JP2010033712A - Optical disk and method for manufacturing optical disk - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a two-layer or three-layer optical disk made by laminating two disk substrates to satisfy both of low-density recording and high-density recording or medium-density recording together with them, and an optical disk unit for recording and reproducing the optical disk. <P>SOLUTION: The optical disk includes a first disk substrate which is the disc-like disc substrate made of a transparent synthetic resin and formed with a concave and convex shape on one surface corresponding to information and a first half transparent reflective film thereon to form a first information recording layer, a second disk substrate which is the disc-like disc substrate made of the transparent synthetic resin and formed with the concave and convex shape on one surface corresponding to the information and a second reflective film thereon to form a second information recording layer, and a transparent adhesion layer for laminating the first and second disk substrates, and the first and second reflective films are made of an Si compound. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

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

  2. Description of the Related Art Conventionally, a two-layer type optical disk is configured to have two information recording layers by bonding two disk substrates together to form an information recording layer formed inside each disk substrate.

  That is, in the case of a so-called double-sided single-layer type optical disc, the optical disc is recorded after the surface of the disk-shaped first disc substrate made of a transparent synthetic resin such as polycarbonate is formed into a pattern shape representing information. A semi-transparent film layer is formed as a layer, and a second disk substrate having substantially the same configuration as the first disk substrate is placed thereon via a transparent adhesive. By curing, two disk substrates are bonded together. In this case, the second disk substrate has a reflective film layer formed instead of the semitransparent film layer of the first disk substrate.

According to the optical disk having such a configuration, from the first disk substrate side, a light beam for recording and / or reproducing the optical disk, for example, a laser beam is a translucent that is an information recording layer of the first disk substrate. When irradiated so as to focus on the film layer, the information signal recorded on the information recording layer of the first disk substrate is reproduced based on the return light beam reflected by the translucent film layer. Become.
In contrast, when the light beam is irradiated so as to focus on the reflective film layer that is the information recording layer of the second disk substrate, the first light beam is reflected on the basis of the return light beam resulting from the reflection on the reflective film layer. The information signal recorded on the information recording layer of the second disk substrate is reproduced. Therefore, by using the same optical pickup from one side, the information recording layer of the first disk substrate and the information recording layer of the second disk substrate of the optical disk are recorded and / or reproduced.

Here, an optical disc in which the information recording layer of the first disc substrate and the information recording layer of the second disc substrate have different signal recording densities, for example, an optical disc in which the information recording layer on the incident side has a higher density is also proposed. Has been.
Such an optical disk is formed, for example, by using a light beam having a wavelength of 780 nm which is generally used for a low-density information recording layer, that is, an information recording layer of a second disk substrate, for example, a conventional compact disk (CD). There is also a device that can be played back by a playback device. As a result, a light beam having a wavelength of 780 nm is transmitted through the information recording layer of the first disk substrate and reflected by the information recording layer of the second disk substrate, and the return light is again returned to the first first disk substrate. The information recording layer of the second disk substrate is recorded and / or reproduced by being detected through the information recording layer.
On the other hand, the higher density information recording layer, that is, the information recording layer of the first disk substrate, is configured to correspond to a light beam having a shorter wavelength, for example, a wavelength of 650 nm or 635 nm. As a result, a light beam having a wavelength of 650 nm or 635 nm is reflected by the information recording layer of the first disk substrate, and the return light is detected, whereby recording and / or reproduction of the information recording layer of the first disk substrate is performed. Is to be performed.

JP-A-9-27143 Japanese National Patent Publication No. 11-511889

However, with the widespread use of optical discs having higher-density information recording layers (hereinafter referred to as medium density recording layers) corresponding to the above-described light beams with a wavelength of 650 nm or 635 nm, optical discs with higher density recording have been developed. Yes.
Such a high-density recording optical disk uses, for example, blue laser light having a wavelength of about 410 nm, and is reproduced by the above-described reproducing apparatus for an optical disk having a low-density recording layer or a medium-density recording layer. I can't.

  In view of the above-mentioned points, the present invention can cope with both low-density recording and high-density recording, or two layers or three-layers by laminating two disk substrates that can cope with both of these and medium-density recording. It is an object of the present invention to provide a layered optical disc and an optical disc apparatus for recording / reproducing the optical disc.

  An optical disk according to the present invention is a disk-shaped disk substrate made of a transparent synthetic resin, and has a concavo-convex shape corresponding to information formed on one surface, and a semitransparent first reflective film is formed thereon. The first disk substrate on which the first information recording layer is formed and the disk-shaped disk substrate made of a transparent synthetic resin, the uneven shape corresponding to the information is formed on one surface, and the second disk is formed thereon. An optical disc comprising: a second disc substrate on which a second information recording layer is formed by forming the reflective film; and a transparent adhesive layer that bonds the first and second disc substrates. , One of the first and second information recording layers has a higher density than the other, λ ≦ 460 nm, and N.I. A. It is configured to be recorded and / or reproduced with an optical parameter of ≧ 0.6, and the other of the first and second information recording layers is 615 nm ≦ λ ≦ 655 nm and N.I. A. It is configured to be recorded and / or reproduced with an optical parameter of = 0.6 plus or minus 0.05, and the first and second reflective films are composed of Si compounds.

In the optical disk according to the present invention, one of the first and second information recording layers has a pit parameter of 0.30 μm ≦ track pitch ≦ 0.70 μm and 0.15 μm ≦ shortest pit length ≦ 0.40 μm. And the other of the first and second information recording layers has a pit parameter of 0.70 μm ≦ track pitch ≦ 0.80 μm and 0.40 μm ≦ shortest pit length ≦ 0.45 μm. Features.
The optical disk according to the present invention is characterized in that the pit parameters for constituting the first and second information recording layers are set based on optical parameters applied to the DVD disk.

In the optical disk according to the present invention, the first reflective film is configured such that the reflectance at 380 nm ≦ λ ≦ 460 nm is 10% or more and the transmittance at 615 nm ≦ λ ≦ 655 nm is 40% or more. The second reflective film is characterized in that the reflectance at 615 nm ≦ λ ≦ 655 nm is 20% or more.
The optical disk according to the present invention is characterized in that the first and second reflective films are made of a Si compound.
Further, the transparent adhesive layer has a thickness of 10 to 100 μm.

  The method for forming an optical disk according to the present invention comprises forming a concavo-convex shape corresponding to information on one surface of two disc-shaped disk substrates made of a transparent synthetic resin, and forming a translucent shape on the formed concavo-convex shape. By forming a reflective film, a first information recording layer is formed on one of the two disk substrates and a second information recording layer is formed on the other, and the two disk substrates are bonded together by a transparent adhesive layer. In addition, one of the first and second information recording layers has a higher density than the other, λ ≦ 460 nm, and N.I. A. The optical information is recorded and / or reproduced with an optical parameter of ≧ 0.6, and the other of the first and second information recording layers has 615 nm ≦ λ ≦ 655 nm and N.I. A. The optical parameter is set to be 0.6 and ± 0.05, and recording and / or reproduction is performed, and the first and second reflective films are made of a Si compound.

  According to the present invention, a two-layer or three-layer optical disk by bonding two disk substrates, which can handle both low density recording and high density recording, or all of these and medium density recording. In addition, an optical disc apparatus for recording / reproducing the optical disc can be provided.

It is the schematic which shows the structure of the optical disk apparatus of the optical disk by this invention. It is the schematic which shows the structure of the optical pick-up in the optical disk apparatus of FIG. It is a partial expanded sectional view which shows 1st embodiment of the optical disk by this invention. It is a partial expanded sectional view which shows 2nd embodiment of the optical disk by this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 1 to 4.
The embodiments described below are preferred specific examples of the present invention, and thus various technically preferable limitations are given. However, the scope of the present invention is particularly limited in the following description. As long as there is no description which limits, it is not restricted to these aspects.

FIG. 1 is an overall configuration diagram of an optical disc apparatus for reproducing an optical disc according to a first embodiment of the present invention.
In FIG. 1, an optical disk apparatus 10 records a signal by irradiating a light beam onto a spindle motor 12 as a driving means for rotating the optical disk 11 and a signal recording surface of the rotating optical disk 11, and this signal recording surface. Are provided with an optical pickup 20 for reproducing a recording signal by a return light beam and a control unit 13 for controlling them.
Here, the control unit 13 includes an optical disk controller 14, a signal demodulator 15, an error correction circuit 16, an interface 17, a head access control unit 18, and a servo circuit 19.

  The optical disk controller 14 drives and controls the spindle motor 12 at a predetermined rotational speed. The signal demodulator 15 demodulates the recording signal from the optical pickup 20 to correct an error, and sends it to an external computer or the like via the interface 17. Thereby, an external computer or the like can receive a signal recorded on the optical disc 11 as a reproduction signal.

  The head access control unit 18 moves the optical pickup 20 to, for example, a predetermined recording track on the optical disc 11 by track jump or the like. The servo circuit 19 moves the objective lens held by the biaxial actuator of the optical pickup 20 in the focusing direction and the tracking direction at the moved predetermined position.

  FIG. 2 shows a configuration of the optical pickup 20 incorporated in the optical disc apparatus 10. In FIG. 2, the optical pickup 20 includes a beam splitter 22 as a light separating unit and an objective lens 23 as a light converging unit, which are sequentially arranged in the optical path of a light beam emitted from a light source 21, and the beam splitter 22. And a photodetector 24 disposed in the separation optical path.

The light source 21 includes, for example, a semiconductor laser element using semiconductor recombination emission, and emits a predetermined laser beam.
Here, as described later, the light source 21 is preferably a light beam having two or three types of wavelengths, for example, a light beam having a wavelength of 780 nm for a low-density recording optical disk, or a wavelength of 635 nm or 650 nm for a medium-density recording optical disk. In order to selectively emit a light beam and a light beam having a wavelength of 410 nm for a high-density recording optical disc, a semiconductor laser element (not shown) that emits the light beam having the wavelength is provided.
A plurality of light sources 21 may be provided for each wavelength.

  The beam splitter 22 is a beam splitter provided with the semi-transmissive film 22a inclined at 45 degrees with respect to the optical axis, and separates the light beam from the light source 21 and the return light from the signal recording surface of the optical disk 11. To do. That is, a part of the light beam from the light source 21 is transmitted through the semi-transmissive film 22 a of the beam splitter 22, and a part of the return light beam is reflected by the semi-transmissive film 22 a of the beam splitter 22. .

  The objective lens 23 is a convex lens, and focuses the light beam from the beam splitter 22 onto a desired recording track on the signal recording surface of the optical disk 11 that is rotationally driven. Here, the objective lens 23 is supported by a biaxial actuator (not shown) so as to be movable in the biaxial direction, that is, the focus direction and the tracking direction. The photodetector 24 is configured to have a light receiving unit for the return light beam reflected by the beam splitter 22.

  Here, the optical disc 11 according to the first embodiment of the present invention is configured as shown in FIG. In FIG. 3, an optical disk 11 is formed by attaching two disk-shaped disk substrates 31 and 32 having a thickness T of 0.6 mm made of a transparent synthetic resin such as polycarbonate, and the two disk substrates 31 and 32. A transparent adhesive layer 33 for matching the light beam L from the light source 21 of the optical pickup 20 is incident from above in FIG.

  The first disk substrate 31 has an inner side surface (lower surface in FIG. 3) formed in a concavo-convex shape corresponding to recording information, for example, and then a translucent reflective film 34 is formed thereon. The second disk substrate 32 has an inner side surface (lower surface in FIG. 3) formed in a concavo-convex shape corresponding to recording information, for example, and a total reflection film 35 is formed thereon.

Further, in the optical disc 11, the information recording layer formed by the reflective film 34 is configured as a high density recording layer, and the information recording layer formed by the reflective film 35 is configured as a low density recording layer.
Here, the high-density recording layer formed of the reflective film 34 has λ ≦ 460 nm and N.I. A. Recording and / or reproduction is performed with optical parameters of ≧ 0.6.
The low-density recording layer made of the reflective film 35 is 770 nm ≦ λ ≦ 830 nm and N.P. A. = 0.45 plus / minus 0.05 The optical parameters are set to be recorded and / or reproduced.

Further, the reflection film 34 is preferably made of a Si compound, and has a configuration such that the reflectance at 380 nm ≦ λ ≦ 460 nm is 10% or more and the transmittance at 770 nm ≦ λ ≦ 830 nm is 40% or more. Has been.
Here, when the reflectance is less than 10%, the amount of return light from the high-density recording layer is not sufficient, and the reproduction characteristics of the high-density recording layer deteriorate. On the other hand, when the transmittance is less than 40%, the amount of light applied to the low density recording layer decreases, and the reproduction characteristics of the low density recording layer deteriorate.

Here, for example, in the DVD disk (medium density recording layer) which is the optical recording medium of the highest density recording currently in practical use, λ = 0.635 or 0.65 μm, and N.I. A. = 0.6, track pitch (TP) = 0.4 μm, and the following relationship is established.
T. T. P. = 0.74 × (λ / 0.635) × (0.6 / NA)
Shortest pit length (Pmin) = 0.4 × (λ / 0.635) × (0.6 / NA)
As the optical parameters of this embodiment, the above-mentioned λ ≦ 460 nm and N.I. A. Substituting ≧ 0.6, T. P. ≦ 0.54 μm Pmin. ≦ 0.29 μm.
Further, the practical technical limit of the wavelength λ is 0.38 μm. A. Because the limit of 0.95 is the maximum. P. ≧ 0.28 μm Pmin. It can be seen that ≧ 0.15 μm.

In order to satisfy the above conditions, the semi-transmissive reflective film 34 is formed of a Si compound containing at least one element of nitrogen, oxygen, and hydrogen, as disclosed in JP-A-1-28802.
Here, the reflectance has a sine-square characteristic with respect to the thickness. Therefore, the reflectance is appropriately changed by changing the thickness.
Further, the semi-transmissive reflective film is not limited to the Si compound, but can also be configured by a metal thin film of gold or aluminum.

The transparent adhesive layer 33 is selected to have a thickness of 10 to 100 μm, for example. As a result, the high-density recording layer of the first disk substrate 31 and the medium-density recording layer of the second disk substrate 32 are separated from each other at an appropriate interval. The light beam from the light source 21 is surely focused.
Here, if the thickness is less than the lower limit, the distance between the high-density recording layer and the medium-density recording layer is too narrow, so that when the light beam of a predetermined wavelength is irradiated, the other recording layer As a result, the return light is generated and the reproduction characteristics are deteriorated.
If the thickness exceeds the upper limit, the amount of light is reduced when the light beam for the medium density recording layer is transmitted through the transparent adhesive layer. Therefore, the recording and / or reproduction characteristics are deteriorated.

The optical disc 11, the optical pickup 20, and the optical disc apparatus 10 according to the present embodiment are configured as described above and operate as follows.
First, the case of reproducing a high density recording layer will be described. That is, when the spindle motor 12 of the optical disc apparatus 10 rotates, the optical disc 11 is driven to rotate.
Then, the optical pickup 20 is moved in the radial direction of the optical disk 11 along a guide (not shown), so that the optical axis of the objective lens 23 is moved to a desired track position of the optical disk 11, thereby allowing access. Done.

  In this state, in the optical pickup 20, the light beam having a wavelength of 410 nm from the light source 21 passes through the beam splitter 22 and is focused on the high-density recording layer of the first disk substrate 31 of the optical disk 11 by the objective lens 23. The In this case, the objective lens 23 has a wavelength of 410 nm and N.I. A. It is designed so that ≧ 0.6. N. A. Is 0.6 or less, the light beam applied to the high-density recording layer is distorted by the influence of spherical aberration.

  Then, the return light including the signal from the high-density recording layer of the optical disk 11 is incident on the beam splitter 22 through the objective lens 23 again. Then, the light is reflected by the semi-transmissive film 22 a of the beam splitter 22 and forms an image on the photodetector 24. Thereby, based on the detection signal of the photodetector 24, the recording signal of the high-density recording layer of the optical disc 11 is detected, and a reproduction signal is generated.

  At that time, the signal demodulator 15 detects the tracking error signal and the focus error signal from the detection signal from the photodetector 24 by an appropriate method. The servo circuit 19 performs servo control via the optical disk drive controller 14 to perform focusing and tracking of the objective lens 23 of the optical pickup 20.

  Further, when reproducing the low density recording layer of the optical disk 11, it is performed as follows. That is, the optical disk 11 is rotationally driven and accessed by the optical pickup 20 in the same manner as in the reproduction of the low density recording layer.

In the optical pickup 20, the light beam having a wavelength of 650 nm from the light source 21 passes through the beam splitter 22 and is focused on the low density recording layer of the second disk substrate 32 of the optical disk 11 by the objective lens 23. In this case, the objective lens 23 has a wavelength of 650 nm with respect to this low density recording layer. A. = 0.60 plus or minus 0.05.
In this case, N.I. A. If the above condition is not satisfied, the light beam applied to the low-density recording layer is distorted due to the influence of spherical aberration.

Then, the return light including the signal from the low density recording layer of the optical disc 11 is incident on the beam splitter 22 through the objective lens 23 again. Then, the light is reflected by the semi-transmissive film 22 a of the beam splitter 22 and forms an image on the photodetector 24. Thereby, based on the detection signal of the photodetector 24, the recording signal of the low density recording layer of the optical disc 11 is detected, and a reproduction signal is generated.
The signal demodulator 15 detects the tracking error signal and the focus error signal from the detection signal from the photodetector 24 by an appropriate method. The servo circuit 19 performs servo control via the optical disk drive controller 14 to perform focusing and tracking of the objective lens 23 of the optical pickup 20.

  Thus, the optical disk 11 includes the high-density recording layer and the low-density recording layer, so that the low-density recording layer can be reproduced by a conventional optical disk device using a light beam having a wavelength of, for example, 780 nm. The high-density recording layer can be reproduced by a new dedicated optical disk device using a light beam having a wavelength of 410 nm, for example. For this reason, for example, when the same information is recorded in the high-density recording layer and the low-density recording layer, both reproducing apparatuses can be used.

  FIG. 4 shows a second embodiment of the optical disc according to the present invention. In FIG. 4, an optical disk 40 is composed of two disk substrates 41 and 42 and a transparent adhesive layer 43 for bonding these disk substrates 41 and 42, as with the optical disk 11 shown in FIG. Yes.

  As with the first disk substrate 31 in FIG. 3, the first disk substrate 41 has an inner side surface (lower surface in FIG. 4) formed in a concavo-convex shape corresponding to information, A transparent reflection film 44 is formed. After the upper and lower surfaces of the second disk substrate 42 are formed in a concavo-convex shape corresponding to information, a translucent reflective film 45 is formed on the upper surface in FIG. A total reflection film 46 is formed.

Further, the first information recording layer by the reflection film 44 is a high density recording layer, the second information recording layer by the reflection film 45 is a medium density recording layer, and the third information recording layer by the reflection film 46 is used. Are each configured as a low density recording layer. Here, the first information recording layer formed of the reflective film 44 has λ ≦ 460 nm and N.I. A. Recording and / or reproduction is performed with optical parameters of ≧ 0.6.
The second information recording layer made of the reflective film 45 is 615 nm ≦ λ ≦ 655 nm and N.I. A. Recording and / or reproduction is performed with an optical parameter of = 0.6 plus or minus 0.05. On the other hand, the third information recording layer made of the reflective film 46 has 770 nm ≦ λ ≦ 830 nm and N.I. A. = 0.45 plus / minus 0.05 The optical parameters are configured to be reproduced.

  Further, the reflection film 44 is preferably made of a Si compound, and the reflectance at 380 nm ≦ λ ≦ 460 nm is 10% or more, the transmittance at 615 nm ≦ λ ≦ 655 nm is 40% or more, and 770 nm ≦ λ ≦. It is configured such that the transmittance at 830 nm is 60% or more. The reflective film 45 is preferably made of a Si compound, and has a configuration such that the reflectance at 615 nm ≦ λ ≦ 655 nm is 20% or more and the transmittance at 770 nm ≦ λ ≦ 830 nm is 60% or more. Has been. On the other hand, the reflective film 46 is configured so that the reflectance at 770 nm ≦ λ ≦ 830 nm is 60% or more.

Here, if the reflectance of the reflective film 44 is less than 40%, the amount of return light from the first information recording layer will be insufficient, and the reproduction characteristics of the first information recording layer will deteriorate. In other words, if the transmittance is less than 60%, the amount of light applied to the second and third information recording layers and the amount of return light are insufficient. Recording and / or reproduction characteristics will deteriorate.
Also, if the reflectance of the reflective film 45 is less than 20%, the amount of return light from the second information recording layer will be insufficient, and the reproduction characteristics of the second information recording layer will deteriorate. If the transmittance is less than 60%, the amount of light applied to the third information recording layer and the amount of return light are insufficient, and the reproduction characteristics of the third information recording layer are deteriorated. It will be.
Furthermore, if the reflectance of the reflective film 46 is less than 60%, the amount of return light from the third information recording layer will be insufficient, and the reproduction characteristics of the third information recording layer will deteriorate. become.

Further, the first information recording layer has pit parameters of 0.30 μm ≦ track pitch ≦ 0.70 μm and 0.15 μm ≦ shortest pit length ≦ 0.40 μm. The second information recording layer has pit parameters of 0.70 μm ≦ track pitch ≦ 0.80 μm and 0.40 μm ≦ shortest pit length ≦ 0.45 μm. On the other hand, the third information recording layer has pit parameters of 1.40 μm ≦ track pitch ≦ 1.70 μm and 0.80 μm ≦ shortest pit length ≦ 1.0 μm.
Here, the reason for determining the track pitch is the same as in the first embodiment, and the composition and design method of the semitransparent (semi-transmissive) reflective film are the same as in the first embodiment.

The transparent adhesive layer 43 is selected to have a thickness of 10 to 100 μm, for example. As a result, the first information recording layer of the first disk substrate 41 and the second information recording layer of the second disk substrate 32 are separated from each other at an appropriate interval. Thus, the light beam from the light source 21 of the optical pickup 20 is surely focused.
Here, if the thickness is less than the lower limit, the distance between the first and second information recording layers is too narrow, so that when the light beam of a predetermined wavelength is irradiated, the return from the other recording layer. Light will be generated, and the reproduction characteristics will deteriorate. Further, when the thickness exceeds the upper limit, the amount of light decreases when the light beams for the second and third information recording layers pass through the transparent adhesive layer, and the second and third information recording layers are reduced. The amount of light applied to the information recording layer and the amount of return light will be insufficient, and the recording and / or reproduction characteristics will deteriorate.

  According to the optical disc 40 having such a configuration, the third information recording layer provided on the second disc substrate is reproduced by a conventional optical disc apparatus using a light beam having a wavelength of 780 nm, and light having a wavelength of 635 nm or 650 nm is reproduced. The second information recording layer provided on the second disk substrate is reproduced by the optical disk device using the beam, and the first disk substrate 41 is read by the new optical disk device using the light beam having a wavelength of 410 nm. The first information recording layer provided on the inner surface is reproduced.

  In the optical disc 40, the second information recording layer has λ ≦ 460 nm and N.I. A. ≧ 0.6 optical parameters, or 615 nm ≦ λ ≦ 655 nm and N.I. A. It may be configured to be reproduced with an optical parameter of = 0.6 plus or minus 0.05. In this case, the second information recording layer is reproduced by a light beam having the same wavelength of 410 nm as the light beam for reproducing the first information recording layer, and medium density recording by a conventional light beam having a wavelength of 635 nm or 650 nm. It can also be reproduced by an optical disk device for optical disks.

Further, in the optical disc 40, the third information recording layer has λ ≦ 460 nm and N.I. A. ≧ 0.6 optical parameters, or 615 nm ≦ λ ≦ 655 nm and N.I. A. = 0.6 plus or minus 0.05 optical parameters, or 770 nm ≦ λ ≦ 830 nm and N.I. A. It may be configured to be reproduced with an optical parameter of = 0.45 plus or minus 0.05.
In this case, the third information recording layer is reproduced by a light beam having the same wavelength of 410 nm, 635 nm, or 650 nm as the light beam for recording and / or reproduction of the first information recording layer or the second information recording layer. At the same time, it can also be reproduced by an optical disk device for a low density recording optical disk using a conventional light beam having a wavelength of 780 n.

  Further, in the above embodiment, the optical disk apparatus 10 describes the operation of the read-only optical disk apparatus. However, the present invention is not limited to this. Obviously, it may be a recording / reproducing optical disk apparatus configured to perform reproduction. Further, it is obvious that the high-density recording layer of the optical disk 11 is dedicated for reproduction, and the medium-density recording layer and the low-density recording layer may be configured to perform recording and reproduction. is there.

  As described above, according to the present invention, it is possible to cope with both low-density recording and high-density recording, or these and medium-density recording. It is possible to provide a three-layer optical disc and an optical disc apparatus for recording / reproducing the optical disc.

DESCRIPTION OF SYMBOLS 10 ... Optical disk apparatus, 11 ... Optical disk, 12 ... Spindle motor, 13 ... Control part, 14 ... Optical disk drive controller, 15 ... Signal demodulator, 16 ... Error correction circuit , 17 ... interface, 18 ... head access control unit, 20 ... optical pickup, 21 ... light source (semiconductor laser element), 22 ... beam splitter, 23 ... objective lens, 24. ..Photodetector, 31, 32, 41, 42... Disk substrate, 33, 43... Transparent adhesive layer, 34, 35, 44, 45. 46 ... Reflective film

Claims (5)

A disc-shaped disk substrate made of a transparent synthetic resin, which has a concave-convex shape corresponding to information formed on one surface, and a semitransparent first reflective film is formed thereon, thereby forming a first information recording A first disk substrate having a layer formed thereon;
A disk-shaped disk substrate made of a transparent synthetic resin, in which an uneven shape corresponding to information is formed on one surface, and a second reflective film is formed thereon to form a second information recording layer. A second disk substrate;
An optical disc comprising a transparent adhesive layer for bonding the first and second disc substrates,
One of the first and second information recording layers has a higher density than the other, λ ≦ 460 nm, and N.I. A. Configured to be recorded and / or reproduced with optical parameters ≧ 0.6,
The other of the first and second information recording layers is 615 nm ≦ λ ≦ 655 nm and N.I. A. Configured to be recorded and / or reproduced with optical parameters of = 0.6 plus or minus 0.05;
An optical disc, wherein the first and second reflective films are made of a Si compound. One of the first and second information recording layers has a pit parameter of 0.30 μm ≦ track pitch ≦ 0.70 μm and 0.15 μm ≦ shortest pit length ≦ 0.40 μm,
The other one of the first and second information recording layers has a pit parameter of 0.70 μm ≦ track pitch ≦ 0.80 μm and 0.40 μm ≦ shortest pit length ≦ 0.45 μm. Item 4. The optical disk according to Item 1.   The first reflective film is configured such that the reflectance at 380 nm ≦ λ ≦ 460 nm is 10% or more and the transmittance at 615 nm ≦ λ ≦ 655 nm is 40% or more, and the second reflective film includes: 3. The optical disk according to claim 2, wherein the optical disc is configured such that the reflectance at 615 nm ≦ λ ≦ 655 nm is 20% or more.   4. The optical disk according to claim 3, wherein the transparent adhesive layer has a thickness of 10 to 100 [mu] m. An uneven shape corresponding to information is formed on one surface of two disc-shaped disk substrates made of transparent synthetic resin,
By forming a translucent reflective film on the formed concavo-convex shape, a first information recording layer is formed on one of the two disk substrates, and a second information recording layer is formed on the other,
While bonding the two disk substrates together with a transparent adhesive layer,
One of the first and second information recording layers has a higher density than the other, λ ≦ 460 nm, and N.I. A. The optical information is recorded and / or reproduced with an optical parameter of ≧ 0.6, and the other of the first and second information recording layers has 615 nm ≦ λ ≦ 655 nm and N.I. A. = Configured to be recorded and / or reproduced with optical parameters of 0.6 plus or minus 0.05;
A method of forming an optical disc, wherein the first and second reflective films are made of a Si compound.

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