JPH0323531A - Optical disk - Google Patents

Abstract

PURPOSE:To reduce time for curing and to improve reliability of the medium by sticking single-plate disks comprising a transparent disk substrate and thin film layers such as protective film and magnetic film with using a hotmelt adhesive and inteposing a film having little water absorption between the disks. CONSTITUTION:The single-plate disks 11a, 11b having thin film layers 12a, 12b such as protective films and magnetic films are coated with a hotmelt adhesive 13a, 13b and pressed to each other with interposing an org. or inorg. film having little water absorption. Since the org. or inorg. film 14 having little water absorption is interposed, it prevents moisture from intruding the disk to the thin film layers 12a, 12b and gives excellent moisture resistance to the disk. Thus, the obtd. optical disk has excellent workability and reliability with little water absorption.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical disc used in a data file device or the like that records and reproduces information using light such as a laser beam.

Conventional technology In recent years, optical disks have been developed as high-density, large-capacity memories. There are roughly two types of optical disc structures. One is a protective film on a transparent disc and! One is a single-plate structure in which a thin film layer such as an R-resistant film is formed and then coated with a resin, etc., and the other is a disc that has a thin film layer such as a protective film and a magnetic film, or a disc that has a thin film layer formed on it. This type is made by bonding a transparent disc with resin. The former is used in compact discs, etc., and has some problems with reliability such as disc life. The present invention relates to the latter.

Conventionally, two veneer disks on which a thin film layer such as a protective film and an fn film were formed were pasted together using an epoxy adhesive, etc., or hot melt resin was applied on the veneer disk, and another layer of hot melt resin was applied. A method of laminating the coated veneer disks by stacking them and pressing them together, or if one side is a transparent disk, apply a photocurable resin and bond them together, then shine UV light from the transparent disk side for 1.1 seconds to harden the resin. Many methods have been used to do this. For example, Japanese Patent Application Laid-Open No. 58-6536. Figure 3 is a cross-sectional view of an optical disk bonded using a conventional hot melt adhesive. In FIG. 3, 31a, 3lb are transparent disks, 32a. ．． 32b is i! of a protective film, a magnetic film, etc. The membrane layer 33 is a hot melt adhesive layer. As for the manufacturing method, the guide grooves on the stand bar are transferred onto a glass substrate using a photocurable resin to produce transparent substrates 31a and 31b, and then the transparent substrates 31a and 31b are printed. ! Fjl Ml layers 32a and 32b such as a film and a magnetic film are formed by the Subanotar method or the like to produce two veneer disks, and then a hot melt adhesive is applied onto the veneer disks using a roll coater. Within the oven time of hot-melt bonding, these two veneer disks are pressed and bonded together to form a hot-melt adhesive layer 33 to complete the optical disk. Problems to be Solved by the Invention However, when bonding uses thermosetting resins such as epoxy resins and photocurable resins as bonding adhesives, it takes a long time for the resin to harden, and problems occur during bonding. There was a problem with workability because the resin sometimes protruded. On the other hand, in the case of lamination using a hot melt adhesive, although it is superior in terms of workability, the hot melt adhesive has high water absorption, which causes deterioration of the magnetic film etc. in terms of reliability (especially moisture resistance). It had the secret title ゜ζ. In view of the above-mentioned problems, the present invention provides an optical disc that has excellent workability, low water absorption, and excellent faU properties. Means for Solving the Problems The present invention involves applying a hot-melt adhesive onto a veneer disk on which a thin ll2N film such as a protective film and a magnetic film is formed, and then applying a hot melt adhesive to the two veneer disks thus produced. This is an optical disc characterized by being pressed through a film made of a small amount of organic or inorganic matter. At this time, it is desirable that the film to be inserted has a thicker IPJ thickness on the inner and outer circumferences of the film. Function The present invention has the above-mentioned configuration 6, but the amount of the melt adhesive with high water absorption is small and the thin film layer is interposed with a film made of organic or inorganic material with low water absorption. It does not allow moisture to reach the top and has excellent moisture resistance. Especially for films with thicker inner and outer circumferences,
The effect will be significant. In addition, roll coating with hot melt adhesive is a very simple method that can reduce costs. EXAMPLE An example of the present invention will be described below with reference to the drawings. FIG. 1 shows a sectional view of a completed disk substrate according to an embodiment of the present invention. In Figure 1,
lla, 11. b is a transparent disk, 12a and 12b are thin film layers such as a protective film and a magnetic film, 13a and 13b are hot melt adhesive layers, and 14 is a film. Furthermore, Fig. 2 shows an overview of the film 14. The method for manufacturing optical discs is shown below. First, transparent substrates 11a and llb were fabricated by injection molding polycarbonate resin. Next, use the Subanotar device on top of this to protect it! SiN. Each yI film 11 is made of TbFeCo as the magnetic film and SiN as the second protective film! ! 2a and 12b were reproduced. Using a roll coater on Sarani and Konoyl film, apply ethylene/vinyl acetate based hot melt adhesive JiF13a.
, 13b (membrane I! 30pm) was reprimanded. Next, one single slope disc produced in this way was set in a press machine with a centering bottle, and the inner and outer peripheral film thicknesses were 15 and 16, loOIlm, and the center film thickness was 17.
A 70 μm vinylidene polyfluoride film 14 is placed on it,
Furthermore, he placed another single-plate disc on top of it and quickly pressed it within the oven time, completing the optical disc.

In addition, as film materials, organic materials with a water absorption rate of 0.1% or less, such as olefin polymers, fluorine polymers, and polyester polymers, or inorganic materials, such as yellow steel, were allowed to pass. The optical disc produced in this way was heated to 80°C at 280%.
As a result of the RH environmental test, no change was observed in BER and C/N even after 2000 hours. Comparing the environmental test results of the conventional configuration bonded using only hot melt adhesive and this example, it was found that with the conventional configuration, the magnetic film deteriorated within several hundred hours. EFFECTS OF THE INVENTION As shown in E, the present invention consists of two single-plate discs each having a thin film layer such as a protective film and a magnetic film on the transparent discs, and a film made of an organic or inorganic material with low water absorption. By bonding the discs with a photomelt adhesive, the curing time is short, less than 1 minute, there is almost no resin extrusion, the manufacturing process is simplified, and an optical disc with excellent reliability is provided.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an optical disk according to an embodiment of the present invention, FIG. 2 is a general view of a film, and FIG. 3 is a cross-sectional view of a conventional optical Y disk. 1 1 a. 1 l b--transparent disk, 12a, 1
2b... Thin film layer such as a protective film and a magnetic film, 13a
+3b...Honotomelt adhesive layer, 14...
···film.

Claims (2)

[Claims] (1) Two veneer disks each having a thin film layer such as a protective film and a magnetic film formed on a transparent disk are bonded together using a hot melt adhesive via a film made of organic or inorganic material with low water absorption. Characteristic optical disc. (2) The optical disc according to claim (1), wherein the film has a thicker film thickness on the inner and outer peripheries.