JPH10244195A - Immersion coating applicator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the introduction of air bubbles together with a coating liquid for film formation to an immersion bath to be immersed with a conductive substrate in the case of the introduction of the coating liquid for film formation from a tank in which the coating liquid for film formation is stored to the immersion bath with an immersion coating applicator for circulating the coating liquid for film formation between the immersion bath and the tank. SOLUTION: This device is provided with the immersion bath 10 which applies the coating liquid 2 for film formation on the conductive substrate 1 by immersing the conductive substrate 1 into the coating liquid, the tank 14 in which the coating liquid for film formation is stored, a guide pipe 13 which guides the coating liquid for film formation from the immersion bath to the tank and a supply pipe 17 which supplies the coating liquid for film formation from the tank to the immersion bath. In such a case, the supply pipe is provided with a filter 19 for passing the coating liquid for film formation supplied from the tank to the immersion bath. The filter 19 and the tank are communicated by a return pipe 24.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dip coating apparatus used for applying a coating liquid for forming a film to a conductive substrate, and more particularly to applying a coating liquid for forming a film by immersing the conductive substrate. In a dip coating apparatus configured to circulate the coating liquid for film formation between the immersion tank and the tank storing the coating liquid for film formation, when the coating liquid for film formation is guided from the tank to the immersion tank, The present invention relates to a dip coating apparatus that suppresses bubbles from being introduced into a dip tank together with a forming coating liquid.

[0002]

2. Description of the Related Art Conventionally, in producing an electrophotographic photosensitive member used in an electrophotographic apparatus such as a copying machine or a printer, a coating liquid for forming a film such as a coating liquid for a photosensitive layer is applied to a conductive substrate and dried. Then, a photosensitive layer or the like is formed on the surface of the conductive substrate.

Here, various coating apparatuses have conventionally been used for applying a coating liquid for forming a film on the surface of a conductive substrate. One of such coating apparatuses is known as a coating apparatus. An immersion coating apparatus is widely used in which a conductive substrate is immersed in an immersion tank containing a coating liquid for forming, and then the conductive substrate is pulled out of the immersion tank to apply a coating liquid for film formation. I was

A dip coating apparatus for immersing a conductive substrate in a dip tank containing the coating liquid for film formation and applying the coating liquid for film formation to the conductive substrate is shown in FIG. A dip coating apparatus as shown was used.

In this dip coating apparatus, as shown in FIG. 1, the dip tank 10 is placed on the upper periphery of a dip tank 10 containing a film forming coating liquid 2 for dipping a conductive substrate 1. An overflow receiving portion 11 for accommodating the overflowing coating liquid 2 for film formation is provided, and the coating liquid 2 for film formation is stored in the overflow receiving portion 11 via a guide tube 13 provided with a valve 12 at an appropriate position. Tank 1
The coating liquid 2 for film formation contained in the overflow receiving portion 11 is supplied to the tank 14 through the guide tube 13.

On the other hand, in the tank 14, the coating liquid 2 for film formation guided from the overflow receiving portion 11 through the guide tube 13 and the coating liquid 2 for film formation stored in the tank 14 as described above. Is stirred by a stirrer 15, and the solvent 2 a is supplied from an auxiliary tank 16 containing the solvent 2 a in the film-forming coating liquid 2 as needed to reduce the viscosity of the film-forming coating liquid 2 in the tank 14. The coating liquid 2 for film formation in the tank 14 is sucked into the supply pipe 17 by the pump 18 provided in the supply pipe 17 which makes the adjustment and the bottom of the tank 14 communicate with the bottom of the immersion tank 10. The coating liquid for film formation 2 is guided to the bottom of the immersion tank 10 through a filter 19 and a valve 20 provided in the immersion tank 10.
The coating liquid 2 for film formation was supplied into the immersion tank 10 from 1, and the coating liquid 2 for film formation was circulated between the immersion tank 10 and the tank 14.

Here, in such a dip coating apparatus, the coating liquid 2 for film formation overflowing from the dip tank 10 is used.
Is supplied from the overflow receiving portion 11 into the tank 14 through the guide tube 13, or when the coating liquid 2 for forming a film is stirred in the tank 14 by the stirring device 15, etc. Air entered the liquid 2, and the air thus entered became bubbles and was led to the immersion tank 10 through the supply pipe 17 together with the coating liquid 2 for film formation.

When bubbles are mixed in the coating liquid 2 for film formation in the immersion tank 10 as described above, the conductive substrate 1 is moved to the coating liquid 2 for film formation in the immersion tank 10 as described above.
When the coating liquid 2 for forming a film is applied to the conductive substrate 1 by immersion in the substrate, the air bubbles adhere to the surface of the conductive substrate 1, whereby the coating liquid 2 for forming the film is applied to the conductive substrate 1. Unevenness occurs, and a uniform film is not formed on the conductive substrate 1,
When an electrophotographic photosensitive member is manufactured by forming a film such as a photosensitive layer on the conductive substrate 1 by such a dip coating apparatus, the formed photosensitive layer or the like becomes uneven, and such an electrophotographic photosensitive member is used. When an image is formed by using the above method, there is a problem that a noise or the like due to the above-mentioned unevenness occurs and a good image cannot be obtained.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems in a dip coating apparatus used for applying a coating liquid for forming a film on a conductive substrate.

That is, the present invention provides an immersion tank for immersing a conductive substrate as described above to apply a coating liquid for film formation,
In a dip coating apparatus configured to circulate a coating liquid for forming a film between a tank storing the coating liquid for forming a film and the coating liquid for forming a film, the coating liquid for forming a film is introduced from the tank to the immersion tank. In the case where the conductive substrate is immersed in the coating liquid for film formation in the immersion tank to suppress bubbles from being led to the immersion tank together with the liquid, and the coating liquid for film formation is applied to the conductive substrate. It is another object of the present invention to provide an electrophotographic photoreceptor having good characteristics without causing a coating liquid for forming a film to be uniformly applied to a conductive substrate to cause application unevenness or the like.

[0011]

In the dip coating apparatus of the present invention, in order to solve the above-mentioned problems, a dip tank for dipping a conductive substrate and applying a coating liquid for film formation to the conductive substrate is provided. A tank in which the coating liquid for film formation is stored, a guide pipe for guiding the coating liquid for film formation from the immersion tank to the tank, and a supply pipe for supplying the coating liquid for film formation from the tank to the immersion tank In the dip coating apparatus provided with a filter for passing the coating liquid for film formation supplied from the tank to the immersion tank in the supply pipe, the filter and the tank were connected by a return pipe.

As in the dip coating apparatus of the present invention, a filter is provided in a supply pipe for supplying a coating liquid for film formation from a tank to a dip tank, and the coating liquid for film formation in the tank is immersed through the filter by the supply pipe. When the filter and the tank are communicated with each other by a return pipe when sent to the tank, even if bubbles are mixed in the coating liquid for film formation in the tank, the bubbles are suppressed in the filter portion. The bubbles suppressed in the filter are returned to the tank together with the coating liquid for film formation through the return pipe, so that bubbles are not mixed into the coating liquid for film formation supplied to the immersion tank. .

For this reason, when the conductive substrate is immersed in the coating liquid for film formation in the immersion tank and the coating liquid for film formation is applied to the conductive substrate, bubbles are generated on the surface of the conductive substrate. The coating liquid for film formation can be uniformly applied to the conductive substrate without causing the application of the coating liquid for film formation to the conductive substrate due to the adhesion to the conductive substrate.

In forming a film with the dip coating apparatus of the present invention, it is preferable that the coating liquid for forming a film is fed from a tank to a dip tank via a filter, and the coating is performed in a state of overflowing from the upper part of the dip tank. In order to perform film formation continuously with this dip coating device, at least when the amount of coating liquid consumed in the dip tank is very large, if the coating liquid for film formation flows too much into the return pipe, The pump pressure must be increased more than necessary in order to secure the necessary amount of the coating liquid for dip coating, and air bubbles were generated when pumping from the pump, which caused problems. is there. Therefore, even when the amount of the coating liquid consumed is large, the diameter of the return pipe is made smaller than the diameter of the supply pipe in order to reliably remove bubbles while securing a sufficient supply amount of the coating liquid to the immersion tank,
Alternatively, it is desirable to control the amount of the coating liquid for film formation returned through the return pipe by providing a valve for adjusting the amount of liquid in the return pipe.

The amount of the coating liquid consumed in the dipping tank includes the number of conductive substrates to be dipped, the diameter of the conductive substrate, the film thickness formed on the surface of the conductive substrate, the type of the coating liquid for film formation, and the film formation. The diameter of the return pipe is too large to supply the coating liquid for film formation to the immersion tank through the supply pipe if the diameter is too large. On the other hand, if the diameter is too small, the air bubbles removed by the filter cannot be sufficiently returned to the tank and the air bubbles are sent to the immersion tank. 0.15 to 0.3 times the diameter of the supply pipe.

In the case of adjusting by the above-mentioned liquid amount adjusting valve, it is not necessary to particularly define the diameter of the return pipe, and the flow rate of the coating liquid flowing through the return pipe to the flow rate of the coating liquid flowing through the filter into the immersion tank is not required. It is preferable to control to 0.02 to 0.2 times

As the coating liquid for forming a film to be contained in an immersion tank or a tank, various coating liquids for forming a film are used. For example, a coating liquid for forming a photosensitive layer used for forming a photosensitive layer on a conductive substrate is used. Liquid, a charge generation layer coating liquid or a charge transport layer coating liquid used to form a photosensitive layer in which a charge generation layer and a charge transport layer are laminated on a conductive substrate, and a conductive substrate and a photosensitive layer. An undercoat layer coating liquid for providing an undercoat layer between them, and a protective layer coating liquid for providing a protective layer on the photosensitive layer are used.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A dip coating apparatus according to an embodiment of the present invention will be specifically described below with reference to the accompanying drawings.

In the dip coating apparatus of this embodiment, as shown in FIG. 2, similarly to the dip coating apparatus shown in FIG. 1, a dip coating film containing a film forming coating liquid 2 for dipping a conductive substrate 1 is accommodated. An overflow receiver 11 for receiving the film forming coating liquid 2 overflowing from the immersion tank 10 is provided on the outer periphery of the upper part of the tank 10, and the overflow receiver 11 is provided with a guide tube 13 provided with a valve 12 at an appropriate position.
Through a tank 14 in which the coating liquid 2 for film formation is stored, and through this guide tube 13 the overflow receiving portion 1
The coating liquid 2 for film formation contained in 1 is supplied to a tank 14.

In the dip coating apparatus according to this embodiment, a discharge pipe 22 is also provided on the lower side of the dip tank 10, and the discharge pipe 22 is connected to the guide pipe 13 and the switching valve 2.
3, and the film forming coating liquid 2 supplied to the tank 14 through the guide tube 13 by the switching valve 23.
Is switched between the overflow receiving portion 11 and the immersion tank 10. When the dip coating apparatus is not used, or when the coating liquid 2 for film formation in the immersion tank 10 is replaced, the immersion is performed by the switching valve 23. The coating liquid 2 for film formation in the tank 10 is discharged to the tank 14.

In the tank 14, the coating liquid 2 for film formation guided from the overflow receiving portion 11 through the guide tube 13 and the coating liquid 2 for film formation accommodated in the tank 14 as described above. Stirrer 1 to stir
5 is provided, and the coating liquid 2 for forming a film is stirred by the stirring device 15. A viscometer 25 for measuring the viscosity of the coating liquid 2 for forming a film in the tank 14 is provided. The auxiliary tank 16 containing the solvent 2a of the coating liquid 2 is connected to a solvent supply pipe 1 provided with a valve 16a.
6b, when the viscosity of the coating liquid for film formation 2 measured by the viscometer 25 increases, the valve 16a is opened to supply the solvent 2a from the auxiliary tank 16, The viscosity of the coating liquid 2 for film formation in the tank 14 is adjusted.

Here, in the dip coating apparatus of this embodiment, a pump 18 and a filter 19 are connected to a supply pipe 17 that connects the bottom of the tank 14 and the bottom of the dip tank 10.
And a valve 20, and a return pipe 24 is provided above the filter 19, and the return pipe 24 is connected to an upper part of the tank 14.

Then, the tank 1 is controlled by the pump 18 described above.
The coating liquid 2 for film formation in the suction pipe 4 is sucked.
The coating liquid 2 for film formation is guided to the filter 19 through the filter, foreign matter in the coating liquid 2 for film formation is removed by the filter 19 and bubbles mixed in the coating liquid 2 for film formation are partially removed. The coating solution 2 and the coating liquid 2 are led to the above-mentioned return pipe 24 attached to the upper portion of the filter 19, and bubbles are formed through the return pipe 24 together with the coating liquid 2 for film formation in the tank 14.
To return to.

After the bubbles are removed in the filter 19, the remaining coating liquid 2 for film formation is led to the bottom of the immersion tank 10 through the valve 20 by the supply pipe 17, and the bottom of the immersion tank 10 Injection nozzle 21 provided
To the immersion tank 10, and the coating liquid 2 for film formation is supplied to the immersion tank 1.
It circulates between 0 and the tank 14.

For this reason, in the dip coating apparatus of this embodiment, the coating liquid 2 for film formation is supplied into the tank 14 through the guide tube 13, or the coating liquid 2 for film formation is stirred in the tank 14. For example, in the case of agitation by 15, even if air enters the coating liquid 2 for film formation in the tank 14, and this air becomes bubbles and is guided to the supply pipe 17 together with the coating liquid 2 for film formation. As described above, air bubbles mixed in the coating liquid 2 for film formation are returned to the tank 14 through the return pipe 24 together with a part of the coating liquid 2 for film formation, and supplied from the tank 14 to the immersion tank 10. No bubbles are mixed into the coating liquid 2 for film formation to be performed.

When the conductive substrate 1 is immersed in the coating liquid 2 for film formation accommodated in the immersion tank 10 to apply the coating liquid 2 for film formation, bubbles are generated in the conductive substrate 1.
The coating liquid 2 for film formation applied to the conductive substrate 1 is not uneven, and the coating liquid 2 for film formation is uniformly applied to the conductive substrate. By drying the applied coating liquid 2 for forming a film, a uniform layer without unevenness is formed on the conductive substrate 1.

Next, a specific example using the dip coating apparatus of the above embodiment will be described, and a comparison with a comparative example using the conventional dip coating apparatus shown in FIG. 1 will be described. In the dip coating apparatus, it will be clarified that bubbles are prevented from being mixed into the coating liquid 2 for film formation in the dip tank 10.

(Examples 1 to 5 and Comparative Examples 1 and 2) In Examples 1 to 5 and Comparative Examples 1 and 2, a charge generation layer and a charge transport layer were formed on a conductive substrate 1 composed of a cylindrical aluminum drum. In producing a laminated electrophotographic photoreceptor in which a charge transport layer was formed, a case in which a coating liquid for forming a charge transport layer film was applied on the conductive substrate 1 on which the charge generation layer was formed was examined.

In Examples 1 to 5 and Comparative Examples 1 and 2, 100 parts by weight of a charge transport material composed of a hydrazone compound and 100 parts by weight of a polycarbonate resin were used as the coating liquid 2 for forming a film. Using a charge transport layer coating solution dissolved in a mixed solvent obtained by mixing an equal amount of dioxane and dioxane, the viscosity of the charge transport layer coating solution was 180 cp in Examples 1 to 3 and Comparative Examples 1 and 2. Example 4
In this case, the adjustment was made to be 220 cp, in Example 5 to be 250 cp, and in Example 6 to be 170 cp.

A supply pipe 17 having a diameter of 22 mm in each of the dip coating apparatuses described above was used as a filter 19.
In addition to using a filter material having a mesh size of 30 μm, in Examples 1 to 5, the return pipe 24 having a diameter of 5.5 mm was used.

The flow rate of each of the charge transport layer coating liquids supplied to the immersion tank 10 by the pump 18 was 1800 c in Examples 1, 4 to 6 and Comparative Examples 1 and 2.
c / min, 2200 cc / mi in Example 2
n, in Example 3, the coating liquid for each charge transport layer was applied to the immersion tank 10 and the tank 1 at a rate of 2500 cc / min.
4 and each immersion tank 10 every 3 hours.
The presence or absence of bubbles in the interior was visually observed.

As a result, in Examples 1 to 6 above, no air bubbles were generated even after 24 hours had elapsed, but in Comparative Examples 1 and 2, the fourth 1
In the observation at the time when 2 hours had passed, no bubbles were generated, but when the fifth observation was performed at the time when 15 hours had passed, bubbles were generated, and bubbles were generated in the immersion tank 10 between 12 and 15 hours. There has occurred.

As described above, in the case of Examples 1 to 6 in which the filter 19 provided in the supply pipe 17 for sending the coating liquid for the charge transport layer from the tank 14 to the immersion tank 10 is connected to the tank 14 by the return pipe 24. The bubbles mixed in the charge transport layer coating liquid are returned to the tank 14 through the return pipe 24, and the charge transport layer coating liquid without bubbles is stably supplied to the immersion tank 10. When the conductive substrate 1 is immersed in the immersion tank 10 to apply the charge transport layer coating liquid, there is no occurrence of uneven application of the charge transport layer coating liquid on the conductive substrate 1.

On the other hand, in the case of Comparative Examples 1 and 2 in which the above-mentioned return pipe 24 is not provided, bubbles mixed in the charge transport layer coating liquid gradually accumulate during circulation or the like, and It is supplied to the immersion tank 10,
When the conductive substrate 1 is immersed in the immersion tank 10 to apply the charge transport layer coating liquid, the air bubbles adhere to the surface of the conductive substrate 1 and the charge transport layer applied to the conductive substrate 1 is applied. Coating unevenness occurred in the layer coating solution.

[0035]

As described above in detail, in the dip coating apparatus of the present invention, a filter is provided in a supply pipe for supplying a coating liquid for film formation from a tank to a dip tank, and the coating liquid for film formation in the tank is provided. Since the filter and the tank are communicated by the return pipe when sending them to the immersion tank through the filter by the supply pipe, even if air bubbles are mixed in the coating liquid for film formation in the tank, these air bubbles will be removed from the filter. In the film forming coating liquid supplied to the immersion tank, the bubbles suppressed in the filter and thus suppressed in the filter are returned to the tank together with a part of the film forming coating liquid through the return pipe. Thus, a stable amount of the coating liquid for film formation came to be supplied from the tank to the immersion tank through the supply pipe without being mixed with air bubbles.

As a result, in the dip coating apparatus according to the present invention, when the conductive substrate is immersed in the coating liquid for film formation in the dip tank and the coating liquid for film formation is applied to the conductive substrate, bubbles are generated. Does not adhere to the surface of the conductive substrate to cause unevenness in application of the coating liquid for film formation on the conductive substrate, and the coating liquid for film formation is uniformly applied to the conductive substrate. An electrophotographic photoreceptor having excellent characteristics has been obtained.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of a conventional dip coating apparatus.

FIG. 2 is a schematic explanatory view of a dip coating apparatus according to an embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 conductive substrate 2 coating liquid for film formation 10 immersion tank 13 guide tube 14 tank 17 supply tube 19 filter 24 return tube

Claims (1)

[Claims] An immersion tank for containing a coating liquid for film formation and immersing the conductive substrate to apply the coating liquid for film formation to the conductive substrate; and a tank for storing the coating liquid for film formation. A guide pipe for guiding the film-forming coating liquid from the immersion tank to the tank and a supply pipe for supplying the film-forming coating liquid from the tank to the immersion tank are provided, and the supply pipe is supplied from the tank to the immersion tank. A dip coating device provided with a filter through which a coating liquid for forming a film is passed, wherein the filter and the tank are connected by a return pipe.