JPH05337417A - Dip coating device for manufacturing electrophotographic receptor - Google Patents

Abstract

PURPOSE:To provide a dip coating device to produce an electrophotographic receptor having a uniform coating film without uneven density. CONSTITUTION:The dip coating device for manufacturing the electrophotographic receptor is provided with a coating liquid circulating device having a coating tank 2 having a receiving dish 3 at the upper part, a coating liquid storage 5 and a pump 6 and an elevator device of a material 1 to be coated, and the coating liquid is circulated and while allowing the coating liquid to, dip coating is performed. The coating tank 2 has a circular cross section and the upper a part inside diameter of the coating tank is larger than the lower part inside diameter of that and also the tank 2 has a shape in which the cross section area of the tank 2 decreases continuously from the upper part to the lower part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dip coating apparatus for producing an electrophotographic photosensitive member by using a coating liquid in which particles are dispersed.

[0002]

2. Description of the Related Art Hitherto, in order to manufacture an electrophotographic photosensitive member, a dip coating method using a dip coating apparatus has been widely practiced. This method is basically used for coating an object to be coated in a coating liquid. Is a method in which the material to be coated is dipped to the point where it is desired to be coated, and is then raised to perform coating. This dip coating method is a method excellent in productivity, film thickness uniformity, and the like as a method for producing a drum-shaped photoreceptor. However, in the dip coating method, a coating film defect may occur due to various causes. For example,
When a low-viscosity coating liquid is used, the coating liquid is easily affected by the surrounding vibration, and the fluctuation of the liquid surface causes the portion to be overcoated, resulting in a local thick film portion. In order to improve the occurrence of such coating film defects, it is sufficient to provide equipment for reducing the vibration of the surroundings, but in continuous production, this is not an appropriate method in terms of cost. On the other hand, in order to reduce the influence of vibration, it is possible to enlarge the entire coating tank portion, but in that case, there is a problem in that the coating liquid is required for the increased volume.

In order to deal with such a problem, for example, as shown in FIG. 2, the area of the inner diameter of the upper part of the coating tank is
It has been proposed to make it larger than the area of the inner diameter of the lower part. In FIG. 2, reference numeral 1 denotes an object to be coated such as an aluminum pipe, the upper part of which is connected to a lifting device (not shown). Reference numeral 2 denotes a coating tank for dipping and coating an object to be coated, and a tray 3 for collecting the overflowed coating liquid is provided on the upper portion thereof. The collected coating liquid passes through the pipe 4 and is poured into the coating liquid reservoir 5. The coating liquid collected in the coating liquid reservoir 5 is applied to the coating tank 2 by the pump 6.
Is supplied to. A filter 7 is provided to remove dust and the like. In the above dip coating apparatus, the inner diameter of the upper portion of the coating tank is larger than the inner diameter of the lower portion thereof, whereby the influence of vibration can be reduced.

[0004]

However, in the above-mentioned conventional dip coating apparatus, as a secondary obstacle due to making the inner diameter of the upper part larger than the inner diameter of the lower part, coating defects, especially uneven distribution of particles in the coating, are caused. (Hereinafter, it is referred to as uneven density.) The cause of this phenomenon is not yet clear, but when the particles in the coating solution come into contact with the object to be coated, a certain repulsive force (for example, an electric potential such as a zeta potential) existing at the interface between the particle and the object to be coated. It is considered that an external force that exceeds the target force) causes the film to be adsorbed, and that state is maintained until a coating film is formed, so that the portion becomes a coating film defect. That is, for example, in the coating layer having the shape as shown in FIG. 2, when the coating liquid circulates, turbulent flow occurs at a portion where the area of the coating layer changes from the area of the inner diameter to the area of the outer diameter. It is considered that this is because the force due to the contact between the object to be coated and the particles when the object is immersed increases. The present invention is intended to solve the above-mentioned problems in the conventional technique. That is, an object of the present invention is to provide a dip coating apparatus capable of producing an electrophotographic photosensitive member having a uniform coating film with no unevenness in density.

[0005]

Means for Solving the Problems As a result of diligent research on the effect of the generation of the uneven density occurring in conventional dip coating, the present inventors have found that, as described above, It was discovered that the effect of the contact between the particles and the object to be coated is maintained until the coating film is formed as it is, and a coating film defect occurs due to the history of the object to be coated due to the contact with the coating liquid during dipping. Then, by relaxing the contact between the article and the particles during immersion,
It has been found that this kind of shade unevenness can be eliminated, and the present invention has been completed.

That is, the dip coating apparatus for producing an electrophotographic photosensitive member of the present invention comprises a coating tank having a pan on the top, a coating solution circulating apparatus having a coating solution reservoir and a pump, and a lifting device for an object to be coated. The coating solution is circulated, and immersion coating is performed while causing the coating solution to overflow.
The cross-section is circular, the inner diameter of the upper part of the coating tank is larger than the inner diameter of the lower part, and the cross-sectional area of the cross-section continuously decreases from the upper part to the lower part. In the dip coating apparatus of the present invention, the structure in which the cross-sectional area of the cross section of the coating tank continuously decreases from the upper portion to the lower portion is not particularly limited, but the angle inclined from the upper portion to the lower portion is not limited. , 60 vertically
Those having a structure such that the angle is less than or equal to °, preferably less than or equal to 20 ° are used.

As a coating liquid for dispersing particles for forming a photosensitive layer used in the dip coating apparatus of the present invention, fine powder of photoconductive material is dispersed in an organic solvent solution of a binder resin. As the photoconductive material in the dispersion liquid, any known organic pigment and inorganic pigment can be used.

[0008]

When an electrophotographic photosensitive member is manufactured by the dip coating device of the present invention, the object to be coated supported by the elevating device is dipped in the coating solution in the coating tank and then pulled up to be placed on the object to be coated. The film of the photosensitive layer is formed. At that time, the coating liquid overflows from the upper end of the coating tank, is collected in a tray, and is collected in a coating liquid reservoir. The recovered coating liquid is returned to the coating tank by driving the pump. In the present invention, the coating tank has a structure in which its cross-sectional area continuously decreases from the upper portion to the lower portion, so that when the article to be coated is dipped, the flow of the coating liquid becomes uniform, The contact between the object to be coated and the particles in the coating solution is relaxed. And
The history that the object to be coated during the immersion is violently contacted with the coating solution, and the history of the coating film being formed on the object to be coated by the object being maintained even after the object is lifted up, in particular, defects such as uneven density. Will be of good quality.

[0009]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of an embodiment of the dip coating device of the present invention. In the figure, 2 is a coating tank for dip coating an aluminum pipe which is a substrate, and the inside is filled with a coating liquid. A receiving tray 3 for collecting the overflowing coating liquid is provided above the coating tank 2, and a pipe 4 communicating with a coating liquid reservoir 5 is provided below the receiving tray. The lower part of the coating tank 2 and the lower part of the coating liquid reservoir 5 communicate with each other by piping, and the coating liquid is pumped by a pump 6 to a filter 7
It is designed to be circulated to the coating tank via. The coating bath has a circular cross section, and as shown in the figure, its upper inner diameter is larger than its lower inner diameter, and its cross-sectional area continuously decreases from the upper part to the lower part. , Is formed from a bath wall that is inclined with a gentle curve. On the other hand, the aluminum pipe 1, which is the object to be coated, is supported by a lifting device so as to be lifted and lowered. That is, the upper portion is supported by the supporting device 8 and can be moved up and down by the ball screw 9. Reference numeral 10 is a motor for driving the ball screw.

The case of producing an electrophotographic photosensitive member using the above dip coating device will be described. The motor 10 is driven to rotate the ball screw 9 and the aluminum pipe 1 supported by the supporting device 8 is applied to the coating tank. Immerse in the coating liquid inside. The coating liquid is circulated by driving the pump 6. That is, the coating liquid overflowing from the upper end of the coating tank 2 and collected in the tray 3 flows down the pipe 4 and is collected in the coating liquid reservoir 5. The recovered coating liquid is circulated by the pump 6 and supplied to the lower part of the coating tank.

Next, more specific examples and comparative examples will be shown. Examples 1 to 8 Using the coating liquid A and the coating liquid B prepared as described below, a coating film was formed on the aluminum pipe (φ80 mm × length 360 mm) as the substrate by the dip coating device shown in FIG. Formed. In that case, the inner diameter of the upper part and the inner diameter of the lower part of the coating tank were changed to various ones shown in Table 1 for coating. The dip coating conditions were as follows. Depth of coating liquid in coating tank: 500 mm Immersion speed of aluminum pipe: 800 mm / min Supply amount of coating liquid: 4000 cm ³ / min Ascending speed of aluminum pipe: 200 mm / min

Coating liquid A: dibromoanthanthrone 10
By weight, 1 part by weight of polyvinyl butyral, 0.02 part by weight of trifluoroacetic acid, 0.06 part by weight of hydrochloric acid and 90 parts by weight of cyclohexanone were dispersed to prepare a coating solution. Coating liquid B: 87 parts by weight of granular trigonal selenium and 13 parts by weight of vinyl chloride-vinyl acetate copolymer (trade name: Solution Vinyl VMCH, manufactured by Union Carbide) to 200 parts by weight of n-butyl acetate. The dissolved solution,
It was dispersed for 24 hours with an attritor. Next, to 30 parts by weight of the obtained dispersion liquid, 57 parts by weight of n-butyl acetate was added and diluted to form a coating liquid.

Comparative Examples 1 to 8 Aluminum pipes were subjected to dip coating under the same conditions as in the above-mentioned examples except that the dip coating device having the coating tank having the structure shown in FIG. 2 was used. The coating tank in FIG. 2 has an upper inner diameter larger than that of the lower inner diameter.
It has a shape with a step on the bath wall. In these comparative examples, the inner diameter of the upper part and the inner diameter of the lower part of the coating tank are shown in Table 1.
Dipping coating was performed by changing to various types shown in. As a result, the formed coating films all had coating film defects, particularly severe unevenness of light and shade.

Comparative Examples 9 to 12 Using an immersion coating apparatus having a coating tank having the structure shown in FIG. 3, an aluminum pipe was subjected to immersion coating under the same conditions as in the above-mentioned Examples. The coating tank 2 in FIG. 3 had the same inner diameter from the upper part to the lower part. In addition,
In the figure, the reference numerals mean the same as in FIG. As a result, the formed coating films all had defects in the shape of unevenness in density in the circumferential direction, particularly unevenness in steps.

The coating liquids in the above Examples and Comparative Examples,
The inner diameter of the coating tank and the state of the coating film are summarized in Table 1 below.

[0016]

[Table 1]

[0017]

As described above, in the dip coating apparatus of the present invention, the coating tank has a circular cross section, the inner diameter of the upper part is larger than the inner diameter of the lower part, and the cross-sectional area of the cross section is from the upper part to the lower part. Since it has a shape that decreases continuously as it reaches, when the object to be coated is immersed in the coating liquid, the flow of the coating liquid becomes uniform, and the fluctuation of the liquid surface also decreases, so that the coating film It is possible to produce an electrophotographic photosensitive member having a photosensitive layer of good quality without defects and uneven density.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of a dip coating device of the present invention.

FIG. 2 is a schematic configuration diagram of a main part of an example of a conventional dip coating device.

FIG. 3 is a schematic configuration diagram of a main part of another example of a conventional dip coating device.

[Explanation of symbols]

1 ... Aluminum pipe, 2 ... Coating tank, 3 ... Sauce, 4 ...
Piping, 5 ... Coating liquid reservoir, 6 ... Pump, 7 ... Filter, 8
... Supporting device, 9 ... Ball screw, 10 ... Motor.

Claims (1)

[Claims] 1. An electronic device comprising: a coating tank having a saucer on the upper portion thereof; a coating liquid circulating device having a coating liquid reservoir and a pump; and an elevating device for an object to be coated, which circulates the coating liquid and performs dip coating while overflowing. In a dip coating apparatus for producing a photographic photoreceptor, the coating tank has a circular cross section, the inner diameter of the upper portion of the coating tank is larger than the inner diameter of the lower portion, and the cross-sectional area of the cross section continuously increases from the upper portion to the lower portion. And a dip coating apparatus for producing an electrophotographic photosensitive member using a coating liquid in which particles are dispersed.