JPH09128810A - Optical disc and method of manufacturing the same - Google Patents

Abstract

(57) Abstract: To provide a highly reliable double-sided optical disc at low cost. SOLUTION: In an optical disc capable of being optically reproduced and recorded, a first recording layer 2, a light shielding layer 3 and a second recording layer 2 are provided on a transparent substrate 1 having a groove or pit for tracking. The recording layer 4 is laminated in this order, and the transparent flat plate 6 is adhered onto the second recording layer 4 via the adhesive layer 5 made of an ultraviolet curable resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a double-sided optical disk capable of optically recording and reproducing information.

[0002]

2. Description of the Related Art Conventionally, optical discs are single-plate type optical discs such as compact discs and mini discs having one information-recorded side, and laser discs or international standards with a disc diameter of 5.25 inches ( A double-sided optical disc having two information recording surfaces, such as a magneto-optical disc based on ISO) (hereinafter also referred to as a double-sided optical disc)
And have been put to practical use. Conventional double-sided optical discs
Two pieces each having a reflective layer or a recording layer provided on a translucent substrate on which information is recorded in advance as concave and convex pits are prepared, and the information recording surfaces are opposed to each other and bonded together via an adhesive layer. Each information recording surface is provided with a concentric or spiral information track.

An example of such a conventional double-sided optical disk is described in Japanese Patent Publication No. 04-21936.
This is shown in FIG. FIG. 2 is a diagram showing an example of a conventional double-sided optical disc. In FIG. 2, the optical disc 30 is
The two optical disks 30A and 30B are configured by bonding with an adhesive layer 36. The optical disk 30A includes a translucent substrate 31, a surface uneven layer 3 on which signal information or tracking guides are formed in a concentric or spiral shape.
2, a first intermediate protective layer 33, an information forming layer 34 including a recording layer or a light reflecting layer, and a second intermediate protective layer 35 are laminated in this order.

The optical disc 30B is constructed in the same manner as the optical disc 30A, and a surface uneven layer 42, a first intermediate protective layer 43, an information forming layer 44, and a second intermediate protective layer 45 are formed on a transparent substrate 41. Are laminated in this order. Then, the second intermediate protective layer 35 of the optical disk 30A
And the second intermediate protective layer 45 of the optical disc 30B,
It is adhered via the adhesive layer 36. Recording or reproducing of the optical disk 30A is performed by irradiating a laser beam from the substrate 31 side, and recording or reproducing of the optical disk 30B is performed by irradiating a laser beam from the substrate 41 side.

[0005]

In the above-mentioned conventional double-sided optical disk, signal information or a tracking guide is actually formed on one surface of a transparent substrate, and a first intermediate protective layer, an information forming layer and a second intermediate protective layer are formed on the signal information or tracking guide. After the intermediate protective layer and the intermediate protective layer are sequentially laminated by vacuum vapor deposition or sputter vapor deposition, they are taken out to the atmosphere and bonded to another optical disk via an adhesive layer to manufacture. In the conventional method of manufacturing an optical disk of this type, many steps are required and it is necessary to accurately align the centers of the two disks, which requires a long time for measuring the eccentricity, the manufacturing efficiency is low, and the production cost is low. It had the drawback of becoming expensive.

Further, since the information forming layer is a recording layer or a light reflecting layer composed of a metal thin film such as Al or Te, the transmittance of ultraviolet rays is extremely low, and an ultraviolet curable adhesive is used at the time of bonding. Cannot be used. For this reason, in the conventional example, the hot melt method was used to bond the epoxy type adhesive, but such a solvent type adhesive takes a long time to bond and the transparent substrate or the metal thin film is used. It often becomes difficult to select the material.

Further, when the adhesive is applied, the adhesive wraps around the read surface of the optical disk to increase the defective rate. Also,
If the solvent is not sufficiently dried, there are problems that the reflectance of the information layer is different and the disk expands, resulting in an increase in errors. The present invention has been made to solve the above problems, and an object thereof is to provide a highly reliable double-sided optical disc at low cost.

[0008]

The optical disk of the present invention comprises:
In an optical disc that can be optically reproduced and recorded, a first recording layer, a light-shielding layer, and a second recording layer are provided in this order on a translucent substrate having a groove or pit for tracking. It is an optical disc in which a light-transmissive flat plate is laminated and laminated on the second recording layer via an adhesive layer. The optical disk of the present invention is an optical disk in which, in the optical disk, the optical thickness of the transparent plate and the optical thickness of the transparent substrate are substantially equal.

Further, the method for producing an optical disc of the present invention is a method for producing an optical disc which can be optically reproduced and recorded, and is characterized in that a first substrate is formed on a transparent substrate having tracking grooves or pits. The recording layer, the light-shielding layer, and the second recording layer are formed in this order in vacuum, then taken out into the atmosphere, and then an ultraviolet curable resin is applied onto the second recording layer to form an ultraviolet curable resin. After forming a layer and adhering the translucent flat plate to the translucent substrate via the ultraviolet curable resin layer, the ultraviolet curable resin layer is irradiated with ultraviolet rays from the translucent flat plate side. It is a method of manufacturing an optical disc to be manufactured.

[0010]

1 is a diagram showing the configuration of an optical disc of the present invention. In FIG. 1, a substrate 1 is a translucent substrate that can transmit laser light for recording and reproduction, and a plastic substrate such as polycarbonate, polyolefin, acrylic, or a glass substrate is used. Pregrooves and prepits are provided on one surface of the substrate 1 in a concentric or spiral shape. The pre-grooves and pre-pits are necessary to obtain a tracking control signal for guiding the laser light spot to a predetermined position during recording and reproduction, and are formed on the substrate 1 by the 2P method (photopolymer method), or , Injection molded directly.

The substrate 1 is installed in a vacuum film forming apparatus (not shown), and the first recording layer 2, the light shielding layer 3 and the second recording layer 4 are successively formed in vacuum. As the vacuum film forming method, resistance heating type or electron beam type vacuum deposition, direct current or alternating current sputtering, reactive sputtering, ion beam sputtering, ion plating, etc. are used. The first recording layer 2 is not limited to be composed of only one layer, and may be composed of a protective layer, an optical interference layer, an antireflection layer, or the like. The first recording layer 2 is composed of a metal, a semiconductor, or an organic substance that causes an optically detectable physical change, a chemical change, or the like. Examples of the material include a phase change recording layer, a magneto-optical recording layer, and the like. Examples include organic dye recording layers.

In the light shielding layer 3, the first recording layer 2 and the second recording layer 4 are optically separated. That is, the first recording layer 2
Is provided so that the information to be recorded on the second recording layer 4 is not recorded, and the information recorded on the first recording layer 2 cannot be reproduced from the second recording layer 4 side. There is. As the light shielding layer 3, a thin film made of metal, semiconductor or the like is used. The second recording layer 4 is not limited to be composed of only one layer, and may be composed of a protective layer, an optical interference layer, an antireflection layer, or the like. The second recording layer 4 is composed of a metal, a semiconductor, or an organic substance that causes an optically detectable physical change, a chemical change, or the like. Examples of the material include a phase change recording layer, a magneto-optical recording layer, and the like. Examples include organic dye recording layers.

The substrate 1 on which the second recording layer 4 has been laminated by vacuum film formation is taken out into the atmosphere, and then an ultraviolet curable resin is applied on the second recording layer 4 to form an adhesive layer (hereinafter, ultraviolet curable resin). 5) is also formed. As this coating method, a spin coating method, a spraying method, a dipping method, a blade coating method or the like is used. A transparent flat plate 6 is adhered to the substrate 1 having the tracking groove or pit through the adhesive layer 5 (ultraviolet curable resin layer), and ultraviolet rays are irradiated from the transparent flat plate 6 side. The adhesive layer 5 is cured. The ultraviolet curable resin constituting the adhesive layer 5 is at least a prepolymer, a monofunctional acrylate monomer,
It comprises a polyfunctional acrylate monomer and the like and a photopolymerization initiator.

Next, as an embodiment of the optical disc of the present invention, a case where a phase change recording film is used as the recording layer will be described with reference to FIG. FIG. 2 is a diagram showing an embodiment of the optical disc of the present invention. 2, the basic structure is the same as that shown in FIG. 1, but the first recording layer 2 is the first dielectric layer 2
1, the first phase change recording layer 22 and the second dielectric layer 23, and the second recording layer 4 includes the third dielectric layer 24, the second phase change recording layer 25 and the fourth dielectric layer 26. Has been done. Less than,
This manufacturing method will be described. First, the track pitch
A first dielectric layer 21, a first phase-change recording layer 22 as a first recording layer 2 was formed on a 1.2 mm-thick polycarbonate substrate 1 provided with a pre-groove of 1.6 μm and a groove depth of 60 nm. The second dielectric layer 23 is formed by sputtering.

In this film formation, first, the degree of vacuum is 1 × 10 -6 To
After exhausting to below rr, ZnS-SiO2 (80: 20m
ol%) is high-frequency sputtered with Ar gas to a thickness of 1
The first dielectric layer 21 having a thickness of 05 nm is formed. And the first
Ge14Sb29Te57 is formed as the phase change recording layer 22 to a thickness of 25 nm by the direct current sputtering method, and ZnS-SiO2 (80:20 mol%) is formed as a second dielectric layer 23 thereon to a thickness of 20 nm by the high frequency sputtering method. Next, as the light shielding layer 3, Al-Zr (98: 2 at%) is formed to a thickness of 150 nm by a DC sputtering method.

Further, on the light-shielding layer 3, as the second recording layer 4, a third dielectric layer 24, a second phase change recording layer 25, and a fourth recording layer 25 are formed.
The dielectric layer 26 is formed by sputtering similarly to the first recording layer 2. In this film formation, first, ZnS-S
The third dielectric layer 24 is formed to a thickness of 20 nm by high-frequency sputtering io2 (80:20 mol%) with Ar gas. Then, as the second phase change recording layer 25, Ge14Sb29T is used.
e57 was formed to a thickness of 25 nm by a DC sputtering method, and ZnS-SiO2 (80: 2) was formed as a fourth dielectric layer 26 thereon.
0 mol%) is formed to a thickness of 105 nm by a high frequency sputtering method.

After the disk is taken out from the vacuum chamber, an ultraviolet curable resin (for example, XR5C manufactured by Sumitomo Chemical Co., Ltd.) as the adhesive layer 5 is spin-coated on the fourth dielectric layer 26, and a thickness of 1 is applied to the ultraviolet curable resin. A transparent flat plate 6 made of polycarbonate having a thickness of 0.2 mm is placed on the transparent flat plate 6 and is irradiated with ultraviolet rays from the transparent flat plate 6 side to be cured. If the optical thickness of the substrate 1 and the optical thickness of the transparent flat plate 6 are made substantially equal, the thickness of the transparent flat plate 6 has the same characteristics when recording (or reproducing) two recording layers at the same time. The recording optical head (or the reproduction optical head) can be used. Further, when recording (or reproducing) one surface by one reproducing optical head, there is an advantage that one recording optical head (or reproducing optical head) is sufficient.
Here, the optical thickness is represented by multiplying the actual mechanical dimension of the optical material by the refractive index of the optical material.

Next, the optical disc manufactured as described above was evaluated. First, while rotating the optical disk, laser light was irradiated from the substrate 1 side to initialize the first phase change recording layer 22 from an amorphous state to a crystalline state with high reflectance. At this time, since heat is conducted to the second phase change recording layer 25 through the light shielding layer 3, the second phase change recording layer 25
Are also initialized at the same time. Then, recording was performed from the substrate 1 side to the land portion between the guide grooves of the first phase change recording layer 22.

The recording conditions were a linear velocity of 3 m / s, a recording laser wavelength of 684 nm, an objective lens NA of 0.6, a mark length of 0.60 μm, a peak power of 10.0 mW, and a bias power of 2.0 mW. The C / N was measured and found to be 52 dB. The second phase change recording layer 2 which is the reverse side of the recording portion of the first phase change recording layer 22 with the optical disk reversed
Recording was performed on 5 tracks. That is, recording was performed from the transparent flat plate 6 side to the guide groove (groove portion) of the second phase change recording layer 25. When the recording mark length was changed to 0.61 μm and changed from that of the first phase change recording layer 22, the C / N was 5
2 dB and C / N similar to that of the first recording layer 2 were obtained. Also, the mark length recorded on the first recording layer 2 is 0.60 μm.
No signal was detected, and the first phase change recording layer 22 and the second phase change recording layer 23 were completely separated by the light-shielding layer 3, and good characteristics were exhibited.

[0020]

【The invention's effect】

(1) Since the first recording layer, the light-shielding layer, and the second recording layer can be sequentially laminated in a vacuum on a substrate having a tracking guide, the number of manufacturing steps is small and the manufacturing efficiency is excellent. (2) Since a UV curable adhesive can be used, the quality is high and the reliability is high. (3) Since the two recording layers use a common track, there is no eccentricity, there is no need to accurately align the centers when the two discs are bonded together, and the manufacturing efficiency is high and the production cost is low. (4) According to the optical disk of the second aspect, there is an effect that the number of recording or reproducing optical heads can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an optical disc of the present invention.

FIG. 2 is a diagram showing an embodiment of an optical disc of the present invention.

FIG. 3 is a diagram showing an example of a conventional optical disc.

[Explanation of symbols]

 1 Substrate 2 First Recording Layer 3 Light-Shielding Layer 4 Second Recording Layer 5 Adhesive Layer (Ultraviolet Curing Resin Layer) 6 Light-Transparent Flat Plate

Claims (3)

[Claims] 1. An optical disk capable of being optically reproduced and recorded, wherein a first recording layer, a light shielding layer, and a second recording layer are formed on a transparent substrate having grooves or pits for tracking. An optical disc in which a layer is laminated in this order, and a transparent flat plate is adhered onto the second recording layer via an adhesive layer. 2. The optical disk according to claim 1, wherein the optical thickness of the transparent flat plate and the optical thickness of the transparent substrate are substantially equal to each other. 3. A method of manufacturing an optical disk capable of optical reproduction and recording, comprising a first recording layer and a light-shielding layer on a translucent substrate having grooves or pits for tracking. The second recording layer and the second recording layer are formed in this order in vacuum, then taken out into the air, and then an ultraviolet curable resin is applied on the second recording layer to form an ultraviolet curable resin layer. Is adhered to the translucent substrate via the ultraviolet curable resin layer, and then the ultraviolet curable resin layer is irradiated with ultraviolet rays from the translucent flat plate side to manufacture the optical disc. Production method.