JPH10302314A - Multilayer structure optical information medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reproduce information without any errors even if any one of reproducing devices is used by simultaneously constructing a low recording density optical information medium such as a compact disk and a high recording density optical information medium such as a digital video disk which are different in corresponding wavelengths and recording densities by using one medium. SOLUTION: A first optical information medium having a first information structure made of a recessed and projecting pit and a semi-transparent film on a first substrate and a second optical information medium having a second information structure made of a recessed and projecting pit and a reflective film on a second substrate are arranged so as to position the first and second substrates in the same direction and then stuck to each other. The semi-transparent film of such a multilayer structure optical information medium is made of one layer thin film which in turn is made of a material having a complex index of refraction of 2.4 or higher while a wavelength is above 620 nm and lower than 660 nm and an attenuation coefficient of 0.05 or lower while a wavelength is above 760 nm and lower than 800 nm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information medium such as an optical disk and an optical card, and more particularly to a reproducing apparatus for a high recording density optical information medium having a shorter reproducing light beam wavelength for a digital video disk (DVD). However, the present invention relates to an optical information medium for reproducing compatibility, which can be reproduced by using a reproducing apparatus for a low recording density optical information medium having a longer reproducing light beam wavelength for a compact disk (CD). .

[0002]

2. Description of the Related Art Conventionally, a reproducing apparatus for a low recording density optical information medium such as a compact disk (CD) has a substrate thickness of 1.2 m.
m, the NA of the objective lens of the optical head is as small as 0.45, and the wavelength of the light beam is as long as about 780 nm. Regarding the substrate thickness of the CD, the NA of the objective lens, and the wavelength of the light beam, see the compact disc reader (Heitaro Nakajima, Hiroshi Ogawa, co-author, Ohmsha, November 25, 1982)
Published on pages 12, 17, 18 and the like. On the other hand, a reproducing apparatus for a high recording density optical information medium such as a digital video disk (DVD) uses a medium having a substrate thickness of 0.6 mm, and the NA of the objective lens of the optical head is 0.1 mm.
60 and the wavelength of the light beam is from 630 nm to 680
It is as short as about nm. DVD substrate thickness, objective lens N
A. Regarding the wavelength of the light beam, see the Research and Development XI (Optical Industry and Technology Promotion Association, March 1996), pages 85 to 89, and IEEE Consumer Electron
ics (1996) FAM 20.2, pages 348-349 (The DVD Physica
l Format: JGF Kablau).

[0003]

SUMMARY OF THE INVENTION A low recording density optical information medium such as a compact disk (CD) and a digital video disk (DV) disclosed in the above-mentioned prior art.
D) and other high-density optical information media have the same format on one medium, and different formats such as substrate thickness, corresponding wavelength, and recording density can be simultaneously configured on one medium. Could not.

An object of the present invention is to provide a low-density optical information medium such as a compact disk (CD) having different substrate thicknesses, corresponding wavelengths, and recording densities, and a digital video disk (DVD) in a single medium. It is an object of the present invention to provide a multi-layered optical information medium which has a high recording density optical information medium format and has a sufficiently large reproduction signal intensity and can be reproduced by using either of the above-mentioned reproduction apparatuses.

[0005]

In order to achieve the above object of the present invention, the present invention is configured as described below.

That is, the multi-layered optical information medium of the present invention has a first information comprising a concave / convex pit provided on the surface of a first substrate and a translucent film provided on the concave / convex pit. A second optical information medium including a first optical information medium having a structure, a concave and convex pit provided on the surface of the second substrate, and a reflective film provided on the concave and convex pit; And an optical information medium having a structure in which the first and second substrates are arranged and bonded so as to be located in the same direction, and information is conveyed by a convergent light beam incident from the first substrate side. In the multilayer optical information medium to be reproduced, the translucent film has a complex refractive index of 620 nm.
It has a refractive index of 2.4 or more at a wavelength of 660 nm or less and a single thin film made of a material having an extinction coefficient of 0.05 or less at a wavelength of 760 nm or more and 800 nm or less.

In the above-mentioned multilayer optical information medium, the first substrate and the second substrate each have a thickness of 0.54 mm.
As described above, it is assumed to be 0.66 mm or less.

In the above-mentioned optical information medium having a multilayer structure,
When a light beam for reproducing information is incident from the first substrate side and converges on the first information structure, a flat portion of the first information structure measured from the first substrate side by the converged light beam Has a reflectance of 15% at a wavelength of 620 nm to 660 nm.
From the first substrate side with the converged light beam when the light beam is converged on the second information structure.
The reflectance of the flat part of the information structure of the above is 760 nm or more and 8
It is assumed that the thickness is within the range of not more than 00 nm and not less than 55%. By doing so, the reflectivity of the light beam focused and irradiated on each information structure is high, and good reproduction is possible.

Here, the dielectric layer is made of an oxide of Ti,
Bi oxide, Zr oxide, Ce oxide, Ta oxide, Hf oxide, La oxide, Y oxide, Sc
Oxide, Mg oxide, Si oxide, In oxide, Al oxide, Ge oxide, Pb oxide, Sn
Oxide, V oxide, Nb oxide, Cr oxide,
A group of oxides of W, a sulfide of Sb, a sulfide of Zn,
Group of Ga sulfide, In sulfide, Ge sulfide, Sn sulfide, Pb sulfide, and Mg fluoride, Ce
And at least one material selected from the group consisting of a group of fluorides of Ca, a group of fluorides of Ca, and a group of nitrides of Si, nitrides of Ta, nitrides of Al, and nitrides of B. The refractive index is 2.4 or more at a wavelength of 620 nm or more and 660 nm or less, and 760 nm or more and 800 n at a wavelength of 760 nm or less.
It is assumed that the extinction coefficient at m or less is 0.05 or less.

Of these dielectric layers, oxides include T
The oxide of i, the oxide of Bi, the oxide of Zr, the oxide of Ce, and the oxide of Ta control the amount of oxygen in the oxide to increase the refractive index while keeping the extinction coefficient small. This is preferable because it can be increased. In the sulfide, the sulfide of Sb, Z
By controlling the amount of sulfur in the sulfide, the sulfide of n is preferable in that the refractive index can be increased while keeping the extinction coefficient small. Among the nitrides, Si nitride and Ta nitride are preferable in that the refractive index can be increased while the extinction coefficient is kept small by controlling the amount of nitrogen in the nitride.

Further, in the multilayer optical information medium of the present invention, the reflective layer is made of Au, Au alloy, Ag, Ag alloy,
It is made of at least one material selected from the group consisting of Cu, Cu alloy, Al, and Al alloy. Among these reflective layer materials, Au and Au alloy can easily increase the reflectance of the flat portion of the second information structure, and Al and A
The alloy can reduce the manufacturing cost of the multilayer optical information medium.

Further, in the multi-layer optical information medium of the present invention, an adhesive layer transparent to the reproducing light beam is provided between the first and second optical information media. By setting the thickness of the adhesive layer transparent to the light beam in the range of 10 μm to 80 μm, it is possible to achieve both good bonding and good reproduction characteristics on the second optical information medium.

The substrate in the multilayer optical information medium of the present invention is
Made of polycarbonate or polyolefin, the first
In addition, by forming a substance transparent to the light beam between the second optical information media with an ultraviolet curable resin or a reactive adhesive, the multilayer optical information medium of the present invention can be mass-produced at low cost.

In the multilayer optical information medium according to the present invention, the recording density of the first optical information medium having the first information structure on the first substrate on the light incident side is equal to the second optical density of the second substrate on the second substrate. It is assumed that the recording density is higher than the recording density of the second optical information medium having the information structure. This makes it possible to reproduce the first information structure in the reproducing apparatus for a high-recording-density optical information medium having a small substrate thickness, and reproduce the second information structure in the reproducing apparatus for a low-recording-density optical information medium having a thick substrate. It is suitable.

[0015]

Embodiments of the present invention will be described below in more detail.

First Embodiment FIG. 1 shows an example of a cross-sectional structure of a multi-layered optical information medium exemplified in this embodiment.
First, information is formed on a surface of a disc-shaped polycarbonate plate having a diameter of 120 mm and a thickness of 0.575 mm by an injection molding method by using an uneven pit (8-16 having a pit depth of 100 nm, a track pitch of 0.74 μm and a minimum mark length of 0.44 μm).
Substrate 1 formed as an optical phase pit row comprising a modulation random pattern) was produced. On the substrate 1, a semi-transparent layer 2 consisting of a single dielectric layer in which a TiO2 (atomic ratio) layer was formed to a thickness of 300 nm was formed by a high-frequency magnetron sputtering method using an argon gas.
A read-only information structure was constructed to produce an optical information medium α1.

Next, a diameter of 120 mm and a thickness of 0.575 m
The information different from the above is formed on the surface of a disc-shaped polycarbonate plate having an irregularity pit (pit depth: 90 nm, track pitch: 1.6 μm, shortest mark length: 0.84 μm, by an 8-14 modulation random pattern. A substrate 3 formed as a phase pit row) was produced. A reflective layer 4 made of an Al layer having a thickness of 80 nm was formed on the substrate 2 by a high-frequency magnetron sputtering method using an argon gas to form a second read-only information structure. An ultraviolet curable resin was applied on the reflective layer 4 by a spin coating method to a thickness of 10 μm, and then cured by irradiating ultraviolet rays to form a protective layer 5, thereby producing an optical information medium α2.

The optical information media α1 and α2 produced in this manner are arranged such that the substrate 1 and the substrate 3 are oriented in the same direction (the substrate 1 of the optical information medium α1 and the protective layer 5 of the optical information medium α2 are on the outside). To form a multilayer optical information medium α.
Here, after the ultraviolet curable resin is dripped on the semi-transparent layer 2 of the optical information medium α1, the optical information medium α2 is attached to the optical information medium α1 so as to have a thickness of 50 μm so as to prevent bubbles from entering.
Was irradiated with ultraviolet light from the side of No. 3 to cure.

<Embodiment 2> The multi-layered optical information medium α produced in Embodiment 1 is used for the optical disc drive A ｛the reproducing light laser wavelength 650 nm and the objective lens numerical aperture (NA).
The reproduction was evaluated by 0.6% and the optical disk drive B (reproduction light laser wavelength: 780 nm, objective lens numerical aperture (NA): 0.45). Here, the drive A is a high-density optical information medium reproducing apparatus for a digital video disk (DVD), which has a shorter reproducing light beam wavelength and a substrate thickness of 0.6 mm, and has a compact drive B. Compatible with discs (CD), the light beam wavelength for reproduction is longer,
This is a reproducing apparatus for a low recording density optical information medium having a substrate thickness of 1.2 mm. The optical disk drive A has a linear velocity of 3.84
The optical disk drive B rotates at a constant linear velocity of 1.2 m / s. At an arbitrary radius position, the reproduction light level is set at 0.5 mW above the medium surface, and continuous light from the semiconductor laser is emitted. Irradiation was performed by irradiating through the substrate 1 with the objective lens in the head. The optical disc drive A focuses light on the first read-only information structure, and the optical disc drive B focuses light on the second read-only information structure, performs tracking while performing automatic focusing, and controls the intensity of reflected light. The information was read by detecting.

The information of the first read-only information structure of the multi-layered optical information medium α is stored in the second optical disk drive A by the optical disk drive A.
The information of the read-only information structure was reproduced by the optical disk drive B, and the jitter and the reflectance were measured, respectively. The jitter equalizes the recorded random pattern by three taps, performs a waveform equalization process using a transversal filter, sets a DC slice signal at the center of the read eye pattern using a tracking slice, and sets a reproduction signal and a slice signal. The cross point with was detected and measured as an edge position. P
LL (phase locked loop) and SYNC (synch
10000 time intervals between the clock signal and the data signal from the ronous code) are taken into a jitter meter (Time Interval Analyzer), and the standard deviation (σ) at this time is normalized by the detection window width (Tw) to obtain the jitter (σ / Tw). The reflectance (R) as viewed from the optical head was 9
The signal intensity (Ds) obtained by autofocusing a flat glass disk (reflectance Rs) laminated on 0 nm is defined as the reflectance (Rtop) of the longest mark interval portion in each data layer with reference to the signal intensity (Ds). Signal strength (Itop)
From the equation (R≡Rtop = Ds × Itop / Rs). Table 1 shows the results of the jitter characteristics, and Table 2 shows the results of the reflectance characteristics.

[0021] When the thickness of the substrate 1 is changed in the multilayer optical information medium α, the information of the first read-only information structure is written in the optical disk drive A, and the information of the second read-only information structure is written in the optical disk drive. Table 3 shows the results of reproduction with B and measurement of jitter.

[Table 3] First information structure Jitter due to jitter in second information structure Thickness of substrate 1 (Drive A) (Drive B) (mm) (%) (%) 0.51 25. 1 25.2 0.53 17.5 17.4 0.54 14.3 14.2 0.56 9.7 9.4 0.58 7.0 6.6 0.60 6.0 5.6.0 .62 7.0 6.5 0.64 9.6 9.3 0.66 14.1 14.0 0.67 17.3 17.2 0.69 24.8 24.9 If it is less than 0.54 mm or more than 0.66 mm, the jitter due to spherical aberration and coma aberration of the laser light wavefront is increased. This was a large jitter exceeding 15% of the level.

When the thickness of the substrate 3 is changed in the multi-layered optical information medium α, the information of the second read-only information structure is reproduced by the optical disk drive B and the result of measuring the jitter is shown. It is shown in FIG.

[0024] When the thickness of the substrate 3 is less than 0.54 mm or more than 0.66 mm, the jitter due to the spherical aberration and coma aberration of the laser light wavefront increases, so that the jitter of either the first or the second read-only structure becomes an error. The jitter was large, exceeding the minimum level of 15% at which information could be reproduced.

When the thickness of the transparent adhesive layer 6 was changed in the multilayer optical information medium α, the information of the second read-only information structure was reproduced by the optical disk drive B, and the jitter was measured. Table 5 shows the results.

[0026] When the thickness of the transparent adhesive layer 6 exceeds 110 μm, the noise of the laser light wavefront increases due to spherical aberration and coma, so that the jitter of the second read-only structure has a minimum level of 15 which can reproduce information without error. %.

<Third Embodiment> The reflectance (R) of the first read-only information structure and the second read-only information structure of the multilayered optical information medium α manufactured in the first embodiment as viewed from the optical head. FIG. 2 shows a result obtained by examining the wavelength dependence of ()) by optical simulation. In the first read-only information structure, D
When the laser wavelength is 620 nm or more and 660 nm or less for a high-density optical information medium reproducing apparatus such as a VD, the reflectivity level is 1 which can be reproduced by the high-density optical information medium reproducing apparatus.
The value is in the range of 5% to 40% (21% to 26%). In the second read-only information structure, a laser wavelength of 76 used in a low-recording-density optical information medium reproducing apparatus such as a CD is used.
At a value of 0 nm or more and 800 nm or less, the reflectance becomes a value of 55% or more (78% to 84%) which is a reflectance level that can be reproduced by the low-density optical information medium reproducing device.

As the translucent layer 2 of the optical information medium α having a multilayer structure, in addition to the TiO 2 used in the present embodiment, the complex refractive index has a refractive index of 2.4 or more at a wavelength of 620 nm to 660 nm. At a wavelength of 760 nm or more 8
The extinction coefficient may be a single-layer thin film made of a material having a extinction coefficient of 0.05 or less at a wavelength of 00 nm or less. By doing so, in the first read-only information structure, the DV
D, which is a reflectance level of 15 which can be reproduced by the high recording density optical information medium reproducing apparatus when the laser wavelength used in the high recording density optical information medium reproducing apparatus is 620 nm or more and 660 nm or less.
% To 40%, and even in the second read-only information structure, the low-recording-density optical information medium has a laser wavelength of 760 nm to 800 nm used in a low-recording-density optical information medium reproducing apparatus such as a CD. It can be set to 55% or more, which is a reflectance level that can be reproduced by the reproducing apparatus.

For example, as the translucent layer 2, a multi-layered optical information medium β using a single dielectric layer formed of a 270 nm Sb2S3 layer and obtained by a high-frequency magnetron sputtering method using argon gas is used. However, the reflectance when the information of the first read-only information structure is reproduced by the optical disk drive A is 33%, and the reflectivity when the information of the second read-only information structure is reproduced by the optical disk drive B is 33%. 80% could be obtained.

Further, for example, the translucent layer 2 is made of Si using a gas obtained by mixing 3% nitrogen gas with argon gas.
Even if a multi-layer optical information medium γ using a single dielectric layer in which a silicon nitride layer is formed to a thickness of 280 nm and obtained by high-frequency magnetron sputtering, the information of the first read-only information A reflectivity of 68% was obtained when the information was reproduced by the drive A, and a reflectivity of 83% was obtained when the information of the second read-only information structure was reproduced by the optical disk drive B.

The dielectric layer in the translucent layer 2 is made of Si, C
oxide of e, oxide of La, oxide of Si, oxide of In, oxide of Al, oxide of Ge, oxide of Pb, Sn
Oxide, Ta oxide, Sc oxide, Y oxide,
Ti oxide, Zr oxide, V oxide, Nb oxide, Cr oxide, W oxide, Zn sulfide, Ga sulfide, In sulfide, Sb sulfide, Ge sulfide,
Sn sulfide, Pb sulfide, Mg fluoride, Ce fluoride, Ca fluoride, Si nitride, Al nitride, T
at least one material selected from the group consisting of a nitride of a and a nitride of B;
If the refractive index at 0 nm or more and 660 nm or less is 2.4 or more and the extinction coefficient at a wavelength of 760 nm or more and 800 nm or less is 0.05 or less, the reflectance of the first read-only information structure at a laser wavelength of 620 nm to 660 nm is reduced. The reflectance of the second read-only information structure at a laser wavelength of 760 nm to 800 nm is 5% or more and 40% or less.
The jitter was 5% or more, and the jitter at the time of information reproduction in the first and second reproduction-only information structures could be suppressed to a sufficiently low value of 15% or less.

Of these dielectric layers, oxides include T
The oxide of i, the oxide of Bi, the oxide of Zr, the oxide of Ce, and the oxide of Ta control the amount of oxygen in the oxide to increase the refractive index while keeping the extinction coefficient small. In the sulfide, the sulfide of Sb and the sulfide of Zn are
By controlling the amount of sulfur in the sulfide, the refractive index can be increased while keeping the extinction coefficient small. In nitrides, the nitride of Si and the nitride of Ta control the amount of nitrogen in the nitride. By doing so, it is possible to increase the refractive index while keeping the extinction coefficient small, so that the reflectance of the first read-only information structure at a laser wavelength of 620 nm to 660 nm is higher in the range of 15% to 40%. It was able to be the value of one. Therefore, the jitter at the time of reproducing information in the first read-only information structure can be sufficiently suppressed.

As the reflection layer 4 of the multilayer optical information medium α, in addition to Al used in the present embodiment, an Au alloy, A
g, Ag alloy, Cu, Cu alloy, Al, Al Even when using a metal layer made of at least one material selected from the group consisting of Al alloy, the same result as in the present embodiment was obtained.

As the transparent adhesive layer 6 of the multilayer optical information medium α, in addition to the ultraviolet curing resin used in the present embodiment, a silicone-based reactive adhesive, an epoxy-based reactive adhesive, etc., having a wavelength of 620 nm or more. Even when a transparent material was used, the same result as in the present embodiment was obtained.

As a substrate used in the present embodiment, in addition to a polycarbonate substrate produced by an injection molding method, a polyolefin substrate produced by an injection molding method or a PMM substrate
The same result as in the present embodiment can be obtained by using the A substrate, or by using a substrate on which a UV-curable resin layer in which information is provided as uneven pits by a photopolymerization method is formed on the surface of a glass or resin substrate or the like. was gotten.

[0036]

As described above, according to the present invention, a low-density optical information medium such as a compact disk (CD) having different thicknesses, corresponding wavelengths, and recording densities in one medium, and a digital video disk (DVD) and other high-density optical information media formats are configured at the same time.
Information can be reproduced without error by satisfying the reproduction signal intensity sufficiently.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a cross-sectional structure of a multilayer optical information medium α exemplified in Embodiment 1 of the present invention.

FIG. 2 shows the wavelength dependence of the reflectance (R) of the first information structure and the second information structure in the multilayer optical information medium α exemplified in the third embodiment of the present invention as viewed from the optical head. FIG.

[Explanation of symbols]

 1, 3 ... substrate 2 ... translucent layer 4 ... reflective layer 5 ... protective layer 6 ... transparent adhesive layer.

Claims (8)

[Claims] 1. A first optical information medium having a first information structure comprising a first substrate provided with concave and convex pits on the surface of the substrate and a semitransparent film provided on the concave and convex pits; A second substrate provided on the first optical information medium and having a concave / convex pit on the substrate surface, and a second information structure comprising a reflective film provided on the concave / convex pit. Wherein the first information structure has a complex refractive index having a wavelength of 620 n. The optical information medium of claim 2, wherein the information is reproduced by a convergent light beam incident from the first substrate side.
a multi-layer structure light comprising a single-layer thin film made of a material having a refractive index of 2.4 or more at m or more and 660 nm or less and an extinction coefficient of 0.05 or less at wavelengths of 760 nm or more and 800 nm or less. Information medium. 2. The multilayer optical information medium according to claim 1, wherein the thickness of the first substrate and the thickness of the second substrate are respectively not less than 0.54 mm and not more than 0.66 mm. Structured optical information medium. 3. The multi-layered optical information medium according to claim 1, wherein when the convergent light beam converges on the first information structure, the first convergent light beam is used as the first convergent light beam. The reflectance of the flat portion of the first information structure measured from the substrate side is in the range of 15% to 40% at a wavelength of 620 nm or more and 660 nm or less, and when converged on the second information structure, the converged light beam The second measured from the first substrate side at
The reflectance of the flat part of the information structure of the above is 760 nm or more and 8
An optical information medium having a multilayer structure, wherein the optical information medium has a thickness of not more than 00 nm and not less than 55%. 4. The multi-layered optical information medium according to claim 1, wherein the first information structure comprises an oxide of Ti, an oxide of Bi, an oxide of Zr, Ce,
Oxide, Ta oxide, Hf oxide, La oxide, Y oxide, Sc oxide, Mg oxide, Si oxide, In oxide, Al oxide, Ge oxide Oxides of
Pb oxide, Sn oxide, V oxide, Nb oxide, Cr oxide, W oxide group, and Sb sulfide, Zn sulfide, Ga sulfide, In Sulfide, Ge
Sulfide, Sn sulfide, Pb sulfide group, and M
g fluoride, Ce fluoride, Ca fluoride group,
And Si nitride, Al nitride, Ta nitride, B
Characterized by comprising at least one kind of material selected from the group consisting of nitrides. 5. The multilayer optical information medium according to claim 1, wherein said second information structure is made of Au or an alloy containing Au as a main component, Ag or A
a multi-layer optical information medium comprising at least one material selected from an alloy containing g as a main component, Cu or an alloy containing Cu as a main component, Al or an alloy containing Al as a main component. . 6. A multi-layered optical information medium according to claim 1, wherein a transparent adhesive layer for transmitting a reproduction light beam is provided between said first and second optical information mediums. An optical information medium having a multilayer structure, comprising: 7. A multi-layer optical information medium according to claim 6, wherein said transparent adhesive layer has a thickness in a range of 10 μm to 80 μm. 8. The multi-layer optical information medium according to claim 1, wherein the recording density of said first optical information medium is made higher than the recording density of said second optical information medium. A multi-layered optical information medium characterized by being set at a higher height.