JPH04228126A - Optical information recording medium - Google Patents

Abstract

PURPOSE:To provide an optical information recording medium capable of optically recording and interchangeable with a reproduction-only CD, a CD-ROM, etc. CONSTITUTION:A recording layer 2, a dielectric layer 3 and a metallic reflecting layer 4 are successively laminated on a substrate 1 to constitute the optical information recording medium. Information is recorded by the phase transition between the amorphous and crystalline states induced in the recording layer by the irradiation with a laser beam, and the information is read by a decrease in reflectivity resulting from the phase transition. Before the phase transition is caused by the recording, the reflectivity read by the laser beam through the substrate is >=70%. The complex index of refraction n*=n-ik is k=0.1-1.0 before the phase transition by the record and k>0.5 after the phase transition which is larger than before the phase transition, and n is not the same value before and after the phase transition. In formation is recorded by the phase transition between amorphous and crystalline states induced in the recording layer by the irradiation with a laser beam, and the information is read by a decrease in reflectivity resulting from the phase transition.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to optical information recording media, and in particular to direct playback (Di
rect read after write:DRA
The present invention relates to a novel optical information recording medium which is capable of W) and which is also capable of optical recording.

0002

2. Description of the Related Art Optical discs include read-only types and optically recordable types. Playback-only drives are already widely used for video discs, audio discs, and even large-capacity computer disc memories. Among these, compact discs (CDs) are widely put into practical use for audio playback such as music.

[0003] Compact discs (CDs) are CD-formatted EFM (Eight to Four) discs.
It is put into practical use by transferring the holes (pits) of the een Modulation signal onto a substrate made of plastic, and then providing a reflective film and a protective film made of metal such as aluminum thereon. Information from a CD is read by irradiating the optical disc with a semiconductor laser beam, and CD format signals and the like are read based on changes in reflectance depending on the presence or absence of pits. In this case, conventional CDs are characterized by having a high reflectance of 70% or more and a modulation degree of 60% or more, but such read-only CDs have the disadvantage that information cannot be recorded or edited. Therefore, it has been desired to develop an optically recordable CD.

[0004] Files such as software, data files, and still images are also stored on CD/ROM (read
only memory) or CD-I (inte
There has been a desire for an optically recordable optical disc for use in the Ractive.

On the other hand, typical optical recordable types include:
There are drilling types, magneto-optical types and phase change types. For example, TeSeF alloy (Japanese Patent Laid-Open No. 63-182188
) or dye is used, and is locally heated by laser beam irradiation to form holes or recesses.
In practice, such a punching die requires the presence of voids on the recording layer. For this reason, the recording layers of two disks are faced to each other and bonded together using a spacer to form an air gap between the recording layers. Therefore, as a matter of course, a disc with such a laminated structure cannot be installed in the currently popular CD drive.

Furthermore, since the magneto-optical type performs recording and erasing depending on the direction of magnetization of the recording layer, and also performs reproduction using the magneto-optic effect, conventional CD drives that utilize the difference in reflectance may not be able to reproduce the data. It is possible.

On the other hand, the phase change type is similar to the CD in that recording and erasing are performed based on the 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 it is recorded, and a rewritable type in which the recorded information can also be erased, but the configurations of the media have many things in common. In the phase change type recording layer, Te-Ge-Sb (JP-A-63-225934) and Te-Ge-Bi (JP-A-63-225934) are used.
3-225935), In-Sb-Te (JP-A-1-1
00748), etc., but since the absorption coefficient (imaginary part of the complex refractive index) of these recording layer thin films is large, approximately 1.0 or more, the reflectance can only be 60% at most. Therefore, it is not completely compatible with CD.

By the way, as an optical disk for recording CD format signals, 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 61-237239, 61-239443)
However, these optical discs also have different reflectance, modulation degree of playback signal,
It cannot be said that it has practically sufficient performance in terms of resistance to reproduction light intensity.

[0009]

[Problems to be Solved by the Invention] As mentioned above, in the past, optical recording is possible, and the CD is compatible with the currently most popular read-only type CD, CD-ROM, etc.
Optical information recording media that can be directly played back with a dedicated drive are not available.

SUMMARY OF THE INVENTION In view of the above-mentioned conventional circumstances, an object of the present invention is to provide an optical information recording medium that is capable of optical recording and is compatible with read-only optical discs such as CDs and CD-ROMs. shall be.

[0011]

[Means for Solving the Problems] The optical information recording medium according to claim 1 comprises a recording layer, a dielectric layer and a metal reflective layer sequentially laminated on a substrate, and the recording layer is irradiated with a laser beam. An optical information recording medium in which information is recorded by an induced phase change between an amorphous state and a crystalline state, and information is read out by a decrease in reflectance accompanying the phase change, the medium comprising: In a state before a phase change occurs due to recording, the reflectance read out by a laser beam through the substrate is 70% or more, and the complex refractive index n*=
n-ik takes a value of k = 0.1 to 1.0 in the state before the phase change as recorded above, and k > 0.5 in the state after the phase change and is larger than before the phase change. The phase change is characterized in that n does not have the same value before and after the phase change.

[0012] The optical information recording medium according to claim 2 is the optical information recording medium according to claim 1, wherein the recording layer is Sb1-xSex (x=0
．． 55 to 0.65).

[0013] The optical information recording medium according to claim 3 is the optical information recording medium according to claim 1, wherein the recording layer has Ge1-yTey (y=0
．． 45 to 0.55).

[0014] In the optical information recording medium according to claim 4, according to any one of claims 1 to 3, 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 It is characterized in that the reflectance is less than 50%.

That is, the present inventors have discovered that optical recording is possible by local phase change of the recording layer without physical deformation such as holes or blistering, and that the recording layer has a reflectance of 70% or more and sufficient contrast. As a result of intensive research on recording layer materials and layer configurations that have a The present invention has been completed by discovering that the above object can be achieved by specifying the absorption coefficients k and n out of n*=n-ik.

[0016]

[Operation] The present invention will be explained in detail below.

FIG. 1 is a schematic cross-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 reflective layer. In addition, in the present invention, on this recording medium, in order to prevent thermal deformation of the recording layer and improve mechanical strength,
Furthermore, a hard coat layer made of thermosetting or photosetting resin may be provided.

The constituent material of the substrate 1 may be any material that is transparent to the wavelength of the semiconductor laser, such as glass, acrylic resin, polycarbonate resin, etc., from among those conventionally used as substrate materials. However, in terms of compatibility with CD,
Polycarbonate resin is preferred.

The recording layer 2 is usually an inorganic thin film that can be formed by vapor deposition or sputtering, and is in an amorphous state immediately after the film is formed, and crystallized bits with low reflectance are formed by recording. do. The complex refractive index in the amorphous state before the phase change of the recording layer is na *= na −ika
, the complex refractive index in the crystalline state after phase change is nc *=nc
-ikc, na and nc are generally in the range of 3.0 to 6.0 for ordinary metal or semiconductor inorganic thin films. It is necessary that ka = 0.1 to 1.0 in order to obtain a reflectance of 70% when the thickness of the recording layer is 200 to 1000 Å. If ka > 1.0, it is necessary to make the recording layer thinner than 200 Å, which causes problems in that it is difficult to obtain stability over time and sufficient contrast. Also, k
When a<0.1, the recording sensitivity becomes extremely poor and recording cannot be performed using a normal semiconductor laser. On the other hand, after phase change kc
If it is not >0.5, the decrease in reflectance is insufficient and it is difficult to obtain contrast. Furthermore, if ka<kc, contrast cannot be achieved due to the decrease in reflectance.

Here, with reference to FIGS. 2 and 3, we focused on the dependence of the reflectance on the recording layer thickness, and found that the initial reflectance was 70%.
Let us now consider the case where a film thickness that provides a large contrast is selected. In the case of na = nc shown in Fig. 2, there is only a decrease in reflectance due to an increase in absorption; therefore,
It is difficult to obtain contrast unless the difference between ka and kc is large. However, in the example of nc>na as shown in FIG. 3, the reflectance minimum point is shifted before and after the phase change, so that a large contrast can be easily obtained. nc<
The same applies to na. Therefore, in the present invention, na≠nc. Note that the above conditions regarding optical properties are not necessarily satisfied in a completely amorphous or crystalline state, but must be satisfied in a mixed state of an amorphous and crystalline state or a so-called microcrystalline state. You can leave it there.

Recording layer materials satisfying the above-mentioned optical properties include, for example, Ga, Al, Ge, Si, Se, Te, and Bi.
, Sb, and other elements by optimizing the composition of the alloy. The crystallization temperature of the alloy is desirably 100° C. or higher from the viewpoint of stability over time, and desirably less than 300° C. from the viewpoint of recording sensitivity. Among them, Sb1-x Sex (x = 0.55 to 0.65) or Ge1-y Tey (y = 0.45 to 0.55) not only can satisfy the above optical properties, but also can be used by vacuum evaporation method and sputtering method. While a stable amorphous state is formed by either method, it can be sufficiently crystallized with a pulse of several hundred nanoseconds or less during laser beam irradiation, making it suitable for optical recording.

[0022] In forming an alloy thin film having such a composition, an alloy whose composition has been adjusted in advance may be used, or a multi-component vapor deposition or sputtering method may be used. The film thickness is 200~
The thickness is preferably 1000 Å. That is, if it is less than 200 Å, it is difficult to change the reflectance before and after recording, that is, the contrast, and if it exceeds 1000 Å, the heat capacity of the recording layer becomes large and the recording sensitivity decreases. In particular, the recording layer thickness is Sb1-x
For Sex (x=0.55~0.65), 600~
700 Å, Ge1-y Tey (y=0.45-0.
55), it is preferably 400 to 470 Å. S
b1-x Sex (x=0.55-0.65) or G
ex Te1-x (x=0.45 to 0.55) has a crystallization temperature of about 200° C. and is in an extremely stable amorphous state at room temperature, and can be crystallized at high speed when irradiated with laser light.

[0023] Note that if the recording layer is Sb-Se or Ge-Te,
It is also possible to add a third element to the alloy thin film as needed to improve stability over time, recording sensitivity, optical properties, etc. In this case, the third element is Ge(Sb-
In the case of Se), Te (in the case of Sb-Se), Sb (in the case of Ge
-In the case of Te), Se (in the case of Ge-Te), Au, A
Examples include one or more of g, Cu, Pt, Pd, Co, Ni, Ti, etc., but are not limited to these elements. The amount of these third elements added is 5 at.% based on the total amount of Sb-Se or Ge-Te, which are the main components.
It is preferable that the amount is less than (5 atomic % or less in total when there are two or more kinds of third elements). Specific actions of these third elements include, for example, Au, Ag, Pe, and Pd.
, Co, etc. increase the crystallization rate and shorten the recording time. Further, Bi, Se, Ge, Sb, etc. act to stabilize the amorphous state.

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

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

The reflective layer 4 has the function of increasing the contrast in reflectance and promoting the diffusion of thermal energy absorbed by the recording layer 2. The material for forming the reflective layer 4 is preferably Au, Ag, Cu, Al, or an alloy containing these metals as a main component, particularly Au, and the film thickness is 1.
It is preferably in the range of 00 to 5000 Å, preferably 300 to 5000 Å. If the film thickness is less than 100 Å, the reflectance will be too low, and if it exceeds 5000 Å, it will be disadvantageous in terms of film formation time and cost.

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

[0028]

[Examples] The present invention will be explained in more detail with reference to experimental examples, working examples, and comparative examples, but the present invention is not limited by the following examples unless it exceeds the gist thereof.

Experimental Example 1 As a specific example of layer structure design, we used an Sb40Se60 recording layer, tantalum oxide for the dielectric layer, and Au for the reflective layer, and the complex refractive index of these materials is shown in Table 1. It was calculated using actual measurements or literature values at a wavelength of 780 nm.

[0030]

[Table 1]

FIGS. 4 to 8 show the reflectance before and after crystallization when the thickness of the upper dielectric layer is changed for various recording layer thicknesses of 1000 Å or less. However, the reflectance is a value when light is incident through the substrate. In each figure, the requirements of claim 4 are satisfied within the range of dielectric layer thickness indicated by ⇔. As shown in the figure, if the thickness of the recording layer is 800 Å or more, a reflectance of 70% or more in an amorphous state cannot be ensured. on the other hand,
If the thickness of the recording layer is 500 Å or less, the requirements of claim 4 are satisfied only in a very narrow region, and the dependence of the reflectance on the film thickness in this region is steep, which is unfavorable in terms of manufacturing. The requirements of claim 4 are satisfied only when the recording layer thickness is 600 to 700 Å and when the dielectric film thickness is relatively wide. Note that the results described here hold true for all dielectric materials having a refractive index of about 2.1. Specifically, ZnS, Si3N
4 etc. can be mentioned. Further, even if there is a slight variation in the optical constants used here, similar results hold.

Experimental Example 2 The Ge50Te50 recording layer was evaluated in the same manner as in Experimental Example 1. The complex refractive index of each material was calculated using actual measured values at a wavelength of 780 nm as shown in Table 2.

[0033]

[Table 2]

FIGS. 9 to 13 show the dependence of the reflectance on the dielectric film thickness before and after crystallization at various recording layer thicknesses. In order to satisfy the requirements of claim 4, the reflectance was controlled by adjusting the film thickness of the tantalum oxide layer on the horizontal axis, but the above conditions are satisfied in the range where the recording layer film thickness is less than 400 Å and more than 470 Å. It is not possible. Recording layer thickness 400~
It can be seen that only at 470 Å, the above condition regarding reflectance is satisfied. At this time, the thickness of the tantalum oxide layer is 10
It must be between 00 and 1300 Å. Note that the results obtained here hold true for all dielectric materials with a refractive index of about 2.1. Specifically, ZnS, Si3 N4, etc. can be mentioned.

Example 1 and Comparative Example 1 An amorphous film of Sb45Se55 was formed to a thickness of 700 Å on a glass substrate and a polycarbonate resin substrate, respectively, by sputtering, and then Ta was deposited in a mixed gas atmosphere of Ar and oxygen. reactively sputtered to a thickness of 1800 Å.
A tantalum oxide film was formed. Finally, an Au film was formed to a thickness of 2000 Å by sputtering to produce a recording medium having the layer structure shown in FIG.

Further, 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 thickness of the recording layer was set to 200 Å or 1000 Å. In this case, a hard coat layer is essential to prevent deformation of the recording layer.

When the temperature of a sample using a glass substrate was raised and the crystallization temperature was evaluated at the temperature at which the reflectance suddenly decreased, it was approximately 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%.

Note that the complex refractive index of the recording layer before crystallization is:
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 with a wavelength of 780 nm.

[0039]

[Table 3]

Next, a sample using a polycarbonate resin substrate was rotated at a linear velocity of 1.4 m/s, irradiated with semiconductor laser light with a wavelength of 780 nm, and recorded using pulse waveforms of various duties at a frequency of 200 kHz. Let Ra be the playback signal level before recording, Rc be the signal level of the part where the reflectance has decreased the most in the waveform of the playback signal after recording,
Contrast was defined using the following formula.

[0041]

[Math 1]

When recording was carried out at 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 power was 10 to 2 at 15 mW.
Only 0% contrast was obtained. This is thought to be because heat escape from the recording layer to the reflective layer was large and sufficient crystallization was not possible. Note that in Example 1, a C/N ratio of 50 dB was obtained.

Example 2 Sb4 was deposited on a glass substrate and a polycarbonate resin substrate.
An amorphous film of 5Se55 was formed to a thickness of 650 Å by sputtering, and then Ta was reactively sputtered in a mixed gas atmosphere of Ar and oxygen to form a tantalum oxide film of 1000 Å thick. Finally, Au was formed by sputtering.
A film was formed to a thickness of 2000 Å to produce a recording medium having the layer structure shown in FIG.

When a sample using a glass substrate was heated and the crystallization temperature was evaluated at the temperature at which the reflectance suddenly decreased, it was approximately 220°C. Reflectance before crystallization 72%,
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 with a wavelength of 780 nm.

Next, a sample using a polycarbonate resin substrate was rotated at a linear velocity of 1.4 m/s, irradiated with a reactionary laser beam with a wavelength of 780 nm, and recorded using pulse waveforms of various duties at a frequency of 500 kHz. . Let Ra be the playback signal level before recording, Rc be the signal level of the part where the reflectance has decreased the most in the waveform of the playback signal after recording,
Defined by the formula shown in Example 1, laser power 15 mw
When recording was carried out, a maximum contrast of 50% was obtained. Further, a C/N ratio of 50 dB was obtained.

Comparative Example 2 In Example 1, the recording layer was formed to a thickness of 100 to 1500 Å in approximately 100 Å increments, and an Au layer was directly formed to a thickness of 2000 Å without using a tantalum oxide layer. Among these, a medium with a reflectance of 70 to 80% in an amorphous state and a reflectance of less than 50% after crystallization was obtained when the recording layer thickness was around 200 Å and 1000 Å. An attempt was made to record these while rotating at a linear velocity of 1.4 m/s, but even with a maximum recording power of 15 mw, a contrast of only 10 to 20% could be obtained. This is thought to be due to the large amount of heat escaping from the recording layer to the reflective layer, making it impossible to achieve sufficient crystallization. Furthermore, in a layer configuration that does not use tantalum oxide, the reflectance varies greatly with respect to variations in the recording layer thickness, making it difficult to obtain a uniform reflectance.

Example 3 An amorphous film of Ge45Te55 was formed on a glass substrate and a polycarbonate resin substrate by sputtering.
A tantalum oxide film with a thickness of 1300 Å was formed by reactive sputtering of Ta in a mixed gas atmosphere of Ar and oxygen. Finally, an Au film was formed to a thickness of 2000 Å by sputtering to produce a recording medium having the layer structure shown in FIG.

[0048] A sample using a glass substrate was heated and the crystallization temperature was evaluated at the temperature at which the reflectance suddenly decreased, and it was found to be about 200°C. At a wavelength of 780 nm,
A reflectance of 75% before crystallization and a reflectance of 47% after crystallization were obtained. In addition, the complex refractive index before crystallization is at a wavelength of 780 nm.
4.0-0.9i, 5.4-3.6 after crystallization
It was i.

Next, a sample using a polycarbonate resin substrate was rotated at a linear velocity of 1.4 m/s, irradiated with semiconductor laser light with a wavelength of 780 nm, and recorded using pulse waveforms of various duties at a frequency of 200 kHz. Let Ra be the playback signal level before recording, Rc be the signal level of the part where the reflectance has decreased the most in the waveform of the playback signal after recording,
Contrast Defined by the formula shown in Example 1 and recorded with a laser power of 12 mw, a maximum contrast of 40% was obtained. Further, a C/N ratio of 45 dB was obtained.

Example 4 A thin film having a composition of Sb40Se60 was deposited on a glass substrate.
The tantalum oxide film was vacuum-deposited to a thickness of 0 Å or 700 Å, and tantalum oxide films of various thicknesses shown in Table 4 were formed thereon by reactive sputtering, and gold was further vacuum-deposited to a thickness of 2000 Å. Note that although the composition of the recording layer was determined by fluorescent X-ray method, there was a variation of about ±3%.

Table 4 shows the reflectance and contrast read from the substrate side before and after crystallization for the various layer configurations described above.

[0052]

[Table 4]

[0053] No. of Table 4. All of Nos. 1 to 5 satisfy the requirements of the present invention, and almost match the calculated values in FIGS. 6 and 7 within the range of experimental error (±5%). Further, a maximum contrast of 71% was obtained. The complex refractive index of the recording layer before crystallization was 3.8-0.25i, and after crystallization was 4.7-0.8i.

Comparative Example 3 When a Ge12Sb40Te48 film was used as the recording layer, at a film thickness of 100 Å 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 means that the complex refractive index of this recording layer is 3 before crystallization.
．． This is because the absorption coefficient in the amorphous state is too large at 8-2.0i and 5.5 to 3.8i after crystallization, and at this complex refractive index, it is impractical to set the recording layer thickness to 100 Å or less. It was also concluded from the calculation results taking into account the interference effect that a reflectance of 70% or more cannot be obtained unless the reflectance is set to a specific value. Furthermore, it can be concluded from simple calculations that with such a film thickness, it is difficult to reduce the reflectance after crystallization to less than 50%.

According to the study results of the present inventors, a Ge-Sb-Te alloy film recording layer having a composition as disclosed in JP-A-62-209742, JP-A-63-225934, etc. is in an amorphous state. A recording layer with an absorption coefficient of 1.0 or less was not obtained.

[0056]

[Effects of the Invention] As described in detail above, the optical information recording medium of the present invention provides a high-performance optical information recording medium that is capable of optical recording and can be directly reproduced by a CD-only drive. .

[Brief explanation of the drawing]

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

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

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

[Figure 4] Figure 4 shows the results of Experimental Example 1 (recording layer thickness 400 Å).
This is a graph showing the case of

[Fig. 5] Fig. 5 shows the results of Experimental Example 1 (recording layer thickness 500 Å).
This is a graph showing the case of

[Fig. 6] Fig. 6 shows the results of Experimental Example 1 (recording layer thickness 600 Å).
This is a graph showing the case of

[Figure 7] Figure 7 shows the results of Experimental Example 1 (recording layer thickness 700 Å).
This is a graph showing the case of

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

[Fig. 9] Fig. 9 shows the results of Experimental Example 2 (recording layer thickness 400 Å).
This is a graph showing the case of

FIG. 10 shows the results of Experimental Example 2 (recording layer thickness: 43
0 Å case).

[Fig. 11] Fig. 11 shows the results of Experimental Example 2 (recording layer thickness 45
0 Å case).

[Fig. 12] Fig. 12 shows the results of Experimental Example 2 (recording layer thickness 47
0 Å case).

[Fig. 13] Fig. 13 shows the results of Experimental Example 2 (recording layer thickness 50
0 Å case).

[Explanation of symbols]

1 Board 2 Recording layer 3 Dielectric layer 4 Reflection layer

Claims (4)

[Claims] 1. A recording layer, a dielectric layer, and a metal reflective layer are sequentially laminated on a substrate, and a phase change between an amorphous state and a crystalline state is induced in the recording layer by laser beam irradiation. This is an optical information recording medium in which information is recorded by a laser beam through a substrate and information is read out by a decrease in reflectance caused by the phase change. The reflectance read by light is 70% or more, and the complex refractive index n of the recording layer is
*=n-ik takes a value of k=0.1 to 1.0 in the state before the phase change as recorded above, and k>0.5 in the state after the phase change and before the phase change. An optical information recording medium characterized in that n changes to a larger value and does not have the same value before and after the phase change. 2. The recording layer has Sb1-x Sex (x=
0.55 to 0.65). The optical information recording medium according to claim 1. 3. The recording layer is Ge1-y Tey (y=
0.45 to 0.55). The optical information recording medium according to claim 1. 4. 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 less than 50%.
3. The optical information recording medium according to any one of 3.