JPH0836786A - Manufacture of optical recording medium - Google Patents

Abstract

PURPOSE:To remove bubbles mixed in adhesive and reduce the cost by limiting an adhesive coating region and decreasing the pressure of either the inner or the outer periphery to extent the adhesive. CONSTITUTION:A substrate 2 is set on a turntable 4, and an adhesive 1 is discharged in a ring state from a dispenser 3 to the outer peripheral position on the substrate 2 while rotating. Then, an opposite substrate 2 is moved down, and the substrate 2 is brought into contact with the adhesive 1 at the entire periphery. A cover jig 5 for covering the inner peripheral hole is mounted on the surface of the inner periphery of the substrate 2 to seal the inner periphery, and pressure is reduced so that the adhesive 1 is uniformly spread up to the inner peripheral edge. Thereafter, ultraviolet rays are cast at the adhesive via the substrate 2, further left to stand for 1 hour in an atmosphere at 100 deg.C to cure the adhesive 1. Thus, the bubbles mixed with the adhesive 1 can be removed to improve its defective ratio.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an optical recording medium.

[0002]

2. Description of the Related Art In recent years, an optical recording medium has attracted attention as an information recording medium having excellent characteristics. Various materials are used for the recording layer of this optical recording medium. Among them, as the material of the recording layer of the magneto-optical recording medium, rare earth elements such as Tb, Gd, Dy and amorphous transition metals such as Fe and Co are used. An alloy thin film is used. Since this material is very susceptible to oxidation and corrosion, a structure in which the recording layer is sandwiched between dielectric layers has been generally proposed for the purpose of protecting the recording layer. However, since this dielectric layer cannot be formed thick due to its nature or manufacturing method, its strength is small, and in order to compensate for this, an organic protective film layer has been further provided thereon. Then, the optical recording media capable of recording and reproducing information from both sides have been obtained by adhering the thus processed products.
Further, when it is sufficient to record and reproduce information from one side, a protective plate is attached to one side.

When the substrates are bonded together or the substrate and the protective plate are bonded together as described above, first, it is necessary to spread the adhesive used for bonding over the entire gap.
Conventionally, a roll coating method, a spraying method, a screen printing method, a spin coating method, a dispensing method and the like have been known. For example, as a method for laminating a magneto-optical recording medium, as an adhesive therefor, a fixing adhesive made of a paraffin-based hot melt resin or a reaction made by an ultraviolet curable resin, a thermosetting resin, a moisture curable resin, an anaerobic curable resin, or the like is used. A curable adhesive is often used.

The method of adhering with a hot melt resin is a method of applying an adhesive by a roll coating method and then immediately pressing it while cooling to cure the adhesive, which is a very excellent method for mass production. However, since pressing is performed while cooling, it is necessary to increase the pressing pressure considerably in order to overcome the deterioration of the fluidity of the resin and obtain the adhesive strength, which causes a problem that cracks are likely to occur in the recording layer. . If the press pressure is too low to avoid this problem, sufficient adhesive strength cannot be obtained, and another problem that the adhesive layer peels due to deterioration over time tends to occur. Further, since the adhesive itself is inferior in the denseness, it hardly functions as a barrier against the moisture that tries to penetrate from the outside of the medium. Therefore, it was not possible to manufacture a highly reliable optical recording medium by this method.

On the other hand, a reaction-curable adhesive generally has a lower viscosity than a fixed-type adhesive, and since it is not necessary to cure and bond immediately after application,
Sufficient fluidity can be secured at room temperature during pressing. That is,
Since the pressing pressure is small, it is possible to perform the bonding without damaging the recording layer. In addition, since the reaction-curable adhesive material generally has low hygroscopicity and low moisture permeability, it exhibits an excellent ability as a barrier against moisture that tries to enter from the outside of the medium after curing, and is bonded with this type of adhesive. The obtained optical recording medium has an advantage of excellent durability. As a method of applying a low-viscosity adhesive such as a reaction curable adhesive, a spray method, a spin coating method,
The screen printing method, the dispensing method and the like are common.

However, conventionally, in an optical recording medium manufactured by laminating with a reaction-curable adhesive, it is unavoidable that bubbles are mixed in the adhesive layer.
In the vicinity of the bubbles mixed in the adhesive layer, the recording layer and the dielectric layer may be cracked or deformed due to stress.
It adversely affects the focusing and tracking of the optical head. As a result, there has been a problem that a data error such as a burst error or a bit error, a seek (movement of a beam spot to a designated address) error, or the like occurs. In addition to this problem, there has been a problem that the manufacturing yield is poor and the cost is high.

Therefore, the dispensing method described below has been proposed. This method will be described with reference to FIG. That is, first, as shown in (a), while rotating the substrate 2 on which the recording layer is formed at a constant rotation speed, the substrate 2 is moved to a predetermined radial position on the upper surface thereof.
A predetermined amount of the adhesive 1 is discharged from the dispenser 3. As a result, the adhesive 1 becomes a ring shape on the substrate. next,
As shown in (b), the other substrate 2 is gently lowered onto the substrate coated with the adhesive in a ring shape. Then, as shown in (c), if the adhesive and the descending substrate come into contact, as shown in (e) through (d), leave or press until the adhesive spreads over the entire substrate, After that, it is cured.

[0008]

However, although the degree of inclusion of air bubbles in the adhesive layer is greatly reduced by the above-mentioned dispensing method, the viscosity of the adhesive due to the warp of the substrate, the fluctuation of temperature and humidity, etc. It was not possible to completely eliminate the inclusion of air bubbles in the adhesive layer due to changes in the wettability with respect to the adhesive on the substrate surface.

An object of the present invention is to solve such a problem.

[0010]

As a result of intensive research for solving the above problems, the present inventor has found that when an adhesive is applied onto a substrate, the application area of the adhesive is limited so that the other substrate or the protective plate. Even if air bubbles are mixed when they are brought into contact with each other, they can be located at a position where they are not affected or are small, and the flow rate of the adhesive can be easily adjusted by expanding the adhesive by reducing the pressure. The present invention has been completed and the present invention has been completed.

Therefore, according to the present invention, "the adhesive is applied to at least the substrate on which the recording layer is formed, and the same substrate or protective plate as the substrate is brought close to the substrate, and the adhesive is provided in the gap that appears. In the method for manufacturing an optical recording medium in which the adhesive is cured by spreading the adhesive, the application area of the adhesive is limited, and the inner circumference or the outer circumference is depressurized in one direction. A method for manufacturing an optical recording medium, which comprises spreading an adhesive.

[0012]

In the manufacturing method of the present invention, first, the substrate is coated with the adhesive. The area to be applied is limited to the outer edge area or the inner edge area that is outside the recording area of the optical recording medium.
Next, the other substrate or protective plate is brought close to the adhesive. The opposite substrate or protective plate may or may not be coated with an adhesive. After the entire circumference of the ring-shaped adhesive was in contact with the other substrate or protective plate optical recording medium, the adhesive was applied to the inner peripheral edge of this gap while keeping the two substrates or the substrate and the protective plate parallel to each other. In the case from the outer edge,
When applied to the outer peripheral edge, the pressure is reduced from the inner peripheral edge. By reducing the pressure, the applied adhesive reaches the inner peripheral edge or the outer peripheral edge and spreads over the entire gap. Even if air bubbles are mixed in, the position of the air bubbles is outside the recording area, so that the air bubbles do not cause a problem. Since there is a correlation between the degree of pressure reduction and the speed at which the adhesive spreads, the desired speed can be easily obtained by adjusting the degree of pressure reduction according to the viscosity of the adhesive used. After the adhesive has spread over the entire gap, it is cured by an appropriate curing method according to the adhesive, and the bonding is completed.

By reducing the degree of pressure reduction to the maximum extent at which the adhesive can be evenly spread, the time required for bonding can be shortened, and further, without spreading the adhesive throughout the gap,
It is also possible to provide a region that is not partially bonded.
Hereinafter, the present invention will be described in more detail with reference to Examples.
The present invention is not limited to this.

[0014]

EXAMPLE First, a polycarbonate resin substrate 6 having an outer diameter of 130 mm, an inner diameter of 10 mm and a thickness of 1.2 mm having a tracking groove was prepared by an injection molding method. A silicon nitride protective layer 7 having a thickness of 70 nm is formed as a dielectric on the entire surface of the substrate by sputtering, and a DyFeCo recording layer 8 having a thickness of 50 nm is also formed thereon by sputtering. Then, a protective layer 7 of silicon nitride was formed thereon as a dielectric to a thickness of 70 nm by sputtering.
Next, an acrylate-based UV curable resin was formed on the silicon nitride film by a spin coating method to a thickness of about 8 μm to form an organic protective layer 9. The substrate after the above steps is shown in FIG.
Shown in

Next, description will be made with reference to FIG. As shown in FIG. 1 (a), the substrate 2 was set on the turntable 4, and while rotating at a rotation speed of 10 rpm, 3 cc of the adhesive 1 was dispensed in a ring shape from the dispenser 3 to a position with a radius of 62 mm on the substrate. . Next, the other substrate was lowered at a predetermined speed, and the substrate 2 and the adhesive 1 were brought into contact with the entire periphery of the substrate 2 as shown in (c). Next, the cover jig 5 that covers the inner peripheral hole is attached to the surface of the inner peripheral portion of the substrate to seal the inner peripheral portion, and the pressure is reduced to 200 Torr from the lower method of the inner peripheral portion of the substrate, and the state is maintained. While spreading the adhesive to the inner peripheral edge. Then, the substrate was irradiated with ultraviolet rays at an intensity of 100 mJ / cm ² and left in an atmosphere of 100 ° C. for 1 hour to cure the adhesive.

A reproduction test was conducted on the optical recording medium thus manufactured, and data errors such as burst error, bit error, and seek error were measured, and the defective rate was 0%. The adhesive used was an ultraviolet / thermosetting resin manufactured by Grace Japan Co., Ltd. and having a viscosity of 500 cps.

[0017]

[Comparative Example] An optical recording medium was manufactured in the same manner as in Example except that the adhesive was discharged onto a substrate at a position having a radius of 40 mm, and the same measurement was performed. As a result, the defective rate was about 60%.

[0018]

As described above, according to the present invention, an optical recording medium of excellent quality which is not affected by bubbles mixed in the adhesive layer can be manufactured at low cost.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a bonding method of the present invention.

FIG. 2 is a conceptual diagram showing a conventional bonding method.

FIG. 3 is a vertical sectional view of an optical recording medium.

[Explanation of symbols]

 1 ... Adhesive 2 ... Substrate 3 ... Dispenser 4 ... Turntable 5 ... Cover jig 6 ... Substrate 7 ... Protective layer 8 ... Recording layer 9 ... Organic Above protective film

Claims (1)

[Claims] 1. After spreading an adhesive on a substrate on which at least a recording layer is formed, and by spreading the adhesive in a gap exposed by bringing the same substrate as the substrate or a protective plate close to the substrate. In the method for manufacturing an optical recording medium in which bonding is performed by curing the adhesive, the application area of the adhesive is limited, and the adhesive is expanded by depressurizing either the inner circumference or the outer circumference. A method of manufacturing an optical recording medium characterized by the above.