JP2002100073A - Optical disc and optical disc manufacturing method - Google Patents

Abstract

(57) [Problem] With the shortening of the wavelength of a light source used for an optical disk and the increase of the NA of an objective lens, there is a possibility that several types of optical disk substrates are mixed in the market. However,
If the thickness of the substrate is different, several types of dies of the injection molding machine must be prepared and replaced each time, and there is a problem that productivity is extremely deteriorated. Kind Code: A1 A single-sided reading dual-layer optical disk having two substrates each having a thickness of 0.58 mm, which is particularly likely to appear on the market in the future, and an optical disk having a cover layer having a thickness of 0.1 mm are commonly used. Molded with a mold,
An optical disk and a method for manufacturing the optical disk are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical disk and a method for manufacturing an optical disk.

[0002]

2. Description of the Related Art In an optical disk such as a DVD, a substrate having a flat mirror surface and a surface onto which a recording pattern of a concavo-convex pattern is transferred is formed. The recording pattern is read by applying light. In this case, in consideration of productivity, the substrate is often formed by injection molding using a resin such as polycarbonate.

However, in the future, it has been considered that an optical disc reproduces a signal through a transparent cover layer having a thickness of about 0.1 mm instead of a substrate having a thickness of 0.6 mm due to a shorter reproduction wavelength and a higher NA.

In a conventional DVD, the substrate thickness is
Normal 0.60mm and 0.58m for single-sided two-layer reading
m. A 0.58 mm-thick DVD two-layer substrate is injection-molded with a mold having a mold interval (cavity interval) of 0.58 mm.
Injection molding has been performed by using a mold having a cavity thickness of 0.60 mm, or by overfilling the resin with a mold having a cavity thickness of 0.58 mm. However, an optical disc having a cover layer of 0.1 mm thickness, which is expected to appear in the future, is prepared by injection molding a substrate on which a signal having a thickness of about 1.1 mm has been transferred, and a material dissolved in a solvent having a predetermined size. It is considered that a cover layer made by a so-called casting method or the like is adhered to the surface after the mold is removed and then the solvent is evaporated and hardened, followed by making a plate. Therefore, it is expected that the thickness of the substrate changes significantly and the method of manufacturing the disk also changes significantly.

[0005] In the future, it is expected that the capacity of information recorded on an optical disc will be increased, and a single-sided, dual-layer DVD having a substrate thickness of 0.58 mm and a short wavelength, It is expected that two types of optical disks with a cover layer of 0.1 mm thick for high NA will be mainly mixed in the market. However, these two types of optical disks have significantly different thicknesses of substrates to be molded. Separate dies must be prepared and exchanged each time for molding, or another line must be provided. In such a case, there is a problem that productivity is significantly deteriorated.

[0006]

As the wavelength of a light source used for an optical disc has become shorter and the NA has increased, there has been a possibility that several types of optical discs having different substrate thicknesses may be mixed in the market.

However, if the thickness of the substrate is different, several types of injection molding dies must be prepared and replaced each time.
There is a problem that productivity is extremely deteriorated.

An object of the present invention is to provide an optical disk and a method for manufacturing an optical disk, which do not require replacement of an injection mold and improve productivity.

[0009]

In order to achieve the above object, an optical disk according to the present invention comprises a first substrate having a concave and convex pattern corresponding to information formed on a predetermined surface, and a concave and convex pattern formed on the first substrate. A reflection film formed in a pattern; a cover layer covering the reflection film; and a second substrate bonded to a surface of the first substrate different from the surface on which the concavo-convex pattern is formed. And

Further, the thickness of the first substrate is equal to the thickness of the second substrate.
Characterized by being thicker than the thickness of the substrate.

Further, the cover layer has a thickness of 0.10 mm ± 0.01 mm.

The first substrate may have a thickness of 0.56 mm to 0.57 mm.
mm, and the second substrate has a thickness of 0.53 mm.
And a thickness from the cover layer to the second substrate is set to 1.20 mm ± 0.03 mm.

In addition, in the method of manufacturing an optical disk according to the present invention, a step of forming a stamper having a concavo-convex pattern on a predetermined surface according to information, and a first substrate having a predetermined thickness by the stamper and the mold are used. Forming, forming a reflective layer on the first substrate, bonding a cover layer to the reflective layer, and bonding a second substrate to the first substrate. It is characterized by.

Also, in the method of manufacturing an optical disk, the optical disk has a first substrate having a thickness of 0.56 mm to 0.57 mm on which a concave / convex pattern according to information is formed on a predetermined surface; The reflective film formed on the concave / convex pattern of the first substrate, the cover layer covering the reflective film and having a thickness of 0.10 mm ± 0.01 mm are different from the surface of the first substrate on which the concave / convex pattern is formed. 0.53mm ~
A second substrate having a thickness of 0.54 mm, wherein the distance between the first substrate and the second substrate is 0.56 mm ± 0.01.
It is characterized by being molded using a mm mold.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. The embodiments described below are preferred specific examples of the present invention, but the scope of the present invention is not limited to these embodiments.

FIG. 1 is a sectional view of an optical disk 100 showing one embodiment of the present invention. In FIG. 1, reference numeral 10 denotes a cover layer having a thickness of 0.1 mm, reference numeral 11 denotes a reflection film, reference numeral 12 denotes a signal recording area (recorded as a concavo-convex pattern according to information on a substrate 13), and reference numeral 13 denotes a 0.56 mm thick. A molded substrate (first substrate) 14 is a dummy molded substrate (second substrate) having a thickness of 0.54 mm. The substrate 13 and the substrate 14 are bonded to the adhesive layer 1
5 are pasted together.

An uneven pattern corresponding to the information is formed on the substrate 13, and the reflective film 11 is formed along the uneven pattern. The cover layer is bonded to the reflection film 11 with an adhesive (not shown).

The optical disk 100 shown in FIG.
m, inner diameter 15mm, thickness after bonding 1.2mm ±
0.03 mm, which is the same size as optical disks such as CDs and DVDs. It should be noted that the thickness after lamination allows some errors, and if the thickness is 1.20 mm ± 0.03 mm, it does not affect the implementation of the present invention.

The thickness of the cover layer is 0.1 mm ± 0.01 mm.
Is desirable. The thickness of the substrate 13 is preferably in the range of 0.56 mm to 0.57 mm. The thickness of the substrate 14 is preferably 0.53 mm to 0.54 mm. When comparing the thickness of the substrate 13 on which the uneven pattern is formed with the thickness of the substrate 14, it is desirable that the substrate 13 be thicker than the substrate 14.

FIG. 2 shows an injection molding die 200 for producing the optical disk 100 of the present invention.

In FIG. 2, reference numeral 30 denotes a fixed mold, 31 denotes a movable mold, 32 denotes a stamper, 33 denotes a nozzle, and 34 denotes a cavity. The present invention is characterized in that an interval (cavity interval) when the movable mold 31 is joined to the fixed mold 30 is 0.56 mm. It should be noted that a slight error is allowed, and if it is 0.56 mm ± 0.01 mm, it does not affect the implementation of the present invention.

FIG. 3 shows a method of manufacturing the optical disk of FIG. 1 using the injection mold 200 of FIG.

FIG. 3A shows the injection mold 20 of FIG.
0 shows a molded substrate 13.

The substrate 13 is formed by the stamper 32 shown in FIG. This stamper 32 is created as follows.

First, a glass master is coated with a photoresist and exposed to laser light to record an information pattern corresponding to the information. By performing development processing after exposing the photoresist, irregularities corresponding to information are recorded on the glass master. A conductive film is provided on the glass master by electroless plating such as sputtering, and the stamper 32 is formed by plating using the conductive film as an electrode. As a material of the stamper 32, Ni or the like is mainly used.

Then, the stamper 32 is fixed to the fixed mold 30 of the injection molding mold 200 shown in FIG. 2, and for example, polycarbonate is injected as a substrate material from the nozzle 33, and the movable mold 31 is moved in the direction of the arrow in the drawing. , The closed space formed by the fixed mold 30 and the movable mold 31 is filled with polycarbonate.
As a result, the irregularities on the surface of the stamper 32 are transferred to the polycarbonate, and when this is taken out of the injection mold 200, the substrate 13 having a thickness of 0.56 mm shown in FIG.
Is obtained.

Next, as shown in FIG. 3B, a reflective film 11 of, for example, Al is formed on the substrate 13 of FIG. 3A.

In FIG. 3C, the reflection film 11 shown in FIG.
Separately, a transparent resin having excellent optical properties, such as polycarbonate, acrylic (PMMA), amorphous polyolefin (APO), etc., is coated with a cover layer of 0.10 mm in thickness of the optical disc 100 with an adhesive (for example, an ultraviolet curable resin). Or hot melt).

Then, as shown in FIG. 3D, the substrate 14 having a thickness of 0.54 mm separately molded by using the injection mold 200 of FIG. 2 is bonded to an adhesive (for example, an ultraviolet curable resin or hot melt). Glue using Thereby, the optical disc 100 is obtained.

The substrate 14 is prepared as follows.

The substrate 14 is formed using the injection molding die 200 of FIG. The difference from the molding of the substrate 13 is that the stamper 32 is not formed with irregularities, but a flat stamper is used. This is because the substrate 14 does not need to record information and is a dummy substrate. Then, the substrate 14 having a thickness of 0.54 mm is obtained by filling less polycarbonate than when the substrate 13 is formed. Note that the cavity spacing of the injection molding mold 200 in FIG. 2 is 0.56 mm, and the polycarbonate for the thickness of 0.54 mm is insufficiently filled. However, as described above, the substrate 13 needs to record information. Since it is a dummy substrate having no stamper, transferability of the stamper is not required, and insufficient filling is not a problem.

This is because a substrate having a thickness of about 0.02 mm is made of polycarbonate or the like, as in the case where a substrate having a thickness of 0.60 mm of a DVD is molded with a mold for a two-layer DVD substrate having a gap of 0.58 mm. Since molding can be performed by overfilling the resin, a mold having a cavity spacing of 0.56 mm can mold a substrate having a thickness of 0.58 mm in addition to a substrate having a thickness of 0.56 mm to 0.57 mm. Further, if the dummy substrate is not particular about the transferability, a slightly thin substrate having a thickness of 0.54 mm to 0.53 mm can be formed by adjusting the filling amount.

Of the substrate having a thickness that can be formed by this mold,
By bonding a substrate having a thickness of 0.58 mm with an adhesive layer having an appropriate interlayer thickness, a single-sided, double-layer readout optical disk having a thickness of 0.58 mm can be produced. Similarly, of the substrates having a thickness that can be formed by this mold, a substrate having a thickness of 0.56 mm to 0.57 mm and a dummy substrate having a thickness of 0.54 mm to 0.53 mm are bonded and cast on the surface of the recording area. By bonding a cover layer having a thickness of 0.1 mm ± 0.01 mm formed by a method or the like, a 0.1 mm-thick cover layer optical disk compatible with short wavelength and high NA can be formed.

Although the description has been made using polycarbonate, which is the same material as the substrate 14, as the material of the substrate 13,
Since a laser beam for reproducing information does not pass through the substrate 13, the substrate 13 is not made of a transparent resin such as polycarbonate, but is made of, for example, modified polyphenylene oxide (modified PP).
An opaque resin having excellent moldability and mechanical properties such as O) may be used. Also, instead of polycarbonate, acrylic (PMMA)
A transparent resin such as an amorphous polyolefin (APO) -based resin may be used.

According to the present invention, two types of optical disk substrates of different types, such as a 0.58 mm thick single-sided reading dual-layer optical disk corresponding to a red light source and a 0.1 mm cover layer optical disk corresponding to a blue light source, are used in a common mold. Can be molded. For this reason, even if these two types of optical disks are mixed in the market in the future, there is no need to exchange dies or prepare a plurality of dies or manufacturing lines, and the productivity does not deteriorate.

[0036]

As described above, according to the optical disk and the method of manufacturing the optical disk of the present invention, it is not necessary to replace the injection mold, thereby improving the productivity.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of an optical disk of the present invention.

FIG. 2 is a view showing one embodiment of a mold for injection molding of a substrate of an optical disk of the present invention.

FIG. 3 is a diagram showing an example of a method for manufacturing an optical disk of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Cover layer of 0.1 mm thickness 11 ... Reflection film 12 ... Signal recording area 13, 14 ... Substrate 15 ... Adhesive layer 30 ... Fixed side mold 31 ... Moving side mold 32 ... Stamper 33 ... Nozzle 34 ... Cavity 100 ... Optical disk 200: Injection mold

Claims (6)

[Claims] A first substrate having a concave and convex pattern corresponding to information formed on a predetermined surface; a reflective film formed on the concave and convex pattern of the first substrate; a cover layer covering the reflective film; An optical disc, comprising: a second substrate bonded to a surface of the first substrate, the surface being different from the surface on which the concavo-convex pattern is formed. 2. The optical disk according to claim 1, wherein a thickness of said first substrate is larger than a thickness of said second substrate. 3. The optical disk according to claim 1, wherein said cover layer has a thickness of 0.10 mm ± 0.01 mm. 4. The first substrate has a thickness of 0.56 mm to 0.57 mm, the second substrate has a thickness of 0.53 mm to 0.54 mm, and the second substrate has a thickness of 0.52 mm to 0.54 mm. 1.20mm ±
The optical disk according to claim 3, wherein the optical disk has a thickness of 0.03 mm. 5. A step of forming a stamper having a concavo-convex pattern according to information on a predetermined surface; a step of forming a first substrate having a predetermined thickness by using the stamper and a mold; A method for manufacturing an optical disc, comprising: a step of forming a reflective layer on a substrate; a step of bonding a cover layer to the reflective layer; and a step of bonding a second substrate to the first substrate. 6. A method for manufacturing an optical disk, wherein the optical disk has a concavo-convex pattern formed on a predetermined surface according to information.
A first substrate having a thickness of 56 mm to 0.57 mm, a reflective film formed on the uneven pattern of the first substrate, a cover layer having a thickness of 0.10 mm ± 0.01 mm covering the reflective film, A second substrate having a thickness of 0.53 mm to 0.54 mm bonded to a surface of the first substrate that is different from the surface on which the concavo-convex pattern is formed, wherein the first substrate and the second substrate Board with a spacing of 0.56mm ±
6. The method for manufacturing an optical disk according to claim 5, wherein the optical disk is molded using a 0.01 mm mold.