JP2001202655A - Optical disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical disk which may be reproduced by both of a player for high-density reproduction and a player for low-density reproduction. SOLUTION: The optical disk 1 is provided with a first information recording layer information A of high recording density near its light incident surface 3 and is provided with a second information recording layer B of low recording density far from the light incident surface 3. A laser beam L1 for reproducing the first information recorded on the first information recording layer information A and a second laser beam L2 (the wavelength of the first laser beam L1<the wavelength of the second laser beam L2) for reproducing the second information recorded on the second information recording layer B are made incident on the light incident surface 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-density optical disk having a laminated structure which can be reproduced by a compact disk player.

[0002]

2. Description of the Related Art Conventionally, optical discs such as compact discs (hereinafter, referred to as CDs) are widely used in view of a large amount of recorded information, ease of handling, and the like. This C
D has a so-called single-plate structure constituted by one substrate. On the other hand, as shown in FIG. 6, the substrate a1 on which the first information recording layer a is formed and the substrate b1 on which the second information recording layer b is formed are placed such that their information recording surfaces a and b face each other. Conventionally, there is an optical disc 100 having a lamination type structure in which an information recording layer is formed on two sides by laminating using a transparent adhesive 2. As shown in FIG. 1, such an optical disc 100 reads information by irradiating a reproduction laser beam from both sides of the disc. This laminated structure has less disk warpage than the single-plate structure.
It is being adopted to increase the storage capacity of high-density optical disks, for example, because the amount of recorded information can be doubled.
Note that a high-density optical disk is an optical disk that records information at a higher density than a CD by recording recording pits smaller than a CD with a smaller track pitch than a CD.

In a high-density optical disk having the above-mentioned lamination type structure (hereinafter sometimes simply referred to as a high-density optical disk), a substrate to be bonded is made thinner than a CD so that various optical aberrations caused by the thickness of the substrate are reduced. It is thought to reduce. For example, the thicknesses Da and Db of the substrates a1 and b1 shown in FIG.
It is considered that the thickness D of the disk is made to be 1.2 mm by laminating them.

[0004]

By the way, the high-density optical disk 100 having the above-mentioned laminated structure can be reproduced by a player dedicated to the high-density optical disk (hereinafter, referred to as a high-density reproducing player). Therefore, it cannot be reproduced by a CD player that is a low-density reproduction player. This is because the information recording layer is formed at the center in the thickness direction of the disk. That is, this high-density optical disk is composed of substrates a1 and b1
The first information recording layer a and the second information recording layer b are located at the center in the thickness direction of the disc, with the thicknesses Da and Db of the CD being half of the CD.
Since the optical pickup has an optical length different from that of a CD, even if an information signal for a CD is recorded on one of the information recording layers, it cannot be reproduced by a CD player. As described above, the conventional high-density optical disk having a laminated structure has a disadvantage that it cannot be reproduced by an existing CD player.

Therefore, the present invention has been made in view of the above points, and a high-density reproducing player for reproducing a high-density optical disk and a low-density optical disk (for example, CD)
It is an object of the present invention to provide an optical disk having a structure that can be reproduced by any low-density reproduction player (for example, a CD player) that reproduces an image.

[0006]

In order to solve the above-mentioned problems, the present invention provides an optical disk having the following constitutions (1) to (3). (1) In order to reproduce the first information with the wavelength of the first laser light, the first information is formed at the optical length of a first optical pickup that emits the first laser light, and the first information is The second laser beam is emitted in order to reproduce the second information with the first information recording layer on which is recorded and the wavelength of the second laser beam longer than the wavelength of the first laser beam. A second information recording layer formed at the position of the optical length of the second optical pickup and recording the second information, wherein the shortest pit length of the first information recording layer is the second pit length. An optical disc characterized by being shorter than the shortest pit length of the information recording layer. (2) In order to reproduce the first information at the wavelength of the first laser light, the first information is formed at the optical length of a first optical pickup that emits the first laser light, and The second laser beam is emitted in order to reproduce the second information with the first information recording layer on which is recorded and the wavelength of the second laser beam longer than the wavelength of the first laser beam. A second information recording layer formed at the position of the optical length of the second optical pickup and recording the second information, a first substrate on which the first information recording layer is formed, A second substrate on which a second information recording layer is formed; a first information recording layer side of the first substrate; and an opposite side of the second substrate opposite to the second information recording layer side. An adhesive layer for adhering the first information recording layer, wherein the shortest pit length of the first information recording layer is
An optical disc characterized by being shorter than the shortest pit length of the information recording layer. (3) In order to reproduce the first information at the wavelength of the first laser light, the first information is formed at the optical length of the first optical pickup that emits the first laser light, and the first information is reproduced. The second laser beam is emitted in order to reproduce the second information with the first information recording layer on which is recorded and the wavelength of the second laser beam longer than the wavelength of the first laser beam. A second information recording layer formed at the position of the optical length of the second optical pickup and on which the second information is recorded, a first substrate having flat both surfaces, and A second substrate having an information recording layer formed thereon and the second information recording layer formed on the other surface; one surface of the first substrate and the one surface of the second substrate; And an adhesive layer for adhering
The optical disk according to claim 1, wherein a shortest pit length of the first information recording layer is smaller than a shortest pit length of the second information recording layer.

[0007]

In order to provide an optical disk having a structure that can be reproduced by both a high-density reproducing player and a low-density reproducing player, a first information recording layer having a high recording density is provided by an optical pickup of the high-density reproducing player. The second information recording layer having a low recording density may be provided at a position corresponding to the optical length of an optical pickup of a low-density reproducing player (for example, a CD player). That is, the first information recording layer may be formed near the light incident surface of the optical disc, and the second information recording layer may be formed far from the light incident surface. The reflection layer provided on the first information recording layer is made of, for example, silicon (Si) so as to transmit laser light in a CD reproduction wavelength range. Note that the reflective layer provided on the second information recording layer is formed using a substance having a high light reflectance regardless of the wavelength range, such as aluminum. This makes it possible to sufficiently secure the amount of reflected light from the second information recording layer. In this way, one optical disc can be reproduced by both the high-density reproduction player and the low-density reproduction player.

As described above, when a first information recording layer having a high recording density and a second information recording layer having a low recording density corresponding to an existing optical disk such as a CD are provided in one optical disk, for example, High-density playback player with high recording density
In the information recording layer, software that can be reproduced with high resolution is recorded, and in the second information recording layer with low recording density, the same software can be recorded with low resolution. In this way, the same software recorded at a high resolution can be reproduced at a low resolution even with a low-density reproduction player, so even users who do not have a high-density reproduction player can purchase this optical disc. You can do it. When a high-density reproduction player is purchased, the same software can be reproduced at a high resolution, so that one optical disk can be used for a long time. As described above, in a disk system in which the same software is recorded at a high resolution and a low resolution, a low-density reproduction player can ensure backward compatibility.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the basic structure of an optical disk according to the present invention will be described with reference to FIG. FIG. 1 is a diagram for explaining a basic configuration of the present invention. In addition, FIG.
In order to explain the basic configuration of the present invention, the structure of an optical disk is schematically shown. As shown in the figure, the optical disc 1 of the present invention has two information recording layers in the thickness direction of the disc, and near the center of the optical disc 1 in the thickness direction,
A first information recording layer A is provided, and a second information recording layer B is provided near the surface of the optical disc 1. Also,
The surface opposite to the surface on which the second information recording layer B is provided has a first reproduction laser beam L1 for reproducing information recorded on the first information recording layer A and a second reproduction laser beam L1. A light incident surface 3 on which a second reproduction laser beam L2 for reproducing information recorded on the information recording layer B is incident.

In the first information recording layer A, pits smaller than pits formed on a CD are formed at a smaller track pitch than a CD. Since information that can be reproduced by a CD player is recorded on the second information recording layer B, pits having the same size as the CD are formed at the same track pitch as the CD. The first reproduction laser light L1 is a laser light having a wavelength range smaller than that of the second reproduction laser light L2, and the focused spot diameter is smaller than that of the second reproduction laser light L2. The second reproduction laser light is a laser light in a CD reproduction wavelength range (780 ± 10 nm).

The thickness of the optical disk 1 is about 1.2 mm (± 0.1 mm) for compatibility with a CD, and the distance db from the light incident surface 3 to the second information recording layer B is db.
Is 1.1 to 1.3 mm. The distance da from the light incident surface 3 to the first information recording layer A is 0.6 m.
m, and the distance dab between the first information recording layer A and the second information recording layer B is configured to be separated by about 0.5 to 0.7 mm. This is because the first information recording layer A is provided at the optical length of the optical pickup of the high-density reproduction player, and the second information recording layer B is provided at the optical length of the optical pickup of the CD player. Here, the position of the optical length of the optical pickup means the position of the focal length in terms of the optical length of the optical pickup.

The first information recording layer A is provided with a first reflection layer A2, and the second information recording layer B is provided with a second reflection layer B2. The first reflection layer A2
Is configured to exhibit reflectivity with respect to the first reproduction laser beam L1 and to exhibit substantially transmissivity with respect to the second reproduction laser beam L2. For example, as shown in FIG. have. Note that, in the drawing, the case where the reproduction wavelength of the first reproduction laser beam L1 is 635 nm, the second reproduction laser beam L2 is 780 nm, and the first reflection layer A2 is formed of silicon having a film thickness of about 60 nm. Is shown. As shown in the figure, the first reflection layer A2 has a reflectance of about 30% for the first reproduction laser light L1, and about 5% for the second reproduction laser light L2. It is comprised so that it may become. Further, as shown in the figure, the second reflective layer B2
It is made of a material having a high reflectance regardless of the wavelength, such as gold or aluminum. Therefore, the reflectance of the optical disc 1 with respect to the first reproduction laser beam L1 is about 30%,
Of the optical disk 1 with respect to the reproduction laser beam L2 of
It is about 0%.

Next, an embodiment of the present invention will be described.
FIG. 2 is a view showing a part of a cross-sectional structure of an optical disc according to an embodiment of the present invention. FIG. 2A shows a first embodiment,
FIG. 7B shows a second embodiment. FIG. 1 shows a sectional view of the optical disk in a radial direction. The same parts as those of the optical disc 1 are denoted by the same reference numerals, and description thereof will be omitted. The optical disc 10 shown in FIG. 1A has a first substrate A1 having the first information recording layer A formed on one surface and a second substrate A1 having the second information recording layer B formed on one surface. (Laminated structure) in which the substrate B1 is bonded to the substrate B1 with an adhesive layer 2 interposed therebetween.

The first substrate A1 and the second substrate B1
Is made of a material used in a conventional optical disc, such as a light-transmitting resin such as polycarbonate, polymethacrylate resin, or epoxy resin, or glass. The first substrate A1 has a thickness of 0.6 mm, and the second substrate A1 has a thickness of 0.6 mm. The substrate B1 has a thickness of 0.55 mm. Further, the thickness of the adhesive layer 2 is set to 0.1.
And the thickness of the optical disc 10 is approximately 1.2 mm.
mm, and the optical disk 10 has a diameter of 120 mm. Thus, the optical disk 1
0 is configured to have the same thickness and diameter as the CD for compatibility with the CD. The surface on the side opposite to the surface on which the second information recording layer B is provided is the light incident surface 3, and the first reproduction laser light L1 and the second reproduction laser light L2 are It is designed to be incident.

Further, the first and second information recording layers A and B
Are the pits P, each having an uneven shape corresponding to the reproduction wavelength.
Information is recorded by A and PB. As described above, in the first information recording layer A, since information is recorded at a high density,
The pit PA is formed smaller (shorter) than the pit recorded on the CD, and the track pitch is formed narrower than the CD.
For example, it is formed with a shortest pit length of 0.41 μm and a track pitch of 0.73 μm. On the other hand, since the information of the signal format corresponding to the CD is recorded on the second information recording layer B as described above, the pits PB have the same size as the CD and are formed at the same track pitch as the CD.
For example, the shortest pit length is 0.9 μm and the track pitch is 1.
It is formed at 6 μm.

The adhesive layer 2 is made of, for example, a transparent ultraviolet curable resin mainly composed of an acrylate or a methacrylate. This resin is suitable for use in the present invention because it has a high polymerization rate and cures in a short time. On the second reflection layer B2, a protective film 4 made of an ultraviolet curable resin or the like is formed, and on the protective film 4 is a label surface 5 for displaying recorded information contents and the like.

On the other hand, as shown in FIG. 2B, the optical disk 11 of the second embodiment of the present invention has two information recording layers formed on one substrate (second substrate B11). . That is, the first information recording layer A is formed on the lower surface of the second substrate B11, and the second information recording layer B is formed on the upper surface. The second substrate B11 has a structure in which the surface on which the first information recording layer A is formed is bonded to a flat substrate (first substrate A11) via the adhesive layer 2. The optical disk 11 has a diameter of 120 mm as in the optical disk 10, the first substrate A11 has a thickness of 0.55 mm, the second substrate B11 has a thickness of 0.6 mm, and the adhesive layer 2 has a thickness of 0 mm. .05 mm, and the thickness of the disc is
1.2 mm. Therefore, the optical disk 1
1, the thickness and the diameter are the same as those of the CD.

By configuring the optical disk as described above, it is possible to exhibit effects which have not been considered conventionally. That is, when the optical disks 10 and 11 are viewed from the viewpoint of a CD, since the disk substrate has a substrate accuracy capable of reproducing a signal for high density, the signal quality derived from the substrate accuracy is significantly higher than that of a CD. Improved and very reliable. For example, for the warp angle of a disc,
Since the signal error rate is half or less than that of the above, the signal error rate is reduced. This has the effect of reducing the signal error rate because the substrate accuracy is improved for all items of disk thickness variation, birefringence, and eccentricity.
In the above optical discs 10 and 11, specific examples of the thickness of each of the first substrate A1, the second substrate B1, and the adhesive layer 2 and the specific numerical values of the diameter of the disc are only examples, and the present invention is not limited thereto. Is not limited to this.

Next, the optical disk 1 constructed as described above
A case will be described in which 0 and 11 are mounted and reproduced in respective reproduction devices for high-density reproduction and low-density reproduction (CD).
When the optical disks 10 and 11 are mounted on a high-density reproduction player, the first reproduction laser beam L1 is emitted from the high-density reproduction player. As described above, the first reflection layer A2 has a high reflectance with respect to the first reproduction laser beam L1. For this reason, the focus of the optical pickup is on the first information recording layer A, and the information on the first information recording layer A is reproduced.

When the optical disks 10 and 11 are mounted on an existing low-density reproduction player such as a CD player, the second reproduction laser beam L2 is emitted from such a player. The first reflection layer A2 has a low reflectance with respect to the second reproduction laser light. Here, the second information recording layer B is provided at a position corresponding to the optical length of the optical pickup of the CD player. Further, the first reflection layer A2 is configured so that the reflectance of the optical discs 10, 11 with respect to the irradiation of the second reproduction laser beam L2 is about 5%. Therefore, the focus of the optical pickup is on the second information recording layer B, and the low-density reproduction player reproduces the second information recording layer B.

Next, a method of manufacturing the optical disks 10 and 11 will be described. Each of the optical disks 10 and 11 has a structure in which two substrates are bonded together.
The substrate on which the first information recording layer A is formed is different. First, a method for manufacturing the optical disc 10 will be described. FIG. 3 is a diagram for explaining a method of manufacturing the optical disc according to the first embodiment of the present invention. As shown in FIG. 1A, a first information recording layer A is provided on one surface of a first substrate A1.
The pits PA of the second information recording layer B are formed on one surface of the second substrate B1. The first substrate A1 on which these pits PA and PB are formed
The second substrate B1 is manufactured by an injection molding method using a stamper, a 2P method, or the like, similarly to a conventional CD. The thickness of the first substrate A1 or the second substrate A2 is set to, for example, 0.55 mm in consideration of the thickness of the bonding, and the optical length of the optical disk after bonding is set to 1.2 mm. I do. Also, the first information recording layer A serving as a bonding surface
First, a first reflection layer A2 is formed. The first reflection layer A2 is formed by sputtering silicon (Si) by a sputtering method, an evaporation method, or the like. When the first reflective layer A1 is made of silicon, if the film thickness changes, the signal shape at the time of reproduction changes.
Thoroughly control the film thickness. In addition, before bonding the first substrate A1 and the second substrate B1, the second reflective layer B2 may be formed in advance on the signal surface of the second substrate B1. Also,
If the thickness of both silicon and aluminum is about 50 nm, it is possible to obtain a reflectance that satisfies the standards for both high-density reproduction and low-density reproduction.

Next, an ultraviolet curable resin serving as the adhesive layer 2 is dropped on the surface of the first information recording layer A of the first substrate A1, and the flat surface of the second substrate B1 is bonded. continue,
The resin is spread by a spin coater, and then the first substrate A
The resin is cured by irradiating ultraviolet rays from below 1 or above the second substrate B2 (when the second reflective layer B2 is formed in advance, ultraviolet rays are irradiated only from below the first substrate A1). Do).

When the resin is cured as described above, the first substrate A1 and the second substrate B1 are bonded to each other as shown in FIG. Thereafter, a second reflective layer B2 made of aluminum or the like is formed on the upper surface of the second substrate B1, and a protective film 4 is formed by spin-coating an ultraviolet curable resin or the like on the second reflective layer B2. The optical disk 10 is manufactured by performing label printing on the surface.

Next, a method for manufacturing the optical disk 11 will be described with reference to FIG. FIG. 4 is a diagram for explaining a method of manufacturing an optical disc according to the second embodiment of the present invention.
In the optical disc 11, a first information recording layer A is formed on a lower surface of a second substrate B1, and a second information recording layer B is formed on an upper surface. The second substrate B11 is provided with a stamper S for forming a first information recording layer A as shown in FIG.
Stamper S2 for forming the first and second information recording layers B
Then, the above-mentioned substrate material is sandwiched and molded.

Since the first information recording layer A and the second information recording layer B are read from the same direction, the pits PB of the second information recording layer B are formed in a concave shape.
The pit PA of the information recording layer A needs to be formed in a convex shape. Therefore, for example, when a stamper for forming a CD substrate (a pit portion is convex) is used as the stamper S2, the stamper S1 has an inverse relationship between the stamper S2, the pits and the land (the pit portion). Is concave).

A first reflective layer A2 is formed on the surface of the first information recording layer A of the second substrate B11 constructed as described above, and the first information recording layer A side is flattened on both sides. The substrate is bonded to the first substrate A11 (FIG. 13B). The first substrate A11 has a thickness of 0.5 to 0.6 mm.
For this bonding, as in the case of the optical disk 10, an ultraviolet curable resin is used, and this ultraviolet curable resin becomes the adhesive layer 2. Then, after the ultraviolet curable resin is cured (FIG. 2C), it is manufactured in the same manner as the optical disk 10.
This method of manufacturing the optical disk 11 is desirable in mass production because not only can two substrates be formed at one time, but also the eccentricity of the disk can be controlled in one mold.

In the above embodiment, a read-only optical disk has been described, but the present invention is of course applicable to a write-once type or rewritable type optical disk.

Here, in other words, in other words,
The present invention can be said to be the following optical disc. That is, the optical disc of the present invention is a multi-layer optical disc having a plurality of information recording layers reproduced by laser light having different reproduction wavelengths in one optical disc, and a high-density optical pickup for emitting short-wavelength laser light. A high-density information recording layer at the position of the optical length, and a low-density information recording layer at the position of the optical length of the low-density optical pickup that emits laser light of a long wavelength. The high-density information signal has a narrower track pitch and a shorter shortest pit length than the low-density information recording layer, and the track pitch and the shortest pit length of the high-density information recording layer are (low-density information recording layer). Track pitch and shortest pit length) ×
((Wavelength of laser beam for reproducing high density information) / (wavelength of laser beam for reproducing low density information)) or not more than this value.

In other words, in other words, the present invention can be said to be the following optical disc. That is, the optical disc of the present invention includes a high-density information recording layer having a relatively narrow track pitch and short shortest pits and a low-density information recording layer having a relatively wide track pitch and long shortest pits in one optical disc. In a multilayer optical disc having at least two different recording densities, a high-density information recording layer located at the optical length of a high-density optical pickup for emitting short-wavelength laser light, and a low-density information recording layer for emitting long-wavelength laser light A low-density information recording layer at the position of the optical length of the high-density optical pickup, and the track pitch and shortest pit length of the high-density information recording layer are (track pitch and shortest pit length of the low-density information recording layer) × From the value of ((optical length of high density optical pickup) / (optical length of low density optical pickup)), (track pitch and shortest pit length of low density information recording layer) × ((optical length of the high density optical pick-up) ×
(Wavelength of laser beam for high density information reproduction) / ((optical length of low density optical pickup) × (wavelength of laser beam for low density information reproduction)).

[0030]

As described above, according to the optical disk of the present invention, the first information recording layer having a high recording density is provided at a position corresponding to the optical length of the optical pickup of the high-density reproducing player. Is provided at a position corresponding to the optical length of the optical pickup of the low-density reproducing player, and the shortest pit length of the first information recording layer is longer than the shortest pit length of the second information recording layer. By making it smaller,
It is possible to provide an optical disc that can be reproduced by both the high-density reproduction player and the low-density reproduction player.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a basic configuration of the present invention.

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

FIG. 3 is a diagram for explaining a method of manufacturing the optical disc according to the first embodiment of the present invention.

FIG. 4 is a diagram for explaining a method of manufacturing an optical disc according to a second embodiment of the present invention.

FIG. 5 is a diagram illustrating spectral characteristics of the optical disc in FIG. 1;

FIG. 6 is a diagram showing an example of the structure of a conventional optical disc.

[Explanation of symbols]

 1, 10, 11 optical disk 2 adhesive layer 3 light incident surface 4 protective film A first information recording layer A1, A11 first substrate A2 first reflection layer B second information recording layer B1, B11 second substrate B2 Second reflective layer

Claims (3)

[Claims] 1. A first optical pickup which emits the first laser light is formed at a position corresponding to an optical length of the first optical pickup and reproduces the first information at a wavelength of the first laser light.
A first information recording layer on which information is recorded, and the second laser light is reproduced in order to reproduce second information at a wavelength of the second laser light longer than the wavelength of the first laser light. A second information recording layer formed at the position of the optical length of the second optical pickup that emits light, and wherein the second information is recorded. The shortest pit length of the first information recording layer is An optical disc characterized by being shorter than the shortest pit length of the second information recording layer. 2. A method for reproducing first information at a wavelength of a first laser light, the optical pickup being formed at a position of an optical length of a first optical pickup for emitting the first laser light, and
A first information recording layer on which information is recorded, and the second laser light is reproduced in order to reproduce second information at a wavelength of the second laser light longer than the wavelength of the first laser light. A second information recording layer formed at the position of the optical length of the emitting second optical pickup and recording the second information; and a first substrate on which the first information recording layer is formed. A second substrate on which the second information recording layer is formed; a first information recording layer side of the first substrate;
An adhesive layer for adhering the substrate on the side opposite to the second information recording layer side, wherein the shortest pit length of the first information recording layer is the shortest pit length of the second information recording layer. An optical disc characterized by being smaller than the optical disc. 3. A first optical pickup which emits the first laser light is formed at a position corresponding to an optical length of the first optical pickup and reproduces the first information at a wavelength of the first laser light.
A first information recording layer on which information is recorded, and the second laser light is reproduced in order to reproduce second information at a wavelength of the second laser light longer than the wavelength of the first laser light. A second information recording layer formed at the position of the optical length of the second optical pickup that emits light and on which the second information is recorded; a first substrate having flat surfaces on both sides; A second substrate on which one information recording layer is formed and the second information recording layer is formed on the other surface; one surface of the first substrate and one of the second substrates; An optical disc, comprising: an adhesive layer that adheres to a surface of the optical disc, wherein a shortest pit length of the first information recording layer is smaller than a shortest pit length of the second information recording layer.