JP2519993B2 - Method for manufacturing optical recording medium - Google Patents

Description

The present invention relates to a method for manufacturing an optical recording medium capable of recording and reproducing with a light beam. More specifically, the present invention relates to a method for manufacturing an optical recording medium in which warp deformation of a substrate is small.

(Prior Art) Conventionally, a recording layer made of an optical memory material utilizing a magneto-optical effect, photochromism, phase transition from amorphous to crystalline, etc. is laminated on a plastic substrate such as acrylic resin, polycarbonate resin, or polyolefin resin. A recording medium formed by the above is known. Such an air sandwich structure in which a spacer is sandwiched between two recording media and the recording layers are bonded so as to face each other, or a laminated structure in which two recording media are bonded so as to face each other Optical recording media have been proposed. Generally, an optical recording medium is of a donut type having a hole for engaging with a rotation axis at the center of a substrate molded by an injection molding method, and recording and reproducing are performed while rotating around the rotation axis. However, in recent years, its rotational speed has been 1800 rpm.
In, the warp angle of the board is 6mR (milliradian)
Since then, it has become required to further reduce the size to about 3 mR.

(Problems to be Solved by the Invention) In general, a plastic substrate is more easily deformed than a glass substrate, and thus has a large warp angle. As the warp angle increases, the shape of the beam spot emitted from the laser beam head of the recording / reproducing apparatus changes.
A displacement of the beam spot with respect to the substrate group occurs. Tracking failure occurs. Inconvenience such as occurs.

An object of the present invention is to provide a method of manufacturing an optical recording medium using a plastic substrate having a very small warp angle of a bonded substrate during recording and reproduction.

(Means for Solving the Problem) The above object of the present invention is to provide a recording layer on at least one of the facing surfaces of two facing substrates, and the facing surfaces may be directly or with air between the facing surfaces. In an optical recording medium in which a layer is formed by bonding with an adhesive via a spacer or the like, a pair of upper and lower holders used for the bonding have a recess in the circumferential direction along the outer circumference of the substrate. It is characterized in that the optical recording medium bonded to the holding member is sandwiched and pressed.

(Operation) Generally, the disk substrate 1 for an optical recording medium, which is made of an acrylic resin, a polycarbonate resin, a polyolefin resin, or the like, is mass-produced by the injection molding method. For example, when molding a polycarbonate substrate with a groove surface 12 (group) having a diameter of 130 mmΦ, an inner diameter of 15 mmΦ, and a thickness of 1.2 mm, attach a stamper (group transfer nickel plate) to the moving mold side and use the fixed mold side as a mirror surface. Injection molding a polycarbonate resin. Injection-molded disk substrate 1
As shown in FIG. 1, a vertical beam 2 (height 20-200 μm) is formed on the outermost peripheral portion of the flat surface 13 of the substrate 1 as shown in FIG.
Was found to have occurred.

Conventionally, the recording layer 3 is provided on the group surface of the substrate 1 as shown in FIG. 2, and a hot melt adhesive is applied onto the recording layer 3 by using a roll coater. The substrates were stuck together, sandwiched from the top and bottom by holders 5, 5 ', and pressed using a press 6. In the case of FIG. 2, the vertical beam 2 does not apply uniform pressure to the entire surface of the substrate 1, and the warp angle of the bonded disks (the disk is inclined with respect to the reference plane) is reduced. I couldn't.

According to the present invention, as shown in FIG. 3, a pair of upper and lower holders for bonding 5 and 5'include a recess 7 in the circumferential direction along the outer peripheral edge of the substrate 1, and the outermost flat surface of the substrate is flat. Since the vertical beam 8 generated at 1 fits into the concave portion (width 1 mm, depth 2 mm) 7, it does not come into contact with the bonding holders 5 and 5 '. Further, the lower bonding holder 5'is provided with a cylindrical convex portion 9 into which the center hole of the disk substrate fits, and the upper bonding holder 5 is provided with a cylindrical convex portion 9 '.
There is a cylindrical hole 10 that fits in. As a result, the centering and positioning of the disks can be performed during the bonding. As another form, as shown in FIG. 4, a protrusion may be provided on the outer peripheral end of the lower holder 5'and the centering ring 15 may be fitted in the center hole of the substrate.

As shown in FIG. 3, when the bonding holder of the present invention is used for pressing, nonuniform pressure on the substrate surface due to vertical burrs on the outer peripheral flat surface of the substrate does not occur.
It is possible to obtain a bonded disc having a very small warp angle.

(Example) Example 1 Diameter 130 mmΦ made of polycarbonate resin, inner diameter 15 m
A doughnut-shaped disk substrate with a tracking groove (group) of mΦ and a thickness of 1.2 mm was molded by injection molding.
The substrate 1 had vertical burrs 8 having a height of 20 to 200 μm at the outermost peripheral edge of the flat surface.

The group surface of the substrate 1 was formed by a magnetron sputtering method using a SiO ₂ layer 1000Å, Si ₃ N ₄ layer 800Å, Gd, Tb, Fe, C
A magneto-optical recording layer 11 was provided by sequentially laminating a magnetic recording layer 1000 Å and a Si ₃ N ₄ layer 800 Å. Ultraviolet (UV) curable resin (SD-17, Dainippon Ink) is spin-coated on the recording layer 3 to a film thickness of 20 μm, and UV irradiation is performed to completely cure the resin.
11 Next, using a roll coater on the protective layer 11, a hot melt adhesive (3S49, Diabond Industry Co., Ltd.)
Is applied at 140 ° C to a film thickness of 30 μm, and the adhesive layer 4
And This was used as a bonding sample of the present invention.

The lower holder 5'for bonding according to the present invention shown in FIG.
2 pieces of the above samples are fitted to each other so that the adhesive layers 4 face each other, the upper bonding holder 5 is fitted from the above, and the sample is sandwiched between the press machines 6 and pressed at 50 kg / cm ² for 10 seconds, and the both surfaces The work of attaching the magneto-optical disk for recording was completed. Similarly, create 6 sets of bonded discs,
The warp angle at which the disc was inclined with respect to the reference plane was measured. The results are shown in Table 1. The maximum value of the warp angle was defined as the warp angle of each sample. The average value of 6 samples was 1.95 mR (milliradian), which was extremely small.

Comparative Example 1 The same laminating sample as that used in Example 1 is shown in FIG. Using a conventional holder for bonding, the same operation as in Example 1 was performed to prepare 6 bonded disks, and the warp angle was evaluated in the same manner. The average value of 6 samples is 3.
At 12 mR, it was 1.5 times larger than in Example 1.

(Effect of the Invention) According to the method for manufacturing an optical recording medium of the present invention, the pair of upper and lower holders used for bonding have concave portions in the circumferential direction along the outer peripheral edge of the disk substrate. It is possible to efficiently manufacture bonded plastic discs that have a very small warp angle even if there is vertical burrs on the outer peripheral edge of the flat surface of the plastic or disc substrate molded by the method, and the shape of the beam spot during recording and reproduction does not change In addition, there is an effect that an excellent optical recording medium can be obtained in which the beam spot is not displaced with respect to the substrate group and tracking failure does not occur.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an optical disk substrate injection-molded using a polycarbonate resin. FIG. 2 is a sectional view of a pressing structure by a press when using a conventional bonding holder. FIG. 3 is a sectional view of a pressing structure by a press when the bonding holder of the present invention is used. FIG. 4 is a schematic cross-sectional view of a bonding holder showing another embodiment of the present invention. (Explanation of symbols) 1. Disc substrate 2 .. Vertical beam of substrate 3. Recording layer 4. Adhesive layer 5, 5 '. ...... Holders for bonding upper and lower parts 6,6 '. …… Press machine (press surface) 7. …… Groove of the holder for bonding 8. …… Vertical beam of the substrate 9. …… Cylindrical convex portion 10. …… Cylindric hole 11. …… Protective layer 12. …… Group side of the board 13. …… Flat surface of the board 14. …… Center hole of the board 15. …… Centering ring

Claims (1)

(57) [Claims] 1. A recording layer is provided on at least one opposing surface of two opposing substrates, and a spacer or the like is provided so that both opposing surfaces form an air layer directly or between the opposing surfaces. In a method of manufacturing an optical recording medium that is bonded with an adhesive, a pair of holders for pressing the optical recording medium up and down, which are used for bonding the optical recording medium, are attached to the substrate. A method for manufacturing an optical recording medium, characterized in that an arbitrary groove is provided in a circumferential direction along an outer peripheral surface, and the substrate is sandwiched between the holders and pressed to bond them together.