JPS61151853A - Optical disk - Google Patents

Abstract

PURPOSE:To obtain an optical disk which can be produced easily without impairing a reflecting film and a substrate protection film and holds the signal bits with high accuracy, by using an anaerobic hardening type adhesive for bonding two optical disks. CONSTITUTION:Two acrylic resin optical disks 1 and 1a containing signal bits 1a and 1a' of recessing/projecting forms marked on each single side are produced by an injection molding process. Then Al layers 2 and 2' are formed on each signal surface by a vacuum vapor deposition process in the form of the reflecting films. Furthermore the protection films 3 and 3' of ultraviolet ray hardening acrylic resin are provided to both layers 2 and 2'. Thus two optical disks are obtained. Then an anaerobic hardening type adhesive 4 is applied on the films 3 and 3' by a spinner coating process. Then the surfaces of both protection films are adhered to each other. Thus the optical disk can be produced in a short time at a normal temperature. This produces no thermal distortion nor other types of stresses with no warp produced to the substrate. Furthermore the signal bit form can be held with high accuracy since the adhesive coated surface is not impaired.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to improvements in optical recording moonlight discs such as optical video discs or digital audio discs made by bonding two discs together.

[Technical background of the invention and its problems]

Generally, a double-sided reproducible optical disc has a substrate 10 made of synthetic resin such as acrylic, and has a signal pin (2) on which information is recorded on one side, and a layer of aluminum (mut) etc. is formed thereon. Another disk formed in the same way as the single-sided disk on which the reflective film 2 used was formed and the protective film 3 formed thereon was prepared, and both protective films were pasted facing each other with an adhesive 4 interposed therebetween. Manufactured together.

By the way, conventionally used adhesives for laminating the sheets include: (1) an adhesive prepared by dissolving rubber in a solvent; (2) an epoxy adhesive; Melt adhesive was used. However, these adhesives had the following problems. That is, (1) adhesives prepared by dissolving rubber in a solvent often corrode reflective films formed on synthetic resin substrates and signal pits, and the curing time required for adhesion is very long. (2) Although epoxy adhesives harden at room temperature, the process is complicated, such as mixing two components, and it takes a long time, one day or more, to completely harden. (3) Hot-melt adhesives harden quickly, but because the adhesive is used in a molten state, the heat from the adhesive heats up the disk, causing thermal distortion such as deformation and warping, resulting in the rotation of the disk. Surface runout is likely to occur. Further, since hot melt adhesives have high viscosity, the adhesive layer tends to be thick, and an expensive coating device is required to uniformly coat the adhesive layer. Each had their own drawbacks.

[Purpose of the invention]

The present invention has been made to solve the above problems, and can be easily manufactured without damaging the reflective film or the synthetic resin substrate protective film, and can retain signal pits in which information signals are recorded with high precision. The purpose of the present invention is to provide a two-disc laminated optical disc.

[Summary of the invention]

In the present invention, signal pits are formed using an anaerobic curing adhesive that polymerizes when the air is shut off.
The optical disc is characterized in that it is manufactured by laminating two discs together with a protective film that protects a reflective film provided on the surface on which signal pits are formed. That is,
The present invention has been discovered to use an anaerobic curing adhesive as the most suitable adhesive for bonding two disks together. As a result, optical discs can be bonded together in a short time, and as a result, deformation such as warping due to heat, which is a serious problem for optical discs, can be suppressed, so there is no damage to recorded signal pits or reflective films due to thermal deformation, or playback failure. will not occur. This adhesive is generally composed of tetraethylene glycol dimethacrylate monomer as its main component and a small amount of cumene hydroperoxide and benzoquinone, and polymerization progresses and hardens by blocking air. Because it turns into a thermosetting polymer, it has excellent heat resistance, solvent resistance, and oil resistance, has a relatively quick curing time, and is excellent in thinning the adhesive layer. At this time, the blending ratio of the components contained in the anaerobic curing adhesive is appropriately determined in consideration of its workability (viscosity, curing time), properties such as the adhesive layer, adhesive strength, etc. Also, this anaerobic curing adhesive As a method for applying the agent to the disk, it is preferable to use a conventional spinner coating method, screen printing method, etc. because it is simple.

Since the optical disc of the present invention can be bonded together at room temperature, warping of the disc substrate due to thermal distortion does not occur. Also, depending on the shape of the two disks being pasted together, the anaerobic adhesive may remain uncured on areas that come into direct contact with air, such as the outermost periphery and the inner periphery of the center hole for rotation. In such a case, the adhesive may be cured by using a dry box with an inert gas atmosphere, a vacuum desiccator, or the like, or by shielding it from air by covering it with tape or the like. Alternatively, an ultraviolet curing type adhesive having an anaerobic curing function may be used as the adhesive used in the present invention. In this case, ultraviolet irradiation can be used to harden the peripheral portion, etc. as described above.0 [Effects of the Invention] The optical disc according to the present invention uses an anaerobic curing adhesive to bond two discs together. Since it can be formed at room temperature in a shorter time, almost no thermal strain or other stress is applied, and no warping of the substrate occurs. In addition, the signal pit shape can be maintained with high precision because the surface to which the adhesive is applied is not attacked. Round disc made from acrylic resin using injection molding method. Its size was 1.2-1 in thickness, 3001 in outer diameter, and 35φ in center hole diameter. Next, a reflection film of about 0.0 mm was deposited on the signal surface of each of the two disks by vacuum deposition. A layer having a thickness of ip- was formed on each layer.Furthermore, a protective film made of ultraviolet curing type acrylic resin was formed to a thickness of 20#-0 on each M layer to obtain two discs. Next, apply an anaerobic curing adhesive (Arontai R, manufactured by Toagosei Kagaku Kogyo Co., Ltd.) on the protective film to a thickness of approximately 10 mm using a spinner coating method, and then overlap and bond the protective film surfaces. An optical disc according to the present invention was manufactured in this manner. The two discs adhere perfectly! ! The time it took was about 20 seconds.

On the other hand, as a comparative example, hot-melt adhesive (P
S-07.A (manufactured by C1 Company) was applied to a thickness of about 30 mm using a roll coater method, and the coated layers were stacked and bonded to explode the optical disc.

The time required for adhesion was approximately 2.5 minutes.

The signals written on the optical discs of the examples of the present invention and the comparative examples were played at 1800 r by an optical disc player.
Regeneration started at a rotation speed of pm. It was confirmed that the optical disc of the present invention did not cause any trouble during reproduction, and the warpage of the disc surface measured afterward was as small as 0.11 or less.

On the other hand, in the optical disc of the comparative example, the 2
Although the two discs were exactly the same as those used in the present invention, a phenomenon was observed in which collision between the optical disc and the pickup occurred during regeneration, making regeneration temporarily difficult. The optical disk of this comparative example had a warp of about 0.7 mm, which is thought to be due to the effect of heating during adhesion, and this is thought to have caused the collision between the optical disk and the pickup described above.

Example 2 In the same manner as in Example 1, four acrylic resin disks were prepared in which a reflective film and a protective film were formed on the information signal recording surface. An ultraviolet curing adhesive (TB3060, manufactured by ThreeBond Tower) with an anaerobic curing function was applied to the peritoneal membrane surface of two of these disks using a screen printing method, and the protective membrane surfaces were placed facing each other. Ta. Next, ultraviolet rays were irradiated in spots using an ultraviolet irradiation equipment (Toscure 200p, manufactured by Toshiba Electric Materials Corporation) to ensure adhesive curing in the outer solid portion and the vicinity of the center hole.

The time required to completely adhere the two disks was approximately 20 seconds. In addition, as a comparative example, the remaining two discs were pasted together using a chloroprene rubber-based solvent type adhesive (Cemedine 575; manufactured by Cemedine Co., Ltd.) to obtain a comparative optical disc. At this time, it took approximately 90 minutes for complete adhesion.

When both optical disks were observed 24 hours after adhesion, no changes were observed in the optical disk of the present invention, but fine cracks had occurred on the surface of the U layer in the optical disk of the comparative example, and the reflection Due to the damage to the membrane, normal playback of the disc was impossible.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of an optical disc made by laminating two discs on which information signals are recorded. 1.1... Substrate 1a + la... Signal pit 2.2... Reflective film 3.3... Protective film 4... Adhesive agent Patent attorney Kensuke Chika (and 1 other person) Figure 1

Claims (1)

[Claims] Two disks comprising a substrate made of synthetic resin on which signal pits are formed, a reflective film provided on the surface of the substrate on which the signal pits are formed, and a protective film further provided on the reflective film. An optical disk characterized in that the protective film surfaces of the two are bonded together using an anaerobic curing adhesive.