JPH0649167B2 - Thin film coating method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention forms a thin film partially on a substrate in wet coating using a solution, particularly in the case of coating by a sol-gel method using a metal alkoxide as a starting material. Coating method and position suitable for coating.

[Conventional technology]

Conventionally, in wet coating for coating a substrate using a solution, a dipping method performed by immersing the substrate in the solution and pulling it up at a constant speed, a flow coating method in which the solution is poured from the top of the substrate and sales are expanded, Various methods are known, such as a roller coating method in which a substrate is conveyed by two lower rolls and a film is coated with a solution in contact with either one or both rolls.

[Problems to be solved by the invention]

However, when partially coating the substrate,
In the flow coating method and the roller coating method, it is practically impossible to mask unnecessary portions with a masking tape or the like, so first coat the entire surface and then remove the unnecessary portions in large quantities by etching or the like. In addition, it was extremely difficult to obtain a delicately controlled film thickness on the order of submicrons. The dipping method is said to be most effective for obtaining a film thickness on the order of submicrons, but since this method is immersed in a coating solution for a large substrate and then pulled up, the driving equipment becomes large and complicated, and handling is difficult. Not only is it difficult and costly, but when pulling up the substrate, the liquid level is unavoidable due to the vibration of the substrate itself, so horizontal stripes easily occur and it is difficult to form a thin film of uniform thickness. there were. In addition, in the case of partial coating, not only unnecessary parts on the coated surface of the substrate but also the entire back surface is masked, or after coating both the front and back surfaces of the substrate once, the entire back surface and unnecessary parts on the front surface are coated. It is necessary to remove the film by a method such as etching, which requires a lot of trouble.

In view of such a point, the applicant of the present invention has disclosed in Japanese Unexamined Patent Publication No. 1-04336.
However, the present invention is intended to provide a method and an apparatus which are capable of coating a homogeneous thin film having a desired thin film and particularly suitable for partially coating a substrate. To aim.

[Structure of Invention]

The method of the present invention is a method for coating a thin film in which a coating solution is brought into contact with a substrate such as plate glass or plastic to form a thin film in a state in which the opening surface of a processing tank having an opening on one side is in close contact with the substrate. The coating solution is put into the processing tank up to a predetermined level, and a part is overflowed from a small opening provided in the processing tank so that the level of the coating solution contacting the substrate is lowered.
Characterized by extracting the coating liquid at a predetermined speed,
As a device for carrying out this method, a holding device for holding the substrate vertically or inclined, and one side surface of which is opened in a shape matching the substrate, and a small opening is formed on the upper side of the non-open side surface And a coating liquid supply tank which is attached to the processing bath and has a surface including the small opening as one side surface, and a coating liquid supply tank which can be moved up and down, and the processing layer and the coating liquid supply layer. The bottom surface of which is communicated by a tube, or a holding device for holding the substrate vertically or inclined, and one side face is opened in a shape matching the substrate, and a small opening is formed on the upper side of the non-open side face. From the bottom of the processing tank, a processing tank provided with a processing tank, and a receiving tank attached to the processing tank and having a surface including the small opening as one side surface, and a supply tank for supplying the coating liquid to the processing tank. Provided recovery tank to withdraw computing solution above and below the respective processing tank, wherein the said treatment tank, what a structure of connecting the tube respectively through the valve.

[Work]

With the substrate stationary, a processing tank having a slightly larger area than the coated surface of the substrate and having one side opened in a shape matching the substrate is brought into close contact with the coated surface of the substrate.
In that state, the coating solution is poured to a level equal to or less than the maximum part of the surface to be coated to perform an action equivalent to dipping the substrate in the dipping method. It is possible to perform partial coating by performing an action equivalent to pulling up the substrate in the dipping method by extracting, and not only the handling of coating while the substrate is stationary is easy, but also the film thickness A thin film with a uniform thickness can be obtained by easy coating.

In this case, if the lid of the processing tank is provided, the contact with air is insufficient, so that the film surface immediately after coating is not sufficiently dried and the film thickness becomes uneven.

Further, in the case of Example 1 described later, it is difficult to extract the solution.

Therefore, it is necessary to keep the upper part of the processing tank open, and as a result, dust is mixed in the processing tank and floats on the upper part of the coating solution, or the organic solvent in the solution evaporates and the coating solution Since the film thickness becomes non-uniform due to the change in the concentration, a part of the coating solution is overflowed in the present invention to remove the suspended matter in the solution and reduce the change in the concentration.

〔Example〕

 Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 and FIG. 2 are schematic perspective views showing a coating apparatus in Example 1 and Example 2 of the invention, FIG. 3 is a perspective view showing a processing tank, and FIG. 4 is an overflow of a notch in the processing tank. It is a figure which shows a state.

Example 1 As shown in FIGS. 1 and 3, the present device has a holding device 2 for holding a substrate 1 such as a plate glass, one side face of which is opened in a shape matching the substrate 1, and the other side face and bottom face are closed. , A processing tank 4 in which a small opening 3 is formed by notching the upper portion of the side surface that is not open in a sawtooth shape, and a small opening 3 attached to this processing tank.
Receiving tank 5 having a side including a side surface as one side surface, and a lifting device 6
The coating liquid supply tank 7 is provided so as to be able to move up and down by the above, and the tube 8 for connecting the processing tank 4 and the coating liquid supply tank 7 together. The holding device 2 is composed of two arms 11 and 11 having a suction pad 9 and a stopper 10, and is rotated by a drive device 11.

Further, the processing tank 4 has a hollow double structure independent on the left and right sides and the bottom side so that the tube 13 can be evacuated, an elastic body 14 is provided in the contact portion with the substrate, and a rod 16 connected to the air cylinder 15 is provided. It is reciprocated back and forth due to the expansion and contraction of.

Next, a thin film coating procedure will be described.

The coating solution supply tank 7 containing an alkoxide solution (sol solution) prepared by adding a solvent such as isopropyl alcohol of titanium alkoxide, which is a main material, as the coating solution 17 is adjusted so that its liquid level is lower than the bottom surface of the processing tank 4. In the lowered state, the substrate 1 is the belt conveyor 1
Belt conveyor 18 when it is conveyed by 8 and reaches a predetermined position
To stop. While the stationary substrate 1 is placed on the arms 11 and 11, the substrate 1 is rotated to the position shown in FIG.

At this time, by sucking the substrate 1 with the suction pad 9 during the rotation, the substrate 1 is safely held at a predetermined position in combination with the action of the stopper 10. The processing tank 4 is moved forward by the operation of the air cylinder 15 and brought into contact with the substrate 1. After the contact, a vacuum pump or the like (not shown) is used to draw out a vacuum through the tube 13 to increase the degree of adhesion. The coating liquid supply tank 7 is raised by the operation of the elevating device 6 until the liquid surface thereof is slightly above the top of the surface to be coated. At this time, the liquid level of the processing tank 4 rises from a state of 0 to a predetermined level, and a part thereof overflows.
After the liquid surface of the processing tank 4 has stopped, the elevating device 6 is reversely operated to lower the supply tank 7 at a constant speed to a position where the liquid surface is lower than the bottom surface of the processing tank 4. At this time, the liquid level in the processing tank 4 descends at a constant speed, and the coating solution 17 is extracted. The vacuum state by the tube 13 is released, and then the treatment tank 4 is retracted by the reverse operation of the air cylinder 15,
It is detached from the substrate 1. The arm 11 of the holding device 2 is rotated to a horizontal position by the drive device 12, and then the suction of the suction pad 9 is released, and the substrate 1 is transferred to the belt conveyor 18.
To place. The substrate 1 is unloaded by the reverse operation of the belt conveyor 18.

Then, heat treatment is performed in an electric furnace or the like to obtain a uniform TiO ₂ film.

The coating solution overflowing from the processing tank 4 is recovered from the receiving tank 5 through a cleaning means (not shown).

Embodiment 2 This apparatus has a holding device 2 for holding a substrate 1 such as a glass plate as shown in FIGS. 2 and 3, and one side surface is opened in a shape matching the substrate 1, and the other side surface and bottom surface are closed. At the same time, a small opening 3 is formed by cutting the upper portion of the side surface that is not open in a sawtooth shape.
A treatment tank 4 having a structure formed with a fixed structure and a receiving tank 5 attached to the treatment tank 4 and having a surface including the small opening 3 as one side surface; A supply tank 7 for supplying the same coating solution 17 as in Example 1,
A recovery tank 23 provided below the processing tank 4 for extracting the coating solution and a valve 19 connected to the bottom surface of the supply tank 7
It is composed of a tube 20 introduced into the treatment tank 4 through the tube 20 and a tube 22 connected to the bottom surface of the treatment tank 4 and introduced into the collection tank 23 via the valve 21. Although not shown, in this case as well, it is preferable that the periphery of the processing tank 4 has a double structure so that a vacuum can be drawn.

Next, the procedure for coating a thin film will be described.

First, the substrate 1 such as a plate glass is placed on the holding device 2, the valve 19 is opened with the substrate 1 and the processing bath 4 in close contact with each other, and the coating liquid is poured into the processing bath, and the liquid surface partially overflows from a predetermined level. By the way, the valve 19 is closed. After the liquid level in the processing tank has stopped, the valve 21 is opened, the opening is adjusted so that the liquid level descending speed becomes a desired value, and the coating liquid is extracted at a substantially constant speed.

After that, a heat treatment tank is used as in Example 1 and Ti of uniform thickness is used.
Obtain an O ₂ film.

The preferred embodiments have been described above, but the present invention is not limited to these, and various applications are possible.

Thin SiO ₂ film in addition to TiO ₂ film obtained by the present invention, Zr
Optical thin film such as O ₂ film, Al ₂ O ₃ or mixed film of these,
There are various kinds of thin films for hologram such as dichromated gelatin film, and therefore various kinds of coating solutions can be applied.

In addition to plate glass, various plastic plates can be used for the substrate, and even if the shape is not only flat but also curved, it is enough to make the opening of the processing tank conform to the substrate, so it can be applied to substrates of various shapes can do.

The notch provided to form the small opening in the processing tank acts as a weir for overflow, but for reasons such as manufacturing, make the notch completely parallel to the coating liquid surface. In this case, the overflow amount becomes the shaded part shown in Fig. 4, and if this amount is made constant, the sawtooth shape overflows more widely than the straight line, and the notch cuts that much. It is preferable because a wide range of suspended solids can be removed because the cross-sectional area becomes small and the flow velocity of the overflow liquid becomes large. However, when the coating liquid surface and the notch are almost parallel or when the overflow amount is large, etc. Of course, it may be linear.

Further, although the present invention is suitable for partial coating, it is also possible to coat the entire surface on one side by increasing the opening area of the container, that is, by increasing the size of the container.

〔The invention's effect〕

According to the present invention, without masking a partial coating, which was conventionally difficult in wet coating,
Since it is not necessary to remove unnecessary films and the film thickness is easy to control and a uniform film can be obtained, it can be applied to a wide variety of applications such as combiners for head-up displays, reflectors, and decorative plates. Is.

[Brief description of drawings]

1 and 2 show Embodiment 1 and Embodiment 2 of the present invention, respectively.
FIG. 3 is a schematic perspective view showing the coating apparatus in FIG. 3, FIG. 3 is a perspective view showing the processing tank, and FIG. 4 is a view showing an overflow state in the processing tank notch portion. 1 …… Substrate, 2 …… Holding device 3 …… Small opening, 4 …… Treatment tank 7 …… Coating liquid supply tank 8, 20, 22 …… Tube 23 …… Collection tank, 19, 21 …… Valve

Claims (3)

[Claims] 1. A method for coating a thin film in which a substrate is coated with a coating solution to form a coating film, the coating solution being applied to the processing tank in a state where the opening surface of a processing tank having an opening on one side is in close contact with the substrate. To a predetermined level, and then a part of the solution is overflowed from a small opening formed in the processing tank, and then the coating liquid is withdrawn at a predetermined speed so that the level of the coating liquid contacting the substrate drops. And a method of coating a thin film. 2. A holding device for holding a substrate vertically or inclined, and a processing tank having one side face opened in a shape matching the substrate and a small opening formed on an upper side of the side face not opened.
It is equipped with a receiving tank that is attached to the processing tank and has a surface including the small opening as one side surface, and a coating liquid supply tank that is vertically movable, and a bottom surface of the processing tank and the coating liquid supply tank is formed by a tube. A thin film coating device characterized by being connected. 3. A holding device for holding a substrate vertically or inclined, and a processing tank having one side face opened in a shape conforming to the substrate and a small opening formed on an upper side of the side face not opened.
The processing tank comprises a receiving tank attached to the processing layer and having a surface including the small opening as one side surface, a supply tank for supplying the coating liquid to the processing tank, and a recovery tank for extracting the coating liquid from the bottom surface of the processing tank. A thin film coating apparatus, which is provided above and below a processing tank, and is connected to the processing tank by a tube via a valve, respectively.