JPS628342A - optical disc - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Use The present invention relates to an optical disc using a laser.

Conventional technology An optical disk (hereinafter referred to as an optical disk) that uses a laser is a memory medium with a large capacity that can store tens of thousands of documents on a disk with a diameter of less than 30 α.
For this reason, the pits formed have a size of only about 1 μm. Furthermore, writing and reading information is performed 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. □In order to improve the reliability of optical discs, conventionally, as shown in cross section in Figure 2, on a transparent substrate 2 on which a thin film 3 for laser recording has been formed, another layer is attached using a hot melt adhesive 6. It had a structure in which transparent substrates 1 were bonded together. (Unexamined Japanese Patent Publication No. 68-6636 and “
"Introduction to Video Discs and DAD" edited by So Iwamura, published by Corona Publishing. ) Problems to be Solved by the Invention In optical discs using such conventional adhesive methods, if left in a high temperature dry atmosphere or a high temperature humid atmosphere, the adhesive surface of the disc may peel or impurities contained in the adhesive may occur. There was a problem in that the optical recording film corroded due to this. 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 uses a photocurable acrylic adhesive containing an epoxy prepolymer in its composition to adhere optical discs.

action 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 coloring and is flexible, 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 being exposed to high temperature and high humidity. This makes it possible to provide an excellent disc in which deterioration of the recording film can be minimized.

Example The present invention will be specifically explained 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 by ultraviolet light transmitted 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. I would like to mention scales that are also used for polyetherimide substrates, epoxy resin substrates, and p-glass substrates.

(Example 1) Polyester type polyfunctional acrylate (product name KAYA
Dissolve 1 g of benzyl dimethyl ketal in 10 g of Rum DHX-220, manufactured by Nippon Kayaku Co., Ltd., and dissolve 20 g of acrylic resin for paint (Dyanal BR-64゜Mitsubishi Rayon Co., Ltd.). , epoxy equivalent 1
Using an adhesive prepared by dissolving 5g of 80-200 bisphenol popular general-purpose epoxy prepolymer,
00+1ff, a 1.2-layer thick methacrylic resin substrate on which a low oxidized tellurium compound was vapor-deposited to a thickness of 0.10 μm, and a methacrylic resin substrate of the same size were attached so that the adhesive thickness was 60 to 100 pm. After matching,
An optical disk was manufactured by holding two substrates in parallel and irradiating them with ultraviolet light of 500 mJ/d. This optical disc was placed in a dry atmosphere at 80°C and at 70'C-80%RH.
Changes were observed after being left in a high-temperature, humid atmosphere. 200
The table shows the C/N reduction and appearance change of the disk after time elapsed.

(Example 2) Polyester type polyfunctional acrylate (product name: KAYA
RAD MAID Mu1 50FK (manufactured by Nippon Kayaku Co., Ltd.) was mixed with 50 gr of tetrahydrofurfuryl acrylate, and further a bisphenol human-type general-purpose epoxy brevolimer with an epoxy equivalent of 460 to 500 was added to s gr of acrylic resin for paints (Dianal). BR-64. supra) to 20
As in Example 1, a 0.10 μm low oxidation tellurium compound was deposited using an adhesive prepared by dissolving and mixing 1 gr of benzyl dimethyl ketal and 1 gr of benzyl dimethyl ketal.

A methacrylic substrate with a thickness of 1.2 mm and a transparent methacrylic substrate of the same shape were adhered under the same conditions as in Example 1 to produce an optical disk. The performance of this optical disc is shown in the table.

(Example 3) Polyester polyfunctional acrylate (KkYARADMA
70gr, tetrahydrofurfuryl acrylate side chain type epoxy prepolymer (EP-4000).

5 grams of Asahi Denka Kogyo Co., Ltd.) and 20 grams of acrylic resin for paint (C Tykina/I/BR-64)
r.

A methacrylic resin substrate with a diameter of 200 WM, a thickness of 1.2 ff, and W on which a 0.1 μm thick low-oxidation tellurium compound was deposited using an adhesive prepared by dissolving and mixing 1 gr of benzyl dimethyl tital and a transparent methacrylic substrate of the same shape. were adhered under the same conditions as in Example 1 to produce an optical disc. The performance is shown in the table.

(Example 4) Polyester polyfunctional acrylate (KAYARADMA
An optical disk was manufactured using the same materials and conditions as in Example 1 using an adhesive prepared by dissolving and mixing 70 gr of tetrahydrofurfuryl acrylates phenol A type general-purpose epoxy resin, and 1 gr of benzyl dimethyl tital. The performance is shown in the table.

(Comparative Example 1) Polyester type polyfunctional acrylate (KAYARAD
HX-220), 20 gr of acrylic resin for paint (Diamond) --/L/BR-64), and 1 gr of benzyl dimethyl tital were dissolved and mixed to make an adhesive, and an optical disc was prepared according to Example 1. did.

The performance is shown in the table.

(Comparative Example 2) Using a commercially available ICVA hot melt adhesive,
200 fl in diameter, with micron low oxidation tellurium compound vapor-deposited,
An optical disk was manufactured by bonding a totacryl resin substrate with a thickness of 12 ffl and a methane IJ/silica resin substrate of the same shape, and its performance was evaluated. The results are shown in the full table.

Effects of the Invention The optical disc according to the present invention has high reliability, unlike conventional discs, with no fatal defects such as peeling of the substrate or ohm corrosion of the recording film even after a life test, and a change in C/H within 1 dB. are doing.

That is, the present invention makes it possible to provide a high-performance and highly reliable optical disc.

[Brief explanation of the drawing]

FIG. 1 is an enlarged sectional view of an optical disc according to an embodiment of the present invention;
FIG. 2 is an enlarged sectional view of a conventional optical disc. 1, 2... Transparent substrate, 3... Optical recording film, 4... Anti-corrosion adhesive, 6... Hot melt adhesive.

Claims (3)

[Claims] (1) A disk with a recording film that can be written and read by a laser beam, and a disk made of a transparent base material with the same shape but no recording film, are made by using an epoxy prepolymer to maintain flexibility even after curing. An optical disc that is bonded together using a photocurable acrylic adhesive. (2) The optical disk according to claim 1, wherein the photocurable acrylic adhesive is an acrylic monomer alone or a composition of a polymer thickener and an acrylic monomer with an ultraviolet initiator added. . (3) The optical disc according to claim 1, wherein the acrylic monomer is a polyester type polyfunctional acrylate alone or a mixture of this and tetrahydrofurfuryl acrylate.