JPH04340969A - Production of electrophotographic sensitive material - Google Patents

Abstract

PURPOSE:To uniformly stirring a coating liquid without producing bubbles and to obtain a photosensitive material for electrophotography in a uniform coating state without irregularity by detecting the liquid amt. in a stirring tank for the coating liquid and controlling the rotation of the impeller according to the liquid amt. CONSTITUTION:The amt. of the coating liquid in a stirring tank 12 for the coating liquid is detected with a liquid surface sensor 1. According to the liquid amt. in the tank 12, rotation of a motor 3 is controlled with a controller 2 to adjust rotation of the impeller 4 to the optimum stirring rate of the coating liquid in the tank 12. Fir example, when the sensor 1 detects a large amt. of liquid in the tank 12, rotation of the motor 3 is increased by the controller 2 to make the impeller 4 rotate at high speed so that the coating liquid can be enough stirred even in the upper part of the liquid. On the other hand, with decrease of the coating liquid, its amt. is detected with the sensor 1 and rotation of the motor 3 is decreased with the controller 2 based on the obtd. data. Thus, rotation of the impeller 4 is decreased to prevent production of bubbles.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a method for manufacturing an electrophotographic photoreceptor, and more particularly, to an electrophotographic photoreceptor, which involves stirring a coating solution in a coating solution stirring tank uniformly and without generating bubbles. Relating to a manufacturing method.

0002

[Prior Art] Electrophotographic photoreceptors for copying machines, printers, etc. currently in practical use include a charge generation layer using a condensed polycyclic pigment or an azo pigment on the surface of a conductive substrate such as Al, and a charge generation layer using a condensed polycyclic pigment or an azo pigment. It is formed by coating and laminating a charge transport layer using an amine-based material or the like. Coating of such electrophotographic photoreceptors and the like is mainly performed by a dip coating method as shown in FIGS. 3(A) to 3(C). That is, this method forms a photosensitive layer of a constant thickness on the surface of the substrate by dipping the conductive substrate 5 into the coating liquid 6 in the coating tank 13 and pulling it up.

FIG. 2 shows a photoreceptor coating apparatus used in the conventional dip coating method. The coating liquid is stored in a stirring tank 12 for storage and stirring, and is stirred by rotation of stirring blades 21. The coating liquid in the stirring tank 12 is supplied from the stirring tank 12 to the coating tank 13 through a supply pipe 14 by a pump 15 . Further, the coating liquid overflowing from the coating tank as the conductive substrate is immersed is collected in the overflow tank 16 and returned to the stirring tank 12 through the return pipe 17, where it is homogenized with the coating liquid remaining in the stirring tank 12 by stirring. be done.

As shown in FIG. 2, the stirring blades of a conventional photoreceptor coating device are installed at an angle with respect to the surface of the coating liquid in the stirring tank 12. Prior to this, the stirring blades were installed almost horizontally with respect to the coating liquid level in the stirring tank, that is, almost horizontally with respect to the vertical stirring shaft 11; The stirring blade stirs the coating liquid at the bottom of the stirring tank, but the closer it gets to the liquid surface, the less agitated the liquid is, and especially when the coating liquid is almost full in the stirring tank, the liquid level is lower than that of the stirring blade. The actual situation was that the coating liquid in the upper and lower parts of the stirring tank was hardly stirred even though there was only a slight movement in the direction of rotation. In order to solve this problem, we increased the stirring rotation speed, and as a result, we were able to achieve uniform stirring of the upper and lower parts of the coating liquid in the stirring tank, but the disadvantage was that bubbles were formed as the amount of coating liquid decreased. was there.

In order to eliminate this drawback of air bubbles and to uniformly stir the upper and lower parts of the coating liquid even when the stirring tank is nearly full, stirring blades 2 are used as shown in FIG.
1 diagonally with respect to the surface of the coating liquid, it became possible to uniformly stir the upper and lower parts of the coating liquid in the stirring tank 12 by low rotation.

[0006]

[Problems to be Solved by the Invention] However, even with the stirring device shown in FIG. 2, when the liquid level falls to the position where the stirring blades 21 appear, bubbles are generated in the coating liquid, and this liquid becomes difficult to coat. When the coating liquid is sent to the tank 13, there is a risk that air bubbles generated in the coating liquid may adhere to the conductive substrate. If the conductive substrate is pulled up with air bubbles attached to it, the air bubbles will fall due to gravity, causing unevenness and sagging on the coating surface. Additionally, if air bubbles burst during drying, craters (concave defects) may occur on the coated surface. In the case of an electrophotographic photoreceptor, such defects appear as unevenness, white dots, and black dots on the image, resulting in image defects. For this reason, the coating liquid with bubbles is allowed to stand until all the bubbles disappear. However, depending on the viscosity of the coating solution or the type of binder used as a material, the bubbles may not disappear even after several hours, and the coating solution may be discarded. had a significant impact on the efficiency of use.

[0007] In addition, in order to equalize the stirring in the upper and lower parts of the stirring tank, baffle plates are installed on the inner wall of the stirring tank (several plates are installed vertically on the inner wall of the stirring tank, facing toward the center of the stirring tank (not shown). There is also a method of increasing the agitation effect at the top and bottom of the stirring tank by installing a baffle plate, but this tends to cause aggregates of the coating liquid to accumulate at the joint between the baffle plate and the inner wall of the stirring tank, and if this gets mixed into the coating liquid and is applied, It has defects that appear as white dots, black dots, etc. on the image.Furthermore, it has the drawback that cleaning the inside of the stirring tank is very difficult.

[0008]

[Means for Solving the Problems] In order to solve the above-mentioned drawbacks, as a result of intensive research by the present inventors, in a method for manufacturing an electrophotographic photoreceptor, the number of rotations of the stirring blade of the stirring tank for the coating liquid is adjusted to the same level as the stirring speed. By controlling the amount of coating liquid in the tank, air bubbles are not generated in the coating liquid, and the upper and lower parts of the coating liquid in the agitation tank are uniformly stirred, thereby stabilizing the coating liquid. It was discovered that a coating film free of surface defects could be obtained, and the present invention was completed based on this finding.

[0009]

[Operation] FIG. 1 is an overall view of liquid level detection in a coating liquid stirring tank and stirring blade rotation speed control in the method of manufacturing an electrophotographic photoreceptor according to the present invention.

The amount of the coating liquid in the coating liquid stirring tank 12 is detected by the liquid level sensor 1, and the number of rotations of the motor 3 is controlled by the control device 2 according to the amount of liquid in the stirring tank 12, thereby adjusting the number of rotations of the stirring blade 4. is adjusted to optimize the stirring state of the coating liquid in the stirring tank 12. For example, when the liquid level sensor 1 detects that a large amount of coating liquid is in the stirring tank 12, the control device 2 increases the rotation speed of the motor 3 based on that data and rotates the stirring blades 4 at high speed. , stir thoroughly until it reaches the top of the coating solution. On the other hand, as the amount of the coating liquid decreases, the amount is detected by the liquid level sensor 1, and based on the obtained data, the control device 2 lowers the rotation speed of the motor 3 and the rotation speed of the stirring blade 4. Stir to prevent air bubbles from forming.

The charge generation layer of the electrophotographic photoreceptor of the present invention comprises a charge generation material that generates charges upon irradiation with light, a binder, a plasticizer, a sensitizer, and the like. The charge generating material is not particularly limited and any known charge generating material may be used. for example,
Examples include perylene pigments, polycyclic quinone pigments, phthalocyanine pigments, and azo pigments. The charge generation layer is prepared by immersing the conductive substrate in a coating solution in which a charge generation material, a binder, a plasticizer, a sensitizer, etc. are dispersed in a solvent such as cyclohexanone, chlorobenzene, dichloroethane, or methyl ethyl ketone, and then pulling it up. It is dried and formed on the surface of the conductive substrate.

The charge transport layer of the present invention comprises a charge transport material having the ability to accept and transport charges generated by a charge generating material, a binder, a plasticizer, a sensitizer, and the like. Examples of the charge transport material include electron donating substances such as poly-N-vinylcarbazole derivatives, oxazole derivatives, hydrazone derivatives, and oxodiazole derivatives, and electron accepting substances such as fluorene derivatives, dibenzothiophene derivatives, and phenazine oxide derivatives. The binder constituting the charge transport layer may be any binder as long as it is compatible with the charge transport material, such as polycarbonate, polyvinyl butyral, polyamide, polyester, polyketone, epoxy resin, phenol resin, phenoxy resin, etc. Can be mentioned. The charge transport layer is formed on the charge generation layer by dip coating a coating solution in which a charge transport material, a binder, a plasticizer, a sensitizer, etc. are dissolved in a solvent such as dichloromethane, dichloroethane, cyclohexanone, chlorobenzene, or chloroform. be done.

The liquid level detection and stirring blade rotation speed control system of the present invention is particularly suitable for dip coating a charge generation layer and/or charge transport layer on a conductive substrate.

According to the method of the present invention, the stability of the coating solution can be achieved by improving the agitation properties of the coating solution, so even when the amount of the coating solution is small, the generation of air bubbles in the coating solution is prevented, and the formation of air bubbles on the coating surface is prevented. As a result, a coating film without surface defects can be obtained.

Furthermore, even if the amount of liquid decreases, no bubbles are generated in the coating liquid in the stirring tank, so the coating liquid can be used without leaving any residue, which improves the efficiency of using the coating liquid.
This can contribute to reducing the manufacturing cost of photoreceptors.

[0016]

[Examples] The present invention will be specifically explained below with reference to Examples, but the present invention is not limited to these Examples.

Liquid A was used as the coating liquid for the charge generation layer, and liquid B was used as the coating liquid for the charge transport layer.

[0018] Liquid A ・Dibrom anthurone
2
Parts by weight - Butyral resin (S-LEC BM-2 manufactured by Sekisui Chemical Co., Ltd.) 2 parts by weight - Cyclohexanone
230 parts by weight was dispersed in a ball mill for 8 hours.

B Liquid - Hydrazone-based charge transport material (product name - ABPH
(manufactured by Nippon Kayaku Co., Ltd.)

1 part by weight
・Polycarbonate resin (product name - Panlite L-12
50 Teijin Kasei Ltd.)

1 part by weight dissolved in 8 parts by weight of dichloroethane.

An ultrasonic liquid level sensor (FLD-200) manufactured by Mitsubishi Yuka Co., Ltd. was used as the liquid level sensor, and was installed on the outer wall of the stirring tank.

[0021] Two stirring blades 4 were installed in a twisted manner relative to the rotating shaft 11 in order to improve the stirring efficiency. The inner diameter of the stirring tank 12 is 300 mm, and the depth is 550 mm from the bottom of the stirring tank 12 when the coating liquid is full.
mm (because the liquid level becomes higher on the inner wall side of the stirring tank due to stirring, the coating liquid should only be poured up to 500 mm from the bottom).

Example 1 When the charge generation layer was dip-coated with the amount of coating liquid and the rotational speed of the stirring blade set as in Example 1 shown in FIG. 4, the coating liquid (liquid A) was 500 mm long. However, the coating liquid is sufficiently stirred, and even if the coating liquid decreases, the rotation speed of the stirring blade decreases accordingly, so bubbles will not be generated even if the coating liquid level reaches the position of the stirring blade 4 (position 4b in Figure 4). Not at all. By using the stirring blade rotation speed control method of the present invention, the stirring state of the coating liquid is always good regardless of the amount of liquid in the stirring tank 12, and since no air bubbles are generated in the stirring tank 12, the liquid circulation pump 15, the coating liquid containing air bubbles was not sent to the coating tank 13, and defects caused by this (adhesion of air bubbles, sagging, unevenness) did not occur during coating.

Comparative Example 1-1 (High-speed stirring) Coating liquid (
When the liquid A) was stirred at 150 rpm, efficient stirring was performed when the coating liquid level was 500 mm from the bottom of the stirring tank 12, but when the liquid level was 300 mm (Fig. 4 Comparative Example 1)
It was observed that air bubbles were mixed into the coating liquid below point a) of -1.

Comparative Example 1-2 (Medium rotation stirring) Coating liquid (
When liquid A) was stirred at 70 rpm, when the coating liquid level was 500 mm from the bottom of the stirring tank 12, the liquid surface was only slightly flowing in the direction of rotation of the stirring blade, and there was no stirring near the liquid surface. It was in a state where it was not. Liquid level is 350mm
When the temperature reaches around 100, the agitation condition of the coating liquid becomes good.
Bubbles were generated when the thickness became less than mm (point a in Comparative Example 1-2 in FIG. 4).

Comparative Example 1-3 (Low rotation stirring) Coating liquid (
When liquid A) was stirred at 23 rpm, no bubbles were generated even when the liquid level decreased to the position of stirring blade 4, but when the liquid level was 2.
When the distance was 50 mm or more (FIG. 4, point c in Comparative Example 1-3), the stirring state was insufficient and no flow was observed on the surface of the coating solution.

Example 2 When the charge transport layer was dip-coated with the amount of coating liquid and the rotational speed of the stirring blade set as in Example 2 shown in FIG. 5, 500 mm of coating liquid (liquid B) remained. However, the coating liquid is sufficiently stirred, and even if the coating liquid decreases, the rotation speed of the stirring blade decreases accordingly, so bubbles will not be generated even if the coating liquid level reaches the position of the stirring blade 4 (position 5b in Figure 5). Not at all. By using the agitating blade rotation speed control method of the present invention, the agitation state of the coating liquid is always good regardless of the amount of liquid in the agitating tank 12, and since no bubbles are generated in the agitating tank 12, the liquid circulation is improved. The pump 15 did not send a coating liquid containing air bubbles into the coating tank 13, and defects caused by this (adhesion of air bubbles, sagging, unevenness) did not occur during coating.

Comparative Example 2-1 (High-speed stirring) Coating liquid (
When liquid B) was stirred at 150 rpm, the liquid level was 15.
Bubbles were generated when the thickness reached 0 mm (point a in Comparative Example 2-1 in FIG. 5). Also, at 500 mm, it may be because the viscosity is higher than that of A liquid (A liquid = 8 mpa・s, B liquid = 50 mpa・s
) From the state of the liquid level, it was determined that the stirring was somewhat insufficient.

Comparative Example 2-2 (Medium rotation stirring) Coating liquid (
When liquid B) was stirred at 100 rpm, the liquid level was 50.
When it is 0mm, the liquid level is 30mm even if it is only slightly flowing.
Stirring conditions became better when it became less than 0 mm. Further, when the thickness reached 100 mm (point a in Comparative Example 2-2 in FIG. 5), many bubbles were generated.

Comparative Example 2-3 (Low rotation stirring) Coating liquid (
Even when the liquid B) was stirred at 50 rpm, bubbles were generated when the liquid level fell to the position of the stirring blade (point a in Comparative Example 2-3 in FIG. 5). It was confirmed that when the liquid level was lowered to the position of the stirring blade, bubbles were generated unless stirring was performed at a lower speed.

Example 3 and Comparative Example 3 In coating liquid A for the charge generation layer, a conductive substrate was dip-coated into a coating tank in which liquid A stirred in Example 1 was circulated by a circulation pump, and a dry film was formed. A film was formed to a thickness of 0.1 μm and dried at 90° C. for 10 minutes. On the other hand, liquid A was stirred at the rotational speed of Comparative Example 1-2, and the liquid volume in the stirring tank decreased and bubbles were generated, and the liquid A was circulated by a circulation pump to a coating tank in which a dry film thickness of 0.5 mm was applied to a conductive substrate. The coating was applied by dip coating to a thickness of 1 μm, and the formed film was dried at 90° C. for 10 minutes. On the obtained film, liquid B of the charge transport layer, which was confirmed to have no air bubbles in the coating tank, was formed to a dry film thickness of 20 μm and dried at 70° C. for 60 minutes. When the obtained photoreceptor was mounted on a copying machine manufactured by Sharp Corporation SF-8200 and image evaluation was performed, air bubbles were generated in the stirring tank A.
The photoreceptor coated with the liquid (Comparative Example 3) had countless 0.3 to 0.
A white spot with a diameter of 5 mm and something like sagging appearing from it appeared in the image, but the photoreceptor (Example 3) coated with liquid A without bubbles produced an image without white spots or sagging. I was able to do that.

Example 4 and Comparative Example 4 Liquid A of the charge generation layer was dip-coated on two conductive substrates under conditions that no air bubbles were attached to give a dry film thickness of 0.1 μm, and the film was formed. It was dried in the same manner as in Example 3. On top of that, liquid B of the charge transport layer of Example 2 with no bubbles and liquid B of Comparative Example 2-2 with the liquid level reduced to 100 mm and bubbles generated were sent into the coating tank by a circulation pump and charged. A film was formed by dip coating on the generation layer to a dry film thickness of 20 μm, and dried in the same manner as in Example 3. When the images of the obtained photoreceptors were evaluated using a copier SF-8200 manufactured by Sharp Corporation, bubbles were generated. Only the photoreceptor on which liquid B was formed (Comparative Example 4) had numerous white spots. , sunspots, and sagging were observed.

[0032]

[Effects of the Invention] By using the method of the present invention in which the rotational speed of the stirring blade is controlled according to the amount of the coating liquid in the stirring tank, the stirring effect of the coating liquid is always good regardless of the liquid amount.
In addition, even when the coating liquid decreases, bubbles do not occur, and a stable high-quality coating liquid can be fed into the coating tank, making it possible to stably produce electrophotographic photoreceptors.

Furthermore, since the coating liquid in the stirring tank can be used to the limit, the efficiency of using the coating liquid is greatly increased, making it possible to provide an electrophotographic photoreceptor at a low cost.

[Brief explanation of drawings]

FIG. 1 is an overall diagram of liquid level detection in a coating liquid stirring tank and stirring blade rotation speed control in the method of manufacturing an electrophotographic photoreceptor of the present invention.

FIG. 2 is an overall view of a conventional photoreceptor coating apparatus for an electrophotographic photoreceptor.

FIG. 3 is a diagram showing a dip coating method for an electrophotographic photoreceptor.

FIG. 4 is a diagram showing the relationship between the distance from the lower end of the stirring tank of the charge generation layer coating liquid to the liquid level and the rotation speed of the stirring blade.

FIG. 5 is a diagram showing the relationship between the distance from the lower end of the stirring tank of the charge transport layer coating liquid to the liquid level and the rotation speed of the stirring blade.

[Explanation of symbols]

1 Liquid level sensor 2 Control device 3 Motor 4 Stirring blade 5 Conductive substrate 6 Coating liquid 12 Stirring tank 13 Coating tank

Claims (1)

[Claims] 1. A method for manufacturing an electrophotographic photoreceptor in which a photosensitive layer is formed on a conductive substrate, comprising: detecting the amount of liquid in a coating liquid stirring tank, and controlling the rotational speed of a stirring blade based on the detected liquid amount. A method for producing a featured electrophotographic photoreceptor.