JP2003057854A - Coating device for electrophotographic photoreceptor, coating method and electrophotographic photoreceptor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating device for an electrophotographic photoreceptor in which the generation of unevenness in coating film can be suppressed, coating method and an electrophotographic photoreceptor manufactured using the coating method. SOLUTION: In the coating device for the electrophotographic photoreceptor simultaneously immersing a multiple number of cylindrical substrates in coating liquid and forming coating films on the cylindrical substrates by withdrawing them, drying hoods corresponding to each of the multiple number of cylindrical substrates are provided over a coating tank.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photoreceptor coating apparatus, an electrophotographic photoreceptor coating method using the coating apparatus, and an electrophotographic photoreceptor manufactured by the coating method. The present invention relates to a coating apparatus using dip coating for forming an organic photosensitive layer on an outer peripheral surface of a cylindrical substrate in the production of an electrophotographic photoreceptor, a coating method using the coating apparatus, and an electrophotographic photoreceptor.

[0002]

2. Description of the Related Art Heretofore, as a photoconductive material constituting a photosensitive layer of an electrophotographic photosensitive member, inorganic compounds such as selenium, cadmium sulfide and zinc oxide and organic compounds represented by polyvinylcarbazole have been proposed. In a laminated electrophotographic photoreceptor having a photosensitive layer separated into a charge generation layer and a charge transport layer, various organic compounds have been proposed as a charge generation material and a charge transport material, and have been put to practical use as an organic photoreceptor. . Conventionally, as a coating method for such an organic photoreceptor, a dip coating method, a spray coating method, a spin coating method, a bead coating method, a wire bar coating method, a blade coating method, a roller coating method, an extrusion coating method, a curtain coating method. Although various coating methods such as the above are known, the dip coating method is widely used particularly as a method for forming a uniform photosensitive layer on the outer peripheral surface of a cylindrical substrate.

In recent years, there has been a strong demand for downsizing and weight saving of copying machines, printers, facsimiles and the like in which electrophotographic photoconductors are used, and accordingly, the electrophotographic photoconductors are becoming smaller year by year. It's peeled off. As a method for producing an electrophotographic photosensitive member, particularly an electrophotographic photosensitive member using a small-diameter cylindrical substrate by a dip coating method, from the viewpoint of improving productivity, JP-A-5-88385 and JP-A-6-262.
As described in Japanese Patent Publication No. 113, a multiple simultaneous dip coating method in which a plurality of cylindrical substrates are simultaneously dipped in a coating solution and pulled up is generally adopted. In particular, if the space between the cylindrical substrates is narrowed, the productivity will be further increased, which is advantageous, but at that time, the solvent vapor generated from the coating film formed when the cylindrical substrate is pulled up or generated from the liquid level in the coating tank. Due to the effect of the solvent vapor, the touch-drying speed of the coating film formed on the cylindrical substrate becomes non-uniform between the cylindrical substrates or within one cylindrical substrate, resulting in uneven film thickness. I will end up. As a workaround for this, Japanese Patent Laid-Open No. 59-1270.
As described in Japanese Patent Publication No. 49, etc., when the cylindrical substrate is not pulled up from the liquid surface, air is sent from the outside to the vicinity of the liquid receiving tank to reduce the solvent vapor concentration from the vicinity of the liquid receiving tank in advance. , Which accelerates the touch-drying speed,
As described in JP-A-3-151, etc., a solvent vapor discharge port is provided in the vicinity of the liquid receiving tank, and it is connected to a forced exhaust device provided with an ON-OFF mechanism, and is a cylinder when pulled from the liquid level in the coating tank. The unevenness of the film thickness is suppressed by controlling the solvent vapor concentration around the substrate.

However, in the above technique, the concentration of solvent vapor is low near the air supply port and around the cylindrical substrate near the solvent vapor discharge port connected to the forced exhaust device,
It became higher at the remote place, and it was difficult to make the solvent vapor concentration uniform.

Particularly, in an apparatus for coating a large number of cylindrical substrates at the same time, the concentration of solvent vapor around the cylindrical substrates is likely to be non-uniform, the drying speed is different among the substrates, and unevenness in film thickness and top The appearance of a photoconductor having an increased number of thin films has been a cause of a decrease in productivity.

As a measure for avoiding the non-uniformity of the solvent vapor concentration, for example, as shown in JP-A-8-220786, the solvent vapor discharge port is located at a position lower than the liquid level of the coating tank in the middle of the recycling pipe. It has been proposed that the solvent vapor concentration on the liquid surface of the coating layer be made uniform by using a solvent having a specific gravity higher than that of air and a relatively low saturated vapor concentration. However, in this method, by using a solvent with a low saturated vapor concentration, the drying speed tends to be slow, and the coating film tends to flow by the time finger dry (becomes non-greasy to the touch with the finger) is reached. As a result, the coating film at the coating tip becomes thin and the leading thin film becomes large, and unevenness in film thickness is likely to occur. In particular, in a charge generation layer or the like having a thin coating film thickness, unevenness in film thickness tends to occur.

[0007]

Therefore, the present invention has been made for the purpose of solving the above-mentioned problems in the prior art. That is, the object of the present invention is to make the solvent vapor generated from the coating film formed when a large number of cylindrical substrates are pulled up at the same time and the solvent vapor evaporated from the liquid surface of the coating tank as uniform as possible around the cylindrical substrate. Even if a solvent such as methylene chloride having a high saturated vapor concentration is discharged, the solvent can be discharged uniformly and the dry film thickness is 1 μm.
An object of the present invention is to provide a coating device for an electrophotographic photosensitive member, which has a small thickness unevenness even when a charge generation layer having a thickness of m or less is applied. Another object of the present invention is to provide a coating method for an electrophotographic photosensitive member, which is capable of forming a photosensitive layer without unevenness in film thickness on a cylindrical substrate by a dip coating method. To provide an electrophotographic photosensitive member formed by the above.

[0008]

The object of the present invention can be achieved by the following constitutions.

1. In an electrophotographic photoreceptor coating apparatus in which a plurality of cylindrical substrates are simultaneously immersed in a coating solution and pulled up to form a coating film on the cylindrical substrates, each of the plurality of cylindrical substrates is supported on a coating tank. An apparatus for coating an electrophotographic photosensitive member, which has the dried hood.

2. The dry hood is characterized in that the gap width between the hood and the cylindrical substrate when passing through the cylindrical substrate is 1/10 to 1 in terms of the diameter ratio of the cylindrical substrate.
An electrophotographic photoreceptor coating apparatus according to item 1.

3. 3. The electrophotographic photoreceptor coating apparatus according to 1 or 2 above, wherein the dry hood has a large number of ventilation holes.

4. One of the ventilation holes has an opening diameter of 0.1 to
The coating device for an electrophotographic photosensitive member according to the above 3, wherein the coating device has a diameter of 10 mmφ.

5. 5. The electrophotographic photoreceptor coating apparatus according to 3 or 4 above, wherein an opening area ratio of the entire ventilation holes (to an area of the entire drying hood) is 5 to 50%.

6. Using the electrophotographic photosensitive member coating apparatus according to any one of 1 to 5 above, a plurality of cylindrical substrates are simultaneously immersed in a coating solution and pulled up to form a coating film on the cylindrical substrate. And a method for coating an electrophotographic photosensitive member.

7. The coating thickness of the electrophotographic photoreceptor is 5 to
7. The method for coating an electrophotographic photoreceptor as described in 6 above, which has a thickness of 300 μm.

8. 8. The coating method for an electrophotographic photosensitive member according to 6 or 7, wherein the coating liquid is a charge generation layer forming coating liquid.

9. 9. An electrophotographic photosensitive member manufactured by using the method for coating an electrophotographic photosensitive member according to any one of 6 to 8 above.

The present invention will be described in detail below. FIG. 1 shows a schematic configuration of an example of the multiple simultaneous dip coating apparatus of the present invention, showing a state where a cylindrical substrate is being pulled up from a coating liquid. In FIG. 1, a solvent vapor storage chamber 11 for preventing the influence of an external air flow is provided on the coating tank 6.
And a separate drying hood 14 is provided above the solvent vapor storage chamber 11. When the cylindrical substrate is pulled up from the coating tank 6, it enters the solvent vapor storage chamber 14, where the coating film releases a large amount of solvent vapor, and the individual drying hood 1
4 and dried. In the present invention, the solvent vapor reservoir 1
It is preferable to provide a discharge port 12 between 1 and the drying hood 14. By providing the discharge port 12, the solvent vapor concentration in the solvent vapor reservoir chamber 11 can be kept uniform even in the case where a solvent having a high saturated vapor pressure is used for the coating liquid, and uneven touch-drying of the coating film can be achieved. Does not occur.

Here, the solvent vapor reservoir covers the coating layer,
This is a room for temporarily stagnating the solvent vapor generated from the coating liquid or coating film and maintaining an atmosphere with a uniform solvent vapor concentration. The outlet is formed between the solvent vapor reservoir and the drying hood so as to surround the cylindrical substrate when the coated substrate is pulled up. Also, the drying hood has a structure surrounding the cylindrical substrate.

On the other hand, the coating liquid 1 is pumped from the coating liquid tank 2 through the supply pipe 3 by the pump 4, and is supplied into the coating tank 6 through the filter 5. A mesh 15 is inserted in the lower part of the coating tank 6 in order to obtain uniform coating liquid flow velocity in the tank. The coating liquid supplied into the coating tank 6 overflows and is collected in the coating liquid receiving tank 7 provided at the lower end of the solvent vapor reservoir 11 at the upper part of the coating tank 6 to be recycled.
And is collected in the coating liquid tank 2. When performing dip coating using this dip coating device, when the cylindrical substrate 9 is dipped in the coating tank 6 and then pulled up, the cylindrical substrate 9 always overflows in order to keep the liquid level 10 of the coating tank constant. The coating liquid is circulated by the circulation means.

Conventionally, when a large number of cylindrical substrates are simultaneously coated, the drying hood provided on the coating liquid layer 6 is shown in FIG.
As described above, a structure in which the solvent vapor storage chamber is also used as a drying hood, that is, all of the large number of substrates are provided in a large drying hood 14 (hereinafter,
An apparatus having a structure surrounded by a large dry hood) was used, but with this structure, the solvent vapor concentration in the dry hood 14 does not easily decrease uniformly, and the solvent vapor concentration around each substrate decreases evenly. It was difficult to do so, and it tended to cause unevenness of film thickness and increase of the leading thin film.

In the present invention, as shown in FIG. 1, the solvent vapor reservoir chamber and the drying hood are separated, and the drying hood is provided for each individual cylindrical substrate, so that the drying conditions between the cylindrical substrates are made uniform and the drying is performed. By uniformly lowering the solvent vapor concentration in the hood, it is possible to prevent unevenness in film thickness and increase of the leading thin film, and to reduce characteristic variations among the photoconductors.

The dry hood preferably has a cylindrical form sufficient to allow the cylindrical substrate to pass through. That is,
It is preferable that the gap width between the hood of the dry hood and the cylindrical substrate is 1/10 to 1 in terms of the diameter ratio of the cylindrical substrate.
If the diameter ratio is less than 1/10, the dry hood and the substrate are likely to come into contact with each other when passing through the cylindrical substrate, and problems such as abrasion of the coating film are likely to occur. On the other hand, even if the diameter ratio is larger than 1, the device Does not contribute to the improvement of productivity.
The opening diameter of each ventilation hole is preferably 0.1 to 10 mm.
If it is less than 0.1 mm, solvent vapor tends to stay in the dry hood, and if it is greater than 10 mm, the inside of the dry hood is easily disturbed by the outside air.

It is also preferable that the dry hood has a large number of ventilation holes. The overall opening area ratio of the ventilation holes (with respect to the total area of the dry hood) is preferably 5 to 50%. If it is less than 5%, solvent vapor tends to stay in the dry hood, and if it is more than 50%, the environment inside the dry hood is easily disturbed by the outside air.

The length of the dry hood is preferably 5 to 300 cm. If it is less than 5 cm, the effect of the dry hood is small,
The effect of preventing uneven film thickness is small. Meanwhile, 300 cm
Even if the size is larger, the effect commensurate with the increase in size of the device cannot be obtained.

In the present invention, it is preferable to have a solvent vapor storage chamber below the drying hood and above the coating tank, but the distance from the coating liquid surface of the drying hood is preferably between 1 and 100 cm. That is, if it is less than 1 cm, the space of the solvent vapor storage chamber becomes narrow, and the coating film immediately after coating cannot be stabilized. Again 10
Even if it is larger than 0 cm, the effect commensurate with the increase in size of the device cannot be obtained.

Further, according to the present invention, it is preferable to provide an exhaust port between the solvent vapor storage chamber and the drying hood. By discharging the solvent vapor from the exhaust port, the solvent vapor concentration in the entire solvent vapor reservoir is made uniform, and the drying speed immediately after coating is set between the photoconductors.
Alternatively, it is preferable that the outlet 12 capable of reducing the film thickness unevenness in the circumferential direction of the substrate is installed with a gap width of 0.1 to 10 mm between the solvent vapor reservoir chamber and the drying hood.
If it is less than 0.1 mm, the discharge amount of solvent vapor is not sufficient, and 1
If it is 0 mm or more, the solvent vapor is sufficiently discharged, but the solvent vapor reservoir chamber is easily affected by the flow of external air, and the uniformity of the solvent vapor concentration in the solvent vapor reservoir chamber is likely to be disturbed.

The upper lid portion of the solvent vapor storage chamber is provided with an opening (hole) necessary for passing the cylindrical substrate. The opening is preferably circular like the cylindrical substrate.

The drying condition of the dry hood is preferably natural drying. Since the coating film in the drying hood is in a state immediately after coating, if the drying air is forcedly fed, the film thickness unevenness and the leading thin film are increased.

Further, in order to form a coating film on the outer peripheral surfaces of a plurality of cylindrical substrates at the same time, it is preferable that the coating and drying conditions of each substrate are made uniform, and there is no difference in the arrangement position of the cylindrical substrates. Arrangement methods are preferred. As a method for arranging such a substrate, the method for arranging the four-layer simultaneous coating apparatus shown in FIG. 3 is preferable.

As described above, by dip-coating a large number of cylindrical substrates using the apparatus of the present invention, the solvent is discharged to the outside of the system while keeping the touch-drying condition immediately after the dip-coating uniform among the individual substrates. You can As a result, the unevenness of the film thickness can be reduced in a wide range of the coating film thickness (coating film thickness including the solvent immediately after coating) of 30 to 300 μm.

Even if the solvent is selected from a wide range of saturated vapor pressure of 0.7 to 80 kPa, the effect of improving the unevenness of the film thickness can be maintained.

In the present invention, as the cylindrical substrate, a known electrically conductive one used in an electrophotographic photosensitive member is used. Any known material can be used as the coating liquid for forming the photosensitive member on the cylindrical substrate. For example, an undercoat layer coating liquid, a charge generating layer coating liquid, a charge transporting layer coating liquid, etc. are used, whereby an undercoating layer, a charge generating layer and a charge transporting layer, which are constituent layers of the photoreceptor, are formed. However, it is also possible to use a coating liquid for forming other photosensitive layer-constituting layers such as an intermediate layer and a surface layer.

The coating liquid solvent used in the present invention generally includes most of the organic solvents used in the coating liquid for forming an organic photosensitive layer. Specific examples include halogenated hydrocarbons such as methylene chloride, ethers such as tetrahydrofuran, alcohols such as ethyl alcohol, and ketones such as cyclohexanone.

[0035]

EXAMPLES The present invention will be specifically described below with reference to examples.

Example 1 The intermediate layer was formed on the cylindrical substrate as follows.

Polyamide resin CM8000 (manufactured by Toray)
1 part by mass and 10 parts by mass of methanol were added to the same container and dissolved and dispersed to prepare an intermediate layer coating liquid 1. The intermediate layer coating solution was applied to the independent dry hood of FIG. 1 (each dry hood has a large number of vent holes of 3 mmφ, and the opening area ratio of the vent holes is 25
%) And a cylindrical aluminum substrate (1.0 mmt × 30 mmφ × 340 m)
m). The coating liquid temperature at that time was 24 ° C. The speed of pulling up the aluminum substrate from the coating solution is 4
It was set to 80 mm / min. As the position of the outlet 12,
1m gap width between the solvent vapor reservoir and the drying hood shown in Fig. 1.
It is installed at m. The outlet is 10c from the liquid level of the coating tank.
It is formed with a circle of 50 mm at a height of m. The coating liquid circulation flow rate was 5 L / min, and the diameter of the recycle pipe 8 was 150 mmφ. Each coated substrate was air-dried through a 15 cm dry hood, then placed in a drier at 70 ° C.
In 10 minutes, it heat-dried and formed the 0.1-micrometer-thick intermediate | middle layer. Table 1 shows the film thickness unevenness values of the four films. Here, the thickness unevenness value is 20 mm from the upper end of the coating film,
It is the difference between the maximum value and the minimum value of the film thickness value at four points (90 ° intervals) in the circumferential direction at each of 50 mm, 160 mm, and 300 mm, for a total of 16 points. The saturated vapor pressure of methanol at 24 ° C. was 16 to 18.7 kPa.

Comparative Example 1 For comparison, the coating operation of the intermediate layer was carried out under the same conditions as in Example 1 except that a coating apparatus using a large dry hood as shown in FIG. 2 was used. The results are shown in Table 1.

[0039]

[Table 1]

The film thickness is measured by a photo-detection type film thickness measuring device M.
CPD-1000 (instantaneous multi-photometric detector: Otsuka Electronics Co., Ltd.) was used.

Example 2 Y-type titanyl phthalocyanine (60 g), silicone-modified butyral resin (manufactured by Shin-Etsu Chemical Co., Ltd.) (700 g) and 2-butanone (2000 ml) were mixed and dispersed in a sand mill for 10 hours to prepare a charge generation layer coating solution. This coating solution is shown in Figure 1.
Independent dry hoods (many 3mm each dry hood
It is coated on the aluminum substrate on which the intermediate layer obtained in Example 1 above is formed by using a four-piece simultaneous dip coating apparatus having a φ vent hole and an opening area ratio of the vent holes is 25%). Dry at 70 ℃ for 10 minutes, film thickness 0.2μ
m charge generating layer was formed. The speed of pulling up the aluminum substrate from the coating solution was 240 mm / min. The coating liquid temperature at that time was 24 ° C. As the position of the discharge port 12, a gap width of 1 mm is installed between the solvent vapor storage chamber and the drying hood shown in FIG. The discharge port is formed as a circle of 50 mm at a height of 10 cm from the liquid level of the coating tank. The circulating flow rate of the coating liquid was 5 L / min, and the diameter of the recycle pipe 8 was 150 mmφ. Table 2 shows the film thickness unevenness values of the four films. Thickness unevenness value is 20m from the top of the coating film
It is the difference between the maximum value and the minimum value of the film thickness value at four points (90 ° intervals) in the circumferential direction at each of m, 50 mm, 160 mm, and 300 mm, for a total of 16 points. 2 at 24 ° C
-Saturated vapor pressure of butanone was about 2.3 kPa and its specific gravity for air was about 0.81.

Comparative Example 2 For comparison, a charge generating layer was coated on the intermediate layer under the same conditions as in Example 2 except that a large dry hood was used as shown in FIG. The results are shown in Table 2.

[0043]

[Table 2]

Example 3 A charge generating layer was applied on the intermediate layer in the same manner as in Example 2, except that the interval width of the exhaust ports was changed from 1 mm to 8 mm. As a result, the thickness deviation of each substrate was almost the same as in Example 2.

Example 4 A charge generation layer was coated on the intermediate layer in the same manner as in Example 2 except that the interval width of the exhaust ports was changed to 1 mm. As a result, the thickness deviation of each substrate was almost the same as in Example 2.

From Tables 1 and 2, an intermediate formed by using a coating apparatus in which an independent hood corresponding to a plurality of cylindrical substrates is provided on a coating tank in which a plurality of cylindrical substrates are simultaneously immersed in a coating solution. It is found that the layer and the charge generation layer have significantly improved film thickness unevenness as compared with the case where a comparative large dry hood is used.

Further, these Examples 1 to 4 and Comparative Example 1,
A charge transport layer having a dry film thickness of 20 μm was dip-coated on each of the charge generation layers 2 to prepare an electrophotographic photoreceptor. These electrophotographic photoreceptors were mounted on a commercially available electrophotographic printer, a halftone image was formed, and image evaluation was performed. As a result, in the image evaluation using the electrophotographic photoconductors produced in Examples 1 to 4, a good halftone image having no image unevenness was obtained regardless of which photoconductor was used.
In the image evaluation using the electrophotographic photosensitive member obtained from No. 2, image unevenness occurred in the halftone image.

[0048]

As is apparent from the above examples, by using the electrophotographic photosensitive member coating apparatus of the present invention having an independent dry hood, the photosensitive layer or the intermediate layer formed on each cylindrical substrate can be formed. The film thickness can be made highly uniform on all cylindrical substrates, and as a result, a good cylindrical electrophotographic photosensitive member can be provided.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of an example of a multiple simultaneous dip coating apparatus of the present invention.

FIG. 2 is a diagram of a coating device using a large-sized dry hood.

FIG. 3 is a diagram of an arraying method of four simultaneous coating devices.

[Explanation of symbols]

1 coating liquid 2 Coating liquid tank 3 supply piping 4 pumps 5 filters 6 coating tanks 7 Coating liquid receiving tank 8 recycling pipes 9 Cylindrical substrate 10 Liquid level of coating tank (overflow surface) 11 Solvent vapor reservoir 12 outlet 14 Dry hood 15 mesh

Claims (9)

[Claims] 1. An electrophotographic photosensitive member coating apparatus in which a plurality of cylindrical substrates are simultaneously immersed in a coating solution and pulled up to form a coating film on the cylindrical substrates. An electrophotographic photoreceptor coating apparatus having a drying hood corresponding to a cylindrical substrate. 2. The dry hood has a gap width between the hood and the cylindrical substrate when passing through the cylindrical substrate of 1 as a diameter ratio of the cylindrical substrate.
It is comprised in // 10-1.
An electrophotographic photoreceptor coating apparatus according to item 1. 3. The electrophotographic photoreceptor coating apparatus according to claim 1, wherein the drying hood has a large number of ventilation holes. 4. One of the ventilation holes has an opening diameter of 0.1 to 1.
The electrophotographic photosensitive member coating apparatus according to claim 3, wherein the coating apparatus has a diameter of 0 mmφ. 5. The coating device for an electrophotographic photosensitive member according to claim 3, wherein an opening area ratio of the entire ventilation holes (to an area of the entire drying hood) is 5 to 50%. . 6. The electrophotographic photosensitive member coating apparatus according to claim 1, wherein a plurality of cylindrical substrates are simultaneously immersed in a coating solution and then pulled up onto the cylindrical substrate. A method for coating an electrophotographic photosensitive member, which comprises forming a coating film. 7. The coating thickness of the electrophotographic photosensitive member is 5 to 3
The coating method for an electrophotographic photosensitive member according to claim 6, wherein the coating thickness is 00 μm. 8. The method for coating an electrophotographic photosensitive member according to claim 6, wherein the coating liquid is a charge generating layer forming coating liquid. 9. An electrophotographic photosensitive member manufactured by using the method for coating an electrophotographic photosensitive member according to claim 6.