JPH03109962A - Immersion coating applicator - Google Patents

Abstract

PURPOSE:To prevent generation of bubbles by providing a recovery chamber of prescribed size to the outer periphery of the upper part of an application tank and circulating application liquid to the application tank from the recovery chamber by a circulating means of application liquid and lowering the head drop of both the upper end of application liquid and the liquid surface of applica tion liquid in the recovery chamber. CONSTITUTION:The material 13 to be applied is supported by the supporting means 9-11 so that the material 13 to be applied is moved to the upper and lower directions and can be inserted into an application tank 1. Further applica tion liquid is recovered by a recovery chamber 2 provided to the outer periphery of the upper part of the application tank 1. Furthermore the application liquid recovered in the recovery chamber 2 is circulated to the bottom part of the application tank 1 by the circulating means 5-8. The recovery chamber 2 is constituted so that it has bottom area not smaller than two times the bottom area of the application tank 1. The head drop of both the upper end of applica tion liquid in the application tank 1 and the liquid surface of application liquid in the recovery chamber is made small. As a result, a bubble removing mecha nism is not provided and generation of bubbles is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a dip coating device that immerses an object to be coated in a coating solution and then pulls it up for coating. This invention relates to a dip coating device that minimizes troubles caused by air bubbles.

BACKGROUND OF THE INVENTION Various devices have been known for applying a coating liquid to an object to be coated, such as a cylindrical body. In particular, when the smoothness of the coating film is important, such as for electrophotographic photoreceptors, dip coating is used. The device is in use.

Generally, in a dip coating apparatus, the object to be coated is immersed in a coating liquid, and then the object is pulled up at an appropriate speed to perform coating.

In this case, for example, as described in Japanese Utility Model Application Publication No. 59-90667, it is possible to provide a coating liquid recovery tank for recovering the coating liquid separately from the coating tank and to continuously circulate the coating liquid. Preferably, this effectively achieves the objectives of preventing fluctuations in the liquid level in the coating tank, making the composition of the coating liquid uniform, and preventing the surface of the coating liquid on the coating tank from becoming dirty.

FIG. 5 is a schematic configuration diagram of a conventional dip coating device,
The object 13 to be coated is immersed in the coating liquid 3 in the coating tank 1 to be coated. The object to be coated is supported by a support 10 and a support arm 1 so as to be moved up and down by a motor 12 and a ball screw 9.

Further, the coating liquid is supplied to the coating tank 1 by the pump γ and pipes 5 and 6. The coating liquid overflowing from the upper end of the coating tank is returned to the coating liquid recovery tank 17 from the gutter 15 through the guide pipe 16.

In the conventional dip coating apparatus shown in FIG. 4, when the coating liquid enters the coating liquid recovery tank 17 from the guide tube 16, the coating liquid outlet of the guide tube 1B is located at the upper part of the coating liquid recovery tank. Therefore, there was a problem that air bubbles 18 were generated in the coating liquid by flowing down.

If air bubbles are mixed into the coating solution, they will continue to circulate without disappearing, causing defects such as repellency, sagging, bubbles, and floating in the formed coating film.

Various proposals have been made in the past for the purpose of preventing the generation of bubbles. For example, Japanese Utility Model Application Publication No. 60-1.07952 describes that a barrier is provided at a position where the coating liquid flows down.

Furthermore, JP-A No. 59-1.95243 describes that vertically extending partition walls with gaps are arranged alternately in the liquid reservoir (coating liquid collection tank) in order to remove air bubbles. Japanese Unexamined Patent Publication No. 59-195244 describes that a 20 to 80 mesh filter for removing air bubbles is arranged in a liquid reservoir in a direction transverse to the liquid flow.

Furthermore, Japanese Patent Application Laid-open No. 716ft9 discloses that the interior of the coating tank is separated into an inner coating chamber and an outer collection chamber by a partition wall, and a double-layered structure is used to guide paint overflowing over the top of the coating tank to the recovery chamber. A dip coating apparatus having a structured coating tank has been proposed.

Problems to be Solved by the Invention However, when a barrier is provided at the position where the coating liquid flows down as described in Utility Model Application Publication No. 07952, the force of the falling flow is weakened and bubbles are not mixed in. Although it is quite effective, the flow down from the barrier again occurs and therefore, when the viscosity of the coating liquid is low, when foaming occurs.1]-.

The functionality was not sufficient. Also, JP-A-59-19
In the cases described in No. 5243 and Japanese Unexamined Patent Publication No. 59-1.95244, the structure of the dip coating device used becomes complicated, and in the case of a coating liquid with high viscosity, the coating liquid may stagnate. There was a problem that the amount increased and caused problems with circulation.

Furthermore, JP-A-1. In the case described in Japanese Patent No. 1.71669, there was a problem in that as the amount of the coating liquid decreased, the head of the coating liquid overflowing from the upper end of the coating chamber and flowing down became larger, resulting in the generation of bubbles.

Therefore, the conventional technology is not yet sufficient as a technology for preventing the generation of bubbles, and there has been a demand for the development of a dip coating apparatus equipped with a circulation mechanism that can fundamentally prevent the generation of bubbles. The present invention has been made in view of the above-mentioned problems in the conventional technology.

Accordingly, an object of the present invention is to provide a dip coating apparatus having a simple structure and provided with a circulation mechanism that does not generate bubbles.

Means to Solve the Problem The inventors of the present invention have proposed that the generation of air bubbles can be solved by circulating the coating liquid between the coating tank and a coating liquid recovery tank provided separately from the coating tank, or by applying the liquid from the top of the coating tank. Considering that the cause is that the liquid flows down with a considerable head, it is possible to achieve the above objective by not providing a coating liquid recovery tank and by providing a recovery chamber that does not cause much head. We have discovered what we can do, and have completed the present invention.

The dip coating apparatus of the present invention includes an object support means for supporting an object to be coated so that it can be moved vertically and inserted into a coating tank, a coating tank, and a coating liquid provided on the outer periphery of the upper part of the coating tank. The collection chamber has a bottom area that is at least twice the bottom area of the coating tank. It is characterized by having.

In the dip coating apparatus of the present invention, it is preferable to provide a coating liquid supply device in communication with the coating liquid circulation means and at the same height as the recovery chamber.

Function: In the dip coating tank of the present invention, the coating liquid is supplied from the bottom of the coating tank. Coating is performed by immersing the object to be coated, supported by the object-to-be-coated support means, into the coating liquid in the coating tank and pulling it up.

At this time, the coating liquid overflows from the upper end of the coating tank and flows down into a recovery chamber provided on the outer periphery of the upper part of the coating tank.

That is, the coating liquid overflows from the entire periphery of one end and flows down along the outer wall of the coating tank. At this time, since the bottom of the recovery chamber is located above the bottom of the coating tank, the head of the coating liquid overflowing and flowing down is small, and the generation of bubbles is reduced.

At that time, if a coating liquid supply device is installed in communication with the coating liquid circulation means and at the same height as the recovery chamber, the coating liquid in the recovery chamber can be removed by supplying paint to the coating liquid supply device. It becomes possible to adjust the liquid level and therefore
This makes it possible to bring the liquid level of the coating liquid at one end of the coating tank and in the recovery chamber to approximately the same level.

The coating liquid that has fallen into the recovery chamber is returned to the bottom of the coating tank by a coating liquid circulation means that includes a fluid transfer device such as a pump and piping for circulation.

Example Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a schematic configuration of a dip coating apparatus of the present invention, and FIG. 2 is a diagram showing a state in which an object to be coated is immersed in a coating liquid.

In the figure, ■ is a cylindrical coating tank, and the coating liquid 3 is filled inside. A cylindrical collection chamber 2 is provided outside the upper part of the coating tank. This recovery chamber has a bottom area that is at least twice as large as the bottom area of the coating tank, and is arranged so that the bottom surface of the recovery chamber is approximately 1/2 the height of the coating tank from the top of the coating tank. It is set up. A lid 4 having a circular opening in the center is placed over the coating tank and recovery chamber. A pipe 5 for circulating the collected coating liquid is installed at the bottom of the recovery chamber 2. On the other hand, at the bottom of the coating tank 1,
Piping 6 for introducing the circulating coating liquid into the coating tank is installed, and these pipings are connected by a pump 7.
It constitutes a coating liquid circulation means. Note that 8 is a filter provided in the pipe 6. This filter is provided as necessary.

On the other hand, the means for supporting the object to be coated includes a support tool 10, a support arm 1
1 and a ball screw 9, a cylindrical object to be coated 1
3 is supported so that it can be moved vertically and immersed in the coating liquid in the coating tank. Note that 12 is a motor for rotating the ball screw.

In the above-mentioned dip coating apparatus, by driving the motor 12 and rotating the ball screw 9, the object to be coated 13 supported by the support 10 is lowered from above the coating tank, as shown in FIG. , is immersed in the coating liquid 3 in the coating tank 1. Next, coating is performed by pulling up the object to be coated at a predetermined speed. On the other hand, the coating liquid 3 is supplied to the pump 7
It is supplied to the bottom of the coating tank, overflows from the entire upper periphery, and flows down into the collection chamber 2 along the outer periphery. The coating liquid collected in the recovery chamber 2 is discharged from the pipe 5 and is returned to the bottom of the coating tank via the pipe 6 by driving the pump 7.

In the present invention, since the collection chamber has the above configuration,
There is little difference in head between the liquid level of the coating liquid that overflows from the upper end of the coating tank, falls down and is collected in the recovery chamber, and the upper end of the coating tank. When using the device of the present invention, this head is 4
It is preferable to maintain it within cm, and the smaller the head difference, the less bubbles will be generated.

Further, the liquid level in the recovery chamber rises and falls as the object to be coated is taken out and put in, and a coating film may be formed on the side wall of the recovery chamber accordingly. In the present invention, by providing the recovery chamber so that the bottom area of the recovery chamber is at least twice as large as the bottom area of the coating tank, fluctuations in the liquid level can be reduced, and
The amount of coating applied can be reduced.

FIG. 3 is a cutaway sectional view of another embodiment of the invention. In this embodiment, a coating liquid supply device 1 is installed in the middle of the pipe 5.
9 is provided, and by opening and closing the valve 20, the coating liquid 3 in the coating liquid supply device can be supplied. This coating liquid supply device also functions to adjust the liquid level of the coating liquid in the recovery chamber. That is, since the coating liquid supply device is provided at the same height as the recovery chamber, when the valve 20 is open, the coating liquid in the coating liquid supply device and
The liquid level will be almost the same as the coating liquid in the recovery chamber, so
When the liquid level of the coating liquid in the recovery chamber drops, supply the coating liquid into the coating liquid supply device and apply the coating liquid. +'i- The liquid level of the coating liquid in the supply device can be adjusted to a predetermined liquid level, and thereby the liquid level of the coating liquid in the recovery chamber can be adjusted to a predetermined liquid level.

FIG. 4 shows still another embodiment of the dip coating apparatus of the present invention, in which two barriers 14 are provided around the outer periphery of the coating tank. In this case, the coating liquid overflowing from one end of the coating tank is blocked by the barrier and its flow rate is weakened, so when using a coating liquid that has a low viscosity and tends to generate bubbles, suitable. In the figure, two barriers are provided, but the number can be set arbitrarily.

Effects of the Invention As described above, in the dip coating apparatus of the present invention, a collection chamber of a predetermined size is provided on the outer periphery of the upper part of the coating tank, and the coating liquid is coated from the collection chamber by the coating liquid circulation means. Because it is configured to circulate through the tank, the dip coating device itself has a very simple structure, and the drop between the top of the coating solution and the level of the coating solution in the recovery chamber is small, making it impossible to use conventional dip coating. It becomes possible to prevent the generation of air bubbles without providing a bubble removal mechanism for preventing the generation of air bubbles as in the device. Furthermore, since there is no need to provide a separate coating liquid recovery tank, there is also the advantage that the piping is purified. Therefore, the dip coating apparatus of the present invention is particularly suitable for use in forming electrophotographic photoreceptors.

[Brief explanation of drawings]

FIG. 1 is a block diagram illustrating the general structure of the dip coating apparatus of the present invention, FIG. 2 is an explanatory diagram illustrating the state in which the object to be coated is immersed, and FIG. 3 is the dip coating apparatus of the present invention. FIG. 4 is a cross-sectional view of a coating tank in another embodiment of the dip coating apparatus of the present invention, and FIG. 5 is a block diagram showing the general structure of a conventional dip coating apparatus. . 2 1... Coating tank, 2... Recovery chamber, 3... Coating liquid, 4
Lid, 5.6 Piping, 7 Pump, 8 Filter, 9 Ball screw, IC Support, 11 Support arm, 12 Motor, 13 Object to be coated, 14 Barrier, 15・Gutter,] 6... Guide pipe, 17. Coating liquid collection tank, I8... Air bubbles, 19. Coating liquid 1'' (supply device, 20...
·valve.

Claims (2)

[Claims] (1) An object support means that supports the object to be coated so that it can be moved vertically and inserted into the coating tank, a coating tank, and a recovery chamber provided on the outer periphery of the upper part of the coating tank to recover the coating liquid. , and a coating liquid circulation means for circulating the coating liquid collected in the recovery chamber to the bottom of the coating tank, and the recovery chamber has a bottom area that is at least twice as large as the bottom area of the coating tank. Dip coating equipment. (2) communicating the coating liquid supply device with the coating liquid circulation means;
2. The dip coating apparatus according to claim 1, wherein the liquid level of the coating liquid in the recovery chamber is adjustable.