JPH05317797A - Rotary coating - Google Patents

Abstract

PURPOSE:To eliminate an inferior appearance entirely without any visible fine streaks on a film by applying a specified amount of ultraviolet beam-curable paint with the concurrent rotation of a disc-shaped substrate at low speed, then spinning off an extra coat by high-speed rotation of the substrate, and blasting a hot air to the uncured coat. CONSTITUTION:A rotary coating device coats a disc-shaped substrate with an ultraviolet beam-curable paint using a spin-coating method. An optical disc 1 as a disc-shaped substrate is installed on a turntable 3 with the side where a recording film 2 is formed, turned facing upward. In addition, a fixed amount of a protective coating agent 4 as an ultraviolet curable paint is applied to protect the side where the recording film 2 is formed of the optical disc 1. Further, an extra protective coating agent 4 is spinned off the optical disc 1 by high-speed rotation of the turntable 3. After that, a hot air is blasted against the protecting coating agent 4 remaining uncured on the optical disc 1. Consequently, the leveling properties are improved by increasing the surface temperature, if the protective coating agent of ultraviolet beam-curable type used has inferior leveling properties. Thus, a ripple pattern generated can be erased instantaneously.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spin coating method for coating a disk-shaped substrate with an ultraviolet curable coating material by a spin coating method.

[0002]

2. Description of the Related Art Conventionally known methods for coating resin on a disk-shaped substrate include, for example, polycarbonate resin having grooves called grooves in optical disks, polymethylmethacrylate resin, epoxy resin, amorphous polyolefin resin, etc. After a disk-shaped plastic substrate is spin-coated with a UV-curable coating called a hard coating agent on the surface opposite to the side where the groove is formed by spin coating, it is evenly spread over the entire surface of the plastic substrate. ,
Ultraviolet rays are irradiated to form a hard coat film.

Then, a recording film is formed on the side where the groove is formed by a vacuum vapor deposition method, a sputtering method or the like to manufacture an optical disk. An ultraviolet-curable coating material called a protective coating agent was spin-coated by a spin coating method on the recording film formation surface side of this optical disk to form a protective film on the entire surface of the optical disk.

Further, in the case of a compact disc, a reflective film is formed on a disk-shaped plastic substrate on which a predetermined information signal is preliminarily engraved by a vacuum deposition method or a sputtering method on the surface on which the information signal is engraved. An ultraviolet curable coating material called a protective coating agent was spin-coated by spin coating on the reflective film forming surface side to form a protective film on the entire surface of the compact disc.

Thus, when spin-coating a UV-curable coating material such as a hard coating material or a protective coating material on a disk-shaped substrate by a spin coating method, the coating material is disk-shaped at a constant speed and at a constant speed during low-speed rotation. It was applied to a substrate, then rotated at a high speed to shake off excess ultraviolet-curable coating material, and then irradiated with ultraviolet rays to be cured to form a uniform film.

[0006]

However, in this method, fine ripple-like streaks are formed on the resin surface immediately after the excessive ultraviolet curable coating is shaken off by rotating at a high speed, and ultraviolet rays having a particularly poor leveling property are generated. When the curable coating material is irradiated with ultraviolet rays as it is, the ripples remain on the surface of the coating film after curing, and there is a defect that the appearance becomes defective as fine streaks.

The problem to be solved by the present invention is to eliminate the generation of fine streaks in an uncured coating film after spin coating in a spin coating method in which a disk-shaped substrate is coated with an ultraviolet curable coating material by a spin coating method. It is an object of the present invention to provide a spin coating method capable of improving the yield in a spin coating process without causing any defective appearance of the obtained coating product.

[0008]

In order to solve the above-mentioned problems, the present invention provides a first step of applying a certain amount of an ultraviolet curable coating material to a disc-shaped substrate while rotating the disc-shaped substrate at a low speed. There is provided a spin coating method comprising a second step of rotating at high speed to shake off excess paint on a substrate and a third step of blowing hot air onto an uncured coating film on a disk-shaped substrate.

[0009]

According to the present invention, in a spin coating apparatus for coating a disk-shaped substrate with an ultraviolet-curable coating material by a spin coating method, a predetermined amount of coating material is coated, and then the disk-shaped substrate is rotated at a high speed to make an extra amount. Since the coating material is shaken off, and then hot air is blown to the uncured coating film on the disk-shaped substrate, the leveling property can be promoted by raising the surface temperature even with an ultraviolet-curing coating material having poor leveling properties. Ripples disappear immediately, and therefore, the coating obtained by irradiating this coating with ultraviolet rays and curing does not show any fine streaks, and it is possible to eliminate the appearance defect.

[0010]

EXAMPLES The present invention will be described in more detail below with reference to examples and comparative examples.

(Example) As shown in FIG. 1, an optical disk 1 which is a disk-shaped substrate is placed on a turntable 3 with the surface on which the recording film 2 is formed facing up to protect the surface on which the recording film 2 is formed. Therefore, a protective coating agent "EX-318" (manufactured by Dainippon Ink and Chemicals, Inc.) 4 was applied.

In this case, the turntable 3 is set to 60 rpm.
At the same time as the low speed rotation, the coating nozzle 5 of φ1.05 mm is moved to a position having a radius of 23 mm from the center of the optical disc 1 and a position of 1 mm on the surface of the optical disc, and then 1. The protective coating agent 4 was applied for 2 seconds under a pressure of 4 kgf / cm ² . Next, the optical disc was rotated at a high speed of 6,000 rpm to shake off the excess protective coating agent. In this case, the surface state of the coating film was in a state where fine ripple-like streaks 6 were generated as shown in FIG.

After that, as shown in FIG.
Clean air 7 at 0 ° C on the surface of the optical disc 1 for about 10
After spraying for 2 seconds from a position separated by cm, the protective coat agent 4 was cured by irradiating with ultraviolet rays 8 to form a protective coat film. However, fine streaks were not observed at all on the surface of the protective coat film as shown in FIG. I couldn't do it.

The temperature of the hot air is not so high as to cause the optical deformation of the optical disk to deteriorate the mechanical characteristics, but may be any temperature that can promote the leveling property.
It may be appropriately selected depending on the type of ultraviolet curable coating material and the leveling performance.

(Comparative Example) As shown in FIG. 1, the optical disk 1 which is a disk-shaped substrate is placed on the turntable 3 with the side on which the recording film 2 is formed facing up, and then on the side on which the recording film 2 is formed. A protective coating agent "EX-318" (manufactured by Dainippon Ink and Chemicals, Inc.) 4 was applied to protect the ink.

In this case, the turntable 3 is set to 60 rpm.
At the same time as the low speed rotation, the coating nozzle 5 of φ1.05 mm is moved to a position having a radius of 23 mm from the center of the optical disc 1 and a position of 1 mm on the surface of the optical disc, and then 1. The protective coating agent 4 was applied for 2 seconds under a pressure of 4 kgf / cm ² . Next, the optical disc was rotated at a high speed of 6,000 rpm to shake off the excess protective coating agent. In this case, the surface state of the coating film was in a state where fine ripple-like streaks 6 were generated as shown in FIG.

Then, as shown in FIG. 5, ultraviolet rays 8 were immediately irradiated to cure the protective coating agent 4 to form a protective coating film. The protective coating film was formed in the same manner as shown in FIG. Fine streaks 6 were found on the entire surface of the coating.

[0018]

According to the spin coating method of the present invention, a certain amount of the ultraviolet curable coating material is applied, and then the disc-shaped substrate is rotated at a high speed to shake off the extra ultraviolet curable coating material, and then the disc-shaped substrate is coated. Since hot air is blown to the uncured coating film of,
Even with UV-curable coatings that have poor leveling properties, the leveling property can be promoted by raising the surface temperature, so the ripples disappear immediately, so that the uncured coating film can be obtained by curing it by irradiating it with UV light. No fine streaks are found in the obtained coating, and it is possible to completely eliminate appearance defects.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a case where an ultraviolet curable coating material is applied to a disc-shaped substrate by a spin coating method, and is a side view when an optical disc is installed on a turntable.

FIG. 2 is a plan view showing a state of an uncured coating film surface when an excessive resin is shaken off at a high speed after applying an ultraviolet curable coating material.

FIG. 3 is a conceptual diagram when a protective coating agent is applied to an optical disc by the method described in the example.

FIG. 4 is a conceptual diagram in the case of applying a coating material to a disk-shaped substrate by a spin coating method, when an optical disk in the case of applying the hard coating agent described in Example 2 and Comparative Example 2 is installed on a turntable. FIG.

FIG. 5 is a conceptual diagram when a protective coating agent is applied to an optical disc by the method described in a comparative example.

[Explanation of symbols]

 1 Optical Disc 2 Recording Film 3 Turntable 4 Protective Coating Agent 5 Paint Coating Nozzle 6 Fine Rippled Lines 7 Hot Air 8 Ultraviolet

Claims (1)

[Claims] 1. A first step of applying a constant amount of an ultraviolet curable coating material to a disc-shaped substrate while rotating the disc-shaped substrate at a low speed,
A spin coating method comprising: a second step of rotating a disc-shaped substrate at high speed to shake off excess paint on the substrate; and a third step of blowing hot air onto the uncured coating film on the disc-shaped substrate.