JPH11120632A - Production of phase transition type optical disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical disk having excellent durability and recording and reproducing characteristics in a high temp. and high humidity environment by applying a cationic polymn. adhesive and irradiating with UV rays of prescribed illuminance after an initialization process, then laminating disks with thin film sides inside, and pressurizing to adhere. SOLUTION: A first dielectric layer 2 having 100 nm thickness, a recording layer 3 having 25 nm thickness, a second dielectric layer having 20 nm thickness, and a reflection layer 5 having 100 nm thickness are successively formed by sputtering on a substrate 1 having 0.6 mm thickness, and a UV-curing resin layer 6 is formed thereon to obtain a phase transition type optical disk 10. Then the recording layer 3 is initialized by irradiating with laser beams 7 from an initializing device 70 through the substrate 1. Then a cationic polymn. UV- curing adhesive layer 8 is applied by screen printing on the resin layer 6 and irradiated with UV rays to start hardening. Then, two optical disks thus prepared are laminated and pressed as shown in the figure. Thus, an optical disk with little jitters can be obtd. at a low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a phase change optical disk which requires a bonding step and an initialization step.

[0002]

2. Description of the Related Art Optical information recording media have attracted attention because of their high density and large capacity, and have been used in various applications. For example, a read-only optical disk includes a compact disk and a CD-ROM dedicated to data reproduction, and is widely used in the music field, computer field, game field, and the like. In addition, write-once optical discs that can be recorded only once are used in document filing systems, data filing systems, and the like, particularly in fields where data security is important.

[0003] Furthermore, rewritable optical discs capable of erasing and re-recording recorded information are expected to contribute to expanding the use of optical discs, because they are capable of restoring and updating data and can be used repeatedly by rewriting. Is done. As such rewritable optical disks, magneto-optical disks and phase-change optical disks have been put to practical use, and are used for data files and the like.

In order to further increase the capacity of an optical disk, it is necessary to increase the density. In order to increase the density, it is effective to reduce the laser spot diameter. The spot diameter is proportional to the laser wavelength and inversely proportional to the numerical aperture (NA) of the objective lens. Therefore, increasing the NA is an effective means for reducing the spot diameter. However, as the NA increases, the aberration tends to increase with respect to the tilt of the disk, and the influence of the tilt angle (Tilt) of the disk increases.

This aberration depends on the thickness of the disk substrate and (NA)
^Since it is proportional to ³ , when the NA is increased, the aberration can be reduced by making the substrate thinner.
For example, in the case of a 1.2 mm substrate used in a conventional CD or the like, if the NA is set to 0.6 or more, the inclination angle of the disk is only allowed to be about 4 mrad, and considering the actual use environment or productivity, etc. Not realistic. On the other hand, for example, when a 0.6 mm substrate is used, N
It has been found that even when A is 0.6, the tilt angle of the disk can be allowed up to about 8 mrad, which is a practically usable range (see “T. Sugawaya et al.”).
al. : Jpn. J. Appl. Phys. 32 (1
993) 5402. And T. Ohta et a
l. : Jpn. J. Appl. Phys. 32 (199
3) 5214. Etc.).

As described above, in order to reduce the influence of Tilt, it is effective to reduce the thickness of the substrate.
The thickness of 0.6 mm is becoming mainstream as a high-density next-generation optical disc substrate.

[0007] In order to increase the recording capacity and increase the mechanical strength, an optical disk using such a 0.6 mm substrate is usually bonded with the recording layer surfaces of two optical disks facing each other. Used. And in the case of a laser disk or a 130 mm magneto-optical disk,
It is common to bond using a hot melt adhesive. That is, a hot-melt adhesive is applied by a roll coater, and the surfaces of the two optical disks on which the hot-melt adhesive is applied are overlapped and pressed.

[0008] However, when the optical disks are bonded using a hot melt adhesive, the obtained bonded disks are not suitable for use in a high-temperature and high-humidity environment. That is, in a high-temperature and high-humidity environment, there is a problem that the hot-melt adhesive, which is a thermoplastic adhesive, is softened and the warp angle of the disk is greatly deteriorated. In particular, digital video discs (DV
D) is required to be used in a high-temperature and high-humidity environment such as for a vehicle, and therefore, the adhesive used is also required to have high heat resistance.

The types of adhesives having high heat resistance include a cationic polymerization type ultraviolet curing adhesive, a radical polymerization type ultraviolet curing adhesive, and an acrylic pressure-sensitive adhesive sheet.
Among them, the cationic polymerization type UV curing adhesive is different from the radical polymerization type UV curing adhesive, after irradiating the adhesive applied to the surface to be bonded with ultraviolet rays to start polymerization,
Bonding can be performed by overlapping the surfaces to be bonded and pressing each other. Moreover, the cost of the cationic polymerization type ultraviolet curing adhesive is lower than that of the acrylic pressure-sensitive adhesive sheet.

As described above, the cationically polymerizable UV-curable adhesive is excellent in durability, workability, and cost in a high-temperature and high-humidity environment. It is suitable as a bonding adhesive for a certain optical disk.

On the other hand, a phase-change type optical disk is shipped after the entire surface of the recording layer is irradiated with a laser beam and crystallized by heat because the recording layer immediately after film formation is in an amorphous state.
This step is generally called an initialization step.

Regarding the relationship between the bonding step and the initialization step in the method of manufacturing a phase change optical disc, for example, Japanese Patent Laid-Open No. 7-93826 discloses that the initialization step is performed after the bonding step. It describes that it is preferable to increase the mechanical strength of the laminated disc.

[0013]

However, when a cationic polymerization type ultraviolet curing adhesive is used as the bonding adhesive, the recording / reproducing characteristics are deteriorated if the initialization step is performed after the bonding step. There is a problem.

The present invention has been made in view of such problems of the prior art. In a method of manufacturing a phase-change optical disk which requires a bonding step and an initialization step,
It is an object of the present invention to obtain a phase-change type optical disc which is excellent in durability, workability, cost, and recording / reproducing characteristics in a high-temperature and high-humidity environment.

[0015]

In order to solve the above-mentioned problems, the present invention provides a method of making a crystal-amorphous phase change reversible on one surface of a substrate according to the intensity of irradiation light. Laminating two plate-like bodies including at least one phase-change optical disc on which a thin-film layer including at least a recording layer is formed with an adhesive with the thin-film layer side of the phase-change optical disc facing inside. In a method for manufacturing a phase change optical disc, comprising a step and an initialization step of thermally crystallizing the entire recording layer of the phase change optical disc, after performing the initialization step for the phase change optical disc, A cationically polymerizable UV-curable adhesive is applied to the bonding surfaces of both plate-like bodies and irradiated with ultraviolet light of a predetermined illuminance. of To provide a method of manufacturing a phase change type optical disc and performs a bonding process by applying pressure by pressure.

That is, the present invention relates not only to the bonding between phase-change optical disks, but also to the bonding between a phase-change optical disk and a plate other than the phase-change optical disk. Prior to the bonding step using an ultraviolet curable adhesive, an initialization step of the phase change optical disk is performed. In the case of bonding between phase change optical disks, a bonding step is performed after performing an initialization step on both phase change optical disks. Examples of the plate-shaped body other than the phase-change optical disk include a transparent plate such as a glass plate and a polycarbonate plate used for a substrate of the phase-change optical disk, but an opaque plate or an optical disk other than the phase-change optical disk. And so on.

The cationically polymerizable UV-curable adhesive is an ultraviolet-curable adhesive in which the adhesive is cured by cationic polymerization. Examples of usable adhesives in the present invention include an epoxy resin as a main component and an oxidized resin. One containing an antimony composite and a curing agent is included.

The method of applying the cationic polymerization type ultraviolet curable adhesive is not particularly limited. However, since this adhesive generally has a high viscosity, it is applied by a screen printing method so that the in-plane thickness becomes uniform. It is preferable to apply.

Although there is no particular limitation on the method of initialization, a laser beam irradiation method is preferable. For example, a high-output semiconductor laser of 50 to 100 μm is applied to a rotating optical disk.
A method of irradiating with an approximately beam diameter and moving the irradiation position in the radial direction to initialize the entire surface of the optical disk can be adopted.

[0020]

Embodiments of the present invention will be described below. [Embodiment] FIG. 1 is a process chart for explaining a method of manufacturing a phase-change optical disc according to an embodiment of the present invention in the order of steps.

First, a phase change type optical disk having a layer structure shown in FIG. 1A is manufactured as follows. That is,
First, a substrate 1 having an outer diameter of 120 mm and a thickness of 0.6 mm having a center hole and emboss pits corresponding to address information.
Was formed by injection molding of polycarbonate. Next, a ZnS-
A first dielectric layer 2 made of SiO ₂ and having a thickness of 100 nm;
25-nm thick recording layer 3 made of Ge-Te-Sb, Z
A 20 nm thick second dielectric layer 4 made of nS-SiO ₂ and a 100 nm thick reflective layer 5 made of an Al alloy were sequentially formed by sputtering. Next, a resin layer 6 was laminated on the reflective layer 5 by applying and curing a UV curable resin by spin coating.

Next, as shown in FIG. 1B, an initialization step is performed by irradiating the recording layer 3 of the obtained phase change optical disk 10 with the laser beam 7 from the substrate 1 side.
Here, a device (a phase-change type optical disk initialization device of Hitachi Computer Equipment Co., Ltd.) 70 that irradiates a laser beam toward a rotating disk surface and scans the laser beam in the radial direction for each rotation of the disk is used. The linear velocity of the disk was 6.0 m / s, and the laser power was 700 mW.

Next, a cation polymerization type ultraviolet curable adhesive 8 is applied on the surface of the resin layer 6 (on the surface on the thin film layer side) of the two phase-change optical disks 10, respectively. Here, SK-7000 (containing component: epoxy resin 8) manufactured by Sony Chemical Co., Ltd. is used as the cationic polymerization type ultraviolet curable adhesive.
0%, antimony oxide composite 10-15%, curing agent 5
10%). This adhesive is a viscous liquid adhesive suitable for application by a screen printing method, and is a slow-acting photocurable adhesive.

The application of the adhesive was performed by a screen printing method using a screen plate 9 having a disk-shaped mesh portion 91 corresponding to the shape of the substrate 1 as shown in FIG. An enlarged view of the mesh portion 91 is shown in FIG. The mesh of the screen plate is formed by knitting yarns 91a having a predetermined thickness in a lattice shape, and all the adjacent yarns have a substantially equal predetermined interval (opening) 91b. Here, the number of the yarns 91a is 310 / inch,
Using a screen plate 9 having a mesh size with an opening 91b of 52 μm, the coating thickness was set to 40 μm.

Next, an integrated light amount of 800 mJ / cm ² was applied to the surface of the applied adhesive 8 using a metal halide lamp.
UV light (measured by Ushio's integrated light meter UIT150) was applied to initiate curing. Then, in this state 2
As shown in FIG. 1 (c), the two phase-change optical discs 10 are placed in a press with the adhesive 8 applied on the inside thereof and placed in a pressing device.
A surface pressure of f / cm ² was applied for 20 seconds.

By performing the bonding step as described above, a bonded disk on which the two phase-change optical disks 10 were bonded was obtained. While rotating the obtained bonded disc at a linear velocity of 6 m / s, a peak power of 11 mW and a bias power of 5 m were applied to the disc.
Laser light having a wavelength of 640 nm modulated between
By focusing and irradiating with the objective lens of A0.6,
An 8-16 modulation random signal having a window width of 34.2 ns was recorded. After that, this recorded signal is reproduced,
The ratio of the amount of jitter in the reproduced signal was measured. The jitter amount was measured using an evaluator manufactured by Pulstec Co., Ltd., with an ID portion (address portion: embossed pit portion) and a data portion (signal recording portion) located at a radius of 26.0 mm from the center.
Was performed separately. COMPARATIVE EXAMPLE 1 Two phase-change optical disks 10 manufactured in the same manner as in the above embodiment were bonded together under the same conditions using the same cationic polymerization ultraviolet curing adhesive as in the above-mentioned embodiment, and then each phase-change optical disk was used. The laser beam was irradiated from the side of the substrate 1 of the optical disk 10 under the same conditions as in the above embodiment, thereby performing an initialization step for the bonded disk. With respect to the bonded disc thus obtained, the amount of jitter was measured under the same conditions as in the above example. [Comparative Example 2] The jitter amount of a phase-change optical disc 10 manufactured in the same manner as in the above embodiment under the same conditions as in the above embodiment was initialized under the same conditions as in the above embodiment, and thereafter the bonding step was not performed. Was measured.

The results of these measurements are shown in Table 1 below.

[0028]

[Table 1]

From this result, the bonded disc (embodiment) that was bonded after initialization was compared with the optical disc that had been initialized but not bonded (Comparative Example 2), and the ID portion was compared. It can be seen that there is no increase in the jitter amount in both the data portion and the data portion, and that the recording and reproducing characteristics are good. On the other hand, the bonded disc that has been initialized after bonding (Comparative Example 1) has an ID portion and an optical disk that are initialized but not bonded (Comparative Example 2). The jitter amount increases in both the data part. In particular, the amount of jitter greatly increases in the ID section.

A possible cause of this is that when initialization is performed after bonding, an adhesive layer is present on the disk at the time of initialization. That is, the non-uniformity may have an adverse effect on the crystallization of the recording layer. Especially,
Even if the cationic polymerization type ultraviolet curable adhesive is applied by a screen printing method so as to be uniform, it is inevitable that the thickness becomes non-uniform in the plane. Therefore, by performing initialization in a state where the adhesive layer does not exist, such a problem does not occur.

[0031]

As described above, according to the present invention,
In a method for manufacturing a phase-change optical disc that requires a bonding step and an initialization step, the durability in a high-temperature, high-humidity environment,
A phase-change optical disk excellent in workability, cost, and recording / reproducing characteristics can be obtained.

[Brief description of the drawings]

FIG. 1 is a process chart for explaining a method of manufacturing a phase-change optical disc according to an embodiment of the present invention in the order of steps,
(A) shows a step of manufacturing a phase change optical disk, (b) shows an initialization step, and (c) shows a bonding step.

FIG. 2 is a schematic front view showing a screen plate used for applying an adhesive in the embodiment.

FIG. 3 is an enlarged view showing a mesh portion of the screen plate of FIG. 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 1st dielectric layer 3 Recording layer 4 2nd dielectric layer 5 Reflective layer 6 Resin layer 7 Laser beam 70 Initializer 8 Adhesive layer 9 Screen plate 91 Mesh part 91a Thread 91b Opening 10 Phase change type Optical disk (plate)

Claims (1)

[Claims] 1. A phase-change type optical disk having a thin film layer including at least a recording layer in which a phase change between a crystal and an amorphous phase is reversibly performed according to the intensity of irradiation light on one surface of a substrate. A bonding step of bonding two plate-like bodies each containing at least one of them with an adhesive with the surface on the thin film layer side of the phase change optical disk facing inward, and crystallizing the entire recording layer of the phase change optical disk by heat. A method for manufacturing a phase-change optical disc, the method comprising the steps of:
One or both of the plate-shaped bodies are coated with a cationic polymerization type UV curable adhesive and irradiated with ultraviolet light having a predetermined illuminance, and thereafter, the surface on the thin film layer side of the phase change optical disk is turned inside. A method for manufacturing a phase-change optical disk, wherein the laminating step is performed by applying pressure at a predetermined surface pressure.