JPH0766570B2 - Information recording substrate and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention is an information recording substrate having an air soldering structure, which is excellent in handleability and exhibits very good adhesiveness when ultrasonic welding is used as an adhesive means. And its manufacturing method.

[Conventional technology]

As a write-once type optical disc, the Air Sun German structure is known. That is, as can be seen from the cross-sectional view shown in FIG. 1, two disk substrates are arranged with the outer peripheral spacer 3 and the inner peripheral spacer 4 interposed so that the recording layers 5 face each other and a space is formed therebetween. Bonding 1 and 2.

Heretofore, in manufacturing such an optical disc having an air sun-gate structure, the disc substrate and the spacer have been bonded together by using a thermosetting or UV-curing adhesive. However, when an adhesive is used, the monomer in the adhesive component and an excessive amount of the adhesive may adversely affect the recording layer. From this point, an adhesive method that does not use the adhesive is also being studied. Specifically, there is an example in which ultrasonic welding is applied as seen in JP-A-60-103537.

[Problems of conventional technology]

However, even if the above-mentioned ultrasonic welding is applied to manufacture an optical disk, there are the following problems.

That is, in the conventional optical disk, the same plastic material is used for the spacer and the disk substrate, and accordingly, a brittle material having high rigidity is used. When a disk substrate and a spacer made of plastic having such a property are ultrasonically welded, a spacer, especially a spacer having a small thickness and width and a large diameter, such as an outer peripheral spacer, may be cracked at the same time as welding by ultrasonic waves, and may be extremely sharp. In this case, the recording layer may be completely broken and fragments may fly off, damaging the recording layer.

[Problems to be solved by the invention]

One of the objects of the present invention is to provide an information recording substrate having an air-sintered structure, which is capable of fine welding even if ultrasonic welding is performed and has a high adhesive strength. Another object of the present invention is to provide an information recording substrate that is resistant to impact. Another object of the present invention is to provide an information recording substrate having a small birefringence. Still another object of the present invention is to provide an information recording substrate having excellent handleability. Still another object of the present invention is to provide a method for manufacturing an information recording substrate having the above properties by ultrasonic welding.

[Means for solving problems]

That is, the present invention is an information recording substrate having an air sandwich structure in which two disc substrates are adhered via an outer peripheral spacer and an inner peripheral spacer, and the spacer and the disc substrate are made of a material that can be ultrasonically welded. The information recording substrate is characterized in that the elastic modulus of the spacer is within a range of 20 to 90% of the elastic modulus of the disk substrate. Separately, two disk substrates are bonded via an outer peripheral spacer and an inner peripheral spacer. In an information recording substrate having an air sandwich structure, at least one of a plastic forming a spacer and a plastic forming a disk substrate is a copolymer of ethylene and a cyclic olefin, or a ring-opening polymer of a cyclic olefin, or hydrogenation thereof. And the elastic modulus of the spacer is 20 times that of the disk substrate.
The information recording substrate is characterized by being in the range of up to 90%. Furthermore, another method is a method of ultrasonically welding two disk substrates via an outer peripheral spacer and an inner peripheral spacer to manufacture an information recording substrate having an air-sandwich structure. This is a method for manufacturing an information recording substrate, which is characterized by using a material having an elastic modulus of 90%.

[Work]

Two disk substrates 1 constituting the information recording substrate of the present invention
2 and 2 may be basically any plastics that can be ultrasonically welded and have surface hardness and rigidity, such as polymethylmethacrylate, polycarbonate, polystyrene, poly-4-methylpentene-
1, ethylene and cyclic olefins such as norbornene,
Examples thereof include copolymers with tetracyclododecene, methyltetracyclododecene, and the like, ring-opening polymers of the above cyclic olefins, and hydrogenated products thereof. Especially elastic modulus 1 × 10 ^{4 to} 3.8 ×
A relatively hard and rigid material of 10 ⁴ kg / cm ² is preferable.

It is preferable that the outer peripheral spacer 3 and the inner peripheral spacer 4 are ultrasonically weldable and elastic to some extent. If you use a plastic that is as rigid as the disk substrate, cracks may enter during ultrasonic welding,
It breaks and fragments spatter. Therefore, a disc substrate having a modulus of elasticity of 20 to 90%, especially 30 to 80% is used. In order to further increase the adhesive strength, the spacer material is preferably 5 to 30 ° C. lower than the melting point or glass transition point of the plastics constituting the disk substrate, and more preferably the same as the plastics constituting the disk substrate, and particularly, Ethylene and cyclic olefins such as norbornene, tetracyclododecene,
A copolymer with methyltetracyclododecene or the like, a ring-opening polymer of the above cyclic olefin or a hydrogenated product thereof is preferable. If the melting point or glass transition point of the spacer material is within the above range, uniform welding can be performed at a relatively low temperature with respect to the substrate material at the time of welding with the disk substrate, so that there is no risk of substrate deformation or the like. Examples of such plastics include those mentioned above. However, since the spacer portion is not directly related to reading information, other non-transparent plastics may be used. The elastic modulus, the melting point or the glass transition point of the spacer is defined as described above because a proper optically readable information recording substrate cannot be obtained if it is too large or too small. That is,
If the elastic modulus is too small, the ultrasonic welding performance is deteriorated, and it is easy to deform and it becomes difficult to read. On the other hand, if it is too large, the residual stress at the time of welding cannot be completely absorbed and remains on the disk substrate, resulting in a large birefringence and making reading difficult. Also,
Some of them are fragile, and cracks may enter during welding, or broken pieces may scatter and damage the recording layer. If the melting point or the glass transition point is out of the above range, the adhesive strength generally tends to decrease.

To manufacture the information recording substrate, each spacer is provided between two disk substrates, and the joint surface between each spacer and each disk substrate is ultrasonically welded. At this time, the joint surfaces may be welded at the same time, but if the projected area is large and the thickness is thin and the material is relatively fragile like an information recording board, first weld the outer peripheral spacer and one disk board. (Fig. 2), then the two disk substrates are joined together via the inner peripheral spacer, and the joint surfaces are welded simultaneously from one direction (Fig. 3), and then the remaining outer peripheral spacer and the other disc substrate are joined together. It is preferable to weld the unwelded joint surface (Fig. 4) because the ultrasonic output can be reduced, cracking can be prevented, and the adhesive strength can be increased.

〔The invention's effect〕

According to the present invention, a clean adhesive surface without cracks or cracks can be obtained even by ultrasonic welding, the adhesive strength between the spacer and the disk substrate is large, and the spacer serves as a cushioning material, which is excellent in impact resistance, Therefore, it is possible to provide an information recording substrate which is excellent in handleability and in which the spacer absorbs the residual stress at the time of welding and prevents the birefringence from increasing due to the residual stress.

〔Example〕

The contents of the present invention will be described below with reference to preferable examples, but the present invention is not limited to these examples unless otherwise specified.

Examples 1 to 3 Two disc substrates having a diameter of 130 mm and a thickness of 1.2 mm made of the ethylene / tetracyclododecene copolymer shown in Table 1 and the ethylene / tetracyclododecene copolymer shown in Table 1 An information recording substrate of air soldering structure by ultrasonic welding using an outer diameter spacer with an outer diameter of 130 mm, an inner diameter of 125 mm and a thickness of approximately 0.4 mm and an inner diameter spacer of an outer diameter of 36 mm, an inner diameter of 15 mm and a thickness of approximately 0.4 mm. Was manufactured. Specifically, first, the outer peripheral spacer and one disk substrate are ultrasonically welded, and then the welded disk substrate of the outer peripheral spacer and the remaining one disk substrate are bonded through the inner peripheral spacer to bond the inner peripheral spacer. Parts were ultrasonically welded together, and then the remaining outer peripheral spacer and one disk substrate unwelded joint were ultrasonically welded (welding conditions are shown in Table 1). Was welded uniformly and was clean, and the welding strength was also good.

Comparative Example 1 The procedure of Example 1 was repeated, except that a disk substrate made of an ethylene / tetracyclododecene copolymer shown in Table 1 and a spacer were used. As shown in Table 1, the fusion spiro at the welded portion is protruding to the recording layer side or outside the disk substrate, the outer peripheral spacer is damaged, and the welding strength is poor, so that it is practically endurable. Well then.

[Brief description of drawings]

FIG. 1 is an embodiment diagram of an information recording substrate of the present invention, and FIGS. 2 to 4 are diagrams showing a manufacturing method. 1,2 …… Disk substrate, 3 …… Outer peripheral spacer 4 …… Inner peripheral spacer, 11 …… Ultrasonic horn

Claims (7)

[Claims] 1. An information recording substrate having an air sandwich structure in which two disc substrates are bonded via an outer peripheral spacer and an inner peripheral spacer, wherein the spacer and the disc substrate are made of a material that can be ultrasonically welded. An information recording substrate, wherein the elastic modulus of the spacer is in the range of 20 to 90% of the elastic modulus of the disk substrate. 2. An information recording substrate having an air sandwich structure in which two disc substrates are adhered to each other via an outer peripheral spacer and an inner peripheral spacer, wherein at least one of a plastic constituting the spacer and a plastic constituting the disc substrate is formed. A copolymer of ethylene and a cyclic olefin, or a ring-opening polymer of a cyclic olefin or a hydrogenated product thereof, and the elastic modulus of the spacer is in the range of 20 to 90% of the elastic modulus of the disk substrate. An information recording substrate. 3. The information recording substrate according to claim 1, wherein the melting point or glass transition point of the spacer is 5 to 30 ° C. lower than that of the disk substrate. 4. The information recording substrate according to any one of claims 1 to 3, wherein the material of the spacer is the same plastic as that of the disk substrate. 5. The elastic modulus of the disk substrate is 1 × 10 ^{4 to} 3.8 × 10.
The information recording substrate according to any one of claims 1 to ^{4, which has a} weight of ⁴ kg / cm ² . 6. A method for manufacturing an information recording substrate having an air sandwich structure by ultrasonically welding two disc substrates through an outer peripheral spacer and an inner peripheral spacer, wherein the spacer has a disc substrate elastic modulus of 20 to 90. A method for manufacturing an information recording substrate, characterized in that one having a modulus of elasticity is used. 7. The method for an information recording substrate according to claim 6, wherein the melting point or glass transition point of the spacer is lower than that of the disk substrate by 5 to 30 ° C.