JP2000021016A - Optical information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a two layered optical disk on which a high density recording and reproducing is performed. SOLUTION: An optical information recording medium A is made on a transparent substrate 1, against which laser beams L are irradiated, by successively laminating a first information recording layer A1, a transparent layer 6 and a second information recording layer A2. The layer A1 is made by laminating a first dielectric layer 2, a first recording layer 3, which is made of a phase transition material, a second dielectric layer and a heat radiating layer 5 on the transparent substrate 1. The layer A2 is made by laminating a third dielectric layer 7, a second recording layer 8 made of the phase transition material, a fourth dielectric layer 9 and a reflection layer 10 on the layer 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase change type optical information recording medium for recording and reproducing information by irradiating a laser beam, and more particularly to an optical information recording medium suitable for high density recording.

[0002]

2. Description of the Related Art In recent years, with the rise of so-called multimedia, there has been a demand for handling a large amount of information such as digital moving images. Such a large amount of information is accumulated, and random access is performed as necessary. The need to regenerate is growing. Optical discs are optical information recording media that have the characteristics of random access, large capacity, and removable from recording / reproducing devices (removable), and have been used in large quantities in various fields.
In order to cope with the above-mentioned large capacity, it is required that a larger amount of information than ever can be handled.

[0003] In such an optical disc, the recording density in the two-dimensional direction is determined by the minimum spot diameter emitted from a laser light source used, and the smaller the minimum spot diameter, the higher the signal recording density. Therefore, in order to reduce the minimum spot diameter, the wavelength of the light source is shortened, and the numerical aperture NA of the objective lens is increased. However, there is a technical limitation in shortening the wavelength of the light source and increasing the numerical aperture NA of the objective lens, and the improvement of the recording density in the two-dimensional direction has reached the limit at present. Therefore, 3
Increasing the recording capacity in the dimensional direction, that is, stacking a large number of information recording layers for storing information signals in the thickness direction,
For example, attempts have been made to form two information recording layers.

[0004]

For example, in a two-layer optical disc having two information recording layers (recording layers) as described above, it is necessary to perform recording and reproduction of information signals while distinguishing each recording layer. The recording and reproduction of such an information signal is usually performed using the fact that the focal position when condensing the laser beam differs in each recording layer. That is, when a laser beam is irradiated from the substrate side through an objective lens and the first recording layer is focused on from the substrate side, the second recording layer is out of focus. The recording and reproduction of the information signal is performed only on the focused first recording layer.
On the other hand, when the focus is on the second recording layer, the recording and reproduction of the information signal is performed only on the focused second recording layer.

The problem here is the influence of the first recording layer when recording / reproducing the second recording layer. If this effect is large, recording / reproduction to / from the second recording layer cannot be performed satisfactorily. That is, the second recording layer is irradiated with laser light after passing through the first recording layer. At this time, the laser light absorbs some light intensity by the first recording layer. Therefore, 2
The intensity of the laser light actually applied to the second recording layer is considerably weaker than the intensity when emitted from the light source. The reflected light reflected from the second recording layer passes through the first recording layer and is received by a light receiving section of an optical pickup (not shown). At this time, since the reflected light absorbs a certain amount of light intensity by the first recording layer, the light intensity received by the light receiving unit is lower than the intensity reflected by the second recording layer. become weak.

From this point of view, the first recording layer used in the above-described two-layer optical disc has a relatively high light absorption rate, and the laser light is transmitted through the first recording layer. Greatly attenuates. Therefore, in the second recording layer, it is difficult to obtain sufficient irradiation light intensity and reflected light intensity required for recording and reproduction, and there is a problem that a sufficient reproduction output cannot be obtained.

Therefore, the present invention has been proposed in view of such a conventional situation, and has an optical information recording structure having a structure capable of obtaining a sufficient reproduction output from the information recording layer located at the second layer from the substrate side. The purpose is to provide a medium.

[0008]

In order to solve the above-mentioned problems, the present invention provides an optical information recording medium having the following constitutions (1) to (5).

(1) As shown in FIG. 1, a first information recording layer A1, a transparent layer 6, and a second information recording layer A2 are sequentially laminated on a transparent substrate 1 irradiated with a laser beam L. Optical information recording medium A, wherein the first information recording layer A1
Comprises a first dielectric layer 2, a first recording layer 3 made of a phase change material, a second dielectric layer 4, and a heat radiation layer 5 laminated on the transparent substrate 1, and the second information recording layer The optical information A2 is obtained by laminating a third dielectric layer 7, a second recording layer 8 made of a phase change material, a fourth dielectric layer 9, and a reflective layer 10 on the transparent layer 6. recoding media.

(2) The thickness of the first dielectric layer A1 is:
80 to 170 nm, and the thickness of the first recording layer 3 is 5 to 2
0 nm, and the thickness of the second dielectric layer A2 is 60 to 100.
2. The optical information recording medium according to claim 1, wherein

(3) The thickness of the third dielectric layer 7 is 8
0 to 150 nm, and the thickness of the second recording layer 8 is 10 to 4 nm.
3. The optical information recording medium according to claim 1, wherein the thickness of the fourth dielectric layer 9 is 0 nm and the thickness of the fourth dielectric layer 9 is 5 to 50 nm.

(4) The thickness of the heat radiation layer 5 is 50 to 2
The optical information recording medium according to any one of claims 1 to 3, wherein the optical information recording medium has a thermal conductivity of 50 W / mK or more.

(5) The optical information recording medium A according to claim 1, wherein the light intensity of the laser beam L applied to the transparent substrate 1 is set to 1, the first information recording layer A1.
When the first recording layer 3 is in a crystalline state, R11 = Rc1> 1/10 When the first recording layer 3 is in an amorphous state, R11 = Ra1> 1/20, where Rc1: The reflectance Ra1 in the crystalline state of the first recording layer 3 is the reflectance in the amorphous state of the first recording layer 3, and the reflectance R12 of the second information recording layer A2 is
When both the first recording layer 3 and the second recording layer 8 are in a crystalline state, R12 = Tc12 · Rc2> 1/10, the first recording layer 3 is in an amorphous state, and the second recording layer 8 is in a crystalline state. In the case of: R12 = Ta12 · Rc2> 1/20 When the first recording layer 3 is in a crystalline state and the second recording layer 8 is in an amorphous state, R12 = Tc12 · Ra2> 1/10 The first recording layer When both the third recording layer 8 and the second recording layer 8 are in the amorphous state, R12 = Ta12 · Ra2> 1/20, where Rc2 is the reflectance of the second recording layer 8 in the crystalline state Ra2: the second recording layer 8 Wherein Tc1: the light transmittance of the first recording layer 3 in the crystalline state, and Ta1: the light transmittance of the first recording layer 3 in the amorphous state. Medium.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the optical information recording medium of the present invention will be described below with reference to FIGS. FIG.
FIG. 2 is a diagram for explaining the structure of the optical information recording medium of the present invention, and FIG. 2 is a diagram for explaining the recording / reproducing state of the optical information recording medium of the present invention.

Optical information recording medium (optical disk) of the present invention
A is an optical disc in which a first information recording layer A1, a transparent layer 6, and a second information recording layer A2 are sequentially laminated on a transparent substrate 1 irradiated with a laser beam L, as shown in FIG. is there. The first information recording layer A1 is formed by laminating a first dielectric layer 2, a first recording layer 3, a second dielectric layer 4, and a heat radiation layer 5 made of a phase change material on a transparent substrate 1 made of a polycarbonate substrate. It becomes. The second information recording layer A2 includes a third dielectric layer 7, a second recording layer 8 made of a phase change material,
The dielectric layer 9 and the reflection layer 10 are laminated. Reference numeral 11 denotes a transparent substrate made of a polycarbonate substrate as a protective layer.
As described above, the optical disc A having the above-described configuration is a two-layer optical disc including the two phase-change recording layers 3 and 8.

Recording and reproduction using the optical disk A are performed as follows. That is, the recording laser light L irradiated from the transparent substrate 1 side is separately focused on the first (upper) recording layer 3 and the second (lower) recording layer 8, respectively.
An information signal can be recorded on each of the recording layers 3 and 8 independently. In addition, the reproduction laser beam L emitted from the transparent substrate 1 side is separately focused on each of the recording layers 3 and 8, so that the information signals recorded on each of the recording layers 3 and 8 can be reproduced independently. can do.

As the transparent substrate 1, a plastic substrate or a glass substrate made of an acrylic resin such as polycarbonate or polymethyl methacrylate (PMMA) is used. In the former case, grooves (guide grooves), pits and the like are formed concentrically or spirally by a photopolymer method (2P method) in the latter case.

The above-mentioned upper recording layer 3 and lower recording layer 8
Are each made of a phase change material that changes phase between a crystalline state and an amorphous state. GeS is used as a phase change material.
bTe-based compounds and AgInTeSb-based compounds are exemplified. Using this phase change material, recording pits are formed in the recording layers 3 and 8 as follows. That is, when the recording layers 3 and 8 made of this phase change material are formed by the sputtering method, they exhibit an amorphous state immediately after the film formation.

First, immediately after film formation, a low-power laser beam L or a high-temperature laser beam having a melting point or higher is applied to the entire recording layer 3 or 8 in an amorphous state so as to reach a temperature range between the crystallization temperature and the melting point. Initialization is performed by irradiating a laser beam of power or a laser beam of a combination thereof to change the phase into a crystalline state.

Next, recording is performed in which the recording laser beam L incident from the transparent substrate 1 side is focused on the recording layers 3 and 8 in a crystalline state. The recording layers 3, 8 absorb the energy of the recording laser light L by irradiating the recording layers 3, 8 with a high-power recording laser light L that raises the melting point of the phase change material constituting the recording layers 3, 8 or more. Then, after being melted into a liquid phase and rapidly cooled, it becomes an amorphous state. As a result, recording pits in an amorphous state are newly formed on the recording layers 3 and 8, respectively.
This is the same in the case of overwriting.

Next, reproduction is performed in which the reproducing laser beam L incident from the transparent substrate 1 side is focused on the recording pits on the recording layer 3 (recording layer 8). A low-power reproducing laser beam L that does not reach the crystallization temperature is irradiated. Thereby, the reflected light from the recording pit is a reflected light having a different reflectance from the reflected light from the other part (mirror part) (reflectance of crystalline mirror part> recording of amorphous state). Pit reflectivity). As a result, the recording pit on the recording layer 3 (recording layer 8) can be detected and reproduced by utilizing the difference in the reflectance.

The optical characteristics of the phase change material used as the recording material for the recording layers 3 and 8 take into account the positional relationship between the first information recording layer A1 and the second information recording layer A2 with respect to the transparent substrate 1. Is determined by That is, the first information recording layer A1 close to the transparent substrate 1 side is irradiated with the intensity of the recording / reproducing laser beam L, the light transmittance and the light absorption of the first information recording layer A1. Information recording layer A1
This is because the optical characteristics of the second information recording layer A2 located below are greatly affected, and there is a case where recording and reproduction of the second information recording layer A2 become impossible.

For this reason, the light transmittance of the first information recording layer A1 is the same as that of the second information recording layer A2, regardless of whether the first information recording layer A1 is unrecorded or recorded. Even in the case of a certain low reflectance, based on the reflected light from the second information recording layer A2 obtained by transmitting through the first information recording layer A1, light having a sufficient (reproduced) signal amplitude can be obtained. Transmission is required.

On the other hand, the intensity of the recording / reproducing laser beam L applied to the first information recording layer A1 is lower than the intensity of the recording / reproducing laser beam L applied to the second information recording layer A2. It is needless to say that a recording pit can be formed therein, and that the intensity of the reflected light can be obtained from this recording pit to obtain a sufficient reproduction signal amplitude.

In order to determine the phase change material used for the first recording layer 3 and the second recording layer 8 under the above-described conditions, the reflectance, the light transmittance, and the light absorptance are considered. It is necessary. The details are as follows. When the light intensity of the laser beam L applied to the transparent substrate 1 is 1, the reflectance R11 of the first information recording layer A1 is:
When the first recording layer 3 is in a crystalline state, R11 = Rc1> 1/10 When the first recording layer 3 is in an amorphous state, R11 = Ra1> 1/20, where Rc1: the crystalline state of the first recording layer 3 The reflectance Ra1 is the reflectance of the first recording layer 3 in the amorphous state, and the reflectance R12 of the second information recording layer A2 is that both the first recording layer 3 and the second recording layer 8 are crystalline. In the case of the state, R12 = Tc12 · Rc2> 1/10 When the first recording layer 3 is in the amorphous state, and when the second recording layer 8 is in the crystalline state, R12 = Ta12 · Rc2> 1/20 The first recording layer 3 Is in a crystalline state and the second recording layer 8 is in an amorphous state. R12 = Tc12 · Ra2> 1/10 When both the first recording layer 3 and the second recording layer 8 are in an amorphous state, R12 = Ta12 ・ Ra2> 1/20 where Rc2: the crystal state of the second recording layer 8 Ra2: reflectance of the second recording layer 8 in the amorphous state Tc1: light transmittance of the first recording layer 3 in the crystalline state Ta1: light transmittance of the first recording layer 3 in the amorphous state It was confirmed from experiments that it was necessary to satisfy the conditions.

Specifically, the light transmittance Tc1 in the crystalline state of the first recording layer 3 and the light transmittance Tc in the amorphous state
a1 is determined from the viewpoint of suppressing attenuation of the recording or reproducing laser beam L caused by passing (transmitting) through the recording layer 3. If the light transmittances Tc1 and Ta1 are small, 1
The intensity of the recording or reproduction laser beam L is attenuated by passing through the second recording layer 3, and the second recording layer 8 cannot be irradiated with the laser beam L with sufficient intensity. Therefore, there is a disadvantage that the information signal cannot be recorded and reproduced using the second recording layer 8.

The reflectance Rc2 in the crystalline state of the second recording layer 8 and the reflectance Ra2 in the amorphous state are:
This is set from the point of reflectance for obtaining a sufficient reproduction signal amplitude. If the reflectances Rc2 and Ra2 are small, the reflected light from the second recording layer 8 can be output with sufficient intensity when transmitted through the first recording layer 3 and emitted to the substrate 1 side. Can not. As a result, the second recording layer 8
The laser beam L cannot be irradiated with sufficient intensity.
Therefore, there is a disadvantage that the information signal cannot be reproduced using the second recording layer 8.

The reflectance Rc of such a first recording layer 3
The optical characteristics of 1,1, Ra1, the light transmittance Tc1, Ta1 and the reflectivities Rc2, Ra2 of the second recording layer 8 are, in particular, the refractive index n and the extinction coefficient k of the phase change material used as the recording material. Greatly depends on

On the other hand, the thermal characteristics of the first recording layer 3 and the second recording layer 8 are largely different from those of the first information recording layer A1 and the second information recording layer A2. Dependent. That is, the heat generated during recording on the first recording layer 3 is eliminated by radiating the heat from the second dielectric layer 4 and the heat radiation layer 6 made of a transparent dielectric. Heat generated during recording on the second recording layer 8 is eliminated by radiating heat from the fourth dielectric layer 9 and the reflective layer 10.

More specifically, when the first and second dielectric layers 2 and 4 (third and fourth dielectric layers 7 and 9) are provided so as to sandwich the recording layer 3 (recording layer 8), the substrate 1 The first dielectric layer 2 (third dielectric layer 7) on the side has a large optical characteristic (reflectance, light transmittance, light absorption) of the recording layer 3 (recording layer 8) due to the optical interference effect. Works. On the other hand, the dielectric material forming the first dielectric layer 2 (the third dielectric layer 7) generally has a property of hardly diffusing heat. As a result, the second dielectric layer 4
The (fourth dielectric layer 9) greatly affects the cooling rate of the recording layer 3 (recording layer 8). Second dielectric layer 4 (fourth dielectric layer 9)
The thicker the film thickness, the easier it is for the recording layer 3 (recording layer 8) to store heat and the slower the cooling rate (slow cooling structure). In this case, although the recording sensitivity to the laser beam is improved, a problem arises in that the phase change material constituting the recording layer 3 (recording layer 8) flows due to heat storage of the recording layer 3 (recording layer 8).

Therefore, in order to suppress the heat storage of the first recording layer 3, it is effective to use the second dielectric layer 4 and the heat radiation layer 5 together. The heat radiation layer 5 is a dielectric protective film having a relatively large thermal conductivity. By using this, heat diffusion is promoted, and heat conduction to the second recording layer 8 can be largely prevented. it can. When the thickness of the second dielectric layer 4 is reduced and the heat radiation layer 5 is provided thereon, the heat of the recording layer 3 is easily conducted to the heat radiation layer 5 via the second dielectric layer 4. The cooling rate is further increased (rapid cooling structure). A dielectric protection film may be further provided between the reflection films. As a result, heat storage of the recording layer 3 is prevented beforehand.

On the other hand, in order to suppress the heat storage of the second recording layer 8, it is effective to use the fourth dielectric layer 9 and the reflective layer 10 together. Further, when the thickness of the fourth dielectric layer 9 is reduced, the heat of the recording layer 8 is easily conducted to the reflection layer 10 via the fourth dielectric layer 9, so that the cooling rate is further increased (the rapid cooling structure). ).

Further, the first and second dielectric layers 2,
Even if a material having a high thermal conductivity (radiation effect) is used as the fourth (third and fourth dielectric layers 7 and 9), the heat storage of the recording layer 3 (recording layer 8) can be largely suppressed. .

The materials of the first, second, third, and fourth dielectric layers 2, 4, 7, 9 and the heat radiation layer 5 may be those having little absorption in the wavelength region of the laser light L. Any of them may be used, and examples thereof include nitrides, oxides, and sulfides of metals such as Al and semiconductor elements such as Si, for example, a ZnS-SiO2 mixture. When a heat diffusion effect is expected, it is desirable to use a material having high thermal conductivity such as Al3 N4 or SiC.

The reflection layer 9 is made of Al, Au, Ag,
Alternatively, alloys of these materials, such as Ti and Cr, are used.

The thermal properties of the recording layers 3 and 8 are greatly affected by the thickness of the phase change material film itself. If the thickness of the phase change material film is too large, the heat capacity becomes large, and the phase change material film is easily recrystallized. In this case, the erasing ratio is improved, but the flow of the phase change material film easily occurs due to the heat storage effect, and the overwrite characteristics (durability) deteriorate. On the other hand, if the thickness of the phase change material film is too small, the deterioration of the film itself becomes severe.
The layer configuration of the recording layers 3 and 7 needs to be optimized in consideration of the above-described effects on the optical characteristics and the thermal characteristics.

The transparent layer 6 described above, as shown in FIG.
The reflected light R2 from the second recording layer 8 is applied to the first recording layer 3
And has such a thickness that it can be optically separated from the reflected light R1 by the optical pickup (not shown) close to the substrate 1 side. Specifically, the thickness of the transparent layer 6 is 40 μm
(Preferably 35 to 50 μm, best 45 μm). If the thickness of the transparent layer 6 is thinner (0 to 30 μm), the two reflected lights R1 and R2 cannot be optically separated. On the other hand, if the thickness of the transparent layer 6 is thicker (50 to 100 μm), spherical aberration and the like occur, so that the two reflected lights R1 and R2 can be separated optically, but the detection output of the surroundings is small. Since the spot light is blurred, a good reproduction signal cannot be obtained. It is necessary to set the thickness appropriately in consideration of this point.

In this transparent layer 6, grooves (guide grooves), pits, and the like used for recording and reproduction of the second recording layer 8 are formed concentrically or spirally as an uneven shape.

The two-layer optical disc A having the structure described in detail above
Recording and reproduction of information signals with respect to (shown in FIG. 1) are performed by an optical head (optical pickup) having an optical system having a well-known configuration as described below.

This optical pickup comprises a semiconductor laser (wavelength 650 nm) as a light source, a collimator lens, a 1/4
An irradiation system including a wave plate and an objective lens, a condenser lens,
It is composed of a focus servo system including a cylindrical lens and a photodiode. The optical disc A whose optical characteristics are to be measured is placed on a turntable with the substrate 1 side facing the objective lens of this optical system.

In such an optical system, the recording or reproducing laser light L emitted from the light source is converted into parallel light by passing through a collimator lens, and this parallel light is transmitted through a beam splitter, a 波長 wavelength plate, and an objective lens. After passing through, a beam spot is formed on the disk surface (recording layer 3 or recording layer 8). On the other hand, the reflected lights R1 and R2 reflected from the recording layer 3 or the recording layer 8 pass through the objective lens and the quarter-wave plate again and enter the beam splitter. The light that has entered the beam splitter is reflected by a focus servo system, passes through a condenser lens and a cylindrical lens, is received by a photodiode, and the light intensity is detected. This light intensity information is
The laser beam is transmitted to a biaxial device for controlling the movement of the objective lens in the optical axis direction and is recorded on the recording layers 3 and 8 to be recorded or reproduced.
The objective lens is moved so as to focus accurately. In this manner, recording and reproduction of information signals on the dual-layer optical disc A can be performed.

(Embodiment) Hereinafter, a specific embodiment of the optical disc A of the present invention will be described.

In the optical disc A, recording and reproduction of information signals are performed on the first information recording layer A1 and the second information recording layer A2 for rewritable use. The optical disc A having the two-layer structure was prepared in the following order (1) to (6).

(1) First, in the transparent substrate 1 described above, grooves (guide grooves), pits, and the like are formed concentrically or spirally on the surface on which the first dielectric layer 2 is laminated, as concavo-convex shapes. A polycarbonate substrate was prepared. The thickness of the substrate 1 is 0.6 mm.

(2) Next, on this polycarbonate substrate 1, a first dielectric layer 2 made of a ZnS-SiO2 mixture and a first layer of a phase change material film made of a ternary alloy of Ge2 Sb2 Te5 are recorded. The first information recording layer A1 was formed by sequentially depositing a layer 3, a second dielectric layer 4 made of a ZnS-SiO2 mixture, and a heat radiation layer 5.

The thickness of each layer constituting the first information recording layer A1 is as follows. The thickness of the first dielectric layer 2 is 80 to 170 nm, desirably 100 nm. The thickness of the recording layer 3 is 5 to 20 nm, desirably 8 nm. The thickness of the second dielectric layer is 60 to 100 nm, desirably 80 nm. The thickness of the heat radiation layer 5 is 50 to 200 nm, preferably 90
nm and thermal conductivity of 50 W / mK or more

(3) Next, grooves (guide grooves), pits and the like are formed on the first information recording layer A1 (heat radiation layer 5) thus formed by the photopolymer (2P) method. The transparent layer 5 formed concentrically or spirally was formed. The thickness of the transparent layer 6 is 45 μm.

(4) Subsequently, on this transparent layer 6 (the surface on which the third dielectric layer 7 is laminated), a third dielectric layer 7 made of a ZnS-SiO2 mixture and a ternary alloy of Ge2 Sb2 Te5 A second recording layer 8, which is a phase change material film made of Zn,
A second information recording layer A2 was formed by sequentially forming a fourth dielectric layer 9 made of an S-SiO2 mixture and a reflective layer 10 made of Al.

The thickness of each layer constituting the second information recording layer A2 is as follows. The thickness of the third dielectric layer 7 is 80 to 150 nm, preferably 150 nm. The thickness of the recording layer 8 is 10 to 40 nm, preferably 20 n.
m The thickness of the fourth dielectric layer 9 is 5 to 50 nm, preferably 1
8 nm The thickness of the reflective layer 10 is 230 nm.

(5) Further, the second information recording layer A
A protective layer 10 having a thickness of 5 μm was formed by spin-coating an ultraviolet-curable resin on 2 (reflective layer 10). Thus, a two-layer optical disc A was manufactured.

(6) Finally, the optical disk A was initialized by irradiating the entire surface of the recording layers 3 and 8 of the two-layer optical disk A manufactured as described above with an initialization laser beam. Thus, the optical disc A was manufactured in the order of (1) to (6) described above.

The optical disk A manufactured in this manner is irradiated with a recording laser beam L, so that each of the recording layers 3 and 3 is irradiated.
8, recording pits were formed, and the optical characteristics of a portion where the recording pit was formed and a portion where the recording pit was not formed with respect to laser light having a wavelength of 650 nm were examined.

The optical characteristics of the first information recording layer A1 and the second information recording layer A2 will be described below. Here, the reflectance of the second information recording layer A2 is
The laser beam L emitted from the side passes through the first information recording layer A1, is reflected by the second information recording layer A2 (recording layer 8),
Again, this corresponds to the light intensity that passes through the first information recording layer A1 and returns to the substrate 1 side.

Assuming that the light intensity of the laser beam L applied to the transparent substrate 1 is 1, the reflectance Rc1 in the crystalline state of the first recording layer 3 is:
0.192 The reflectance Ra1 of the first recording layer 3 in the amorphous state is:
0.097 The light transmittance Tc1 in the crystalline state of the first recording layer 3 is:
0.730 The light transmittance Ta1 of the first recording layer 3 in the amorphous state is:
0.573 The reflectance Rc2 of the second recording layer 8 in the crystalline state is:
0.344 The reflectance Ra2 of the second recording layer 8 in the amorphous state is:
0.212.

From this, the first information recording layer A1
R11 = Rc1> 1/10 = 0.192> 0.1 when the first recording layer 3 is in a crystalline state, and R11 = Ra1 when the first recording layer 3 is in an amorphous state. > 1/20 = 0.097> 0.05.

On the other hand, the reflectivity R12 of the second information recording layer A2 is such that when both the first recording layer 3 and the second recording layer 8 are in a crystalline state, R12 = Tc12.Rc2> 1/10 = (0 .730) 2 · 0.344> 0.1, the first recording layer 3 is in an amorphous state, and the second recording layer 8
Is in a crystalline state, R12 = Ta12.Rc2> 1/20 = (0.573) 2.0.344> 0.05, the first recording layer 3 is in a crystalline state, and the second recording layer 8 is in an amorphous state. In the case of the state, R12 = Tc12.Ra2> 1/10 = (0.730) 2.0.212> 0.1, and both the first recording layer 3 and the second recording layer 8 are in the amorphous state. R12 = Ta12.Ra2> 1/20 = (0.573) 2.0.212> 0.05.

As described above, in this two-layer optical disc A,
Since the first information recording layer A1 (especially the first recording layer 3) has a high light transmittance Tc1 and Ta1, the first information recording layer A1 transmits through the first information recording layer A1 to the second information recording layer A2. Light can be incident at a sufficient intensity. Further, in each of the first information recording layer A1 and the second information recording layer A2, high reflectivity R11 and R12 can be obtained, and good recording / reproducing characteristics can be obtained.

[0058]

As described above, according to the optical information recording medium of the present invention, it is possible to irradiate a recording or reproducing laser beam with sufficient intensity to the second information recording layer made of a phase change material. In addition, since the reflected light from the information recording layer can be received with a sufficient intensity, a sufficient reproduction output can be obtained not only from the first information recording layer but also from the second information recording layer. Is possible, it is possible to provide an optical disc having a two-layer configuration capable of high-density recording and reproduction.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a structure of an optical information recording medium of the present invention.

FIG. 2 is a diagram for explaining a recording state of an optical information recording medium of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 1st dielectric layer 3 1st recording layer 4 2nd dielectric layer 5 Heat dissipation layer 6 Transparent layer 7 3rd dielectric layer 8 2nd recording layer 9 4th dielectric layer 10 Reflection layer A Optical information recording Medium A1 First information recording layer A2 Second information recording layer L Laser beam R11, R12, Ra1, Ra2, Rc1, Rc2 Reflectivity

Claims (5)

[Claims] A first substrate on which a laser beam is irradiated;
An optical information recording medium comprising: an information recording layer, a transparent layer, and a second information recording layer, which are sequentially laminated, wherein the first information recording layer comprises a first dielectric layer, a phase A first recording layer made of a changeable material, a second dielectric layer, and a heat dissipation layer, and the second information recording layer is formed on the transparent layer by a third dielectric layer made of a phase change material. An optical information recording medium comprising a stack of two recording layers, a fourth dielectric layer, and a reflective layer. 2. The film thickness of said first dielectric layer is 80-170.
The optical information recording medium according to claim 1, wherein the thickness of the first recording layer is 5 to 20 nm, and the thickness of the second dielectric layer is 60 to 100 nm. 3. The thickness of the third dielectric layer is 80 to 150.
3. The optical information recording medium according to claim 1, wherein the thickness of the second recording layer is 10 to 40 nm, and the thickness of the fourth dielectric layer is 5 to 50 nm. 4. The optical information according to claim 1, wherein the heat radiation layer has a thickness of 50 to 200 nm and a thermal conductivity of 50 W / mK or more. recoding media. 5. The optical information recording medium according to claim 1, wherein the light intensity of the laser beam applied to the transparent substrate is set to 1, When the first recording layer is in a crystalline state, the reflectance R11 of the information recording layer is as follows: R11 = Rc1> 1/10 When the first recording layer is in an amorphous state, R11 = Ra1> 1/20, where Rc1 : The reflectance of the first recording layer in a crystalline state Ra1: the reflectance of the first recording layer in an amorphous state, and the reflectance R12 of the second information recording layer is the reflectance of the first and second recording layers. When both recording layers are in a crystalline state, R12 = Tc12 · Rc2> 1/10 When the first recording layer is in an amorphous state and when the second recording layer is in a crystalline state, R12 = Ta12 · Rc2> 1/1 20 The first recording layer is in a crystalline state, the second recording layer is in an amorphous state. In the case of the quality state, R12 = Tc12 · Ra2> 1/10 When both the first recording layer and the second recording layer are in the amorphous state, R12 = Ta12 · Ra2> 1/20, where Rc2: the second Reflectance in the crystalline state of the recording layer Ra2: Reflectivity in the amorphous state of the second recording layer Tc1: Light transmittance in the crystalline state of the first recording layer Ta1: in the amorphous state of the first recording layer An optical information recording medium having a light transmittance.