JPH05337430A - Method for forming photosensitive layer of electrophotographic photoreceptor - Google Patents

Abstract

(57) [Abstract] [Purpose] To reduce the unevenness of the coating film that occurs when the substrate is pulled up from the coating liquid when the coating film is formed on the cylindrical photosensitive conductive substrate by the dipping method. [Structure] A coating liquid 2 flowing out of a storage tank 4 is made to flow into a dipping tank 1 so as to be constantly overflowed, and a cylindrical conductive substrate 11 which is vertically movable is dipped in the dipping tank 1 to form a coating film. The height dimension of the vapor layer 12 of the solvent generated on the liquid surface of the dipping tank 1 during formation is set to 30 mm or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a coating film by coating a coating liquid on the surface of a cylindrical conductive substrate of an electrophotographic photoreceptor.

[0002]

2. Description of the Related Art A photosensitive member is formed by processing a metal having good conductivity such as aluminum into a cylindrical shape to form a base, and a photoconductive material is formed on the surface of the conductive cylindrical base (hereinafter simply referred to as "base"). Is produced. In this case, as the photoconductive material, an inorganic material such as cadmium sulfide, amorphous selenium, selenium arsenic, and zinc oxide, an organic material such as polyvinylcarbazole, and phthalocyanine are used alone or in a form dispersed in a resin, and this material is used as a base material. A layer is formed on the surface.

Generally, coating is applied to the film formation on the surface of an object,
Typical methods include brush painting and spray gun spraying. Such a coating method is effective for obtaining a coating film having a coating film thickness of, for example, about 10 μm or more. That is, it is often desirable to have a rather thick coating film, such as a coating film containing a pigment for hiding the base color of the coating object or a film for rust prevention of the coating object, It is a very effective method for forming a coating film in such a case.

However, in recent years, thinner coatings have been required in the photosensitive layer of the electrophotographic photosensitive member and the flux coating of the printed circuit board as compared with the prior art. Further, such a coating film is required to have uniform functions on the substrate, but since it is made thinner, even a slight variation in film thickness, which has not been a problem in the past, can significantly increase its function. It will lead to a decline.
Therefore, the conventional brush coating and spray coating with a spray gun cannot be applied, and the spin coating method or the dipping method that can obtain a uniform film thickness is mainly used. However, the spin coating method requires a high-speed rotation drive mechanism for the apparatus, and coating is difficult or even impossible when the surface area of the substrate on which the coating film is formed is large or the surface shape is complicated. The dipping method is widely adopted.

In the dipping method, a functional material (eg, cadmium sulfide, zinc oxide, etc.) is dissolved or dispersed in an organic solvent (eg, polycarbonate resin, polyester resin, etc.) and, if necessary, an adhesive, a plasticizer, etc. are added. A coating liquid is formed, the coating liquid is stored in a liquid tank, and the substrate is immersed in the coating liquid in the liquid tank.
Next, after pulling up the substrate from the liquid tank, the coating liquid adhering to the substrate surface is dried to form a coating film. This dipping method is simple, and a thin film can be obtained relatively easily by adjusting the viscosity of the coating liquid and the speed at which the substrate is pulled up from the coating liquid.

FIG. 1 shows a coating apparatus used for forming a coating film on the surface of a substrate of a photoreceptor by a dipping method, which comprises a dipping tank 1, a storage tank 4, a pump 5 and the like, and the dipping tank 1 always overflows. The coating liquid 2 is filled in a state, and the coating liquid 2 overflowing from the dipping tank 1 is stored in a doughnut-shaped pan 1A surrounding the outer periphery of the dipping tank 1 through a pipe 3A connected in communication with the pan 1A. I am trying to flow into 4. A cover lid 3B having a hole 1C through which the substrate 1 can be inserted is detachably attached to the opening of the tray 1A. The coating liquid 2 in the storage tank 4 flows through the pipe 3C by the drive of the pump 5 connected to the pipe 3B, flows into the dipping tank 1, and is constantly circulated so that the coating liquid 2 overflows from the dipping tank 1 The liquid level in the tank 1 is kept constant. An elevator 8 is attached to a guide rail 7 vertically planted on the base 6, and a base holder 10 is attached to the tip of an arm 9 extending horizontally from the elevator 8. One end of the base 11 is held by the base holder 10 and is lowered in the direction of the thick arrow P by the vertical movement of the elevator 8 to be immersed in the coating liquid 2 through the hole 1C of the cover 1B and in the direction of the thick arrow Q. To rise from the coating liquid 2. 2 is a detailed view of a portion indicated by an arrow R in FIG.
What is shown by 2 is a vapor layer of the organic solvent of the coating liquid 2.

[0007]

In the process of dipping a substrate having an outer diameter larger than 60 mmΦ into the coating solution in the dipping tank by the dipping method using the above-mentioned coating apparatus, and then pulling it out of the coating solution, the surface of the substrate is When the coating liquid is released, the surface temperature of the substrate is rapidly lowered due to the effect of the latent heat of vaporization of the solvent in the coating liquid. For this reason, when the coating film applied to the surface of the substrate away from the coating liquid passes through the vapor layer, the solvent there is not evaporated, and the coating film flows in the direction of gravity (downward), with respect to the pulling direction of the substrate. There is a problem that the coating film becomes uneven.

The object of the present invention is to solve the above problems.
It is to suppress the unevenness of the coating film caused by the effect of a sudden temperature drop due to the latent heat of vaporization of the solvent generated when the substrate is pulled up from the coating liquid.

[0009]

According to the present invention, a cylindrical conductive substrate is immersed in a dipping tank filled with a coating solution for forming a photosensitive layer so that the coating solution is constantly overflowing, and then the conductive substrate is pulled out from the dipping tank. In the method of forming a coating film for the photosensitive layer on the surface of the conductive substrate by drying the surface, the height of the vapor layer of the solvent in the coating solution generated on the liquid surface of the dipping tank is set to 30 mm or less. More specifically, the coating film is formed using a dipping tank having a depth of 30 mm or less, which is covered with an upper surface of a pan surrounding the outer periphery of the dipping tank and has a hole into which a conductive substrate can be inserted. Polyester resin 1: dichloromethane as a coating solution X in a solution having a weight ratio of 100
Type mixed metal-free phthalocyanine is used, and the conductive substrate is filled with this coating solution and dipped in a dipping tank for 10 mm / s.
The CG layer (charge generation layer) is formed on the surface of the conductive substrate by pulling up from the dipping bath at a constant rate of ec, and the CT layer (charge transport layer) formed on the CG layer (charge generation layer)
Is a mixed solution having a weight ratio of hydrazone derivative 1: polycarbonate resin 1: dichloromethane 9 as a coating solution, and the conductive substrate is dipped in the dipping tank filled with this coating solution, and then, at a constant speed of 2 mm / sec. Pull up to form.

[0010]

According to the method for forming the photosensitive layer of the electrophotographic photosensitive member according to the present invention, the dipping method is performed by setting the height of the vapor layer of the solvent in the coating solution generated on the upper surface of the dipping tank to 30 mm or less. In the process of pulling up the substrate immersed in the coating liquid, even if the temperature of the substrate surface suddenly drops due to the latent heat of vaporization of the solvent, the distance and time for passing through the vapor layer are short, so there are few parts where the solvent does not evaporate. The unevenness of the coating film does not occur in the lifting direction of the substrate.

[0011]

EXAMPLE In this example, the coating apparatus shown in FIGS. 1 and 2 described above is used. When the CG layer (charge generation layer) is formed on the surface of the substrate 11, as the coating liquid 2, a solution having a weight ratio of polyester resin 1: dichloromethane 100 mixed and dispersed with X-type metal-free fucocyanine is used. To do. The substrate 11 of 78Φ × 340L is attached to the substrate holder 10, and the elevator 8 is driven to lower the substrate 11 to immerse it in the coating solution 2 in the dipping tank 1. Next, when pulling up the substrate 11 to which the coating liquid 2 is attached, the elevator 8 is driven again to raise the substrate 11 at a constant speed of 10 mm / sec. The base 11 is removed from the base holder 10, and the base 11 is dried by a dryer (not shown).

When the CT layer (charge transport layer) is formed on the substrate 11 on which the CG layer (charge generation layer) is formed, the structure shown in FIG.
A separate coating apparatus shown in FIG. 2 is used, and as the coating liquid 2 at that time, a mixed solution having a weight ratio of hydrazone derivative: polycarbonate resin 1: dichloromethane 9 is used. The dipping and pulling-up operations of the base 11 are the same as those described above, so the description thereof is omitted.
The constant speed is mm / sec. The total thickness of the substrate 11 on which the CG layer (charge generation layer) and CT layer (charge transport layer) were formed in this manner was set to 20 μm.

[0013]

The photoconductor substrate formed by the above method while changing the height dimension of the vapor layer 12 of the coating apparatus is irradiated with the lightness deviation of the CG layer due to the axial thickness deviation of the CG layer and the laser light source. When the light potential deviation and the image density deviation due to the actual image were obtained, the results shown in the following table were obtained.

[0014]

[Table 1] As a result, it was found that no image deviation occurred when the height of the vapor layer of the solvent in the coating liquid generated on the liquid surface of the dipping tank was 30 mm or less. In addition, in order to reduce the vapor layer to 30 mm or less, a cover lid having a depth of 30 mm or less may be used.

[Brief description of drawings]

FIG. 1 is a front view of a coating device that forms a coating film on a photoreceptor substrate by a dipping method.

FIG. 2 is a detailed view of a portion viewed from an arrow R in FIG.

[Explanation of symbols]

 1 Immersion Tank 1A Sauce 1B Cover Lid 1C Hole 2 Coating Liquid 4 Storage Tank 12 Vapor Layer

Claims (4)

[Claims] 1. A cylindrical conductive substrate is dipped in a dipping tank filled with a coating solution for forming a photosensitive layer so as to always overflow, and then the conductive substrate is pulled out of the dipping tank and its surface is dried. In the method for forming a coating of a photosensitive layer on the surface of a conductive substrate, the height dimension of the vapor layer of the solvent in the coating liquid generated on the liquid surface of the dipping tank is set to 30 mm or less. Method for forming photosensitive layer of body. 2. The immersion tank according to claim 1, wherein the depth of the cover lid having a hole for covering the upper surface of the pan surrounding the outer periphery of the immersion tank and into which the conductive substrate can be inserted is 30 mm or less. A method for forming a photosensitive layer of an electrophotographic photoreceptor, which comprises forming a coating film. 3. The coating solution according to claim 1, wherein an X type metal-free phthalocyanine is mixed in a solution having a weight ratio of polyester resin 1: dichloromethane 100 as a coating solution, and the conductive substrate is used as the coating solution. And forming a CG layer (charge generating layer) on the surface of the conductive substrate by immersing the film in the dipping bath and then pulling it up from the dipping bath at a constant rate of 10 mm / sec. Membrane method. 4. The method according to claim 3, wherein a mixed solution having a weight ratio of hydrazone derivative 1: polycarbonate resin 1: dichloromethane 9 is used as a coating solution, and the conductive substrate is placed in a dipping tank filled with the coating solution. 2mm / s after immersion
A method for forming a photosensitive layer of an electrophotographic photosensitive member, which comprises pulling up from a dipping bath at a constant rate of ec to form a CT layer (charge transport layer) on a CG layer (charge generation layer).