JP2984538B2 - Information optical recording media - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information optical recording medium,
In particular, it relates to a rewritable information optical recording medium.

[0002]

2. Description of the Related Art In recent years, in the field of information recording, demands for higher density and higher capacity have been increasing. An optical disk device is an information recording device that can satisfy such requirements. The optical disk device performs recording / reproduction of information using laser light. An optical disk device has a recording density 10 to 100 times that of a conventional magnetic recording medium. Further, in the optical disk device, it is possible to record / reproduce information while keeping the recording / reproducing head and the medium in a non-contact state. Therefore, even after long-time use, the recording medium is less damaged.

An optical disk device records information on an information optical recording medium. Information optical recording media are read-only, write-once,
And rewritable types. The read-only type can read only information. The write-once information optical recording medium is capable of recording and reproducing information. However, in a write-once information optical recording medium, information once recorded cannot be erased. A rewritable information optical recording medium is capable of recording and reproducing information.
In a rewritable information optical recording medium, recorded information can be erased and rewritten. These information optical recording media are properly used depending on the application. A rewritable information optical recording medium is suitable for a data file for a computer.

[0004] Recording methods for rewritable information optical recording media can be broadly classified into two types: a magneto-optical method and a phase change method.

In the phase change method, a phase change layer is provided inside an information optical recording medium. The phase change layer has a portion in a crystalline state and a portion in an amorphous state. Information is recorded by a combination of a part in a crystalline state and a part in an amorphous state.

A transition from a crystalline state to an amorphous state, and
The transition from an amorphous state to a crystalline state is called a phase change.
The phase change can be caused by heating and cooling the phase change layer. The heating of the phase change layer is performed by laser light irradiation. In order to change a specific portion of the phase change layer to a desired state, the cooling rate of the phase change layer is controlled. The cooling rate can be controlled by adjusting the luminous output and luminous time of the irradiated laser light. The portion in the crystalline state and the portion in the amorphous state in the phase change layer can be detected based on a difference in reflectance or a difference in phase of reflected light.

Several methods for recording and erasing information recorded on a rewritable information optical recording medium of the phase change type have been proposed. In recent years, methods for simultaneously performing recording and erasing with the same laser beam have been actively studied. Such a method is called one-beam overwriting. In one-beam overwriting, erasing of old information and writing of new information are performed simultaneously.

However, when information is recorded by one-beam overwriting, there is a problem that the jitter of a reproduced signal is large. The cause of this phenomenon is that the absorptance of laser light is different between a region in a crystalline state and a region in an amorphous state.

In order to eliminate this phenomenon, attempts have been made to make the absorption rates of both regions equal. Specifically, the absorptance of both regions was adjusted by adjusting the thickness of each layer inside the information optical recording medium. However, this method could not reduce the jitter of the reproduced signal.

This is presumed to be due to the difference in latent heat between the crystalline region and the amorphous region when the state changes. Based on this estimation, there has been proposed a method of forming a layer inside the information optical recording medium such that the absorptance in the crystalline region is higher than that in the amorphous region.

An example of such a method is described in
"Technology of IEICE" MR92-1 published by The Institute of Electronics and Communication Engineers of Japan
48 (CPM92-148), pp. 37-42, a paper entitled "High Speed Overwrite Phase Change Optical Disk". The feature of the technology described in this document lies in the reflective layer made of Au. In this paper, it is stated that such a configuration reduces mark distortion at the time of overwriting. The distortion of the mark at the time of overwriting is a phenomenon corresponding to the jitter of the reproduction signal.

[0012]

However, in the information optical recording medium having the above-described structure, there is a problem that if rewriting is performed many times, the jitter of a reproduced signal increases. It is presumed that this is because the Au film serving as the reflective layer is peeled or deformed when rewriting is performed many times.

[0013]

SUMMARY OF THE INVENTION In view of the above problems of the prior art, an object of the present invention is to provide an information optical recording medium in which the jitter of a reproduced signal does not increase even after rewriting has been performed many times. It is in. More specifically, an object of the present invention is to provide an information optical recording medium configured so that the absorptance in a crystalline state region is larger than that in an amorphous state region. An object of the present invention is to provide an information optical recording medium in which a layer does not peel or deform.

In order to achieve such an object, according to the present invention, in the information optical recording medium, the reflection layer is configured to contain Si.

[0015] In another embodiment of the present invention, the information optical recording medium, a transparent substrate 1, a first interference layer 2 comprising a mixture of ZnS and SiO ₂ is provided in an upper layer than the transparent substrate 1
And Ge ₂ Sb provided above the first interference layer 2.
_A phase change layer 3 containing ₂ Te ₅ , a second interference layer 4 provided above the phase change layer 3 and containing a mixture of ZnS and SiO _2, and a second interference layer 4 provided above the second interference layer 4 Si
And a reflection layer 5 including

In another embodiment of the present invention, the thickness of the phase change layer of the information optical recording medium is set to 10 nm to 20 nm. In order to make the effect of the present invention more remarkable, the thickness of the phase change layer may be set to 10 nm to 16 nm.

In another embodiment of the present invention, the thickness of the second interference layer of the information optical recording medium is set to 40 to 100 nm. In order to make the effect of the present invention more remarkable, the thickness of the second interference layer may be set to 40 nm to 55 nm.

In another embodiment of the present invention, the thickness of the reflective layer of the information optical recording medium is set to 50 to 100 nm.
In order to make the effect of the present invention more remarkable, the thickness of the reflective layer may be set to 55 nm to 85 nm.

In another embodiment of the present invention, the thickness of the first interference layer of the information optical recording medium is set to 200 to 250 nm. To make the effect of the present invention more remarkable, the first
The thickness of the interference layer may be set to 220 μm to 250 nm.

In another embodiment of the present invention, a protective layer is provided on at least one of the reflective layer and the transparent substrate of the information optical recording medium.

In another embodiment of the present invention, information is written / read to / from the information optical recording medium having the above-mentioned structure by using a laser beam having a wavelength of 630 to 830 nm. At this time, the diameter of the spot of the laser beam on the phase change layer is suitably from 1.0 μm to 1.4 μm.

In another embodiment of the present invention, the information optical recording medium is formed by sputtering ZnS and SiO
_A first step of forming a first interference layer by sputtering a sintered target of the mixture of No. ₂ with argon gas; and Ge ₂ S
a second step of forming a phase change layer by sputtering a target of b ₂ Te ₅ with argon gas;
_A third step of forming a second interference layer by sputtering a sintered target of the mixture of ₂ with argon gas, and a fourth step of forming a reflective layer 5 by sputtering an Si target with argon gas. It is manufactured by a manufacturing method.

[0023]

【Example】

[Structure] Next, a first embodiment of the present invention will be described with reference to the drawings.

Referring to FIG. 1, in an information optical recording medium D of the present embodiment, a first interference layer 2, a phase change layer 3, a second interference layer 4, a reflection layer 5, and a protection layer are provided on a transparent substrate 1. 6 are stacked in this order.

As the transparent substrate 1, a polycarbonate resin plate, a polyolefin resin plate, a glass plate provided with a photopolymer, an acrylic plate provided with a photopolymer, or the like can be used. The transparent substrate 1 is formed in a circular shape having a diameter of, for example, 130 mm, 120 mm, 90 mm, or the like. It is desirable that guide grooves and guide pits for tracking servo are formed on the transparent substrate 1. The track pitch of the guide groove and the guide pit is 0.6 to 1.6 μ.
m.

The first interference layer 2 is a mixture of ZnS and SiO 2. The thickness of the first interference layer 2 is 200 to 250 μm
It is. To make the effect more remarkable, the first interference layer 2
Preferably has a thickness of 220 to 250 μm.
The content ratio of SiO2 in the first interference layer 2 is desirably 10 to 20 mol%. It is desirable that the refractive index of the first interference layer 2 is about 2.2.

The phase change layer 3 contains Ge ₂ Sb ₂ Te ₅ as a main component. The thickness of the phase change layer 3 is 10 to 20 nm. In order to make the effect more remarkable, the thickness of the phase change layer 3 is preferably 10 to 16 nm. If necessary, a small amount of an element such as N may be added to the phase change layer 3.
By adding a small amount of these elements, the phase change layer 3
Can be prevented from becoming large. By preventing the crystal grain boundaries from becoming large, it is possible to prevent an increase in reproduced signal noise.

The second interference layer 4 is a mixture of ZnS and SiO ₂ . The thickness of the second interference layer 4 is 40 to 100 nm. To make the effect more remarkable, the thickness of the second interference layer 4 is preferably 40 to 55 nm. The abundance ratio of SiO ₂ in the second interference layer 4 is preferably 10 to 20 mol%. Further, it is desirable that the refractive index of the second interference layer 4 is about 2.2.

The reflection layer 5 contains Si as a main component. Reflective layer 5
An example of a specific material is Si containing less than 1 atomic% of B.
It is. The thickness of the reflection layer 5 is 50 to 100 nm.
In order to make the effect more remarkable, the thickness of the reflection layer 5 should be 5
It is preferably from 5 to 85 nm.

The thickness of each layer should be set according to the use conditions such as the wavelength of the laser beam. At that time, the thickness is preferably adjusted in the order of the first interference layer 2, the reflection layer 5, the second interference layer 4, and the phase change layer 3. That is, the optimum thickness of the first interference layer 2 is most easily affected by the use conditions. On the other hand, in the phase change layer 3, the optimum thickness does not change significantly even when the use conditions change.

The protective layer 6 is made of an ultraviolet curable resin or the like.

It is also possible to bond two information optical recording media described above. Referring to FIG. 2, the information optical recording medium D includes an information optical recording medium D0 and an information optical recording medium D.
1 is included. The information optical recording medium D0 and the information optical recording medium D1 are adhered by an adhesive layer 7. The information optical recording medium D1 includes a transparent substrate 1, a first interference layer 2, a phase change layer 3,
It comprises a second interference layer 4, a reflective layer 5 and a protective layer 6. These constitute an information optical recording medium having the same structure as that shown in FIG. The information optical recording medium D1 includes a transparent substrate 11, a first interference layer 12, a phase change layer 13, and a second interference layer 1.
4, a reflective layer 15 and a protective layer 16. These constitute an information optical recording medium having the same structure as that shown in FIG. The adhesive layer 7 adheres the protective layer 6 of the information optical recording medium D0 to the protective layer 16 of the information optical recording medium D1.

The information optical recording medium having the above-mentioned structure is formed by using a semiconductor laser having a wavelength of about 630 to 830 nm.
Suitable for writing / reading. At this time, the diameter of the laser spot near the phase change layer 3 is 1.0 μm.
The laser beam should be focused so that it is between m and 1.4 μm. [Manufacturing Method] Next, a method for manufacturing the information optical recording medium of the first embodiment will be described with reference to examples.

In the following example, an information optical recording medium D having the structure shown in FIG. 2 is formed. That is, the information optical recording media D0 and D1 are formed on two sheets, and these are adhered.

The dimensions of each part of the information optical recording medium D manufactured in the following example are as follows. That is, the transparent substrate 1
, The diameter of the transparent substrate 1, the pitch of the guide grooves of the transparent substrate 1, the thickness of the first interference layer 2, the thickness of the phase change layer 3, the thickness of the second interference layer 4, and the thickness of the reflection layer 5. The thickness is 1.
2mm, 130mm, 1.2μm, 235nm, 13n
m, 45 nm, and 70 nm.

The same method can be used even when the dimensions of each part of the information optical recording medium D are other than the above.

In the first step, a first interference layer 2 is provided on a transparent substrate 1.

The material of the transparent substrate 1 is a polycarbonate resin. The dimensions of the transparent substrate 1 are 130 mm in diameter and 1.2 in thickness. The transparent substrate 1 is provided with a guide groove having a pitch of 1.2 mm.

The first interference layer 2 is formed by sputtering. The sputtering is performed after evacuation in a vacuum of 1 × 10 ⁻⁶ Torr or less. Before forming the first interference layer 2, the surface of the transparent substrate 1 is sputter-etched to a thickness of about 0.2 nm with argon. After this, ZnS and SiO
_A sintered target of the mixture of ₂ is sputtered with argon gas. The content of SiO ₂ is 17 mol%. The first interference layer 2 is formed by this sputtering. The thickness of the first interference layer 2 is 235 nm.

In a second step, a phase change layer 3 is formed on the first interference layer 2. The thickness of the phase change layer 3 is 13
nm. The phase change layer 3 is formed by sputtering a Ge ₂ Sb ₂ Te ₅ target with an argon gas.

In the third step, a second interference layer 4 is formed on the phase change layer 3. The second interference layer 4 is made of Zn
It is formed by sputtering a sintered target of a mixture of S and SiO ₂ with argon gas. The content of SiO ₂ is 17 mol%. The thickness of the first interference layer 2 is 45 n
m.

In the fourth step, a reflection layer 5 is formed on the second interference layer 4. The reflection layer 5 is formed by sputtering an Si target with an argon gas.
At this time, a small amount of B is added to the Si target.
The thickness of the reflection layer 5 is 70 nm.

In the fifth step, on the reflection layer 5,
The protection layer 6 is formed. The thickness of the protective layer 6 is 10 μm. The method for forming the protective layer 6 is as follows. First, an ultraviolet curable resin is spin-coated on the reflective layer 5. next,
By irradiating ultraviolet rays, the ultraviolet curable resin is cured.

As a sixth step, the information optical recording medium D
0 and the information optical recording medium D1 are adhered. Information optical recording medium D
0 and D1 are manufactured according to the first to fifth steps described above. The bonding method is based on hot melt. The information optical recording media D0 and D1 are adhered such that the transparent substrate 1 and the transparent substrate 11 are outside.

As a seventh step, the first stage of the medium is initialized. Specifically, the crystal states of phase change layer 3 and phase change layer 13 are made uniform. Specifically, the medium is irradiated with a laser beam having a wavelength of 830 nm. The shape of the laser beam spot is elliptical. 4. When irradiating with laser light;
Spin at a constant media linear velocity of 65 m / sec.

As an eighth step, the second stage of the medium is initialized. Specifically, a binary random pattern is recorded in an area of the medium where information is to be recorded. The recording of the random pattern is repeated ten times. [Comparative Experiment] The result of a comparative experiment showing the effectiveness of the information optical recording medium of the first embodiment will be described. The purpose of the comparative experiment is to confirm the effect of the information optical recording medium of the first embodiment and to verify the validity of the allowable range of the thickness of each layer inside the information optical recording medium.

Next, an experimental method will be described.

In one experiment, three characteristics of the information optical recording medium were verified.

The first characteristic is a recording / reproducing characteristic. The recording and reproduction characteristics were verified by the following procedure.

First, the recording frequency of the information optical recording medium is 8.3.
Record a 7 MHz square wave. The duty of the square wave is 50%. Next, a 2.12 MHz rectangular wave is overwritten and recorded. The duty of this rectangular wave is also 50%. Thereafter, the information optical recording medium is reproduced, and the C /
The N ratio and the erasure rate are measured.

Various conditions in the above recording / reproducing process are as follows.

The rotation speed of the information optical recording medium is 3600 rpm
m. The wavelength of the semiconductor laser is 680 nm.
The diameter of the spot of the laser beam on the phase change layer 3 is about 1.0 μm. Signal reproduction, tracking servo,
And the power of the laser beam in the focusing servo is 1.0 mW. At the time of signal recording, the power of the laser beam is controlled in two stages, high power and intermediate power.
The power of the laser beam at high power is 13 mW. The power of the laser beam at the time of the intermediate power is 5 mW. The rectangular wave is written at a position with a radius of 30 mm on the information optical recording medium. The medium linear velocity at this position is 11.3 m / sec.
c.

The second characteristic is a repetitive recording / reproducing characteristic.
The repeat recording / reproducing characteristics were verified by the following procedure. First,
8.37MHz square wave and 2.12M for information optical recording medium
Hz rectangular waves were alternately overwritten. Number of repetitions is 2
00 times. Thereafter, the recorded signal was reproduced to check whether or not the jitter was increased.

The third characteristic is high temperature and high humidity environment preservability. The high-temperature and high-humidity environmental preservability was verified by the following procedure. First, the information optical recording medium was heated at a temperature of 80 ° C. and a humidity of 80%.
For 500 hours. Thereafter, it was examined whether or not peeling or oxidation had occurred in each layer inside the information optical recording medium.

The above experiment was performed on a plurality of information optical recording media having different internal layer thicknesses. The results are shown below. [Experiment 1] The thicknesses of the first interference layer 2, the phase change layer 3, the second interference layer 4, and the reflection layer 5 of the information optical recording medium used in Experiment 1 were 235 nm, 13 nm, 45 nm,
And 70 nm. As a result of the experiment, the recording / reproducing characteristics
The C / N ratio was 54 dB, and the erasing rate was 25 dB. This result indicates that this medium has good recording / reproducing characteristics. Also, the repetitive recording / reproducing characteristics and the high-temperature / high-humidity environmental preservability were good. From the above results, it was found that the information optical recording medium of Experiment 1 was practically usable. [Experiment 2] The thicknesses of the first interference layer 2, the phase change layer 3, the second interference layer 4, and the reflective layer 5 of the information optical recording medium used in Experiment 2 are 250 nm, 13 nm, 45 nm,
And 70 nm. As a result of the experiment, it was found that the information optical recording medium of Experiment 2 can be put to practical use in any of the recording / reproducing characteristics, the repetitive recording / reproducing characteristics, and the high temperature / high humidity storage properties. [Experiment 3] The thicknesses of the first interference layer 2, the phase change layer 3, the second interference layer 4, and the reflection layer 5 of the information optical recording medium used in Experiment 3 are 220 nm, 13 nm, 45 nm,
And 70 nm. As a result of the experiment, it was found that the information optical recording medium of Experiment 3 was practically usable in any of the recording / reproducing characteristics, the repetitive recording / reproducing characteristics, and the high-temperature / high-humidity storage characteristics. [Experiment 4] The thicknesses of the first interference layer 2, the phase change layer 3, the second interference layer 4, and the reflection layer 5 of the information optical recording medium used in Experiment 4 are 240 nm, 13 nm, 15 nm,
And 70 nm. In this information optical recording medium, the phase change layer 3 could not be initialized stably. Therefore, it was found that the information optical recording medium of Experiment 4 was not practical. The wavelength of the laser beam used for the first-stage initialization of the phase change layer 3 is 830 nm. [Experiment 5] The thicknesses of the first interference layer 2, the phase change layer 3, the second interference layer 4, and the reflective layer 5 of the information optical recording medium used in Experiment 5 are 235 nm, 9 nm, 45 nm, and 70 nm. With this information optical recording medium, good recording / reproducing characteristics could not be obtained. Specifically, a good C
/ N ratio could not be achieved. Therefore, Experiment 5
Was found to be impractical. [Experiment 6] The thicknesses of the first interference layer 2, the phase change layer 3, the second interference layer 4, and the reflection layer 5 of the information optical recording medium used in Experiment 6 are 235 nm, 21 nm, 45 nm,
And 70 nm. With this information optical recording medium, good repetitive recording / reproducing characteristics could not be obtained. That is, as the rewriting was repeated, the jitter of the reproduced signal increased. Therefore, it was found that the information optical recording medium of Experiment 6 was not practical. [Experiment 7] The thicknesses of the first interference layer 2, the phase change layer 3, the second interference layer 4, and the reflective layer 5 of the information optical recording medium used in Experiment 7 are 190 nm, 13 nm, 45 nm,
And 70 nm. With this information optical recording medium, good repetitive recording / reproducing characteristics could not be obtained. That is, as the rewriting was repeated, the jitter of the reproduced signal increased. Therefore, it was found that the information optical recording medium of Experiment 7 was not practical. [Experiment 8] The thicknesses of the first interference layer 2, the phase change layer 3, the second interference layer 4, and the reflection layer 5 of the information optical recording medium used in Experiment 8 were 260 nm, 13 nm, 45 nm, respectively.
And 70 nm. With this information optical recording medium, good repetitive recording / reproducing characteristics could not be obtained. That is, as the rewriting was repeated, the jitter of the reproduced signal increased. Therefore, it was found that the information optical recording medium of Experiment 8 was not practical. [Experiment 9] The thicknesses of the first interference layer 2, the phase change layer 3, the second interference layer 4, and the reflection layer 5 of the information optical recording medium used in Experiment 9 are 235 nm, 13 nm, 45 nm,
And 40 nm. In this information optical recording medium, the stocking servo became unstable during the test of the recording / reproducing characteristics. Therefore, it was found that the information optical recording medium of Experiment 9 was not practical. [Experiment 10] The thicknesses of the first interference layer 2, the phase change layer 3, the second interference layer 4, and the reflection layer 5 of the information optical recording medium used in Experiment 10 are 235 nm, 13 nm, and 45 n, respectively.
m, and 110 nm. With this information optical recording medium, good recording / reproducing characteristics could not be obtained. Specifically, the recording sensitivity was significantly reduced. Therefore, Experiment 1
It has been found that the information optical recording medium of 0 is not practical. [Experiment 11] The thicknesses of the first interference layer 2, the phase change layer 3, the second interference layer 4, and the reflection layer 5 of the information optical recording medium used in Experiment 11 are 235 nm, 13 nm, and 30 n, respectively.
m, and 70 nm. In this information optical recording medium,
During the test of the recording / reproducing characteristics, the stocking servo became unstable. Therefore, it was found that the information optical recording medium of Experiment 11 was not practical. [Experiment 12] The thicknesses of the first interference layer 2, the phase change layer 3, the second interference layer 4, and the reflection layer 5 of the information optical recording medium used in Experiment 12 are 235 nm, 13 nm, and 110, respectively.
nm, and 70 nm. With this information optical recording medium, good recording / reproducing characteristics could not be obtained. Specifically, the recording sensitivity was significantly reduced. Therefore, Experiment 1
It was found that the information optical recording medium No. 2 was not practical.

Next, the analysis results of the above experiment will be described.

The table shown in FIG.
This is a summary of the results. FIG. 4 shows a rearrangement of the experimental results shown in this table. This rearrangement was performed according to the following procedure.

In the first step, the columns indicating the thickness of each layer were first rearranged. That is, in FIG.
In the order of the interference layer 2, the phase change layer 3, the second interference layer 4, and the reflection layer 5, in FIG. 4, the reflection layer 5, the second interference layer 4, the phase change layer 3, and the first interference layer 2 are shown. In order.

In the second step, the results of each experiment were rearranged in the order of the thickness of the reflective layer 5.

In the third step, only data in which the thickness of the reflection layer 5 is 50 to 100 nm were selected and set as a set 1. Data belonging to the set 1 is indicated by S1 in FIG.

In the fourth step, only the data belonging to the set 1 were rearranged in the order of the thickness of the second interference layer 4.

In the fifth step, only data belonging to the set 1 and having a thickness of the first interference layer 2 of 40 to 100 nm was selected and set as the set 2. Data belonging to the set 2 is indicated by S2 in FIG.

In the sixth step, only data belonging to the set 2 and having a thickness of the phase change layer 3 of 10 to 20 nm was selected and set as the set 3. Data belonging to set 3
This is indicated by S3 in FIG.

In the seventh step, only data belonging to the set 3 and having a thickness of the first interference layer 2 of 200 to 250 nm was selected and set as the set 4. Data belonging to the set 4 is indicated by S4 in FIG.

The set 4 has a thickness of the first interference layer 2, the phase change layer 3, the second interference layer 4, and the reflection layer 5 of 20
It consists of only data included in the range of 0 to 250 nm, 10 to 20 nm, 40 to 100 nm, and 50 to 100 nm. Then, referring to FIG. 4, only the information optical recording medium used in the experiment belonging to the set 4 can be put to practical use. Accordingly, it can be seen that the information optical recording medium that can be put to practical use has the thickness of each layer belonging to this range. [Effects of the first embodiment] As described above, in this embodiment,
The information optical recording medium D is configured such that the reflection layer 5 contains Si, and the first interference layer 2, the phase change layer 3, the second interference layer 4, and the reflection layer 5 each have a thickness of 200. ~ 25
0 nm, 10-20 nm, 40-100 nm and 50
It is configured to fall within the range of 100 nm. For this reason, the information optical recording medium D of the present embodiment can achieve the effect that the jitter of the recording / reproducing signal does not increase even if writing is repeatedly performed. [Second Embodiment] Next, a second embodiment of the present invention will be described with reference to the drawings.
An example will be described. This embodiment is characterized in that a protective layer 8 is provided under the transparent substrate 1. In other respects, the configuration of the present embodiment is the same as that of the first embodiment.

Referring to FIG. 5, in the information optical recording medium D of the present embodiment, a protective layer 8 is provided under the transparent substrate 1. The material of the protective layer 8 is, for example, SiO2.

The features of this embodiment may be applied to the information optical recording medium D shown in FIG. That is, the protective layer 8 may be provided on the transparent substrate 1 and the transparent substrate 11 of the information optical recording medium D in FIG.

According to the structure of this embodiment, in addition to the effects of the first embodiment, the effect that the transparent substrate 1 can be protected is achieved.

[0069]

As described above, the present invention employs the reflective layer 5 containing Si, further comprises the first interference layer 2, the phase change layer 3,
Since the information optical recording medium is configured such that the thicknesses of the second interference layer 4 and the reflective layer 5 are within a predetermined range, the jitter of the recording / reproducing signal does not increase even if writing is performed repeatedly. The effect can be achieved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram showing another embodiment of the first embodiment of the present invention.

FIG. 3 is a diagram showing the results of a comparative experiment for verifying the effects of the first embodiment of the present invention.

FIG. 4 is a diagram showing the results of a comparative experiment for verifying the effects of the first embodiment of the present invention.

FIG. 5 is a diagram showing a second embodiment of the present invention.

[Explanation of symbols]

 D, D1, D2 Information optical recording medium 1 Transparent substrate 2 First interference layer 3 Phase change layer 4 Second interference layer 5 Reflective layer 6 Protective layer 7 Adhesive layer 8 Protective layer 11 Transparent substrate 12 First interference layer 13 Phase change layer 14 Second interference layer 15 Reflective layer 16 Protective layer 18 Protective layer

 ────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Shu Shu Obata 5-7-1 Shiba, Minato-ku, Tokyo NEC Corporation (56) References JP-A-4-263133 (JP, A) JP-A-4 -263134 (JP, A) JP-A-3-5929 (JP, A)

Claims (2)

(57) [Claims] 1. A transparent substrate, a first interference layer provided above the transparent substrate and containing a mixture of ZnS and SiO _2, and a Ge ₂ Sb ₂ Te provided above the first interference layer
₅ , a second interference layer provided above the phase change layer and containing a mixture of ZnS and SiO _2, and a reflective layer provided above the second interference layer and containing Si. an information optical recording medium including the thickness of the phase change layer is from 10 to 20 nm, the second
2. The thickness of the interference layer is 40 to 100 nm,
The first interference layer, wherein a thickness of the layer is 50 to 100 nm;
Characterized by a thickness of 200 to 250 nm
Information optical recording medium. 2. At least one of the reflection layer and the transparent substrate
2. The method according to claim 1, wherein a protective layer is provided on one side.
Information optical recording medium.