JPH0520718A - Spin coating method for protective layer to disk-shaped recording medium and device therefor - Google Patents

Abstract

PURPOSE:To uniformly form a protective layer having a uniform thickness on a disk-shaped recording medium. CONSTITUTION:The disk-shaped recording medium 1 is adhered to a turn table 4 and the outer peripheral end of the disk-shaped recording medium 1 is previously heated by a nichrome wire 6. A coating liquid 10 is dropped from a nozzle 8 onto the surface in the inner peripheral part of the disk-shaped recording medium 1 and a spindle motor 2 is started to rotate the turn table 4 and eventually the disk-shaped recording medium 1 in an arrow A direction for a prescribed period of time. The dropped coating liquid is made to arrive at the outer peripheral end of the disk-shaped recording medium 1 by the effect of centrifugal force and is heated, by which the temp. is raised and the viscosity is lowered. Consequently, the coating liquid of the unnecessary amt. at the outer peripheral end is splashed to the outside of the disk-shaped recording medium 1 by the effect of the centrifugal force and is thereby removed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for applying a protective layer to a disk-shaped recording medium, and more particularly, to a radiation-curable resin as a protective layer for an overwritable magneto-optical recording medium by a magnetic field modulation method. Further, the present invention relates to a spin coating method and spin coating apparatus suitable for applying a paint.

[0002]

2. Description of the Related Art As an overwritable magneto-optical disk and a device therefor using a magnetic field modulation method, for example, JP-A-51-107121 and JP-A-63-217548 are available.
As described in JP-B No. 59-215008, JP-B No. 60-48806 and the like, there are known methods for modulating the magnetic field applied to the magneto-optical recording layer according to the information to be recorded. ing. Further, the structure of the magneto-optical disk used in these devices is such that a laminated film of a recording layer and an inorganic dielectric protective layer is formed on a substrate, and a resin layer as a protective layer is further provided thereon. Is common.

Conventionally, a spin coating method using a spin coater has been generally used as a method for forming the protective layer. This spin coating method is a method for forming a surface of an inner peripheral portion of an object to be coated (disk-shaped recording medium). Is a method of forming a protective layer on the surface of the object to be coated by casting the coating solution by the action of centrifugal force by dropping the coating solution onto the object and rotating the object to be coated.

By the way, the resin composition used for the protective layer is
When a resin containing a solvent or a coating material is directly applied to the laminated film, a solventless type is preferable in order to prevent the laminated film from being lifted from the substrate and peeled off or cracks in the laminated film. Further, the resin curing method, when considering the heat resistance of the substrate, is cured at a lower temperature than thermosetting,
In addition, a so-called radiation curing method of curing using ultraviolet rays or electron beams is preferable. As described above, the resin used for the protective layer is generally a solventless type radiation curable resin.

[0005]

In the spin coating method described above, a phenomenon occurs in which the coating liquid collects and rises at the outer peripheral edge of the disk-shaped recording medium. When used in a magnetic field modulation type magneto-optical recording medium, such a thick portion of the coating film may come into contact with the magnetic head or the slider portion when it is mounted on the magneto-optical recording device and rotated to damage them. It is a problem that it ends up. The rise of such a coating film is
The higher the viscosity of the coating liquid, the more remarkable.

In the case of a general solvent type coating solution, it is easy to prevent the outer peripheral edge of the coating film from rising by increasing the solvent component in the coating solution to reduce the viscosity. However, it is difficult for the above-mentioned solventless type. This is because, in the case of a solventless type radiation curable resin, if the concentration of the reactive diluent in the constituents is increased, the viscosity of the coating solution will decrease to some extent, but on the other hand, the physical properties of the coating film after curing will be Because it becomes brittle.

The present invention has been made in view of the above problems of the prior art, and is capable of forming a protective layer having a uniform thickness uniformly on a disk recording medium. An object of the present invention is to provide a method and apparatus for spin coating a protective layer on a medium.

[0008]

In order to achieve the above object, the method of spin coating a protective layer on a disk-shaped recording medium according to the present invention is performed by heating the outer peripheral edge of the disk-shaped recording medium in advance, The disc-shaped recording medium is rotated while the coating liquid is dropped on the surface of the inner peripheral portion of the disk-shaped recording medium.

Further, the coating liquid may be dropped on the surface of the inner peripheral portion of the disc-shaped recording medium, and the disc-shaped recording medium may be rotated while heating the outer peripheral end of the disc-shaped recording medium.

As an apparatus for carrying out the above method,
Rotating means for rotating the disk-shaped recording medium, dropping means for dropping the coating liquid on the inner peripheral surface of the disk-shaped recording medium, and for heating the outer peripheral end of the disk-shaped recording medium. And heating means. The rotating means for rotating the disk-shaped recording medium is composed of a table for supporting the disk-shaped recording medium and a motor for rotating the table, and heats the outer peripheral end of the disk-shaped recording medium. The heating means for performing the heating may be composed of a heating element embedded in the table and a power source for energizing the heating element.

Further, as a heating means for heating the outer peripheral end of the disk-shaped recording medium, a laser light irradiating device for irradiating the outer peripheral end with a laser beam may be used instead of the heating element and the power source. .

[0012]

In the invention according to claim 1 configured as described above, the outer peripheral end of the disk-shaped recording medium which is the object to be coated is heated in advance so that the disk-shaped recording medium drops when it rotates. The applied coating solution reaches the outer peripheral end of the disk-shaped recording medium by the action of centrifugal force, and is heated to increase the temperature and decrease the viscosity. As a result, an unnecessary amount of coating liquid on the outer peripheral edge is scattered and removed outside the disc-shaped recording medium by the action of the centrifugal force.

According to the second aspect of the invention, the coating liquid dripped onto the disc-shaped recording medium by rotating the disc-shaped recording medium while heating the disc-shaped recording medium,
Similar to the invention described in (1), the outer peripheral edge of the disk-shaped recording medium is reached by the action of centrifugal force, and is heated to increase the temperature and decrease the viscosity. As a result, an unnecessary amount of coating liquid on the outer peripheral edge is scattered and removed outside the disc-shaped recording medium by the action of the centrifugal force.

[0014]

Embodiments of the present invention will now be described with reference to the drawings. (First Embodiment) First, the structure of the spin coating apparatus according to the first embodiment will be described.

As shown in FIG. 1, a spindle motor 2 is fixedly supported by an apparatus main body (not shown), and a tip of an output shaft (rotary shaft) 3 of the spindle motor 2 has a center of a turntable 4 at its tip. The lower surface of the part is fixed. The turntable 4 has a structure for supporting the disc-shaped recording medium 1 on its upper surface, and has a ring-shaped groove 5 formed in a portion corresponding to the outer peripheral portion of the disc-shaped recording medium 1. The spindle motor 2 and the turntable 4 constitute a rotating means for rotating the disk-shaped recording medium 1.

A nichrome wire 6 as a heating element is uniformly provided in the ring-shaped groove 5, and an AC power supply 7 for energizing the nichrome wire 6 is embedded in the turntable 4. Further, above the central portion of the disc-shaped recording medium 1 supported by the turntable 4, a nozzle 8 as a dropping means for dropping the coating liquid 10 on the inner peripheral surface of the disc-shaped recording medium 1 is provided. The nozzle 8 is in communication with a storage member (not shown) that stores the coating liquid.

Next, the spin coating method will be described.

Sputtering (sputtering pressure 0.2 P) was performed on a polycarbonate disk substrate having a thickness of 1.2 mm and a diameter of 86 mm, which had a chamber groove and a preformat signal.
a, input power 500W), film thickness 500 × 10 ^-4 μ
Of Si ₃ N ₄ is formed, and the film thickness is 400 × 10 ^{−4 on it.}
An amorphous GdFe layer having a thickness of μ and an amorphous TbFe layer having a thickness of 400 × 10 ⁻⁴ μ are sequentially stacked by sputtering at a sputtering pressure of 0.3 Pa to form a magnetic recording layer. Further, a Si ₃ N ₄ layer having a film thickness of 700 × 10 ⁻⁴ μ is sputtered at a pressure of 0.2 P.
a, a film was formed with an input power of 500 W to obtain a magneto-optical disc-shaped recording medium. Next, as shown in FIG. 1, the disk-shaped recording medium 1 is mounted on the turntable 4 of the spin coater, and the nichrome wire 6 is used to adjust the current value to be applied to the nichrome wire 6 by the AC power supply 7. The outer peripheral edge of the flat recording medium 1 was uniformly heated. At this time, the temperature of the outer peripheral edge portion was measured by a contact type digital thermometer and was 35 ° C. In this state, the photo-curable resin (product name S
A predetermined amount of the coating liquid 10 made of PC339 and Nippon Kayaku Co., Ltd. is dropped, and the spindle motor 2 is activated to turn the turntable 4 and thus the disc-shaped recording medium 1 into an arrow A.
Rotate in the direction for a predetermined time. During the rotation, the dropped coating liquid reaches the outer peripheral end of the disk-shaped recording medium 1 by the action of centrifugal force, is heated and the temperature rises, and the viscosity decreases. As a result, an unnecessary amount of the coating liquid on the outer peripheral edge is scattered and removed outside the disc-shaped recording medium 1 by the action of the centrifugal force.

After this, an electron beam irradiation device (manufactured by Nisshin High Voltage Co., Ltd., Curetron EBC-200-20-15) was used.
Type) was used to irradiate an electron beam of 10 Mrad at an accelerating voltage of 150 KV to form a protective layer.

The disk-shaped recording medium 1 thus obtained
The thickness of the inner peripheral part (radius 30 mm) and the outer peripheral part (radius 4
1 mm) and the thickness of the inner peripheral portion was subtracted from the thickness of the outer peripheral edge to obtain the bulge amount of the protective layer at the outer peripheral edge, which was about 0.8 μm.
Met.

Further, the temperature of the outer peripheral end of the disk-shaped recording medium 1 is adjusted to 4 by adjusting the value of the electric current applied to the nichrome wire 6.
Three disc-shaped recording media were formed so that the temperatures were set to 5 ° C., 55 ° C., and 65 ° C., and under the other conditions, the protective layers were formed in the same manner.

The bulge amount of the protective layer at the outer peripheral edge of each of these three disk-shaped recording media was about 0.2 μm.

As a comparative example of the above-mentioned embodiment, when the protective layer was formed on the disc-shaped recording medium under the same conditions except that the nichrome wire 6 was not energized, the bulge amount of the protective layer was about 3. It was 4μ.

The results of these experiments are shown in FIG.

As is apparent from FIG. 2, when the outer peripheral edge of the disk-shaped recording medium is heated in advance, the amount of swelling of the protective layer is much smaller than in the conventional example. (Second Embodiment) As shown in FIG. 3, the spin coating apparatus of the present embodiment uses a heating element and an AC power source of the first embodiment as heating means for heating the outer peripheral end of the disk-shaped recording medium 1X. Instead of the laser beam 9 on the outer peripheral end face of the disk-shaped recording medium 1X.
A laser light irradiation device (not shown) for irradiating X is used. Other configurations are the same as those shown in FIG.

In this embodiment, during spin coating, the turntable 4X is rotated in the direction of arrow AX, and the outer peripheral end face of the disk-shaped recording medium 1X is irradiated with laser light 9X.
The outer peripheral edge of the disk-shaped recording medium 1X is uniformly heated in advance. The other steps are similar to those of the first embodiment.

In each of the above-mentioned embodiments, the higher the viscosity of the coating liquid used, the higher the set temperature of the outer peripheral end of the disc-shaped recording medium, that is, the disc-shaped recording medium is adjusted to the viscosity of the coating liquid. The temperature of the outer peripheral edge may be set.

Further, although the outer peripheral end portion of the disc-shaped recording medium is heated in advance and the coating liquid is dropped while the disc-shaped recording medium is rotated, the present invention is not limited to this, and the disc-shaped recording medium is not limited thereto. The disc-shaped recording medium may be rotated while the coating liquid is dropped onto the surface of the inner peripheral portion of the above and the outer peripheral end portion is heated.

[0029]

Since the present invention is configured as described above, it is possible to uniformly form a protective layer having a uniform thickness on the surface of a disk-shaped recording medium. The magnetic head and slider of the magneto-optical device used are not damaged.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a first embodiment of a spin coating apparatus for forming a protective layer on a disk-shaped recording medium of the present invention.

FIG. 2 is a graph showing the results of comparison between the spin coating method of the present example and the conventional example, in which the horizontal axis represents the set temperature of the outer peripheral edge of the disk-shaped recording medium and the vertical axis represents the bulge of the outer peripheral edge. It is a quantity.

FIG. 3 is a schematic configuration diagram of a second embodiment of a spin coating apparatus for forming a protective layer on a disk-shaped recording medium according to the present invention.

[Explanation of symbols]

1,1X disk-shaped recording medium (coated material) 2,2X spindle motor 3,3X output shaft (rotating shaft) 4,4X turntable 5 grooves 6 Nichrome wire 7 AC power supply 8,8X nozzle 9X laser light 10,10X coating liquid A, AX Disk rotation direction

Claims (5)

[Claims] 1. An outer peripheral end of a disk-shaped recording medium is heated in advance, a coating liquid is dropped on the surface of the inner peripheral part of the disk-shaped recording medium, and the disk-shaped recording medium is rotated.
A method of spin-coating a protective layer on a disk-shaped recording medium. 2. A disc-shaped recording medium, wherein the coating liquid is dropped on the inner peripheral surface of the disc-shaped recording medium and the disc-shaped recording medium is rotated while heating the outer peripheral end of the disc-shaped recording medium. Spin coating method for protective layer. 3. A rotating means for rotating the disc-shaped recording medium, a dropping means for dropping a coating liquid on the inner peripheral surface of the disc-shaped recording medium, and an outer peripheral end portion of the disc-shaped recording medium. And a heating means for heating the disk. A spin coater for applying a protective layer to a disk-shaped recording medium. 4. A rotating means for rotating the disc-shaped recording medium, a table for supporting the disc-shaped recording medium,
The heating means for heating the outer peripheral end of the disk-shaped recording medium comprises a motor for rotating the table, a heating element embedded in the table, and a power source for energizing the heating element. A spin coating apparatus for a protective layer onto a disk-shaped recording medium according to claim 3, which is composed of: 5. A laser light irradiating device for irradiating the outer peripheral end portion with a laser beam is used as the heating means for heating the outer peripheral end portion of the disk-shaped recording medium, instead of the heating element and the power source. An apparatus for spin coating a protective layer onto a disk-shaped recording medium according to.