JPH0370296B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for bonding laser recording disks. (Conventional structure and its problems) A laser recording disk (hereinafter referred to as an optical disk) is a large-capacity memory medium that can store more than 10,000 A4 pages on a disk with a diameter of less than 30 cm. Yes, each bit corresponds to a small pit with a length of only around 1 μm. In addition, information must be written and read on a disk with a diameter of 1 μm that rotates at a high speed of more than 1000 revolutions per minute.
This is done by condensing a laser beam narrowed down to around m, detecting the position, and adjusting the focus.Even the slightest warpage of the board, deviation in parallelism, deformation, scratches, foreign objects, etc., can cause signal errors. It leads to For this reason, the manufacturing of optical disks requires as much care as in the manufacturing of semiconductors. Conventionally, for the purpose of increasing reliability, an optical disk has a structure in which laser recording thin films 4 and 5 are sandwiched between two transparent substrates 2 and 3, as shown in FIG. (However, Figure 1 is a perspective view of the optical disk cut away, and below, part of the cross section A
The laminated state will be explained by enlarging the figure. FIG. 2 shows an example of a double-sided recording optical disc. ) Therefore, the adhesion 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 reliability of the optical disk. Traditionally, hot melt adhesives have been known as this bonding method, but since heat and pressure are applied at the same time, this method tends to cause warping, distortion, scratches, and bubbles on the board, and it is also difficult to use. However, some recording films suffer from deterioration due to the influence of heat, and in addition, there are many problems such as peeling due to a decrease in adhesive strength under high humidity. (Objective of the Invention) The present invention solves the drawbacks of conventional adhesive methods, and eliminates the generation of scratches and bubbles on the recording film.
The objective is to efficiently manufacture optical disks that have highly reliable adhesion even under high temperature and high humidity conditions. (Structure of the Invention) The method for manufacturing an optical disk of the present invention is based on a transparent substrate on which an optical recording layer is preliminarily formed on a plastic film coated on the entire surface of one side with a photocurable adhesive that is sticky at a temperature of 120°C or less. The plastic film is pasted with the optical recording layer on the inside to avoid air bubbles, and after curing the photocurable adhesive with ultraviolet rays, an adhesive that can be cured at low temperatures is applied onto the plastic film, and another identical sheet is attached. The process consists of the steps of bonding the constituting transparent substrate or transparent substrate alone through the adhesive with their central axes aligned and curing, and then cutting off the excess plastic film. (Description of Examples) First, the main points of the present invention will be explained with reference to the drawings. FIG. 3 shows a cross-sectional structure of a double-sided optical disc completed according to the present invention. That is, optical recording layers 9 and 10 are provided on transparent substrates 7 and 8, and there are layers of plastic films 13 and 14 via ultraviolet curable resin layers 11 and 12, and an adhesive that can be cured at low temperature is placed in the center of these layers. This means that layer 15 is present. The entire manufacturing process mainly consists of six steps as shown in FIG. Process 1
As shown in FIG. 4, a plastic film 19 having a photocurable resin layer 18 is pasted on a transparent substrate 16 on which an optical recording film 17 is formed.One method is as shown in FIG. As shown in the figure, the plastic film and the transparent substrate are overlapped and passed between heatable rolls 20 and 21, and the discs are bonded together while expelling air from one end of the disc. Another method is a hot press method under reduced pressure as shown in FIG.
8 are stacked one on top of the other, and with the pressure in the vacuum chamber 26 reduced by the exhaust system 27, they are thermocompressed by heatable upper and lower pedestals 24, 25 driven by movable shafts 22, 23. By any of the above methods, the transparent substrate and the film can be bonded without producing bubbles. The thermocompression bonding conditions at this time vary depending on the substrate, recording film, and photocurable adhesive resin used, but it is desirable that the temperature is below the heat deformation temperature of the substrate and the pressure is below ^15Kgcm2 . . Under conditions higher than this, deformation of the substrate is likely to occur. In step 2, ultraviolet rays are irradiated through the film pasted in step 1. Therefore, it is necessary for the plastic film to pass the light. By curing with ultraviolet rays, the optical recording film on the transparent substrate is protected by a strong bubble-free protection tank, which simplifies post-processing and greatly improves the reliability of the optical disc. In addition, as shown in FIG. 7, the adhesive tank 2
8, the adhesiveness does not go around to the transparent substrate 16 side and contaminate it, and since it is applied via the film 18 and the photocurable resin layer 18, it depends on the quality of the solvent resistance of the transparent substrate 16. You can choose the adhesive without any hassle. Furthermore, because of these protections, defects such as scratches on the optical recording film 17 can be significantly reduced. After applying the adhesive by roll, spray, gravure, brushing, etc. in step 3, the two disks are bonded together in step 4 with the optical recording layer facing inside and the center axes of both disks 7 aligned. Then, the plastic film is cured in step 5, and after curing, the excess plastic film is removed in step 6, thereby completing the optical disk of the present invention as shown in FIG. As the adhesive used in this step 3, a low-temperature curing adhesive is effective, and epoxy adhesives, acrylic adhesives, urethane adhesives, polybutadiene adhesives, and polyester adhesives are used. Among them, two-liquid non-mixable type (hereinafter referred to as SGA)
The adhesive is easy to use, and in this case, a method can be adopted in which the two components of the adhesive are applied separately to the two disks to be bonded together, which is very advantageous in terms of the process. Although the above embodiment has mainly described an optical disc using both sides of the disc, in the fourth step (bonding), an optical recording film is not used on one side, and the disc is intended to be used on one side. The manufacture of disks is also included in the invention. That is, in step 4, one transparent substrate 29 having a complete protective layer consisting of an ultraviolet curing resin layer 32 and a plastic film 33 is placed on the optical recording film 31 shown in FIG. In this case, the adhesive layer 34 may be an ultraviolet curing adhesive in addition to the various adhesives for double-sided discs described above. Next, a specific example will be explained. Specific example 1 On a methacrylic resin substrate (hereinafter referred to as PMMA substrate) with a pressure of 1.0 mm, an outer diameter of 200 mm, and an inner diameter of 35 mm, a wavelength of 800 ~
A Te-based thin film whose reflectance changes when a phase change is caused by an 850 mm laser beam is deposited, and on top of this, pressure is applied.
A 20μm thick acrylic photocurable resin layer on a 25μm polyester film with a softening point of 40~50℃
The adhesive film with the adhesive layer formed thereon was attached using the rubber roll described above. Roll condition is 80
°C and the pressure was 5 psi. Thereafter, the plastic film was cured by irradiating 300 mJ (millijoules) of ultraviolet light from the side. Next, the two components of the two-component mixed acrylic adhesive were applied with a rubber roller to the entire surface of the plastic film side of the two substrates having the above structure, each with a thickness of 5 μm, and then the central axes were aligned. They were bonded together in parallel and cured at room temperature. Next, the excess plastic film on the inner and outer peripheries was removed to complete the optical disk. The performance of this optical disk is shown in the table. Among performance, error rate is the frequency at which defective pits occur when writing is performed using a semiconductor laser with a wavelength of 820 mm focused at 1 μm, and the data is read.
It shows the average result for 100 sheets,
For example, 1×10 ⁻³ indicates one reading failure per 1000 pits. In addition, the yield is
This is the result of determining that a product with an error rate of 1×10 ^-4 or higher at the end of all processes is considered to be a good product. Humidity resistance is 60℃-
These are the results of visual observation of changes in the bonded area of the substrate after it was left under 90% RH for 7 days. Specific Example 2 The Te-based recording film of Specific Example 1 was deposited on a polycarbonate substrate (hereinafter referred to as Pc substrate) with a thickness of 1 mm, an outer diameter of 200 mm, and an inner diameter of 35 mm, and a 20 μm adhesive polybutadiene-based cured resin layer was added on top of this. formed thickness
A 15 μm polyester film was attached using a vacuum adhesive device shown in FIG. The conditions for pasting were a degree of vacuum of 1 torr, a pressure of 0.1 Kg/mm ² and a room temperature of 1 minute. After returning to normal pressure, a 2-component low-temperature curing epoxy resin mixed varnish was applied to a thickness of 30 μm on top of the film, which was cured with 500 mJ of ultraviolet light.
It was applied to m. A rubber roller was used for application.
On top of this, optical disk substrates having the same configuration were bonded together with their central axes aligned, pre-cured at 70°C for 5 minutes, and then main cured at room temperature for 24 hours.
A double-sided optical disc was manufactured by cutting off the excess film. The performance of this optical disk 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 35 mm, a film was attached and photocured in the same manner as in Example 1. 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 film was pasted was aligned with the central axis. They were aligned and brought into close contact with each other so that the optical recording film was on the inside, and cured with 300 mJ of ultraviolet light from the transparent substrate side.
After curing, the excess film was removed to complete a one-sided recording optical disc. The performance of this optical disk is shown in the table. (Reference example) 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.
Using a commercially available hot melt applicator,
Urethane hot melt adhesive was applied to a thickness of 30 μm. The roll temperature was 100°C. The two sets of transparent substrates coated with hot melt adhesive in this way were aligned with their central axes, the adhesive surfaces were brought into close contact with each other, and pressed for 5 minutes at a pressure of 5 kg/cm ² using a heat press at 100°C. I pasted it together. The performance of this optical disk is shown in the table. (Effects of the Invention) As is clear from the table, all optical disks manufactured using the method of the present invention have a lower incidence of pit reading errors than the conventional method using a general hot melt adhesive. It can be seen that this is an excellent manufacturing method that causes very little generation of bubbles near the recording film and little 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 a major contribution to the realization of highly reliable optical disks. It is something. 【table】

[Brief explanation of drawings]

FIG. 1 is a perspective view of an optical disc cut away and showing an enlarged part A, FIG. 2 is a sectional view of a conventional hot-melt adhesive disc, and FIG. 3 is a double-sided disc completed by the manufacturing method of the present invention. Cross-sectional view of the disk used,
Fig. 4 is an explanatory diagram of a state in which a film is pasted onto a substrate by a roller, Fig. 5 is a flowchart showing the process of the present invention, Fig. 6 is a diagram of a vacuum bonding device, and Fig. 7 is an illustration of adhesion. FIG. 8 is a cross-sectional view showing the state of application of the agent, and FIG. 8 is a cross-sectional view of a disc used on one side. 1... Completed disk, 2, 3, 7, 8, 16,
29,30...transparent substrate, 4,5,9,10,1
7, 31... Optical recording film, 6... Hot melt adhesive, 11, 12, 18, 32... Ultraviolet curing resin layer, 13, 14, 19, 33... Plastic film, 15, 28, 34... Adhesion agent layer, 20,
21...Heating roll, 22, 23...Movable shaft, 2
4, 25... Upper and lower pedestals, 26... Vacuum chamber, 27...
...Exhaust system.

Claims (1)

[Claims] 1. A transparent substrate on which an optical recording layer has been formed in advance is placed on a plastic film coated with a photocurable adhesive that is sticky at a temperature of 120°C or less on one side, with the optical recording layer inside. Paste the plastic film without creating bubbles, cure the photocurable adhesive with ultraviolet light, and then apply an adhesive that can be cured at low temperatures on top of the plastic film to create another transparent substrate or a single transparent substrate with the same structure. A method for manufacturing an optical disk, comprising the steps of: bonding the two pieces together with their central axes aligned with each other via the adhesive, curing the film, and then cutting off the excess plastic film. 2. The method for manufacturing an optical disk according to claim 1, characterized in that a heatable roll is used when attaching the plastic film to the transparent substrate. 3. The method for manufacturing an optical disk according to claim 1, wherein a press capable of heating under reduced pressure is used when attaching the plastic film to the transparent substrate. 4. Apply one component of a two-component, non-mixable, rapid-curing adhesive to one of the transparent substrates to which the plastic film has been pasted, and apply the adhesive onto the other film to which the plastic film has been pasted. 2. A method for manufacturing an optical disk according to claim 1, which comprises applying another component, bonding these components together, and curing them.