JPH1048849A - Production of electrophotographic photoreceptor and float for dip coating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ectrophotographic photoreceptor by a dip coating method capable of forming a uniform coating film free from film defects due to unevenness in concn. and to obtain a float for dip coating. SOLUTION: A body 13 to be coated is dipped in a coating soln. prepd. by dispersing particles in a coating tank, it is moved up at the required rate and a coating film is formed to produce an electrophotographic photoreceptor. In this method, a float 21 having an inverted cone-shaped structure is floated on the surface of the coating soln., and at the time of clipping the body 13 in the coating soln., the body 13, together with the float 21, is introduced into the coating soln. so that a flow of the coating soln. near the bottom of the body 13 is directed toward the surface of the wall of the coating tank.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an electrophotographic photosensitive member, and more particularly, to a method for producing an electrophotographic photosensitive member for forming a coating film by a dip coating method, and a float used for the same.

[0002]

2. Description of the Related Art A dip coating method has been widely used as a method for manufacturing an electrophotographic photosensitive member. The dip coating method is basically a method of forming a coating film by lowering an object to be coated in a coating solution, immersing the object to be applied to a position to be coated, and then raising the object. This dip coating method is an excellent method for producing a drum-shaped electrophotographic photosensitive member in terms of productivity, uniformity of film thickness, and the like.

[0003] Coating liquids have various properties. For example, some pigment-dispersed coating liquids have thixotropic properties that exhibit different viscosities due to a certain force applied to the coating liquid (eg, flow of the coating liquid, stirring). It is known that a portion having uneven viscosity is generated in a coating tank, which causes a coating film defect. To cope with such a problem, for example, Japanese Patent Application Laid-Open No. 3-62035 discloses a method in which a coating solution is applied while being vibrated. Further, for example, for a coating film defect caused by an uneven flow of a coating solution, a method of installing a rectifying cone in a coating tank has been proposed from the viewpoint of supplying a uniform flow of a coating solution. Further, a method of suppressing evaporation of the solvent vapor from the application surface is generally known for a coating film defect caused by uneven diffusion of the solvent vapor from the application tank.

[0004] However, the above-mentioned coating film defects generated in the conventional dip coating method cannot be sufficiently removed by the above method. Therefore, the conventional dip coating method still has the above-mentioned problems.

On the other hand, Japanese Patent Application Laid-Open No. 59-42067 discloses an apparatus in which a convex lid is provided below an object to be coated. In this case, handling when the object is coated is covered. There is a problem that it is not suitable for continuous production due to its poor quality.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems in the prior art, and an object of the present invention is to provide a method for producing an electrophotographic photosensitive member by a dip coating method. It is an object of the present invention to provide a method for uniformly coating a film, and in particular, to provide a method for producing an electrophotographic photoreceptor that does not cause unevenness in the density of a coating film. Another object of the present invention is to provide a dip coating float used in a method for producing an electrophotographic photosensitive member.

[0007]

In the conventional dip coating method, when the object to be coated is immersed in the coating tank, no consideration is given to the contact of the object with the coating liquid received on its surface. . On the other hand, in the process of continuous production or mass production, it is indispensable to increase the productivity by increasing the immersion speed in forming a line, but the present inventors immerse the object to be coated at a high speed. In the process, it was found that a great deal of stress was generated due to the contact between the dispersed particles in the coating solution and the object to be coated, and the effect of this stress was maintained until the coating film was formed, and the coating film defects were reduced. That is, a phenomenon in which a coating film defect occurs due to the history of the object to be coated when the object is immersed in contact with the coating liquid. Although the cause of such a phenomenon has not yet been confirmed, it is known that when the dispersed particles in the coating solution come into contact with the object to be coated, a certain repulsive force existing at the interface between the particle and the object to be coated ( For example, it is considered that the film is adsorbed by receiving an external force that exceeds an electric force such as a zeta potential), and is retained as it is until a coating film is formed, so that the portion becomes a coating film defect.

The inventors of the present invention have conducted studies based on the above findings. As a result, the present invention relaxes the contact of the object to be coated with the dispersed particles in the coating solution during immersion, thereby reducing defects in the coated film, especially unevenness in density. Defects can be removed.
The present inventors have found that the above object can be achieved by using a float having a novel structure,
The present invention has been completed.

Therefore, the present invention provides a method for producing an electrophotographic photoreceptor in which a coating liquid is formed by using a coating liquid in which particles are dispersed, dipping the coating material in a coating tank and raising the coating at a required speed. Wherein the flow of the coating liquid near the lower portion of the coating object is controlled so as to be directed toward the wall surface of the coating tank when the coating object is immersed in the coating liquid.

In a first aspect of the present invention, a float having an inverted conical structure having a thin bottom is floated on a coating liquid surface, and when the coating object is immersed in the coating liquid, the coating object is coated together with the float. The coating liquid is introduced into the coating liquid so that the flow of the coating liquid near the lower part of the coating object is directed toward the wall surface of the coating tank. In this case, it is preferable to use a float having a structure in which the outer diameter of the upper surface of the float is larger than the inner diameter of the object to be coated. According to a second aspect of the present invention, an inverted conical convex portion is provided inside a jacket whose lower side is open, and a float having an opening in a peripheral portion of an upper surface of the jacket is floated on a coating liquid level, and an object to be coated is applied. When immersing in the liquid, the object to be coated is introduced into the coating liquid together with the float,
It is characterized in that the flow of the coating liquid near the lower part of the object is directed toward the wall surface of the coating tank.

The float for dip coating of the present invention is for producing the above-mentioned electrophotographic photoreceptor, and one embodiment thereof is characterized in that it has an inverted conical structure with a thin bottom. Further, another aspect is characterized in that an inverted conical convex portion is provided inside the mantle whose lower part is open, and an opening is provided around the upper part of the mantle.

FIG. 1 is a schematic structural view of a dip coating apparatus for manufacturing an electrophotographic photosensitive member, wherein 1 is a coating tank filled with a coating liquid 6. 2 is a guide tube, 3
Is a collection tank, and 4 is a pipe, thereby forming a paint circulation channel. Reference numeral 5 denotes a circulation pump, reference numeral 7 denotes a filter, reference numeral 8 denotes a horseshoe-shaped paint guide member (see Japanese Utility Model Laid-Open No. 1-139876), and reference numeral 9 denotes a gutter for guiding a coating solution flowing from the upper portion of the coating tank. Reference numeral 10 denotes a ball screw that is rotated by a motor 11, and reference numeral 12 denotes a support member that supports an object to be coated.

[0013] Using the dip coating apparatus, the object 13
To paint the ball screw 1 by driving the motor 11
By rotating 0, the support member 12 is moved downward. As a result, the object 13 is immersed in the paint in the coating tank 1. Next, the object is pulled up at a predetermined speed to perform coating. At this time, the coating liquid 6 is supplied to the circulation pump 5
Is circulated by driving. The coating liquid is supplied from the lower part of the coating tank, flows from the upper part to the gutter 9, and is supplied again to the coating tank 1 through the guide pipe 2.

In the present invention, a conventionally known coating liquid in which particles are dispersed is used. For example, a typical example is a coating liquid for forming a charge generation layer in which a charge generation pigment is dispersed in an organic solvent containing a binder resin. Further, there may be mentioned a coating solution for forming an undercoat layer containing a fine particle, a protective layer and other layers constituting an electrophotographic photosensitive member.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, when an object to be coated is immersed in a coating liquid, the flow of the coating liquid near the lower part of the object is controlled so as to be directed toward the wall surface of the coating tank. Is used as a float. FIG. 2 is a view for explaining an example of a dip coating float of the present invention together with the state of flow of a coating liquid. Reference numeral 21 denotes a float, which has an inverted conical structure with a thin bottom, and a coating on the top. A fitting portion 22 for fitting with an object is formed. When performing dip coating, this float is floated on the coating liquid level in the coating tank of the dip coating apparatus in FIG. The dip coating is performed by lowering the object 13 to be fitted into the fitting portion 22, moving downward in that state, and introducing it into the coating liquid. At this time, the coating liquid is indicated by an arrow. As described above, since the liquid flows along the outer periphery of the float, it is possible to control the coating liquid to flow toward the wall surface of the coating tank by the float.

In the present invention, the float preferably has an inverted conical structure in which the lower portion is tapered as shown in FIG. 2, but the outer diameter of the upper portion is larger than the inner diameter of the object to be coated. It is desirable to have a structure. In that case,
It is desirable that the upper part be made as large as possible as long as the outer diameter can freely enter and exit the inner surface of the coating tank 1.

The float of the present invention may be provided with a spiral groove or a spiral ridge on its surface.
FIG. 3 shows a structure in which a plurality of spiral grooves 23 are provided on the surface of the float 21, and FIG. 4 shows a structure in which a plurality of spiral protrusions 24 are provided on the surface of the float 21.

In the inverted conical float shown in FIG. 2, there is no portion parallel to the surface of the coating liquid at the convex portion, but the float of the present invention has an inverted conical shape. However, the present invention is not limited to this, and a portion parallel to the coating liquid surface may exist.

As another specific example of the float of the present invention,
An example is a cylindrical one in which an inverted conical convex portion is provided inside the mantle whose lower part is open, and an opening is formed around the upper part of the mantle.
FIG. 5 is an example of this, in which an inverted conical convex portion 27 is provided inside a jacket 25 having a structure in which the lower portion is open, and a fitting for fitting with an object to be coated is provided at the center of the upper surface of the jacket 25. Joint part 2
2, and an opening 26 is provided in the periphery. FIG. 6 shows another example, in which a plurality of openings 26 are formed.
a, 26b and 26c are provided.

When performing the dip coating, the float is floated on the coating liquid level in the coating tank of the dip coating apparatus shown in FIG. 1, and the object 13 is lowered and fitted into the fitting portion 22.
In this state, it moves downward and is introduced into the coating solution. At that time, the coating liquid flows along the convex portion of the inverted cone provided inside the jacket of the float, and the opening 26 (or 26a to 26a to
26c) flows out of the mantle. Therefore, the coating liquid flows toward the coating tank wall surface as shown by the arrow.

In the present invention, the material of each of the floats is not particularly limited as long as it floats on the surface of the coating solution. For example, the float is made of a polyfluorinated ethylene fiber (trade name: Teflon). Is preferably used.

[0022]

EXAMPLES Examples of the present invention will be described for the case where a charge generating layer of an electrophotographic photosensitive member is formed. 87 parts by weight of granular trigonal selenium and a vinyl chloride-vinyl acetate copolymer (trade names: Solution Vinyl VMCH, Union
13 parts by weight of n-butyl acetate 200
Mix with the solution dissolved in parts by weight, and
Time-dispersed. Next, 57 parts by weight of n-butyl acetate was added to 30 parts by weight of the obtained dispersion to dilute the dispersion.
An immersion coating liquid was obtained.

The object to be coated has an outer diameter of 84 mm and an inner diameter of 82 mm.
mm, prepare an aluminum pipe with a length of 310 mm,
Using this coating liquid, dip coating was performed by using a dip coating apparatus shown in FIG. 1 and floating a Teflon structure shown in FIG. 2 as a float. That is, it was immersed at 800 mm / min and then pulled up at 100 mm / min. Then, it is heated at 100 ° C. for 5 minutes, and has a thickness of 0.1 μm.
Was formed. The obtained charge generation layer was formed of a very clean and dense coating film without shading unevenness or repelling failure.

Similarly, when the floats shown in FIGS. 3 to 6 were used, a charge generation layer composed of a very clean and dense coating film without unevenness of density and repelling failure was similarly formed.

Comparative Example A dip coating was performed in the same manner as in the example except that the float used in the above example was removed. as a result,
Coating defects, especially irregular patterns in the axial direction, caused uneven shading and cissing failures.

[0026]

The method for producing an electrophotographic photoreceptor of the present invention comprises:
With the above structure and using the float having the above structure, it is possible to reduce coating film defects that occur during conventional dip coating. That is, for example, a coating defect due to the presence of uneven viscosity in the coating tank, a coating defect due to uneven liquid flow, or a non-uniform dispersion of solvent vapor from the coating tank. The occurrence of coating film defects and the like is reduced, and a uniform and dense coating film free of these coating film defects, particularly, coating film defects relating to shading unevenness can be formed.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a dip coating apparatus used for manufacturing an electrophotographic photosensitive member.

FIG. 2 is a perspective view of one embodiment of a float for dip coating according to the present invention, illustrating a flow state of a coating liquid.

FIG. 3 is a perspective view of another embodiment of the dip coating float of the present invention.

FIG. 4 is a perspective view of another embodiment of the dip coating float of the present invention.

FIG. 5 is a perspective view of still another embodiment of the float for dip coating according to the present invention, illustrating a flow state of a coating liquid.

FIG. 6 is a perspective view of another embodiment of the dip coating float of the present invention, illustrating a flow state of a coating liquid.

[Explanation of symbols]

1 ... coating tank, 2 ... guide tube, 3 ... collection tank, 4 ... piping,
5: circulation pump, 6: coating liquid, 7: filter, 8 ...
Paint guide member, 9 gutter, 10 ball screw, 11 motor, 12 support member, 13 coated object, 21 float, 22 fitting part, 23 spiral groove, 24 spiral convex Stripe portion, 25 ... mantle, 26 ... opening, 27 ... convex portion.

Claims (6)

[Claims] In a method of manufacturing an electrophotographic photoreceptor, a coating liquid is formed by immersing an object to be coated in a coating tank at a required speed by using a coating liquid in which particles are dispersed. A method for producing an electrophotographic photoreceptor, comprising: controlling a flow of a coating solution near a lower portion of an object to be coated toward a wall surface of a coating tank when immersing the object in a coating solution. 2. A method for producing an electrophotographic photoreceptor in which an object to be coated is immersed in a coating tank and is raised at a required speed by using a coating liquid in which particles are dispersed. A float with a thin inverted cone structure is floated on the surface of the coating liquid, and when the object to be coated is immersed in the coating liquid, the object to be coated is introduced together with the float into the coating liquid. 2. The method according to claim 1, wherein the flow is directed toward the wall surface of the coating tank. 3. The method for producing an electrophotographic photosensitive member according to claim 2, wherein a float having a structure in which the outer diameter of the upper surface of the float is larger than the inner diameter of the object to be coated is used. 4. A method of manufacturing an electrophotographic photoreceptor in which an object to be coated is immersed in a coating tank and raised at a required speed by using a coating liquid in which particles are dispersed, thereby forming a coating film. An inverted conical convex portion is provided inside the open mantle, a float having an opening at the periphery of the upper surface of the mantle is floated on the coating liquid surface, and when the object is immersed in the coating solution, the object is coated. 2. The method for producing an electrophotographic photoreceptor according to claim 1, wherein the flow of the coating liquid near the lower portion of the object to be coated is directed toward the wall surface of the coating tank by introducing the coating liquid together with the float. 5. A dip coating float for producing an electrophotographic photosensitive member, characterized by having an inverted conical structure with a thin bottom. 6. A dip coating float for producing an electrophotographic photoreceptor, wherein an inverted conical convex portion is provided inside a mantle whose lower part is open, and an opening is formed in a peripheral part of an upper surface of the mantle.