JPH11120617A - Optical record medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To permit a high-density recording by allowing an optical record medium to have a first signal recording layer whose thickness of a light transmission layer is made to be within a specific range and also to have one or more other signal recording layers. SOLUTION: A first signal recording layer 1 whose thickness of the light transmission layer is 3-177 μm, a DVD format layer 2 and a CD layer 3 are formed in a film form on transparent substrates 4, 5, 6 and this record medium is made to have three-layer structure by sticking these three sheets. Moreover, recordings and reproductions with respect to respective signal recording layers are all performed from the same direction with respective optical systems A, B, C. Since the light transmission layer of the signal recording layer 1 is very thin so that the thickness is 3-177 μm, the layer 1 is reproducable with an optical system having a high NA, for example, when a disk is a disk whose diameter is 120 mm, a capacity of not smaller than 8GB is obtainable. Since, in the signal recording layer 1, ruggedness pits are formed on the transparent substrate 4 and a translucent film is formed on it, a reproducing optical system is a proper system in accordance with the wavelength of a regenerative light using the optical characteristic of the translucent film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called hybrid optical recording medium in which a plurality of signal recording layers are combined.

[0002]

2. Description of the Related Art Optical recording media for optically reading signals are known as recording media for recording audio signals, video signals, and other various information.

As the optical recording medium, various types such as a so-called compact disk, a rewritable magneto-optical disk, and a phase change disk are known, and all of them are formed on a transparent substrate having a thickness of about 1.2 mm. The basic idea is that a recording layer and a reflection layer are formed on a substrate, and recording light and reproduction light are irradiated from the transparent substrate side to perform signal writing and reading.

[0004]

By the way, in the field of optical recording media, the density is rapidly increasing, and the track pitch is narrowed, the recording wavelength of light is shortened, and the shortest pit length is shortened. That, the numerical aperture of the optical system for recording or reproducing information is increased, the information recording layer is overlapped to form a multilayer structure, the disks are bonded together to form a double-sided structure, etc. I have.

[0005] The present invention has been proposed in view of such circumstances, and a novel optical recording medium capable of achieving unprecedented high-density recording and capable of responding to various uses. The purpose is to provide.

[0006]

In order to achieve the above-mentioned object, an optical recording medium of the present invention has a light transmitting layer having a thickness of 3 to 1 mm.
Having a first signal recording layer of 77 μm,
It is characterized by having one or more other signal recording layers.

A signal recording layer having a light transmission layer with a thickness of 3 to 177 μm can cope with a high numerical aperture (high NA) of an optical system, for example, a 8 GB disk with a diameter of 120 mm.
The above capacity can be obtained.

Therefore, the signal recording layer (first signal recording layer) and various signal recording layers, for example, a so-called DVD
By combining a signal recording layer of the format, a signal recording layer of the CD format, and the like, a large-capacity optical recording medium (optical disk) far exceeding the conventional one is realized.

Further, the first signal recording layer and the other signal recording layers can be recorded and reproduced by different independent players, and their applications can be greatly expanded.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an optical recording medium to which the present invention is applied will be described in detail with reference to the drawings.

The optical recording medium of the present invention, for example, an optical disk, has a signal recording layer having a light transmitting layer of 3 to 177 μm in thickness as a first signal recording layer, and various signal recording layers are combined with the signal recording layer. It is a so-called hybrid optical disk.

The signal recording layer to be combined is optional, and may be any of a read-only type, a write-once type, and a rewritable type.
Examples thereof include a combination of uneven pits and a reflective film, a magneto-optical recording layer, a phase-change recording layer, and an organic dye-based recording layer. In addition, the format is arbitrary, and so-called DVD format (DVD, DVD-RAM,
DVD-R, etc.), CD format (CD-ROM, C
Any of known ones such as D-R and CD rewritable can be applied.

FIG. 1 shows an example of a hybrid optical disk in which three types of signal recording layers are combined. In this example, a signal recording layer (hereinafter referred to as an HD signal layer) having a light transmitting layer having a thickness of 3 to 177 μm is shown. 1), a DVD format layer 2 and a CD layer 3.

These signal recording layers are formed on the transparent substrates 4, 5, and 6, respectively, and have a three-layer structure by bonding these three transparent substrates 4, 5, and 6. The recording and reproduction for each signal recording layer is performed by each of the optical systems A, B, and C from the same direction.

Therefore, the light transmitting layer of the HD signal layer 1 is the transparent substrate 4, the light transmitting layer of the DVD format layer 2 is the transparent substrate 4 + the transparent substrate 5, and the light transmitting layer of the CD layer 3 is the transparent substrate 4+
That is, the transparent substrate 5 + the transparent substrate 6.

In this embodiment, the thickness of the transparent substrate 4 (the thickness of the light transmitting layer in the HD signal layer 1) is 3 to 177 μm, and the thickness of the transparent substrate 4 + the transparent substrate 5 (the thickness of the light transmitting layer in the DVD format layer 2). Thickness) is 0.55 to 0.65 mm, and the thickness of the transparent substrate 4 + the transparent substrate 5 + the transparent substrate 6 (total thickness of the light transmitting layer) is 1.1 to 1.3 mm.

The HD layer 1 has a light transmission layer of 3 to 177 μm.
Since it is extremely thin, i.e., m, it is possible to reproduce with an optical system having a high NA. For example, when a disc having a diameter of 120 mm is used, a capacity of 8 GB or more can be obtained.

The HD layer 1 is formed by forming concave and convex pits on the transparent substrate 4 and forming a translucent film thereon. At this time, the optical characteristics of the translucent film depend on the wavelength of the reproduction light to be used. It is preferable to set an appropriate one according to the following. For example, when the generations are conveniently divided according to the practical laser wavelength, the first generation of the reproduction light wavelength of 630 to 680 nm and the reproduction light wavelength of 5
Second generation of 00 to 550 nm, reproduction light wavelength of 400 to 45
Although it is the third generation of 0 nm, the semi-transparent films constituting the HD signal layer 1 and the DVD format layer 2 according to these generations are films satisfying the following optical characteristics.

First generation 10% reflectance in the wavelength range of 630 to 680 nm
(10-40%) and at least 630-790
A translucent film (HD signal layer 1) having a transmittance of 70% or more in nm.

2. The reflectance in the wavelength range of 630 to 680 nm is 10% or more and at least 630 to 790 nm
Translucent film (HD signal layer 1) having a transmittance of 70% or more in a film and a translucent film (DVD having a reflectance of 15% or more at a wavelength of 630 to 680 and a transmittance of 70% or more at a wavelength of 780 nm Combination of format layers 2).

Second generation 10% reflectance in the wavelength range of 500 to 550 nm
A translucent film (HD signal layer 1) having a transmittance of at least 70% at 630 to 790 nm.

2. The reflectance in the wavelength range of 500 to 550 nm is 10% or more and at least 630 to 790 nm
Translucent film (HD signal layer 1) having a transmittance of 70% or more in a film and a translucent film (DVD having a reflectance of 15% or more at a wavelength of 630 to 680 and a transmittance of 70% or more at a wavelength of 780 nm Combination of format layers 2).

Third Generation 10% reflectance in the wavelength range of 400 to 450 nm
A translucent film (HD signal layer 1) having a transmittance of at least 70% at 630 to 790 nm.

2. The reflectance in a wavelength range of 400 to 450 nm is 10% or more and at least 630 to 790 nm.
Translucent film (HD signal layer 1) having a transmittance of 70% or more in a film and a translucent film (DVD having a reflectance of 15% or more at a wavelength of 630 to 680 and a transmittance of 70% or more at a wavelength of 780 nm) Combination of format layers 2).

On the other hand, the DVD format layer 2 and the CD layer 3
Is a signal recording layer having a capacity of 4.7 GB or less. For example, the DVD format layer 2 has a capacity of 2.6 to 4.7 G.
B. The DVD format layer 2 is composed of a translucent film as described above, and the CD layer 3 is composed of a reflective film made of metal.

In the optical disk having the above configuration, recording and reproduction can be performed by players of three types of formats.

Of course, it is not always necessary to form three types of signal recording layers, and two or four or more types may be used.

FIG. 2 shows an example of a two-layer optical disk including an HD signal layer 1 and a DVD format layer 2, and FIG. 3 shows an example of a two-layer optical disk including an HD signal layer 1 and a CD layer 3. Things.

In the above example, recording and reproduction for each signal recording layer are performed by irradiating light from the same direction. However, recording and reproduction of each signal recording layer are performed by irradiating light from directions opposite to each other. Reproduction may be performed.

FIG. 4 shows an example of a two-layer optical disk comprising an HD signal layer 1 and a DVD format layer 2,
FIG. 5 shows an example of a two-layer optical disc composed of an HD signal layer 1 and a CD layer 3.
Recording / reproducing surface of signal layer 1, DVD format layer 2, CD
The recording / reproducing surfaces of the layer 3 are opposite to each other, and a so-called double-sided disk is employed. Therefore, the HD signal layer 1
And the optical systems B and C of the DVD format layer 2
The optical system C of the D layer 3 is arranged on the opposite side of the optical disk.

The same applies to the case of a three-layer optical disk.
In the example shown in FIG. 5, the signal reading surfaces of the HD signal layer 1, the DVD format layer 2, and the CD layer 3 are opposite to each other.

Further, each signal recording layer may be composed of a plurality of layers. In this case, signal recording layers of the same density
It is formed at an interval of 0 μm or less, and by controlling the transmittance of the translucent film, at least two layers capable of recording and reproducing with the same optical pickup are present.

FIG. 7 shows an example of an optical disk having an HD signal layer, a DVD format layer, and a CD layer, each of which has two layers. The HD signal layer includes an HD (1) signal layer 1a and an HD (2) signal layer. 1b, DVD format layer is DVD
(1) Layer 2a, DVD (2) layer 2b, CD layer is CD
(1) Layer 3a and CD (2) layer 3b. Therefore, it has a total of six signal recording layers.

Next, a method of manufacturing the optical disk having the above-described configuration will be described.

For example, to manufacture the three-layer optical disc shown in FIG. 1, first, as shown in FIG.
For example, the stamper 12 is pressed against a polycarbonate sheet of m (3 to 177 μm) at a high temperature and a high pressure by using, for example, a pressure roll 11, and the unevenness formed in accordance with the signal is transferred to produce the HD substrate 13. The transfer of the unevenness may be performed by a so-called 2P method or the like.

At the same time, a DVD substrate 14 and a CD substrate 15 are manufactured by an injection molding method. The thickness of the DVD substrate 14 is, for example, 0.5 mm, and the thickness of the CD substrate 15 is, for example, 0.6 m.
m, and in each case, an uneven pattern such as a pit or a guide groove is formed in accordance with a signal at the time of injection molding.

Next, an HD signal layer, a DVD format layer, and a CD layer (not shown), which are signal recording layers, are formed on each substrate.

As described above, the required characteristics of the HD signal layer differ depending on the wavelength of the laser beam used, and a semi-transparent film having optimum characteristics is formed in consideration of the required characteristics.
As the material, a compound of Si (oxide, nitride, hydride, carbide, or a mixture thereof) is used.

The DVD format layer also needs to be a translucent film in order to enable recording and reproduction of the CD layer, and it is preferable that the optical characteristics are also appropriate according to the wavelength of the laser beam used.

As the CD layer, a reflective film having a reflectance of 70% or more for a laser beam having a wavelength of 780 nm is formed. Specific materials include Al, Au, Ag, Cu, and alloys thereof.

The substrate on which each signal recording layer is formed is bonded with an ultraviolet curable resin or the like to complete an optical disk. At this time, since the ultraviolet curable resin generally tends to have a reduced transmittance after curing, the CD substrate 15 is first used. After the UV curable resin layer 16 serving as a protective film is applied and formed on the CD layer forming surface, the UV curable resin 17 is applied to the surface of the CD substrate 15 opposite to the CD layer forming surface as shown in FIG. The DVD substrate 14 is superposed on this, and ultraviolet rays are irradiated from the DVD substrate 14 side.

Thereafter, an ultraviolet curable resin 18 is applied on the DVD substrate 14, and the HD substrate 13 is overlaid thereon as shown in FIG. Then, the excess ultraviolet curable resin is removed by rotating and shaking off, and curing is performed by irradiating ultraviolet rays from the HD substrate 13 side.

Thus, a hybrid optical disk having three signal recording layers is completed. When a hybrid optical disk is manufactured according to the above method, the HD substrate 13
If a concavo-convex pattern and a signal recording layer are provided on both sides by simultaneous double-sided transfer at the time of manufacturing the optical disc, a hybrid optical disc having a four-layer structure as shown in FIG. 11 can be constructed. In this case, if the protective layer 8 is formed on the uppermost signal recording layer 7 with a thickness of 10 μm at the maximum, or the protective layer is not provided, the signal recording layer 7 has a higher NA (for example, using a solid immersion lens). (NA ≧ 1.0).

As another manufacturing method, as shown in FIG. 12, a substrate 21 on which a DVD format layer and a CD layer are formed on both surfaces and a substrate 22 on which an HD signal layer is formed are prepared and bonded. Method.

In this case, both the substrate 21 and the substrate 22 may be formed by injection molding. At this time, the pits and grooves of the HD signal layer and the DVD format layer are
It is preferable to increase the size in advance. This is because in the HD signal layer and DVD format layer, a semi-transparent film is formed in the pits and grooves formed on the substrate by injection molding, and the pits and grooves are actually formed when light is irradiated from above in the figure. This is because it becomes substantially smaller than that performed.

The thickness of the substrate is, for example, 0.6 mm for the substrate 21 and 0.5 mm for the substrate 22, for example.

After these are bonded with an ultraviolet curable resin, a thickness of 3 to 177 μm (for example, 10 μm) is formed on the HD signal layer.
0 μm) of a cover layer (light transmitting layer), which may be directly formed of a high-viscosity ultraviolet curable resin,
It may be formed by laminating a 100 μm-thick transparent sheet (having no pits or grooves) with a low-viscosity ultraviolet curable resin.

Alternatively, it is also possible to manufacture a hybrid optical disk as shown in FIG. 1, for example, by applying the so-called 2P method.

FIG. 13 shows the process.
First, the first substrate 31 on which the first signal recording layer is formed
The replica is transferred by the 2P method using the stamper 32 to form the second substrate 33 (FIG. 13A), and after peeling it off (FIG. 13B), the replica is formed by the 2P method using another stamper 34. The third substrate 35 is formed by transfer (FIG. 13C). By repeating this, a hybrid optical disc having an arbitrary number of layers can be manufactured.

In order to manufacture an optical disk in which two signal recording layers of each format are formed as shown in FIG. 7, a double-sided molded substrate is prepared, and these are laminated with an ultraviolet curing resin layer at a predetermined interval. What is necessary is just to bond together.
At this time, adjacent layers having the same format are formed by setting the thickness and the like so that the reflectances from these layers are substantially equal.

The configuration of the optical disk to which the present invention is applied has been described above. However, it goes without saying that the present invention is not limited to these, and various modifications can be made without departing from the spirit of the present invention.

[0052]

As is apparent from the above description, according to the present invention, it is possible to achieve an unprecedented high-density recording and to provide an optical recording medium applicable to various uses. Can be.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a configuration example of a three-layer hybrid optical disc.

FIG. 2 is a schematic diagram illustrating a configuration example of a two-layer hybrid optical disc.

FIG. 3 is a schematic diagram illustrating another configuration example of a two-layer hybrid optical disc.

FIG. 4 is a schematic diagram illustrating a configuration example of a double-sided readout dual-layer hybrid optical disc.

FIG. 5 is a schematic diagram showing another configuration example of the double-sided reading dual-layer hybrid optical disc.

FIG. 6 is a schematic diagram showing a configuration example of a double-sided readout three-layer hybrid optical disc.

FIG. 7 is a schematic diagram showing a configuration example of a hybrid optical disc having each signal recording layer having a two-layer structure.

FIG. 8 is a schematic diagram illustrating an example of a manufacturing process of a hybrid optical disc, illustrating a forming process of each substrate.

FIG. 9 is a schematic view showing a first bonding step.

FIG. 10 is a schematic view showing a second bonding step.

FIG. 11 is a schematic diagram illustrating a configuration example of a four-layer hybrid optical disc.

FIG. 12 is a schematic view showing another example of the manufacturing process of the hybrid optical disc.

FIG. 13 is a schematic view showing still another example of the manufacturing process of the hybrid optical disc.

[Explanation of symbols]

1 HD signal layer (first signal recording layer), 2 DVD format layer (other signal recording layer), 3 CD layer (other signal recording layer), 4, 5, 6 transparent substrate (light transmitting layer)

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI G11B 7/24 541 G11B 7/24 541F

Claims (7)

[Claims] 1. An optical recording medium comprising: a first signal recording layer having a light transmission layer having a thickness of 3 to 177 μm; and at least one other signal recording layer. 2. The optical recording medium according to claim 1, wherein the other signal recording layer is a signal recording layer in which the thickness of a light transmitting layer is 0.55 to 0.65 mm. 3. The signal recording layer according to claim 1, wherein the other signal recording layer is a signal recording layer including a concave / convex pit and a reflection film.
The optical recording medium according to the above. 4. The optical recording medium according to claim 1, wherein the other signal recording layer is a write-once type signal recording layer including an organic dye layer. 5. The recording and / or reproducing for the first signal recording layer and the recording and / or reproducing for another signal recording layer are performed by irradiating light from the same direction. The optical recording medium according to the above. 6. The recording and / or reproducing for the first signal recording layer and the recording and / or reproducing for another signal recording layer are performed by irradiating light from opposite directions. The optical recording medium according to the above. 7. The optical recording medium according to claim 1, wherein the optical recording medium has two or more other signal recording layers.