JP7639438B2 - 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 dip coating device for manufacturing electrophotographic photoreceptors having a substantially cylindrical dip coating tank for manufacturing electrophotographic photoreceptors in which an undercoat layer, a charge generating layer, or a charge transport layer is formed by dip coating on a conductive support for electrophotographic photoreceptors. In the dip coating device for manufacturing electrophotographic photoreceptors described in this document, the upper end of the dip coating tank has at least one or more dams provided at non-uniform intervals, and the dams can be removed and/or the size can be controlled.

Patent No. 4075322

However, if bubbles remaining on the upper surface of the cylindrical part of the coating tank adhere to the surface of the substrate, there is a concern that defects may occur in the coating film on 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 defects caused by bubbles in the coating film on the surface of the substrate, compared to a coating tank in which the inner R or C chamfer and the outer R or C chamfer at the upper end of the cylindrical portion of the coating tank are the same dimensions.

The coating device of the first aspect is equipped with a chuck section that supports a cylindrically formed substrate and moves in the vertical direction, and a coating tank having a tubular section that is filled with a coating liquid from which the coating liquid overflows from the top, in which the substrate is immersed in the tubular section from above, and in which, in a cross-sectional view cut along the vertical direction, the corner R dimension or C chamfer dimension of a radially inner corner at the upper end of the tubular section and the corner R dimension or C chamfer dimension of a radially outer corner at the upper end of the tubular section are different from each other.

The second aspect of the coating device is the coating device of the first aspect, in which the radially inner corner and the radially outer corner at the upper end of the cylindrical portion are rounded, and the R dimension of the radially inner corner at the upper end of the cylindrical portion is set to a smaller dimension than the R dimension of the radially outer corner at the upper end of the cylindrical portion.

The third aspect of the applicator is the applicator of the first or second aspect, in which the area between the radially inner corner and the radially outer corner at the upper end of the cylindrical portion is flat with the surface facing upward.

The coating method of the fourth aspect uses a coating device of any one of the first to third aspects, and includes a first step of inserting the substrate into the cylindrical portion, and a second step of lifting the substrate out of the cylindrical portion.

The coating method of the fifth aspect is such that in the first step of the coating method of the fourth aspect, the average rising speed of the coating liquid rising between the radially outer surface of the substrate and the radially inner surface of the cylindrical portion is set to 50 cm/min or more.

The coating device of the first aspect can prevent defects caused by bubbles in the coating film on the surface of the substrate, compared to a coating device in which the inner R or C chamfer and the outer R or C chamfer at the upper end of the cylindrical portion of the coating tank have the same dimensions.

The coating device of the second aspect can prevent defects caused by bubbles in the coating film on the surface of the substrate, compared to a configuration in which the corner R dimension of the radially inner corner at the upper end of the cylindrical portion is set to a dimension larger than the corner R dimension of the radially outer corner at the upper end of the cylindrical portion.

The coating device of the third aspect can prevent defects caused by bubbles in the coating film on the surface of the substrate compared to a configuration in which there is no flat portion between the radially inner corner and the radially outer corner at the upper end of the cylindrical portion.

The coating method of the fourth aspect can prevent defects caused by bubbles in the coating film on the surface of the substrate, compared to a method in which the inner R or C chamfer and the outer R or C chamfer at the upper end of the cylindrical part of the coating tank are the same size.

The coating method of the fifth aspect can suppress defects caused by bubbles in the coating film on the surface of the substrate, compared to a method in which the average rising speed of the coating liquid rising between the radially outer surface of the substrate and the radially inner surface of the cylindrical portion is less than 50 cm/min.

FIG. 2 is a side cross-sectional view that shows a schematic view of the coating device, illustrating a state before a substrate is inserted into a 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. 1 is a side cross-sectional view showing a cross section of an upper end portion of a cylindrical portion to which the configuration of Example 1 is applied, cut along the up-down direction. 11 is a side cross-sectional view showing a cross section of an upper end portion of a cylindrical portion to which the configuration of Example 2 is applied, cut along the up-down direction. FIG. 13 is a side cross-sectional view showing a cross section of an upper end portion of a cylindrical portion to which the configuration of Example 3 is applied, cut along the up-down direction. FIG. 13 is a side cross-sectional view showing a cross section of an upper end portion of a cylindrical portion to which the configuration of Example 4 is applied, cut along the vertical direction. FIG. 13 is a cross-sectional view showing a cross section of an upper end portion of a cylindrical portion to which the configuration of Example 5 is applied, cut along the vertical direction. FIG. 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 apply coating liquid 14 to the radially outer surface 12D of a cylindrical substrate 12. This 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 suppression member 22 that suppresses evaporation of the coating liquid 14, and a fixed hood 24 that covers the coating tank 18 from above.

The chuck portion 16 is configured to be able to grip the upper end portion 12A of the substrate 12 by, for example, operating compressed air or an electric actuator. In this embodiment, a plurality of chuck portions 16 are arranged at intervals in the device width direction and device depth direction. The plurality of chuck portions 16 are held by a chuck holding member 30. The number of chuck portions 16 may be set appropriately taking into consideration the number of substrates 12 to be processed simultaneously.

The coating tank 18 is filled with the coating liquid 14 by being supplied 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 12 in the cylindrical portion 19 from above. In this embodiment, multiple cylindrical portions 19 are arranged at intervals in the width direction and depth direction of the device. The number of cylindrical portions 19 may be set appropriately in consideration of the number of substrates 12 to be processed simultaneously, similar to the number of chuck portions 16.

The liquid receiving section 20 is configured to include a plate-shaped bottom surface section 20A that spreads 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 is formed with a plurality of through holes 20C through which the plurality of cylindrical sections 19 are inserted. The gap between the outer peripheral surface of the cylindrical section 19 and the through holes 20C 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 upper end of the cylindrical section 19 and reaches the bottom surface section 20A flows along the bottom surface section 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 in the liquid holding tank from the return pipe 36 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 each of 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 the upper side. 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. The solvent vapor sucked downward from the gap between the covering cylindrical portion 22A and the cylindrical 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.

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

As shown in FIG. 1, 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. 2, 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. 3, 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.

Through the above steps, the coating liquid 14 is applied to the radially outer surfaces 12D of the multiple substrates 12, and a coating film 15 is formed on the radially outer surfaces 12D of the multiple substrates 12. Note that in the above steps, the coating liquid 14 for forming the charge generating layer 54 (see FIG. 9) described below is used to apply the coating liquid 14 to the radially outer surfaces 12D of the multiple substrates 12.

(Configuration and method for facilitating foam discharge)
Next, a description will be given of a configuration and a method for easily discharging bubbles 14B on the upper surface 14A of the coating liquid 14 spilling out from the upper end 19A of the cylindrical portion 19. The configurations and methods of the embodiments described below are applied to the coating device 10 and the coating method described above.

Example 1
4 shows a cross section of the upper end 19B of the cylindrical portion 19 to which the configuration of Example 1 for facilitating the discharge of the bubbles 14B is applied. As shown in this figure, in the cylindrical portion 19 of this embodiment, the radially inner corner 19C and the radially outer corner 19D at the upper end 19A of the cylindrical portion 19 are R-chamfered. In the cylindrical portion 19 of this embodiment, the corner R dimension R1 of the radially inner corner 19C at the upper end 19A of the cylindrical portion 19 and the corner R dimension R2 of the radially outer corner 19D are set to different dimensions. Specifically, the corner R dimension R1 of the radially inner corner 19C at the upper end 19A of the cylindrical portion 19 is set to 2.5 mm, and the corner R dimension R2 of the radially outer corner 19D is set to 3 mm. Here, in a preliminary test or the like, the outer diameter dimension D1 of the bubbles 14B floating on the upper surface 14A of the coating liquid 14 is measured. The average value of the outer diameter dimension D1 of the bubbles 14B is set to D2. It was discovered that the bubbles 14B floating on the upper surface 14A of the coating liquid 14 can be easily discharged by setting the corner R dimension R1 of the radially inner corner 19C at the upper end 19A of the cylindrical portion 19 and the corner R dimension R2 of the radially outer corner 19D at the upper end 19A of the cylindrical portion 19 to a dimension of 1/3 or more of the average value D2 of the outer diameter dimension D1 of the bubbles 14B, more preferably to a dimension of 1/2 or more. In this embodiment, since the average value D2 of the outer diameter dimension D1 of the bubbles 14B was 5 mm, the corner R dimension R1 of the radially inner corner 19C at the upper end 19A of the cylindrical portion 19 and the corner R dimension R2 of the radially outer corner 19D at the upper end 19A of the cylindrical portion 19 are set to 2.5 mm or more.

In this embodiment, the upper end 19A of the cylindrical portion 19 has a flat surface 19E between the radially inner corner 19C and the radially outer corner 19D, which faces upward. The shape of this flat surface 19E when viewed from above is annular. The radial width dimension W of the cylindrical portion 19 at the flat surface 19E is set to 3 mm.

4, the substrate 12 being inserted into the cylindrical portion 19 in the above-mentioned insertion step (see FIG. 2) is shown by a two-dot chain line. In this embodiment, in the insertion step, the amount of coating liquid 14 supplied to the cylindrical portion 19 is adjusted so that the average rising speed V of the coating liquid 14 rising between the radially outer surface 12D of the substrate 12 and the radially inner surface 19F of the cylindrical portion 19 becomes a predetermined speed. The average rising speed V [cm/min] of the coating liquid 14 is calculated by the following (Equation 1) when the amount of coating liquid 14 supplied to the cylindrical portion 19 is Q [ ^cm3 /min], the area between the radially outer surface 12D of the substrate 12 and the radially inner surface 19F of the cylindrical portion 19 in a cross-sectional view taken along the width and depth directions of the device, the volumetric insertion speed of the substrate is ^{X cm3 /} min, and the internal cross-sectional area of the cylindrical portion 19A is Y ^cm2 .
(Formula 1) V=(Q+X)/(Y-A)
In this embodiment, the average rising speed V of the coating liquid 14 is set to a predetermined value of 50 cm/min or more.

Example 2
5 shows a cross section of an upper end 19B of a cylindrical portion 19 to which the configuration of Example 2 for facilitating the discharge of foam 14B is applied. As shown in this figure, the cylindrical portion 19 of this example is configured similarly to the cylindrical portion 19 of Example 1 (see FIG. 4) described above, except that the cylindrical portion 19 of this example does not include a flat portion 19E. Note that the same reference numerals as those of the cylindrical portion 19 of Example 1 are used for the portions of the cylindrical portion 19 of Example 2 that correspond to those of the cylindrical portion 19 of Example 1 (see FIG. 4).

Example 3
6 shows a cross section of an upper end 19B of a cylindrical portion 19 to which the configuration of the third embodiment for facilitating the discharge of bubbles 14B is applied. As shown in this figure, the cylindrical portion 19 of this embodiment is configured similarly to the cylindrical portion 19 of the first embodiment (see FIG. 4) except that the corner R dimension R1 of a radially inner corner 19C at the upper end 19A of the cylindrical portion 19 is set to 3 mm and the corner R dimension R2 of a radially outer corner 19D is set to 2.5 mm. Note that the same reference numerals as those of the cylindrical portion 19 of the first embodiment are used for the portions of the cylindrical portion 19 of the third embodiment corresponding to those of the cylindrical portion 19 of the first embodiment (see FIG. 4).

(Effects of this embodiment)
Next, the effects of the above-mentioned first to third embodiments will be described.

First, in order to confirm the effects of the above-mentioned Examples 1 and 2, a test was conducted to check the proportion of bubbles 14B discharged from the upper surface 14A of the coating liquid 14 from the start to the completion of the insertion process. The completion of the insertion process refers to the point in time when the substrate 12 is lowered to the lowest position, as shown in FIG. 2.

In this test, a predetermined number of bubbles 14B were first floated on the upper surface 14A of the coating liquid 14. The bubbles 14B were formed with a dropper. Next, an insertion process was performed, and the number of bubbles 14B floating on the upper surface 14A of the coating liquid 14 at the completion of the insertion process was counted to calculate the percentage of bubbles 14B that had been expelled.

Table 1 below shows the conditions and results of the above test performed using the cylindrical portion 19 of Example 1, Example 2, and Comparative Example. The cylindrical portion 19 of the Comparative Example is configured similarly to the cylindrical portion 19 of Example 1, except that the corner R dimension R1 of the radially inner corner 19C at the upper end 19A of the cylindrical portion 19 is set to 0.5 mm, and the corner R dimension R2 of the radially outer corner 19D is set to 0.5 mm. This test was performed by setting the average rising speed V of the coating liquid 14 to 30 [cm/min], 40 [cm/min], 50 [cm/min], and 60 [cm/min] for each of the cylindrical portions 19 of Example 1, Example 2, and Comparative Example.

As shown in Table 1 above, the cylindrical portions 19 of Examples 1 and 2 have a higher rate of being able to expel bubbles 14B floating on the upper surface 14A of the coating liquid 14 than the cylindrical portion 19 of the comparative example. This shows that the cylindrical portions 19 of Examples 1 and 2 have a higher rate of being able to expel bubbles 14B floating on the upper surface 14A of the coating liquid 14 than the cylindrical portion 19 of the comparative example in which the corner R dimension R1 and corner R dimension R2 at the upper end 19A of the cylindrical portion 19 are the same. This makes it possible to suppress defects caused by bubbles 14B from occurring in the coating film 15 on the radially outer surface 12D of the substrate 12.

Also, as shown in Table 1 above, the cylindrical portion 19 of Example 1 is able to discharge a higher proportion of bubbles 14B floating on the upper surface 14A of the coating liquid 14 than the cylindrical portion 19 of Example 2. This shows that the cylindrical portion 19 of Example 1 is able to discharge a higher proportion of bubbles 14B floating on the upper surface 14A of the coating liquid 14 than the cylindrical portion 19 of Example 2, which does not have the flat portion 19E.

Table 2 below shows the conditions and results of the above test conducted using the cylindrical portion 19 of Example 1 and Example 3. Note that this test was conducted for each of the cylindrical portions 19 of Example 1 and Example 3 by setting the average rising speed V of the coating liquid 14 to 35 [cm/min], 40 [cm/min], 45 [cm/min], 50 [cm/min], and 60 [cm/min], respectively.

As shown in Table 2 above, the cylindrical portion 19 of Example 1 is able to discharge a higher percentage of bubbles 14B floating on the upper surface 14A of the coating liquid 14 than the cylindrical portion 19 of Example 3. This shows that the cylindrical portion 19 of Example 1 is able to discharge a higher percentage of bubbles 14B floating on the upper surface 14A of the coating liquid 14 than the configuration of the cylindrical portion 19 of Example 3 in which the corner R dimension R1 is set to be larger than the corner R dimension R2.

In addition, as shown in Tables 1 and 2 above, in the cylindrical portion 19 of Comparative Example 1, by setting the average rising speed V of the coating liquid 14 to 50 cm/min or more, it is possible to remove 100% of the bubbles 14B floating on the upper surface 14A of the coating liquid 14.

As described above, the coating device 10 described above can suppress defects caused by bubbles 14B in the coating film 15 on the surface of the substrate 12, compared to a coating tank 18 having the same corner R dimension R1 and corner R dimension R2 at the upper end 19A of the cylindrical portion 19.

The coating device 10 described above can prevent defects caused by bubbles 14B from occurring in the coating film 15 on the surface of the substrate 12, compared to the configuration of the cylindrical portion 19 in Example 3 in which the corner R dimension R1 is set to a dimension larger than the corner R dimension R2.

Furthermore, the coating device 10 described above can suppress the occurrence of defects due to bubbles 14B in the coating film 15 on the surface of the substrate 12, compared to a configuration in which the flat portion 19E is not provided between the radially inner corner 19C and the radially outer corner 19D at the upper end 19A of the cylindrical portion 19.

The coating method described above can prevent defects caused by bubbles 14B from occurring in the coating film 15 on the surface of the substrate 12, compared to a method in which the corner R dimension R1 and corner R dimension R2 at the upper end 19A of the cylindrical portion 19 of the coating tank 18 are the same.

Furthermore, the coating method described above can suppress the occurrence of defects due to bubbles 14B in the coating film 15 on the surface of the substrate 12, compared to a method in which the average rising speed V of the coating liquid 14 is less than 50 cm/min.

In the above-described embodiments, the radially inner corner 19C and the radially outer corner 19D at the upper end 19A of the cylindrical portion 19 are R-shaped, but the embodiments of the present disclosure are not limited thereto. For example, as in the cylindrical portion 19 to which the configuration of the fourth embodiment shown in FIG. 7 is applied and the cylindrical portion 19 to which the configuration of the fifth embodiment shown in FIG. 8 is applied, the radially inner corner 19C and the radially outer corner 19D at the upper end 19A of the cylindrical portion 19 may be C-chamfered. In the cylindrical portion 19 to which the configuration of the fourth embodiment shown in FIG. 7 is applied, the C-chamfer dimension C1 of the radially inner corner 19C at the upper end 19A of the cylindrical portion 19 is set to a larger dimension than the C-chamfer dimension C2 of the radially outer corner 19D. In addition, in the cylindrical portion 19 to which the configuration of Example 5 shown in FIG. 8 is applied, the C chamfer dimension C1 of the radially inner corner 19C at the upper end 19A of the cylindrical portion 19 is set to a smaller angle dimension than the C chamfer dimension C2 of the radially outer corner 19D.

(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. Examples of 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 materials 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 and used. Furthermore, the powder resistance can be controlled by subjecting the metal oxide particles to surface treatment with a coupling agent. In the following description, the undercoat layer 50 may be referred to as UCL (Under Coat Layer).

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 solution for forming the undercoat layer thus obtained onto the substrate 12 include dip coating using the coating device 10 described above, push-up coating, wire bar coating, spray coating, blade coating, knife coating, curtain coating, and the like. 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 and crosslinked PMMA resin particles.

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. In the following description, the charge generation layer 54 may be referred to as CGL (Charge Generation Layer).

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 dip coating using the coating device 10 described above, push-up coating, wire bar coating, spray coating, blade coating, knife coating, curtain coating, and the like. The thickness of the charge generating layer 54 is preferably set in the range of 0.01 to 5 μm, more preferably 0.05 to 2.0 μm.

The charge transport layer 56 corresponds to the surface layer of the electrophotographic photoreceptor 48, and contains the copolymer according to this embodiment and fluororesin particles as described above. The copolymer according to this embodiment is a fluorine-based graft polymer containing repeating units represented by structural formula A and structural formula B, and is a resin synthesized, for example, by graft polymerization using a macromonomer made of an acrylic acid ester compound, a methacrylic acid ester compound, etc., and perfluoroalkylethyl (meth)acrylate or perfluoroalkyl (meth)acrylate. Here, (meth)acrylate refers to acrylate or methacrylate.

In the copolymer according to this embodiment, 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.

In structural formula A and structural formula B, examples of the alkyl group represented by R1, R2, R3, and R4 include a methyl group, an ethyl group, and a propyl group. R1, R2, R3, and R4 are preferably a hydrogen atom or a methyl group, and among these, a methyl group is more preferable.

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.

The method for applying the thus obtained charge transport layer forming coating liquid onto the charge generation layer 54 is preferably a dip coating method using the coating device 10 described above. Other methods for applying onto the charge generation layer 54 include 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.

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 invention in various other modified forms without departing from the spirit of the invention.

10 Coating device 12 Substrate 12D Radially outer surface of substrate 14 Coating liquid 16 Chuck portion 18 Coating tank 19 Cylindrical portion 19A Upper end 19C of cylindrical portion Radially inner corner 19D at upper end of cylindrical portion Radially outer corner 19F at upper end of cylindrical portion Radially inner surface R1 of cylindrical portion Corner R dimension R2 of radially inner corner at upper end of cylindrical portion Corner R dimension C1 of radially outer corner at upper end of cylindrical portion C2 of radially inner corner at upper end of cylindrical portion C chamfer dimension C2 of radially outer corner at upper end of cylindrical portion

Claims (5)

A chuck portion that supports a cylindrically formed substrate and moves in a vertical direction;
a coating tank having a cylindrical portion which is filled with a coating liquid and from which the coating liquid overflows from the top, the substrate being immersed in the cylindrical portion from above, the coating tank having a corner R dimension or C chamfer dimension of a radially inner corner at the upper end of the cylindrical portion and a corner R dimension or C chamfer dimension of a radially outer corner at the upper end of the cylindrical portion which are different from each other in a cross-sectional view cut along a vertical direction;
Equipped with
A coating device in which the portion between a radially inner corner and a radially outer corner at the upper end of the cylindrical portion is flat with an upward surface . A radially inner corner and a radially outer corner at an upper end of the cylindrical portion are rounded,
2. The coating device according to claim 1, wherein a radius of curvature of a radially inner corner at the upper end of the cylindrical portion is set to be smaller than a radius of curvature of a radially outer corner at the upper end of the cylindrical portion. Using the coating device according to claim 1 or 2 ,
A first step of inserting the base material into the cylindrical portion;
a second step of pulling the substrate out of the cylindrical portion;
The coating method according to claim 1, The coating method according to claim 3 , wherein in the first step, an average ascending speed of the coating liquid rising between the radially outer surface of the substrate and the radially inner surface of the cylindrical portion is set to 50 cm/min or more. A chuck portion that supports a cylindrically formed substrate and moves in a vertical direction;
a coating tank having a cylindrical portion which is filled with a coating liquid and from which the coating liquid overflows from the top, the substrate being immersed in the cylindrical portion from above, the coating tank having a corner R dimension or C chamfer dimension of a radially inner corner at the upper end of the cylindrical portion and a corner R dimension or C chamfer dimension of a radially outer corner at the upper end of the cylindrical portion which are different from each other in a cross-sectional view cut along a vertical direction;
Using a coating device equipped with
a first step of inserting the base material into the cylindrical portion;
a second step of pulling the substrate out of the cylindrical portion;
having
The coating method, in the first step, wherein an average ascending speed of the coating liquid rising between the radially outer surface of the substrate and the radially inner surface of the cylindrical portion is set to 50 cm/min or more.