JPH05253535A - Spin coating method - Google Patents

Abstract

PURPOSE:To control the difference of the thickness of the inner circumferential part and the outer circumferential part of substrate in the case an ultraviolet ray curable coating material is applied by spin coating apparatus. CONSTITUTION:Regarding a method to apply an active energy ray curable coating material 1 to a substrate 2 by spin coating, active energy rays having energy with which the viscosity of the coating material is changed between the inside and outside of the substrate but the coating material is not hardened, is irradiated to the coating material spread toward the radius direction by rotation. Consequently, the difference of the thickness in the radius direction is suppressed, so that the warp of the substrate 2 is lessened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of spin-coating active energy ray-curable coating material, and more specifically, it eliminates the disadvantage that the coating thickness is not uniform between the inner and outer peripheries of the substrate during coating. The present invention relates to a spin coating method.

[0002]

2. Description of the Related Art Conventionally, in a method of applying a coating material of active energy ray curable using a spin coating device to obtain a cured film,
Supply the paint while rotating the substrate at low speed, then
The coating was spread on the substrate by using centrifugal force by rotating at high speed, and after stopping the rotation, irradiation with active energy rays was performed to obtain a cured film.

However, according to the principle of the present method, as shown in FIG. 1, the obtained coating has unevenness on the inner peripheral side and the outer peripheral side.

In such a case, for example, in an optical disc using a plastic substrate, the difference in shrinkage of the cured film causes the substrate to be deformed, which may cause a focusing error or the like and cause an operation such as recording or reproducing. It will cause trouble.

As a method for preventing this, Japanese Patent Application Laid-Open Nos. 1-286146 and 2-15441 propose a method of irradiating active energy rays during rotation to cure. However, in this method, the coating is already non-uniform in the radial direction at the time of rotation, and since so-called setting time cannot be taken, fine radial stripes remain due to the spread of the paint at the time of rotation, and There is a risk that it may cause an error during recording and playback.

[0006]

The problem to be solved by the present invention is to obtain a uniform film thickness in the radial direction when the active energy ray-curable coating material is applied by the spin coating method. Therefore, the warp of the plastic substrate in the optical disc is suppressed.

[0007]

Means for Solving the Problems As a result of earnest studies, the inventors of the present invention have made it possible to control the viscosity of a paint developed by a spin coating apparatus so that the inner peripheral portion and the outer peripheral portion of the substrate are different from each other. The inventors have found that the problems can be solved and have reached the present invention.

That is, in order to solve the above problems, the present invention provides a method of spin-coating an active energy ray-curable coating on a substrate, in which the coating thickness is controlled for the spin-spreading radial coating. In order to achieve this, there is provided a spin coating method, which comprises irradiating an active energy ray having an energy which does not reach curing so that the viscosity of the coating material changes between the inside and the outside of the substrate.

In the case of a paint having a constant viscosity, the inner side in the radial direction is always on the side where the paint is supplied to the outer peripheral portion, but since the outer peripheral portion is the side where the paint is supplied, the outer peripheral portion and the inner peripheral portion are When comparing the film thicknesses with and, it is clear that the outer peripheral portion becomes thicker. Therefore, if the viscosity of the paint on the inner peripheral side is always made higher than that on the outer peripheral side with the start of rotation, the supply of the paint from the inner peripheral side to the outer peripheral side is temporarily reduced, so that a uniform film thickness can be obtained as a whole. Become.

As a method therefor, a method has been devised in which the coating material on the inner peripheral portion is irradiated with an active energy ray to such an extent that it does not cure and the viscosity is increased simultaneously with the start of rotation.

As a method of selectively irradiating the inner peripheral portion of the substrate with a large amount of active energy rays, for example, as shown in FIGS. 2 and 3, is it possible to arrange one or more spot light sources on the inner peripheral portion? Alternatively, a method of arranging an annular light source may be used. Further, as shown in FIGS. 4 and 5, a method of arranging a plurality of spot lights or annular light sources in the radial direction and weakening the irradiation intensity from the inner peripheral portion to the outer peripheral portion can be mentioned. Further, as shown in FIG. 6, a method of using a reflecting mirror having a shape capable of decreasing the energy density of active energy rays toward the outer peripheral portion and weakening the irradiation intensity toward the outer peripheral portion can be used. In this case, it is preferable to install an irradiation prevention plate between the light source and the paint so that the active energy ray from the light source does not directly irradiate the paint on the substrate.

The active energy ray-curable coating material can be applied to the method of the present invention without particular limitation as long as it can be used in a spin coating apparatus.

The irradiation energy of the active energy ray by these methods may be appropriately determined depending on the energy required for curing the active energy ray-curable coating material used, the rotation speed and the rotation time of the spin coater. In any case, any energy may be used as long as the viscosity is increased.

Further, after the development is completed, the rotation of the spin coater is stopped, a setting time is set as required, and then the whole coating material is irradiated with an active energy ray required for curing to complete the curing of the coating film. Let

As the energy beam for irradiation, an electron beam can be similarly used in addition to ultraviolet rays.

[0016]

In the coating obtained by the above method, the viscosity of the outer peripheral portion and the inner peripheral portion changes in an inclined manner, so that even if the coating is developed by rotation, the coating thickness between the outer peripheral portion and the inner peripheral portion becomes constant. ,
Therefore, it is possible to suppress the deformation of the substrate due to the shrinkage of the cured film.

[0017]

EXAMPLES Next, the present invention will be described in more detail with reference to Examples and Comparative Examples.

(Example 1) A 5.25-inch polycarbonate substrate for a magneto-optical disk was set on an origin spin coater, and was rotated at 50 rpm / min while being UV-curable coating "EX-701" (Dainippon Ink and Chemicals). Industrial Co., Ltd. product was circularly supplied to the inner peripheral portion in an amount of 2 g.

Next, the substrate was started to rotate at 2000 rpm / minute, and at the same time, the inner peripheral portion was irradiated with ultraviolet rays in a spot shape as shown in FIG. The irradiation intensity at this time is 20 m
The irradiation amount was W / cm ² , which was an irradiation dose at which the UV-curable coating did not cure.

When the paint reaches the outer periphery of the substrate,
By increasing the rotation speed to 3500 rpm / min, rotating until the coating thickness at the position 25 mm from the center of the substrate reaches 9 μm, then stopping, and irradiating 410 mW / cm ² of ultraviolet rays evenly on the entire surface of the coating. The coating was completely cured.

(Example 2) A 5.25-inch polycarbonate substrate for a magneto-optical disk was set on an origin spin coater, and while being rotated at 50 rpm, an ultraviolet curable coating "EX-701" was applied to the inner peripheral portion. 2 g was supplied in a circle.

Then, the substrate was started to rotate at 2000 rpm / minute, and at the same time, as shown in FIG. The irradiation intensity at this time is 20 mW /
The irradiation amount was cm ² , and the irradiation amount was such that the ultraviolet curable coating did not cure.

When the paint reaches the outer periphery of the substrate,
By increasing the rotation speed to 3500 rpm / min, rotating until the coating thickness at the position 25 mm from the center of the substrate reaches 9 μm, then stopping, and irradiating 410 mW / cm ² of ultraviolet rays evenly on the entire surface of the coating. The coating was completely cured.

(Example 3) A 5.25-inch polycarbonate substrate for a magneto-optical disk was set on an origin spin coater, and while being rotated at 50 rpm / minute, an ultraviolet curable coating "EX-701" was applied to the inner peripheral portion. 2 g was supplied in a circle.

Next, the substrate is started to rotate at 2000 rpm / minute, and at the same time, as shown in FIG. 4, there are two spot-shaped UV irradiation light sources arranged in the radial direction, and the outer circumference is larger than the inner circumference. Ultraviolet rays were set so that the irradiation intensity of the part was weakened. The irradiation intensity at this time is 20 mW / cm ²
That is, the irradiation amount was such that the ultraviolet curable coating did not cure.

When the paint reaches the outer peripheral portion of the substrate,
By increasing the rotation speed to 3500 rpm / min, rotating until the coating thickness at the position 25 mm from the center of the substrate reaches 9 μm, then stopping, and irradiating 410 mW / cm ² of ultraviolet rays evenly on the entire surface of the coating. The coating was completely cured.

(Example 4) A 5.25-inch polycarbonate substrate for a magneto-optical disk was set on an origin spin coater, and while being rotated at 50 rpm, an ultraviolet curable coating "EX-701" was applied to the inner peripheral portion. 2 g was supplied in a circle.

Next, the substrate is started to rotate at 2000 rpm / minute, and at the same time, as shown in FIG. 5, there is a double annular UV irradiation light source arranged radially in the inner peripheral portion,
The ultraviolet rays were set so that the irradiation intensity of the outer peripheral portion was weaker than that of the inner peripheral portion. The irradiation intensity at this time is 20 mW / cm
^{It was 2} , and the irradiation dose was such that the ultraviolet curable coating did not cure.

When the paint reaches the outer periphery of the substrate,
By increasing the rotation speed to 3500 rpm / min, rotating until the coating thickness at the position 25 mm from the center of the substrate reaches 9 μm, then stopping, and irradiating 410 mW / cm ² of ultraviolet rays evenly on the entire surface of the coating. The coating was completely cured.

(Example 5) A 5.25-inch polycarbonate substrate for a magneto-optical disk was set on an origin spin coater, and while being rotated at 50 rpm / minute, an ultraviolet curable coating "EX-701" was applied to the inner peripheral portion. 2 g was supplied in a circle.

Next, the substrate is started to rotate at 2000 rpm / minute, and at the same time, as shown in FIG. 6, a reflecting mirror having a shape capable of reducing the energy density of ultraviolet rays is installed toward the outer peripheral portion, and all of them are installed. The entire surface was irradiated with ultraviolet rays so that the ultraviolet rays were reflected by a reflecting mirror. The irradiation intensity at this time was 20 mW / cm ² , and the irradiation amount was such that the ultraviolet curable coating did not cure.

When the coating reaches the outer peripheral portion of the substrate,
By increasing the rotation speed to 3500 rpm / min, rotating until the coating thickness at the position 25 mm from the center of the substrate reaches 9 μm, then stopping, and irradiating 410 mW / cm ² of ultraviolet rays evenly on the entire surface of the coating. The coating was completely cured.

(Comparative Example) A polycarbonate substrate for a magneto-optical disk of 5.25 inches was set on an origin spin coater, and while being rotated at 50 rpm / minute, an ultraviolet curable coating "EX-701" was circled on the inner peripheral portion. 2 g was fed.

Next, the substrate was rotated at 2000 rpm / minute, and when the coating material reached the outer periphery of the substrate, the rotation speed was increased to 3500 rpm / minute, and the coating film thickness at a position 25 mm from the center of the substrate was 9 μm. The coating was completely cured by irradiating it with 410 mW / cm ² of ultraviolet rays evenly, after stopping the rotation until it became uniform.

With respect to the films obtained in the respective examples and comparative examples,
The film thickness difference between the outer peripheral part (55 mm from the center of the substrate) and the inner peripheral part (25 mm from the center of the substrate) of the substrate, which was measured using a visible ultraviolet spectrophotometer U-2000 manufactured by Hitachi Ltd. The film thickness of each part is shown in Table 1.

[0036]

[Table 1]

[0037]

According to the method of the present invention, it is possible to make the coating thickness of the substrate uniform in the radial direction.

Therefore, the method of the present invention is extremely useful for coating hard coats, protective coats on optical discs, and photoresists on ICs.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a film and a substrate obtained by a conventional spin coating device.

FIG. 2 is a conceptual diagram when irradiating a spot light set on an inner peripheral portion and performing spin coating.

FIG. 3 is a conceptual diagram when spin coating is performed by irradiating an annular active energy ray installed on the inner peripheral portion.

FIG. 4 is a conceptual diagram at the time of spin coating in which a plurality of spot lights are installed and irradiated in the radial direction from the inner peripheral portion.

FIG. 5 is a conceptual diagram at the time of spin coating in which a plurality of annular active energy rays are installed and irradiated from the inner peripheral portion in the radial direction.

FIG. 6 is a conceptual diagram when spin coating is performed using a reflecting mirror installed so that the active energy rays are weakened in reflection intensity toward the outer peripheral portion.

[Explanation of symbols]

 1 active energy ray curable coating 2 substrate 3 substrate center hole 4 spot light source (unirradiated state) 5 dropped active energy ray curable coating 6 spot light source (irradiated state) 7 active energy ray being developed by rotation Curable coating 8 Annular light source (unirradiated state) 9 Light source (irradiated state) 10 Reflector 11 Active energy ray irradiation prevention plate

Claims (6)

[Claims] 1. A method of spin-coating an active energy ray-curable coating material on a substrate, wherein the curing is performed so that the viscosity of the coating material changes between the inside and the outside of the coating material with respect to the coating material that develops in the radial direction by rotation. A spin coating method, which comprises irradiating an active energy ray of which the energy does not reach. 2. The spin coating method according to claim 1, wherein an active energy ray is applied to the inner peripheral portion of the coating material on the substrate. 3. The spin coating method according to claim 1, wherein the active energy ray is irradiated while changing the irradiation intensity toward the outer peripheral portion. 4. The spin coating method according to claim 2, wherein the spot-like active energy ray is irradiated. 5. The spin coating method according to claim 2, wherein the active energy ray is irradiated from a circular lamp. 6. The spin coating method according to claim 1, wherein the active energy ray is irradiated using a reflecting mirror having a shape capable of reducing the energy density of the active energy ray toward the outer peripheral portion.