JPH03256247A - Optical disk - Google Patents

Abstract

PURPOSE:To shorten the time required for production of the optical disk and to obtain excellent shearing stress resistance by executing the adhesion of annular spacers and substrates of the air sandwich type optical disk via annular pressure-sensitive adhesive members and constituting the adhesive members of an acrylic adhesive. CONSTITUTION:The outer peripheral spacer 2 is held in place via the annular adhesive members 13 between a pair of substrates 5 and 6 provided on both substrates of which signal recording layers face the internal space, by which the optical disk is formed. The difference of this disk from the conventional disks lies in that the adhesive layers 31b consist of the acrylic pressure sensitive adhesive. The annular adhesive members 13 having such adhesive layers 13b are so formed that one main surface of the adhesives is previously stuck to the substrate carrying surface of the inner and outer peripheral spacers and the other adhesive layer surface is protected by the separator at the time of templating and molding the spacers consisting of, for example, polycarbonate. The need for the time for waiting the curing of the adhesives is eliminated and the optical disk having the excellent resistant characteristic to the shearing stresses of a pair of the substrates is obtd.

Description

TECHNICAL FIELD The present invention relates to an optical disc, and more particularly to a so-called air sandwich type optical disc in which a space is provided facing an internal signal recording layer.

BACKGROUND ART Write-once optical discs have been known as air sandwich optical discs in which the signal recording layer is, for example, a thin organic dye film.

Such an optical disc is disclosed in Japanese Patent Application No. 1-1 filed by the applicant of the present application.
As disclosed in Japanese Patent No. 1286, there is an optical disk in which a circular substrate and an annular spacer are bonded to each other via a pressure-sensitive adhesive layer in order to facilitate manufacturing. The annular shape of such an optical disc is as shown in FIG. 2(c).
An outer annular spacer 2 is sandwiched between a pair of circular substrates 5 and 6 with an annular adhesive member 13 interposed therebetween. The signal recording layer 4 is provided on both substrates facing the internal space.

The circular substrate 5.6 is made of a plastic material such as PMMA (polymethyl methacrylate) or PC (polycarbonate).

As shown in the partially enlarged cross-sectional view of FIG. 1, the annular adhesive member 13 in the peripheral portion near the spacer 2 is a so-called double-sided adhesive tape, and has a base material 13a made of a polyester film and both opposing support surfaces of the base material. A silicone-based pressure-sensitive adhesive layer 13 consisting of two silicone rubbers arranged in
(silicon adhesive member).

In the case of forming such an optical disc, FIG. 2(a)
Assembling is performed in the order of steps as shown in f).

First, as shown in FIG. 2(a), the substrate 5 is placed with the signal recording layer facing upward, and the annular adhesive member 13 is placed on it.
Separator (protective tape) 14 from above one side of the substrate supporting surface of
A pair of inner and outer circumferential spacers 1 and 2 from which parts a have been removed are aligned and positioned and fixed.

Next, as shown in FIG. 2(b), the separator 14b is peeled off from the other substrate supporting surface on the annular adhesive side 13, and the substrate 6 carrying the signal recording layer 4 is placed so that the signal recording layer faces downward. Press and fix while aligning the center (Fig. 2 (c)
) to obtain an air sandwich type optical disc.

However, in such an optical disk, when a force is applied to the peripheral portion due to centrifugal force or its own weight, a problem arises in that a shift occurs between the substrate and the spacer at the peripheral portion.

Although this force is weak, it applies a load to the optical disk over a long period of time, and this shift causes the optical disk to become deformed and eccentric, resulting in more errors when recording and reproducing data.

Summary of the Invention [Object of the Invention] An object of the present invention is to provide an air sandwich type optical disk that is easy to manufacture and strong.

[Structure of the Invention] The optical disc of the present invention includes a pair of circular substrates, at least one of which has a signal recording layer, and an outer circumference and an inner circumference of the circular substrates so as to face each other in parallel so that the signal recording layer is on the inside. An optical disc comprising an annular spacer supported by each, and a pressure-sensitive adhesive layer for fixing the circular substrate and the annular spacer to each other, characterized in that the pressure-sensitive adhesive layer is made of an acrylic adhesive.

[Operation of the Invention] According to the invention having such a configuration, in the air sandwich type optical disk, the resistance to shear stress in the pair of substrates is improved.

Example Embodiments of the present invention will be described below with reference to the drawings.

The optical disc of this embodiment has almost the same configuration as that shown in FIG. An optical disc is formed by sandwiching an outer circumferential annular spacer 2 between a pair of substrates 5 and 6 provided on the circumferential substrate with the signal recording layer facing the internal space with an annular adhesive member 13 interposed therebetween.

The optical disc of this embodiment differs from conventional ones in that the first
The adhesive layer 13b shown in the figure is made of an acrylic pressure-sensitive adhesive.

- When the annular adhesive member 13 (acrylic adhesive member) having the acrylic pressure-sensitive adhesive layer 13b is molded into a spacer made of, for example, PC, one main surface of the adhesive layer is preliminarily attached to the inner and outer peripheral spacers. The adhesive layer is attached to the substrate supporting surface, and the other adhesive layer surface is protected by a separator (release paper or protective tape).

In this case, when punching and molding the spacer, the pressure-sensitive adhesive layer side of the separator carrying a thick acrylic pressure-sensitive adhesive layer is attached to the substrate-supporting surfaces of the inner and outer peripheral spacers. It goes without saying that the acrylic adhesive layer should be selected from one that does not corrode the recording film.

Assuming that an acrylic substrate such as PMMA and a PC board are bonded using a PC annular spacer, the adhesion performance between the acrylic adhesive member used in this example and the conventional silicon adhesive member for optical discs will be shown below.

As shown in FIG. 3, a PC board 22 is bonded to a PMMA board 20 with a PC board piece 21 (spacer) interposed therebetween via an adhesive member 13 made of an acrylic adhesive layer according to the present embodiment.
A sample of 010mm x 20mm was made and heated to
The acrylic substrate 20 and the PC board 22 are placed in a 0°C atmosphere.
A predetermined load (100 g/
A creep test was conducted to measure these deviation distances by multiplying by cm2).

FIG. 4 is a graph showing the change in the displacement distance between the acrylic substrate 20 and the PC board 22 with respect to the holding time in this creep test.

Similarly, a sample shown in FIG. 3 was prepared for a conventional silicon adhesive assembly of an optical disk, and a creep test was conducted under the same conditions as described above, to obtain a graph of changes in deviation distance as shown in FIG.

As is clear from FIGS. 4 and 5, the acrylic adhesive member of this embodiment has a smaller deviation distance than the silicon adhesive assembly of the conventional optical disc.

Further, environmental acceleration tests were conducted on the optical disc of the example and the conventional disc. For example, the test conditions are 70℃,
Even after 500 hours have passed at 90% R, H, the deviation distance of this embodiment is about 3/1.00 of the conventional deviation distance on average.
It was found that the deviation distance of this example was smaller than that of the conventional optical disk.

Further, although the optical disc of the above embodiment had the annular adhesive member 13 made of only a single layer of acrylic adhesive, the annular adhesive member 13 was made of polyester film, polyethylene terephthalate, etc., as in the conventional one. The first and second adhesive layers 13b may be formed of a base material 13a, and first and second adhesive layers 13b made of an acrylic pressure-sensitive adhesive and disposed on both opposing supporting surfaces of the base material.

Effects of the Invention As described above, according to the present invention, the annular spacer and the substrate of the air sandwich type optical disk are bonded through an annular pressure-sensitive adhesive member, and the annular pressure-sensitive adhesive member is made of an acrylic adhesive. Therefore, there is no need to wait for the adhesive to harden, and the time required to manufacture the optical disc can be shortened, and it is also possible to obtain an optical disc in which the pair of substrates has better resistance to shear stress than conventional discs.

[Brief explanation of drawings]

Fig. 1 is a partially enlarged sectional view of an optical disc, Fig. 2 is a partially cutaway perspective view for explaining the assembly process of the optical disc, and Fig. 3 is a measurement of the displacement distance of a substrate bonded by a bonding hole made of an adhesive layer. FIG. 4 is a cross-sectional view of a sample for a creep test. FIG. 4 is a graph showing changes in the displacement distance between the acrylic substrate and the PC board with respect to the holding time in the creep test for the optical disk according to the present invention. FIG. It is a graph showing changes in the displacement distance between the acrylic substrate and the PC board with respect to the holding time. Explanation of symbols of main parts 1.2... Spacer 5.6... Substrate 13... Annular adhesive member

Claims (4)

[Claims] (1) a pair of circular substrates, at least one of which has a signal recording layer; an annular spacer supporting the outer and inner circumferences of the circular substrates so as to face each other in parallel with the signal recording layer on the inside; 1. An optical disc comprising a pressure-sensitive adhesive layer that adheres a circular substrate and an annular spacer to each other, wherein the pressure-sensitive adhesive layer is comprised of an acrylic adhesive. (2) The optical disc according to claim 1, wherein the pressure-sensitive adhesive layer comprises a base material and first and second pressure-sensitive adhesive layers sandwiching the base material. (3) The optical disc according to claim 2, wherein the base material is made of polyester or polyethyl terephthalate. (4) The optical disc according to any one of claims 1 to 3, wherein the annular spacer is made of polycarbonate.