JPS6173251A - Manufacture of optical disk - Google Patents

Abstract

PURPOSE:To manufacture an optical disk which is free from air bubbles on its recording film and has a high adhesive property even under high-temperature and high-moisture conditions, by bonding a transparent base, on which an optical recording layer is formed, onto a plastic film having a mold releasability with the optical recording layer inside and, after the film is hardened, removing the film and hardening them after applying a bonding agent to a resin layer formed on the plastic film and adhered to the recording layer. CONSTITUTION:A plastic film 17 with a light-curable resin layer 16 is stuck onto a transparent base 14 on which a recording film 15 is formed and they are stuck to each other by passing them through the space between heatable rolls 18 and 19 while expelling air. By irradiating ultraviolet rays upon the resin layer 16 through the plastic film 17 and hardening the resin layer 16, the optical film 15 on the transparent base 14 is protected by the protective layer which is free from air bubbles and firm. After the plastic film is removed, a bonding agent layer 26 is applied onto the previously photoset resin 16. Two disks formed in such a way are stuck to each other with the optical recording layer inside and heated to 60-70 deg.C, and thus, the optical disk of this invention is completed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for laminating optical discs.

Conventional configuration and its problems Laser recording disc (hereinafter referred to as optical disc)
has a diameter of 30. It is a large-capacity memory medium that can store more than 10,000 A4 documents on a medium-sized disk, and each bit corresponds to a small pit of about 1 μm in length. In addition, writing and reading information is performed by focusing a laser beam narrowed to a diameter of around 1 μm onto a disk that rotates at a high speed of over 1000 revolutions per minute, while detecting the position and adjusting the focus. Since the board is hard, slight warpage, deviation in parallelism, deformation, scratches, foreign objects, etc. can lead to signal errors. For this reason, the production of optical discs requires as much care as the production of semiconductors. Conventionally, for the purpose of increasing reliability, optical discs have a structure in which a thin film 4.6 for laser recording is sandwiched between two transparent substrates 2.3, as shown in FIG. (However, FIG. 1 is a perspective view of an optical disc cut away, and hereinafter, the stacked state will be explained by enlarging part A of the cross section. In FIG. 2, an example of a double-sided recording optical disc is shown.) Therefore, The bonding process of bonding these two transparent substrates 2 and 3 together via the adhesive layer 6 is important, and this process often affects the yield and the reliability of the optical disc. Traditionally, hot melt adhesives are known as this bonding method, but since heat and pressure are applied at the same time, this method easily causes warping, distortion, scratches, and bubbles on the board. Moreover, depending on the recording film, deterioration may occur due to thermal effects.
In addition, there were many other problems, such as peeling due to a decrease in adhesive strength under high humidity.

OBJECTS OF THE INVENTION The present invention overcomes the drawbacks of conventional bonding methods.
The purpose of this method is to efficiently manufacture optical discs that do not cause scratches or bubbles on the recording film and have highly reliable adhesive properties even under high temperature and high humidity conditions.

Structure of the Invention The method for producing an optical disc of the present invention involves forming an optical recording layer in advance on a releasable glasstic film coated on one side with a photocurable adhesive that is sticky at a temperature of 120° C. or lower. The transparent substrate is pasted with the optical recording layer on the inside to prevent air bubbles from forming, and the photo-curable adhesive is cured with ultraviolet light.The glass film is peeled off, and the adhesive that can be cured at low temperatures is photo-cured. It is applied onto a subsequent photocurable resin and cured via the adhesive and another transparent substrate having the same structure or a single transparent substrate.

Description of examples First, the main points of the present invention will be explained using figures.

FIG. 3 shows a cross-sectional structure of a double-sided optical disc completed according to the present invention. That is, the transparent substrate 7. On B there are optical recording layers 9 and 10, and layers of ultraviolet curable resin 11 and 12, and in the center of these is an adhesive layer 1 that can be cured at low temperatures.
3 exist. The whole manufacturing process is
As shown in FIG. 6, the process mainly consists of six steps. In step 1, on the transparent substrate 14 on which the recording film 15 is formed,
One method is to attach a releasable plastic film 17 having a photocurable resin layer 16, as shown in FIG.
The plastic film and the transparent substrate are overlapped and passed through the gap, and the disks are bonded together while expelling air from one end of the disk. Another method is a hot press method under reduced pressure as shown in Figure 6.
The plastic film 17 is superimposed on the transparent substrate 14, and is bonded by thermocompression using the heatable upper and lower pedestals 22 and 23 while the pressure in the vacuum chamber 24 is reduced by the exhaust system 25iC. By any of the above methods, the transparent substrate and the film can be bonded without generating bubbles. The thermocompression bonding conditions at this time vary depending on the substrate, recording film, and photocurable adhesive resin used, but
The temperature is below the thermal deformation temperature of the substrate, and the pressure is 15 kg/
It is desirable that it is 7 or less. Under conditions higher than these, deformation of the substrate is likely to occur. In Step 2, ultraviolet rays are irradiated through the film pasted in Step 1, and for this reason, it is necessary for the plastic film to pass the light. By curing with ultraviolet light, the optical recording film on the transparent substrate is protected by a strong protective layer without bubbles, which facilitates post-processing and greatly improves the reliability of the optical disc. In addition, as shown in FIG. 7, in order to apply an adhesive layer 26 on the photo-cured resin 16 after peeling off the plastic film,
Even if a small amount of foreign matter or bubbles get mixed in when applying the adhesive, the performance of the optical disk will not deteriorate, and since the adhesive is applied through the already hardened photocurable resin layer 16, it is not affected by the solvent resistance of the transparent substrate 14. You can choose the adhesive. Furthermore, since the cured layer 16 is protected, defects such as scratches on the optical recording film 1γ can be significantly reduced. Roll and spray adhesive.

After coating by gravure method, no-ke coating, etc., the two discs are pasted together with the optical recording layer inside and the central axes of both discs aligned, and then heated at room temperature or at 6o~7℃.
By heating to 0° C., the optical disc of the present invention is completed as shown in FIG.

As the adhesive used in this step 4, a low-temperature curing adhesive is effective, and examples include epoxy adhesive, acrylic adhesive, urethane adhesive, polybutadiene adhesive, and polyester adhesive. Among them, two-liquid non-mixing type (hereinafter referred to as SG)
The adhesive (referred to as A) is easy to use, and in this case, it is very advantageous in terms of the process because it is possible to apply a method in which the two components of the adhesive are applied separately to the two disks to be bonded together. Although the above embodiments have mainly described optical discs in which both sides of the disc are used, in the fifth step (bonding), an optical recording film is not used on one side, and the disc is intended to be used on one side. Also included in the present invention is the manufacture of That is, in step 5, the ultraviolet curing resin 2 is applied on the optical recording film 28 completed up to step 4.
One disk 27 having a complete protective layer consisting of 9 is bonded to another transparent substrate 30 via an adhesive layer 31. In this case, the adhesive layer 31 is the double-sided disk described above. In addition to various types of adhesives, UV-curable adhesives can also be used.

Next, a specific example will be explained.

Specific example 1 Thickness 1.0m, outer diameter 200 rm, inner diameter 3
On a 5fi methacrylic resin substrate (hereinafter referred to as a PMMA substrate), a To-based thin film whose reflectance changes due to phase change caused by laser light with a wavelength of 800 to 850 wavelengths is deposited, and on top of this a 25 μm thick silicon film is deposited. An adhesive film with a 20 μm thick acrylic photocurable resin layer with a curing point of 40 to 6 Q°C was pasted onto the polyester film that had been subjected to a mold release treatment using the rubber roll described above. Wearing.

The roll conditions were 80° C. and 5 Psi pressure.

After that, the plastic film was cured by irradiating ultraviolet rays of 300 mT (millijoules) from the side, and then the plastic film was peeled off and 2/g was applied to the entire surface of the photocurable resin of two transparent substrates having the same structure.

After applying each of the two components of the mixed acrylic adhesive to a thickness of 6 μm using a rubber roller, they were laminated parallel to each other with the center axes of the disc aligned, and cured at room temperature to complete an optical disc. The performance of the completed optical disc is shown in the table. Among performance, error rate indicates the frequency of occurrence of defective bits when writing is performed using a semiconductor laser with wavelengths in the order of 820 and condensed to 1 μm, and the frequency of occurrence of defective bits is averaged over 100 completed discs. For example, 1×1o means 1 per 1000 pits.
This indicates a reading failure. Also, the yield is
This is the result of determining that a product with an error rate of 1X10 or more at the end of all steps is a good product.

Moisture resistance is the result of visually observing changes in the adhesive portion of the substrate after it was left at 60° C. and 90% RH for 7 days.

Concrete Example 2 The T of Concrete Example 1 was placed on a polycarbonate substrate (hereinafter referred to as Pc substrate) with a thickness of Class 1, an outer diameter of 200, and an inner diameter of 35.
o-based recording film was deposited, and a 20 μm sticky polybutadiene-based cured resin layer was formed on top of this to a thickness of 16 mm.
A .mu.m release-treated polyester film was attached using a vacuum adhesive device shown in FIG. The conditions for pasting are:
The degree of vacuum was 1 ton, the pressure was 0.1 Kq/cA, and the temperature was 1 minute at room temperature. After the pressure was returned to normal, it was cured with 600 ml of ultraviolet light, and a mixed phenol of a two-component low-temperature curing epoxy resin was applied to a thickness of 30 μm on the cured photocurable resin. A rubber roller was used for application. A double-sided optical disc is manufactured by bonding optical disc substrates with the same configuration on top of this with their central axes aligned, pre-curing at 70°C for 6 minutes, and then main curing at room temperature for 24 hours. did. The performance of this optical disc is shown in the table.

Specific Example 3 Using a Pc substrate with a thickness of 1.0 mm, an outer diameter of 200 mm, and an inner diameter of 36 mm, a film was pasted and photocured in the same manner as in Example 1, and only the film was peeled off. On the other hand, on another transparent substrate of the same size, a liquid acrylic ultraviolet curable adhesive was applied to a thickness of 10 μm using a spin coating method, and then the substrate on which the photocurable resin layer was formed was coated. The central axes were aligned, the optical recording film was brought into close contact with the inside, and the film was cured with 300 mJ of ultraviolet light from the transparent substrate side.

After curing, the excess film was removed to complete a single-sided recording optical disc. The performance of this optical disc is shown in the table.

For reference in April, the Te-based optical recording film was formed on an acrylic substrate with a thickness of 1.0 mm, an outer diameter of 200 mm, and an inner diameter of 35 mm.
Urethane hot melt adhesive was applied to a thickness of μm. The roll temperature was 100°C. In this way, the two sets of transparent substrates coated with hot melt adhesive were aligned so that their central axes were aligned, the adhesive surfaces were brought into close contact with each other, and then pressed for 6 minutes using a 100°C heat press at a pressure of 5K97'crA. and pasted it together.

The performance of this optical disc is shown in the table.

As is clear from the effect table of the invention, all optical discs manufactured using the method of the present invention have an extremely low incidence of pit reading errors compared to the conventional method using a general hot melt adhesive. It can be seen that this is an excellent manufacturing method that causes less generation of bubbles near the recording film and less damage to the film. Moreover, because it is protected by a cross-linked polymer, it maintains a stable adhesive state even under high temperature and high humidity conditions, making it a major contribution to the realization of highly reliable optical discs. .

table

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an optical disc cut away and showing an enlarged part A;
Figure 2 is a sectional view of a conventional hot-melt adhesive disc, Figure 3 is a sectional view of a double-sided disc completed by the manufacturing method of the present invention, and Figure 4 is a film pasted onto a substrate using a roller. Fig. 6 is a flowchart showing the process of the present invention, Fig. 6 is a diagram of the vacuum bonding device, Fig. 7 is a cross-sectional view showing the adhesive application state, Fig. 8 is a one-sided It is a sectional view of the disk used. 1... Completed disk, 2, 3, 7, 8, 14° 27.30... Transparent substrate, 4, 5, 9, 10,
15゜28... Optical recording film, 6... Hot melt adhesive, 11.12, 16.29...
Ultraviolet curing resin layer, 13.16.31...Low@
(Or ultraviolet) cured resin layer, 18.19...
Heating roll, 20.21...Movable shaft, 22.2
3... Upper and lower pedestals, 24... Vacuum chamber, 2
5...Exhaust system. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 3 Figure 5 Figure 7? 7

Claims (4)

[Claims] (1) A photocurable resin layer that is adhesive at a temperature of 120°C or less is formed on one entire surface of a plastic film with a release agent layer formed on the surface, and the photocurable resin layer is coated with an optical recording layer in advance. After pasting the formed transparent substrate with the optical recording layer on the inside to prevent air bubbles from forming, it is cured by ultraviolet rays, the plastic film is peeled off, and the cured photocurable resin layer is coated at a low temperature. A method for manufacturing an optical disk comprising the steps of applying a curable adhesive, bonding it to another transparent substrate having the same configuration, or a single transparent substrate via the adhesive, and curing. (2) A method for manufacturing an optical disc according to claim 1, which comprises using a heatable roll when pasting the photocurable resin formed on the releasable plastic film onto the transparent substrate. (3) A method for manufacturing an optical disc according to claim 1, which comprises using a press capable of heating under reduced pressure when pasting the photocurable resin formed on the releasable plastic film onto the transparent substrate. . (4) A photocurable resin layer is formed on the optical recording film and cured by ultraviolet irradiation, and then on each of the two transparent substrates having the same structure,
2. The method of manufacturing an optical disk according to claim 1, wherein two components of a two-component non-mixable rapid-curing adhesive are applied separately, and the two components are bonded together and cured.