JP7639443B2 - Coating device and coating method - Google Patents

Description

The present invention relates to a coating device and a coating method.

The following Patent Document 1 discloses a coating device used when coating a cylindrical substrate with a coating liquid. The coating device described in this document includes a coating tank filled with the coating liquid, and a cylindrical section that is provided above the coating layer and through which the coating liquid overflows. The coating device also includes a solvent evaporation suppressing member (evaporation suppressing member) having a solvent evaporation suppressing cylindrical section that covers the cylindrical section from its outer periphery, and a lid having a hood provided above the cylindrical section and the solvent evaporation suppressing member. The substrate is inserted into the cylindrical section and then pulled up from the cylindrical section, so that the coating liquid is applied to the outer periphery of the substrate.

Patent No. 5194558

In coating devices, there is concern that unevenness in the coating on the surface of the substrate may occur due to the influence of solvent vapor evaporating from the coating liquid applied to the surface of the substrate.

In consideration of the above, the present invention aims to provide a coating device and coating method that can prevent uneven coating of the substrate surface compared to a configuration that only has an evaporation suppression member that suppresses evaporation of the coating liquid from the cylindrical portion.

The coating device of the first aspect is equipped with a coating tank having a cylindrical portion that is filled with a coating liquid and from which the coating liquid overflows from the top, in which a substrate is immersed in the cylindrical portion from above, an evaporation suppressing member having a cylindrical covering cylindrical portion that surrounds the cylindrical portion from the radial outside and suppresses evaporation of the coating liquid, a hood member that is provided above the coating tank and covers the coating tank from above and has a cylindrical hood portion that covers the substrate from the radial outside, and a gas exhaust portion that exhausts solvent vapor that evaporates from the coating liquid that has adhered to the surface of the substrate located within the hood portion.

The second aspect of the coating device is the coating device of the first aspect, in which the hood member includes a fixed hood having the hood portion and immovably disposed relative to the coating tank, and a movable hood having the hood portion and movable in the vertical direction relative to the fixed hood, and when the substrate is lifted from the coating tank, the movable hood rises relative to the fixed hood.

The coating device of the third aspect is the coating device of the first or second aspect, and further includes a flow divider having an inflow section into which the coating liquid flows, a plurality of outflow sections through which the coating liquid flows out and which are connected to a plurality of the coating tanks, and a first opposing section and a second opposing section arranged opposite each other, and a slit flow path between the first opposing section and the second opposing section that connects the inflow section and the plurality of outflow sections.

The coating method of the fourth aspect uses the coating device of any one of the first to third aspects, and includes a first step of lowering the substrate to insert the substrate into the cylindrical portion, and a second step of raising the substrate to lift the substrate from the cylindrical portion, and in the second step, the gas exhaust section sucks in and exhausts the solvent vapor that evaporates from the coating liquid that adheres to the surface of the substrate located in the hood section.

A fifth aspect of the coating method is the coating method of the fourth aspect, wherein the amount of the gas containing the solvent vapor sucked and discharged from the hood portion is set to 0.1 to 0.6 m ³ /h.

The coating method of the sixth aspect is the coating method of the fourth or fifth aspect, in which in the second step, the lifting speed of the substrate in the latter part of the lifting process when the substrate is lifted from the cylindrical portion is made slower than the lifting speed of the substrate in the early part of the lifting process.

The seventh aspect of the coating method is the coating method of any one of the fourth to sixth aspects, in which the coating device of the second aspect is used, and in the second step, the movable hood is raised to lift the substrate while covering the portion of the substrate protruding from the hood portion of the fixed hood with the hood portion of the movable hood.

The coating method of the eighth aspect is the coating method of any one of the fourth to seventh aspects, in which the coating device of the third aspect is used, and in the first step, the multiple substrates are inserted into the multiple cylindrical portions, respectively, and in the second step, the multiple substrates are pulled up from the multiple cylindrical portions, respectively.

The coating device of the first aspect can prevent uneven coating on the surface of the substrate compared to a configuration in which only an evaporation suppression member is provided.

The second aspect of the coating device can prevent uneven coating on the surface of the substrate compared to a configuration in which the hood member is equipped only with a fixed hood.

The coating device of the third aspect can make the coating liquid more uniform compared to a configuration in which the flow path of the flow divider has a circular cross section.

The coating method of the fourth aspect can prevent uneven coating on the surface of the substrate compared to the method in which the substrate is simply lifted from the cylindrical portion in the second step.

According to the coating method of the fifth aspect, when the amount of suction gas is less than 0.1 m ³ /h, the occurrence of uneven coating on the surface of the substrate can be suppressed compared to when the amount is outside the numerical range exceeding 0.6 ^{m 3} /h.

The coating method of the sixth aspect can effectively prevent uneven coating compared to when the substrate is pulled up from the cylindrical portion at a constant speed.

The seventh aspect of the coating method can prevent uneven coating on the surface of the substrate compared to a configuration that uses only a fixed hood as the hood member.

The coating method of the eighth aspect makes it possible to achieve uniform coating quality on the surfaces of multiple substrates compared to using a flow divider with a circular cross-section.

FIG. 2 is a side cross-sectional view that illustrates a coating apparatus. 4 is a plan view showing a schematic diagram of piping paths for a coating liquid to be supplied to a plurality of cylindrical portions. FIG. FIG. 4 is a perspective view showing a first flow divider. FIG. 2 is a side cross-sectional view corresponding to FIG. 1 and showing a state before the substrate is inserted into the cylindrical portion. 2 is a side cross-sectional view corresponding to FIG. 1 and showing a state when the insertion of the base material into the cylindrical portion is completed. FIG. 2 is a side cross-sectional view corresponding to FIG. 1 and showing a state when the substrate has been completely pulled up from the cylindrical portion. FIG. 2 is a side cross-sectional view corresponding to FIG. 1 , showing a state in which the raised movable hood has returned to its original position. FIG. 11 is a side cross-sectional view showing another type of coating layer. FIG. 2 is a cross-sectional view showing a schematic diagram of each layer of a coating film applied to the surface of a substrate.

Below, a description will be given of a form for implementing the technology of this disclosure. In the following description, the direction indicated by the arrow X, which is appropriately shown in the drawings, will be referred to as the device width direction, and the direction indicated by the arrow Y will be referred to as the device height direction. In addition, the direction perpendicular to each of the device width direction and device height direction (arrow Z direction) will be referred to as the device depth direction.

As shown in FIG. 1, the coating device 10 of this embodiment is a device used to coat the outer peripheral surface of a cylindrical substrate 12 with a coating liquid 14. The coating device 10 includes a chuck portion 16 that grips the upper end portion 12A of the substrate 12, a coating tank 18 to which the coating liquid 14 is supplied, and a liquid receiving portion 20 that receives the coating liquid 14 that has overflowed from the coating tank 18. The coating device 10 also includes an evaporation suppressing member 22 that suppresses evaporation of the coating liquid 14, and a fixed hood 24 and a movable hood 26 as hood members that cover the coating tank 18 from above. The coating device 10 also includes a gas exhaust portion 28 that exhausts solvent vapor that evaporates from the coating liquid 14 that has adhered to the surface of the substrate 12 located within the fixed hood 24 and the movable hood 26.

The chuck portion 16 is configured to be able to grip the upper end portion 12A of the substrate 12 by, for example, operation of compressed air or an electric actuator. In this embodiment, 24 chuck portions 16 are arranged in four rows in the device width direction and six rows in the device depth direction. The spacing between adjacent chuck portions 16 in the device width direction and the spacing between adjacent chuck portions 16 in the device depth direction are set to the same spacing. The 24 chuck portions 16 are held by a chuck holding member 30. The number of chuck portions 16 may be set appropriately taking into account the number of substrates 12 to be processed simultaneously.

The coating tank 18 is filled with the coating liquid 14 by supplying the coating liquid 14 from below, and has a cylindrical portion 19 from which the coating liquid 14 overflows from the top. The inner diameter of the cylindrical portion 19 is set to be larger than the outer diameter of the substrate 12, and the depth of the cylindrical portion 19 is set to be deeper than the length of the substrate 12. This makes it possible to immerse the substrate in the cylindrical portion 19 from above. As shown in Figures 1 and 2, in this embodiment, 24 cylindrical portions 19 are arranged in four rows in the width direction of the device and six rows in the depth direction of the device. In addition, the interval between adjacent cylindrical portions 19 in the width direction of the device and the interval between adjacent cylindrical portions 19 in the depth direction of the device are set to the same interval. The number of cylindrical portions 19 may be set appropriately taking into account the number of substrates 12 to be processed simultaneously.

Here, in this embodiment, the coating liquid 14 is supplied to the 24 cylindrical portions 19 via six first flow dividers 32 and a single second flow divider 34 as flow dividers.

3, the first flow distributor 32 includes an outer wall portion 32A as a first opposing portion formed in a cylindrical shape, a first lower wall portion 32B connected to the lower end of the outer wall portion 32A and formed in a funnel shape narrowing toward the lower side, and a cylindrical inlet portion 32C connected to the lower end of the first lower wall portion 32B. The first flow distributor 32 also includes an inner wall portion 32D as a second opposing portion formed in a cylindrical shape and disposed inside the outer wall portion 32A and radially opposed to the outer wall portion 32A, a second lower wall portion 32E that closes the lower end of the inner wall portion 32D, and an upper wall portion 32F that closes the upper ends of the outer wall portion 32A and the inner wall portion 32D. Furthermore, the first flow distributor 32 includes four outlet portions 32G that are connected to the upper end side of the outer wall portion 32A and are arranged at equal intervals along the circumferential direction of the outer wall portion 32A. Here, the space between the first lower wall portion 32B and the second lower wall portion 32E inside the first flow distributor 32 is a conical flow path 32H that is a conical space. Also, the space between the outer wall portion 32A and the inner wall portion 32D inside the first flow distributor 32 is a slit flow path 32J that is a cylindrical space. The flow path width of this slit flow path 32J is set so that the liquid flow is laminar. This makes it possible to discharge the coating liquid 14 that has flowed from the inlet portion 32C into the conical flow path 32H from the four outlet portions 32G via the slit flow path 32J. The second flow distributor 34 shown in FIG. 2 is configured in the same manner as the first flow distributor 32, except that it has six outlet portions 32G and has dimensions according to the flow rate to be distributed to the six first flow distributors 32. The outlet portion 32G of the second flow distributor 34 is also given the same reference numeral as the outlet portion 32G of the first flow distributor 32.

As shown in FIG. 2, the outlets 32G of the first diverters 32 are connected to the four cylindrical sections 19 arranged side by side in the width direction and depth direction of the device. Also, the outlets 32G of the second diverters 34 are connected to the inlets 32C of the six first diverters 32 (see FIG. 3).

1, the liquid receiving section 20 includes a plate-shaped bottom surface section 20A that extends in the device width direction and device depth direction at the vertical intermediate portion of the cylindrical section 19, and a side surface section 20B that rises upward from the ends of the bottom surface section 20A in the device width direction and device depth direction. The bottom surface section 20A has a plurality of through holes 20C through which the plurality of cylindrical sections 19 are inserted, and a plurality of through holes 20D through which the plurality of suction tubes 40 described later are inserted. The gap between the outer peripheral surface of the cylindrical section 19 and the through hole 20C is blocked, and the gap between the outer peripheral surface of the suction tube 40 and the through hole 20D is blocked. The bottom surface section 20A is inclined downward as it approaches one side in the device width direction. The return pipe 36 is connected to the side surface section 20B on one side in the device width direction. The coating liquid 14 that overflows from the top end of the cylindrical portion 19 and reaches the bottom portion 20A flows along the bottom portion 20A toward one side in the device width direction and is collected from the return pipe 36 to a liquid holding tank (not shown). The coating liquid 14 collected from the return pipe 36 to the liquid holding tank is sent again toward each cylindrical portion 19 of the coating tank 18. That is, the coating liquid 14 circulates between the cylindrical portion 19 of the coating tank 18 and the liquid holding tank.

The evaporation suppression member 22 includes a plurality of covering cylindrical portions 22A formed in a cylindrical shape surrounding the plurality of cylindrical portions 19 from the radial outside, and a bottom surface portion 22B connecting the plurality of covering cylindrical portions 22A and extending in the device width direction and device depth direction. The bottom surface portion 22B covers the liquid receiving portion 20 from above. In addition, the bottom surface portion 22B is formed with a plurality of through holes 22C through which the plurality of suction tubes 40 described later are inserted. The gap between the outer circumferential surface of the suction tube 40 and the through hole 22C is blocked. The coating liquid 14 overflowing from the upper end of the cylindrical portion 19 flows through the gap between the covering cylindrical portion 22A and the cylindrical portion 19, so that the solvent vapor evaporated from the coating liquid 14 is sucked downward from the gap between the covering cylindrical portion 22A and the cylindrical portion 19. In addition, the solvent vapor sucked downward through the gap between the covering tubular portion 22A and the tubular portion 19 is collected through the return pipe 36 and reused as a solvent for the coating liquid 14.

The fixed hood 24 includes a plurality of hood sections 24A arranged above the plurality of cylindrical sections 19 so that their axes coincide with the respective cylindrical sections 19 within a range of a specified tolerance, and a lid section 24B that connects the plurality of hood sections 24A and covers the evaporation suppression member 22 and the plurality of cylindrical sections 19 from above. The hood section 24A of the fixed hood 24 is formed in a cylindrical shape. The inner diameter of this hood section 24A is set to be larger than the outer diameter of the base material 12.

The movable hood 26 comprises a plurality of hood sections 26A arranged radially outward of the plurality of hood sections 24A of the fixed hood 24, and a connection section 26B connecting the plurality of hood sections 26A. The hood section 26A of the movable hood 26 is formed in a cylindrical shape. The inner diameter of the hood section 26A of the movable hood 26 is set to an outer diameter slightly larger than the outer diameter of the hood section 24A of the fixed hood 24. Furthermore, the movable hood 26 can be moved in the vertical direction by a movement mechanism (not shown).

The gas exhaust section 28 is provided below the fixed hood 24 and the movable hood 26. The gas exhaust section 28 includes a pressure reducing section 38 provided below the liquid receiving section 20, and a plurality of suction pipes 40 connecting the space in the pressure reducing section 38 to the space between the fixed hood 24 and the evaporation suppression member 22. The gas exhaust section 28 also includes a pump 42 that sucks out the gas in the pressure reducing section 38. By operating this pump, the pressure in the space in the pressure reducing section 38 becomes lower than the pressure in the space between the fixed hood 24 and the evaporation suppression member 22. This makes it possible to suck in and exhaust the solvent vapor that evaporates from the coating liquid 14 attached to the surface of the substrate 12 located within the fixed hood 24 and the movable hood 26 via the plurality of suction pipes 40 and the pressure reducing section 38.

Next, we will explain the coating method using the coating device 10 described above.

As shown in FIG. 4, first, the multiple substrates 12 held by the multiple chuck portions 16 are moved upwardly of each of the cylindrical portions 19.

Next, as shown in FIG. 5, the multiple chuck portions 16 are lowered to lower the multiple substrates 12 held by the multiple chuck portions 16, and the multiple substrates 12 are inserted into the respective cylindrical portions 19. This process is the first process, or insertion process.

Next, as shown in FIG. 6, the chuck portions 16 are raised to raise the substrates 12 held by the chuck portions 16, and the substrates 12 are pulled up from the cylindrical portions 19. This step is the second step, or the pulling-up step.

In the lifting process, the movable hood 26 is raised so that the portion of the base material 12 that protrudes from the hood portion 24A of the fixed hood 24 is covered by the hood portion 26A of the movable hood 26 while the base material 12 is lifted.

During this pulling step, the pump 42 (see FIG. 1) is operated to suck and discharge the solvent vapor evaporated from the coating liquid 14 adhering to the surface of the substrate 12 located within the hood portion 24A of the fixed hood 24 and the hood portion 26A of the movable hood 26 through the multiple suction pipes 40 and the pressure reducing portion 38. At this time, the output of the pump 42 is adjusted so that the amount of gas containing the solvent vapor sucked and discharged from one hood portion (the hood portion 24A and the hood portion 26A) is a set amount within the range of 0.1 to 0.6 m ³ /h. The pump 42 may be operated from the insertion step through the pulling step.

In addition, during the pulling process, the lifting speed of the multiple chuck portions 16 is adjusted so that the lifting speed of the substrate 12 in the later stage of pulling the substrate 12 from the cylindrical portion 19 is slower than the lifting speed of the substrate 12 in the early stage of pulling.

Through the above steps, the coating liquid 14 is applied to the outer peripheral surfaces of the multiple substrates 12. As shown in Figure 7, the raised fixed hood 24 descends and returns to its original position.

(Effects of this embodiment)
Next, the effects of this embodiment will be described.

In the embodiment described above, during the lifting process, the solvent vapor evaporated from the coating liquid 14 attached to the surface of the substrate 12 located within the hood portion 24A of the fixed hood 24 and the hood portion 26A of the movable hood 26 is sucked and discharged via the multiple suction pipes 40 and the decompression portion 38. This makes it possible to suppress unevenness in the coating on the surface of the substrate 12 compared to a configuration in which only the evaporation suppressing member 22 is provided. In particular, unevenness in the coating occurring along the circumferential direction of the surface of the substrate 12 can be suppressed. In addition, by making the amount of gas containing solvent vapor sucked and discharged from one hood portion (the hood portion 24A and the hood portion 26A) to be within the range of 0.1 to 0.6 ^{m 3} /h, unevenness in the coating occurring along the circumferential direction of the surface of the substrate 12 can be effectively suppressed compared to a case outside this range.

In addition, in this embodiment, by raising the movable hood 26 in the lifting process, the portion of the substrate 12 that protrudes from the hood portion 24A of the fixed hood 24 is covered by the hood portion 26A of the movable hood 26. This makes it possible to extend the time that the outer peripheral surface of the substrate 12 to which the coating liquid 14 is attached is covered from the radially outer side by the hood portions 24A, 26A, compared to when only the fixed hood 24 is provided. This makes it possible to effectively suppress uneven coating that occurs along the circumferential direction of the surface of the substrate 12, compared to when only the fixed hood 24 is provided.

Furthermore, in this embodiment, the lifting speed of the substrate 12 in the later stage of lifting the substrate 12 from the cylindrical portion 19 is set slower than the lifting speed of the substrate 12 in the early stage of lifting. This makes it possible to effectively suppress uneven coating along the axial direction of the surface of the substrate 12, compared to when the substrate 12 is lifted from the cylindrical portion 19 at a constant speed.

In addition, in this embodiment, the coating liquid 14 is supplied to the 24 cylindrical parts 19 through six first flow dividers 32 having slit flow paths 32J and a single second flow divider 34. As a result, when the coating liquid 14 is supplied to the 24 cylindrical parts 19, a portion of the coating liquid 14 is prevented from stagnation in the first flow divider 32 and the second flow divider 34. This makes it possible to uniformize the coating liquid 14 in the 24 cylindrical parts 19. As a result, even when the coating liquid 14 is simultaneously applied to the surfaces of multiple substrates 12 as in this embodiment, it is possible to suppress the variation in the film thickness of the coating liquid 14 applied to the surface of each substrate 12. That is, it is possible to uniformize the quality of the coating on the surfaces of the multiple substrates 12. In addition, by suppressing a portion of the coating liquid 14 from stagnation in the first flow divider 32 and the second flow divider 34, it is possible to suppress the generation of aggregated fine particles in the coating liquid 14. This makes it possible to suppress defects caused by the adhesion of the aggregated fine particles to the surface of the substrate 12. This is particularly effective when using a coating liquid in which fine particles are dispersed in a volatile dispersion medium, such as the "charge transport layer" described below.

The coating device 10 of this embodiment can prevent uneven coating on the surface of the substrate 12 compared to a configuration in which only the evaporation suppression member 22 is provided.

The coating device 10 of this embodiment can prevent uneven coating on the surface of the substrate 12 compared to a configuration in which the hood member only has a fixed hood 24.

The coating device 10 of this embodiment can make the coating liquid 14 more uniform than a configuration in which the flow path of the flow divider has a circular cross section.

The coating method of this embodiment can prevent uneven coating on the surface of the substrate 12 compared to a method in which the substrate 12 is simply lifted from the cylindrical portion 19 in the second step.

According to the coating method of the present embodiment, when the amount of suction gas is less than 0.1 m ³ /h, the occurrence of uneven coating on the surface of the substrate 12 can be suppressed compared to when the amount is outside the numerical range exceeding 0.6 m ³ /h.

The coating method of this embodiment can effectively prevent uneven coating compared to when the substrate 12 is pulled up from the cylindrical portion 19 at a constant speed.

The coating method of this embodiment can prevent uneven coating on the surface of the substrate 12 compared to a configuration that uses only a fixed hood 24 as a hood member.

The coating method of this embodiment can achieve uniform coating quality on the surfaces of multiple substrates 12 compared to using a flow divider with a circular cross-section.

In the above-described embodiment, the coating liquid 14 is supplied to the plurality of cylindrical portions 19 through the first flow divider 32 and the second flow divider 34, but the embodiment of the present disclosure is not limited thereto. For example, as shown in FIG. 8, in a configuration in which the lower ends of the plurality of cylindrical portions 19 are open to a single flow path 44, a straightening plate 46 may be provided in the flow path 44. The straightening plate 46 is formed in a plate shape with the thickness direction being the vertical direction. The straightening plate 46 has a plurality of openings 46A that penetrate the straightening plate 46 in the vertical direction. The plurality of openings 46A are also arranged at regular intervals in the width direction and the depth direction of the device. The opening ratio of the straightening plate 46 is preferably 3% to 15%. By providing the straightening plate 46, it is possible to prevent a portion of the coating liquid 14 from remaining in the flow path 44, and to homogenize the coating liquid 14 in each cylindrical portion 19. This is particularly effective when using a coating liquid in which fine particles are dispersed in a volatile dispersion medium, such as the "charge transport layer" described later.

(Example of application to electrophotographic photoreceptor)
Next, an example in which the above-mentioned coating apparatus 10 and coating method are applied to the manufacture of an electrophotographic photoreceptor 48 (see FIG. 9) will be described.

As shown in FIG. 9, the conductive substrate 12 may be any of those that have been conventionally used. Examples include metals such as aluminum, nickel, chromium, and stainless steel, and plastic films provided with thin films of aluminum, titanium, nickel, chromium, stainless steel, gold, vanadium, tin oxide, indium oxide, and ITO, as well as paper and plastic films coated or impregnated with a conductive agent. The shape of the substrate 12 is not limited to a drum (cylindrical) shape, and may be a sheet or plate shape.

When a metal pipe is used as the substrate 12, the surface may be left as a bare pipe, or may have been previously treated by mirror cutting, etching, anodizing, rough cutting, centerless grinding, sandblasting, wet honing, or the like.

The undercoat layer 50 is provided as necessary for the purpose of preventing light reflection on the surface of the substrate 12 and preventing unnecessary carriers from flowing from the substrate 12 into the photosensitive layer 52. Materials for the undercoat layer 50 include metal powders such as aluminum, copper, nickel, and silver, conductive metal oxides such as antimony oxide, indium oxide, tin oxide, and zinc oxide, and conductive substances such as carbon fiber, carbon black, and graphite powder dispersed in a binder resin and applied to the substrate. Two or more types of metal oxide particles can also be mixed for use. Furthermore, the powder resistance can be controlled by subjecting the metal oxide particles to surface treatment with a coupling agent.

Examples of binder resins contained in the undercoat layer 50 include known polymer resin compounds such as acetal resins such as polyvinyl butyral, polyvinyl alcohol resins, casein, polyamide resins, cellulose resins, gelatin, polyurethane resins, polyester resins, methacrylic resins, acrylic resins, polyvinyl chloride resins, polyvinyl acetate resins, vinyl chloride-vinyl acetate-maleic anhydride resins, silicone resins, silicone-alkyd resins, phenolic resins, phenol-formaldehyde resins, melamine resins, and urethane resins, as well as charge transport resins having charge transport groups and conductive resins such as polyaniline. Among these, resins that are insoluble in the coating solvent of the upper layer are preferably used, and in particular phenolic resins, phenol-formaldehyde resins, melamine resins, urethane resins, and epoxy resins are preferably used.

The ratio of metal oxide particles to binder resin in the undercoat layer 50 is not particularly limited and can be set arbitrarily within a range that provides the desired electrophotographic photoreceptor characteristics.

When forming the undercoat layer 50, a coating liquid in which the above components are added to a predetermined solvent is used. Examples of such solvents include aromatic hydrocarbon solvents such as toluene and chlorobenzene, aliphatic alcohol solvents such as methanol, ethanol, n-propanol, iso-propanol, and n-butanol, ketone solvents such as acetone, cyclohexanone, and 2-butanone, halogenated aliphatic hydrocarbon solvents such as methylene chloride, chloroform, and ethylene chloride, cyclic or linear ether solvents such as tetrahydrofuran, dioxane, ethylene glycol, and diethyl ether, and ester solvents such as methyl acetate, ethyl acetate, and n-butyl acetate. These solvents can be used alone or in combination of two or more. When mixing, any solvent can be used as the mixed solvent as long as it can dissolve the binder resin.

Methods for dispersing metal oxide particles in the coating liquid for forming the undercoat layer include media dispersers such as ball mills, vibrating ball mills, attritors, sand mills, and horizontal sand mills, and medialess dispersers such as stirrers, ultrasonic dispersers, roll mills, and high-pressure homogenizers. Examples of high-pressure homogenizers include a collision method in which the dispersion liquid is dispersed by liquid-liquid collision or liquid-wall collision under high pressure, and a penetration method in which the dispersion liquid is dispersed by penetrating fine flow paths under high pressure.

Methods for applying the coating liquid for forming the undercoat layer thus obtained onto the substrate 12 include dip coating, push-up coating, wire bar coating, spray coating, blade coating, knife coating, curtain coating, and the like, using the coating device 10 of this embodiment. The thickness of the undercoat layer 50 is preferably 15 μm or more, and more preferably 20 to 50 μm. Resin particles can also be added to the undercoat layer 50 to adjust the surface roughness. Examples of the resin particles that can be used include silicone resin particles, crosslinked PMMA resin particles, and the like.

The charge generation layer 54 is formed by dispersing a charge generation material in a suitable binder resin. As such a charge generation material, phthalocyanine pigments such as metal-free phthalocyanine, chlorogallium phthalocyanine, hydroxygallium phthalocyanine, dichlorotin phthalocyanine, titanyl phthalocyanine, etc. can be used, and in particular, chlorogallium phthalocyanine crystals having strong diffraction peaks at Bragg angles (2θ±0.2°) of at least 7.4°, 16.6°, 25.5°, and 28.3° for CuKα characteristic X-rays, and Bragg angles (2θ±0.2°) of at least 7.7°, 9.3°, 16. Metal-free phthalocyanine crystals having strong diffraction peaks at 9°, 17.5°, 22.4° and 28.8°, hydroxygallium phthalocyanine crystals having strong diffraction peaks at Bragg angles (2θ±0.2°) of at least 7.5°, 9.9°, 12.5°, 16.3°, 18.6°, 25.1° and 28.3° to CuKα characteristic X-rays, and titanyl phthalocyanine crystals having strong diffraction peaks at Bragg angles (2θ±0.2°) of at least 9.6°, 24.1° and 27.2° to CuKα characteristic X-rays can be used. Other charge generating materials include quinone pigments, perylene pigments, indigo pigments, bisbenzimidazole pigments, anthrone pigments, quinacridone pigments, etc. These charge generating materials can be used alone or in combination of two or more.

Examples of the binder resin in the charge generating layer 54 include polycarbonate resins such as bisphenol A type or bisphenol Z type, acrylic resins, methacrylic resins, polyarylate resins, polyester resins, polyvinyl chloride resins, polystyrene resins, acrylonitrile-styrene copolymer resins, acrylonitrile-butadiene copolymers, polyvinyl acetate resins, polyvinyl formal resins, polysulfone resins, styrene-butadiene copolymer resins, vinylidene chloride-acrylonitrile copolymer resins, vinyl chloride-vinyl acetate-maleic anhydride resins, silicone resins, phenol-formaldehyde resins, polyacrylamide resins, polyamide resins, and poly-N-vinylcarbazole resins. These binder resins can be used alone or in combination of two or more types. The compounding ratio of the charge generating material to the binder resin is preferably in the range of 10:1 to 1:10.

When forming the charge generating layer 54, a coating liquid in which the above components are added to a specified solvent is used. Examples of such solvents include aromatic hydrocarbon solvents such as toluene and chlorobenzene, aliphatic alcohol solvents such as methanol, ethanol, n-propanol, iso-propanol, and n-butanol, ketone solvents such as acetone, cyclohexanone, and 2-butanone, halogenated aliphatic hydrocarbon solvents such as methylene chloride, chloroform, and ethylene chloride, cyclic or linear ether solvents such as tetrahydrofuran, dioxane, ethylene glycol, and diethyl ether, and ester solvents such as methyl acetate, ethyl acetate, and n-butyl acetate. These solvents can be used alone or in combination of two or more. When mixing, any solvent can be used as the mixed solvent as long as it can dissolve the binder resin.

To disperse the charge generating material in the resin, the coating liquid is subjected to a dispersion treatment. Dispersion methods that can be used include media dispersers such as ball mills, vibrating ball mills, attritors, sand mills, and horizontal sand mills, as well as medialess dispersers such as stirrers, ultrasonic dispersers, roll mills, and high-pressure homogenizers. Furthermore, examples of high-pressure homogenizers include the collision method, which disperses the dispersion liquid by liquid-liquid collision or liquid-wall collision under high pressure, and the penetration method, which disperses by penetrating fine flow paths under high pressure.

Methods for applying the coating solution thus obtained onto the undercoat layer 50 include a dip coating method using the coating device 10 of this embodiment, a push-up coating method, a wire bar coating method, a spray coating method, a blade coating method, a knife coating method, and a curtain coating method. The thickness of the charge generating layer 54 is preferably set in the range of 0.01 to 5 μm, and more preferably 0.05 to 2.0 μm.

The charge transport layer 56 is, for example, a layer containing a charge transport material and a binder resin. The charge transport layer may be a layer containing a polymer charge transport material.

Examples of charge transport materials include electron transport compounds such as quinone compounds such as p-benzoquinone, chloranil, bromanil, and anthraquinone; tetracyanoquinodimethane compounds; fluorenone compounds such as 2,4,7-trinitrofluorenone; xanthone compounds; benzophenone compounds; cyanovinyl compounds; and ethylene compounds. Examples of charge transport materials include hole transport compounds such as triarylamine compounds, benzidine compounds, arylalkane compounds, aryl-substituted ethylene compounds, stilbene compounds, anthracene compounds, and hydrazone compounds. These charge transport materials may be used alone or in combination of two or more, but are not limited to these.

From the viewpoint of charge mobility, the charge transport material is preferably a triarylamine derivative represented by the following structural formula (a-1) or a benzidine derivative represented by the following structural formula (a-2).

In structural formula (a-1), Ar ^T1 , Ar ^T2 , and Ar ^T3 each independently represent a substituted or unsubstituted aryl group, -C ₆ H ₄ -C(R ^T4 )=C(R ^T5 )(R ^T6 ), or -C ₆ H ₄ -CH=CH-CH=C(R ^T7 )(R ^T8 ). R ^T4 , R ^T5 , R ^T6 , R ^T7 , and R ^T8 each independently represent a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group.
Examples of the substituent on each of the above groups include a halogen atom, an alkyl group having from 1 to 5 carbon atoms, and an alkoxy group having from 1 to 5 carbon atoms. Examples of the substituent on each of the above groups also include a substituted amino group substituted with an alkyl group having from 1 to 3 carbon atoms.

In structural formula (a-2), R ^T91 and R ^T92 each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, or an alkoxy group having 1 to 5 carbon atoms. R ^T101 , R ^T102 , R ^T111 , and R ^T112 each independently represent a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an amino group substituted with an alkyl group having 1 to 2 carbon atoms, a substituted or unsubstituted aryl group, -C(R ^T12 )=C(R ^T13 )(R ^T14 ), or -CH=CH-CH=C(R ^T15 )(R ^T16 ), and R ^T12 , R ^T13 , R ^T14 , R ^T15 , and R ^T16 each independently represent a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group. Tm1, Tm2, Tn1 and Tn2 each independently represent an integer of 0 or more and 2 or less.
Examples of the substituent on each of the above groups include a halogen atom, an alkyl group having from 1 to 5 carbon atoms, and an alkoxy group having from 1 to 5 carbon atoms. Examples of the substituent on each of the above groups also include a substituted amino group substituted with an alkyl group having from 1 to 3 carbon atoms.

Here, among the triarylamine derivatives represented by structural formula (a-1) and the benzidine derivatives represented by structural formula (a-2), the triarylamine derivatives having "-C ₆ H ₄ -CH═CH-CH═C(R ^T7 )(R ^T8 )" and the benzidine derivatives having "-CH═CH-CH═C(R ^T15 )(R ^T16 )" are particularly preferred from the viewpoint of charge mobility.

As the polymer charge transport material, known materials having charge transport properties such as poly-N-vinylcarbazole and polysilane are used. In particular, polyester-based polymer charge transport materials disclosed in JP-A-8-176293 and JP-A-8-208820 are particularly preferred. The polymer charge transport material may be used alone or in combination with a binder resin.

Examples of the binder resin used in the charge transport layer 56 include polycarbonate resin, polyester resin, polyarylate resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinylidene chloride resin, polystyrene resin, polyvinyl acetate resin, styrene-butadiene copolymer, 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-N-vinylcarbazole, polysilane, etc. Among these, polycarbonate resin or polyarylate resin is preferable as the binder resin. These binder resins are used alone or in combination of two or more.
The compounding ratio of the charge transport material to the binder resin is preferably from 10:1 to 1:5 by mass.

The charge transport layer 56 may also contain other known additives.

The charge transport layer 56 may also contain a copolymer and fluorine-based resin particles. This copolymer is a fluorine-based graft polymer containing repeating units represented by structural formula A and structural formula B. Specifically, structural formula A is a macromonomer made of, for example, an acrylic acid ester compound, a methacrylic acid ester compound, etc., and structural formula B is, for example, perfluoroalkylethyl (meth)acrylate, perfluoroalkyl (meth)acrylate, and is a resin synthesized by, for example, graft polymerization using these. Here, (meth)acrylate refers to acrylate or methacrylate.

In the copolymer, the content ratio of structural formula A to structural formula B, i.e., l:m, is preferably (A) 1:9 to 9:1, and more preferably 3:7 to 7:3. When l:m is in the range of (A) 3:7 to 7:3, the tetrafluoroethylene resin can be dispersed in both rows.

The content of the copolymer according to this embodiment in the surface layer, i.e., the charge transport layer 56, is preferably 1% by mass or more and 5% by mass or less relative to the content (by mass) of the fluororesin particles in the surface layer. The average molecular weight of the fluororesin graft polymer is preferably 20,000 to 80,000, more preferably 50,000 to 70,000. In this embodiment, the average molecular weight of the fluororesin particles refers to a value measured by GPC.

The content of the fluororesin particles relative to the total solid content of the surface layer, i.e., the charge transport layer 56, is preferably 1% by mass or more and 15% by mass or less, and more preferably 2% by mass or more and 12% by mass or less. If the content of the fluororesin particles is 2% by mass or more, the surface energy of the charge transport layer 56 can be reduced, and the durability of the electrophotographic photoreceptor can be improved. Furthermore, if the content of the fluororesin particles is 15% by mass or less, a decrease in light transmittance and a decrease in film strength are unlikely to occur.

As the fluororesin particles, it is desirable to appropriately select one or more types from tetrafluoroethylene resin (PTFE), trifluorochloroethylene resin, hexafluoropropylene resin, vinyl fluoride resin, vinylidene fluoride resin, difluorodichloroethylene resin, and copolymers thereof, with tetrafluoroethylene resin and vinylidene fluoride resin being more preferred, and tetrafluoroethylene resin being particularly preferred. When the fluororesin particles according to this embodiment contain tetrafluoroethylene resin, abrasion resistance effects are obtained.

Methods for applying the thus obtained charge transport layer forming coating liquid onto the charge generating layer include dip coating, push-up coating, wire bar coating, spray coating, blade coating, knife coating, curtain coating, etc. The thickness of the charge transport layer 56 is preferably 15 μm or more, more preferably 20 to 50 μm.

Industrially, multiple substrates 12 are often coated simultaneously by a dip coating method using the coating device 10 of this embodiment in which the liquid circulates between the coating tank 18 and the liquid holding tank. If the immersion speed, which is the descending speed of the substrate 12, is increased to increase productivity, the amount of coating liquid 14 overflowing from the cylindrical portion 19 increases rapidly, causing the return pipe 36 to become clogged, so a method of reducing the circulating flow rate of the coating liquid 14 when the substrate 12 is immersed may be used. In particular, when coating the charge transport layer 56, which is a high-viscosity liquid, it is preferable to reduce the circulating flow rate when the substrate 12 is immersed by 30% or more.

In addition, when the requirement for uniformity in film thickness is not strict, such as for the undercoat layer 50, or when using a coating liquid 14 where even a slight air current can cause coating unevenness or coating defects, it is effective to use mesh-shaped hood parts 24A, 26A. In this case, it is desirable to set the mesh size of the hood parts 24A, 26A to 50 μm to 1000 μm. Also, different mesh sizes may be used in layers, for example, 600 μm to 1000 μm on the inside and 50 μm to 100 μm on the outside.

(Specific example)
The present invention will be described in more detail below based on examples and comparative examples, but the present invention is not limited to the following examples in any way.

An aluminum support of 30 mm diameter x 365 mm length was prepared. The undercoat layer was prepared by mixing 100 parts by weight of zinc oxide (average particle size 70 nm: manufactured by Teika Co., Ltd.; specific surface area value 15 m2/g) with 500 parts by weight of toluene, adding 1.25 parts by weight of a silane coupling agent (KBM603: manufactured by Shin-Etsu Chemical Co., Ltd.), and stirring for 2 hours. The toluene was then removed by vacuum distillation, and the mixture was baked at 120°C for 3 hours to obtain a zinc oxide pigment surface-treated with a silane coupling agent.

60 parts by weight of the zinc oxide pigment that had been subjected to the surface treatment, 0.6 parts by weight of alizarin, 13.5 parts by weight of a curing agent blocked isocyanate (Sumidur 3175, manufactured by Sumitomo Bayern Urethane Co., Ltd.), and 15 parts by weight of butyral resin (BM-1, manufactured by Sekisui Chemical Co., Ltd.) were dissolved in 85 parts by weight of methyl ethyl ketone to obtain a solution of 38 parts by weight and 25 parts by weight of methyl ethyl ketone, and the solution was dispersed for 2 hours in a sand mill using glass beads with a diameter of 1 mm to obtain a dispersion. 0.005 parts by weight of dioctyltin dilaurate as a catalyst and 4.0 parts by weight of silicone resin particles (Tospearl 145, manufactured by GE Toshiba Silicone Co., Ltd.) were added to the obtained dispersion to obtain a coating liquid for the undercoat layer.

This undercoat layer coating solution was applied to the aluminum substrate using the coating device 10 of this embodiment for dip coating, which is equipped with hood sections 24A and 26A made by layering a wire mesh with a mesh size of 87 μm on the outside of a wire mesh with a mesh size of 850 μm. The coating speed was adjusted so that the film thickness after drying would be 19.0 μm, and the coating was dried and cured at 180° C. for 40 minutes to form the undercoat layer 50.

First, a mixture consisting of 15 parts of hydroxygallium phthalocyanine, which has diffraction peaks at Bragg angles (2θ±0.2°) of at least 7.3°, 16.0°, 24.9°, and 28.0° in the X-ray diffraction spectrum using Cukα radiation as a charge generating material, 10 parts of vinyl chloride/vinyl acetate copolymer resin (VMCH, manufactured by Nippon Unicar Co., Ltd.) as a binder resin, and 200 parts of n-butyl acetate was dispersed in a sand mill using glass beads with a diameter of 1 mm for 4 hours. 175 parts by mass of n-butyl acetate and 180 parts by mass of methyl ethyl ketone were added to the obtained dispersion and stirred to obtain a coating liquid for the charge generating layer 54. This coating liquid for the charge generating layer 54 was applied by dip coating on the undercoat layer 50 and dried at room temperature (25°C) to form a charge generating layer with a thickness of 0.2 μm.

Next, 0.5 parts by mass of A tetrafluoroethylene resin particles (average primary particle size: 0.2 μm) and 0.01 parts by mass of a fluoroalkyl group-containing copolymer (weight average molecular weight 50,000, l:m=1:1, s=1, n=60) containing a repeating unit represented by the following structural formula were mixed with 4 parts by mass of tetrahydrofuran and 1 part by mass of toluene at a liquid temperature of 20°C for 30 hours under stirring to obtain a tetrafluoroethylene resin particle suspension. Next, 2 parts by mass of N,N'-bis(3-methylphenyl)-N,N'-diphenylbenzidine, 2 parts by mass of N,N'-bis(3,4-dimethylphenyl)biphenyl-4-amine, 6 parts by mass of bisphenol Z-type polycarbonate resin (viscosity average molecular weight: 50,000) as a charge transport material, and 0.1 parts by mass of 2,6-di-t-butyl-4-methylphenol as an antioxidant were mixed and dissolved in 24 parts by mass of tetrahydrofuran and 11 parts by mass of toluene. Liquid A was added to this liquid B and stirred and mixed, and then the liquid was dispersed once at a pressure of 500 kgf/cm2 using a high-pressure homogenizer (manufactured by Yoshida Kikai Kogyo Co., Ltd.) equipped with a through-type chamber with fine flow paths. 8 ppm of dimethyl silicone oil (product name: KP-340, manufactured by Shin-Etsu Silicone Co., Ltd.) was added to the liquid and thoroughly stirred to obtain a coating liquid for forming the charge transport layer 56.

Example 1
The coating device 10 shown in FIG. 1 was used. The coating liquid 14 for the charge transport layer 56 obtained as described above was put into the coating tank 18, and the temperature and viscosity were adjusted to 30.0° C. and 520 mPa·s. The coating device 10 used had 25 (5×5) cylindrical tubular parts 19 with an inner diameter of Φ60 mm and a depth of 500 mm, arranged at a pitch of 85 mm. Around the cylindrical tubular parts 19, an evaporation suppressing member 22 having a cylindrical covering tubular part 22A that covers the outer periphery of the tubular part 19 at a predetermined interval was installed. In addition, a fixed hood 24 having a hood part 24A with an inner diameter of 60 mm and a height of 200 mm, and a movable hood 26 that can be raised and lowered having a hood part 26A with an inner diameter of 80 mm and a height of 200 mm were provided. The hood part 24A of the fixed hood 24 and the hood part 26A of the movable hood 26 before being raised were provided at a height of 30 mm from the liquid level of the tubular part 19.

An aluminum pipe having an outer diameter of 30 mm and a length of 340 mm was used as the substrate 12. Using the coating liquid 14 for the charge transport layer 56 in the coating device 10 of FIG. 1, dip coating was performed on the charge generation layer 54 at a coating speed of 150 mm/min while the gas in one hood section (the hood section 24A and the hood section 26A) was discharged at a flow rate of 0.3 m ³ /h by the gas exhaust section 28. In the process of lifting the substrate 12 from the cylindrical section 19, the movable hood 26 was raised by 200 mm when the upper end of the substrate 12 reached the upper end of the hood section 24A of the fixed hood 24. After coating, the substrate was dried at 120° C. for 30 minutes to obtain a charge transport layer 56 having a film thickness of 40 μm.

(evaluation)
The film thickness on the surface of the substrate 12 produced in Example 1 above was measured at 10 mm intervals and every 90° from the coating start position on the upper end side to 20 mm to 300 mm using an eddy current film thickness measuring device (manufactured by our company), and the average value was taken as the average film thickness A (μm). The difference between the maximum and minimum film thickness values at all measurement points was taken as the film thickness unevenness, which is the coating unevenness. As a result, in Example 1, the coating unevenness could be suppressed to 2.0 μm or less.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above, and it is of course possible to implement the present invention in various other modified forms without departing from the spirit of the present invention.

10 Coating device 12 Substrate 14 Coating liquid 18 Coating tank 19 Cylindrical portion 22 Evaporation suppressing member 22A Covering cylindrical portion 24 Fixed hood (hood member)
24A Hood portion 26 Movable hood (hood member)
26A Hood portion 28 Gas exhaust portion 32 First flow divider (flow divider)
32A Outer wall part (first opposing part)
32C Inflow section 32D Inner wall section (second opposing section)
32G Outlet portion 32J Slit flow path and 34 Second flow divider (flow divider)

Claims (5)

a coating tank having a cylindrical portion filled with a coating liquid and from which the coating liquid overflows from an upper portion, the substrate being immersed in the cylindrical portion from above;
an evaporation suppressing member having a cylindrical covering portion that surrounds the cylindrical portion from the radially outer side and suppresses evaporation of the coating liquid;
a hood member provided above the coating tank and having a cylindrical hood portion that covers the coating tank from above and covers the base material from the radially outer side;
a gas exhaust section located within the hood section, which exhausts solvent vapor evaporated from the coating liquid attached to the surface of the substrate;
a flow divider including an inflow section into which the coating liquid flows, a plurality of outflow sections through which the coating liquid flows out and which are connected to the plurality of coating tanks, and a first opposing section and a second opposing section disposed opposite to each other, the first opposing section and the second opposing section forming a slit flow path connecting the inflow section and the plurality of outflow sections;
A coating device comprising: The hood member includes a fixed hood having the hood portion and being immovable relative to the coating tank, and a movable hood having the hood portion and being movable in a vertical direction relative to the fixed hood,
The coating apparatus according to claim 1 , wherein the movable hood rises relative to the fixed hood when the substrate is lifted from the coating tank. Using the coating device according to claim 1 or 2 ,
a first step of lowering the base material to insert the base material into the cylindrical portion;
a second step of lifting the substrate from within the cylindrical portion;
Including,
In the second step, the gas exhaust unit sucks in and exhausts solvent vapor evaporated from the coating liquid attached to the surface of the base material located in the hood unit,
Furthermore, in the second step, a pulling speed of the base material in a later stage of pulling the base material out of the cylindrical portion is set to be slower than a pulling speed of the base material in an initial stage of pulling the base material.
Application method. Using the coating device according to claim 2,
The coating method according to claim 3 , wherein in the second step, the movable hood is raised to lift the substrate while covering a portion of the substrate protruding from the hood portion of the fixed hood with the hood portion of the movable hood. Using the coating device according to claim 1 or 2 ,
a first step of lowering the base material to insert the base material into the cylindrical portion;
a second step of lifting the substrate from within the cylindrical portion;
Including,
In the second step, the gas exhaust unit sucks in and exhausts solvent vapor evaporated from the coating liquid attached to the surface of the base material located in the hood unit,
In the first step, a plurality of the base materials are inserted into a plurality of the cylindrical portions,
In the second step, the plurality of base materials are pulled up from the respective cylindrical portions.
Application method.