JPH07155663A - Immersion coating apparatus - Google Patents

Abstract

PURPOSE:To prevent occurrence of a coating defect due to break of a film formed in the lower end of a hollow cylindrical article to be coated at the time of immersion- coating by providing a system to forcibly break the film of a coating liquid formed at the lower end of the article to be coated just after the object article is parted from the coating liquid surface. CONSTITUTION:A photosensitive drum 1, which is an article to be coated, is immersed in a coating liquid 4 in a coating tank 10 and coated with the liquid and just after the lower end of the drum 1 is parted from the coating liquid surface, a liquid film 3 of the coating liquid is formed at the lower end of the drum 1. The liquid film 3 is forcibly broken by opening a solenoid valve 14 based on a signal from a controlling apparatus 21 to control the position signal of the drum 1 and communicating a pipeline 13 with a suction apparatus or a compressed fluid supplying apparatus 15 wherein the solenoid valve 14 is set in the middle of the pipeline 13 for ventilation communicating with the space surrounded by the liquid film 3 and a closed apparatus 9. For example, the liquid film 3 at the lower end of the drum 1 is expanded toward the coating liquid surface by sending a compressed fluid and shifts to the coating liquid side attributed to the cohering force of the coating liquid itself and thus the liquid film 3 is broken and disappears.

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 coating a photoconductor coating solution on a tube of an electrophotographic photosensitive drum used in an electrophotographic apparatus such as a copying machine or a laser beam printer. is there.

[0002]

2. Description of the Related Art In electrophotographic copying machines and laser beam printers, a cylindrical electron is formed by coating a photosensitive layer (in many cases, a multilayer) on the outer peripheral surface of a hollow cylindrical drum made of metal such as aluminum. A photographic photoreceptor is used. As the coating method of the photosensitive layer, a coating method such as a dip coating method, a spray coating method, a spin coating method, a bead coating method, a wire bar coating method, a blade coating method, a roller coating method or a curtain coating method can be used. However, since it is possible to easily apply a plurality of pieces at the same time (hereinafter, referred to as a multi-piece application), the mass application is excellent, and the dip coating method is often used because the apparatus is simple.

In the dip coating method, the coating liquid is filled in the coating tank, the inside of the hollow cylindrical object to be coated is grasped, and after dipping to a predetermined position, the object to be coated is moved upward relative to the coating tank. Application is performed by moving.

In order to obtain a uniform coating film by using this dip coating method, in addition to moving the object to be coated or the coating tank up and down relatively smoothly, foreign matter on the coating surface and the coating film after coating are applied. It is necessary to avoid adhesion of excess coating liquid droplets.

In order to prevent foreign matter from adhering to the coating surface, it is customary to carry out the dip coating step in clean air. Further, as disclosed in Japanese Patent Application Laid-Open No. 1-63065, a method is adopted in which a drive unit is not installed directly above a coating process.

There is no prior art relating to a method for preventing extra coating liquid droplets from adhering to a coating film after coating,
There is no mention of preventing the coating liquid droplets from adhering due to the rupture of the coating liquid film at the lower end of the hollow cylindrical object to be coated. For example, Japanese Examined Patent Publication (Kokoku) No. 62-54065 discloses a method of pulling up an object to be coated without separating it from the liquid surface of the coating liquid.
Japanese Patent Publication No. 4-4034 discloses a method of adjusting the pressure of the space on the inner surface of the hollow cylindrical object whose one end is hermetically gripped at the time of application, but prevents the application liquid droplets from adhering. It does not mention how to do it.

Further, as a method for preventing the pooling of the coating liquid at the lower end of the hollow cylindrical object to be coated, Japanese Patent Laid-Open No. 63-12371 discloses pulling up the hollow cylindrical object to be coated near the end. Method of reducing speed, JP-A-63-63
-20072, a method of temporarily stopping the pulling operation immediately before or after the hollow cylindrical object to be coated separates from the liquid surface of the coating liquid; JP-A-3-255451 discloses a hollow cylindrical shape. A method is disclosed in which the pulling speed immediately before the coating object separates from the liquid surface of the coating liquid is set to be slower than the pulling speed until then, but these are all coating films of the coating liquid at the lower end of the hollow cylindrical coating material. Although no mention is made of prevention of tension, and even if there is an effect of prevention of membrane tension, problems such as complicated pulling control and reduced productivity will occur.

[0008]

In the step of applying the coating solution for a photoreceptor onto the tube of the electrophotographic photoreceptor drum by the dip coating method, film coating of the coating solution at the lower end of the drum occurs stochastically. Those with a large drum inner diameter, for example, those with a drum inner diameter of 60 mm or more, film formation is unlikely to occur, and those with a small drum inner diameter, for example, the drum inner diameter of 30 mm
The following things tend to cause filming.

When the film of the photoconductor coating liquid formed at the lower end of the pipe of the photoconductor drum, which is the object to be coated, is ruptured during the dip coating process, the film of the coating liquid is formed even if only one pipe is coated. The coating liquid droplets generated by the rupture of the polymer may adhere to the surface of the coating film of its own, resulting in a coating film defect. In the multi-coating application process, in addition to the case of single-coating, the droplets of the coating liquid for photoconductor adhered to each other on the coating surface of the adjacent tube to form a coating film defect. There was a problem that it ended up.

In order to prevent film tension at the lower end of the drum,
Adding an additive to the photoconductor coating solution is also an effective means, but it cannot be easily adopted because it may adversely affect the photoconductor characteristics.

The problem to be solved by the present invention is that a film formed at the lower end of a hollow cylindrical object to be coated during dip coating using a hollow cylindrical object to be coated without adding a special additive to the coating solution. It is an object of the present invention to provide a dip coating device capable of preventing the occurrence of coating film defects due to the rupture of a coating material.

[0012]

In order to solve the above-mentioned problems, according to the present invention, a hollow cylindrical article to be coated is dipped in the coating solution and then relatively pulled up to form the coating solution on the coating object. A dip coating device for coating, comprising a mechanism for forcibly breaking a film of the coating liquid formed at the lower end of the coating liquid immediately after the coating liquid leaves the liquid surface of the coating liquid. I will provide a.

The dip coating apparatus of the present invention is effective for forming a coating film on the outer peripheral surface of a hollow cylindrical object to be coated, and is particularly effective for manufacturing a cylindrical electrophotographic photosensitive member.

The cylindrical electrophotographic photosensitive member is obtained by forming a subbing layer, if necessary, and then forming a photosensitive layer on a hollow cylindrical conductive support.

Examples of the material of the conductive support include aluminum, copper, zinc, stainless steel, chromium, titanium,
Nickel, molybdenum, vanadium, indium, gold,
Examples include metals or alloys such as platinum, conductive polymers, conductive compounds such as indium oxide; paper, plastic films, ceramics, etc. coated, vapor-deposited or laminated with metals or alloys such as aluminum, palladium and gold. Metallic ones, especially aluminum ones, are preferable. If necessary, the surface of the conductive support may be subjected to chemical or physical treatment.

The photosensitive layer is of a first type in which a charge generating layer mainly composed of a charge generating material and a charge transporting layer mainly composed of a charge transporting material are sequentially laminated, a charge transporting layer and a charge generating layer are successively formed. It may be a laminated second type or a third type in which a charge generating material is dispersed in a charge transfer medium.

For the first type photosensitive layer, a dispersion liquid obtained by vapor deposition of a charge generating material or by dispersing fine particles of the charge generating material in a solvent in which a binder resin is dissolved, is applied and dried. Then, the charge transporting material may be used alone or, if necessary, a binder resin may be used in combination, and a solution in which the binder resin is dissolved is applied and dried.

In the second type of photosensitive layer, a solution in which a charge transport material is used alone or, if necessary, a binder resin is used in combination is applied onto a conductive support, dried, and then a charge is generated thereon. It can be obtained by vapor deposition of a material, or by applying a dispersion obtained by dispersing fine particles of a charge generating material in a solvent or a binder resin solution and drying.

In the third type photosensitive layer, fine particles of the charge generating material are dispersed in a solution in which the charge transporting material is used alone or, if necessary, a binder resin is also used in combination, and this is used as a conductive support. It can be produced by coating on the surface and drying.

Regarding the thickness of the photosensitive layer, in the case of the photosensitive layers of the first and second types, the thickness of the charge generation layer is 5 μm or less, preferably 0.01 to 2 μm, and the thickness of the charge transport layer. The length is 3 to 50 μm, preferably 5 to 30 μm. In the case of the third electrophotographic photosensitive member, the thickness of the photosensitive layer is 3 to 50.
μm, preferably 5 to 30 μm.

The proportion of the charge transport material in the charge transport layer in the first and second type photosensitive layers is 5 to 100% by weight.
Can be appropriately selected within the range of, preferably 40 to 80% by weight. The ratio of the charge generating material in the charge generating layers of the first and second type photosensitive layers is 5 to 5.
It can be selected appropriately in the range of 100% by weight, and preferably in the range of 40 to 80% by weight. The proportion of the charge transporting material in the third type photosensitive layer can be appropriately selected within the range of 5 to 99% by weight, and the proportion of the charge generating material is 1 to 50% by weight, preferably 3 to 20% by weight. %. In addition, in any of the first to third photosensitive layers, a plasticizer and a sensitizer can be used together with the binder resin.

Examples of the charge generating material include azo pigments such as monoazo pigments, disazo pigments and trisazo pigments;
Phthalocyanine pigments such as various metal phthalocyanines, metal-free phthalocyanines, and naphthalocyanines; condensed polycyclic pigments such as perinone pigments, perylene pigments, anthraquinone pigments, quinacridone pigments; squarylium dyes; azurenium dyes; thiapyrylium dyes; cyanine dyes And the like.

Particularly, phthalocyanines are suitable because they have high sensitivity in an electrophotographic system using a long wavelength light source such as a semiconductor laser or a light emitting diode.

The charge generating material is not limited to those described here, and may be used alone or in combination of two or more when used.

The charge transport material is roughly divided into low molecular weight compounds and high molecular weight compounds.

Examples of the charge transporting material of the low molecular weight compound include pyrene; carbazoles such as N-ethylcarbazole, N-isopropylcarbazole and N-phenylcarbazole; N-methyl-N-phenylhydrazino-3.
-Methylidene-9-ethylcarbazole, N, N-diphenylhydrazino-3-methylidene-9-ethylcarbazole, p- (N, N-dimethylamino) benzaldehyde diphenylhydrazone, p- (N, N-diethylamino) benzaldehyde diphenyl Hydrazone, 1-
[4- (N, N-diphenylamino) benzylideneimino] -2,3 dimethylindoline, N-ethylcarbazole-3-methylidene-N-aminoindoline, N-ethylcarbazole-3-methylidene-N-aminotetrahydrokyrin Hydrazones such as; oxadiazoles such as 2,5-bis (p-diethylaminophenyl) -1,3,4-oxadiazole; 1-phenyl-3- (p-
Diethylaminostyryl) -5- (p-diethylaminophenyl) pyrazoline, 1- [quinolyl- (2)]-3
Pyrazolines such as-(p-diethylaminophenyl) pyrazoline; tri-p-tolylamine, N, N'-diphenyl-N, N'-bis (3-methylphenyl) -1,
Arylamines such as 1'-biphenyl-4,4'-diamine; 1,1-bis (p-diethylaminophenyl)
Butadiene such as -4,4-diphenyl-1,3-butadiene; 4- (2,2-diphenylethenyl) -N, N
Examples include stills such as -diphenylbenzenamine and 4- (1,2,2-triphenylethenyl) -N, N-diphenylbenzenamine.

Examples of the charge transport material of the polymer compound include poly-N-vinylcarbazole, halogenated poly-N-vinylcarbazole, polyvinylpyrene,
Examples thereof include polyvinyl anthracene, polyvinyl acridine, poly-9-vinylphenyl anthracene, pyrene-formamide resin, ethylcarbazole-formaldehyde resin, triphenylmethane polymer, and polyphenylalkylsilane.

The charge transporting material is not limited to those described here, and may be used alone or in combination of two or more when used.

As the binder resin which can be used if necessary, it is preferable to use a hydrophobic and electrically insulating polymer compound capable of forming a film. Examples of such high molecular weight polymers include polycarbonate, polyester, methacrylic resin, acrylic resin, polyvinyl chloride,
Polyvinylidene chloride, polystyrene, polyvinyl acetate, polyvinyl butyral, styrene-butadiene copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, silicone resin, silicone-alkyd resin, phenol-formaldehyde resin, styrene-alkyd resin, Examples thereof include poly-N-vinylcarbazole, polyvinyl formal, and polysulfone.

The binder resin is not limited to the ones described here, but may be used alone or in combination with the binder resin.
It can be used as a mixture of more than one kind.

Further, in order to improve film-forming property, flexibility and mechanical strength, well-known additives such as plasticizers and surface modifiers may be used together with these binder resins.

Examples of the plasticizer include biphenyl, biphenyl chloride, o-terphenyl, p-terphenyl,
Dibutyl phthalate, diethyl glycol phthalate,
Examples thereof include dioctyl phthalate, triphenyl phosphoric acid, methylnaphthalene, benzophenine, chlorinated paraffin, polypropylene, polystyrene and various fluorohydrocarbons.

Examples of the surface modifier include silicone oil and fluororesin.

Any known sensitizer can be used as the sensitizer for the photosensitive layer, if necessary.

Examples of the sensitizer include chloranil, tetracyanoethylene, methyl violet, rhodamine B, cyanine dye, merocyanine dye, pyrylium dye and thiapyrylium dye.

Further, in order to improve storability, durability and environmental resistance, a deterioration preventing agent such as an antioxidant or a light stabilizer may be contained in the photosensitive layer. Examples thereof include phenol compounds, hydroquinone compounds, amine compounds and the like.

Furthermore, in order to improve the adhesive between the conductive support and the photosensitive layer and to prevent the injection of free charges from the conductive support to the photosensitive layer, a gap between the conductive support and the photosensitive layer is provided. ,
An adhesive layer or a barrier layer can be provided if necessary.

The materials used for these layers include, in addition to the polymer compounds used for the binder resin, casein, gelatin, ethyl cellulose, nitrocellulose,
Carboxy-methyl cellulose, vinylidene chloride-based polymer latex, styrene-butadiene-based polymer latex, polyvinyl alcohol, polyamide, polyurethane, phenol resin, aluminum oxide, tin oxide,
Titanium oxide and the like can be used, but the film thickness is preferably 1 μm or less.

When a laminated type photosensitive layer having a charge generation layer and a charge transport layer is formed by coating, the solvent that dissolves the binder resin varies depending on the kind of the binder resin, but does not dissolve the lower layer. It is desirable to select from among them.
Specific examples of the organic solvent include, for example, methanol,
Alcohols such as ethanol and n-propanol; ketones such as acetone, methyl ethyl ketone and cyclohexanone; amides such as N, N-dimethylformaldehyde and N, N-dimethylacetamide; ethers such as tetrahydrofuran, dioxane and methylcellosolve; acetic acid Esters such as methyl and ethyl acetate; Sulfoxides and sulfones such as dimethyl sulfoxide and sulfolane;
Aliphatic hydrocarbons such as dichloromethane, chloroform, carbon tetrachloride and trichloroethane; aromatics such as benzene, toluene, xylene, monochlorobenzene and dichlorobenzene.

[0040]

The dip coating apparatus of the present invention forcibly, immediately after the detachment, forcibly forms a film of the coating liquid generated when the lower end of the drum is detached from the liquid surface of the coating liquid in the dip coating process of the photosensitive drum as the object to be coated. Explode.

[0041]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in more detail below with reference to embodiments using the drawings.

In the dip coating method, a state immediately after the photosensitive drum is separated from the liquid surface of the coating liquid, and a state in which a film of the coating liquid is spread on the lower end of the drum is shown in FIG. The film coating of the coating liquid on the lower end of the drum occurs stochastically, and the smaller the inner diameter of the drum, the more likely it is to occur.

As shown in FIG. 4, the film coating of the coating liquid on the lower end of the drum is ruptured in the step after the coating liquid is removed, and the generated coating liquid droplets adhere to the coating film surface, resulting in a coating film defect. . The droplets of the film rupture may be attached to the same drum where the film rupture occurs, or may be attached to the adjacent drum in the multi-strand coating. Generally, from the viewpoint of improving the efficiency of the dip coating process,
Since the multiple picking is adopted and the distance between the drums must be narrowed as much as possible, the coating film defect due to the coating liquid droplet adhesion due to the burst of the coating liquid film becomes a serious problem.

Next, the principle of the present invention will be described with reference to FIGS. FIG. 2 shows a space surrounded by a sealing device that prevents the coating liquid from entering the inner surface of the drum and a coating liquid liquid film formed at the lower end of the drum immediately after the drum, which is the object to be coated, separates from the liquid surface of the coating liquid. It shows a state in which the coating liquid film is ruptured to the inner surface side of the drum by removing the gas. According to this method, the droplets generated by the rupture of the coating liquid film at the lower end of the drum fly toward the inner surface of the drum and are not attached to the outer coating surface, which is effective. The timing of venting the gas from the space enclosed by the drum sealing device and the coating liquid film is not exact, but at least before the coating liquid film spontaneously bursts without any operation. Need to do.

FIG. 3 is surrounded by a sealing device which prevents the coating liquid from entering the inner surface of the drum and a coating liquid film formed at the lower end of the drum immediately after the drum, which is the object to be coated, separates from the liquid surface of the coating liquid. By sending a compressive fluid into the space, the coating liquid film stretched in the lower end of the drum is expanded in the direction of the coating liquid surface, and finally brought into contact with the coating liquid surface. As a result, due to the cohesive force of the coating liquid itself, the coating liquid film at the lower end of the drum moves to the coating liquid side of the coating tank and the coating liquid film at the lower end of the drum breaks and disappears. According to this method
Since the coating liquid liquid film at the lower end of the drum once generated is brought into contact with the coating liquid again, the liquid film is broken by utilizing the cohesive force of the coating liquid,
It is possible to suppress the generation of droplets of the coating liquid due to the rupture of the liquid film, and it is possible to prevent the coating liquid droplets from adhering to the coating film surface of the drum surface. In this method, the timing of sending the compressive fluid into the space surrounded by the drum sealing device and the coating liquid film is very important. The reason for this is clear if a drum, which is an object to be coated, is fed with a compressive fluid at a time when the drum is far from the surface of the coating liquid. The coating liquid liquid film pushed down by the compressive fluid bursts because it could not contact the coating liquid in the coating tank, and the generated droplets of the coating liquid were manipulated to rupture the coating liquid liquid film. As compared with the case where the liquid is not added, the liquid scatters more violently, and the probability that the liquid film adheres to the coating film surface of the drum itself that has ruptured or the coating film surface of the adjacent drum increases. Therefore, in the method of feeding the compressible fluid to break the coating liquid film, the distance between the coating liquid film at the lower end of the drum and the coating liquid surface of the coating tank is very important. In the process of pushing down the coating liquid film at the lower end, the liquid film needs to contact the coating liquid surface of the coating tank without rupturing. This distance is preferably 5 mm or less, although it varies depending on conditions such as the properties of the coating liquid and the inner diameter of the drum.

For comparison, FIG. 4 schematically shows how the coating liquid droplets adhere to the coating film surface due to the rupture of the coating liquid liquid film at the lower end of the drum in the conventional multi-take dipping coating method. It is a thing. In FIG. 4, reference numeral 6 denotes a droplet that adheres to the coating film surface of the drum itself when the coating liquid film at the lower end of the drum bursts, and 5 denotes a droplet that adheres to the coating surface of the adjacent drum. ing. As described above, in the multi-coating dip coating method, in addition to 6 droplets, 5 droplets are generated from each drum and adhere to the coating surface of the adjacent drum to cause a coating defect.

FIG. 5 shows one of the embodiments of the present invention. Although FIG. 5 shows a single pick, in the case of multiple picks, it is of course possible to install a mechanism for forcibly breaking the coating liquid film of the present invention for each drum. In FIG. 5, the drum 1 which is the object to be coated is attached to the coating tank 1
It shows the state immediately after the lower end of the drum is separated from the surface of the coating liquid by dip coating in the coating liquid 4 of No. 0. A liquid film of the coating liquid is stretched on the lower end of the drum, which is the object to be coated. This coating liquid liquid film has a solenoid valve 14 installed in the middle of a ventilation pipe 13 which communicates with the space surrounded by the liquid film and the sealing device 8, and a control device 21 for controlling a position signal of the object drum. Opening with a signal from the device causes it to be forcibly broken by the mechanism as described in FIG. 2 or FIG. 3 by being connected to the suction device or the compressive fluid supply device of 15.
The suction device 15 includes a vacuum pump, an ejector,
Examples of the compressive fluid include, but are not limited to, air, nitrogen, carbon dioxide, helium, argon, and the like.

[0048]

According to the dip coating apparatus of the present invention, coating film defects due to the adhesion of coating liquid droplets to the coating film surface caused by the bursting of the coating liquid film at the lower end of the drum generated by the dip coating method,
It can be prevented by forcibly breaking in advance by a method in which the coating liquid droplets do not adhere to the coating film surface. Further, it is possible to effectively prevent the occurrence of coating film defects due to the adhesion of the coating liquid droplets, which tends to occur when the inner diameter of the drum becomes small.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a coating liquid film at the lower end of a drum generated by a dip coating method.

FIG. 2 is a schematic cross-sectional view showing a state in which the coating liquid film at the lower end of the drum is broken by gas suction.

FIG. 3 is a schematic cross-sectional view showing a state in which the coating liquid film is pushed down by the supply of the compressive fluid and is in contact with the coating liquid surface.

FIG. 4 is a schematic cross-sectional view showing a process in which the coating liquid film at the lower end of the drum bursts and the coating liquid droplets adhere to the coating film surface of itself or the adjacent drum.

FIG. 5 is a drawing showing a configuration of an embodiment in the case of single picking of the present invention.

[Explanation of symbols]

 1 Aluminum Hollow Cylindrical Drum 2 Coating Film on Photoreceptor 3 Liquid Film of Coating Liquid 4 Coating Liquid 5 Droplet created by rupturing coating liquid liquid film at the lower end of the drum 6 Made by bursting coating liquid liquid film at the lower end of the drum Droplet 7 Support device 8 Shaft 9 Sealing device 10 Coating tank 11 Coating liquid supply pipe 12 Coating liquid return pipe 13 Aeration pipe 14 Solenoid valve 15 Suction device or compressive fluid supply device 16 Driving device 17 Driving device 18 Motor 19 Belt 20 Pulley 21 Control device 22 Control signal path

Claims (3)

[Claims] 1. A dipping coating apparatus for coating a coating material on a coating liquid by immersing a hollow cylindrical coating material in the coating liquid and then relatively pulling the coating liquid onto the coating liquid. A dip coating apparatus comprising a mechanism for forcibly breaking the film of the coating liquid generated at the lower end of the object to be coated immediately after being separated from the surface. 2. A mechanism for forcibly breaking the film of the coating liquid formed at the lower end of the coating liquid immediately after the coating liquid leaves the surface of the coating liquid prevents the coating liquid from entering the inner surface of the coating liquid. 2. The dip coating device according to claim 1, comprising a mechanism for removing gas from a space surrounded by a sealing device and a film of the coating liquid generated at the lower end of the coating object. 3. A mechanism for forcibly breaking the film of the coating liquid generated at the lower end of the coating liquid immediately after the coating liquid leaves the surface of the coating liquid prevents the coating liquid from entering the inner surface of the coating liquid. 2. The dip coating apparatus according to claim 1, which is a mechanism for increasing a volume of gas in a space surrounded by a sealing device and a film of the coating liquid generated at a lower end of the coating material by supplying a compressive fluid. .