JPH09270150A - Optical disk and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an excellent characteristic even in either recording area and to make possible easily revising specification also by sticking two substrates forming a recording layer each other and changing a signal recording area each other. SOLUTION: A first substrate 2 forming the recording layer 1 and a second substrate 4 forming the recording layer 3 are stuck each other opposing the sides forming the recording layers 1, 3 each other. Signal recording areas 6, 8 are formed on the first substrate 2 and the second substrate 4 respectively. Then, the signal recording areas 6, 8 are different from each other in the first substrate 2 and the second substrate 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk, for example, a so-called partial RO having a read-only recording area and a user writable recording area.
It relates to an optical disc suitable as M.

[0002]

2. Description of the Related Art A so-called partial ROM having both a read-only recording area (ROM) and a user writable recording area (RAM) is used, for example, as a software supply medium for a game machine.

In this partial ROM, the RA on the substrate is
A guide groove, an address code pit, or the like is formed in an area corresponding to M as an uneven shape, and a writable recording layer made of a phase change material or the like is formed on the uneven shape. Further, in the area corresponding to the ROM, data pits corresponding to the data signal are formed in an uneven shape together with the address code pits, and a reflective layer of Al or the like is formed on the uneven shape. A protective layer made of an ultraviolet curable resin or the like is provided on the recording layers of the RAM and the ROM to protect the recording layers from moisture and impact of the external environment.

A substrate having such a RAM area and a ROM area is usually formed by an injection molding method using a stamper on which a concavo-convex pattern of the substrate is formed.

[0005]

However, in such a partial ROM, since the ROM area and the RAM area are formed on the same substrate, the pit forming condition and the recording layer forming condition are designed by a trade-off between them. I have no choice but to
It is difficult to optimize these conditions in each recording area. Therefore, in any recording area, a sacrificial portion comes out, which is inevitable compared to an optical disk dedicated to ROM or RAM. The characteristics are inferior.

Further, for example, in a software supply medium for a game machine, data information is changed in the ROM area according to the type of software, but the RAM area has the same uneven pattern regardless of the type of software. When used as such a medium, in the configuration in which the ROM area and the RAM area are formed on the same substrate, the RAM area may be included every time the ROM area is changed, although the RAM area may have the same concavo-convex pattern. It has a drawback that it requires a stamper and is not suitable for changing specifications.

Therefore, the present invention has been proposed in view of such a conventional situation, and two recording areas can be formed under optimum conditions, respectively, and good characteristics can be obtained in any recording area. It is an object of the present invention to provide an optical disc which can be obtained and whose specifications can be easily changed, and a manufacturing method thereof.

[0008]

In order to achieve the above object, the optical disc of the present invention comprises a first substrate having a recording layer formed thereon and a second substrate having a recording layer formed thereon. It is characterized in that the first substrate and the second substrate are different in signal recording area from each other and are bonded to each other with their recording layer-formed sides facing each other.

Further, in the method for manufacturing an optical disc of the present invention, the first substrate and the second substrate formed in regions where the recording layers are different from each other are made to face each other on the side where the recording layers are formed,
It is characterized in that the above-mentioned ultraviolet-curing resin is cured by irradiating with ultraviolet rays from the first substrate side and the second substrate side after bonding with the ultraviolet-curing resin.

An optical disc constructed by bonding a first substrate having a recording layer formed thereon and a second substrate having a recording layer formed thereon, that is, an optical disc having two recording layers provided on separate substrates. In the disc, pits and films can be formed under optimum conditions in each recording layer.

In such an optical disc, the first
By changing the combination of the second board and the second board, the information of the first board and the second board can be generated without causing a new stamper.
It is possible to freely combine the information of the substrates. Therefore, it is very easy to change the specifications.

Further, in such an optical disc, since the recording layers are formed in the regions different from each other on the first substrate and the second substrate, for example, when an ultraviolet curable resin is used for bonding the substrates to each other. By irradiating ultraviolet rays from both sides of the disk, it is possible to irradiate the ultraviolet curable resin with ultraviolet rays without passing through the recording layer. Therefore, a sufficient amount of light can be applied to the ultraviolet curable resin, and the resin can be cured in a short time.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

It should be noted that the present invention is based on the partial ROM.
An example applied to is explained.

As shown in FIGS. 1 and 2, the optical disc according to this embodiment has a disc-shaped first substrate 2 and a second substrate 4 formed in regions where recording layers 1 and 3 are different from each other. However, the side where the recording layers 1 and 3 are formed is made to face each other, and is bonded by the ultraviolet curable resin 5.

The first substrate 2 is a ROM substrate on which a read-only recording layer is formed. This first substrate 2
A ROM area 6 is set in an annular shape on the inner peripheral side of the.
As shown in FIG. 2, in the ROM area 6, data pits 7 corresponding to address information and data information such as address code pits are engraved as an uneven shape.

The material of this substrate may be any substrate material normally used for optical discs. In addition to plastic materials such as acrylic resin, polycarbonate resin, polyolefin resin and epoxy resin, glass is also used. To be done. The thickness of the substrate is set to about 0.6 mm in consideration of compatibility with a digital audio disc (so-called compact disc).

On the ROM area 6 of the first substrate 2,
A metal reflective layer made of Al, Au, or the like is formed as the recording layer 1.

On the other hand, the second substrate 4 is a substrate for RAM in which a recording layer writable by the user is formed. An annular RAM area 8 is set on the outer peripheral side of the second substrate 4. In this RAM area 8, address information such as guide grooves and address code pits is engraved as an uneven shape. As the material of the second substrate 4, any of the materials exemplified for the first substrate 2 can be used.

On the RAM area 8 of the second substrate 4,
Recording layer 3 on which data information can be written by the user
Is formed. The recording layer 3 may be a write-once recording layer capable of writing only once or a rewritable recording layer capable of writing / erasing. Specifically, a perpendicular magnetization film having a magneto-optical characteristic (Kerr effect or Faraday effect), a low melting point metal thin film, a phase change film, a film containing an organic dye, and the like are formed.

In addition to these recording layers, the RAM area 8 is provided with a dielectric layer or a reflective layer for the purpose of increasing the reflectance or the degree of signal modulation and protecting the recording layer. You may make it form the recording part of a multilayer structure which consists of a dielectric layer, a recording layer, a 2nd dielectric layer, and a reflective layer.

As the dielectric layer, an oxide, a nitride or the like can be used. For example, a thin film made of silicon nitride or aluminum nitride, or a ZnS-SiO ₂ mixed film is used.

The reflective layer is preferably composed of a film having a high reflectance that reflects 70% or more of the laser light at the boundary with the second dielectric layer 7, and is a metal reflective layer made of Al, Au, or the like. Is preferred.

The first recording layers 1 and 3 are thus formed
The substrate 2 and the second substrate 4 are bonded to each other with the ultraviolet curable resin 5 so that the sides on which the recording layers 1 and 3 are formed face each other.

The ultraviolet curable resin 5 bonds the first substrate 2 and the second substrate 4 to each other, and the recording layers 1 and 3 formed on the first substrate 2 and the second substrate 4 are externally bonded to each other. It also serves as a protective layer that shields moisture from the environment. Therefore, as the ultraviolet curable resin 5, an acrylic ultraviolet curable resin having excellent waterproof property is suitable.

In the optical disc having such a structure, RO
Since the M area 6 and the RAM area 8 are formed on separate substrates 2 and 4, when forming the ROM area 6,
The pits and the recording layer can be formed on the substrate under the optimum conditions suitable for the pit pattern in the OM and the structure of the recording layer. Further, also in the RAM area 8, the pits and the recording layer can be formed on the substrate under the optimum conditions suitable for the pit pattern in the RAM and the configuration of the recording layer. Therefore,
As compared with a disk having a ROM area and a RAM area on the same substrate, good characteristics can be obtained in both the ROM area and the RAM area.

In addition, if the ROM area 6 and the RAM area 8 are formed on separate substrates 2 and 4, the RO area is changed according to the type of software, such as the software supply medium of a game machine.
When only the data information of the M area is changed and the concavo-convex pattern of the RAM area is made the same, only the data information of the stamper for ROM may be changed and the stamper for RAM combined with this may be always the same. Therefore, there is an advantage that the specifications can be easily changed.

This optical disc is manufactured as follows.

First, the first substrate 2 for ROM and the RAM
A second substrate 4 for each is produced.

When a plastic material is used as the material of the substrate, the substrate is manufactured by an injection molding method using a stamper on which a concavo-convex pattern of the substrate is formed. When a glass substrate is used as the substrate, glass 2P (Photo Polymerizatio) is used.
An uneven pattern made of resin is formed on this substrate by the n) method.

In the first substrate 2, data pits corresponding to address information and data information such as address code pits are formed as a concavo-convex pattern in the annular ROM area 6 set on the inner peripheral side.

On the other hand, on the second substrate 4, address information such as guide grooves and address code pits is formed as a concavo-convex pattern in the annular RAM area 8 set on the outer peripheral side.

At this time, the ROM area 6 and the RAM area 8 do not overlap in the entire area when the substrates 2 and 4 are bonded to each other, or if they overlap each other, only a part thereof overlaps. It is desirable to set each as a signal recording area. The ROM area and the RAM area are overlapped because if a gap is formed between the recording layer of the ROM and the recording layer of the RAM, the gap becomes a non-reflecting portion and causes defocusing. When the recording layer of the ROM and the recording layer of the RAM are made to partially overlap with each other, such a non-reflecting portion does not occur, and defocusing is avoided.

The inner area of the ROM area 6 and the RAM area 8 is preferably formed within a range of 1 mm or more from the center of the disk in consideration of the eccentricity of the disk and an error in masking the film formation. . Normally, the eccentricity of the disk is about ± 100 μm, and the error of the film masking is ± 50.
It is about 0 μm.

Then, the ROM area 6 of the first substrate 2 and the RAM area 8 of the second substrate 4 thus manufactured.
Recording layers 1 and 3 are formed on the respective layers.

In the ROM area 6 of the first substrate 2, a metal reflective layer made of Al, Au or the like is formed as the recording layer 1.
A so-called vapor-phase plating technique such as vapor deposition or sputtering is used as the film forming method.

On the RAM area 8 of the second substrate,
In addition to the recording layer 3, a dielectric layer, a reflective layer, etc. are formed if necessary.

The film forming method for each of these layers is appropriately selected depending on the material used, but the recording layer such as the perpendicular magnetization film, the low melting point metal thin film, the phase change film, the film containing the organic dye, etc., and the dielectric layer may be selected. The body layer and the reflective layer are formed by a so-called vapor phase plating technique such as vapor deposition or sputtering.

Then, either the first substrate 2 or the second substrate 4 on which the recording layers 1 and 3 are formed, or the surface on which both recording layers are formed, is spin-coated with an ultraviolet curable resin. And the like, and the substrates 2 and 4 are attached to each other. Then, the ultraviolet curable resin is irradiated with ultraviolet rays by an ultraviolet lamp.

At this time, it is desirable to irradiate the ultraviolet rays from both the first substrate 2 side and the second substrate 4 side. When ultraviolet rays are irradiated from either one of the substrates, the ultraviolet curable resin is irradiated with the ultraviolet rays through the recording layer in the region on the irradiation side where the recording layer of the substrate is formed. At this time, since the ultraviolet rays are partially reflected and absorbed by the recording layer, the amount of light actually applied to the ultraviolet curable resin becomes smaller than the amount of emitted light, and a great amount of time is required for curing the resin.

On the other hand, when ultraviolet rays are radiated from both the substrate sides 2 and 4, the regions of the recording layers on the respective substrates 2 and 4 are different, so that the region where the recording layer 1 of the first substrate 2 is formed. In FIG. 6, ultraviolet rays from the second substrate 4 side are irradiated to the ultraviolet curable resin 5 without passing through the recording layer, and in the region 8 of the second substrate 4 where the recording layer is formed, from the first substrate 2 side. Of ultraviolet rays is applied to the ultraviolet curable resin 5 without passing through the recording layer. Here, since the absorption of ultraviolet rays by the substrate is extremely small, it is possible to irradiate the ultraviolet curable resin with a sufficient amount of ultraviolet rays over the entire area of the disk, and the curing time is shortened.

By the way, the transmittance of ultraviolet rays is about 80% for the polycarbonate substrate and about 0.8% for the Al reflection layer, and in the recording portion having a four-layer structure including the Ge ₂ Sb ₂ Te ₅ phase change material layer. Since it is thick, it can hardly pass ultraviolet rays.

In order to read an information signal from such an optical disk, the ROM area 6 or the RAM area 8 is irradiated with laser light with a minute spot diameter, and a change in the amount of light reflected from the disk is detected.

In this information reproduction, as shown in FIG. 3, the laser beam L is irradiated from one of the substrates, and R is emitted.
Both the OM area 6 and the RAM area 8 may be reproduced, and the ROM area 6 is reproduced by irradiating the laser light L ₁ from the first substrate 2 side as shown in FIG. The RAM area 8 may be reproduced by irradiating the laser light L ₂ from the side, and the laser light may be radiated from different sides in the respective areas. However, since only one optical pickup device is required, which is advantageous for simplification of the device, laser light is emitted from one substrate side, and the ROM area 6 and RAM are
It is desirable to regenerate both areas 8.

When the laser light is irradiated from one substrate side to reproduce both the ROM area 6 and the RAM area 8, the other substrate is irradiated with the laser light from the recording layer side. The concavo-convex pattern formed on the substrate needs to be formed in an inverted pattern when laser light is irradiated from the substrate side.

In this case, the ROM area 6 to R
Since the laser spot is continuously scanned from the AM area 8 or the RAM area 8 to the ROM area 6, the ROM area 6
If the above-mentioned non-reflective portion exists between the RAM area and the RAM area 8, defocus occurs at this portion. Therefore, as described above, it is desirable that the outer peripheral portion of the ROM area 6 and the inner peripheral portion of the RAM area 8 partially overlap. ROM area 6 and RA
When changing the irradiation side of the laser beam in the M region 8, R
The OM area 6 and the RAM area 8 may or may not overlap.

Although one form of the optical disc according to the present invention has been described above, the form of the optical disc is not limited to this.
For example, both the recording area of the first substrate and the recording area of the second substrate may be a ROM area having data pits, or both may be a RAM area. Further, when the ROM area and the RAM area are combined, the ROM area may be on the inner circumference side and the RAM area may be on the outer circumference side as in this embodiment, and conversely, the RAM area may be on the inner circumference side. ROM
The region may be on the outer peripheral side. In this case, the same effect can be obtained.

[0048]

EXAMPLES Hereinafter, specific examples of the present invention will be described based on experimental results.

Here, in order to confirm the effect of the manufacturing method of the present invention, a method of irradiating ultraviolet rays in the step of bonding the substrates was examined.

Example 1 First, as a first substrate for ROM, a diameter of 120 mm,
A polycarbonate substrate having a thickness of 0.6 mm was produced by an injection molding method. In this first substrate, a ROM area is set in a range of 20 mm to 40 mm from the center of the substrate, and data pits corresponding to data information are formed in this area. Then, in the ROM area of this substrate, an Al reflective layer having a thickness of 50 nm was formed as a recording layer by a sputtering method.

Next, as a second substrate for RAM, a polycarbonate substrate having a diameter of 120 mm and a thickness of 0.6 mm was prepared by injection molding. In the second substrate, a range of 40 mm to 58 mm from the center of the substrate is a RAM area, and this area does not overlap the ROM area of the first substrate. In addition, in this RAM area,
A guide groove is formed. Then, in the RAM area of the substrate, the first ZnS-SiO ₂ dielectric layer with a thickness of 100 nm, Ge ₂ Sb ₂ Te ₅ phase change material layer having a thickness 22 nm, the second thickness 20 nm ZnS-SiO ₂ A dielectric layer and an Al reflective layer having a thickness of 100 nm were sequentially formed by a sputtering method to form a recording portion.

Then, on the side of the first substrate on which the recording layer was formed, within a range of about 15 mm to 60 mm from the center of the disc,
UV curable resin (Product name SD-1 manufactured by Dainippon Ink and Chemicals, Inc.
7: An integrated light amount of 155 mJ / cm ² ) was applied by a spin coater, and the surface of the second substrate on which the recording layer was formed was bonded to this surface. Then, in this state, ultraviolet rays were irradiated from both sides of the disk by an ultraviolet lamp to cure the resin. At this time, the ultraviolet curable resin is
Sufficient curing could be achieved by irradiating UV rays from each side for 2 seconds for a total of 4 seconds.

Signal reproduction was performed on the optical disc manufactured in this manner. The ROM area is irradiated with laser light from the first substrate side, and the RAM area is irradiated with laser light from the second substrate. As a result, RO
Good reproduction characteristics could be obtained in any of the M region and the RAM region.

Embodiment 2 The ROM area on the first substrate is set to 20 from the center of the disk.
In the range of mm to 41 mm, the concavo-convex pattern of Example 1 is formed in this area, and the RAM area on the second substrate is 40 to 58 from the disk center.
An optical disk was produced in the same manner as in Example 1 except that the range was set to mm, that is, the ROM area and the RAM area were partially overlapped.

Also in this case, the ultraviolet curable resin between the first substrate and the second substrate can be sufficiently cured by irradiating ultraviolet rays for 2 seconds on each surface for a total of 4 seconds. did it.

Then, signal reproduction was performed on the optical disk thus manufactured. Irradiation with laser light was performed from the second substrate side in both the ROM area and the RAM area. As a result, ROM area, R
Good reproduction characteristics could be obtained in both areas of the AM area.

COMPARATIVE EXAMPLE 1 The ROM area on the first substrate is 20 from the center of the disk.
mm to 58 mm, and the RAM on the second substrate
An optical disk was produced in the same manner as in Example 1 except that the area was set to be in the range of 20 mm to 58 mm from the disk center, that is, the RAM area and the ROM area were entirely overlapped.

However, in this case, since the recording layer of the second substrate has a four-layer structure and hardly transmits ultraviolet rays, the ultraviolet curable resin was cured by irradiating ultraviolet rays from the first substrate side. At this time, irradiation time of 150 seconds was required to sufficiently cure the resin. From this, it was found that it takes a long time to cure the resin when ultraviolet rays are radiated through the recording layer.

[0059]

As is apparent from the above description, the optical disc of the present invention is constructed by laminating the first substrate having the recording layer formed thereon and the second substrate having the recording layer formed thereon. Since the first substrate and the second substrate have different signal recording areas from each other, it is possible to form the two signal recording areas under optimum conditions and obtain good characteristics in any of the signal recording areas. be able to. Also, by changing the combination of the first substrate and the second substrate, it is possible to freely combine the information of the first substrate and the information of the second substrate without causing a new stamper. Can be done easily.

Therefore, the optical disc of the present invention is suitable as a software supply medium for a game machine and can be used for various other purposes.

In such an optical disc, the first disc
Since a recording layer is formed in different regions between the first substrate and the second substrate, for example, when an ultraviolet curable resin is used for bonding the substrates together, the recording is performed by irradiating ultraviolet rays from both sides of the disc. It is possible to irradiate the ultraviolet curable resin with ultraviolet rays without going through the layer. Therefore, a sufficient amount of light can be applied to the ultraviolet curable resin, and the resin can be cured in a short time.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of an optical disc to which the present invention is applied.

FIG. 2 is a schematic cross-sectional view of an essential part showing an enlarged ROM area of the optical disc.

FIG. 3 is a schematic diagram showing an example of a method of irradiating a reproduction laser beam on an optical disc.

FIG. 4 is a schematic diagram showing another example of a method of irradiating a reproduction laser beam on an optical disc.

[Explanation of symbols]

1, 3 recording layer, 2 first substrate, 4 second substrate, 5
UV curable resin, 6 ROM area, 8 RAM area

Claims (7)

[Claims] 1. A first substrate on which a recording layer is formed and a second substrate on which the recording layer is formed are bonded together with their sides on which the recording layers are formed facing each other. An optical disc, wherein the substrate and the second substrate have different signal recording areas. 2. The optical disk according to claim 1, wherein the first substrate and the second substrate are bonded together by an ultraviolet curable resin. 3. The optical disk according to claim 1, wherein the first substrate and the second substrate have different regions in which recording layers are formed. 4. A recording layer formed on a first substrate, and a second layer.
2. The optical disc according to claim 1, wherein the recording layers formed on the substrate are partially overlapped. 5. The optical disk according to claim 4, wherein the laser beam is irradiated from one of the first substrate side and the second substrate side when reproducing the signal. 6. The recording layer formed on one substrate is a read-only recording layer, and the recording layer formed on the other substrate is a writable recording layer.
The described optical disc. 7. A first substrate and a second substrate having recording layers formed in different regions are made to face each other on the sides having recording layers formed thereon, and are bonded together by an ultraviolet curable resin. A method for manufacturing an optical disk, characterized in that the ultraviolet curable resin is cured by irradiating ultraviolet rays from the substrate side and the second substrate side.