JPH0283874A - Optical recording medium - Google Patents

Abstract

PURPOSE:To improve the adherence of a substrate and a hub by fixing a hub to a substrate with the 2-layer construction adhesives and making the value of respective linear expansion coefficients into a special sequence. CONSTITUTION:A hub 4 and a disk substrate 1 to coat a first adhesives and form a first bonding layer 9 are positioned and fixed with second adhesives to form a second bonding layer 10. The linear expansion coefficient of respective raw materials at this time is combined so as to become the hub 4 > layer 10 > layer 9 > substrate 1 or the hub 4 < layer 10 < layer 9 < substrate 1. Thus, when the formed optical recording medium is rotated by a recording and reproducing device, the circle formed by a tracking guide 3 is not decentered and can be rotated, for that reason, the correct recording and reproducing can be executed and the adherence of the substrate 1 and the hub 4 can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an adhesive structure for a hub of an optical recording medium that can perform recording, reproduction, erasing, etc. using a light beam.

[Prior Art] Conventionally, a recording layer made of an optical memory material that utilizes the magneto-optic effect, photochromism, phase transition from amorphous to crystalline, etc. is laminated on a substrate on which a tracking guide (guide groove) is formed. Optical recording media are known. As shown in FIG. 2, the conventional optical recording medium is a donut-shaped dowel-shaped recording medium with an inner diameter smaller than the center hole 2 of the substrate 1 in order to correct the eccentricity of the center hole 2 of the substrate 1 and the tracking guide 3. A hub 4 having a flat surface was fixed to a substrate 1 with an adhesive 5.

[Problems to be Solved by the Invention] As shown in Figure 6, the adhesive area between the disk substrate and the hub is not very large, and as a result, the disk may be exposed to shocks or stored in high temperature and high humidity environments. If the disc substrate is made of glass and the hub is made of plastic such as polycarbonate or epoxy resin, the adhesive part may easily peel off. The difference in expansion coefficient caused the bonded parts to peel off. To solve this problem, adhesives with viscoelastic properties are used to absorb impact forces and expansion and contraction caused by differences in expansion coefficients between different materials. If the hub is warped or deformed, there will be an extremely thin part in the adhesive layer, and this part will not have the cushioning effect to absorb expansion and contraction due to impact and differences in expansion coefficients, resulting in peeling. .

The present invention was made in view of the related problems,
The purpose of this is to allow the circle formed by the tracking guide to rotate without eccentricity when rotated by a recording/reproducing device, thereby allowing accurate recording/reproducing and improving the adhesion between the board and the knob. The object of the present invention is to provide an optical recording medium that can be improved.

[Means for Solving the Problems] The optical recording medium of the present invention capable of achieving the above object is an optical recording medium in which a hub is disposed at the center of a disk substrate, in which the hub is attached to a first adhesive layer, a first It is fixed to the substrate with a two-layer adhesive consisting of two adhesive layers, and the values of the linear expansion coefficients of each are determined by the knob, the first adhesive layer, the second adhesive layer, the disk substrate, or The disk substrate is characterized by a hub, a first adhesive layer, and a second adhesive layer.

The present invention will be explained in more detail with reference to the drawings.

FIG. 1 shows a schematic cross-sectional view of the optical recording medium of the present invention, in which a tracking guide 3 is formed on a disk substrate 1'' by the 2P method.

An optically recordable and reproducible recording layer 6 is formed on the surface of the substrate 1 on which the tracking guide 3 is formed, and an adhesive 7 is formed thereon.
It is bonded to the backing substrate 8 at. The first adhesive is applied to the fixed surface side of the hub 4 using a spinner or the like and cured. Next, the hub 4 on which the first adhesive layer 9 has been formed and the disk substrate 1 are aligned so that the center circle of the hub 4 is concentric with the tracking guide 3 of the substrate 1, and the second adhesive layer 10 is applied. It is fixed with the second adhesive formed. At this time, the linear expansion coefficient of each material is determined so that the combination becomes hub>first adhesive layer>second adhesive layer>disc substrate, or hub>first adhesive layer<second adhesive layer>disk substrate. It is necessary.

The substrate that can be used in the present invention is any substrate that is normally used for optical recording media, such as glass, polycarbonate, acrylic resin, and epoxy resin.

The hub can also be made of plastics such as polycarbonate resin, acrylic resin, epoxy resin, ABS, or urethane, or metals such as stainless steel, aluminum, or nickel.

Also, any known adhesive such as ultraviolet curing type, thermosetting type, two-component curing type, epoxy, urethane, acrylic, etc. can be used as long as it has a coefficient of linear expansion between that of the substrate and the hub. It is possible. Regarding the thickness of the adhesive, it is sufficient that the total thickness of the two layers is 30 to 200 μm.

[Example] Hereinafter, the present invention will be specifically explained by showing examples.

A linear expansion coefficient of 3 x 10-5 (c
m/cm/”C) of the first ultraviolet curing adhesive about 3
It was applied to a thickness of 0 μm and cured with ultraviolet light. Align the hub to the center of a glass substrate with an inner diameter of 15φ and an outer diameter of 130φ so that it is concentric with the tracking guide,
Linear expansion coefficient lXl0-5 (CIll/Cl11/°C)
It was fixed with a second UV-curable adhesive (thickness: 30 μl).

For comparison, Comparative Example 1 in which the substrate and hub were fixed only with the first UV-curable adhesive (60 μm thick) and Comparative Example 1 in which they were fixed only with the second UV-curable adhesive (60 μm thick). 2 was prepared and placed in an environmental testing machine at high temperature and high humidity, and the occurrence of peeling of the adhesive layer was observed. The results are shown in Table 1.

Table 1 The substrate of the optical recording medium of Example 1 is a polycarbonate injection substrate, the hub is a stainless steel hub,
The first adhesive layer has a linear expansion coefficient of 4 x 10-5 (cm/cm/
Example 1 except that the adhesive (thickness: 50 μm) with a linear expansion coefficient of 3×10 (cm/cm/-C) was used as the second adhesive layer for the adhesive (thickness: 50 μm) of “C)” An optical recording medium was produced in the same manner.

For comparison, Comparative Example 3 in which the substrate and hub were fixed only with the first UV-curable adhesive (100 μm thick) and Comparative Example 3 in which they were fixed only with the second UV-curable adhesive (100 μm thick). 4 was prepared and placed in a high-temperature, high-humidity environmental testing machine, and the occurrence of peeling of the adhesive layer was observed. The results are shown in Table 2.

Table 2 shows that the circle formed by the tracking guide can be rotated without eccentricity when rotated by a recording/reproducing device, and
Therefore, it has become important to provide an optical recording medium that allows accurate recording and reproduction and improves the adhesion between the substrate and the hub.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of the optical recording medium of the present invention, FIG. 2 is a schematic sectional view of a conventional optical recording medium, and FIG. 3 is a schematic partial enlarged view of the conventional optical recording medium. 1... Board 2... Center hole 3.
...Tracking guide 4...Hub 5...
Conventional adhesive layer 6...Recording layer 7...Adhesive (substrate bonding) 8...Backing substrate 9...First adhesive layer 10...Second adhesive layer [Effects of the invention] ]

Claims (1)

[Claims] In an optical recording medium in which a hub is disposed in the center of a disk substrate, the hub is fixed to the substrate with a two-layer adhesive consisting of a first adhesive layer and a second adhesive layer, and
A light characterized in that the values of the linear expansion coefficients of each are hub > first adhesive layer > second adhesive layer > disk substrate, or hub < first adhesive layer < second adhesive layer < disk substrate. recoding media.