JP4233474B2 - Immersion coating apparatus and method for producing electrophotographic photosensitive member using the apparatus - 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 uniformly and uniformly to a columnar or cylindrical substrate surface.

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. By simply moving the container containing the coating solution and the substrate to be coated so that the substrate is immersed in the coating solution, the substrate can be easily applied to the surface. Usually, a method in which the pulled-up photosensitive substrate is then allowed to stand still and naturally dried is employed.
An electrophotographic photosensitive member is manufactured by applying a photosensitive material to a peripheral surface of a cylindrical or columnar photosensitive substrate to form a photosensitive layer. As a method for applying the photosensitive material, a dip coating method is used. Usually used. In order to form a coating film having a uniform thickness with very high accuracy, such as a photosensitive layer of an electrophotographic photoreceptor, a fast-drying solvent is usually used as a solvent for the coating solution. When a fast-drying solvent is used, the coating solution can be solidified in a short time by increasing the drying rate of the coating solution. However, the surface property of the formed coating film is deteriorated due to the following reasons. There is.

  That is, the flow of the solvent vapor generated by the surrounding extremely low-speed air flow gives thickness unevenness to the formed coating film. In particular, such a phenomenon occurs remarkably in an industrial scale implementation in which a large number of substrates are suspended. That is, the influence of the solvent vapor generated from the coating liquid applied to the adjacent substrate is large, and accordingly, the photosensitive substrate positioned at the end and the photosensitive substrate positioned around the other photosensitive substrate In this case, since the influence of the solvent vapor received is different, the thickness unevenness of the photosensitive coating film is likely to occur. Further, since the drying speed is too high, brushing (a phenomenon in which water vapor is condensed on the coating film from which latent heat has been removed by rapid evaporation of the solvent and the photosensitive coating film becomes cloudy) occurs.

  In order to solve the above problem, a method is adopted in which the substrate after application is stationary in a space covered with a hood and naturally dried. In such a method, when the solvent vapor is excessively accumulated in the shield space, the drying speed is slowed to cause liquid dripping and the thickness unevenness in the vertical direction of the photosensitive substrate is generated. The concentration of solvent vapor is controlled.

In order to control the concentration of solvent vapor in the shield space, a method using a vertically-structured cover having a large number of openable and closable openings (see, for example, Patent Document 1), a cylindrical hood having openings at the top and bottom Techniques relating to the shape of the hood, such as a method to use (see, for example, Patent Document 2) and a method to use a cylindrical hood in which an opening is provided around the lower end (see, for example, Patent Document 3) are disclosed. In addition, a method for setting the concentration of solvent vapor as a function of the height from the lower end of the drying region (see, for example, Patent Document 4) is proposed, and furthermore, a cylindrical hood provided with an opening around the lower end is provided. As a method to be used, a method (for example, see Patent Document 5) in which the pulling speed of the photosensitive substrate is defined has been proposed in order to improve productivity.
Japanese Patent Publication No. 63-11940 Japanese Patent Laid-Open No. 3-27469 JP 59-42060 A JP-A-60-110378 Japanese Patent Publication No. 4-80383

However, the shape of the substrate when forming a coating film on the surface of the substrate by dip coating may be various, particularly when producing an electrophotographic photoreceptor, the type of solvent, the solid content concentration of the coating solution, The length and diameter of the photosensitive substrate, the coating thickness, etc. may be changed. Therefore, each of the above methods for controlling the concentration of the solvent vapor by utilizing the diameter and number of the openings provided in the cover, the upper and lower gaps, etc. Then, these have to be determined for every manufacturing condition, and there exists a fault which requires a great effort.

  The present invention has been made in view of the above circumstances, and its purpose is that it is possible to control the concentration of solvent vapor with respect to changes in production conditions by an easy operation. An object of the present invention is to provide a dip coating apparatus capable of forming an excellent coating film with little sagging and without causing coating film defects such as brushing.

As a result of intensive studies on the above problems, the present inventors have used a first hood that does not have an opening on the side surface and a second hood that has an opening on the side surface. It has been found that coating film defects such as sagging and brushing of the film can be prevented, and the present invention has been achieved.
That is, according to the present invention, the container containing the coating liquid and the substrate to be coated are moved relative to each other, the substrate is dipped in the coating liquid and then pulled up, and then the substrate is stationary in a hood and applied to the surface of the substrate. In the dip coating apparatus for forming a film, the hood has a first hood that covers all side surfaces in the circumferential direction, and at least one opening on the side surface. A second hood whose opening is not symmetrical with respect to the virtual central axis of the hood is provided , and the first hood is movable up and down, and relative to the relative movement of the substrate to be coated. It moves at an arbitrary timing, or the first hood is installed so as to be stretchable and the height changes at an arbitrary timing with respect to the relative movement of the substrate to be coated. Dip applicator, and It consists in the method for producing a photoreceptor, characterized by using the device.

  According to the dip coating apparatus according to the present invention, it is possible to form a coating film with excellent surface characteristics that is uniform and has no coating unevenness, does not cause brushing, and has no coating sagging at the upper end. By forming the photosensitive layer using the dip coating apparatus, an extremely high quality electrophotographic photoreceptor can be easily produced.

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 and implemented 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 device (3) is mainly composed of an immersion tank (30) in which the coating liquid is stored and the substrate (1) is immersed, and a coating liquid circulation mechanism. The immersion tank may be a combination of a plurality of tanks. 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) schematically shows the hood of the present invention provided on the immersion tank (30) and the receiving toy (32) of the present invention. Details will be described later in the section of <Food>. To describe.

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 The cylindrical substrate (1) is raised substantially vertically relative to the immersion bath (30).
In the dip coating process, the 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 shaft (21) suspended vertically on the horizontal arm and inserted into the base (1). ) And a balloon body (22) provided on the outer peripheral surface of the insertion shaft.

  The balloon body (22) can hold the base body (1) if it is provided at least at one location with respect to the insertion shaft (21). However, in order to hold the base body (1) vertically and more stably, It is provided at two places with respect to the insertion shaft (21). These balloon bodies (22) hold the substrate (1) from the inside by being expanded by a fluid such as pressurized air supplied through a flow path formed inside the insertion shaft (21). 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, various types such as a structure in which fingers that can be expanded and contracted around an insertion shaft inserted into the base are provided. It is possible to employ an apparatus having the structure described below.

  After the above process, although not shown, the 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 substrate (1) is dried to A coating film is formed on the 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 that uses an air convection drying device (hot air drying device) to raise the temperature of the substrate (1) to a predetermined temperature and 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 substrate (1) is statically dried in a space sealed with a hood. 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.

<Food>
In the present invention, a hood specific to the present invention is provided on the immersion tank (30) and the receiving toy (32). The hood includes a second hood (hereinafter sometimes referred to as an open hood) having at least one opening on a side surface, and a first hood (hereinafter referred to as a non-opening) that does not have an opening that covers all sides in the circumferential direction. These hoods may be provided separately or integrally, and if they are provided as a single piece, the hood and the non-open hood created separately A combination of the open hoods may be used, or an open hood and a non-open hood may be integrally formed.

  The top and bottom surfaces of the hood may have any shape as long as they do not interfere with the substrate to be coated. However, it is preferable that the top surface also has a hood in order to prevent airflow from the top surface. The top hood may be integrated with the open hood and / or the non-open hood or may be a separate body, but is provided on the chuck device (2) so as not to interfere with the movement of the substrate to be coated. It is preferred that

  The hood of the present invention may be fixedly installed with respect to the immersion tank (30) or may be installed so as to be relatively movable, but the substrate is relatively relative to the immersion tank (30). It is preferable to be able to move at an appropriate arbitrary timing in accordance with the vertical movement because it is possible to control the solvent vapor concentration of various different coating solutions. In particular, the non-opening hood is preferably movable at any suitable timing. When the open hood and the non-open hood are provided integrally, each hood moves as a unit, but when the open hood and the non-open hood are provided separately, the respective hoods are interlocked. However, they may be operated individually. When the opening hood and the non-opening hood are provided separately, it is preferable to operate individually.

  The non-opening hood has a function of storing a certain amount of solvent vapor used in the coating solution around the object to be coated. Although the non-opening hood does not have an opening on the side surface, if the opening is provided at the lower part of the hood, the solvent vapor flows out from the opening and is lost. Or it installs so that a clearance gap may become as small as possible with respect to a receiving toy (32). Since the overflowed coating liquid flows in the outer edge portion of the immersion bath (30), it is difficult to bring the lower portion of the hood close to the outer edge portion. Provide a small gap for outflow. Preferably, the lower portion of the non-opening hood is provided in contact with the outer edge portion of the toy, and more preferably, the lower portion of the non-opening hood is joined to the outer edge portion of the toy.

  The opening hood has an opening that prevents excessive solvent vapor from accumulating and prevents airflow from flowing in the horizontal direction. In order to prevent the airflow from flowing in the horizontal direction, the opening is usually provided at one location on the side of the hood, but if it is not symmetrical with respect to the virtual center axis of the hood, there are multiple openings. I do not care. Here, the virtual center axis indicates the virtual center axis of the cylinder when the hood has a cylindrical shape. When the hood outer shape is a polygonal column shape, the virtual center axis is the smallest circle that includes the polygon of the horizontal section of the hood. A vertical line passing through the center.

The opening is usually formed by a portion on the side surface sandwiched by two vertical lines parallel to the virtual central axis, but is not limited to such an opening, and has a large number of holes on the side surface It does not matter. However, the openings should not be formed at positions symmetrical to each other with respect to the virtual center axis.
The area of the opening portion needs to be wide enough so that the solvent vapor can sufficiently flow out so that excessive solvent vapor does not accumulate, but is usually 10% or more with respect to the total area of the hood. , Preferably 15% or more, more preferably 20% or more. In addition, if the area of the opening is too large, it is easy to flow in the horizontal direction and leads to unevenness of the coating film. Therefore, it is usually 80% or less, preferably 60% or less with respect to the entire area of the hood. More preferably, it is 40% or less.
The heights of the open hood and the non-open hood are arbitrary, but those that can be expanded and contracted as required are preferable.

<Substrate>
The substrate to be coated in the coating method of the present invention is not particularly limited as long as it is a columnar substrate or a cylindrical substrate, but there are no particular restrictions on the material or shape, but a metal material such as aluminum, nickel, brass, stainless steel, or Polymer foils such as polyethylene terephthalate, polypropylene, nylon, polystyrene, phenol resin, etc., which are provided with a conductive layer such as aluminum, copper, palladium, tin oxide, indium oxide on the surface, such as laminates, vapor deposits, and metal foils. Conductive materials such as metal powder, carbon black, copper iodide, and polymer electrolyte are formed by mixing carbon black with these polymers to make them conductive, or molding other materials such as hard paper into a cylindrical shape. Conductive material applied with a suitable binder and conductive treatment, or tin oxide, oxidation And plastic drums conductively treated with a conductive metal oxide such as indium and the like.

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. stipulated 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, the cylindrical base has an outer diameter of 2 to 20 cm and a length of 21 to 100 cm.

<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, a photosensitive layer having a laminated structure in which an intermediate layer or a charge generating layer containing a charge generating substance and a charge transporting layer containing a charge transporting substance are laminated (usually a layer having a thickness of 10 μm or more). For example, it may be referred to as a type photosensitive 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 antioxidants can be obtained by dissolving or dispersing in an organic solvent.

<Photosensitive layer>
The production method of the present invention is the same as the production method of an electrophotographic photoreceptor by a conventional dip coating method, except for the point relating to the hood described above.
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. be able to. Among these layers, a photosensitive layer having a laminated structure in which a charge generating layer containing an intermediate layer or a charge generating substance and a charge transporting layer containing a charge transporting substance are usually formed to form a thick film layer (hereinafter referred to as a laminated type). (It may be referred to as a photosensitive layer). Among these, in particular, it can be suitably used for coating formation of a charge transport layer, and gives an excellent electrophotographic photoreceptor.

<Coating solution>
In the production method of the present invention, the photosensitive material coating solution is a mixture of a charge generating material, a charge transporting material, a binder resin, and a coating solvent when a single layer type electrophotographic photosensitive member is produced. The photosensitive material coating solution used in the production of the laminated electrophotographic photosensitive member includes a charge generating layer, a binder resin and a coating solvent for a charge generating layer, a charge transport material, a binder resin, A charge transport layer coating solution composed of a coating solvent is separately mixed.

<Charge generating material>
Examples of charge generating materials include azo pigments such as Sudan Red, Diane Blue, and Dienas Green B; quinone pigments such as disazo pigments, algor yellow, and pyrenequinone; quinocyanine pigments, perylene pigments, indigo pigments, and bis such as Indian First Orange toner. Examples thereof include benzimidazole pigments, phthalocyanine pigments such as copper phthalocyanine, quinacridone pigments, pyrylium salts, and azulenium salts.

<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 Examples thereof include compounds having a skeleton of a nitrogen-containing cyclic compound such as, and hole transport materials such as hydrazone compounds.

<Binder resin>
Examples of the binder resin for forming the photosensitive coating film include polycarbonate, polyarylate, polystyrene, polymethacrylic acid esters, styrene-methyl methacrylate copolymer, polyester, styrene-acrylonitrile copolymer, polysulfone, etc., polyvinyl acetate, polyacrylonitrile. , Polyvinyl butyral, polyvinyl pyrrolidone, methyl cellulose, hydroxymethyl cellulose, cellulose esters and the like.

<Solvent>
As the solvent, a solvent having high volatility and a vapor density larger than that of air is preferably used. For example, n-butylamine, diethylamine, ethylenediamine, isopropanolamine, triethanolamine, 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, dichloromethane, tetrahydrofuran, dioxane, methanol, ethanol, isopropanol, ethyl acetate, butyl acetate, dimethyl sulfoxide, methyl cellosolve, ethyl cellosolve, Roussel cellosolve acetate and the like.

<Physical properties of coating solution>
The concentration of each component in the coating solution is appropriately selected according to a known method. The concentration of the solid content is mainly determined according to the film thickness of the layer to be formed. In the case of a coating solution for producing a single-layer type electrophotographic photosensitive member, a laminated type electrophotographic photosensitive member is produced. In the case of the coating solution for the charge transport layer, the amount is adjusted to 40% by weight or less, preferably 10 to 35% by weight or less. In the case of these coating solutions, the viscosity is 50 to 300 cps, preferably 70 to 250 cps, and the dry film thickness is 15 to 40 μm.

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>
・ Coating liquid for charge generation layer formation In powder X-ray diffraction spectrum for CuKα characteristic X-ray, Bragg angles (2θ ± 0.2 °) are strong diffraction peaks at 9.3 °, 10.6 ° and 26.3 ° A type oxytitanium phthalocyanine having 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 treatment.

As binder resin, polyvinyl butyral (manufactured by Denki Kagaku Kogyo Co., Ltd., trade name: Denkabutyral # 6000C) 5% 1,2-dimethoxyethane solution 100 parts and phenoxy resin (trade name: PKHH) A binder resin solution was prepared by mixing 100 parts of a 5% 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%. -Charge transport layer forming coating solution 56 parts by weight of the following hydrazone compound A,

  14 parts by weight of hydrazone compound B shown below,

  And 1.5 parts by weight of the following cyanide compound

  And 100 parts by weight of the following polycarbonate resin (monomer molar ratio 1: 1)

Was dissolved in a mixed solvent of 1,4 dioxane: tetrahydrofuran = 65: 25 to prepare a charge transport layer coating solution.
<Application process>
The aluminum substrate is gripped from the inner surface by a balloon chuck inserted from the upper end, and filled with the coating solution up to the upper end of the container, above the cylindrical coating tank having a diameter of 80 mm and a depth of 500 mm. The charge generation layer and the charge transport layer are arranged in this order in a thickness of 0.5 μm by immersing and applying substantially vertically in an immersion tank provided with a hood as shown in the schematic diagram, and drying. The charge transport layer was applied and formed so as to have a thickness of 20 μm to produce a laminated photosensitive layer.

Comparative Example 1
Dip coating was performed in the same manner as in Example 1 except that a dip coating apparatus having only a hood having no opening as shown in the schematic diagram of FIG.
Comparative Example 2
Immersion coating was performed in the same manner as in Example 1 except that a dip coating apparatus in which only a hood having an opening as shown in the schematic diagram of FIG.
[Evaluation]
The appearance of the coating film formed on the substrate is visually evaluated, and the number of defective coating films when 20 dip coatings are performed is shown in Table-1.

  As is apparent from the results in Table 1, when applied by the dip coating apparatus having the hood of the present invention, the coating film has excellent surface characteristics, and forms a coating film with extremely high uniformity and high quality. be able to.

It is a schematic diagram of the whole coating device of the present invention. It is a schematic diagram of a substrate holding robot in the coating apparatus of the present invention. It is a schematic diagram of the food | hood of this invention. It is a schematic diagram which shows the food | hood used for the comparative example. It is a schematic diagram which shows the food | hood used for the comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cylindrical base | substrate 2 Chuck apparatus 3 Immersion coating apparatus 4 Opening hood 5 Non-opening hood

Claims (4)

The container containing the coating solution and the substrate to be coated are moved relative to each other, the substrate is dipped in the coating solution, then lifted, and then the substrate is placed in a hood to form a coating film on the surface of the substrate. In the coating apparatus, the hood has a first hood covering all side surfaces in the circumferential direction, and at least one opening portion on the side surface, and when there are a plurality of the opening portions, the opening portion is the hood. A second hood that is not symmetrical with respect to the virtual center axis of the first hood is provided , and the first hood can be moved up and down at any timing relative to the relative movement of the substrate to be coated. A dip coating apparatus characterized by: The container containing the coating solution and the substrate to be coated are moved relative to each other, the substrate is dipped in the coating solution, then lifted, and then the substrate is placed in a hood to form a coating film on the surface of the substrate. In the coating apparatus, the hood has a first hood covering all side surfaces in the circumferential direction, and at least one opening portion on the side surface, and when there are a plurality of the opening portions, the opening portion is the hood. A second hood that is not symmetrically positioned with respect to the virtual central axis of the first hood is provided so that the first hood can be extended and contracted. Immersion coating apparatus characterized in that height changes with timing . A method for producing an electrophotographic photosensitive member, wherein the dip coating apparatus according to claim 1 is used. The method for producing an electrophotographic photosensitive member according to claim 3 , wherein the coating liquid contains a charge transport material.

Images