JP2005190602A - Manufacturing method of optical disc - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the manufacturing method of an optical disk having a specification satisfying CD and DVD standards by preventing white turbidity when the optical disk is manufactured using plastics mainly composed of polylactic acid for a substrate. <P>SOLUTION: In the manufacturing method of the optical disk 9 wherein a reflection layer 7 or a recording layer is layered on the rugged pit of a light transmissive substrate 5 made of plastics mainly composed of polylactic acid and reproduction of information of the rugged pit or recording and reproduction of the recording layer is performed by irradiation with a laser beam from the light transmissive substrate 5 side, the reflection layer 7 or the recording layer is formed by a sputtering method at a prescribed sputtering rate, in a prescribed time and at a temperature so as to be not higher than crystallization temperature of the plastics mainly composed of polylacticc acid. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method of manufacturing an optical disk using a plastic whose main component is polylactic acid for a substrate.

As a material for an optical disk substrate, polycarbonate resin is mainly used because light transmittance, workability, productivity, and the like are required.
In fact, the CD (compact disk) is 98% or more by weight, and the DVD (digital versatile disk) is 95% or more polycarbonate resin.
When this CD or DVD is burned and discarded, carbon dioxide gas is generated, which affects global warming. Moreover, since the above-mentioned resin is a depleting fossil resource, it leads to waste of resources.

As a countermeasure, polylactic acid made from starch such as corn is attracting attention because it is biodegradable, is a renewable resource, and is an environmentally low-load resin.
In Patent Document 1, an IC card has an IC chip and an antenna formed on a first card substrate made of paper, and a second card substrate is disposed opposite to the first substrate and bonded via an adhesive made of polylactic acid. It is described that even if discarded after use, it is completely decomposed over time and can be naturally reduced.

Utility Model Registration No. 3075400

However, when a CD or DVD is manufactured using a substrate made of a plastic mainly composed of polylactic acid, there is a problem that the reflectance of the laser beam when recording / reproducing information does not satisfy those standards. It was.
When such a substrate surface was observed, white turbidity was observed, and when this white turbid portion was analyzed by X-ray diffraction, it was found that polylactic acid was crystallized. This is presumably because the substrate is heated to a temperature equal to or higher than the crystallization temperature of the plastic mainly composed of polylactic acid when the reflective layer and the recording layer are formed by sputtering.

  Therefore, the present invention has been made to solve the above-described problems. When an optical disk is produced using a plastic mainly composed of polylactic acid as a substrate, white turbidity is prevented and a CD or DVD is produced. An object of the present invention is to provide a method of manufacturing an optical disc having a specification satisfying the standard.

According to a first aspect of the present invention, a reflective layer or a recording layer is laminated on a concavo-convex pit of a light transmissive substrate made of a plastic mainly composed of polylactic acid, and laser light is irradiated from the light transmissive substrate side. In the method of manufacturing an optical disk for reproducing the information on the uneven pits, or recording / reproducing the recording layer,
The reflective layer or the recording layer is formed by a sputtering method at a predetermined sputtering rate and a predetermined sputtering time so as to be equal to or lower than a crystallization temperature of the plastic mainly composed of polylactic acid. A manufacturing method is provided.
2. The optical disk manufacturing method according to claim 1, wherein the predetermined sputtering rate is 5 to 40 nm / second, and the predetermined sputtering time is 0.3 to 30 seconds. provide.

  According to the present invention, the reflective layer or the recording layer is formed by a sputtering method at a predetermined sputtering rate and a predetermined sputtering time so as to be equal to or lower than the crystallization temperature of the plastic mainly composed of polylactic acid. It can prevent cloudiness. For this reason, an optical disc that satisfies the specifications defined in the CD and DVD standards can be obtained.

An optical disk manufacturing method according to an embodiment of the present invention will be described with reference to FIG.
1A and 1B show a method of manufacturing an optical disk according to an embodiment of the present invention, in which FIG. 1A is a cross-sectional view of a sputtering apparatus, and FIG. 1B is a cross-sectional view of a manufactured optical disk.

First, a sputtering apparatus will be described with reference to FIG.
As shown in FIG. 1A, the sputtering apparatus 1 includes a vacuum chamber 2 having an inert gas inlet 2a and an outlet 2b, and a mechanism for circulating cooling water installed in the vacuum chamber 2. The substrate holder 3 and the target holder 4 opposed to the substrate holder 3 at a predetermined distance are roughly configured.

Next, an optical disk manufacturing method according to an embodiment of the present invention will be described.
A light-transmitting substrate 5 made of plastic mainly composed of polylactic acid is placed on a substrate holder 3 in a vacuum chamber 2 of the sputtering apparatus 1, and a target 6 is fixed to the side of the target holder 4 facing the substrate holder 3. To do.
The light transmissive substrate 5 is manufactured by injection molding by optimizing the resin temperature, mold temperature, and the like using a stamper in which minute concave and convex pits and grooves are formed. Here, the thickness of the light transmissive substrate 5 is 1.2 mm.

Next, an inert gas such as Ar is introduced from the gas inlet 2a of the vacuum chamber 2 and discharged from the gas outlet 2a, and then the target 6 is DC sputtered (DC sputtered) to form a light transmissive substrate. A reflective layer 7 is formed on 5.
At this time, since the plastic containing polylactic acid as a main component becomes cloudy at a temperature higher than the crystallization temperature, it is necessary to control the sputtering time and the sputtering rate so as not to exceed it.

  The plastic based on polylactic acid used here is preferably synthesized from a monomer based on L-lactic acid and / or D-lactic acid. For example, “Mitsui Chemicals” Desirable materials include “Lacia H100, H100J”, “Nature Works” manufactured by Cargill Dow, “Terramac TE-4000” manufactured by Unitika Ltd., and the like. Other than these, copolymerized polylactic acid copolymerized with other monomer components having ester forming ability, and alloy resin mainly composed of polylactic acid obtained by mixing polylactic acid and other transparent plastics may be used.

  Next, as shown in FIG. 1B, after the light transmissive substrate 5 on which the reflective layer 7 is formed is taken out from the sputtering apparatus 1 and an ultraviolet curable resin is applied on the reflective layer 7 by spin coating. Then, the protective layer 8 is formed by curing to produce the optical disk 9.

Next, the optical disk 9 was produced under the following conditions, and the reflectance of the reflective layer 7 formed by the sputtering method was examined.
The optical disk 9 was produced as follows.
As the light-transmitting substrate 5, using a polylactic acid resin pellet (manufactured by Mitsui Chemical Co., Ltd., Lacia H100) and an injection molding machine (Nissei Resin Co., Ltd., M040E), a cylinder temperature of 230 ° C and a mold temperature of 50 ° C Under these conditions, a concavo-convex pit conforming to the CD standard was injection-molded, and a light transmittance of 91% with respect to a laser beam having a wavelength of 780 nm was obtained. This is almost equivalent to polycarbonate material.

As the sputtering apparatus 1, CD COATER 600 manufactured by Shibaura Seisakusho was used. The reflective layer 7 is formed to have a thickness of 50 to 150 nm using Al as a target, with a sputtering rate of 5 to 40 nm / second and a sputtering time of 3 to 30 seconds. As described above, the low sputtering rate and the short sputtering time are performed because when the plastic material mainly composed of polylactic acid is used for the light-transmitting substrate 5, the crystallization temperature is lower than that of polycarbonate. This is to prevent the occurrence of white turbidity.
The protective film 8 was formed to a thickness of 25 μm by forming an ultraviolet curable resin (urethane acrylate ultraviolet curable resin, SD662, manufactured by Dainippon Ink Co., Ltd.) by spin coating at 1500 rpm and irradiating with ultraviolet rays to cure. Is.
The results are shown in Table 1.

  In Table 1, in Examples 1 to 5, Al target is commonly used as the target 6, the sputter rate is common as 20 nm / second, and only the sputter time is different. Further, Comparative Examples 1 to 3 differ from Examples 1 to 5 in that the sputtering time is longer than those of Examples 1 to 5. The reflectance is obtained by the ratio of the reflected light that is incident on the laser beam from the protective film 8 side and is reflected by the reflective layer 7 and extracted from the protective film 8 with respect to the incident laser light.

Under any of the above conditions, white turbidity did not occur in the light-transmitting substrate 5.
Further, as shown in Examples 1 to 5 in Table 1, when the reflectance was measured by irradiating a laser beam of 780 nm from the protective film 8 side, all were 70%. This indicates that the reflective layer 7 satisfies the CD standard that requires a reflectance of 70% or more. When the optical disk 9 produced under these conditions was reproduced with a commercially available CD player, good reproduction could be performed in the same manner as when polycarbonate was used for the light-transmitting substrate.

  On the other hand, in Comparative Examples 1-3, as shown in Table 1, it was 62.3-66.4% with respect to 780 nm laser light. Under any of the above conditions, the light-transmitting substrate 5 is clouded, and the reflective layer 7 does not satisfy the CD standard which requires that the reflectance be 70% or more. When the optical disk 8 produced under these conditions was reproduced with a commercially available CD player, reproduction was impossible.

As described above, according to the embodiment of the present invention, the light transmissive substrate 5 is made of plastic containing polylactic acid as a main component, and the reflective layer 7 is sputtered to crystallize the plastic containing polylactic acid as a main component. Since it is formed with a sputtering rate of 5 to 40 nm / second and a sputtering time of 0.3 to 30 seconds so as to be as follows, it is possible to prevent white turbidity of the light-transmitting substrate 5 and to satisfy the CD standard. Can be obtained.
Note that the same effect can be obtained by using a recording layer instead of the reflective layer 7 described above. In the case of DVD, the same effect can be obtained.

  Since polylactic acid has biodegradability and is a renewable resource, it can be applied to optical discs conforming to the CD standard and DVD standard by improving heat resistance.

1A and 1B show a method for manufacturing an optical disc according to an embodiment of the present invention, in which FIG. 1A is a cross-sectional view of a sputtering apparatus, and FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Sputtering device, 2 ... Vacuum chamber, 2a ... Gas introduction port, 2b ... Gas discharge port, 3 ... Substrate holder, 4 ... Target holder, 5 ... Light transmission substrate, 6 ... Target, 7 ... Reflective layer, 8 ... Protective layer, 9 ... optical disc

Claims (2)

A reflective layer or a recording layer is laminated on the concavo-convex pits of a light-transmitting substrate made of a plastic mainly composed of polylactic acid, and information on the concavo-convex pits is reproduced by irradiating laser light from the light-transmitting substrate side, or In the method of manufacturing an optical disc for recording / reproducing the recording layer,
The reflective layer or the recording layer is formed by a sputtering method at a predetermined sputtering rate and a predetermined sputtering time so as to be equal to or lower than a crystallization temperature of the plastic mainly composed of polylactic acid. Production method. 2. The method of manufacturing an optical disk according to claim 1, wherein the predetermined sputtering rate is 5 to 40 nm / second, and the predetermined sputtering time is 0.3 to 30 seconds.

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