JPH07110584A - Coating device - Google Patents

Abstract

PURPOSE:To form a uniform photosensitive layer without causing nonuniform coating by lowering the surface of a coating soln. below the opening of a coating tank after the dipping of a conductive substrate is finished and then starting coating. CONSTITUTION:This device consists of the surface 1 of a coating soln., a coating tank 2, the opening 3 of the coating tank, an overflow receiving tank 4, a coating soln. return port 5, a coating soln. feed port 6 and a conductive substrate 7, the surface 1 is lowered below the opening 3 at the time of starting coating, then the substrate 7 is extracted, and a charge generating layer is provided on the substrate 7. A coating soln. for a charge-transfer layer prepared by mixing one pts.wt. of a hydrazone compd. and 8 pts.wt. of dichloromethane, agitating and dissolving the mixture is applied by dip coating in the same way as the charge generating layer to provide a charge-transfer layer and dried with hot air to form a functionally separated electrophotographic photoreceptor. Since the photosensitive layer is formed after the liq. surface is stabilized in this way, a coating film defect such as annular nonuniformity and nonuniform coating is prevented, and a good picture characteristic is attained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION An electrophotographic copying machine is manufactured by coating a photosensitive material on the peripheral surface of its substrate.
The present invention relates to a coating device for carrying out the dipping coating method.

[0002]

2. Description of the Related Art Electrophotographic photoreceptors currently in practical use can be roughly classified into those using an inorganic material and those using an organic material. As a typical photoreceptor of inorganic material,
Selenium compounds such as amorphous selenium (a-Se) and amorphous selenium arsenic (a-As ₂ Se ₃ ), dye-sensitized zinc oxide (ZnO), or cadmium sulfide (C
Examples thereof include those in which dS) is dispersed in a binder resin, those in which amorphous silicon (a-Si) is used, and the like.
In addition, as typical photoreceptors of organic materials, 2, 4,
7-Trinitro-9-fluorenone (TNF) and Pori-
Examples thereof include those using a charge transfer complex with N-vinylcarbazole (PVK). These inorganic photoconductors have many advantages and at the same time have drawbacks. For example, a photoreceptor using selenium and CdS has problems in heat resistance and storage stability, and has a limitation that it cannot be easily discarded because it has toxicity and must be recovered. ZnO resin-dispersed photoreceptors are now almost obsolete because of their low sensitivity and lack of durability. Further, although the a-Si photoconductor has excellent advantages such as high sensitivity and high durability, it has a high manufacturing cost due to the complexity of its manufacturing process and image defects due to defects during film formation. Is left with the problem. On the other hand, organic photoreceptors have various organic materials scattered therein and can be arranged in various ways by synthesis. Therefore, by appropriately selecting them, problems such as storage stability and toxicity can be avoided. Further, since it can be manufactured at low cost, it has been extensively studied in a wide range. However, the organic photoconductor also has a problem of low sensitivity, and its improvement is being promoted. The PVK-TNF charge transfer complex described above was one of the improvements, but it did not reach sufficient sensitivity.

Therefore, various other sensitizing methods have been proposed, for example, a layer containing a substance (hereinafter referred to as "charge generating substance") that generates charge carriers when irradiated with light (hereinafter referred to as "charge generating layer"). And a layer mainly composed of a substance (hereinafter referred to as “charge transport substance”) that receives and transports the charge carriers generated in the charge generation layer (hereinafter referred to as “charge transport layer”). Type photoconductors (hereinafter referred to as "function-separated type photoconductors") exhibit excellent sensitization properties, and thus have occupied most of the organic photoconductor structures currently in practical use. Further, it is expected to be the mainstream of photoconductors in the future due to the improvement of durability.

As the conductive substrate in the present invention, a substrate having conductivity itself, for example, aluminum, aluminum alloy, copper, zinc, stainless steel, nickel, titanium, etc. can be used. In addition, aluminum, aluminum alloy, It is possible to use plastic or paper on which indium oxide, tin oxide, or the like is vapor-deposited or applied, plastic or paper containing conductive particles, plastic having conductive polymer, or the like. A charge generation layer is formed on the conductive substrate, and as the charge generation substance used for the charge generation layer, a bisazo compound such as chlorodian blue, a polycyclic quinone compound such as dibromoanthanethrone, Perylene-based compounds, quinacridone-based compounds, phthalocyanine-based compounds, azurenium salt-based compounds and the like can be used. As a method for forming the charge generation layer, there are a method of directly forming a compound by vacuum vapor deposition and a method of dispersing in a binder resin solution and coating to form a film, but the latter method is generally preferable. The thickness of the charge generation layer is 0.05 to 5 μm.
m, preferably 0.1 to 1 μm. In the case of production by coating, as a method of mixing and dispersing the charge generating substance in the binder resin solution, there are a ball mill, a side mill, an attritor, a vibration mill, an ultrasonic disperser and the like. Examples of the binder resin for the binder resin solution include melamine resin, epoxy resin, silicone resin, polyurethane resin, acrylic resin, vinyl chloride, vinyl acetate copolymer resin, polycarbonate resin, phenoquine resin, and the like. As the solvent for dissolving the resin, acetone, methyl ethyl kent, ketones such as cyclohexanone, esters such as ethyl acetate and butyl acetate, ethers such as tetrahydrofuran and dioxane, aromatic hydrocarbons such as benzene, toluene and xylene. , N, N-dimethylformamide,
An aprotic polar solvent such as dimethyl sulfoxide can be used. Examples of the charge transport material of the charge transport layer provided on the charge generation layer include hydrazone compounds, pyrazoline compounds, triphenylamine compounds, triphenylmethane compounds, stilbene compounds, oxadiazole compounds, etc. Can be used, and the charge transporting coating liquid is prepared by dissolving the charge transporting substance in the binder resin solution. This charge transport layer can be formed by the above-mentioned coating method. The thickness of the charge transport layer is 5 to
50 μm, preferably 10 to 40 μm. Further, a layer called an undercoat layer may be provided between the conductive substrate and the photosensitive layer for the purpose of improving the characteristics.

As a method for producing an electrophotographic photosensitive member using the above organic material, a conductive substrate is dipped in a coating solution containing a photosensitive substance as described in JP-A-57-5047, and then, A dip coating method is known in which the substrate is drawn out of the coating solution to form a photosensitive layer on the substrate, and it is a mainstream method for producing an organic photoreceptor because it is simple in terms of equipment and excellent in productivity. ing.

[0006]

In the case of the conventional dip coating, it is necessary to provide an overflow device in order to prevent the precipitation of the coating solution and to keep the dipping length of the conductive substrate constant. However, in the case of overflow coating, uneven coating occurs due to the turbulent flow of the coating liquid during coating while overflowing. Therefore, in order to satisfy the above conditions, a method of overflowing only when the substrate is immersed and stopping the overflow during coating can be considered. However, according to this method, the coating film unevenness due to the turbulent flow of the coating solution can be eliminated, but there is a problem that ring-shaped unevenness occurs at the start of coating. This ring-shaped unevenness is such that when the substrate is immersed and the overflow is stopped, the surface tension of the coating liquid causes the liquid level of the coating liquid to be higher than the opening of the coating tank and the coating liquid to rise. This rising state of the liquid level is the most unstable state of the coating liquid, and when the coating is started next time, the liquid level fluctuates at the place where the liquid level rises, which causes ring-shaped unevenness at the start of coating. Occurs.

[0007]

SUMMARY OF THE INVENTION The present invention has been made for the purpose of solving the above-mentioned problems, and a coating apparatus according to claim 1 immerses a conductive substrate in a coating tank filled with a coating solution to perform coating. In a coating device for forming a photosensitive layer by drawing out the conductive substrate after overflowing the liquid, means for lowering the liquid level of the coating liquid from the opening of the coating tank at the end of immersion of the conductive substrate, and the liquid level by the means. The coating device is characterized in that the coating is started after lowering.

The coating apparatus according to a second aspect is the coating apparatus according to the first aspect, wherein the means for lowering the liquid level is to lower the coating liquid level by pulling out the conductive substrate.

A coating apparatus according to a third aspect of the invention is characterized in that the conductive substrate is pulled out after a predetermined time has elapsed after lowering the coating liquid surface, and a photosensitive layer is formed on the conductive substrate. It is the coating device described.

[0010]

According to the first aspect, since the photosensitive layer is formed after releasing the unstable state of the liquid surface, it is possible to form a uniform photosensitive layer without causing coating unevenness.

According to the second aspect, no special function is required as means for lowering the liquid level, and the problem can be solved without modifying the conventional coating device.

According to the third aspect, since the photosensitive layer is formed after the liquid surface of the coating liquid is stabilized, a further effect can be exerted in suppressing uneven coating, and a more uniform photosensitive member can be formed.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings, but the present invention is not limited to the following embodiments unless the gist thereof is exceeded.

Example 1 FIG. 1 is a schematic cross-sectional view showing the liquid level of the coating liquid at the time when the immersion overflow of the conductive substrate is completed. In FIG. 1, 1 is the liquid level of the coating liquid, 2 is a coating tank, and 3 Is the coating tank opening,
4 is an overflow receiving tank, 5 is a coating liquid return port, 6 is a coating liquid supply port, and 7 is a conductive substrate.

FIG. 2 is a schematic sectional view showing a state in which the liquid level of the coating liquid at the start of coating is lowered from the opening of the coating tank.

In a coating tank as shown in FIGS. 1 and 2, for example, 1.5 parts by weight of a bisazo pigment (chlorodian blue) represented by the following structural formula (Formula 1) and butyral resin (manufactured by Union Carbide Co .: XYGS) 1. A mixture of 5 parts by weight and 97 parts by weight of methyl isobutyl kent was dispersed with a paint shaker for 8 hours to fill the prepared charge generation layer coating liquid,
Next, a cylindrical conductive base made of aluminum, whose upper end is hermetically held, is immersed in the coating tank to overflow the coating liquid. Immersion is stopped when the substrate reaches the desired depth. At this point, the liquid level of the coating liquid is at the water level as shown in FIG. 1, and then the substrate is slightly pulled out so that the liquid level of the coating liquid becomes as shown in FIG. At this time, the distance from the coating tank opening to the liquid surface is 1 mm. After lowering the liquid level, the substrate was pulled out and a charge generation layer was provided on the conductive substrate. Furthermore, a hydrazone compound (4, -diethylaminobenzaldehyde-N,
A mixture of 1 part by weight of N-diphenyl bidrazone), 1 part by weight of a polycarbonate resin (Mitsubishi Gas Chemical Co., Inc .: Iupilon) and 8 parts by weight of dichloromethane was dissolved by stirring.
The prepared charge transport layer coating solution is applied by dip coating in the same manner as for the charge generation layer to form a charge transport layer, and hot air drying is performed for 1 hour at a drying temperature of 80 ° C. to obtain a dry film thickness of 20 μm. An electrophotographic photoreceptor was produced. The electrophotographic photosensitive member produced in this manner has no coating defects such as ring-shaped unevenness and coating unevenness, and the actual device (manufactured by Sharp Corporation: SF: 810).
Good image characteristics were also obtained in the actual copying test according to 0).

[0017]

[Chemical 1]

[0018]

[Chemical 2]

Example 2 In contrast to Example 1 in which the conductive substrate was slightly drawn out and the liquid level of the coating liquid was lowered from the opening of the coating tank, a small amount of the coating liquid was drained from the supply port to lower the liquid level. Was subjected to dip coating in the same manner as in Example 1 to produce a function-separated electrophotographic photosensitive member. In this case as well, the appearance inspection and actual copying test of the photoconductor were performed in the same manner as in Example 1, but good image characteristics were obtained without coating film defects.

Example 3 The coating solution used in Example 1 was filled in the coating tank, the conductive substrate was immersed in the coating tank, the surface of the coating solution was lowered by 2 mm from the opening of the coating tank, and then stopped for about 10 seconds. Then, the function-separated electrophotographic photosensitive member was produced by the procedure of starting the coating after the coating liquid surface was completely stabilized. In this case as well, the appearance inspection and actual copying test of the photosensitive member were performed in the same manner as in Example 1, but good image characteristics were obtained without coating film defects.

Comparative Example 1 The conductive substrate obtained in Example 1 was slightly pulled out, and the liquid level of the coating liquid was lowered from the opening of the coating tank, while the liquid level was not lowered and coating was performed from the state shown in FIG. Then, a function-separated electrophotographic photosensitive member was produced. Also in this case, the appearance inspection and the actual copying test of the photoconductor were carried out in the same manner as in Example 1, and the fluctuation of the coating liquid occurred at the start of the coating, which caused the ring-shaped unevenness on the upper part of the photoconductor, which was excellent. Image characteristics were not obtained.

Comparative Example 2 Whereas the conductive substrate obtained in Example 1 was slightly pulled out and the liquid level of the coating liquid was lowered by 1 mm from the opening of the coating tank, the liquid level was lowered by 6 mm from the opening of the coating tank. Except for this, dip coating was performed in the same manner as in Example 1 to prepare a function-separated electrophotographic photosensitive member. In this case as well, when the appearance inspection and the actual copying test of the photosensitive member were carried out in the same manner as in Example 1, the film thickness in the image area portion on the upper portion of the photosensitive member became thin and an image defect occurred.

Comparative Example 3 In the same manner as in Example 3, except that the coating liquid surface was lowered by 2 mm and stopped for about 10 seconds to start coating in Example 3, but the stop time was changed to 60 seconds. When the appearance inspection and the actual copying test of the photosensitive member were conducted, the photosensitive layer was forgotten due to the secondary agglomeration of the photosensitive material, resulting in non-uniform image characteristics. Summarizing the above, the present invention is characterized in that coating is started after the liquid surface of the coating liquid is lowered from the opening of the coating tank at the end of immersion of the conductive substrate, that is, at the end of overflow. Further, the method of lowering the liquid level of the coating liquid from the coating tank opening of the present invention is not particularly limited, but the distance from the coating tank opening to the liquid level when the liquid level is lowered is the non-coated portion of the upper part of the photoreceptor. Is preferably set within 0 to 2 mm so as not to reach the image area, but is not particularly limited as long as it does not reach the image area. Also, the time from lowering the liquid level to the start of coating is 0
Approximately 30 seconds or so is preferable, and if it is too long, secondary aggregation of the photosensitive material occurs and the coating solution precipitates, causing uneven coating.

The coating tank of the coating apparatus constructed as described above is filled with the coating solution, and the conductive substrate is immersed in the coating tank to cause overflow. When the substrate reaches a desired depth, the immersion is stopped. At this point, the liquid surface of the coating liquid is located higher than the opening of the coating tank due to the influence of the surface tension of the coating liquid. Therefore, the liquid surface is lowered below the opening of the coating tank. Next, after the coating liquid is stabilized, the conductive substrate is drawn out and coating is performed to form a photosensitive layer on the substrate. Obtained in this way,
The coating film of the electrophotographic photosensitive member is uniform and has excellent coating properties.

Others The present invention is not limited to the embodiments described above and shown in the drawings, and it is needless to say that the present invention can be appropriately modified and implemented without departing from the scope of the invention.

[0026]

According to claim 1 of the present invention having the above structure, the photosensitive layer is formed after the unstable state of the liquid surface is released, so that a uniform photosensitive layer can be formed without causing coating unevenness. You can

According to the second aspect, as a means for lowering the liquid level, no special function is required, and the problem can be solved without modifying the conventional coating device.

According to the third aspect, since the photosensitive layer is formed after the liquid surface of the coating liquid is stabilized, a further effect can be exerted in suppressing uneven coating, and a more uniform photosensitive member can be formed.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an example of the present invention, showing a state immediately after a conductive substrate is immersed.

FIG. 2 is a cross-sectional view of an example of the present invention, showing a state at the start of coating.

[Explanation of symbols]

 1 coating liquid level 2 coating tank 3 coating tank opening 4 overflow receiving tank 5 coating liquid return port 6 coating liquid supply port 7 conductive substrate

Claims (3)

[Claims] 1. A coating apparatus for immersing a conductive substrate in a coating tank filled with the coating solution, allowing the coating solution to overflow, and then pulling out the conductive substrate to form a photosensitive layer, at the end of immersion of the conductive substrate. A coating device comprising means for lowering the liquid level of the coating liquid below the opening of the coating tank, and coating after the liquid level is lowered by the means. 2. The coating apparatus according to claim 1, wherein the means for lowering the liquid level is to lower the coating liquid level by pulling out the conductive substrate. 3. The coating apparatus according to claim 1, wherein the conductive substrate is pulled out and a photosensitive layer is formed on the conductive substrate after a predetermined time elapses after lowering the coating liquid surface.