JP4470516B2 - Immersion coating method - Google Patents

Description

  The present invention relates to a method for applying a liquid to a substrate surface, and more particularly to an application method for applying a coating solution to a columnar or cylindrical substrate surface in a short time without unevenness.

  As a method of applying a liquid to the surface of a substrate, a dip coating method is known in which the solution is raised after being immersed in a coating solution. When the liquid is applied to the surface of the cylindrical substrate, the substrate can be easily applied to the surface by simply immersing the substrate in the coating solution and raising it. On the other hand, when the liquid is applied to the surface of the cylindrical body, it is not necessary to apply the liquid, or it is necessary to prevent the liquid from adhering to the inner surface of the cylindrical body because, for example, a movable device is provided inside the cylindrical body. There is a case. In order to apply the liquid to the surface of the cylindrical substrate and prevent the coating liquid from adhering to the inside of the cylindrical body, the inside of the cylindrical body is gripped and the upper end of the cylindrical body is sealed, and the virtual axis of the cylindrical body is A coating method in which the film is lifted after being immersed so as to be substantially perpendicular to the surface is conceivable.

In order for the time required for coating to be short and the liquid applied to the substrate surface to be uniform without unevenness, the speed at which the base is immersed, the speed at which it is raised, the method of supplying the coating liquid and the speed are set. Although it is necessary to strictly control, conventionally, a constant amount of coating solution is supplied to a container containing a coating solution, and the coating solution is always overflowed from the container, so that it is immersed and applied (hereinafter referred to as this, COF method) (for example, refer to Patent Document 1), and a coating method in which the coating solution overflows from the container containing the coating solution only when the substrate to be coated is immersed in the coating solution. (Hereinafter, this may be referred to as IOF method) has been known (see, for example, Patent Document 2).
JP-A-5-337417 JP 2002-49162 A

  However, the following problems are likely to occur in coating by the COF method. That is, (1) The liquid level rises from the end of the coating liquid container due to surface tension and is not stable, so that the liquid level is likely to vibrate and coating unevenness is likely to occur. (2) Evaporation tends to cause uneven coating due to change in liquid concentration. (3) When the difference between the outer diameter of the substrate and the container diameter is 10 mm or more, the coating solution does not overflow uniformly from the container holding the solution. There has been a problem that uneven coating tends to occur.

  The above problems are: (1) Change the liquid feeding device to a type that does not pulsate, or use the optimum outer diameter of the coating container according to the outer diameter of the substrate, and (2) Create the outer wall so that the solvent does not evaporate and remove the solvent. It can be avoided by applying the IOF method that does not allow the reservoir or overflow during application. However, the equipment is large and complicated, such as preparing a coating container for each outer diameter of the substrate and introducing a device that controls the atmosphere during coating to prevent deterioration of the coating shape due to dripping of the coating more than necessary. In the IOF method, even when the substrate is released from the liquid level, the substrate still remains in the container holding the coating solution. There was another problem that productivity could be reduced due to the inability to proceed to this process.

As a result of intensive investigations to solve the above-described problems in the dip coating method, the inventors of the present application have adjusted the liquid feeding speed so that the coating surface can be applied to the coating container without overflowing the coating liquid during coating from the container. It was found that the above problem can be solved by holding the tablet at a certain height under the mouth. That is, (1) liquid level vibration is reduced because the coating liquid does not rise, and (2) the mouth of the container acts as an outer wall to adjust the liquid feeding speed, so that different substrate outer diameters and rising speeds can be obtained. It is possible to control the solvent vapor concentration. (3) If the liquid level is held just below the mouth of the coating container, the decrease in productivity can be suppressed to a minimum, and uniform application without unevenness is possible. In addition, the present inventors have found that the substrate can be detached from the coating solution container in a short period of time after the coating is completed.

  That is, the present invention is a method in which a columnar or cylindrical substrate to be coated is immersed in a coating solution so that its virtual axis is substantially perpendicular to the liquid level, and then the liquid level of the solution is obtained. In a coating method in which the substrate is lifted relatively to the substrate, the rising speed D (mm / min) relative to the liquid level of the substrate, the outer diameter Ds (mm) of the substrate, and a container for holding the coating solution while the substrate is rising In the dip coating method, the relationship represented by the following formula (1) is established when the supply rate of the coating solution to be supplied is V (L / min).

D> V / (1/4 (π · Ds ² )) × 10 ⁶ > 0 (1)

  According to the coating method of the present invention, the coating film is uniform and does not cause unevenness, can be precisely controlled to a desired thickness, and can be coated with high productivity in a short time. The coating method of the present invention can provide a high-quality electrophotographic photosensitive member.

Hereinafter, embodiments of the present invention will be described in detail. However, the description of the constituent elements described below is a representative example of the embodiments of the present invention, and is appropriately modified without departing from the spirit of the present invention. can do.
<Dip coating method>
In the dip coating method of the present invention, for example, a dip device as shown in FIG. 1 is used. The illustrated immersion apparatus (3) is mainly composed of an immersion tank (30) in which the coating liquid is stored and the cylindrical substrate (1) is immersed, and a coating liquid circulation mechanism. The coating liquid stored in the immersion tank (30) is supplied from the coating liquid supply port (31) and overflows from the upper part of the immersion tank (30). The coating liquid overflowed to the receiving toy (32) is sent to the coating liquid tank (33) and stirred, and then supplied again via the supply pump (34). Reference numeral (35) denotes a hood provided as necessary on the dipping tank (30) and the receiving toy (32) for preventing evaporation of the solvent on the coating liquid surface.

  In the dip coating according to the present invention, the cylindrical substrate (1) is vertically lowered and immersed in a dip tank (30) having a structure in which the liquid level of the coating liquid in the case of overflow is maintained constant, and then Then, the cylindrical base body (1) is lifted vertically and lifted. At that time, by controlling the descending and rising speeds of the cylindrical substrate (1), it is possible to prevent vibration of the coating liquid surface around the cylindrical substrate (1) and to prevent coating defects (flow unevenness). Is the rising speed D (mm / min) relative to the liquid level, the outer diameter Ds (mm) of the cylindrical substrate, and the amount of coating liquid supplied to the container holding the coating solution during the rise is V (L / min). In this case, by applying the relationship represented by the following formula (1), uniform coating without unevenness can be performed.

D> V / (1/4 (π · Ds ² )) × 10 ⁶ > 0 (1)
The relationship between the rising speed D, the outer diameter Ds of the cylindrical substrate, and the amount of coating liquid supplied to the container that holds the coating solution during ascent is V. After the substrate leaves the liquid surface, it is detached from the coating solution container. In order to shorten productivity and increase productivity,
V / (1/4 (π · Ds ² )) × 10 ⁶ > 0.8D
And more preferably
V / (1/4 (π · Ds ² )) × 10 ⁶ > 0.9D
And particularly preferably,
V / (1/4 (π · Ds ² )) × 10 ⁶ > 0.95D
It is.

In the case of producing a laminated electrophotographic photosensitive member, the above-described dip coating is performed for each of coating of a coating solution for a charge generation layer and coating of a coating solution for a charge transport layer.
In the process from the dip coating to the holding table, the cylindrical substrate is held and moved using, for example, a chuck device as shown in FIG. The illustrated chuck device (2) includes a horizontal arm (20) configured to be movable up and down and horizontally movable, and an insertion that is suspended vertically by the horizontal arm and inserted into a cylinder of the cylindrical base body (1). It consists of a shaft (21) and a balloon body (22) provided on the outer peripheral surface of the insertion shaft.

  The balloon body (22) can hold the cylindrical base body (1) if it is provided at least in one place with respect to the insertion shaft (21), but holds the cylindrical base body (1) vertically and more stably. Therefore, it is preferably provided at two positions with respect to the insertion shaft (21). These balloon bodies (22) are expanded by a fluid such as pressurized air supplied through a flow path formed inside the insertion shaft (21), so that the cylindrical base body (1) is removed from the cylinder. Hold. And the cylindrical base | substrate (1) hold | maintained with the balloon body (22) is moved up / down or moved horizontally by the action | operation of a horizontal arm (20). As the chuck device (2), in addition to a so-called air picker type device as shown in FIG. 2, a structure in which fingers that can be expanded and contracted are provided around an insertion shaft inserted into a cylinder of a cylindrical base. The apparatus of various structures, such as, can be employ | adopted.

After the above processing, although not shown, the cylindrical substrate (1) held by the chuck device (2) is transferred to the pallet of the transfer line and sent to the drying process, and the outer peripheral surface of the cylindrical substrate (1) is transferred. It is made to dry and a photosensitive coating film is formed in the said outer peripheral surface. The drying method is performed by a conventionally known temperature rising drying method or natural drying method. The temperature rising drying method is a drying method in which an air convection drying device (hot air drying device) is used and the temperature of the cylindrical substrate (1) is raised to a predetermined temperature to dry the coating liquid. In the temperature rising drying method, the temperature rising rate and the like are controlled in order to prevent so-called bubble defects. The natural drying method is a method in which the cylindrical substrate (1) is stationary in a space sealed with a cover and naturally dried. In the natural drying method, the concentration of the solvent vapor in the shield space is controlled in order to adjust the drying speed and prevent the occurrence of thickness unevenness.
<Substrate>
The substrate to be coated in the coating method of the present invention is not particularly limited as long as it is a cylindrical substrate or a cylindrical substrate that is not applied to the inner surface, but aluminum, nickel, brass, stainless steel, etc. These metal materials, laminates of these metal foils, or vapor-deposited materials of these metals.

  Also, a polymer material such as polyethylene terephthalate, polypropylene, nylon, polystyrene, phenol resin, etc. with a conductive layer made of aluminum, copper, palladium, tin oxide, indium oxide, etc. on the surface, carbon black on the polymer material, etc. Conductive substances such as metal powders, carbon black, copper iodide, polymer electrolytes, etc. formed by mixing conductive materials such as And a plastic drum subjected to a conductive treatment with a conductive metal oxide such as tin oxide or indium oxide.

The coating method of the present invention is suitably used for coating on a substrate for an electrophotographic photosensitive member that requires particularly uniform coating. As the substrate for the electrophotographic photosensitive member, any of the above-mentioned types can be used. Among them, a metal endless pipe such as aluminum is a preferable support. In particular, a base made of aluminum or an aluminum alloy is preferably used. As the aluminum material used for the substrate, aluminum alloys such as 3000 series, 5000 series, 6000 series, etc. specified by JIS are suitable. Extruded pipes, drawn pipes of those materials or those obtained by cutting them. Is used. A metal endless pipe such as aluminum is formed by processing such as extrusion, drawing, and ironing. What was shape | molded may be used as it is, and what added processes, such as cutting, grinding, and grinding | polishing further, may be used. The surface of the conductive support can be subjected to various treatments such as oxidation treatment and chemical treatment within a range that does not affect the image quality. Usually, a cylindrical substrate having an outer diameter of 1 to 20 cm and a length of 20 to 100 cm is used.
<Coating solution>
As a solution suitable for coating by the coating method of the present invention, any solution can be used as long as it can form a coating film by coating. A solution for coating and forming a photosensitive layer of an electrophotographic photoreceptor that requires precise control of the thickness of the film is suitable. By applying the solution for coating and forming the photosensitive layer of the electrophotographic photoreceptor by the coating method of the present invention, a highly uniform photosensitive layer can be coated and formed with a desired thickness with high accuracy.

  In the coating method of the present invention, any layer such as an intermediate layer, an undercoat layer, a photosensitive layer containing a photoconductive substance and / or a surface protective layer, which is usually possessed by an electrophotographic photoreceptor, is formed on the substrate. can do. Among these layers, an undercoat layer that usually forms a thin film layer of 3 μm or less, or a photosensitive layer having a laminated structure in which a charge generation layer containing a charge generation material and a charge transport layer containing a charge transport material are laminated ( Hereinafter, it may be suitably used for forming a charge generation layer). Among these, in particular, it can be suitably used for coating formation of the charge generation layer.

<Coating solution>
The coating liquid in the production method of the present invention is a conductive material such as a charge generation material or a charge transport material, a binder resin, a conductive inorganic compound such as a metal oxide or a metal compound, and / or a conventionally known method. Various additives such as an antioxidant can be obtained by dissolving or dispersing in an organic solvent.

<Charge generating material>
Examples of charge generation materials include selenium and its alloys, inorganic photoconductive materials such as amorphous silicon, azo pigments such as Sudan Red, Diane Blue, and Dienas Green B, quinone pigments such as disazo pigments, algor yellow, and pyrenequinone, and quinocyanine Examples thereof include pigments, perylene pigments, indigo pigments, bisbenzimidazole pigments such as Indian First Orange toner, phthalocyanine pigments such as copper phthalocyanine, anthanthrone pigments, quinacridone pigments, pyrylium salts, and azurenium salts.

  Among these, it is desirable to use organic pigments, particularly phthalocyanine pigments and azo pigments. When using phthalocyanine pigments, specifically, metal-free phthalocyanine, copper, indium, gallium, tin, titanium, zinc, vanadium, silicon, germanium and other metals or oxides thereof, halides, hydroxides, alkoxides, etc. Coordinated phthalocyanines having crystal forms are used. More specifically, the azo pigments described in JP-A-63-259572, JP-A-57-195567, JP-A-5-32905, JP-A-5-98181, and JP-A-2-8256. Preferred examples are phthalocyanine pigments described in JP-A-62-267094.

When a phthalocyanine compound is used as the charge generation material, specifically, a metal such as metal-free phthalocyanine, copper, indium, gallium, tin, titanium, zinc, vanadium, silicon, germanium, or an oxide or halide thereof. Phthalocyanines are used. Examples of the ligand to a metal atom having 3 or more valences include a hydroxyl group and an alkoxy group in addition to the oxygen atom and chlorine atom shown above. Particularly preferred are X-type, τ-type metal-free phthalocyanine, A-type, B-type, and D-type titanyl phthalocyanine, vanadyl phthalocyanine, chloroindium phthalocyanine, chlorogallium phthalocyanine, hydroxygallium phthalocyanine, and the like. Of the crystal forms of titanyl phthalocyanine mentioned here, A type and B type are described in W.W. It has been shown by Heller et al. As phase I and phase II, respectively (Zeit. Kristallogr. 159 (1982) 173), and type A is known as a stable type. The D-type is a crystal type characterized by a clear peak at a diffraction angle 2θ ± 0.2 ° of 27.3 ° in powder X-ray diffraction using CuKα rays. As the phthalocyanine compound, only a single compound may be used, or several mixed states may be used. As the mixed state that can be placed in the phthalocyanine compound or crystal state here, the respective constituent elements may be mixed and used later, or the mixed state in the production / treatment process of the phthalocyanine compound such as synthesis, pigmentation, crystallization, etc. It may be generated. As such treatment, acid paste treatment, grinding treatment, solvent treatment and the like are known.

<Charge transport material>
Charge transport materials include polyaromatic compounds such as anthracene, pyrene, phenanthrene, coronene or indole, carbazole, oxazole, isoxazole, thiazole, imidazole, pyrazole, oxadiazole, pyrazoline, thiadiazole, triazole in the main chain or side chain Compounds having a skeleton of nitrogen-containing cyclic compounds such as, aromatic nitro compounds such as 2,4,7-trinitrofluorenone, cyano compounds such as tetracyanoquinodimethane, and electron-withdrawing substances such as quinones such as diphenoquinone , Carbazole derivatives, indole derivatives, imidazole derivatives, oxazole derivatives, pyrazole derivatives, thiadiazole derivatives and other heterocyclic compounds, aniline derivatives, hydrazone compounds, aromatic amine derivatives, stilbene derivatives, Those diene derivatives and these compounds are more bond or polymers other having a group consisting of these compounds in the main chain or side chain, include hole transport materials such as hydrazone compounds.

<Binder resin>
Examples of the binder resin for forming the photosensitive coating film include polycarbonate, polyarylate, styrene-methyl methacrylate copolymer, polyester, styrene-acrylonitrile copolymer, polysulfone, polyacrylonitrile, polyvinyl butyral, polyvinyl propional, polyvinyl acetate, polyvinyl acetate. Acetoacetal, polyvinylpyrrolidone, methylcellulose, hydroxymethylcellulose, polyamide, phenoxy resin, epoxy resin, urethane resin, silicon resin, cellulose ester, cellulose ether, and styrene, vinyl acetate, vinyl chloride, acrylate ester, methacrylate ester, vinyl Examples thereof include polymers and copolymers of vinyl compounds such as alcohol and ethyl vinyl ether. Among these resins, a plurality of resins may be used in combination.

<Solvent>
As the solvent or dispersion medium, a solvent having high volatility and a vapor density higher than that of air is preferably used. For example, n-butylamine, diethylamine, ethylenediamine, isopropanolamine, triethanolamine, triethylenediamine, N , N-dimethylformamide, acetone, methyl ethyl ketone, cyclohexanone, benzene, 4-methoxy-4-methylpentanone-2, dimethoxymethane, dimethoxyethane, 2,4-pentadione, anisole, methyl 3-oxobutanoate, monochlorobenzene, toluene , Xylene, chloroform, 1,2-dichloroethane, 1,2-dichloropropane, 1,1,2-trichloroethane, 1,1,1-trichloroethane, trichloroethylene, tetrachloroethane, dichlorometa , Tetrahydrofuran, dioxane, methyl alcohol, ethyl alcohol, isopropyl alcohol, ethyl acetate, butyl acetate, dimethyl sulfoxide, methyl cellosolve, ethyl cellosolve, and the like methyl cellosolve acetate. These solvents may be used alone or in combination of two or more.

<Physical properties of coating solution>
The density | concentration of each component in a coating liquid and the viscosity of a coating liquid are suitably selected according to a well-known method.
For example, in the case of a charge transport layer of a single layer type photoreceptor or a function separation type photoreceptor, the solid content concentration of the coating solution is usually 5% by weight or more, preferably 10% by weight or more, more preferably 20% by weight or more. In general, it is used in the range of 50% by weight or less, preferably 40% by weight or less, particularly preferably 35% by weight or less. The viscosity of the coating solution is usually 10 cps or more, preferably 50 cps or more, and usually 500 cps or less, preferably 400 cps or less. The film thickness of the coating film is preferably 15 to 40 μm.

  In the case of a charge generating layer of a multilayer photoreceptor, the solid content concentration of the coating solution is usually 0.1% by weight or more, preferably 1% by weight or more, and usually 15% by weight or less, preferably 10% by weight. % Or less is used. The viscosity of the coating solution is usually in the range of 0.01 cps or more, preferably 0.1 cps or more, and usually 20 cps or less, preferably 10 cps or less.

Hereinafter, the present invention will be described in more detail with reference to production examples, examples and comparative examples. The following examples are given for the purpose of illustrating the present invention in detail, and the present invention is not limited to the production examples and examples shown below, unless they are contrary to the spirit of the invention.
Example 1

<Manufacture of aluminum substrate>
An aluminum alloy No. 6063 defined by JIS was processed into a cylindrical shape by extrusion, then drawn and further cut to obtain an aluminum substrate having an outer diameter of 60 mm and a length of 300 mm.
<Manufacture of coating liquid>
A-type oxytitanium phthalocyanine having strong diffraction peaks at 9.3 °, 10.6 ° and 26.3 ° in the powder X-ray diffraction spectrum for CuKα characteristic X-rays 10 parts by weight was added to 150 parts by weight of 4-methoxy-4-methylpentanone-2 and pulverized with a sand grind mill for 1 hour for atomization.

As binder resin, 5% of polyvinyl butyral (Electrochemical Industry Co., Ltd., trade name Denkabutyral # 6000C) 5% 1,2-dimethoxyethane solution and phenoxy resin (Union Carbide, trade name PKHH) A binder resin solution was prepared by mixing 100 parts of a 1,2-dimethoxyethane solution.
100 parts by weight of the binder resin solution and an appropriate amount of 1,2-dimethoxyethane were added to 160 parts by weight of the previously prepared pigment dispersion to finally prepare a pigment dispersion having a solid content concentration of 4.0%.

<Application process>
The aluminum substrate is gripped from the inner surface by a balloon chuck inserted from the upper end, and is approximately perpendicular to the coating liquid tank filled with the pigment dispersion up to the upper end of a cylindrical container having a diameter of 80 mm and a depth of 500 mm. Immersion coating was performed at a relative rising speed of 300 mm / min with respect to the liquid surface and a liquid supply speed of 0.80 L / min during the ascending of the substrate. When this application condition is applied to equation (2) and calculated, D = 300, V = 0.8, and Ds = 60.
V / (1/4 (π · Ds ² )) × 10 ⁶ = 283
D = 300
0.8D = 240
Thus, the condition represented by the formula (2) of the present invention is satisfied.

Example 2
Immersion coating was performed in the same manner as in Example 1 except that the liquid supply rate during ascending the substrate was 0.70 L / min. When this application condition is applied to the equation (1) and calculated, D = 300, V = 0.7, and Ds = 60.
V / (1/4 (π · Ds ² )) × 10 ⁶ = 212
Thus, the condition represented by the formula (1) of the present invention is satisfied.

Comparative Example 1
Immersion coating was carried out in the same manner as in Example 1 except that the liquid supply rate during ascending the substrate was 1.0 L / min. When this application condition is applied to equation (1) and calculated, D = 300, V = 1.0, and Ds = 60.
V / (1/4 (π · Ds ² )) × 10 ⁶ = 353
Thus, the value of V / (1/4 (π · Ds ² )) × 10 ⁶ exceeds the value of D (= 300) and is not a coating method of the present invention.

Comparative Example 2
Immersion coating was performed in the same manner as in Example 1 except that the coating solution was not supplied to the coating solution tank while the substrate was raised. When this application condition is applied to the equation (1) and calculated, D = 300, V = 0, Ds = 60.
V / (1/4 (π · Ds ² )) × 10 ⁶ = 0
Thus, the value of V / (1/4 (π · Ds ² )) × 10 ⁶ is not the coating method of the present invention.
[Evaluation]
The appearance of the coating film formed on the substrate is evaluated visually, and the time from when the aluminum substrate contacts the coating solution until it exits the coating tank (hereinafter sometimes referred to as coating time) is measured with a stopwatch. did. The results are shown in Table-1.

It is explanatory drawing which shows an example of the immersion apparatus for implementing a dip coating method. It is explanatory drawing which shows an example of the chuck apparatus holding a cylindrical base | substrate.

Explanation of symbols

1: Cylindrical substrate 2: Chuck device 3: Immersion coating device

Claims (3)

After immersing a columnar or cylindrical substrate to be coated in a coating solution so that its virtual axis is substantially perpendicular to the liquid surface, the substrate is relative to the liquid surface of the solution. In the coating method, the rising speed D with respect to the liquid level of the substrate (mm / min), the outer diameter Ds (mm) of the substrate, and the coating solution for supplying the coating solution while the substrate is rising A dip coating method, wherein the relationship represented by the following formula (1) is established when the solution supply rate is V (L / min).
D> V / (1/4 (π · Ds ² )) × 10 ⁶ > 0 (1) The dip coating method according to claim 1, wherein the following formula (2) is satisfied.
D> V / (1/4 (π · Ds ² )) × 10 ⁶ > 0.8D (2) A method for producing an electrophotographic photosensitive member, wherein a photosensitive layer is formed by coating by the coating method according to claim 1.

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