JPH03118874A - Dip coating method - Google Patents

Abstract

PURPOSE:To prevent a liquid level from falling by immersing the remaining half number of cylindrical base bodies at the same speed as the speed at which the cylindrical base bodies are pulled up from a coating tank. CONSTITUTION:The coating tank consists of the two coating tanks 3a, 3b which are connected by a pipe 30 in the lower part thereof. Flow regulating plates 5a, 5b are provided in the part of the pipe 30. Holding parts 2a, 2b of a lifting device hold the cylindrical base bodies 1a, 1b. These holding parts 2a, 2b can be respectively discretely moved upward and downward. While the cylindrical base bodies 1b are immersed in the coating tank 3b, the cylindrical base bodies 1a of the same number are immersed into the coating tank 3a in synchronization with the speed at which the cylindrical base bodies 1b are pulled up from the coating liquid 3b. The uniform coated films are thus formed without generating unequal coating.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Field of Application This invention relates to a dipping method in which a plurality of cylindrical substrates are immersed in a coating liquid in a coating tank and then pulled up to form a coating film on the surface of the cylindrical substrates. Regarding the coating method.

(b) Prior Art One method for forming a layer of a material different from that of the substrate on the surface of the substrate is to immerse the substrate in a coating tank containing a coating liquid and then pull it up.

FIG. 3 is a diagram illustrating a conventional dip coating method.

Figure (A) shows the state in which the cylindrical substrate is completely immersed in the coating liquid in the coating tank. A cylindrical substrate 1 is held by a holding part 2 of a lifting device (not shown), and is immersed into a coating tank 3 in which a coating liquid 4 is stored. A saucer 31 is provided at the top of the coating tank 3 to receive the coating liquid that overflows when the coating tank 3 is immersed.
A return pipe 32 is connected to 1 to recover the overflowing coating liquid to a stirring tank unit (not shown). A pipe 33 for supplying and recovering the coating liquid is installed at the bottom of the coating tank. The same figure (B
) represents a state in which the lifting device is lifting up the cylindrical base 1. Cylindrical substrate 1 lifted from the coating liquid
A coating film 41 is formed on the surface. (C) shows a state in which the lifting device has completely lifted up the cylindrical substrate and coating has been completed.

A coating film 41 is formed on the surface of the cylindrical substrate that has been pulled up.

Furthermore, in mass production lines, a method is usually adopted in which a plurality of coating tanks are lined up and a lifting device holds and coats a plurality of cylindrical substrates at once.

(C1 Problem to be Solved by the Invention However, the above coating method had the following drawbacks.

When the cylindrical substrate is lifted out of the coating tank, the liquid level decreases in the coating tank by the volume of the cylindrical substrate (including the internal space), so the inner wall of the coating tank is coated with parts (B) and ( in Figure 2). A portion 42 to which the coating liquid has adhered is formed as shown in C). The solvent in the adhered coating liquid easily evaporates and forms aggregates, which are mixed into the coating liquid. Since this causes uneven coating, it was not possible to form a uniform coating film.

Furthermore, when coating cylindrical substrates with different diameters in the same coating tank, the drop in the liquid level that occurs when the cylindrical substrate is pulled up is due to the diameter of the cylindrical substrate (the rate of drop in liquid level is related only to the diameter of the size). ). Therefore, the rate at which the level of the coating liquid in the coating tank decreases due to lifting differs depending on the diameter of the cylindrical substrate. Therefore, in consideration of this, it is necessary to change the coating speed (pulling speed) of the cylindrical substrate depending on the diameter, which is complicated and has extremely poor operability.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a dip coating method in which the coating liquid in a coating tank always maintains a substantially constant liquid level, and the liquid level does not drop.

(d) Means for Solving the Problems In the dip coating method of the present invention, of a plurality of cylindrical substrates of the same size to be coated, half of the cylindrical substrates are first coated with a coating liquid. immersing the plurality of cylindrical substrates in a tank, and then, when pulling up the half of the cylindrical substrates from the coating tank, immersing the remaining half of the plurality of cylindrical substrates in the coating tank at the same speed as the lifting speed. It is characterized by going.

(e) Effect In the dip coating method according to the present invention, when a plurality of cylindrical substrates of the same size are coated simultaneously, half of the cylindrical substrates of the plurality of cylindrical substrates are first immersed in the coating liquid in the coating tank. Soak,
Thereafter, when half of the immersed cylindrical substrates are pulled up, the remaining half of the plurality of cylindrical substrates are immersed into the same coating tank at the same speed as the lifting speed. Since the multiple cylindrical substrates are all the same size as well as the diameter, the volume of the cylindrical substrate that comes out of the coating liquid after being pulled up is equal to the volume of the cylindrical substrate that is immersed in the coating liquid and is pulled up. The drop in the liquid level caused by this and the rise in the liquid level caused by immersion cancel each other out, so that the liquid level always remains at a nearly constant height and no drop in the liquid level occurs. Therefore, the inner wall of the coating tank is not exposed with the coating liquid attached, and no aggregates are formed.

Furthermore, since the liquid level does not drop, there is no need to consider the rate of drop in the liquid level when setting the coating speed, and cylindrical substrates of any diameter can be coated at the same speed.

(fl Embodiment FIG. 1 is a diagram for explaining the outline of a dip coating method that is an embodiment of the present invention. The same parts as in FIG. 2 are denoted by the same numbers and the explanation will be omitted.

In this embodiment, there are two cylindrical substrates.

As shown in the figure, the coating tank consists of two coating tanks 3a and 3b, which are connected by a vibrator 30 at the bottom. Current plates 5a and 5b are provided at the pipe 30 portions of the coating tanks 3a and 3b. Holding parts 2a and 2b of a lifting device (not shown) hold cylindrical base bodies 1a and 1b, respectively, and the holding parts 2a and 2b can be raised and lowered separately.

Figure (A) shows a state in which the cylindrical substrates 1b (half of the substrates) are completely immersed in the coating tank 3b. In this state, both coating tanks 3a and 3b are filled with the coating liquid 4. Thereafter, the cylindrical substrate 1b is lifted from the coating tank 3b, and the cylindrical substrate la (the remaining half of the substrates) is immersed into the coating tank 3b.

The figure (B) shows a state in which the cylindrical substrate 1b is half lifted from the coating tank 3b and the cylindrical substrate 1a is half immersed in the coating tank 3a. Since the pulling speed of the cylindrical substrate 1b and the dipping speed of the cylindrical substrate 1a are the same, the volume reduction due to pulling up the cylindrical substrate 1b is equal to that of the cylindrical substrate 1a which is immersed in the coating tank 3a at the same speed. The increase in volume flows through the pipe 30 to the coating tank 3b and is offset, thereby preventing a drop in the liquid level in the coating tank 3b. Ripples on the liquid surface of the coating liquid due to the flow of the coating liquid from one coating tank to another are caused by a rectifier plate 5a,
5b. Note that a coating film 41 is formed on the cylindrical substrate 1b that has been pulled up, and the coating liquid decreases by that amount, but it is a very small amount compared to the entire coating liquid, and the coating film 41 is
It can be said that the liquid level of the coating liquid is kept constant in both cases a and 3b.

Figure (C) shows a state in which the cylindrical substrate 1b has been completely pulled up from the coating tank 3b, and the cylindrical substrate 1a has been completely immersed in the coating tank 3a. Due to the same principle as in the case shown in FIG. 5(B), the liquid level does not drop and remains constant. Therefore,
The inner wall surface of the coating tank is not exposed, no agglomerates of the coating liquid are generated, and a uniform coating film can be formed without uneven coating.

In addition, when coating cylindrical substrates of any size, since the multiple cylindrical substrates are all the same size, there is no drop in the liquid level in the coating tank, and there is no need to change the coating speed depending on the diameter. Improved operability.

In the dip coating method of this embodiment, the same number of coating tanks as the substrates were connected by pipes, and the connection part was located at the bottom, but it may be provided at the middle, the top, or at multiple locations. Also,
Instead of a plurality of connected coating tanks, a coating tank as shown in FIG. 2 can also be used. That is, the plurality of coating tanks 3C and 3d are connected as a whole to form substantially one coating tank. In this case, in order to prevent the liquid surface from undulating due to the cylindrical substrates immersed in the coating tanks 3C and 3d,
A current plate 5 is provided between the coating tanks 3C and 3d.

Note that when switching the cylindrical substrate to be coated to a cylindrical substrate of a different size, a drop in the liquid level is prevented by using dummy substrates of the same size first and last.

(Effects of the Button Invention As described above, according to this invention, in order to simultaneously coat a plurality of cylindrical substrates of the same size, first half of the cylindrical substrates are immersed in the coating liquid in the coating tank, and then When half of the immersed cylindrical substrates are pulled up, the other half of the cylindrical substrates are dipped into the same coating tank at the same speed as the lifting speed.For this reason, they are pulled up and out of the coating liquid. The volume of the cylindrical substrate becomes equal to the volume of the cylindrical substrate immersed into the coating liquid.In other words, the drop in the liquid level due to lifting and the rise in the liquid level due to immersion cancel each other out, causing the liquid level to drop. First, the inner wall of the coating tank is not exposed with the coating liquid attached to it, and no aggregates are formed.Therefore, a uniform coating film can be formed without uneven coating.

Furthermore, there is no need to consider the rate of drop in the liquid level, and a plurality of cylindrical substrates of any diameter can be coated at the same speed, thereby improving operability.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating a dip coating method according to an embodiment of the present invention. Figure (A) shows a state in which one cylindrical substrate is completely immersed. Figure (B) shows a state in which one cylindrical substrate is half lifted out of the coating tank, and the other cylindrical substrate is half immersed in the coating tank. The same figure (C
) represents a state in which one cylindrical substrate is completely lifted out of the coating tank and the other cylindrical substrate is completely immersed in the coating tank. FIG. 2 is a schematic diagram of a modified example of a coating apparatus for carrying out the same dip coating method. Figure 3 (A) (B), (C
) is a diagram illustrating an outline of a conventional dip coating method. 1a, 1b - cylindrical substrate, 2a, 2b - holding part of the lifting device, 3a, 3b - coating tank, 4 - coating liquid, 5.5a, 5b - rectifier plate.

Claims (1)

[Claims] (1) Among multiple cylindrical substrates of the same size to be coated, half of them are first immersed in a coating tank containing a coating liquid, and then half of the cylindrical substrates are coated. A dip coating method characterized in that, when the cylindrical substrates are pulled up from the tank, the remaining half of the plurality of cylindrical substrates are dipped into the coating tank at the same speed as the pulling speed.