constant value. SOLUTION: In dip-coating method, a coating liquid for forming a photosensitive layer having high viscosity is applied to a base body of an electrophotographic sensitive body. The coating liquid, which flows out of a coating liquid tank 1, is added to and mixed with a solvent 5 through a static mixer 4 and then is circulated (returned) to the coating liquid tank 1. Thus, the solid portion density of the coating liquid in the coating liquid tank 1 is adjusted before the liquid is applied to.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an electrophotographic photosensitive member. More specifically, it relates to a method of applying a coating solution for forming a photosensitive layer onto an electrophotographic photoreceptor substrate by a dip coating method. More specifically, it relates to a method of applying a photosensitive layer-forming coating liquid containing a charge transporting substance, a binder resin and a solvent onto an electrophotographic photosensitive substrate by a dip coating method.

[0002]

2. Description of the Related Art An electrophotographic photoreceptor is generally a coating solution for forming a photosensitive layer on a cylindrical substrate made of a metal such as aluminum, stainless steel or brass or a polymeric material such as polyethylene terephthalate, nylon or phenol resin. It is manufactured by applying. Although there are various coating methods, a dip coating method in which a cylindrical substrate is dipped in a photosensitive layer-forming coating solution for coating is widely used. The photoreceptor has
Laminate type photoreceptor prepared by separately applying a charge generating layer forming coating solution and charge transporting layer forming coating solution, and a single layer prepared by applying a coating solution containing a charge generating substance and a charge transporting substance There is a type photoconductor, but in both of them, what is important in manufacturing is that the coating layer has a uniform thickness without unevenness and has a set film thickness.

[0003]

The coating solution for forming a charge generating layer comprises a charge generating substance such as an azo pigment or a quinone pigment, a binder resin and a solvent, and the coating solution for forming a charge transport layer comprises a charge such as a hydrazone compound. The coating liquid consisting of a transport material, a binder resin and a solvent, which is used for manufacturing a single-layer type photoreceptor, comprises a charge generating material, a charge transport material, a binder resin and a solvent. The liquid and the coating liquid used for producing the single-layer type photoreceptor have particularly high viscosity, and when the solvent evaporates from the upper surface of the coating liquid during the coating operation, the solid content concentration in the coating liquid increases,
The viscosity increases, and as a result, the coating film thickness becomes thick, and it is notable that a predetermined film thickness cannot be obtained. Therefore, it is necessary to replenish the coating solution with a solvent to adjust the concentration of the coating solution. In this case, the coating liquid is approximately 150 to 350 cp.
The viscosity of the solvent is 0.5-5 cps.
It is not easy to mix both because it is low, and it takes a lot of time. The present invention has been made in view of the above circumstances, and an object thereof is a coating solution for forming a photosensitive layer on an electrophotographic photoreceptor substrate, particularly a coating solution for forming a charge transport layer and a coating solution used for producing a single-layer type photoreceptor. Another object of the present invention is to provide a method of applying a coating film having a set film thickness without unevenness in thickness by the dip coating method.

[0004]

That is, according to the present invention, a coating solution for forming a photosensitive layer, in particular, a coating solution for forming a photosensitive layer containing a charge transport substance, a binder resin and a solvent is immersed in an electrophotographic photoreceptor substrate. In the method of applying by a coating method, the coating solution flowing out of the coating tank is added with a solvent through a static mixer to add a solvent, and the solid content concentration of the coating solution in the coating tank is circulated in the coating tank by mixing and circulating. The gist is a dip coating method characterized by adjusting.

Further, in the above method, the gist is a dip coating method in which the coating solution flowing out is guided to a circulation tank for storage, and the coating solution in the circulation tank is supplied to a static mixer using a pump. is there. Further, the present invention is an apparatus used for carrying out the dip coating method, wherein the electrophotographic photoreceptor substrate is dipped and a coating tank for coating a photosensitive layer forming coating solution, the coating solution flowing out from the coating tank. A circulating tank for storing the liquid, a pump for feeding the coating liquid in the circulating tank to a static mixer, a solvent tank, a pump for feeding the solvent in the solvent tank to the static mixer, and a static mixer for mixing the coating liquid and an additional solvent. The gist of the invention is an apparatus for dip-coating a coating solution for forming a photosensitive layer containing a charge transporting substance, a binder resin and a solvent onto an electrophotographic photoreceptor substrate.

Hereinafter, the present invention will be described in detail. In the present invention, the electrophotographic photoreceptor substrate is, for example, a metal material such as aluminum, brass, stainless steel, a polymer material such as polyethylene terephthalate, polybutylene terephthalate, polypropylene, nylon, polystyrene, phenol resin, or hard paper. 20 other ingredients
These are various conventionally known substrates formed into a cylindrical shape having an outer diameter of about 200 mm to a length of about 300 to 1000 mm.
In the case of an insulating material, it is subjected to conductive treatment by a method such as impregnation with a conductive material, lamination of metal foil, vapor deposition of metal or the like.

The coating liquid for forming a photosensitive layer is any one of various conventionally known coating liquids containing a photosensitive material and one or more kinds of solvents. The coating liquid for forming a photosensitive layer in the case of producing a single-layer type electrophotographic photosensitive member. Is prepared by mixing a charge generating substance, a charge transporting substance, a binder resin and a solvent. Further, the coating solution for forming a photosensitive layer in the case of producing a laminated electrophotographic photoreceptor comprises a coating solution for forming a charge generating layer, which comprises a charge generating substance, a binder resin and a solvent, and a charge transporting substance, a binder resin and a solvent. The coating liquid for forming the charge transport layer is prepared separately. The present invention is applicable to the coating operation of the coating liquid for forming a photosensitive layer in the case of producing a single-layer type electrophotographic photoreceptor and the coating liquid for forming a charge transport layer in the case of producing a laminated type electrophotographic photoreceptor. And

Examples of the charge generating substance include azo pigments such as Sudan Red, Diane Blue and Dienas Green B, disazo pigments, argone yellow, quinone pigments such as pyrenequinone, quinocyanine pigments and perylene pigments.
Examples thereof include bisbenzimidazole pigments such as indigo pigments and Indian first orange toner, phthalocyanine pigments such as copper phthalocyanine, quinacridone pigments, pyrylium salts and azurenium salts.

Examples of the charge-transporting substance include a polyaromatic compound such as anthracene, pyrene, phenanthrene and coronene in the main chain or side chain, or indole, carbazole, oxazole, isoxazole, thiazole, imidazole, pyrazole, oxadiazole, pyrazoline, Examples thereof include compounds having a skeleton of nitrogen-containing cyclic compounds such as thiadiazole and triazole, and hole transporting substances such as hydrazone compounds.

As the binder resin, polycarbonate, polyarylate, polystyrene, polymethacrylic acid esters, styrene-methyl methacrylate copolymer, polyester, styrene-acrylonitrile copolymer, polysulfone, polyvinyl acetate, polyacrylonitrile, polyvinyl butyral, polyvinyl pyrrolidone, Methyl cellulose, hydroxymethyl cellulose,
Examples thereof include cellulose esters.

As the solvent, a solvent having a high volatility and a vapor density higher than that of air is preferably used. For example, n-butylamine, diethylamine, ethylenediamine, isopropanolamine, triethanolamine, N, N-dimethylformamide, acetone, methylethylketone, cyclohexanone, benzene, 4-methoxy-4-methylpentanone-2, dimethoxymethane,
Dimethoxyethane, 2,4-pentadione, anisole, methyl 3-oxobutanoate, monochlorobenzene,
Toluene, xylene, chloroform, 1,2-dichloroethane, dichloromethane, tetrahydrofuran, dioxane, methanol, ethanol, isopropanol, ethyl acetate, butyl acetate, dimethyl sulfoxide, methyl cellosolve, ethyl cellosolve, methyl cellosolve acetate and the like can be mentioned.

The concentration of each component in the coating liquid is appropriately set according to known techniques. The concentration of the solid content is mainly determined depending on the film thickness of the layer to be formed. In the case of a coating liquid used for producing a single-layer type electrophotographic photosensitive member, and a laminated type electrophotographic photosensitive member. In the case of a coating liquid for forming a charge transport layer in the case of manufacturing, 40 wt% or less, preferably 10
It is adjusted to ˜35 wt% or less. Further, in the case of these coating liquids, the viscosity is generally 150 to 350 cps, preferably 70 to 250 cps, and the film thickness after drying is 15 to 40 μm.

The coating solution is applied to the electrophotographic photoreceptor substrate by a dip coating method. The dip coating method is a conventionally known coating method in which a substrate is dipped in a coating solution, pulled up and dried. In this case, during the coating operation, the solvent evaporates from the surface of the coating liquid in the coating tank, the solid content concentration in the coating liquid rises, the viscosity increases, the coating unevenness and the coating thickness change, and the set film thickness It becomes impossible to obtain a coating film having On the other hand, the present invention adjusts the solid content concentration of the coating solution in the coating tank by adding and mixing the coating solution flowing out of the coating tank through a static mixer with an additional solvent and circulating the mixture in the coating tank. In this way, the solid content concentration of the coating liquid in the coating tank can be maintained constant, and a coating film having uniform coating without uneven coating and having a set film thickness can be obtained. is there.

Specifically, for example, the coating liquid overflowing from the coating tank is supplied to a circulation tank and stored therein, and the coating liquid in the circulation tank is sent to a static mixer using a pump. On the other hand, the solvent stored in the solvent tank is sent to a static mixer using a pump, where the coating solution and the solvent sent from the circulation tank are mixed,
The solvent is added, and the coating liquid having a low solid content is supplied and circulated in the coating tank. As a result, the solid content concentration and viscosity of the coating tank can be kept constant.

The static mixer used in the present invention, as shown in FIG. 2, cuts the spiral blade of a screw feeder known as a powder feeding device at right angles to the axis every half cycle, and the axis is rotated by 90 °. It is a mixer with a structure in which a twisting and spiral blade is fixed to the shaft. Its characteristic is that it is a closed system, so it does not entrain air in the liquid, it has excellent mixing properties, and there are few equipment troubles. It has various characteristics such as. By employing this mixer, the present invention can efficiently and uniformly mix a small amount of a solvent having a small viscosity with a coating liquid having a large viscosity in a large amount and a high concentration. As a result, the solid content concentration of the coating liquid in the coating tank is maintained in a stable state, and there is no coating unevenness.
Moreover, the coating film having the set film thickness is advantageously formed.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory view showing an apparatus of the present invention for dip-coating a photosensitive layer forming coating liquid containing a charge transporting substance, a binder resin and a solvent on an electrophotographic photosensitive member substrate. In the figure, 1 is a coating tank, 11 is a coating solution which overflows from the coating tank, 2 is a circulation tank, 3 is a pump, 4 is a static mixer, 5 is a solvent tank, and 6 is a pump. The coating liquid received at the grate 11 is guided to the circulation tank 2 and stored in the tank. A predetermined amount of the stored coating liquid is sent to the static mixer 4 by the pump 3. On the other hand, the solvent stored in the solvent tank is also sent to the static mixer 4 in a predetermined amount by the pump 6. The coating liquid and the solvent are uniformly mixed together while passing through the static mixer 4, and then fed into the coating tank 1 and circulated. In addition,
The gutter 11 may be a simple outflow pipe provided in the upper part of the coating tank 1.

FIG. 2 is an explanatory view of the static mixer, in which 41 designates a spiral blade (screw),
The spiral blade is fixed, and the liquid to be mixed moves along the spiral blade. The spiral blades 41, 41, ... Are installed so as to be offset by 90.degree. For each one, and the liquid to be mixed is divided into two each time one spiral blade passes. A and B are nozzles, respectively, from which the components to be mixed are introduced. In the case of the present invention, the coating liquid is introduced from the nozzle A and the solvent is introduced from the nozzle B at the same time, and merges.
The combined liquid of the two components of the coating liquid and the solvent is then divided by the spiral blade 41. 2 per spiral blade
Since there are n spiral blades, it is divided into 2
It is divided into ⁿ . The number of spiral blades to be attached is appropriately determined according to need, but is preferably 10 or more in the case of mixing the coating liquid and the solvent in the present invention.

By using this static mixer, since there is no contact with air during the mixing operation, air is not entrained in the coating liquid, which causes quality problems such as CT bubbles and CT twists. There is no fear. Further, generally, it is very difficult to mix a high viscosity liquid and a low viscosity liquid or a large amount liquid and a small amount liquid, but in the present invention using this static mixer, for example, It is possible to favorably perform such an extremely difficult operation of mixing a solvent having a low viscosity of 1 cps with only 20 cc / min into 100 liters / min of a high viscosity of 250 cps.

The method of adjusting the solid content concentration of the coating liquid in the present invention will be described. First, the photosensitive layer forming coating liquid containing the charge transporting substance, the binder resin and the solvent flowing out from the coating tank 1 is introduced into the circulation tank 2. The coating solution in the circulation tank 2 is sent to the static mixer 4 by a constant amount using the pump 3. On the other hand, a fixed amount of the solvent stored in the solvent tank 5 is sent to the static mixer 4 using the pump 6. The coating liquid and the solvent sent to the static mixer 4 merge here, and then the coating liquid is sequentially divided and mixed by a plurality of spiral blades 41, and the solvent is added,
By mixing, a uniform coating solution having a solid content concentration and a viscosity reduced to predetermined values, respectively, is sent to the coating tank 1 and circulated. The viscosity of the coating liquid sent to the static mixer 4 is generally 150 to 350 cps,
On the other hand, the viscosity of the solvent is about 0.5 to 5 cps, and the mixing ratio of the two is, for example, 100 to 50,000: 1, preferably 1,000 to 10,000: 1. By mixing at this mixing ratio, a predetermined viscosity and solid content concentration of the coating liquid can be obtained.

This circulation operation may be performed in a batch system or continuously depending on the amount of solvent evaporated from the surface of the coating liquid in the coating tank 1 and the amount of the coating liquid used. In the circulation tank 2, the coating liquid is uniformly mixed by a stirrer installed in the circulation tank 2 in order to prevent uneven viscosity caused by solvent evaporation from the surface of the coating liquid in the coating tank 1 and the circulation tank 2, for example. It

According to the present invention, it is possible to easily maintain a good state of the coating liquid in the coating tank, that is, to maintain a desired value without changing the solid content concentration and the viscosity, and to keep it uniform.
It is possible to prepare a good coating liquid without inclusion of bubbles, to form a uniform coating film on the electrophotographic photoreceptor substrate without coating unevenness, and to form a coating film having a set film thickness. There is no fear of causing quality problems such as twisting.

[0022]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples unless it exceeds the gist. Example 1 In this example, the apparatus shown in FIG.
An operation of mixing a solvent of 20 cc / min in the circulating amount of the coating liquid of liter / min was performed. As the coating liquid, a coating liquid for forming a charge transport layer composed of a polycarbonate resin, a hydrazone compound and tetrahydrofuran was used, and as a solvent, tetrahydrofuran was used.

First, the viscosity of the circulating tank 2 is about 200c.
100 liters / min of the coating solution of ps, 20 cc / min of the solvent having a viscosity of about 2 cps from the solvent tank 5 are supplied to the static mixer 4 using a pump, passed through and mixed to obtain a predetermined viscosity, and the coating tank Supply to 1. The static mixer used was one equipped with 12 spiral blades.

The cylindrical substrate has an outer diameter of 100 m.
An aluminum tube having a length of m, a length of 340 mm, and a wall thickness of 1.5 mm was used. Also, in the immersion treatment, 1500 mm
It was dipped at a speed of / min and pulled up at a speed of 200 mm / min to form a charge transport layer having a film thickness of 20 μm after drying. As a result of observing the obtained charge transport layer, it was a good coating film without coating defects such as coating streaks, uneven flow, and uneven horizontal steps. This operation was appropriately repeated to obtain a good substrate on which a coating film having no quality unevenness was formed.

Comparative Example 1 The spiral blade of the static mixer 4 in FIG. 1 was removed, and dip coating was performed using the coating liquid and solvent having the same composition as in Example 1. In this case, the solvent was supplied to the circulation tank 2, and the mixing in the circulation tank was performed for 10 minutes using a stirrer. As a result, uneven coating on the substrate surface, C
T-bubble defects were seen.

[0026]

As described above, according to the dip coating method in the manufacturing process of the electrophotographic photosensitive member according to the present invention,
Since a high-viscosity coating liquid such as the coating liquid for forming the charge transport layer and a small amount of solvent can be mixed rapidly and satisfactorily, and stable conditions of the coating liquid in the coating tank can be maintained well, It is possible to form a coating film that is uniform and has a set film thickness without uneven coating on the surface of the body substrate.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an example of a dip coating device of the present invention.

FIG. 2 is a schematic view showing an example of a static mixer used for carrying out the present invention.

[Explanation of symbols]

 1 coating tank 2 circulation tank 4 static mixer 5 solvent tank

Claims (3)

[Claims] 1. A charge transport material on an electrophotographic photoreceptor substrate,
In a method of applying a coating solution for forming a photosensitive layer containing a binder resin and a solvent by a dip coating method, the coating solution flowing out of the coating tank is added to a solvent through a static mixer together with an additional solvent, and mixed into a coating tank. A dip coating method, wherein the solid content concentration of the coating liquid in the coating tank is adjusted by circulating the liquid. 2. The dip coating method according to claim 1, wherein the outflowing coating liquid is guided to and stored in a circulation tank, and the coating liquid in the circulation tank is supplied to a static mixer using a pump. 3. An electrophotographic photoconductor substrate is dipped and a coating tank for coating a coating solution for forming a photosensitive layer is provided.
A circulation tank for storing the coating liquid, a pump for feeding the coating liquid in the circulation tank to a static mixer, a solvent tank, a pump for feeding the solvent in the solvent tank to the static mixer, and a static mixer for mixing the coating liquid and an additional solvent. An apparatus for dipping and coating a coating solution for forming a photosensitive layer containing a charge transport substance, a binder resin and a solvent on an electrophotographic photoreceptor substrate, which is characterized by being provided.