JPH0584577B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to an optical disk using a laser. Conventional technology Optical disks using lasers (hereinafter referred to as optical disks) are placed on disks with a diameter of less than 30 cm.
It is a memory medium with a large capacity that can store tens of thousands of A4 documents, so the pits formed are only around 1 μm in size. Furthermore, writing and reading information is carried out by focusing a laser beam narrowed to a diameter of around 1 μm onto a disk that is rotating at high speed, and detecting the position and adjusting the focus. Small scratches, foreign objects, deformation of the board, warping, deviations in parallelism, etc. can cause signal errors. Therefore, when manufacturing optical disks, the same level of care is required as when manufacturing semiconductors. Conventionally, in order to improve the reliability of optical discs, as shown in the cross section in FIG. It had a structure in which substrates 1 were bonded together. (Described in JP-A-58-6536 and "Introduction to Video Discs and DAD" edited by So Iwamura and published by Corona Publishing) Problems to be solved by the invention Disks have had problems in that when left in a high temperature dry atmosphere or a high temperature humid atmosphere, the adhesive surface of the disk may peel off or the optical recording film may corrode due to impurities contained in the adhesive. The present invention has been made in view of this point, and an object of the present invention is to provide a highly reliable optical disc. Means for Solving the Problems In order to solve the above problems, the present invention provides adhesives for optical discs using photocurable acrylic adhesives containing bisphenol A type and side chain type epoxy prepolymers in the composition. This is done using a drug. Effect The effect of this technical means is as follows. That is, an acrylic photocurable adhesive containing an epoxy prepolymer is applied onto a transparent substrate on which an optical recording film is formed, and a transparent substrate with a protective role is bonded on top of this, and the two substrates are bonded together. The adhesive is solidified by irradiating ultraviolet light while maintaining parallelism. At this time, the cured acrylic adhesive has little coloration and has plasticity, so there is no deformation of the substrate due to curing shrinkage or stress concentration on the recording film, and the action of the epoxy prepolymer prevents it from forming under high temperature and high humidity conditions. It becomes possible to provide an excellent disk that can minimize the deterioration of the recording film. EXAMPLES The present invention will be specifically described below. In FIG. 1, a cross-sectional view illustrates a state in which a transparent substrate 2 having an optical recording layer 3 formed on its surface and a transparent substrate 1 having a protective role are adhered with the anticorrosive photocurable adhesive 4 of the present invention. ing. The adhesive 4 is cured using ultraviolet light that passes through the transparent substrate 1. The manner in which corrosion progresses in a high-temperature, high-humidity atmosphere differs depending on the materials of the substrates 1 and 2, and if either one of the substrates is moisture permeable, corrosion occurs over the entire surface of the optical recording layer. If both substrates are not moisture permeable, such as glass, corrosion is observed from the edges of the bond. In the examples, an example is shown in which a transparent substrate made of methacrylic resin is used in order to evaluate the observation of corrosion under accelerated conditions, but in reality, the adhesive of the present invention can be used on polycarbonate resin substrates, in addition to methacrylic resin substrates. It should be mentioned that it can also be used for polyetherimide substrates, epoxy resin substrates, and glass substrates. (Example 1) Polyester type polyfunctional acrylate (trade name;
Dissolve 1 g of benzyl dimethyl ketal in 100 g of KAYARAD HX-220, manufactured by Nippon Kayaku Co., Ltd., and dissolve 20 g of acrylic resin for paint (Dyanal BR-64, manufactured by Mitsubishi Rayon Co., Ltd.). Using an adhesive prepared by dissolving 5 g of bisphenol A type general-purpose epoxy prepolymer with an epoxy equivalent of 180 to 200, a low-oxidation tellurium compound was vapor-deposited to a thickness of 0.10 μm on a methacrylic resin substrate with a diameter of 200 mm and a thickness of 1.2 mm. After bonding the object and a methacrylic resin substrate of the same size so that the adhesive thickness is 50 to 100 μm, the two substrates are kept parallel and the
An optical disk was manufactured by irradiating it with 500 mJ/cm ² of ultraviolet light. This optical disk is placed in a dry atmosphere at 80℃,
Changes were observed after being left in a high-temperature and humid atmosphere at 70°C and 80% RH. The table shows the C/N reduction and appearance change of the disk after 200 hours. (Example 2) Polyester type polyfunctional acrylate (trade name;
50g of tetrahydrofurfuryl acrylate for 50g of KAYARAD MANDA (manufactured by Nippon Kayaku Co., Ltd.)
Mix and further add 5 g of bisphenol A general-purpose epoxy prepolymer with an epoxy equivalent of 450 to 500, and acrylic resin for paints (Dianal BR-64, mentioned above).
Using an adhesive prepared by dissolving and mixing 20gr of and 1gr of benzyldimethylketanol, the same methacrylic substrate with a diameter of 200mm and a thickness of 1.2mm was coated with a 0.10μm low oxidation tellurium compound by vapor deposition, as in Example 1. A shaped transparent methacrylic substrate was adhered under the same conditions as in Example 1 to produce an optical disk.
The performance of this optical disk is shown in the table. (Example 3) Polyester type polyfunctional acrylate (KAYARAD MANDA) 70gr, tetrahydrofurfuryl acrylate 30gr, epoxy equivalent 310~
340 side chain type epoxy prepolymer (EP-4000,
A low oxidation tellurium compound with a thickness of 0.1μm is made using an adhesive made by dissolving and mixing 5gr of Asahi Denka Kogyo Co., Ltd.), 20gr of acrylic resin for paint (Dianal BR-64), and 1gr of benzyl dimethyl ketanol. A methacrylic substrate with a diameter of 200 mm and a thickness of 1.2 mm on which the methacrylate was deposited was bonded to a transparent methacrylic substrate of the same shape under the same conditions as in Example 1 to produce an optical disk. The performance is shown in the table. (Example 4) Polyester type polyfunctional acrylate (KAYARAD MANDA) 70gr, tetrahydrofurfuryl acrylate 30gr, epoxy equivalent 450~
500 bisphenol A type general purpose epoxy resin 10gr,
Furthermore, the same material method as in Example 1 was applied using an adhesive in which 1gr of benzyl dimethyl tital was dissolved and mixed.
Optical discs were manufactured under the following conditions. The performance is shown in the table. (Comparative Example 1) 100gr of polyester type polyfunctional acrylate (KAYARAD HX-220), 20gr of acrylic resin for paint (Dyanal BR-64), and 1gr of benzyl dimethyl titanol were dissolved and mixed to make an adhesive, Example An optical disc was prepared according to 1. The performance is shown in the table. (Comparative Example 2) Using a commercially available EVA hot melt adhesive,
Diameter 200 with 0.1 μm low oxidation tellurium compound deposited
An optical disk was manufactured by bonding a totacryl resin substrate with a thickness of 12 mm and a methacrylic resin substrate of the same shape, and its performance was evaluated. The results are shown in the table.

[Table] Effects of the Invention The optical disk according to the present invention has no fatal defects such as peeling of the substrate or corrosion of the recording film even after the life test, and the C/N change is within ±1 dB, which is higher than the conventional example. It has reliability. That is, the present invention makes it possible to provide a high performance and highly reliable optical disk.

[Brief explanation of the drawing]

FIG. 1 is an enlarged sectional view of an optical disk according to an embodiment of the present invention, and FIG. 2 is an enlarged sectional view of a conventional optical disk. 1, 2...Transparent substrate, 3...Optical recording film, 4...
Anticorrosion adhesive, 5...Hot melt adhesive.

Claims (1)

[Scope of Claims] 1. A disc having a recording film that can be written and read by a laser beam, and a disc made of a transparent substrate having the same shape but no recording film, are cured by containing an epoxy prepolymer. An optical disk that is bonded together using a photocurable acrylic adhesive composition that also has plasticity. 2. The photocurable acrylic adhesive composition according to claim 1, wherein the photocurable acrylic adhesive composition is an acrylic monomer alone or a composition of a polymer thickener and an acrylic monomer, with an ultraviolet initiator added. disc. 3. The optical disk according to claim 2, wherein the acrylic monomer is a polyester type polyfunctional acrylate alone or a mixture of this and tetrahydrofurfuryl acrylate.