JPH08273199A - Optical disk and optical disk device - Google Patents

Abstract

PURPOSE: To enable compressed moving image information recorded by the standard MPEG 2 to be lowered to a prescribed error rate due to an error rate reducing effect by suppressing an error rate caused by an optical disk itself to be a prescribed value or downward. CONSTITUTION: This optical disk device has a 1st discoid light transmission substrate 101, a reflecting layer 103 provided on the substrate 101 and a protective layer 105 provided on the reflecting layer 103. Moreover, this disk device is equipped with a 1st member 111 for recording desired information, an adhesive layer 107 having a 1st surface and a 2nd surface bonded to a protective layer 105 and a 2nd member 112 having at least a 2nd light transmission substrate 102 bonded to the 1st surface of the adhesive layer 107. Then, the thickness of the optical disk is specified as, for instance, >=1.19mm. In addition, a warping amt. of the optical disk under rotation at a prescribed revolving speed is specified as <=±3 deg.. Thus, by prescribing the warping amt. of the whole optical disk at the prescribed revolving speed and the overall thickness of the optical disk and moreover the thickness of the substrates, the error rate caused by the optical disk itself is suppressed to be <=10<-4> .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc and an optical disc device.

[0002]

2. Description of the Related Art In recent years, digital signal processing technology for images and MPEG (Moving Picture Image Coding Experts)
With the progress of moving picture compression technology being promoted by standardization organizations called Group), instead of VTRs and laser disks, moving picture information such as movies is played for a long time in the same size as CDs (compact disks). Expectations for possible optical disks are increasing. For example, video information of 2 hours can be sent to a standard TV such as NTSC like a laser disk.
The capacity required for recording in the form of analog video signal of the system is 80 GB including audio, but MP
If a moving image compression technique defined by a standardized method called EG2 is used, even if the image quality is similar to that of a high quality VTR such as S-VHS, the capacity required to record this image information for 2 hours. Is about 4GB. The capacity of 4 GB has already been put to practical use in a write-once type optical disk with a diameter of 300 mm, but considering the future spread to general households, it is possible to achieve the same capacity with a CD size of 120 mm that is easy to handle. Required. That is, it is necessary to increase the recording density of the optical disk to be higher than that of the current CD.

In order to increase the recording density of an optical disc, small pits are formed on the optical disc with a narrower track pitch, and a reproducing light beam is focused on the optical disc so that minute pits on the optical disc can be read by a reproducing optical system. The spot size should be reduced. Among these, as a pit processing technique, for example, an optical disc master recording technique using a Kr ion laser beam (ultraviolet light) having a wavelength of 351 nm has been proposed, and it is possible to process a pit smaller than a conventional Ar ion laser. It is possible. Regarding the reproduction optical system, the beam spot diameter can be made smaller by shortening the wavelength of the reproduction light beam by a short wavelength light source such as a red LD and increasing the NA of the objective lens. With the progress of these technologies, it is possible to realize a technology of recording compressed moving image information by MPEG2 on one side of an optical disc for 2 hours or more and on both sides for nearly 5 hours.

By the way, when recording / reproducing compressed moving picture information according to MPEG2 on an optical disc, in order to realize a desired image quality, the total error rate of the recording / reproducing system, that is, the compression finally inputted to the MPEG2 decoder. It is required that the error rate of moving image information be about 10 ⁻²⁰ or less. The error rate is represented by the number of error bits per byte. The error rate of the compressed moving image information is reduced by signal processing such as waveform equalization and error correction for the reproduction signal from the optical disc, but the error rate reduction by this signal processing is currently limited to about 10 ^-16. . In order to realize the total error rate of 10 ^−20, it is necessary to reduce the error rate due to the optical disc itself to 10 ⁻⁴ or less. However, specific measures for ^reducing the error rate due to the optical disc itself to 10 ⁻⁴ or less are as follows.
Not found.

[0005]

As described above, MPEG is used.
When recording / reproducing compressed moving image information according to No. 2 on an optical disc, it is required that the error rate of the reproduced compressed moving image information be about 10 ⁻²⁰ or less. For that purpose, signals for waveform equalization and error correction are required. Considering the effect of reducing the error rate by the processing, it is necessary to reduce the error rate due to the optical disc itself to 10 ⁻⁴ or less.
The conventional technique has not found a concrete measure for that.

An object of the present invention is to provide an optical disk capable of reducing the error rate due to the optical disk itself to 10 ⁻⁴ or less, and an optical disk device using the optical disk.

[0007]

The present invention has taken the following means in order to solve the above problems. First of the present invention
An optical disc according to an aspect includes a disc-shaped first light-transmissive substrate, a reflective layer provided on the first light-transmissive substrate, and a protective layer provided on the reflective layer. A first member for recording desired information, an adhesive layer having a first surface and a second surface adhered to the protective layer, and a first adhesive layer
A second member having at least a second transparent substrate adhered to the surface, and the optical disc has a thickness of 1.19 m.
It is characterized by being m or more. Here, the thickness of the optical disk is preferably 1.32 mm or less. Further, it is preferable that the amount of warpage during rotation at a predetermined number of revolutions is within ± 0.3 °.

An optical disk according to a second aspect of the present invention is provided with a disk-shaped first light transmissive substrate, a reflective layer provided on the first light transmissive substrate, and the reflective layer. A first member for recording desired information, an adhesive layer having a first surface and a second surface adhered to the protective layer, and an adhesive layer adhered to the first surface of the adhesive layer. And a second member having at least a second transparent substrate, the first member
And the thickness of the second light transmissive substrate is 0.58 mm or more,
It is characterized by being 0.64 mm or less.

An optical disk according to a third aspect of the present invention is provided with a disk-shaped first light transmissive substrate, a reflective layer provided on the first light transmissive substrate, and the reflective layer. A first member for recording desired information, an adhesive layer having a first surface and a second surface adhered to the protective layer, and an adhesive layer adhered to the first surface of the adhesive layer. And a second member having at least a second transparent substrate, wherein the optical disc has a warp amount within ± 0.3 ° when rotated at a predetermined rotation speed. Here, the predetermined rotation speed is 1350 rpm.

A preferred embodiment of the above-mentioned optical disc of the present invention is as follows. (1) The second member further has a reflective layer provided on the second light transmissive substrate and a protective layer provided on the reflective layer, and records desired information. thing. (2) At least the diameter of the first light transmissive substrate is 1
Must be 19.7 mm or more and 120.3 mm or less. (3) At least the first light transmissive substrate is made of a material having a refractive index of 1.45 or more and 1.65 or less. (4) At least the material of the first light transmissive substrate is polycarbonate, resin containing polycarbonate, and PM.
Must be one of MA. (5) The adhesive layer is made of a hot melt adhesive. (6) The reflective layer is made of an aluminum film. (7) The protective layer is made of a photocurable resin. (8) At least the first light-transmissive substrate has flexibility, and the optical disc has higher rigidity than the first light-transmissive substrate. (9) At least the first light-transmissive substrate has a warp amount exceeding ± 0.3 ° when rotated at the predetermined rotation speed.

Another optical disk of the present invention is provided with a disk-shaped first light-transmissive substrate, a reflective layer provided on the first light-transmissive substrate, and the reflective layer. A first member having a protective layer and recording desired information;
An adhesive layer having a first surface and a second surface adhered to the protective layer; and a second member having at least a second transparent substrate adhered to the first surface of the adhesive layer, at least the If the warp amount of the first light-transmissive substrate at the time of rotation at the predetermined number of revolutions exceeds the range of ± 0.3 °, and the warp amount of the optical disc at the time of rotation at the predetermined number of revolutions is within ± 0.3 °. It is characterized by being.

The main object of the present invention is to define to what extent the amount of warp of the optical disk necessary to keep the error rate below a desired level should be suppressed. Here, in the second aspect of the present invention, at a predetermined rotation speed (1350 rpm), if the warp amount is ± 0.3 ° or less, it is specified that the error rate is a desired error rate (10 ⁻⁴ ) or less.

Since the warp amount of the optical disc depends on the total thickness of the optical disc, in the first aspect of the present invention, the warp amount is within ± 0.3 ° by setting the total thickness of the optical disc to 1.19 mm or more. Since it has been experimentally confirmed that the optical disc has such a thickness, the optical disc having such a thickness is a feature of the present invention. Therefore, the substrate thickness occupies most of the total thickness of the optical disc, and two optical discs (including a reflective layer and a protective layer) are attached to each other to form an optical disc, so that each substrate thickness is 0.58 mm or more. As a result, the total thickness of the optical disc becomes 1.19 mm or more.

Further, as described above, the optical disk according to the present invention has a predetermined number of rotations (that is, 135 when reproducing).
The amount of warp when rotating at a rotation speed of 0 rpm is ± 0.3
By being within the range of °, the error rate due to the optical disc itself can be suppressed to 10 ⁻⁴ or less. Therefore,
Even when reproducing compressed moving image information recorded in the MPEG2 standard, the effect of reducing the error rate by the signal processing such as waveform equalization and error correction is reduced by the MPEG.
It is possible to reduce the error rate of the compressed moving image information input to the decoder to about 10 ⁻²⁰ or less which is practically required to maintain a desired image quality.

If the substrate thickness is made too large in order to increase the overall thickness of the optical disc, the aberration of the light beam generated on the substrate due to the tilt of the optical disc with respect to the light beam increases, and the signal of the reproduction signal is increased. The window margin at the time of identifying data in the processing system decreases, and conversely the error rate increases. In order to solve this, by setting the upper limit of the substrate thickness to 0.64 mm, it is experimentally confirmed that the window margin is secured at 10% or more and the error rate due to the optical disc itself is suppressed to 10 ^-4 or less. It was In this case, the upper limit of the total thickness of the optical disc is 1.32 mm.

The optical disc has a recording area and a non-recording area located inside thereof, and the thickness of the non-recording area is expected to be larger than that of the recording area because a label or the like is attached to a part of the non-recording area. . Considering the thickness of the label, for example, if the thickness of the label is 0.1 mm, the thickness of the optical disc in the non-recording area is 1.29 mm or more and 1.52.
mm or less.

An optical disk device according to the present invention is a disk-shaped first light-transmissive substrate, a reflective layer provided on the first light-transmissive substrate, and a protective layer provided on the reflective layer. A first member for recording desired information, an adhesive layer having a first surface and a second surface adhered to the protective layer, and at least an adhesive layer adhered to the first surface of the adhesive layer. An optical disc comprising a second member having a second transparent substrate, wherein a warp amount during rotation at a predetermined rotation number is within ± 0.3 °, and a rotation driving means for rotating the optical disc at a predetermined rotation number. A light irradiating means for irradiating the optical disc with a light beam through an objective lens; a light detecting means for detecting reflected light of the light beam emitted from the light irradiating means to the optical disc; and an output of the light detecting means. Corresponding to the information recorded on the optical disc from the signal A signal reproducing means for obtaining the reproduced signal and an information restoring means for restoring the information recorded on the optical disc from the reproduced signal obtained by the reproducing means, and the warp amount when the optical disc is rotated at the predetermined rotation speed. Including the above, the inclination angle of the optical disc with respect to the light beam is 10 mrad or less.

Here, the information restoration means, the signal reproduction means equalizes the waveform of the reproduction signal with the data identification means for identifying the data of the reproduction signal after being equalized by the waveform equalization means. Waveform equalizing means, and the information restoring means decodes the data corrected by the error correcting means and the error correcting means that performs error correction on the data obtained by the data identifying means. Decoding means for restoring the information recorded on the optical disc. Further, it is preferable that the numerical aperture of the objective lens is approximately 0.6, and the wavelength of the light beam is approximately 650 nm.

In the optical disk apparatus according to the present invention, the optical disk according to the second aspect of the present invention is used, and the tilt angle of the optical disk with respect to the light beam including the warp amount when the optical disk rotates at a predetermined rotation speed (eg, 1350 rpm). To 10m
It is below ad. The value that the tilt angle of the optical disk with respect to the light beam is 10 mrad or less is a permissible value that is practically required to reduce the error rate of the reproduction signal input to the signal processing system to 10 ⁻⁴ or less. For the optical disc of the above, the amount of warpage during rotation at a predetermined number of rotations is ±
By limiting the angle to within 0.3 ° (about ± 5.24 mrad), the requirements for the accuracy of the mounting angle of the optical head are alleviated.

As described above, according to the present invention, the error rate due to the optical disc itself is set to 10 ⁻⁴ by defining the warp amount of the entire optical disc at a predetermined rotation speed, the total thickness of the optical disc, and the substrate thickness. It becomes possible to suppress below.

[0021] Accordingly, the error rate reduction effect of compressed moving picture information recorded by the MPEG2 standard according to the signal processing due to waveform equalization and error correction according to the present invention, until the error rate of practically required 10 ^-20 It is possible to provide an optical disc and an optical disc device that can be lowered and input to the MPEG decoder.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings. Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1A and 1B are a perspective view and a sectional view of an optical disc 100 according to an embodiment of the present invention.

In the optical disk of the present invention, a reflective layer 103 for reflecting light is formed on one surface of each of the disk-shaped light transmissive substrates 101 and 102 in which pits corresponding to recorded information such as compressed moving image information are formed. , 104 is applied,
Further, protective layers 105 and 106 for mainly preventing the oxidation of the reflective layers 103 and 104 are further formed thereon, and have first and second information recording members 111 and 112. And
The first and second information recording members 111 and 112 are bonded together with the protective layers 105 and 106 facing each other with an adhesive layer 107 made of a thermosetting adhesive, and integrated to form the optical disc 100. To do. The optical disc 1
A clamping hole 108 for clamping is formed in the center of 00, and a clamping zone 109 is provided around it.

The adhesive layer 1 is shown in FIGS. 1 (a) and 1 (b).
Although an optical disc having the first and second information recording members on both sides of 07 is illustrated, the present invention may be applied to an optical disc having the information recording member on only one side. In this case, when the optical disc has only the first information recording member, the second information recording member may have a structure in which it is not necessary to record information, for example, as follows. (1) Light-transmissive substrate only (FIG. 2 (a)) (2) Light-transmissive substrate and reflective layer (FIG. 2 (b)) (3) Light-transmissive substrate and protective layer (FIG. 2 (c)) ( 4) Light-Transmissive Substrate, Reflective Layer, and Protective Layer (FIG. 2D) In the above configuration, the configuration of (4) is the same as that of the first information recording member, but information is recorded Therefore, the second information recording member does not have to have a structure having pits as shown in FIG. 1B. This structure is the same in the configurations (2) and (3).

The material of each part will be described. Board 10
1, 102 are made of a resin such as polycarbonate or PMMA (polymethylmethacrylate), or a resin containing these as a main component. Reflective layers 103, 104
Is an aluminum thin film. Protective layer 105, 106
Is formed of a photocurable resin (ultraviolet curable resin). The adhesive layer 107 is a hot melt adhesive (thermoplastic resin bonding agent), for example, polyvinyl ether paraffinic _{material; [- CH 2 -CH = CH} -CH 2] n - [CH 2 -
CH (OCH ₃₎ - consisting] _{n '.}

At the time of reproduction, a reproduction light beam emitted from an LD (not shown) and incident through the reproduction optical system is transmitted to the optical disc 100 through the objective lens 203 to the optical disc 100.
(Or 102) is incident from the side, and the reflective layer 103 (or 10
4) It is focused as a minute beam spot on top. Then, the reflected light from the reflective layer 103 (or 104) passes through the objective lens 203 in the opposite direction to the incident light, and then passes through an optical path separated from the optical path of the incident light by the reproduction optical system to perform optical detection (not shown). Detected by the vessel.

FIG. 3 shows an embodiment of an optical disc device for reproducing the compressed moving image information recorded on the optical disc 100. In FIG. 3, the optical disc 100 uses substrates 101 and 102 having a thickness of about 0.6 mm, as will be described later. Therefore, the optical disc 100 is more resistant to dust and dirt attached to the surface than a CD using a substrate having a thickness of 1.2 mm. Therefore, the cartridge 200 can be housed. As described above, by housing the optical disc 100 in the cartridge 200, how to hold the disc, dust,
It eliminates the need to pay attention to fingerprints, etc., and is advantageous in terms of handling and carrying. When the disc is exposed like a CD, it is necessary to determine the error correction capability in consideration of an unexpected situation such as a scratch, but if the cartridge 200 is used, such consideration is unnecessary.
The LDC Reed-Solomon error correction method can be used on a sector-by-sector basis as used in a read / write type optical disc. As a result, for example, when the optical disk is formatted in units of 2 k to 4 k bytes, C
The recording efficiency can be improved by 10% or more as compared with D.

As a modulation system of information recorded on the optical disc 100, for example, a 4/9 modulation system is used, and when the track pitch on the optical disc 100 is 0.72 μm and the pit pitch is 0.96 μm, the conventional CD format is obtained. In comparison, the pit density ratio is 3.84 times, and the modulation method is 2
Since 0% and format efficiency are expected to increase by 10%, a total capacity increase of about 5.1 times can be expected. As described above, the moving image information such as a movie is transferred to SV.
When playing back with high image quality equivalent to HS, 4.5 including sound
Since the rate is Mbps, the capacity required for 2 hours of reproduction is 4 GB. By increasing the capacity by 5.1 times as described above, this capacity of 4 Gbytes can be realized on one side of the disk. Furthermore, FIG. 1 (a) and FIG. 1 (b)
When the optical disc 100 as shown in (2) is double-sided, a maximum of 4 hours or more and nearly 5 hours can be recorded on one optical disc.

Returning to FIG. 3, the optical disk 100 is chucked by the taper cone 220 and is rotated by the spindle motor 201 at a rotation speed of, for example, 1350 rpm. The spindle motor 201 is driven by a spindle motor drive circuit 202.

The reproducing optical system is constructed as follows. The objective lens 203 shown in FIG. 1B is arranged so as to face the optical disc 100. The objective lens 203 can be moved in the optical axis direction by the focus coil 204 and in the track width direction by the tracking coil 205. The LD (semiconductor laser) 207 is the LD driver 20.
6 and its oscillation wavelength is, for example, 650 nm. The light beam emitted from the LD 207 is collimated by the collimator lens 208 and then enters the polarization beam splitter 209. Since the light beam emitted from the LD 207 generally has an elliptic far-field pattern, if a circular pattern is required, a beam shaping prism (not shown) may be arranged after the collimator lens 208. The light beam that has passed through the polarization beam splitter 209 is focused by the objective lens 203, and the optical disc 1
00 from the substrate 101 (or 102) side. The numerical aperture NA of the objective lens 203 is, for example, 0.6.

The reflective layer 103 (or 1 of the optical disc 100
The light reflected by 04) passes through the objective lens 203 in the direction opposite to the incident light beam, is reflected by the polarization beam splitter 209, passes through the detection optical system such as the condenser lens 210 and the cylindrical lens 211, and the photodetector 212. Incident on. The photodetector 212 is, for example, a 4-division photodetector, and its four detection outputs are input to an amplifier array 213 including an amplifier and an adder / subtractor. The amplifier array 213 generates a focus error signal F, a tracking error signal T and a reproduction signal. The tracking error signal T is obtained as a push-pull signal by a method called the push-pull method, for example. The focus error signal F and the tracking error signal T are supplied to the focus coil 204 and the tracking coil 205 via the servo controller 214, respectively. This controls the movement of the objective lens 203 in the optical axis direction and the track width direction,
The reflective layer 103 (or 1 which is the recording surface of the optical disc 100
Focusing of the light beam on the surface of 04) and tracking on the target track are performed.

The reproduction signal from the amplifier array 213 is input to the signal processing circuit 215, where it is subjected to waveform equalization and binarization processing to obtain a reproduction signal corresponding to the information recorded on the optical disc. Details of waveform equalization will be described later. In the binarization process, the reproduced signal after waveform equalization is PLL
A channel clock, which is a basic clock when information is recorded on the optical disc 100, is extracted from the reproduction signal by the (phase synchronization circuit) and the data identification circuit, and based on this channel clock, the reproduction signal “0”,
By identifying "1", the data of the information recorded on the optical disc 100 is identified, and the data pulse is obtained. That is, by comparing the reproduced signal after waveform equalization with an appropriate threshold value within a predetermined time width (referred to as a detection window width or window width) based on the rising or falling timing of the channel clock, data identification is performed. I do.

The data pulse thus detected from the signal processing circuit 215 is input to the disk controller 216, and the disk controller 216 performs format decoding, error correction, etc. to restore the information recorded on the optical disk. The signal restored by the disk controller 216 is input to the MPEG2 decoder / controller 217 as a bit stream of moving image information. On the optical disc 100, data obtained by compression-encoding moving image information according to the MPEG2 standard is printed on the substrates 101, 10.
2 is recorded as a pit pattern. Therefore,
The MPEG2 decoder / controller 217 decodes (decompresses) the input bit stream to reproduce the original moving image information. The reproduced moving image information is input to the video signal generation circuit 218 and added with a blanking signal or the like to be a video signal of a predetermined television format such as the NTSC format, which is displayed on a display not shown.

In the above description of the disk device, it is assumed that a moving image is recorded on the optical disk. However, the present invention is not limited to this, and data other than moving image data (for example, application When reproducing a program, audio data, etc.), the disk controller 216 outputs digital data as it is, for example,
It can be output to the main memory to perform a predetermined process.

The optical disc 100 of the present invention will be described in more detail. In FIG. 4, the optical disc 100 is rotated by the spindle motor 201 at a predetermined rotation speed (for example, 1350 rp).
It is the figure which exaggerated and showed the state when rotating in m). In the present invention, the rotation speed of the optical disc 100 is 1350r.
The optical disc 100 is configured such that the warp amount in pm (hereinafter, simply referred to as “warp amount”), that is, the angle θ formed by the optical disc 100 with respect to the reference surface S is within ± 0.3 ° (about 5.24 mrad). It is characterized by having done. Reference plane S
Is a surface perpendicular to the rotation axis of the optical disc 100 (that is, the rotation axis of the spindle motor 201 in FIG. 3), and the optical disc 100 is generally warped upward with respect to the reference plane S as shown by the solid line. , As shown by the broken line, it warps downward. Further, the optical disc 100 may locally warp upward or downward. In the present invention, the warp amount θ of the optical disc 100 is set within ± 0.3 ° in this way, so that the optical disc 1 can be described as follows.
As the error rate of the reproduced signal due to 00 itself, a value of 10 ⁻⁴ or less, which is the original request, can be realized.

FIG. 5 shows an optical disk 100 with an objective lens 2
Optical beam for reproduction incident on the optical disc 1 and the optical disc 1
The angle φ formed by a line perpendicular to the plane of 00 (this is referred to as a disk tilt angle) is shown.

The surface of the optical disc 100 and the light beam should ideally be 90 °, but in reality, medium factors such as the above-mentioned warpage of the optical disc 100 and the optical head (objective) shown in FIG. Lens 203, focus coil 20
4, the tracking coil 205, the LD 207, the collimator lens 208, the polarization beam splitter 209, the condenser lens 210, the cylindrical lens 211, etc.).
Deviate from °. This deviation is called disc tilt. The magnitude of this deviation, that is, the disc tilt angle φ is the sum of both medium factors such as the above-described warpage of the optical disc 100 and device factors such as an error in the mounting angle of the optical head. In practice, the disc tilt angle φ is related to the error rate of the reproduction signal, and it is desirable to keep it below 10 mrad.

FIGS. 6A and 6B are views showing data obtained by actually measuring the relationship between the warp amount θ of the optical disc 100 and the error rate caused by the optical disc 100.
6A, the warp amount θ1 in the radial direction (track width direction) of the optical disc 100 is plotted, and in FIG. 6B, the warp amount θ2 in the circumferential direction (track direction) of the optical disc 100 is plotted on the horizontal axis. As is clear from FIGS. 6A and 6B, in order to suppress the error rate due to the optical disc 100 to 10 ⁻⁴ or less in both the radial direction and the circumferential direction, the warpage amount θ (θ1 , Θ2) ± 5.24 mra
It can be seen that it may be suppressed within d, that is, within ± 0.3 ° described above.

By the way, the warp amount θ of the optical disc 100 greatly depends on the thickness (total thickness) t of the optical disc 100,
The warp amount θ decreases as the total thickness t increases.
FIG. 7 is a diagram showing the relationship between the total thickness t of the optical disc 100 and the warp amount θ. From FIG. 7, the total thickness t of the optical disc 100 is shown.
By setting 1.19 mm or more, the number of rotations is 1350
It is apparent that the amount of warpage θ at rpm is suppressed within ± 5.24 (mrad), that is, within ± 0.3 °.

Next, a specific example of dimensions of each part of the optical disc 100 will be described. FIG. 8 shows a preferable range of the diameter of each part of the optical disc 100. As shown in FIG. 8, the outer diameter D of the optical disc 100 is D = 120 ± 0.3 m.
m, that is, 119.7 mm or more and 120.3 mm or less,
The diameter D1 of the clamping hole 108 is 15 to 15.1.
mm, the inner diameter D2 of the clamping zone 109 is 22 m or more, the outer diameter D3 is 33 mm or less, and the inner diameter of the recording area (outer diameter of the non-recording area) is 47.6 mm or more and 48 mm or less,
The outer diameter D4 is set to 116 mm or less.

FIG. 9 shows the thickness of each part of the optical disc 100. As shown in FIG. 9, the total thickness t of the optical disc 100 is
Is 1.19 mm or more and 1.32 mm or less, the substrate 101,
The thickness t1 of 102 is 0.58 mm or more and 0.64 mm or less, and the thickness t2 of the protective layers 105 and 106 is 5 μm or more, 1
0 μm or less, the thickness t3 of the adhesive layer 107 is 5 μm or more, 2
The thickness t4 of the reflective layers 103 and 104 is about 0.01 μm or less.

The total thickness t of the optical disc 100 in the recording area in FIG.
05, 106, the adhesive layer 107, and the reflective layers 103, 104
Total thickness (2 x t1 + 2 x t2 + t3 + 2 x t4)
And is in the range of 1.19 to 1.32 mm. on the other hand,
The clamping zone 109 in the non-recording area in FIG.
The area outside the area of 0.1 to 0.2 for displaying the title of information recorded on the optical disc 100 and the like.
Since it is expected that a label having a thickness of about mm will be formed, the total thickness t of the optical disc 100 is (2 × t1 + 2 × t2 + t3 + 2).
The thickness of the label is further added to xt4), for example, in the range of 1.29 to 1.52 mm.

As is clear from the numerical example shown in FIG.
The thicknesses t2 and t3 of the protective layers 105, 106 and the adhesive layer 107 are on the order of microns, and the thickness t of the reflective layer 103 is t.
4 is in the order of angstroms, and the thickness t1 of the substrates 101 and 102 occupies most of the total thickness t of the optical disc 100. Moreover, the protective layers 105, 106,
Thicknesses t2, t3 and t of the adhesive layer 107 and the reflective layer 103
No. 4 cannot be made too thick in terms of process. Therefore, increasing the total thickness t of the optical disc 100 means increasing the thickness t1 of the substrates 101 and 102. When the thicknesses t2, t3, and t4 of the protective layers 105 and 106, the adhesive layer 107, and the reflective layer 103 are set in a practical range, the warpage amount θ of the optical disc 100 is set within the range of ± 0.3 ° described above. Optical disc 1 required for
In order to realize the lower limit of 1.19 mm of the total thickness t of 00, the thickness t1 of the substrates 101 and 102 may be set to 0.58 mm or more.

Further, the optical disc 1 configured as described above
00, the substrates 101 and 102 have flexibility, but the optical disc 100 as a whole has substrates 101 and 102.
By bonding the first and second information recording members 111 and 112, each of which includes as a constituent element, the substrates 101 and 102 have a property of higher rigidity, that is, inflexibility. Further, the warp amount θ is within the range of ± 0.3 ° as described above for the optical disc 100 as a whole, but the warp amount at the same rotation number exceeds the range of ± 0.3 ° for the substrates 101 and 102 alone. .

By the way, if the thickness t1 of the substrates 101 and 102 (hereinafter referred to as the substrate thickness) is made too large, the total thickness t of the optical disc 100 becomes large, so that the warp amount θ.
However, the window margin at the time of performing data identification by the signal processing circuit 215 shown in FIG. 3 is reduced, and the error rate of the compressed moving image information input to the MPEG2 decoder / controller 217 is increased.
Therefore, in the present invention, the upper limit of the substrate thickness t1 is set to 0.64 mm as described above. The reason for this will be described below.

FIG. 10 shows the substrate 10 of the optical disc 100.
FIG. 3 is a diagram for explaining the shape of pits formed on the first and second parts. As shown in FIG. 10, the shape of the pit 10 approximates a so-called soccer stadium shape with a trapezoidal cross section. The inner wall 11 of the pit 10 is a downward slope, and the bottom 12 is substantially flat. 13 is a cross section of the pit 10 in the radial direction of the optical disc (track width direction), 14 is a cross section of the optical disc in the circumferential direction (track direction), Wm is the dimension of the upper part of the pit 10 in the track width direction (upper width), and Wi is The dimension of the bottom of the pit 10 in the track width direction (bottom width), hm is the depth of the pit 10, and Zm is the length of the pit 10 in the track direction. This pit 1
The shape of 0 is reflected in the surface shape on the reflective layers 103 and 104.

FIG. 11 is a diagram showing a reproduction signal obtained from the optical disc 100 by the optical disc apparatus shown in FIG. 3, which is obtained by computer simulation using a known diffraction model.

The parameters relating to the optical disk device are: laser wavelength λ: 650 nm, numerical aperture NA of the objective lens: 0.6, beam filling rate in the disk radial direction: 0.58, beam filling rate in the disk circumferential direction: 0. 31 and parameters relating to the optical disc 100 are: substrate refractive index n: 1.58 substrate thickness t1: 0.6 mm track pitch Tp: 0.72 μm detection window width (window width) Tw: 0.12 μm Pit top width Wm: 0.35 μm, pit bottom width Wi: 0.20 μm, pit depth hm: 0.2 (λ / n).

These parameters are used for the optical disc 100.
The information recorded above includes RLL (Run Length
It is assumed that the modulation code of (d, k) = (3, 17) system of the limited modulation code and the code rate (m / n) = 4/9 is used. This corresponds to a recording density for recording 4.5 GB of information on one side of the optical disc 100.

FIG. 11 shows the change of the reproduction signal in the range where the pit edge position is ± 0.5 Tw when reproduction is performed from the optical disc 100 in which the pit length is recorded by using the above modulation code. A reproduction signal pattern (pit pattern) that can be generated corresponding to a range of pit edge positions of ± 10 Tw under the constraint of run length in the modulation code is as shown in the center position (light beam position is Tw = 0. There are 100 signals each of which rises (a signal that rises to the right in the figure) and signals that fall (a signal that falls to the left in the figure) corresponding to the pitch edge. In FIG. 11, these 10
The reproduced signals of 0 ways are overlapped and drawn. In addition, there are four types of cases where there are no pits on both sides adjacent to the focused track on which the light beam is focused, there is a long pit, there is a long pit start end, and there is a long pit end end. Also, the reproduced signal is drawn in layers. Further, in FIG. 11, the disk inclination angle φ described in FIG.
An example in the case of rad is shown. When designing a practical optical disk device in consideration of mass productivity, it is necessary to allow the disk inclination angle φ to be about 10 mrad.
In this case, in the present invention, the warpage amount θ when the optical disc 100 is rotated at a predetermined rotation speed (1350 rpm) is ± 0.3 °.
By limiting within (about ± 5.24 mrad),
The requirements for the accuracy of the mounting angle of the optical head are alleviated.

FIG. 11 shows the reproduced signal waveform after further signal processing by the waveform equalization circuit. FIG.
2 is a diagram showing a configuration example of a waveform equalizing circuit included in the signal processing circuit 215 in FIG. 3, which is a transformer including a delay circuit 20, multipliers 30 to 34 for weighted addition, and an adder 35. This is a Versal filter type waveform equalization circuit. The reproduction signal Si from the amplifier array 213 in FIG.
First, it is input to the delay circuit 20. The delay circuit 20 has a plurality of stages, in this example, four unit delay elements 21, 22, 23,
24 are connected in cascade, and a plurality of taps T0,
It has T1, T2, T3, and T4. When the input reproduction signal Si is an analog signal, the delay circuit 20 is composed of a delay element, a delay line for analog signals such as a CCD, or the like. The unit delay elements 21 and 24 have a delay time of τ2, and the unit delay elements 22 and 23 have a delay time of τ1. The unit delay elements 21, 22, 23 and 24 have adjacent taps T0 and T
Since it is located between 1, T2, T3, and T4, its delay time (that is, the delay time between adjacent taps) is called a tap interval. Note that generally, τ1 = τ2 = τ is selected.

The output signals from the taps T0, T1, T2, T3 and T4 are multiplied by multipliers 30, 31, 32, 33 and 34.
By a. (-F2), a. (-F1), a.
{1 + 2 (f1 + f2)}, a · (−f1), a · (−
After being multiplied by a coefficient f2) (this is referred to as a tap coefficient), they are added up by the adder 35 to obtain a waveform equalized output signal So. However, a is a constant other than 0 and may be positive or negative. The center tap T3
The tap coefficient by which the output signal from (main tap) is multiplied is such that the sum of the tap coefficients by which the output signals from all the taps T0, T1, T2, T3, and T4 are multiplied is a. It is selected as {1 + 2 (f1 + f2)}. This is because when the input signal (reproduced signal Si) of the waveform equalization circuit is direct current, the output signal So also becomes direct current and the waveform equalization circuit can be regarded as a direct current amplifier having an amplification factor a.

In this case, the tap T at the center of the delay circuit 20
Multiplier 32 connected to the output signal from 2 (main tap)
Considering the signal passing through as the main component, the waveform equalization circuit of FIG. 12 outputs signals from the taps T0, T1, T3, and T4,
That is, before and after the output signal from the main tap T2 ± τ1, ±
By adding a signal obtained by multiplying the signal of (τ1 + τ2) by a tap coefficient different from the tap coefficient for the output signal from the main tap T2, as a correction amount for the main component,
It can be considered that waveform equalization of the reproduction signal Si is performed. In this way, the taps T before and after the main tap T2 are
The reason for multiplying the output signals from 0, T1, T3, and T4 by tap coefficients having symmetrical values is that the mark shape on the optical disc 100 and the shape of the light beam from the optical head are symmetrical in the front-back direction (track direction). That is, there is symmetry in the time axis direction. If there is no such symmetry,
Correspondingly, it may be possible to expect better characteristics by breaking the symmetry of the tap coefficient in the waveform equalization circuit.

By equalizing the waveform of the reproduced signal using such a waveform equalizing circuit, the window margin shown below can be expanded. In this case, the total delay time of the waveform equalization circuit τ1 + τ2 + τ3 + τ4 = 4Tw, 5
The ratio of one tap coefficient is −f2: −f1: {1 + 2 × (f
1 + f2)}:-f1: -f2, f1 = 0.04
5, f2 = 0.03. The preferable ranges of f1 and f2 are 0.01 ≦ f1 ≦ 0.05 and 0.01 ≦ f2 ≦
0.04 or 0.03 ≦ f1 ≦ 0.07, 0.01
5 ≦ f2 ≦ 0.04.

By creating a diagram as shown in FIG. 11 by computer simulation, it is possible to discuss the margin under adverse conditions in the range where the operation should be guaranteed. In this calculation, although the principle model is well known from the past, it is necessary to comprehensively perform a large amount of calculation under various conditions as described above, and it is necessary to discuss for the first time with such calculation. It is possible.

As shown in FIG. 11, the reproduced signals are grouped into three groups for both the rising signal and the falling signal. These three groups are, in order from the top, signals when there are no pits in the patterns of both adjacent tracks, when there is a pit start or end, and when there are long pits. When the patterns of both adjacent tracks are other than these, the signal waveform is obtained by filling the space between them.

The range of ± 0.5 Tw on the horizontal axis of FIG. 11 corresponds to the detection window width (window width) when the data identification circuit in the signal processing circuit 215 shown in FIG. 3 performs data identification. If the rising position or the falling position of the reproduction signal input from the waveform equalization circuit is out of this range, the data identification circuit cannot correctly identify the data and an error occurs. Therefore, when a certain threshold value is set for the X-shaped reproduction signal group in FIG. 11, correct reproduction cannot be performed unless the position where the reproduction signal crosses the threshold value is included within the detection window width. The width of the change range of the position where the reproduction signal crosses the threshold value corresponds to jitter, and a value obtained by dividing this by the detection window width Tw is an amount called a window occupancy rate, which is usually displayed in%. A value obtained by subtracting the window occupancy rate from 100% is called a window margin. In this calculation, the influences of intersymbol interference, crosstalk, disc tilt, etc. are taken into consideration, but other laser noise, electric system noise such as electronic circuits, and medium noise are not taken into consideration. In the system design, it is necessary to secure a certain value or more, specifically, 10% or more as the window margin in order to correctly reproduce even if these influences occur.

For example, as in this embodiment, the pit length corresponding to the window width Tw = 0.12 μm = 0.12 μm
From the optical disc 100 on which information is recorded at high density
= 650 nm and NA = 0.6, when reproducing information through an optical system, the fluctuation (jitter) of the pit edge position is much larger than that of the CD, and the window width Tw is much larger than that of the CD. Small. Therefore, in consideration of all the laser noise, electrical system noise and other signal deterioration factors, the window margin is set to 10% or more in order to realize the error rate of the reproduction signal from the optical disc 100 of 10 ⁻⁴ or less. It was confirmed experimentally that there is a need.

Here, as described above, the substrate thickness t1 should be made large in order to reduce the warp amount θ of the optical disc 100, but a window margin of 10% is secured as to how thick the substrate thickness t1 can be made. It depends on whether or not. That is, the upper limit of the substrate thickness t1 is allowed up to the range where the window margin is 10% or more.

FIG. 13 is a diagram showing the dependence of the window margin on the substrate thickness. Basically, the same simulation calculation as in FIG. 11 is obtained by changing the substrate thickness t1 and repeatedly calculating as shown in FIG. In this case, the tap coefficient of the waveform equalization circuit shown in FIG. 12 is optimized for each calculation. As is clear from FIG. 13, in order to secure a window margin of 10% or more, the substrate thickness t needs to be suppressed to 0.64 mm or less.
This has been clarified for the first time by the systematic analysis by the present inventors in consideration of the various signal deterioration factors and the effects of the waveform equalization circuit described above. In this case, the upper limit of the total thickness t of the optical disc 100 is 1.32 mm.

The reason why the window margin decreases when the substrate thickness t1 is increased as described above is that the aberration of the light beams generated on the substrates 101 and 102 due to the disc tilt of the optical disc 100 as the substrate thickness t1 is increased. By increasing. That is, when the aberration of the light beam becomes large, the spot diameter of the reproducing light beam focused on the reflection layers 103 and 104 of the optical disc 100 widens and the side lobe becomes large. This is because the amount of reproduction signal leakage between tracks increases.

Optical discs 100 having various substrate refractive indices n and substrate thicknesses t1 are used for an ideal objective lens having a refractive index of 1.58 and a thickness of 0.6 mm and having completely corrected aberrations. The rms value of the aberration when used was calculated using a geometric model. The calculation procedure is as follows.

First, the focal point of paraxial rays is set as a reference,
The increase or decrease in the optical path length from the objective lens aperture pupil plane to the reference point, that is, the wavefront aberration is obtained as a function of the coordinates of the aperture pupil plane.
The wavefront aberration thus obtained includes a component due to the defocus of the reproduction light beam, but since the defocus is removed by the focus control, the component is subtracted and the root mean square value of the residual is obtained as the rms value. . As a specific process for removing the defocus component, the best-fit spherical surface for the equiphase surface is obtained by the least square method,
Numerical calculations were performed to find the root mean square of the residuals as the rms value.

FIG. 15 is a diagram showing the result of this calculation.
The substrate refractive index n is plotted on the abscissa and the substrate thickness t1 is plotted on the ordinate, and the rms value of the aberration at each point on the coordinate plane is displayed in contour lines. The unit is 100 of laser wavelength λ (= 650 nm).
It is 1/0. In FIG. 15, the triple circle is the point of the load specification of the objective lens, and the aberration is 0 here. The substrate refractive index n is n = 1.58 when the materials of the substrates 101 and 102 are polycarbonate, and n = 1.58 when PMMA is used.
It is about 1.49. From these results, it is understood that the substrate thickness t1 should be increased when the substrate refractive index n becomes smaller than the lens load specification.

A region surrounded by a thick solid line in FIG. 15 is a range defined by the optical disc of the present invention, the substrate refractive index n is selected in the range of 1.45 to 1.65, and the substrate thickness t.
As described above, 1 is selected in the range of 0.58 mm or more and 0.64 mm or less. The present invention is not limited to the embodiments of the present invention described above, and it goes without saying that various modifications can be made without departing from the scope of the present invention.

[0066]

According to the present invention, the following effects can be obtained. As described above, according to the present invention, the error rate due to the optical disc itself is suppressed to 10 ⁻⁴ or less by defining the warp amount of the entire optical disc at a predetermined rotation speed, the total thickness of the optical disc, and the substrate thickness. It becomes possible.

Therefore, according to the present invention, the compressed moving picture information recorded according to the MPEG2 standard is subjected to an error rate reduction effect by signal processing such as waveform equalization and error correction, and up to an error rate of 10 ^-20 which is practically required. It is possible to provide an optical disc and an optical disc device that can be lowered and input to the MPEG decoder.

[Brief description of drawings]

FIG. 1 is a perspective view and a sectional view of an optical disc according to an embodiment of the present invention.

FIG. 2 is a modification of the optical disc shown in FIG.

FIG. 3 is a block diagram showing a configuration of an optical disc device.

FIG. 4 is an explanatory diagram of a warp of an optical disc.

FIG. 5 is an explanatory diagram of an optical disc tilt.

FIG. 6 is a diagram showing a relationship between a warp amount in a radial direction and a circumference of an optical disc and an error rate caused by the optical disc.

FIG. 7 is a diagram showing the relationship between the total thickness of an optical disc and the amount of warpage.

FIG. 8 is an explanatory diagram of a diameter of each part of the optical disc.

FIG. 9 is an explanatory diagram of the thickness of each part of the optical disc.

FIG. 10 is a diagram for explaining a pit shape on an optical disc.

FIG. 11 is a diagram showing a relationship between a light beam position on an optical disc and a reproduction signal.

12 is a diagram showing the configuration of a waveform equalization circuit included in the signal processing circuit in FIG.

FIG. 13 is a diagram showing a relationship between a substrate thickness of an optical disc and a window margin.

FIG. 14 is a diagram showing calculation results of a window occupancy rate and a window margin with respect to a substrate thickness of an optical disc.

FIG. 15 is a diagram showing the relationship between the refractive index and the thickness of the substrate of an optical disc, using the rms value of aberration as a parameter.

[Explanation of symbols]

 100 ... Optical disc 101, 102 ... Translucent substrate 103, 104 ... Reflective layer 105, 106 ... Protective layer 107 ... Adhesive layer 108 ... Clamping hole 109 ... Clamping zone 111 ... First information recording member 112 ... Second Information recording member 200 ... Cartridge 201 ... Spindle motor 202 ... Spindle motor drive circuit 203 ... Objective lens 204 ... Focus coil 205 ... Tracking coil 206 ... LD driver 207 ... LD (semiconductor laser) 208 ... Collimating lens 209 ... Polarizing beam splitter 210 Condensing lens 211 Cylindrical lens 212 Photodetector 213 Amplifier array 214 Servo controller 215 Signal processing circuit 216 Disk controller 217 MPEG2 decoder / controller 21 ... video signal generating circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mishi Okubo 70 Yanagicho, Sachi-ku, Kawasaki-shi, Kanagawa Toshiba Yanagimachi factory

Claims (19)

[Claims] 1. A disc-shaped first light-transmissive substrate, a reflective layer provided on the first light-transmissive substrate, and a protective layer provided on the reflective layer. A first member for recording desired information, an adhesive layer having a first surface and a second surface adhered to the protective layer, and at least a second transparent substrate adhered to the first surface of the adhesive layer An optical disc having a thickness of 1.19 mm or more. 2. The amount of warpage during rotation at a predetermined number of revolutions is ± 0.
The optical disc according to claim 1, wherein the optical disc is within 3 °. 3. The optical disc according to claim 1, wherein the thickness of the optical disc is 1.32 mm or less. 4. A disk-shaped first light-transmissive substrate, a reflective layer provided on the first light-transmissive substrate, and a protective layer provided on the reflective layer, A first member for recording desired information, an adhesive layer having a first surface and a second surface adhered to the protective layer, and at least a second transparent substrate adhered to the first surface of the adhesive layer A second member having a thickness of 0.58 mm of the first and second light transmissive substrates.
As described above, the optical disc is 0.64 mm or less. 5. A disc-shaped first light-transmissive substrate, a reflective layer provided on the first light-transmissive substrate, and a protective layer provided on the reflective layer, A first member for recording desired information, an adhesive layer having a first surface and a second surface adhered to the protective layer, and at least a second transparent substrate adhered to the first surface of the adhesive layer And a second member having a warp amount when rotating at a predetermined number of revolutions.
An optical disk characterized by being within 0.3 °. 6. The optical disc according to claim 5, wherein the predetermined rotation speed is 1350 rpm. 7. The second member further includes a reflective layer provided on the second light transmissive substrate and a protective layer provided on the reflective layer, and desired information is provided. 6. The optical disc according to claim 1, wherein the optical disc is recorded. 8. The diameter of at least the first light transmissive substrate is 119.7 mm or more and 120.3 mm or less, according to any one of claims 1, 4 and 5. The described optical disc. 9. The method according to claim 1, wherein at least the first light-transmissive substrate is made of a material having a refractive index of 1.45 or more and 1.65 or less. The optical disc according to item 1. 10. The material of at least the first light-transmissive substrate is polycarbonate, a resin containing polycarbonate, or PMMA, according to any one of claims 1, 4 and 5. An optical disc according to item. 11. The optical disc according to claim 1, wherein the adhesive layer is made of a hot melt adhesive. 12. The optical disk according to claim 1, wherein the reflective layer is made of an aluminum film. 13. The optical disc according to claim 1, wherein the protective layer is made of a photocurable resin. 14. The method according to claim 1, wherein at least the first light-transmissive substrate is flexible, and the optical disc is higher in rigidity than the first light-transmissive substrate.
Alternatively, the optical disc according to claim 5. 15. The warp amount of at least the first light-transmissive substrate during rotation at the predetermined number of rotations exceeds a range of ± 0.3 °. The optical disc according to claim 5. 16. A disk-shaped first light-transmissive substrate,
A first member having a reflective layer provided on the first light-transmissive substrate and a protective layer provided on the reflective layer, for recording desired information; a first surface; An adhesive layer having a second surface adhered to the protective layer, and a second member having at least a second transparent substrate adhered to the first surface of the adhesive layer, and at least the first light transmission. The warp amount of the flexible substrate when rotating at the predetermined rotation number exceeds a range of ± 0.3 °, and the warp amount of the optical disc when rotating at the predetermined rotation number is within ± 0.3 °. Optical disc. 17. The optical disk according to claim 5, a rotation driving means for rotating the optical disk at a predetermined rotation speed, a light irradiating means for irradiating the optical disk with a light beam through an objective lens, and the light irradiating means. The light detecting means for detecting the reflected light of the light beam applied to the optical disc, the signal reproducing means for obtaining the reproduction signal corresponding to the information recorded on the optical disc from the output signal of the light detecting means, and the reproducing means. An information restoration means for restoring the information recorded on the optical disc from the obtained reproduction signal, wherein the inclination angle of the optical disc with respect to the light beam includes the amount of warpage when the optical disc is rotated at the predetermined number of revolutions. An optical disk device characterized by being 10 mrad or less. 18. The signal reproducing means includes data identifying means for identifying data of the reproduced signal after being equalized by the waveform equalizing means, and waveform equalizing means for equalizing the waveform of the reproduced signal. The information restoration means includes error correction means for performing error correction on the data obtained by the data identification means,
18. The optical disc apparatus according to claim 17, further comprising: a decoding unit that decodes the data that has been error-corrected by the error correction unit to restore the information recorded on the optical disc. 19. The numerical aperture of the objective lens is approximately 0.
19. The optical disk device according to claim 17, wherein the wavelength of the light beam is approximately 650 nm.