JPS63217544A - Production of information recording body - Google Patents

Abstract

PURPOSE:To produce an optical disk made into a sandwich structure having excellent flatness with high productivity by ultrasonically welding one disk substrate and spacer and adhering the 2nd sheet of the substrate to the 1st sheet by an adhesive agent. CONSTITUTION:The disk substrate 1 having a recording layer 5 on one face and the outside circumferential spacer 3 and inside circumferential space 4 are superposed on each other with the welding surfaces positioned on the inner side. The positions are properly adjusted by utilizing a center hole 6 at this time and thereafter, welding is executed by an ultrasonic horn. the adhesive agent is coated on the opposite surfaces of the substrate 1 and the two spacers 3, 4 and the 2nd sheet of the substrate 2 is adhered thereto. The 1st sheet is welded adjustably in position by the ultrasonic welding in such a manner and the 2nd sheet is prevented from cambering by the adhesive agent; therefore, the production of the laminated optical disk having the excellent flatness is permitted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing an optical information recording medium having an air sandwich structure.

[Conventional technology]

As an optical information recording medium (hereinafter abbreviated as an optical disk), particularly as a write-once optical disk, two disk substrates 1.2 each having a recording layer are arranged so that the recording layers face each other and a space is formed between them. A so-called air sandwich structure in which an outer circumferential spacer 3 and an inner circumferential spacer 4 are interposed and bonded is known (for example, "Optical Disc Molding Technology" published by Trikebbs, 198
6, P17-18.9i magazine "Optronics" published by Optronics, Vol. 43, 7, P66-76).

Conventionally, it has been proposed that the air sandwich structure optical disk be bonded to the substrate and the spacer by either adhesive bonding or ultrasonic fusion bonding.

[Problems with conventional technology]

When bonding with an adhesive, unless it is applied uniformly and pressure is applied uniformly to the entire surface to be bonded, unevenness in the thickness of the adhesive layer tends to occur and the flatness is likely to be impaired.

In particular, in the case of an air sandwich structure using a spacer, the adhesive surfaces between the upper and lower disk substrates and the spacer are added at two points in the thickness direction, so uneven thickness of the adhesive surface may impede the flatness of the optical disk. Strong tendency to give. Further, the time required for applying and curing the adhesive is also a cause of impeding high-speed productivity. Furthermore, there is a problem that the alignment between the first disk substrate and the spacer (and the outer circumferential spacer) is slightly difficult.In other words, when bonding the outer circumferential spacer and the disk substrate, which have already been coated with adhesive, even the slightest misalignment may occur. If they are joined at the same position, it will be difficult to correct them to the normal position because they will adhere to each other.Of course, since the adhesive has not yet hardened, it is possible to forcibly tear them apart, but if the adhesive This may cause the parts to move to the substrate side, impairing the appearance and flatness.With ultrasonic fusion, there is no adhesive, so even if the initial alignment of the disk substrate and outer spacer is slightly misaligned, the two will remain intact. By moving one of them, it can be easily corrected to the normal position, and there is no need for time for applying or curing adhesive, and the bonding is instantaneous, so it has the advantage of excellent high-speed productivity. However, there is a problem in that optical discs tend to warp due to distortion due to fusion, which can easily impair the flatness of the optical disc.In particular, warpage tends to occur greatly when the second disc substrate is fused, and the first When the second disk substrate and spacer are fused together, not much warping occurs.

[Problem that the invention seeks to solve]

The present invention aims to solve the following problems in manufacturing optical discs with an air sandwich structure using spacers, and specifically relates to a method for manufacturing optical discs with excellent flatness with high productivity.

[Means for solving problems]

That is, in the present invention, a disk substrate having a recording layer on one side, an outer circumferential spacer, and an inner circumferential spacer are stacked on top of each other so that the recording layer faces the side to be fused with the spacer, and these are fused using ultrasonic waves. This method of manufacturing an information recording medium having an air sandwich structure is characterized in that another disk substrate is then bonded to the opposite surface of both spacers using an adhesive.

[For production]

According to the present invention, since the first disk substrate and the spacer are bonded together using ultrasonic fusing means, even if there is a misalignment between the spacer and the substrate, it can be easily corrected. Moreover, the fusion action is completed in an extremely short time. Once one of the disk substrates and the spacer are fused together in the correct position, alignment when bonding the two disk substrates can be easily done by overlapping them using the center hole of the disk substrates. Therefore, by bonding the two disk substrates and the spacer using an adhesive, it is possible to manufacture an optical disk that is free from warpage and has excellent flatness. In other words, if the second disk substrate is bonded by ultrasonic welding, large warps will occur as described above and the flatness will be impaired. Even if this occurs, the effect of uneven thickness on flatness is smaller than when both sides are bonded with adhesive, and in fact, the flatness can be kept within the tolerance for flatness as an optical disc.

〔Example〕

The manufacturing method of the present invention will be explained based on typical examples.

As shown in FIG. 1, first, a disk substrate 1 having a recording layer 5 on one side, an outer circumferential spacer 3, and an inner circumferential spacer 4 are stacked so that the recording layer faces the side to which the spacer is fused. At this time, by aligning the inner circumferential spacer 4 and the substrate 1 using the center hole 6, the joint portion between them can be regulated to a normal position. On the other hand, the outer circumferential spacer 3 is fitted onto a base having a fitting portion to align with the substrate, but the width of the spacer is several millimeters and the thickness is 1 mm.
Since the size is less than a millimeter, often less than 0.5 millimeters, it is difficult to completely fix it by fitting, and it may be displaced from the fitted portion due to shock or vibration. Therefore, if necessary, the outer circumferential spacer position is corrected and adjusted to the normal position. Substrate 1 and both spacers 3.4
When they overlap in the normal position, an ultrasonic horn (not shown) is brought into contact with the bonding surfaces to perform fusion. At this time, a protrusion may be formed on the spacer so that the ultrasonic energy can be easily concentrated and can serve as a welding margin.

The optical disk in which the substrate 1 and both spacers 3.4 are fused in this manner is then bonded to the remaining disk substrate 2 by applying an adhesive to the opposite surfaces of both spacers. At this time, if the substrate 1 to which the spacer has already been fused and the substrate 2 to be bonded are overlapped using the center hole, the spacer and the substrate 2 will be overlapped in the normal position, and the alignment will be completed. It can be done easily and accurately.

In addition, in the present invention, if the grooves 7 are provided on both sides of the adhesive application surface of the outer circumferential spacer (Fig. 3), the excess adhesive will be pushed back during adhesion, and the spacer and the substrate will be It is possible to prevent the adhesive from protruding outside the adhesive surface, and to form an adhesive surface with a beautiful appearance.Furthermore, since the thickness of the adhesive layer is uniform, the flatness is also improved.

In addition, by utilizing this groove, a protrusion that can fit into the groove of the spacer is provided on the part of the base side that fits with the outer peripheral spacer when aligning with the substrate 1 during ultrasonic fusion bonding. This also has the effect that the spacer is less likely to move than the fitting portion of the base.

In the present invention, the plastics constituting the substrate and spacer are thermoplastic and have excellent transparency, such as polymethyl methacrylate, polycarbonate, and JP-A-6
Ethylene/cyclic olefin copolymers shown in No. 0-168708 are used.

In particular, ethylene/cyclic olefin copolymers have small birefringence, almost no change in birefringence due to changes in the incident angle of light, and a small photoelastic coefficient, so they have the characteristics of small optical distortion due to ultrasonic fusion. . Taking this ethylene/cyclic olefin copolymer as an example, the ethylene content in the copolymer constituting the substrate is 50 to 70 mol%, and the ethylene content in the copolymer constituting the spacer is 55 to 80 mol%.
If a copolymer composition is selected such that the ethylene content of the substrate is less than the ethylene content of the spacer, a product with particularly excellent flatness and fusion strength can be obtained. As the adhesive, a known adhesive is used, but preferably a UV-curable adhesive,
Among these, epoxy-based UV curable adhesives are used.

Below, the results of an experiment comparing the flatness of an optical disk manufactured by the present invention and an optical disk manufactured by a conventional method will be shown.

This experiment consisted of a recording layer made of ethylene/tetracyclododecene copolymer with a diameter of 130 m + 11 mm and a thickness of 1.2 mm.
1 disk substrate (ethylene content 62 mol%), outer diameter 130 m+, inner diameter 125+++ m, thickness 0.4 mm outer circumferential spacer and outer diameter 3GIllI11, inner diameter 15 n
The test was carried out using an inner spacer having a thickness of +m and a thickness of 0.4m+w (ethylene content in both spacers was 70 mol%). The flatness measurement was performed at 27 to 59 III from the center of the optical disc.
A He--Ne laser beam was irradiated from the vertical direction onto the optical disk surface over the radial distance of Ill, and the deviation angle of the reflected light from the vertical direction was measured. As a result, according to the method of the present invention, the manufacturing time was 30 seconds, and the flatness was 3.5 mradia.
On the other hand, the method using adhesive alone had a manufacturing time of 60 seconds and the flatness was 5 mradian, and the method using only ultrasonic fusion had a manufacturing time of 10 seconds and a flatness of 7 mradian.
It was adian.

Note that the ultrasonic fusion was performed using a Welder (model USWP-2400Z15S) manufactured by Ultrasonic Kogyo Co., Ltd., with a pressure of 1,
The test was carried out under the conditions of 0 kg/cj and a push-in amount of 100μ.

The adhesive is a UV curing type epoxy adhesive (Bis A type epoxy/sulfonium salt type, curing time: 1
5 seconds) was used.

〔Effect of the invention〕

According to the manufacturing method of the present invention, it is easy to align the disk substrate and the spacer, and an information recording medium having an air sandwich structure with excellent flatness can be manufactured with high productivity.

[Brief explanation of the drawing]

1 and 2 are views showing one step of the manufacturing method of the present invention, FIG. 3 is a view showing a cross section of a spacer, and FIG. 4 is a view showing a cross section of an information recording medium obtained by the present invention. 1.2...Disc substrate, 3.4...Spacer, 5...Recording layer, 6...Center hole applicant
Mitsui Petrochemical Industries Co., Ltd. Agent Kazu Yamaguchi 41st row'! , 1st prisoner 20th 3rd mother

Claims (1)

[Claims] (1) A disk substrate having a recording layer on one side, an outer circumferential spacer, and an inner circumferential spacer were placed one on top of the other so that the recording layer faced the side to be fused with the spacer, and they were fused using ultrasonic waves. A method for manufacturing an information recording medium having an air sandwich structure, characterized in that thereafter, another disk substrate is bonded to the opposite surface of both spacers using an adhesive.