JP2000011452A - Optical recording medium and optical recording and reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical recording medium consisting of an optical disk which is capable of making its storage capacity to >=8 GB and has a ROM(Read.Only.Memory) in at least part as basic constitution. SOLUTION: A light transparent layer 12 is formed on an information recording surface 11 formed with information recording pits and is irradiated with the laser beam of 635 nm<=λ<=680 nm in wavelength λ through a lens system of >=0.76 in N.A(numerical aperture) from the light transparent layer side, by which the reading out of the information is executed. The thickness (t) of the light transparent layer is specified 3 to 182 μm and the thickness unevenness Δt thereof to within <=±5.26 λ/(N.A)4. The track pitch TO on the information recording surface 11 is specified to 0.45 to 0.57 μm, the shortest pit length Pmin of information recording pits to 0.21 to 0.31 μm, the recording linear density LD to a bit string of <=0.21 μm/bit and the depth D of the information recording pits to 5.7 to 113 nm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium and an optical recording / reproducing apparatus (the optical recording / reproducing apparatus in this specification refers to an apparatus for optically reproducing and / or recording on an optical recording medium). This is intended to increase the recording capacity especially when laser light in the red wavelength range is used.

[0002]

2. Description of the Related Art A disk-type optical recording medium has the advantages of a high-speed access, a small-sized and simple recording / reproducing apparatus. To realize a disk that can be replaced with a current video tape recorder (VTR), a storage capacity of 8 GB (gigabyte) or more is required.

[0003]

SUMMARY OF THE INVENTION According to the present invention, there is provided an optical recording system comprising an optical disk having a ROM (Read Only Memory) part at least in part, the storage capacity of which can be made 8 GB or more. It is a main object of the present invention to provide a medium and an optical recording / reproducing apparatus that performs reproduction and / or recording on the optical recording medium.

[0004]

That is, in the optical recording medium according to the present invention, a light transmitting layer is formed on an information recording surface on which information recording pits are formed.
Emits a laser beam having a wavelength of 635 nm ≦ λ ≦ 680 nm.
A. The information is read out by irradiating through a lens system having a (numerical aperture) of 0.76 or more. The thickness t of the light transmitting layer is set to 3 μm to 182 μm, and the thickness variation Δt is set to ± 5. .26λ / (NA) ⁴ or less.
The track pitch TP of the information recording surface is 0.4
5 μm to 0.57 μm, the shortest pit length P _min of the information recording pit is 0.21 μm to 0.31 μm, the recording linear density LD is a pit row of 0.21 μm / bit or less, and the depth of the information recording pit is D is 57 nm to 113 nm
And

An optical recording / reproducing apparatus according to the present invention uses the above-described optical recording medium according to the present invention and has a wavelength .lambda.
Laser light having a wavelength of 35 nm ≦ λ ≦ 680 nm was applied to N.I. A.
(Numerical Aperture) A laser beam is made incident on the optical recording medium from the light transmitting layer side through an optical system having a numerical aperture of 0.76 or more to reproduce recorded information on the information recording surface.

With the above configuration, a large storage capacity of 8 GB or more can be realized.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of an optical recording medium according to the present invention is shown in FIG.
The light transmitting layer 12 is formed on the information recording surface 11 in which the information recording pits 13 are formed on one surface.

The substrate 10 is made of, for example, polycarbonate (P
C) is formed by injection molding, and at the same time as the molding, the fine irregularities of the required pattern are transferred from a stamper placed in a molding die.
For example, the information recording pits 13,
Further, a so-called groove is formed.

The thickness of the substrate 10 is, for example, 0.3 mm or more, which allows injection molding, and can be selected to be less than 1.2 mm, which corresponds to the thickness of a substrate in a CD or the like.

The optical recording medium M having this configuration is
From the light transmitting layer 12 side, the wavelength λ is 635 nm ≦ λ ≦
A mode in which a laser beam of 680 nm is incident is adopted. In this case, the laser beam is A. (Numerical Aperture) Irradiation through a lens system of 0.76 or more, for example, reading of information,
That is, reproduction is performed.

The thickness t of the light transmitting layer 12 is 3 μm to 182
μm, and the thickness irregularity Δt is ± 5.26λ / (N.
A. ) ⁴ or less. The track pitch TP of the information recording surface is set to 0.45 μm to 0.57 μm. The shortest pit length P _min of the information recording pit is from 0.21 μm
0.31 μm. The recording linear density LD is 0.21 μm
The pit row is equal to or less than / bit. The depth D of the information recording pit is 57 nm to 113 nm.

The thickness t of the light transmitting layer is preferably 5
0 μm to 120 μm.

The structure of the optical recording medium according to the present invention will be described. DVDs already proposed (Digita
l Versatile Disc or Digital Video Disc), the area within the information signal section, that is, a radius of 24
In the range of mm to 58 mm, the wavelength is 0.65 μm.
m, the numerical aperture (NA) is 0.6, and its storage capacity is 4.7 GB. Therefore, in order to realize a storage capacity of 8 GB based on this, the capacity (in this case, density) is. N. A. , Which is inversely proportional to the wavelength, and which is effective in the square thereof, 8 / 4.7 = {(NA / 0.6) × (0.65 / λ)} ² (1) ).

The laser having a wavelength in the red wavelength range has a wavelength λ of 635 nm ≦ λ ≦ 680 nm, and specifically, has a wavelength λ = 0.
There are laser beams of 635 μm, 0.650 μm, and 0.680 μm. However, considering higher recording density, the laser beam having a shorter wavelength, λ = 0.635 μm, is used. Where λ = 0.635
8 / 4.7 = ｛(NA / 0.6) ×
(0.65 / 0.635)｝ ² ... (1 ₁ ). A. = 0.76.

Λ = 0.635 μm;
A. = 0.76, each track pitch P, shortest pit length P _min , and linear density LD for achieving a recording capacity of 8 GB are 4.74 μm and shortest pit length in a 4.7 GB DVD. Since the track density is 0.40 μm and the line density is 0.267 μm / bit, TP = 0.74 / ８ (8/4) in consideration of both the line direction and the width direction of the track and on the assumption that the modulation method is EFM. .7) = 0.57 μm P _min = 0.40 / √ (8 / 4.7) = 0.31 μm LD = 0.267 / √ (8 / 4.7) = 0.21 μm /
bit.

As will be described later, the lens system has a two-group lens structure, so that A. = 0.95
Since until it practical extent, from (1 ₁₎ of the relationship, TP = 0.74 / (0.95 / 0.6 × 0.65 / 0.635) = 0.45μm P min = 0.40 / (0.95 / 0.6 × 0.65 / 0.635) = 0.24 μm LD = 0.267 / (0.95 / 0.6 × 0.65 / 0.635) = 0.16 μm / bit In the present invention, the track pitch TP is
0.45μm ~ 0.57μm, the shortest pit length P
_min to 0.24 μm to 0.31 μm, and the recording linear density L
D is a pit row of 0.21 μm / bit or less. And here, the modulation method for the optical disk includes
There are an EFM (2-7) system and a 1-7 system modulation system. The ratio of the shortest pit length: channel bit length: signal bit length in each system is 3: 1: 2 in the EFM system, and 1: 1. -7
It is 4: 2: 3 in the system. From this relationship, the shortest pit length is reduced to 8/9 when the 1-7 system is used for the same density.
When this is multiplied, the shortest pit length becomes 0.21 μm.

On the other hand, when the pit depth D is the deepest,
The modulation degree is maximized at ４ of the wavelength λ.
Since the push-pull signal in the well-known push-pull method is maximized, it is required to be within these ranges. Therefore, the above-described red laser has a long wavelength of 680 nm and a short wavelength of 635 nm. If the refractive index n is 1.5, 680/4 / 1.5 = 113 nm and 635/8 / 1.5 = 57 nm. That is, in the present invention, the pit depth D is
57 nm to 113 nm.

On the other hand, the tolerance (skew margin) SM of the inclination of the optical recording medium with respect to the optical axis of the irradiation laser beam has a relationship of SM∝λ / (NA) ³ / t. A. If you increase
It is necessary to reduce the thickness t of the light transmitting layer 12 through which the laser light traveling toward the information recording surface 11 is transmitted.
The skew margin SM is known from JP-A-3-225650 as long as it has a relationship of SM ≦ ± 84.115 ° (λ / (NA) ³ / t). .

This can be applied to the optical recording medium of the present invention, and it is appropriate that this SM is 0.4 ° as a specific limit value. Now, SM =
0.4 ° to shorten the wavelength of the laser, A. To what extent the thickness of the light transmitting layer should be set by the conversion, A. Is 0.76 or more from the above. Further, considering the compatibility with λ = 0.38 μm of a shorter wavelength blue-violet laser as the laser light, A.
If the condition of ≧ 0.76 is not changed, the thickness t of the light transmitting layer is t = 182 μm.

On the other hand, the lower limit of the thickness of the light transmitting layer is determined by whether or not the protective function of the light transmitting layer, which also has a role of protecting the recording film and the reflective film, is secured. That is, the reliability of the optical recording medium and the high N.I. A. It is necessary that the thickness be 3 μm or more in consideration of the influence of the collision of the lens with the light transmitting layer and the light transmitting layer surface due to the approach of the lens. Therefore, in the present invention, the thickness t of the light transmitting layer is set to 3 μm to 182 μm.

Also, high accuracy is required for the thickness unevenness of the light transmitting layer. When the thickness of the light transmitting layer deviates from the design center of the reproduction objective lens, the amount of aberration given to the laser beam spot by the thickness unevenness is determined by N.I. A. And is proportional to the wavelength λ. Therefore, high N.I. A. In order to increase the recording density by reducing the wavelength or shortening the wavelength, the thickness unevenness of the light transmitting layer is more severely limited. As a specific system example, in the case of a CD, the N.V. A. = 0.45 has been put to practical use, and the standard for the thickness unevenness of the light transmitting layer (substrate in the case of CD) is ± 100 μm. In the case of DVD, N.V. A. = 0.6 and ± 30 μm. On the basis of the permissible amount ± 100 μm in CD, the thickness unevenness Δt is expressed by the following equation. Δt = ± (0.45 / NA) ⁴ × (λ / 0.78) × 100 = ± 5.26 × (λ / (NA) ⁴ ) μm

Further, in increasing the capacity of the above-mentioned optical recording medium, N.I. A. = 0.85, the thickness t of the light transmitting layer is 0.6 × (0.6
/0.85) ³ = 0.21 mm or less. Further, in consideration of compatibility with a blue-violet laser having a wavelength of about 400 nm, 0.21 × 0.4 / 0.65 = 0.129 mm, and the thickness t of the light transmitting layer should be 0.12 mm or less. become.

In order to actually form the light transmitting layer 12, for example, application of a resin and adhesion of a resin sheet are considered. In addition, there is a problem that the outermost peripheral portion is raised by spin-coating the resin. Therefore, as shown in a schematic cross-sectional view of another embodiment in FIG. 2, it is considered that an effective method is to form a transparent resin sheet 14 by bonding it with a transparent adhesive layer 15, but in this case, When the thickness of the resin sheet is less than 50 μm, the birefringence is large and the signal characteristics are affected.
It is preferably at least 0 μm. In addition, the thickness t of the light transmitting layer may be 50 μm or more from the viewpoint of the adhesion of dust on the light transmitting layer, the influence on the recording / reproducing laser light spot due to the generation of scratches, and the instability of the servo due to this. preferable.

From the above, the thickness t of the light transmitting layer is:
It is more preferable that the thickness be 50 μm to 120 μm.

Further, the structure of the optical recording medium according to the present invention will be described. The above-mentioned row of pits P in the optical recording medium according to the present invention is shown in FIG. As shown in FIG. 3B, a configuration formed on a single or one spiral wire,
In the illustrated example, a plurality of spiral lines may be formed.

Further, as shown in a schematic pattern diagram in FIG. 4, a structure in which a recordable area 40 indicated by hatching is provided in an area of the information recording surface 11 other than the area where the information pits P are formed. You can also. This recordable area 40 is
As in the case of the pit row described above, a single or multiple spirals can be used.

A plurality of double spirals (2
In the case of a configuration such as a book (parallel spiral), a spiral groove is formed, and a recordable area is formed in each of the so-called lands within the groove and between the grooves. A configuration such as forming P can be adopted.

Further, as shown in a schematic pattern diagram of FIG. 5A, a spiral groove Grv shown by hatching.
And the pit row P is formed on each extension of the groove Grv and the land Lnd between the grooves, or as shown in FIGS. 5B and C, the groove Grv and the land Lnd are continuous. Various configurations can be adopted, such as a configuration in which the pits P are formed on the extension of the configuration.

Although the configuration of FIG. 1 shows a case where the information recording surface 11 has a single layer, a configuration in which two or more layers are stacked as shown in FIG. 6 can be adopted. In the example shown in FIG. 6, the first and second information recording surfaces 11 (11A and 1A)
1B) is a transparent intermediate layer 1 made of, for example, an ultraviolet curable resin.
This is a case where the layers are formed with the layers 6 interposed therebetween. Thus, in the case of a laminated structure of two or more layers, for example, the first information recording surface 1
1A can be an information recording surface with a pit row, and the second information recording surface 11B can be an information recording surface with a recordable area.

In this case, the thickness t of the light transmitting layer with respect to the second information recording surface is the sum of the intermediate layer 16 and the light transmitting layer 12 on the surface.

When the information recording surface 11A having a pit array and the information recording surface 11B constituting a recordable area are laminated as described above, the information recording surface 11A having the pit array is irradiated with a laser beam. It is preferable to arrange on the incident side.

A reflective film is formed on the information recording surface 11A having a ROM configuration of pit rows. When the information recording surface 11A is arranged on the laser light incident side, the reflective film is made translucent. Also,
Information recording surface 11B having an information layer having a recordable area
Is rewritable or one-time writing, so-called W
In the case of a so-called phase change type by a recording mode in which optical characteristics change due to a change between polycrystallization and amorphous by laser irradiation, a phase change material layer is formed. Become composed. Also, if necessary, the base 10 on which the second information recording surface 11B is formed
A reflective film can be formed on the surface on which the information layer, for example, the phase change material layer is formed, for example, on the groove and land surfaces.

The information recording surface 11 having a pit row
A and the information recording surface 11B having a recordable area are stacked, as described above, it is preferable to dispose the information recording surface 11A having a pit row on the laser beam incidence side, as described above. In general, the power of laser light for reading information by pits is smaller than the power of laser light in optical recording or reproduction by phase change recording, for example. In the case of performing the light irradiation on the information recording surface 11A for performing reproduction by transmitting only the light transmitting layer on the front surface side, the reading of the information from the information recording surface 11B can be avoided when the power of the laser beam is small.
/ N can be reproduced.

An optical recording / reproducing apparatus according to the present invention is an optical recording / reproducing apparatus for optically performing reproduction and / or recording on the optical recording medium M, for example, an optical disk. As shown in the configuration diagram of the main part of an example, the wavelength λ is 635 nm ≦ λ ≦ 680 nm.
And a laser light source unit (not shown) for obtaining the laser light L. A. (Numerical aperture) 0.76
Through the above optical system, that is, the objective lens, the light is incident from the light transmitting layer 12 side in a direction orthogonal to, for example, the optical recording medium M that is driven to rotate, and the recorded information on the information recording surface is reproduced or / and reproduced. And record.

In this case, the optical system can be constituted by the two-group lens systems 31 and 32. A. Can be obtained.
These lens systems 31 and 32 have lens surfaces 31a and 31b, 32a and 3
Not only a single lens having 2b but also a lens group including a plurality of lenses can be formed.

The second lens system 3 in this optical system
2 and 33 can be configured so that the distance between them can be changed and adjusted. As described above, the variable configuration can cancel the wavefront aberration caused by the change in the thickness of the light transmitting layer, thereby simplifying the design and manufacturing of the optical recording medium and the optical recording / reproducing apparatus, and improving the recording / reproducing. It is possible to stabilize reproduction and improve characteristics.

As described above, according to the present invention, in particular, in an optical recording medium which performs reproduction and / or recording with laser light in the red wavelength range, the skew margin is set to, for example, 8 GB while keeping the skew margin to the extent of DVD.
An optical recording medium capable of large-capacity recording and an optical recording apparatus for reproducing and / or recording the same can be constructed.

In the above-described optical recording medium, one or more information recording surfaces are formed on one surface of the substrate 10. In this manner, two optical recording media each having an information recording surface are formed. By laminating the substrate 10 on the side opposite to the side on which each information recording surface is formed, a double-sided optical recording medium can be formed. The optical recording medium and the optical recording / reproducing apparatus according to the present invention can be variously modified and modified so that the recording surface is irradiated with laser light.

In the present specification, the terms “transparent” and “light-transmitting” mean, of course, those having transparency to the laser light used.

[0040]

As described above, according to the present invention, especially in an optical recording medium for reproducing and / or recording with laser light in the red wavelength range, the skew margin is kept at, for example, 8 G, while keeping the skew margin to the extent of DVD.
An optical recording medium B capable of large-capacity recording and an optical recording apparatus for reproducing and / or recording the same can be constructed.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an example of an optical recording medium according to the present invention.

FIG. 2 is a schematic sectional view of another example of the optical recording medium according to the present invention.

FIGS. 3A and 3B are pit train patterns of an example of an optical recording medium according to the present invention.

FIG. 4 is a pattern diagram of a pit row in an example of an optical recording medium according to the present invention.

FIG. 5 is a pattern diagram of a pit row in an example of an optical recording medium according to the present invention.

FIG. 6 is a schematic sectional view of another example of the optical recording medium according to the present invention.

FIG. 7 is a configuration diagram of a main part of an example of an optical recording / reproducing apparatus according to the present invention.

[Explanation of symbols]

M: optical recording medium, 10: base, 11, 11A,
11B: information recording surface; 12: light transmitting layer;
..Information recording pit, 31... First lens, 32.
..Second lens, 31a, 31b, 32a, 32b
..Lens surface, 40 ... recordable area, P ... pit

Claims (14)

[Claims] 1. A light transmitting layer is formed on an information recording surface on which information recording pits are formed, and a wavelength λ from the light transmitting layer side.
Emits a laser beam having a wavelength of 635 nm ≦ λ ≦ 680 nm.
A. (Numerical Aperture) The information is read out by irradiating through a lens system with a numerical aperture of 0.76 or more. In the signal information area, the thickness of the light transmitting layer is 3 μm to 182 μm, and the thickness of the light transmitting layer is The irregularity is ± 5.26λ / (N.
A. ⁴ ) or less, and the track pitch of the information recording surface is 0.45 μm or more.
0.57 μm, and the shortest pit length of the information recording pit is 0.21 μm to
An optical recording medium comprising: 0.31 μm; a pit row having a recording linear density of 0.21 μm / bit or less; and a depth of the information recording pit being 57 nm to 113 nm. 2. The optical recording medium according to claim 1, wherein said pit row is formed of one or more spirals. 3. The thickness of the light transmitting layer is 50 μm to 12 μm.
2. The optical recording medium according to claim 1, wherein the optical recording medium has a thickness of 0 μm. 4. The optical recording medium according to claim 1, wherein the information recording surface is formed by laminating two or more layers. 5. The optical recording medium according to claim 1, wherein a recordable area is provided in an area of the information recording surface other than a part where the information pit is formed. 6. The optical recording medium according to claim 5, wherein said recordable area comprises one or more spirals. 7. The optical recording medium according to claim 1, wherein an information recording surface having the information recording pits and an information recording surface having a recordable area are provided in a stacked manner. 8. The optical recording apparatus according to claim 8, wherein the information recording surface having the pit rows is arranged on the laser beam incident side of the information recording surface having the recordable area. Medium. 9. A light transmitting layer is formed on an information recording surface on which information recording pits are formed, and the thickness of the light transmitting layer is 3 μm.
182 μm, and the thickness unevenness of the light transmitting layer is ±
5.26λ / (NA) ⁴ or less, the track pitch of the information recording surface is 0.45 μm to 0.57 μm, and the shortest pit length of the information recording pit is 0.21 μm.
μm to 0.31 μm, and the recording linear density is 0.21 μm.
A laser beam having a wavelength λ of 635 nm ≦ λ ≦ 680 nm is applied to an optical recording medium having a pit row of not more than m / bit and the information recording pit having a depth of 57 nm to 113 nm. A. (Numerical aperture) An optical recording / reproducing apparatus characterized in that it is made incident on the optical recording medium from the side of the light transmitting layer through an optical system having a numerical aperture of 0.76 or more to reproduce recorded information on the information recording surface. . 10. A light transmitting layer is formed on an information recording surface having information recording pits and a recordable area, the light transmitting layer has a thickness of 3 μm to 182 μm, and the light transmitting layer has an uneven thickness. Is set to ± 5.26λ / (NA) ⁴ or less,
The information recording surface has a track pitch of 0.45 μm or more.
0.57 μm, the shortest pit length of the information recording pits is 0.21 μm to 0.31 μm, the recording linear density is a pit row of 0.21 μm / bit or less, and the depth of the information recording pits is Uses an optical recording medium having a wavelength of 57 nm to 113 nm, and emits a laser beam having a wavelength λ of 635 nm ≦ λ ≦ 680 nm. A. (Numerical Aperture) Optical recording characterized by being made incident on the optical recording medium from the light transmitting layer side through an optical system having a numerical aperture of 0.76 or more to reproduce and record information recorded on the information recording surface. Playback device. 11. An optical recording / reproducing apparatus according to claim 9, wherein said optical system is a two-group lens system. 12. The optical recording / reproducing apparatus according to claim 11, wherein the two-unit lens system has a variable lens spacing. 13. The optical recording / reproducing apparatus according to claim 10, wherein said optical system is a two-group lens system. 14. The optical recording / reproducing apparatus according to claim 10, wherein the two-unit lens system has a variable lens spacing.