JPS6252631B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for applying a coating liquid to the surface of a substrate such as various lenses and reflecting mirrors by a draining method.

Conventionally, resin solutions with specific properties have been used as coating liquids to improve surface hardness, provide weather resistance, and provide antifogging properties to the surfaces of glass or plastic substrates such as eyeglass lenses, prisms, and medical parts. A coating film is formed by applying it to the surface of the material and baking it.

There are various methods for applying the coating liquid to the surface of the substrate, such as brush coating, roller coating, spray coating, electrostatic coating, flow coating, barrel coating, and dipping coating. It is widely used because of its excellent adaptability to shapes.

In conventional dip coating, the substrate is immersed in a tank filled with coating liquid and then pulled up or the tank itself is lowered, so there is no impact from vibrations when raising the substrate or lowering the tank. In this case, micro-movements are transmitted to the contact interface between the substrate and the coating liquid, which causes surface defects in the coating film and has various disadvantages.

For this reason, the applicant proposed a drain-type dip coating in Japanese Patent Publication No. 55-3019. As shown in Fig. 1, the apparatus for performing this dip coating has a sub-tank 2 disposed below a main tank 1 that performs the coating process, and a drain pipe 3 for the coating liquid is connected to the bottom of the main tank 1. The lower end of the liquid drain pipe 3 faces into the sub-tank 2, and a valve 4 and an opening/closing knob 5 are provided in the middle part of the liquid drain pipe 3 to adjust the discharge amount of the coating liquid.
has been established.

Then, with the opening/closing pot 5 closed, the main tank 1 is filled with the coating liquid 6, and the opening degree of the valve 4 is adjusted, and then the base material 7 is immersed in the main tank 1. Then, by opening the opening/closing pot 5, liquid is gradually drained from the main tank 1 to the sub tank 2, and along with this, the coating liquid 6 is applied to the surface of the base material 7.

However, in such a liquid drain type coating device, in order to obtain a uniform coating film with a predetermined thickness, it is necessary to reduce the rate of drop of the liquid level to, for example, about 2 cm/min. As a result, a stagnant portion of the coating liquid is generated in the main tank 1, causing liquid separation, which causes surface defects. Furthermore, if there are air bubbles mixed in the coating liquid that cause uneven film thickness or stripes, there is a problem that the air bubbles cannot be easily removed because the coating liquid has a high viscosity.

The present invention has been achieved in order to improve the above-mentioned conventional problems, and its purpose is to make the coating liquid in the main tank for coating the substrate homogeneous and free of air bubbles. To provide a liquid-draining coating device capable of uniformly applying a coating liquid to the surface of a substrate.

In order to achieve the above object, a liquid drain type coating device according to the present invention includes a main tank for coating a substrate, and a sub tank disposed below the main tank and having a cooling part for a (thermosetting) coating liquid. and an extension wall extending vertically from the side wall of the main tank toward the sub-tank in order to cause the coating liquid overflowing from the main tank to flow down into the sub-tank, and supplying the coating liquid to the bottom of the main tank so as to flow down into the sub-tank. A supply pipe that raises the liquid level in the main tank and a drain pipe that coats the substrate while lowering the liquid level in the main tank are provided, and the liquid drain pipe is connected to a sub-tank, and a filter and a first opening/closing cock are installed at the bottom of the sub-tank. A coating liquid discharge pipe is provided which communicates with the supply pipe through the coating liquid discharge pipe, and the sub tank is branched from the upstream side of the first opening/closing socket of the coating liquid discharge pipe, and is connected to the sub tank via a second opening/closing socket which operates in reverse to the first opening/closing socket. The gist of this is the provision of circulation piping connected to the bottom.

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 2 is a cross-sectional view showing the schematic structure of the coating device according to the present invention, and shows the coating device 10.
The main tank 11 is arranged at the top. As shown in the plan view of FIG. 3, this main tank 11 has a substantially rectangular shape in plan, and grooves 12 are formed at the four corners of the upper end and in the middle part thereof, and the main tank 11 is formed inside the main tank 11. A float switch 14 is provided to detect the liquid level of the coating liquid 13 inside.

Further, a hakama-shaped extension wall portion 15 is integrally provided vertically so as to surround the side wall 11a of the main tank 11. The upper end of this extension wall 15 is aligned with the lower end of the groove 12 or is located slightly below. Then, a valve 1 extends outward from a corner slightly above the lower end of the main tank side wall 11a.
6 is provided, and the lower end of this sub-liquid drain pipe 17 is bent so as to be close to the surface of the extension wall 15.

Further, a sub tank 18 is arranged below the main tank 11. The lower part of the extension wall 15 is visible inside the sub-tank 18, and the extension wall 15 serves as a partition wall that divides the inside of the sub-tank 18 into an outer chamber 19 and an inner chamber 20. The outer chamber 19 and the inner chamber 20 communicate with each other through the lower end of the extension wall 15 and the bottom of the sub-tank 18.
A partition member 21 such as a wire netting having a mesh size of 200 to 200 meshes, preferably 50 to 100 meshes, is fixedly attached to the lower end of the hakama-like wall portion 15. The partition member 21 allows the coating liquid 13 to pass through, but does not allow air bubbles mixed in the coating liquid 13 to pass through.

Also, the coating liquid 13 is contained in the sub-tank 18.
The temperature is lowered by a chiller 22, which is a cooling member, to keep the viscosity constant. Furthermore, a coating liquid replenishment part 23 is provided on the outside of the sub-tank 18.
is attached.

A liquid drain pipe 24 for the coating liquid is connected to the bottom of the main tank 11, and this liquid drain pipe 24 is branched in the middle, and a liquid drain adjustment valve 25 is connected to one pipe 24a, and a rapid liquid drain pipe 24 is connected to the other pipe 24b. A vent valve 26 is provided, and each pipe 24a, 2
4b is connected to the supply section 23. A coating liquid discharge pipe 27 is connected to the bottom of the inner chamber 20 of the sub-tank 18, and a pump 29 driven by a motor 28 takes out the coating liquid through the discharge pipe 27. The pipe 32 from the filter 30 is further branched in the middle, and a circulation pipe 34 is provided with an opening/closing socket 33 as a first opening/closing socket in the middle of one pipe.
The other pipe is connected to the bottom of the main tank 11 as a coating liquid supply pipe 37 with a second opening/closing knob 35 and a check valve 36 interposed in the middle. And coating liquid supply pipe 3 to main tank 11
A wire mesh 38 is provided at the connection part of 7, and the main tank 1
This prevents the liquid level in 1 from fluctuating.

Coating device 10 having the above configuration
The effect of this will be explained below.

First, a base material is suspended and supported in the main tank 11 which is not filled with coating liquid. Next, the opening/closing pot 33 is closed, the opening/closing pot 35 is opened, and the coating liquid is supplied into the main tank 11 via the supply pipe 37. Then, the liquid level of the coating liquid 13 in the main tank 11 gradually rises, and eventually overflows from the upper end of the main tank 11, flows down the surface of the extension wall 15, and flows into the outer chamber 19 in the sub-tank 18. accepted. At this time, by making the extension wall 15 substantially vertical, it is possible to suppress bubbles generated when the coating liquid in the sub-tank 18 and the coating liquid flowing down the extension wall 15 mix.

Since the coating liquid in the inner chamber 20 of the sub-tank 18 is discharged from the discharge pipe 27 by the pump 29, the coating liquid flows from the outer chamber 19 into the inner chamber 27 via the communication portion. At this time, since a partition member 21 such as a wire mesh that does not allow air bubbles to pass through is provided in the communication portion, the coating liquid in the inner chamber 20 does not contain air bubbles.

Then, after overflowing from the upper end of the main tank 11 for a while to complete the uniformity of the coating liquid 13 in the main tank 11 and the discharge of air bubbles, the liquid drain adjustment valve 25 is opened by a predetermined amount.
The coating liquid is discharged from the bottom of the main tank through a drain pipe 24.

At the same time, the opening/closing knob 33 is opened and the opening/closing knob 35 is closed to stop supplying the coating liquid. Then, the liquid level of the coating liquid gradually falls, and as it does so, a constant thickness of the coating liquid is applied to the surface of the substrate. At this liquid draining stage, the valve 16 of the sub-liquid drain pipe 17 provided at the corner of the bottom of the main tank 11 is always open, so the coating is applied to the corner inside the main tank 11. The liquid does not stagnate and liquid separation can be prevented.

When the float switch 14 senses that the coating liquid level has further fallen and passed the lower end of the substrate, the rapid liquid drain valve 26 is opened to drop the coating liquid in the main tank 11.

FIG. 4 shows another embodiment, in which a main tank 41 is surrounded by an overflow wall 42, a sub-tank 43 is arranged below one side of the main tank 41, and an extension wall 44 of the main tank 41 is provided.
is made to become the inner wall of the sub tank 43.

A partition wall 45 faces the inside of the sub-tank 43 from above, and the inside of the sub-tank 43 is divided into an outer chamber 46 and an inner chamber 47. A partition member 48 such as a wire mesh is provided on the lower end wall of the partition wall 45, and the coating liquid is 13 flows into the outer chamber 46 from the inner chamber 47, air bubbles are prevented from entering the outer chamber 46.

A coating liquid drain pipe 49 is led out from the lower end of the side wall of the main tank 41, and this liquid drain pipe 49 is connected to a liquid replenishment part 50 provided inside the sub-tank 43. The inner chamber 47 is connected to the inner chamber 47 by a connecting pipe 51.
On the other hand, the coating liquid in the outer chamber 46 from which air bubbles have been removed is sucked by a pump 53 through a discharge pipe 52 connected to the bottom of the outer chamber 46, and is sent out from the pump 53 through a filter 54 through a pipe 55. The pipe 55 branches into pipes 56 and 57 in the middle, while the main tank 56 serves as a coating liquid supply pipe equipped with an opening/closing cock 58 and a check valve 59.
1 and the other 57 is connected to the outer chamber 46 of the sub-tank 41 as a liquid return pipe equipped with an opening/closing knob 60.
Connected to the bottom.

The functions of the coating apparatus having the above-mentioned structure are substantially the same except that the functions of the outer chamber 46 and inner chamber 47 of the sub-tank 43 are reversed from those of the previous embodiment.

That is, after the base material is suspended in the main tank 41 and exposed, the opening/closing pot 58 is opened, and the opening/closing pot 6 is opened.
0 is closed, and the coating liquid is supplied into the main tank 41 by the pump 53. After the coating liquid overflows from the main tank 41, the opening/closing pot 58 is closed, the opening/closing pot 60 is opened, and at the same time, the valve of the coating liquid drain pipe 49 is opened by a predetermined amount to drain the liquid. As the liquid level of the coating liquid falls due to this draining, the coating liquid is applied to the surface of the substrate.

As is clear from the above description, according to the present invention, an extension wall is integrally hung from the side wall of the main tank, and this extension wall faces the inside of the sub-tank, so that the supply is first supplied into the main tank. Although bubbles are likely to be included in the coating liquid, the coating liquid containing these bubbles can be removed by overflowing from the top of the main tank, and the overflowing coating liquid can be removed by a wall extending from the side wall of the main tank. Since it is made to flow down into the sub-tank, air bubbles are not generated when it flows down, and the thermosetting coating liquid in the sub-tank is cooled by the cooling section provided in the sub-tank, and the coating liquid is circulated through the discharge pipe by opening the second opening/closing pot. The viscosity can be maintained constant by circulating the coating liquid through the supply pipe, and this coating liquid can be supplied to the main tank by opening the first opening/closing point of the supply pipe that branches from the middle of the discharge pipe. It has many advantages, such as being able to uniformly apply the coating liquid to the surface and preventing surface defects from occurring even during subsequent baking.

[Brief explanation of the drawing]

The drawings show an example of the implementation of the present invention and a conventional example, and FIG. 1 is a cross-sectional view of a conventional liquid-draining coating apparatus, FIG. 2 is a cross-sectional view of a liquid-draining coating apparatus according to the present invention, and FIG. 3 is a plan view of the same coating device, and FIG. 4 is a sectional view of another embodiment. In the drawing, 11 and 41 are the main tank, 13 is the coating liquid, 15 and 44 are the extension wall parts, 18,
43 is a sub tank, 21 and 48 are partition members, 2
4, 49 are coating liquid drain pipes, 37, 5
6 is a coating liquid supply pipe, and 45 is a partition wall.

Claims (1)

[Scope of Claims] 1. A main tank for coating a substrate, a sub-tank disposed below the main tank and having a coating liquid cooling section, and a coating liquid overflowing from the main tank flowing into the sub-tank. an extension wall extending vertically from the side wall of the main tank toward the sub-tank; a supply pipe for supplying coating liquid to the bottom of the main tank to raise the liquid level in the main tank; A liquid drain pipe is provided for coating the substrate while descending the surface, the liquid drain pipe is connected to a sub-tank, and a coating liquid discharge pipe is connected to the supply pipe via a filter and a first opening/closing cock at the bottom of the sub-tank. In addition, a circulation pipe is provided which branches from the upstream side of the first opening/closing socket of the coating liquid discharge pipe and connects to the bottom of the sub-tank via a second opening/closing socket that operates in reverse to the first opening/closing socket. A liquid-draining coating device. 2. Claim 1, wherein the extension wall portion also serves as a partition wall for partitioning the inside of the sub-tank.
The liquid-draining coating device described in Section 1. 3. The liquid drain type coating device according to claim 2, wherein the partition wall has a partition member at a lower end that allows the coating liquid to pass through but does not allow air bubbles to pass through.