JP2003010751A - Dip coater and apparatus for manufacturing photoreceptor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a uniform coating film by preventing producing bubbles to prevent the deviation of the thickness with a simple constitution. SOLUTION: A bag like variable volume body 13 made of a non-expansible material is provided at the lower end part of a base body holding part 10 for holding the inside surface of a conductive base body 9 and when the conductive base body 9 is dipped into a coating vessel 3, the bag like variable volume body 13 is expanded and when the conductive base body 9 is pulled up from the coating vessel 3, the bag like variable volume body 13 is shrunk to absorb the volume increased by the evaporation of the coating liquid 2 to surely prevent producing the bubbles when the conductive base body 9 is pulled up from the coating vessel 3 and the occurrence of thickness ununiformity of the coating film formed on the surface of the conductive base body 9 is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dip coating apparatus for forming a coating film on the surface of various products, and an apparatus for producing a photoconductor used in an electrophotographic image forming apparatus, and more particularly to a coating film thickness adjusting apparatus. It is related to homogenization.

[0002]

2. Description of the Related Art In an electrophotographic copying machine or the like, an electrostatic latent image is formed on a photosensitive member by exposing the surface of the photosensitive member whose surface is uniformly charged with writing light according to an image to be formed. A toner is attached to the formed electrostatic latent image to make it visible. This toner image is transferred to recording paper and fixed by heat and pressure to form an image on the recording paper. The toner remaining on the photoconductor that has transferred the toner image onto the recording paper is removed by a cleaning unit.

When this photosensitive member is manufactured, a conductive material formed in a cylindrical shape with aluminum or the like in the dip coating tank while keeping the liquid level of the dip coating tank filled with the coating liquid for forming the photosensitive layer or the like constant. The substrate is immersed in the substrate elevating device, the conductive substrate is pulled up from the coating tank at a constant speed, the pulled conductive substrate is stopped, and the coating of the photosensitive layer on the surface of the conductive substrate is naturally dried until it is touch-dried. Then, a method of completely drying in an oven or the like is adopted thereafter.

At the time of pulling up the dip coating, the volume of air trapped inside the conductive substrate increases with the evaporation of the coating liquid of the paint, and the volume of air inside the conductive substrate is larger than the volume inside the conductive substrate. Then, bubbles are generated from the lower part of the conductive substrate. These bubbles burst on the paint surface and disturb the liquid surface of the paint, causing unevenness in the thickness of the coating film. When an image is formed using the photoconductor in which the thickness of the coating film such as the photosensitive layer is uneven as described above,
Image unevenness, white spots, or background stains due to toner adhesion may cause image quality deterioration. Various methods have been adopted to prevent uneven thickness due to the generation of bubbles.

For example, as shown in Japanese Patent Application Laid-Open No. 58-186472, when the internal pressure of the dip coating tank becomes higher than a predetermined value, a solenoid valve is operated to keep the internal pressure at a predetermined value so that air bubbles are generated. To prevent the occurrence,
As disclosed in Japanese Patent No. 4467 and Japanese Patent Application Laid-Open No. 60-132678, a valve is provided in the upper closing device as a pressure adjusting mechanism so that the liquid surface of the coating material that has entered the conductive substrate when the conductive substrate is pulled up is conductive. The air pressure inside the substrate is adjusted to prevent the generation of bubbles. In addition, JP-A-60-2551
As disclosed in Japanese Patent Publication No. 64-64, a pressure balance device for changing the volume by changing the pressure inside the conductive substrate prevents the generation of bubbles, and as disclosed in Japanese Patent Publication No. 6-51148, a supporting member for the conductive substrate. A variable volume (balloon made of elastic material such as rubber) that can be expanded and contracted and deformed inside the chamber is used to absorb the rise in pressure inside the conductive substrate by changing the internal volume of the conductive substrate and prevent the generation of bubbles. Alternatively, as disclosed in Japanese Patent Application Laid-Open No. 10-314637, a movable member for sealing and supporting the upper end of the conductive substrate and adjusting the volume in the conductive substrate by a supporting member for immersing the conductive substrate in the coating liquid. A member is provided to adjust the inner volume of the conductive substrate to prevent the generation of bubbles.

[0006]

However, as disclosed in JP-A-58-186472, when the internal pressure of the dip coating tank is detected and the internal pressure is maintained at a predetermined value, the internal pressure is detected. Therefore, a pressure sensor for adjusting the internal pressure, an electromagnetic valve for adjusting the internal pressure, and an auxiliary device such as an electric circuit for controlling these are required, which complicates the equipment and mechanism.

Further, as shown in JP-A-59-4467 and JP-A-60-132678, the liquid level of the paint that has entered the conductive substrate by opening the valve at the time of pulling up the conductive substrate. When adjusting the air pressure in the conductive substrate, it is difficult to evacuate a certain amount of air because it is difficult to adjust the timing of opening the valve.Therefore, the air is evacuated too much to waste the coating liquid, or the air deficiency is insufficient. Bubbles may be generated. In addition, when the air vent pipe is clogged with coating liquid, or the air vent pipe or pressure control valve leaks air and the liquid enters the air vent pipe and becomes clogged, it takes a lot of time to restore the coating. Work is stagnant.

Further, as shown in JP-A-60-255164, when the volume in the conductive substrate is adjusted by a mechanical pressure balance device by the pressure in the conductive substrate, the mechanism becomes complicated. Will end up.

Further, as disclosed in Japanese Patent Publication No. 6-51148, when the volume in the conductive substrate is freely changed by a balloon made of an elastic material such as rubber, the rate of decrease of the internal volume is the contraction rate of the elastic material, that is, Depending on the material, variations in the properties of each material and changes in the elastic coefficient due to fatigue of the material make it difficult to control in a timely manner. Also, since the amount of air removed is determined by the expanded volume of the stretchable material, the volume that expands is not constant due to variations in the properties of each material and changes in the elastic coefficient due to fatigue of the material,
It is difficult to control the ideal air bleeding amount, and there is a possibility that air is deflated too much to waste the coating liquid, or air deficiency is insufficient to generate bubbles. Further, the elastic material such as rubber repeatedly expands and contracts to cause fatigue, which requires replacement and is not easy to manage. Further, as shown in Japanese Patent Laid-Open No. 10-314637, when the volume inside the conductive substrate is adjusted by a movable member,
Since an air cylinder, a solenoid coil, a motor or the like is attached as a driving device, the device becomes complicated. Also,
Since the upper end of the conductive base is sealed, the volume inside the conductive base increases and the amount of evaporation increases, and the variation in the amount of evaporation increases, making it unsuitable for controlling the absorption of the increase in the internal volume of the conductive base. .

The present invention solves the above drawbacks and provides a dip coating apparatus capable of forming a uniform coating film by reliably preventing the generation of bubbles with a simple structure and preventing unevenness in the thickness of the coating film. It is an object of the present invention to provide a photoconductor manufacturing apparatus.

[0011]

A dip coating apparatus according to the present invention includes a coating tank filled with a coating liquid, a coating material holding portion for holding an inner surface of a cylindrical coating material, and a coating material holding portion. In a dip coating apparatus having an elevating device that raises and lowers a part to immerse the held material to be coated in a coating tank and lifts the dipped material to be coated, the material holding portion for holding the inner surface of the material to be coated is A bag-shaped variable volume made of non-stretchable material is provided at the lower end, and when the material to be coated is dipped in the coating tank, the bag-shaped variable volume is inflated and when the material to be coated is pulled up from the coating tank Characterized by contracting the body.

It is desirable that the side surface of the bag-shaped variable volume body has a bellows structure.

Further, it is preferable that a pressurized fluid is supplied into the bag-shaped variable volume body to expand the bag-shaped variable volume body, and the supplied pressurized fluid is sucked and discharged to contract the bag-shaped variable volume body.

Further, the bag-shaped variable volume body may be contracted by expanding the bag-shaped variable volume body by the elastic force of the elastic body and sucking and discharging the internal air.

The photoconductor manufacturing apparatus according to the present invention has the above-mentioned dip coating apparatus. The coating tank is filled with a coating solution for forming a photoconductor material, and the conductive substrate is immersed in the coating tank to obtain the conductive material. It is characterized in that the substrate is pulled up to form a photosensitive layer on the surface of the conductive substrate.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION As shown in the block diagram of FIG. 1, a dip coating apparatus 1 of the present invention is provided on a base 4 and a coating tank 3 filled with a coating liquid 2 for forming a photosensitive material. A lift screw 5, a lift motor 6 that rotates the lift screw 5, a lift 7 that moves up and down by the rotation of the lift screw 5, an arm 8 provided on the lift 7, and a lower portion of the tip of the arm 8.
It has a substrate holding portion 10 for holding a cylindrical conductive substrate 9 forming a photoconductor. The base body holding portion 10 has a support member 11 provided under the arm 8, an elastic member 12 formed in a cylindrical shape, and a bag-shaped variable capacitance body 13 formed of a non-stretchable material such as a bellows. The support member 11 includes a hollow cylindrical portion 111, a holding portion 112 including a collar provided at an upper end portion of the cylindrical portion 111, the holding portion 112, and the cylindrical portion 111.
A vent pipe 113 is provided so as to penetrate therethrough. A plurality of holes 114 are provided in the middle portion of the cylindrical portion 111.
The holding portion 112 has a fluid supply / exhaust pipe 115 that is electrically connected to the hollow portion of the cylindrical portion 111. The upper end of the elastic member 12 is fixed to the holding portion 112 of the support member 11 by the upper fixing member 14, and the lower end of the elastic member 12 is attached to the lower portion of the cylindrical portion 111.
It is fixed by. The bag-shaped variable capacitance body 13 is fixed to the lower fixing member 15 by a fixing member 16 via a packing 17. A variable volume adjusting spacer 18 is provided at the lower end of the lower fixing member 15 to which the bag-shaped variable capacitance body 13 is fixed. The vent pipe 113 is connected to the fluid supply pump 20 and the fluid discharge pump 21 via the switching valve 19.

The cylindrical conductive substrate 9 is made of aluminum,
Drums and sheets of metal such as copper, iron, zinc, nickel, aluminum on paper, plastic or glass,
Deposit metal such as copper, gold, silver, platinum, palladium, titanium, nickel-chromium, stainless steel, copper-indium, deposit conductive metal oxide such as indium oxide, tin oxide, etc. Or carbon black, indium oxide, tin oxide-antimony oxide powder, metal powder, copper iodide, etc. dispersed in a binder resin and subjected to conductive treatment to form a drum, sheet or plate. Known materials such as the above can be used.

Further, if necessary, the surface of the conductive substrate 9 can be subjected to various treatments within a range that does not affect the image quality. For example, surface oxidation treatment, chemical treatment, coloring treatment or the like can be performed. Further, an undercoat layer can be provided between the conductive substrate 9 and the charge generation layer. This undercoat layer prevents the charge from the conductive substrate 9 to the photosensitive layer in the photosensitive layer having a laminated structure at the time of charging. It shows an action as an adhesive layer that prevents the injection and integrally holds the photosensitive layer to the conductive substrate 9, and an action of preventing reflected light from the conductive substrate 9.

The resin used for the undercoat layer is polyethylene, polypropylene, acrylic resin, methacrylic resin,
Polyamide resin, vinyl chloride resin, vinyl acetate resin, phenol resin, epoxy resin, polyester resin, alkyd resin, polycarbonate, polyurethane, polyimide resin, vinylidene chloride resin, polyvinyl acetal resin, vinyl chloride-vinyl acetate copolymer, polyvinyl alcohol, Known resins such as water-soluble polyester, nitrocellulose, casein, and gelatin can be used. The thickness of the undercoat layer is 0.01 to 10 μm, preferably 0.3 to 7 μm. Examples of the coating method used when forming the undercoat layer include blade coating method, wire bar coating method, spray coating method, dip coating method, bead coating method, air knife coating method, curtain coating method and the like. .

The charge generating layer (carrier generating layer) is, for example, an azo dye such as a monoazo dye, a disazo dye, a trisazo dye, a perylene anhydride, a perylene dye such as perylene imide, an indigo dye such as indigo or thioindigo, Anthraquinone, polycyclic quinones such as pyrenequinone and flapanthurones, quinagridone dyes, bisbenzimidazole dyes, indusulon dyes, squarylium dyes, metal phthalocyanines, phthalocyanine pigments such as metal-free phthalocyanines, pyrylium salt dyes, Dissolving or dispersing various known charge generating substances (carrier generating substances), such as a eutectic complex formed from a thiapyrylium salt dye and a polycarbonate, in a solvent together with a suitable binder resin and, if necessary, a charge transporting substance (carrier transporting substance). Application It can be formed by Rukoto.

As a method for dispersing the charge generating substance in the resin, a ball mill dispersion method, an attritor dispersion method, a sand mill dispersion method or the like can be used. At this time, the charge generating substance has a volume average particle diameter of 5 μm or less, preferably 2 μm.
It is effective to set the particle size to m or less, and optimally 0.5 μm or less. As a solvent used for dispersing these, methanol, ethanol, n-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, cyclohexanone, methyl acetate, dioxane, Ordinary organic solvents such as tetrahydrofuran, methylene chloride, chloroform 1,2-dichloroethane, monochlorobenzene and xylene may be used alone or in combination of two or more. The thickness of the charge generation layer is generally 0.1 to
5 μm, preferably 0.2-2 μm is suitable.

The charge transport layer is formed by incorporating the charge transport material in a suitable binder. As the charge transport material, 2,5-bis (p-diethylaminophenyl)-
Oxazoazole derivatives such as 1,3,4-oxadiazole, 1,3,5-triphenyl-pyrazoline, 1-
[Pyridyl- (2)]-3- (p-diethylaminostyryl) -5- (p-diethylaminophenyl) pyrazolin and other pyrazoline derivatives, triphenylamine, styryltriphenylamine, dibenzylaniline and other aromatic tertiary compounds Amino compound, N, N'-diphenyl-N,
Aromatic tertiary diamino compounds such as N'-bis (3-methylphenyl) -1,1-biphenyl-4,4'-diamine, 3- (4'-dimethylaminophenyl) -5,6
-Di- (4'-methoxyphenyl) -1,2,4-triazine and other 1,2,4-triazine derivatives, 4-diethylaminobenzal, dehydrat-1,1-diphenylhydrazone and other hydrazone derivatives, 2- Phenyl-4-
Quinazoline derivatives such as styryl-quinzoline, benzofuran derivatives such as 6-hydroxy-2,3-di (p-methoxyphenyl) -benzofuran, α such as p- (2,2-diphenylvinyl) -N, N-diphenylaniline -Stilbene derivative, enamine derivative, carbazole derivative such as N-ethylcarbazole, poly-N-vinylcarbazole such as poly-N-vinylcarbazole and its derivative, poly-γ-carbazolylethylglutanate and its derivative, and Pyrene, polyvinylpyrene, polyvinylanthracene, polyvinylacridine,
Known charge transport materials such as poly-9-biphenylanthracene, pyrene-formaldehyde resin, ethylcarbazole formaldehyde resin can be used. Further, these charge transport materials can be used alone or in combination of two or more.

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 are used. , 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. Further, these binder resins may be used alone or in combination of two or more.

The compounding ratio (weight ratio) of the charge transport material and the binder resin is preferably 10: 1 to 1: 5. The thickness of the charge transport layer is generally 5 to 50 μm, preferably 10 to 3
0 μm is suitable.

As the solvent used when the charge transport layer is provided, aromatic hydrocarbons such as benzene, toluene, xylene and chlorobenzene, ketones such as acetone and 2-butanone, methylene chloride, chloroform and chloride. Ordinary organic solvents such as halogenated aliphatic hydrocarbons such as ethylene and cyclic or linear ethers such as tetrahydrofuran and ethyl ether can be used alone or in combination of two or more.

The coating liquid 3 of the photoconductor material is filled in the coating tank 3, and the elevator motor 6 is driven to descend the elevator, and the conductive substrate 9 held by the substrate holder 10 is held.
Is immersed in the coating liquid 2 in the coating tank 3. This conductive substrate 9
Is pulled up from the coating tank 3 at a constant speed to form a coating film of the photosensitive material on the surface of the conductive substrate 9. When the conductive substrate 9 is held by the substrate holding portion 10, a fluid such as pressurized air is supplied from the fluid supply / exhaust pipe 115 to the hollow portion of the cylindrical portion 111 of the substrate holding portion 10, and the supplied fluid forms a cylindrical shape. The elastic member 12 is expanded and pressed against the inner surface of the conductive substrate 9 to hold the conductive substrate 9.

When the conductive substrate 9 held by the substrate holding portion 10 is dipped in the coating liquid 2, as shown in FIG. 2A which is a detailed view of the portion A of FIG. The supply pump 20 is switched to the arm, the fluid such as the pressurized air is supplied from the fluid supply pump 20 into the bag-shaped variable volume body 13 through the vent pipe 113, and the bag-shaped variable volume body 13 is expanded to conduct electricity. The inner volume of the elastic substrate 9 below the elastic member 12 is reduced. In this state, the conductive substrate 9 is immersed in the coating liquid 2. Then, when pulling up the conductive substrate 9 from the coating liquid 2,
By switching the switching valve 19 to the fluid discharge pump 21 side, the expanded fluid in the bag-shaped variable volume body 13 is discharged by the fluid discharge pump 21, and as shown in FIG.
3 is contracted to increase the inner volume of the conductive substrate 9 below the elastic member 12. In this way, when the conductive substrate 9 is pulled up from the coating liquid 2, the bag-shaped variable volume 13 is contracted to increase the inner volume of the conductive substrate 9, thereby absorbing the volume increased by the evaporation of the coating liquid 2. Therefore, it is possible to reliably prevent the generation of bubbles, and it is possible to prevent the coating film formed on the surface of the conductive substrate 9 from having uneven thickness. Further, since the bag-shaped variable volume body 13 prevents the coating tube 2 from contacting the coating liquid 2, the vent tube 113 for supplying and discharging the fluid for expanding and contracting the bag-shaped variable volume body 13 is applied. It is possible to prevent the suction and clogging.

In the above example, the case where the bag-shaped variable capacitance body 13 is inflated by the pressure of the fluid supplied from the fluid supply pump 20 has been described, but as shown in FIG. 3, the bag-shaped variable capacitance body 13 and the variable volume adjustment spacer are shown. A spring 22 is provided between 18, and when the bag-shaped variable capacitance body 13 is inflated by the elastic force of the spring 22 and the bag-shaped variable capacitance body 13 is contracted, the air in the bag-shaped variable capacitance body 13 is discharged by a fluid discharge pump. The bag-shaped variable capacitance body 13 may be contracted by suctioning at 21 to reduce the pressure inside the bag-shaped variable capacitance body 13. By expanding the bag-shaped variable capacitance body 13 by the elastic force of the spring 22 in this way, the fluid supply pump 20 can be omitted, and the configuration of the entire apparatus can be simplified.

[0029]

Example A coating liquid 2 for forming a photosensitive material was prepared as shown below. (1) Coating Solution for Forming Undercoat Layer Coating Solution 2 for forming the undercoat layer was prepared by dissolving 5 parts by weight of soluble nylon (Alamine CM-8000, manufactured by Toray) in 95 parts by weight of methanol. (2) Coating Solution for Forming Charge Generation Layer 10 parts by weight of a charge generation agent having the following structural formula, 7 parts by weight of polyvinyl butyral and 145 parts by weight of tetrahydrofuran were put 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 that has been dispersed is further diluted with cyclohexanone,
This was adjusted to obtain coating liquid 2 for the charge generation layer.

[0030]

[Chemical 1]

(3) Coating Solution for Forming Charge Transport Layer 7 parts by weight of a charge transport agent having the following structural formula and 10 parts by weight of polycarbonate (Panlite C-1400, manufactured by Teijin Kasei) were added to 83 parts by weight of dichloromethane. Coating solution 2 for the charge transport layer was prepared by dissolving.

[0032]

[Chemical 2]

Then, using an aluminum conductive substrate 9 having an outer diameter of 80 mm and a length of 360 mm, the undercoat layer coating solution 2 prepared as described above is dip-coated and dried at 100 ° C. for 10 minutes. An undercoat layer having a thickness of 0.3 μm was formed. Next, a dipping coating was sequentially applied to the coating solution for the charge generation layer and the coating solution for the charge transport layer on this surface to prepare a photoreceptor. At this time, the pulling rate is 0.2 μm for the dry layer of the charge generation layer and 2 for the charge transport layer.
Twelve photoconductors were manufactured under the condition of 8 μm. Further, as a comparative example, the bag-shaped variable capacitance body 13 was not provided, and the venting amount was adjusted with time. As a result, in the case of the example, it was easy to adjust the amount of degassing, and it was possible to degas all 12 pieces uniformly. Further, even when the coating operation was continuously performed, the generation of bubbles was prevented, and a coating film having a uniform film thickness could be formed. On the other hand, in the case of the comparative example, it was not easy to adjust the degassing amount, and it was difficult to uniformly degas all 12 pieces. Further, when the coating operation was continuously performed, bubbles were generated, and the coating film had uneven thickness.

[0034]

As described above, according to the present invention, a bag-shaped variable volume body made of a non-stretchable material is provided at the lower end of the coated material holding portion that holds the inner surface of the coated material, and the coated material is placed in the coating tank. When immersed, the bag-shaped variable volume is expanded, and when the material to be coated is pulled up from the coating tank, the bag-shaped variable volume is contracted. The volume increased by evaporation can be absorbed to reliably prevent the generation of bubbles, and it is possible to prevent the coating film formed on the surface of the coating material from having uneven thickness.

Further, by forming the side surface of the bag-shaped variable volume body in a bellows structure, the bag-shaped variable volume body can be easily expanded and contracted.

Further, by supplying a pressurized fluid into the bag-shaped variable volume body to expand the bag-shaped variable volume body, sucking and discharging the supplied pressurized fluid to contract the bag-shaped variable volume body, It is possible to prevent the coating liquid from being sucked and discharged when the variable volume body is contracted, and the coating liquid can be effectively used.

Further, the bag-shaped variable volume body is expanded by the elastic force of the elastic body, the internal air is sucked and discharged, and the bag-shaped variable volume body is contracted, whereby the structure of the entire apparatus can be simplified. .

Further, by manufacturing a photoreceptor used in an electrophotographic image forming apparatus using the above dip coating apparatus, a photosensitive layer having a uniform thickness and no film unevenness can be formed. A high quality image can be stably formed.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a dip coating apparatus of the present invention.

FIG. 2 is a cross-sectional view showing an operating state of the bag-shaped variable volume body of the dip coating device.

FIG. 3 is a cross-sectional view showing another configuration of the bag-shaped variable volume body of the dip coating device.

[Explanation of symbols]

1; dip coating device, 2; coating liquid, 3; coating tank, 4; base, 5; lifting screw, 6; lifting motor, 7; lift, 8;
Arm, 9; conductive base, 10; base holding part, 11; support member, 12; elastic member, 13; bag-shaped variable capacitance body, 1
4; upper fixing member, 15; lower fixing member, 16; fixing member, 17; packing, 18; variable volume adjusting spacer, 1
9; switching valve, 2; fluid supply pump, 21; fluid discharge pump, 111; cylindrical portion, 112; holding portion, 113; vent pipe, 114; hole.

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Claims (5)

[Claims] 1. A coating tank filled with a coating liquid, a coating material holding portion for holding an inner surface of a cylindrical coating material, and a coating material holding portion moved up and down to hold the coating material held therein. In a dip coating device that has a lifting device that lifts the dipped coating material, a bag-shaped variable volume body made of non-stretchable material is provided at the lower end of the coating material holding part that holds the inner surface of the coating material. A dip coating apparatus which expands the bag-shaped variable volume when the material to be coated is dipped in the coating tank and contracts the bag-shaped variable volume when the material to be coated is pulled up from the coating tank. 2. The dip coating apparatus according to claim 1, wherein the bag-shaped variable volume body has a bellows structure on its side surface. 3. The bag-shaped variable volume body is supplied with a pressurized fluid to expand the bag-shaped variable volume body, and the supplied pressurized fluid is sucked and discharged to contract the bag-shaped variable volume body. Or the dip coating device according to 2. 4. The dip coating apparatus according to claim 1, wherein the bag-shaped variable volume body is expanded by an elastic force of an elastic body, and internal air is sucked and discharged to contract the bag-shaped variable volume body. 5. A dip coating apparatus according to claim 1, wherein the coating tank is filled with a coating liquid for forming a photosensitive material,
An apparatus for producing a photoconductor, comprising: immersing a conductive substrate in a coating tank and pulling up the conductive substrate to form a photosensitive layer on the surface of the conductive substrate.