JP2650507B2 - Optical information recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording medium, and in particular, to a direct reproduction (Dire) using a conventional read-only disk, so-called compact disk (CD) drive.
The present invention relates to a novel optical information recording medium capable of performing ct read after write (DRAW) and optical recording.

[0002]

2. Description of the Related Art Optical discs include a read-only type and an optical recordable type. The read-only type is already widely used as a video disk, an audio disk, and a disk drive for a large-capacity computer.
Among them, compact discs (CDs) are widely used for audio reproduction of music and the like.

A compact disk (CD) is a CD-formatted EFM (Eight to Fourteen Modulatio).
n) Signal holes (pits) are transferred to a substrate made of plastic, and a reflective film and a protective film made of a metal such as aluminum are provided thereon for practical use. Reading of information from a CD is performed by irradiating a semiconductor laser beam to an optical disk, and a CD format signal or the like is read by a change in reflectance depending on the presence or absence of pits. At this time, the conventional CD has a high reflectivity of 70% or more and 6
It is characterized by having a modulation degree of 0% or more. However, such a read-only CD has a drawback that information cannot be recorded / edited, and therefore development of an optically recordable CD is desired. I was

[0004] Software, data files, still images, and other files are also stored in CD-ROMs (read-only).
Optically recordable optical disks for y memory) or CD-I (interactive) have been desired.

[0005] On the other hand, typical optical recording types include:
There are drilling type, magneto-optical type and phase change type. Examples of the perforated type include a TeSeF alloy (JP-A-63-18218).
8) Alternatively, a recording layer such as a dye is used, and is locally heated by laser light irradiation to form holes or recesses. In practice, however, such a punch type has a void on the recording layer. Must. For this reason, the recording layers of the two disks face each other and are bonded using a spacer to form an air gap between the recording layers. Therefore,
As a matter of course, a disk having such a laminated structure cannot be mounted on a CD drive that is currently widely used.

In the magneto-optical type, recording and erasing are performed according to the direction of magnetization of the recording layer, and reproduction is performed by using a magneto-optical effect. It is possible.

[0007] On the other hand, the phase change type is common to the CD in that recording and erasing are performed by a difference in reflectance before and after the phase change. The phase change type is classified into a write-once type, in which information is stored semi-permanently once recorded, and a rewritable type, in which the recorded information can be erased. In the phase change type recording layer, Te-Ge-Sb (Japanese Patent Application Laid-Open No. 63-225934) and Te-Ge-Bi (Japanese Patent Application Laid-Open No.
3-225935), In-Sb-Te (Japanese Unexamined Patent Application Publication No. 1-1)
However, since the absorption coefficient (imaginary part of the complex refractive index) of these recording layer thin films is as large as about 1.0 or more, the reflectance is only 60% at most. Therefore, there is no complete compatibility with CDs.

As an optical disk for recording a CD format signal, an optical disk having a recording layer made of a dye or a polymer containing a dye on a substrate and an optical information recording method using the optical disk have been proposed ( JP-A-61-237239 and 61-23944
3) However, these optical discs cannot be said to have practically sufficient performance in terms of reflectance, modulation degree of a reproduction signal, and reproduction light intensity.

[0009]

As described above, conventionally, optical recording is possible, and it is compatible with the most widely used read-only type CDs and CD-ROMs at present.
No optical information recording medium that can be directly reproduced by a dedicated drive is provided.

The present invention has been made in view of the above circumstances, and has as its object to provide an optical information recording medium capable of optical recording and compatible with an optical disk such as a read-only type CD or CD-ROM. And

[0011]

According to a first aspect of the present invention, there is provided an optical information recording medium comprising a recording layer, a dielectric layer, and a metal reflection layer sequentially laminated on a substrate. the amorphous state induced performs a phase change by the recording of information between the crystalline state, by lowering the change of reflectivity associated with a phase change, an optical information recording medium for reading information, the The recording layer has a thickness of 200 to 1000 °, has a reflectance of 70% or more read by a laser beam through a substrate in a state before the above-described phase change due to recording, and has a complex refraction of the recording layer. Rate n * = n-ik
Before the phase change caused by the above-mentioned recording, k =
It takes a value of 0.1 to 1.0, and in the state after the phase change, k> 0.5 and changes to a larger value than before the phase change, and n is the same before and after the phase change. It is characterized by not being a value.

According to a second aspect of the present invention, in the optical information recording medium according to the first aspect, the recording layer is formed of Sb _{1 -x} Se _x (x = 0.5
5 to 0.65).

According to a third aspect of the present invention, in the optical information recording medium according to the first aspect, the recording layer is made of Ge _{1 -y} Te _y (y = 0.4
5 to 0.55).

According to a fourth aspect of the present invention, in the optical information recording medium according to the first to third aspects, the reflectance read through the substrate before the phase change is 70% or more and less than 80%, and the reflectance after the phase change is changed. The reflectance is less than 50%.

That is, the present inventors have made it possible to perform optical recording by a local phase change of a recording layer without physical deformation such as perforation and swelling, and to obtain a reflectance of 70% or more and a sufficient contrast. As a result of diligent research on the recording layer material and the layer configuration having the above, the complex refractive index of the recording layer in an optical information recording medium comprising a substrate and a recording layer, a dielectric layer and a metal reflective layer provided thereon The present inventors have found that the above object can be achieved by specifying the absorption coefficients k and n among n * = n−ik, and completed the present invention.

[0016]

The present invention will be described below in detail.

FIG. 1 is a schematic sectional view showing an embodiment of the optical information recording medium of the present invention. In FIG. 1, 1 is a substrate, 2 is a recording layer, 3 is a dielectric layer, and 4 is a metal reflection layer. In the present invention, on this recording medium, to prevent thermal deformation of the recording layer, to improve the mechanical strength,
Further, a hard coat layer made of a thermosetting or photocurable resin may be provided.

As a constituent material of the substrate 1, any material that is transparent to the wavelength of a semiconductor laser, such as glass, acrylic resin, or polycarbonate resin, may be selected from those conventionally used as substrate materials. Can be used, but in terms of compatibility with CDs,
Polycarbonate resins are preferred.

As the recording layer 2, an inorganic thin film which can be generally formed by vapor deposition or sputtering, which is in an amorphous state immediately after film formation, and in which a crystallization bit having a low reflectance is formed by recording is applied. I do. The complex refractive index of the amorphous state before the phase change of the recording layer _{n a * = n a -ik a} , the complex refractive index of the crystal state after the phase change n _c * = n _c -ik _c
Then, n _a and n _c are generally in the range of 3.0 to 6.0 for a usual inorganic thin film of a metal or semiconductor. k _a =
0.1 to 1.0 means that the recording layer thickness is 200 to 1
It is necessary to obtain a reflectance of 70% at 000 °. k _a
If> 1.0, it is necessary to make the thickness of the recording layer thinner than 200 °, and it is difficult to obtain stability over time and sufficient contrast. When k _a <0.1, the recording sensitivity becomes extremely poor, and recording cannot be performed with a normal semiconductor laser. On the other hand, unless k _c > 0.5 after the phase change, the decrease in reflectance is insufficient and it is difficult to obtain contrast. Also, k
Unless _a <k _c , no contrast can be obtained due to a decrease in reflectance.

Here, with reference to FIGS. 2 and 3, attention is paid to the dependency of the reflectance on the thickness of the recording layer, and the initial reflectance is 70%.
Consider a case where a film thickness that provides a large contrast is selected as described above. In the case of n _a = n _c shown in FIG. 2, since only the decrease in the reflectance with the increase in the absorptance occurs, k _a
If the difference between k and _c is not large, it is difficult to obtain contrast. However, in the example of n _c> n _a as shown in FIG. 3, the reflectance minimum point is shifted before and after the phase change, it can be obtained easily large contrast. For n _c <n _a is the same. Therefore, in the present invention, and n _a ≠ n _c. It should be noted that the above conditions regarding the optical properties are not necessarily satisfied in a completely amorphous state or a crystalline state, but are satisfied in a state where the amorphous state and the crystalline state are mixed or in a so-called microcrystalline state. May be.

The recording layer materials satisfying the above optical properties include, for example, Ga, Al, Ge, Si, Se, Te, B
It can be obtained by optimizing the composition of an alloy composed of elements such as i and Sb. The crystallization temperature of the alloy is preferably 100 ° C. or higher from the viewpoint of stability over time, and is preferably lower than 300 ° C. from the viewpoint of recording sensitivity. Above all, Sb _1-x Se _x (x = 0.55 to 0.65) or Ge _1-y T _y (y = 0.45 to 0.55) not only can satisfy the above-mentioned optical properties but also has a vacuum. Evaporation method,
While a stable amorphous state is formed by any of the sputtering methods, it can be sufficiently crystallized with a pulse of several hundred nsec or less during laser light irradiation, and is suitable for optical recording.

In forming the alloy thin film having such a composition, an alloy whose composition is adjusted in advance may be used, or a multi-source evaporation or sputtering method may be used. Formed in this way
The thickness of the recording layer to be formed is 200 to 1000 °. That is, if the thickness of the recording layer is less than 200 °, it is difficult to obtain a change in reflectance before and after recording, that is, contrast, and if it exceeds 1000 °, the heat capacity of the recording layer is large and the recording sensitivity decreases.
In particular, the recording layer _{thickness, Sb 1-x Se x (} x = 0.55~
0.65), 600-700 °, Ge _1-y Te _y
At (y = 0.45 to 0.55), the angle is preferably 400 to 470 °. Sb _1-x Se _x (x = 0.55 to
0.65) or Ge _x Te _1-x (x = 0.45 to 0.5
5) has an extremely stable amorphous state at room temperature with a crystallization temperature of about 200 ° C., and enables high-speed crystallization during laser beam irradiation.

The recording layer Sb-Se or Ge-Te
A third element can be added to the alloy thin film as needed to improve the stability over time, recording sensitivity, optical properties, and the like. In this case, Ge (Sb-
Se), Te (Sb-Se), Sb (Ge
-For Te), Se (for Ge-Te), Au, A
One or more of g, Cu, Pt, Pd, Co, Ni, Ti and the like can be mentioned, but it is not limited to these elements. The amount of addition of these third elements is 5 atomic% with respect to the total amount of Sb-Se or Ge-Te as the main component.
It is preferable that the content be less than or equal to 5 atomic% when there are two or more third elements. Specific actions of these third elements include, for example, Au, Ag, Pe, P
d, Co, etc. increase the crystallization speed and shorten the recording time.
Bi, Se, Ge, Sb, and the like act on stabilization of the amorphous state.

The dielectric layer 3 is formed first for the purpose of controlling the reflectance and the contrast by the interference effect. In addition, the presence of the dielectric layer 3 also has the effect of widening the allowable range of the recording layer thickness. And
The dielectric layer 3 provided between the recording layer 2 and the reflection layer 4 has an effect of preventing heat from escaping from the recording layer 2 to the reflection layer 4 and improving recording sensitivity. Further, it has an effect of preventing deformation and oxidative deterioration of the recording layer 2 as a protective layer. Various combinations of the refractive index and the film thickness of the dielectric layer 3 used in the present invention are possible, and the material is appropriately determined in consideration of the refractive index, the thermal conductivity, the chemical stability, and the mechanical strength. Generally, Mg, Ca, Sr, Y, La, Ce, H, which are highly transparent and have a high melting point.
o, Er, Yb, Ti, Zr, Hf, V, Nb, Ta,
Oxides such as Zn, Al, Si, Ge and Pb, sulfides,
A nitride or a fluoride such as Ca, Mg, and Li can be used. These oxides, sulfides, nitrides, and fluorides do not always need to have a stoichiometric composition, and it is also effective to control the composition for controlling the refractive index and the like, or to use a mixture.

In the present invention, the dielectric layer 3 preferably has a refractive index of 2 to 3, and the material is preferably tantalum oxide or silicon nitride. The thickness of the dielectric layer 3 is 100 to 5000 °, particularly 1000 to 130 °.
It is preferably in the range of 0 °. If the thickness is less than 100 °, deformation of the recording layer 2 due to beam irradiation cannot be prevented,
If the thickness is more than 5000 °, cracks are likely to occur.

The reflection layer 4 functions to increase the contrast of the reflectance and to promote the diffusion of the thermal energy absorbed by the recording layer 2. As a constituent material of the reflective layer 4, Au, Ag, Cu, Al or an alloy mainly composed of these metals, particularly Au, is preferable.
It is preferably in the range of 00-5000 °, preferably 300-5000 °. If the film thickness is less than 100 °, the reflectance is too low, and if it exceeds 5000 °, the film formation time and cost are disadvantageous.

The design of the layer configuration of the optical information recording medium of the present invention will be described. Basically, the layer configuration shown in FIG. 1 is determined while paying attention to the interference effect.
At this time, the reflectance before the phase change is 7 due to CD compatibility.
0% or more is required. However, if the reflectance before the phase change exceeds 80%, the light energy absorbed by the recording layer decreases, and the recording sensitivity becomes extremely poor. Therefore, it is desirable that the reflectance is less than 80%. On the other hand, the reflectance after the phase change is preferably less than 50% in order to obtain a sufficient contrast. Accordingly, in the layer structure as shown in FIG. 1, the reflectance in the amorphous state read out by the laser beam through the substrate is 70% or more, preferably 70% or more and less than 80%, and the reflectance in the crystalline state The thickness and refractive index of each layer are selected so that the reflectance is less than 50%.

[0028]

EXAMPLES The present invention will be described more specifically with reference to Experimental Examples, Examples and Comparative Examples, but the present invention is not limited to the following Examples unless it exceeds the gist.

Experimental Example 1 As a specific example of the layer structure design, an Sb ₄₀ Se ₆₀ recording layer, a dielectric layer made of tantalum oxide, and a reflective layer made of Au were used to express the complex refractive indexes of these materials. The calculation was performed using the actual measurement value or the literature value at a wavelength of 780 nm as shown in FIG.

[0030]

[Table 1]

FIGS. 4 to 8 show the reflectivity before and after crystallization when the thickness of the upper dielectric layer is changed for various recording layer thicknesses of 1000 ° or less. However, the reflectance is a value when light enters through the substrate. In each of the figures, the requirement of claim 4 is satisfied in the range of the thickness of the dielectric layer indicated by the triangle. As shown in the figure, when the recording layer thickness is 800 ° or more, a reflectance of 70% or more in the amorphous state cannot be secured. On the other hand, if the thickness of the recording layer is set to 500 ° or less, the requirement of claim 4 is satisfied only in an extremely narrow region, and the film thickness dependence of the reflectance in this region is steep, which is not preferable in manufacturing. Only when the recording layer thickness is 600 to 700 °, the requirement of claim 4 is satisfied at a relatively wide dielectric film thickness. Note that the results described here are valid for all dielectrics having a refractive index of about 2.1. Specifically, ZnS, Si ₃
N _{4 and the} like. Further, even if the optical constants used here slightly change, the same result is obtained.

Experimental Example 2 The Ge ₅₀ Te ₅₀ recording layer was evaluated in the same manner as in Experimental Example 1. Note that the complex refractive index of each material was calculated using an actual measurement value at a wavelength of 780 nm as shown in Table 2.

[0033]

[Table 2]

FIGS. 9 to 13 show the dependence of the reflectance before and after crystallization on the dielectric film thickness for various recording layer thicknesses. The reflectivity was controlled by adjusting the thickness of the tantalum oxide layer on the horizontal axis so as to satisfy the requirement of claim 4, but the above conditions were satisfied when the thickness of the recording layer was less than 400 ° and more than 470 °. It is not possible. Recording layer thickness 400 ~
Only at 470 °, it can be seen that the condition regarding the reflectance is satisfied. At this time, the thickness of the tantalum oxide layer is 10
It must be between 00 and 1300 °. Note that the results obtained here hold for all dielectrics having a refractive index of about 2.1. Specific examples include ZnS and Si ₃ N ₄ .

Example 1 and Comparative Example 1 An amorphous film of Sb ₄₅ Se ₅₅ was formed on a glass substrate and a polycarbonate resin substrate by sputtering, respectively.
Then, Ta was reactively sputtered in a mixed gas atmosphere of Ar and oxygen to form a tantalum oxide film having a thickness of 1800 °. Finally, a film of Au was formed to a thickness of 2,000 mm by the sputtering method to prepare a recording medium having a layer structure shown in FIG.

Also, as Comparative Example 1, a recording medium was produced in the same manner except that no tantalum oxide layer was formed. However, in order to make the reflectance before recording 70% or more, the recording layer thickness was set to 200 ° or 1000 °. In this case, a hard coat layer is indispensable to prevent deformation of the recording layer.

The temperature of the sample using the glass substrate was raised, and the crystallization temperature was evaluated at the temperature at which the reflectance sharply decreased. As a result, the temperature was about 220 ° C. in both Example 1 and Comparative Example 1.
Table 3 shows the reflectance before and after crystallization. In both Example 1 and Comparative Example 1, the reflectance before crystallization was 70% or more and less than 80%, and the reflectance after crystallization was less than 50%.

The complex refractive index of the recording layer before crystallization is as follows:
3.8-0.25i, and the refractive index after crystallization is 4.7.
-0.8i. However, all of the above measurements were performed using a semiconductor laser having a wavelength of 780 nm.

[0039]

[Table 3]

Next, the sample using the polycarbonate resin substrate was rotated at a linear velocity of 1.4 m / s, irradiated with a semiconductor laser beam having a wavelength of 780 nm, and recorded at a frequency of 200 kHz with various duty pulse waveforms. Ra represents a reproduction signal level before recording, and Rc represents a signal level of a portion of the waveform of the reproduction signal after recording where the reflectance is most reduced.
Contrast was defined by the following equation.

[0041]

(Equation 1)

When recording was performed with a maximum laser output of 15 mw, a maximum contrast of 60% was obtained in Example 1. On the other hand, in Comparative Example 1, the maximum was 10 to 2 at 15 mw.
Only 0% contrast was obtained. This is presumably because heat escaped from the recording layer to the reflective layer so much that sufficient crystallization could not be achieved. In Example 1, a C / N ratio of 50 dB was obtained.

Example 2 On a glass substrate and a polycarbonate resin substrate, Sb ₄₅
An amorphous film of Se ₅₅ was formed to a thickness of 650 ° by a sputtering method, and then Ta was reactively sputtered in a mixed gas atmosphere of Ar and oxygen to form a tantalum oxide film having a thickness of 1000 °. Finally, Au was also added by sputtering method.
A recording medium having a layer structure shown in FIG.

The temperature of the sample using the glass substrate was raised, and the crystallization temperature was evaluated at a temperature at which the reflectance sharply decreased. 72% reflectance before crystallization,
A reflectance of 45% after crystallization was obtained. The complex refractive index of the recording layer before crystallization was 3.8-0.25i, and the refractive index after crystallization was 4.7-0.8i. However,
All of the above measurements were performed using a semiconductor laser having a wavelength of 780 nm.

Next, the sample using the polycarbonate resin substrate was rotated at a linear velocity of 1.4 m / s, irradiated with a reaction body laser beam having a wavelength of 780 nm, and recording was performed with a pulse waveform of 500 kHz and various duties. . Ra represents a reproduction signal level before recording, and Rc represents a signal level of a portion of the waveform of the reproduction signal after recording where the reflectance is most reduced.
Defined by the formula shown in Example 1, the laser power 15 mw
As a result, a maximum contrast of 50% was obtained. A C / N ratio of 50 dB was obtained.

COMPARATIVE EXAMPLE 2 In Example 1, the recording layer was formed in a thickness of 100 to 1500.degree. In steps of almost 100.degree., And an Au layer was directly formed to a thickness of 2000.degree. Without a tantalum oxide layer. Among these, a medium having a reflectance of 70 to 80% in an amorphous state and a reflectance of less than 50% after crystallization was obtained at a recording layer thickness of around 200 ° and 1000 °. On the other hand, recording was attempted while rotating at a linear velocity of 1.4 m / s, but a contrast of only 10 to 20% was obtained even with a maximum recording power of 15 mw. This is presumably because heat escaped from the recording layer to the reflective layer so much that sufficient crystallization could not be achieved. Further, in a layer configuration not using tantalum oxide, the variation in the reflectance is large with respect to the variation in the thickness of the recording layer, and it is difficult to obtain a uniform reflectance.

Example 3 An amorphous film of Ge ₄₅ Te ₅₅ was respectively formed on a glass substrate and a polycarbonate resin substrate by a sputtering method.
Then, Ta was reactively sputtered in a mixed gas atmosphere of Ar and oxygen to form a 1300-mm-thick tantalum oxide film. Finally, a film of Au was formed to a thickness of 2,000 mm by the sputtering method to prepare a recording medium having a layer structure shown in FIG.

The temperature of the sample using the glass substrate was raised, and the crystallization temperature was evaluated at a temperature at which the reflectance sharply decreased. At a wavelength of 780 nm,
A reflectance of 75% before crystallization and a reflectance of 47% after crystallization were obtained. The complex refractive index before crystallization has a wavelength of 780 nm.
4.0-0.9i, and 5.4-3.6 after crystallization.
i.

Next, the sample using the polycarbonate resin substrate was rotated at a linear velocity of 1.4 m / s, irradiated with a semiconductor laser beam having a wavelength of 780 nm, and recorded at a frequency of 200 kHz with various duty pulse waveforms. Ra represents a reproduction signal level before recording, and Rc represents a signal level of a portion of the waveform of the reproduction signal after recording where the reflectance is most reduced.
Contrast Defined by the formula shown in Example 1, when recording was performed with a laser power of 12 mw, a maximum contrast of 40% was obtained. A C / N ratio of 45 dB was obtained.

Example 4 A thin film having a composition of Sb ₄₀ Se ₆₀ was formed on a glass substrate at 600 ° C.
Alternatively, vacuum evaporation was performed to a thickness of 700 °, and tantalum oxide films having various thicknesses shown in Table 4 were formed thereon by a reactive sputtering method, and gold was further vacuum-deposited thereon to a thickness of 2000 °. Note that the composition of the recording layer was determined by the X-ray fluorescence method, and there was a variation of about ± 3%.

Table 4 shows the reflectance and contrast read from the substrate side before and after crystallization in the above various layer constitutions.

[0052]

[Table 4]

Nos. 1 to 5 in Table 4 all satisfy the requirements of the present invention, and substantially agree with the calculated values in FIGS. 6 and 7 within the range of an experimental error (± 5%). In addition, a maximum of 71% was obtained as the contrast. The complex refractive index of the recording layer before crystallization was 3.8-0.25i, and after the crystallization was 4.7-0.8i.

Comparative Example 3 A Ge ₁₂ Sb ₄₀ Te ₄₈ film was used as the recording layer.
With a film thickness of 0 ° or more, it was not possible to obtain a reflectance of 70% or more in an amorphous state even with a reflective layer structure. This is because the complex refractive index of the recording layer is 3.8- before crystallization.
2.0i, and 5.5-3.8i after crystallization, because the absorption coefficient in the amorphous state is too large. It can be concluded from the calculation result in consideration of the interference effect that a reflectance of 70% or more cannot be obtained unless the value is set to a value. At such a film thickness, the reflectance after crystallization is 50
It can also be concluded from a simple calculation that it is difficult to make it less than%.

According to the results of the study by the present inventors, the Ge—Sb—Te alloy film recording layer having the composition disclosed in Japanese Patent Application Laid-Open Nos. 62-209742 and 63-225934 has an amorphous state. No recording layer having an absorption coefficient of 1.0 or less was obtained.

[0056]

As described in detail above, according to the optical information recording medium of the present invention, a high-performance optical information recording medium capable of optical recording and directly reproducible by a CD-only drive is provided. .

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing one embodiment of an optical information recording medium of the present invention.

FIG. 2 is a graph showing the dependency of the reflectance on the thickness of a recording layer.

FIG. 3 is a graph showing the dependency of the reflectance on the thickness of a recording layer.

FIG. 4 shows the results of Experimental Example 1 (recording layer thickness 400 °).
FIG.

FIG. 5 shows the results of Experimental Example 1 (recording layer thickness 500 °).
FIG.

FIG. 6 shows the results of Experimental Example 1 (recording layer thickness: 600 °).
FIG.

FIG. 7 shows the results of Experimental Example 1 (recording layer thickness 700 °).
FIG.

FIG. 8 shows the results of Experimental Example 1 (recording layer thickness 800,
FIG.

FIG. 9 shows the results of Experimental Example 2 (recording layer thickness 400 °).
FIG.

FIG. 10 shows the results of Experimental Example 2 (recording layer thickness 43).
(Case of 0 °).

FIG. 11 shows the results of Experimental Example 2 (recording layer thickness 45).
(Case of 0 °).

FIG. 12 shows the results of Experimental Example 2 (recording layer thickness 47).
(Case of 0 °).

FIG. 13 shows the results of Experimental Example 2 (recording layer thickness 50).
(Case of 0 °).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Recording layer 3 Dielectric layer 4 Reflection layer

Claims (4)

(57) [Claims] 1. A phase change between an amorphous state and a crystalline state induced in a recording layer by laminating a recording layer, a dielectric layer, and a metal reflection layer in this order on a substrate. An optical information recording medium from which information is read out by reading the information due to a decrease in the reflectance accompanying the phase change, wherein the thickness of the recording layer is 200 to 1000 ° In a state before the change occurs, the reflectance read by the laser beam through the substrate is 70% or more, and the complex refractive index n * = n-ik of the recording layer is changed before the phase change due to the recording. K = 0.1 in the state of
~ 1.0, and in the state after the phase change, k>
0.5 and a value larger than before the phase change,
An optical information recording medium wherein n does not become the same before and after the phase change. 2. The recording layer according to claim 1, wherein said recording layer is Sb _1-x Se _x (x = 0.55).
The optical information recording medium according to claim 1, wherein the optical information recording medium comprises: -0.65). 3. The recording layer according to claim 1, wherein Ge _1-y Te _y (y = 0.45)
2. The optical information recording medium according to claim 1, wherein the optical information recording medium comprises: 4. The reflectance read out through the substrate before the phase change is 70% or more and less than 80%, and the reflectance after the phase change is less than 50%. 3
The optical information recording medium according to any one of the above items.