JPS6253886A - Information-recording medium - Google Patents

Abstract

PURPOSE:To greatly enhance thermal stability while substantially maintaining the change of optical characteristics peculiar to an Sb-Te binary system, by providing a recording layer comprising at least Sb, Te and Ge in a specified composition range on a base. CONSTITUTION:The recording layer 2 of the information-recording medium comprises at least Sb, Te and Ge, and has a composition of general formula (SbxTe1-x)yGe1-y, wherein x is 0.05-0.7, preferably, 0.1-0.6, and y is 0.4-0.8, preferably, 0.5-0.7. The recording layer 2 is provided by vapor deposition such as vacuum deposition and sputtering. The composition is preferably controlled by ternary co-deposition in the case of vacuum deposition or by flash vapor deposition of a material to be vapor-deposited having a specified composition.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a novel information recording material, more specifically, a recording layer provided on a predetermined substrate is irradiated with an energy beam such as a laser beam, and the irradiated portion is The present invention relates to a medium for recording and reading information using changes in reflectance.

Conventional technology Recordable information recording media that have been proposed so far include:
For example, a recording medium is known in which a predetermined recording layer is provided on a substrate, irradiated with laser light to form holes corresponding to information, and information is read out using the difference in reflectance depending on the presence or absence of the holes. .

In this case, the recording layer used is Te, which has a low melting point.
and B1 and alloys or compounds containing them are well known.

In addition, a recording layer has been proposed in which the optical properties are changed by laser beam irradiation and the change in reflectance caused by this change in optical properties is utilized.As such, for example, fine particles of To are dispersed in TeO2. The system that made it, 5
Two-layer structures such as b2Se and \Bi2Te3 are known.

However, in the above-mentioned pore-forming method, in addition to heating, the process of forming pores involves melting, dispersion, or evaporation, so the viscosity during melting and the surface tension during dispersion have subtle effects. However, it is difficult to control the shape of the hole, and residues are generated inside the hole, resulting in increased noise and errors.

On the other hand, the method that utilizes the change in optical properties caused by heating by laser beam irradiation does not require the process of melting, dispersing, or evaporating the recording layer, so it is easy to control the shape of the pits, and The problem of residue generation in the holes is also eliminated. However, conventional recording materials using this method have poor thermal stability, which has been a practical obstacle. □ By the way, the transmittance of the compound Sb2Te changes greatly when heated, so its use as an information recording material has been considered in the past, but due to the low temperature change and lack of thermal stability, it has not been put to practical use. [Journal of Applied Physics (J, Appl, Phya) J.

Volume 54 (Vol. 3), pages 1256-1260].

Problems to be Solved by the Invention In view of the above circumstances, the purpose of the present invention is to provide an information recording medium that utilizes changes in optical characteristics caused by laser irradiation.
The object of the present invention is to provide a recording material that is thermally stable and superior to conventional recording materials in terms of sensitivity 4C ratio and pit error rate.

Means for Solving the Problems The inventors of the present invention have conducted intensive research to achieve the above object, and have found that the substrate is made of at least three elements, Sb, Te, and ae, and the ratio of these three elements is We have discovered that by providing a recording layer in which 5t)-Te has a specific range of temperature, the thermal stability can be significantly improved without changing the optical properties that are characteristic of the binary system of 5t)-Te. Based on this knowledge, we have completed the present invention.

That is, the present invention provides an information recording medium in which a recording layer made of a material whose light absorption coefficient changes upon heating is provided on a substrate, and information is recorded by a change in light reflectance caused by the change in the absorption coefficient. The recording layer is made of at least Sb.
, consisting of three elements Te and Ge, and these three elements have the general formula % (where X is 0.05-0,7.y is 0.4-0.8
The present invention provides an information recording medium characterized by having a composition represented by:

As a heating means at this time, irradiation with an energy beam such as a laser beam or an electron beam is suitable.

The recording layer in the information recording medium of the present invention comprises at least S
It consists of three elements: b, Te, and Ge, and their composition ratios are expressed by the general formula (BbXTe, -x), Ge, -
When expressed as y, X is 0.05 to 0.7, preferably 0.1 to 0, and 6.7 is 0.4 to 0.8. Preferably O,
It is in the range of S to 0.7. If the value of
Also, if the value exceeds 0.7, the contrast becomes extremely low.
Therefore, the S/N ratio also becomes low.

On the other hand, if the value of y exceeds 0.8, changes in the absorption coefficient due to heating will occur at low temperatures, resulting in a decrease in thermal stability, and if the value of y is less than 0.4, the contrast will be extremely reduced, and the S
, /N ratio also becomes low. If sensitivity is particularly important,
The value of is preferably in the range of 0.1 to 0.35.

Furthermore, from a practical point of view, it may be necessary to continue irradiating the information readout beam to the same location for a long time.
During such long-time playback, heat from the readout beam accumulates, which causes the unrecorded area to gradually approach the same state as the recorded area, resulting in a decrease in the amplitude of the reproduced signal and a gradual increase in the SA ratio and error rate. tends to decline. Therefore, in order to take into consideration the stability for such long playback and balance the sensitivity and sensitivity, the value of X should be 0.15 to 0.4 and the value of y should be 0.5.
Practically speaking, the amount is preferably in the range of 0.7 to 0.7.

In the information recording medium of the present invention, the recording layer is Sb%
Although it is practically sufficient to use a material consisting of only the three elements Te and Ge, other elements may be included if necessary.

The recording layer of (s bXT el -x )yG el -7 is formed by a vapor deposition method such as vacuum deposition or sputtering. For composition control, in the case of vacuum evaporation,
It is preferable to use a three-component co-evaporation method or a flash vapor deposition method using a deposited material having a specific composition, and depending on the desired composition, a two-component co-deposition method can also be used.

In the case of sputtering, on the other hand, it is advantageous to use a target material of a specific composition or to place fragments of one element or alloy on top of a target material of one element or alloy.

When forming a film by vacuum evaporation, the degree of vacuum is 1.
Range from 0” to 10-Torr, deposition rate from 0.5 to
A range of 20 A/sec is preferable, and since there is no particular restriction on the substrate temperature, room temperature is preferable.

On the other hand, when using the sputtering method, the substrate temperature is particularly likely to rise, so cooling is required.

In general, when thin films are stacked on a substrate, the reflectance is uniquely determined by the refractive index, absorption coefficient, and thickness of the substrate and thin film. By determining the reflectance at , the range of film thickness for increasing the change in reflectance before and after heating is automatically determined. On the other hand, when recording is actually performed by irradiation with laser light or the like, the absorption rate of the laser light and the state of heat dissipation vary depending on the thickness of the recording layer and the reflective layer, and therefore the recording sensitivity varies. The preferable film thickness range of the recording layer and the reflective layer is mainly determined by the above two factors.

(S b x T e - is 700A or more, preferably 800-200A
It is better to set it in the range of 0A. However, if the film thickness is made too thick, it becomes difficult to uniformly generate physicochemical state changes in the film thickness direction to change the light absorption coefficient, making it difficult to obtain a ratio corresponding to the original high contrast. become unable to do so. On the other hand, when a reflective layer is provided above or below the recording layer, sufficient contrast can be obtained even in areas where the recording layer is thin, resulting in a high S/N ratio.
This is advantageous because the ratio can be obtained. When providing such a reflective layer, the thickness of the recording layer depends on the material and thickness of the reflective layer, but is generally 20 to 1000 A.
A range of is preferred.

The material that can be used for the reflective layer is preferably a substance that has a high absorption coefficient for the information readout beam, such as AI! , Ti,
Or, Co, Ni, Se, Ge, Zr, A
g.

In, Sn, Sb, Te, Pt, Au, P
Examples include metals such as B, Bi, and alloys thereof.

Among these, 8b, Te, Bi, 6, or alloys thereof are particularly excellent in sensitivity. The reflective layer is
These elements or alloys may be used alone, or two or more elements or alloys may be stacked. The thickness of this reflective layer is 1
00x or more is preferable, especially from the viewpoint of sensitivity 100 to 10
It is preferably in the range of 00 A. In the following, when describing a configuration in which a reflective layer is provided, both the recording layer and the reflective layer are collectively referred to as an information carrier layer.

In the present invention, when the recording layer is used as an information recording medium, the recording layer or the information carrier layer may be used alone, but in each case, at least above or below the recording layer or the information carrier layer is made of a metal compound. It is preferable to provide a layer in order to prevent deterioration of characteristics over time.

In particular, when used as a recording medium for coded digital information such as computer memory, even local changes in film quality can significantly increase errors.
Providing a metal compound layer is extremely effective for preventing deterioration.

As the metal compound used in the present invention, AI! , Or.

Si, Zr, Ti, Ge, Se, Te, V
, Hf, La, Sm.

Oxides or nitrides of elements selected from Y, Ta, and Mo are preferred, and among these, oxides or nitrides of Si are particularly preferred. These metal compound layers,
When provided at least above or below the recording layer or information carrier layer, it prevents water, oxygen, etc. from penetrating into the recording layer or reflective layer from the air or the substrate, and greatly suppresses deterioration of the recording material. Ru. In particular, oxides or nitrides of Sl are excellent in this effect.

The metal compound layer used in the present invention may be either a single layer of the same metal compound or a stack of two or more metal compounds.

When provided on both the upper and lower sides of the recording layer or information carrier layer, the types of metal compounds on the upper and lower sides may be the same or different. The thickness of the metal compound layer is preferably in the range of 100 to 5000 A from the viewpoint of sensitivity.

The reflective layer and the metal compound layer in the present invention can be formed using a vapor deposition method such as vacuum vapor deposition or sputtering, like the recording layer.

As the substrate in the present invention, glass, a photocurable resin on glass, a plastic substrate such as polycarbonate, acrylic resin, Epoquine resin, polystyrene, etc., a metal plate such as aluminum alloy, etc. are used.

10 to 13 are cross-sectional views showing examples of the structure of the recording medium of the present invention, where l is a substrate, 2 is a recording layer, 3 is a reflective layer, and 4 is a metal compound layer.

When the recording medium of the present invention is actually used as an information recording medium, two identical disks each having a recording material provided on a substrate are placed with the surfaces provided with the recording material facing each other with a spacer interposed therebetween. A so-called air sand inch structure is used, in which two identical discs are bonded together over their entire surface without a spacer, with the recording material facing each other. The recording material may have any structure, such as a so-called full-surface adhesive structure, or a structure in which a recording material is provided on a film-like sheet and the sheet is rolled up.

Example Next, the present invention will be explained in more detail with reference to Examples.

Reference Example: On a slide glass with a thickness of 1.2 rIrm, a film e, 3 having a composition as shown in Table 1 was formed by binary co-evaporation from two evaporation ports containing Sb and Te using a resistance heating method.
Each was formed with a thickness of 00A.

Table 1 The light transmittance at a wavelength of 850 nm was measured for these samples in an untreated state and in a state after being heat-treated for about 10 minutes in an oven heated to 200°C. FIG. 1 shows the rate of change in transmittance before and after this heat treatment.

From FIG. 1, it can be seen that the change in transmittance is large in the range where the Sb atomic number coefficient is 20% or more and 70% or less. sb is 20
% or less, the transmittance increases due to heating, but it was confirmed by X-ray diffraction analysis that this is due to oxidation of Te.

Example 1 A film having the composition shown in Table 2 was formed on a slide glass with a thickness of 1.2 ff by six-component co-evaporation from three vapor deposition ports containing Sb, Te, and Gθ using a resistance heating method. were each formed to a thickness of 300λ. As a comparative example, Sb, To8 alloy was deposited from one deposition port to form a film with a thickness of 300A.

Table 2 These samples were subjected to heat treatment for about 10 minutes at a temperature range of 50° C. to 250° C., and the light transmittance at each temperature was measured at a wavelength of 1350 nm. The rate of change in transmittance is large in all regions in FIG. 2.

50 of these samples that were not subjected to heat treatment.
When the transmittance of samples A and G was measured after being left in a constant temperature and humidity chamber at 9Q%RH for 10 days, the transmittance of samples A and G was about twice and about 1.5 times, respectively, compared to the initial value. It was increasing. It is presumed that this increase in transmittance is due to the oxidation of 're.

On the other hand, for samples other than A and G, almost no change in transmittance was observed.

From the above, it can be seen that when the value of X is in the range of 0.05 to 0.7, the change in transmittance due to heating is large and the film is stable even in a high temperature and high humidity environment.

Example 3 On a disc-shaped acrylic substrate obtained by injection molding with a diameter of 305 Mn and a thickness of 1.5 fl, ternary components were deposited from three vapor deposition boats containing Sb, Te, and Ge by resistance heating. By vapor deposition, SbO02Te004Go
Films with a composition ratio of 0.4 were +SOD @ and a, respectively.
ooX.

It was formed with a thickness of 1000A and 1500A. These samples were rotated at 900 rpm and irradiated with condensed light from a semiconductor laser (wavelength: 850 nm) through the transparent substrate to write a 1.5 MHz signal. At this time, the laser power required to record a signal at a diameter of 140H on the disk was 4 mW and 4 mW, respectively, on the recording film surface.
They were 5 mW, 3.5 mW, and 4 mW, and had sufficient sensitivity for practical use.

To reproduce the signal, semiconductor laser light of the same wavelength is used,
Regeneration was performed at 1.2 mW. The signal q/M ratio has a band width of 30
30 dB and 50 dB at KHz, respectively
, 53 dB, 50 dB with te, 80C)A
For all of the above, we obtained more than 50 dB.

When the above recording medium was left in a drying room at 80° C. for 7 days, no change in reflectance was observed, and no change in C/l was observed either.

FIG. 5 shows the reflectance of these samples before and after heat treatment at 250°C. The calculated curve was calculated based on the refractive index and extinction coefficient (Y) determined in Example 1. The solid line in the figure is before heating, and the broken line is after heating (the same applies hereinafter).

Example 4 On a slide glass with a thickness of 1.2H, by resistance heating,
19b, Bbo, 1□Te by ternary codeposition from three deposition boats containing To and Ge. , 4
It was formed to have a thickness of 8#600mm, and an Sb film was further provided thereon to a thickness of 100OA by resistance heating.

The reflectance from the slide glass side at a wavelength of 830 nm was measured for these samples in an untreated state and in a state in which they were heat-treated for about 10 minutes in an open air heated to 200°C. FIG. 6 shows the reflectance before and after this heat treatment. From FIG. 6, it can be seen that when sb is used for the reflective layer, the contrast is highest when the thickness of the recording layer is around 350^.

Next, SbO,
, 120; 48 Ge01.4 film with a composition ratio of 350
After forming sb to a thickness of 200 A and 500 A, respectively, on top of this by resistance heating method.
Formed. FIG. 7 shows the reflectance of the sample formed on the slide glass before and after the heat treatment, which was similarly measured from the slide glass side. The calculation curves shown in FIGS. 6 and 7 were calculated based on the refractive index and extinction coefficient determined in Example 1.

When a sample with a film formed on an acrylic substrate was evaluated in the same manner as in Example 3, it was found that the sb reflective layer was 20
For OA and 500A, the sensitivity is 4
mW and 5.5 mW, the CA ratio is 60 dB and 58
dB, and had sufficient sensitivity and contrast ratio for practical use. However, the sensitivity was lower and the ratio was slightly lower in the case of the case with soo Sb compared to the case of 20OA due to large heat dissipation. Even when these samples were left in a dryer at 60° C. for 10 days, no change was observed in sensitivity, contrast ratio, or reflectance.

Example 5 A groove (depth 700'A, medium 0
．． 1.5 fins with a thickness of 1.5 μm and a pitch of 1.6 μm,
By resistance heating method on an acrylic substrate with a diameter of 305 fl,
SbO,,25Te0z45 was obtained by ternary codeposition from three deposition boats containing Sb, Te, and Ge.
A film with a composition ratio of GeO: 3. After forming it to a thickness of ooi, apply AI! A film 200k was also provided by the resistance heating method.

This recording medium was evaluated in the same manner as in Example 3, and the reflectance before and after heat treatment is shown in FIG. Figures 8 and 9 are respectively AI! Reflective layer Soo large and recording layer thickness 30
This is a calculated curve in the case of 0^, and the calculation was performed based on the refractive index and extinction coefficient determined in Example 1.

Even when these samples were left in a dryer at 60° C. for 10 days, no change was observed in sensitivity, φ ratio, and reflectance.

Example 6 On the same acrylic substrate as in Example 5, 200% of Sb and Te3 and 1% of Ge were deposited by binary co-evaporation from two deposition boats containing Sb2Te and Ge using a resistance heating method.
00λ equivalent was provided. Furthermore, an Sb film with a thickness of 200λ was formed on this by electron beam evaporation method,
A Bi2Te film having a thickness of 200^ was prepared.

In addition, as a comparative example, a 300A thick S
b. After forming a Te3 film, a 200A thick film was formed on it.
An Sb film formed thereon was prepared. In terms of composition ratio of the film formed in each sample, the Ge content was approximately 40%. These six recording media were evaluated in the same manner as in Example 3, except that the signal to be recorded was 3 MHz, and the one with the sb reflective layer had a sensitivity of 5.
The mW% low ratio was 60 Tsukuda, and the reflection layer of B1□Tθ3 obtained a sensitivity of 3.5 mW% CA ratio of 57 dB. Moreover, the comparative example obtained a sensitivity of 4.5 mW and a C, A ratio of 60 dB.

When these recording media were left in a dryer at 60°C for 7 days, there was no change in the sensitivity, O/N ratio, or reflectance of the two examples, but the recording media of the comparative example showed no change in the initial reflectance. 25
% to 40%, and the ratio significantly decreased to 20 dB.

Example 7 Grooves (depth 700 mm, width 0.6 cape, pitch 1.6 μrrL) were formed in advance on a tempered glass disc with a thickness of 1.5 m and a diameter of 305 fl using a photocurable resin. On the substrate, resistive heating method (secondary, Sb, Te and Ge
Ternary co-evaporation (: therefore,
8bI:115 0-. A film having a composition ratio of 55°80:5 was formed to a thickness of 400^, and a 30OA B1 film was further provided thereon by the same resistance heating method.

When this recording medium was evaluated in the same manner as in Example 6, a sensitivity of 6 mW and a q/N ratio of 5 f3 dB were obtained.

Even if this was left in a dry room at 80°C for 10 days, the sensitivity
No change was observed in the C/A ratio or reflectance.

Example 8 On the same acrylic substrate as in Example 5, the three elements St), Te, and Ge were co-evaporated by resistance heating to form a film with a composition ratio of (5bxTe□-X)AGθ□-7. Sa30
Formed at 0X. Here, three types of samples were created in which y=0.6 and the value of X was 0.1, 0.2, and 0.3. For all these three samples, (s
An sb film with a thickness of 200 A was further formed on the bXT ex -x )yG el-7 film.

When each medium was evaluated in the same manner as in Example 6, the sensitivity and cyN ratio (6.5 mw, 6
odB), (4mW, 60dB), (4,smw.

(5Q dB) was obtained. These discs at 60°C
When the signals were reproduced after performing an accelerated test for 7 days under the condition of 182% RH, no change in the ratio was observed for any of the samples.

Example 9 A 5102 film was formed to a thickness of 20 OA by electron beam evaporation on the same acrylic substrate as in Example 5, and then deposited from three evaporation ports containing Sb, Te, and Ge by resistance heating. By ternary codeposition, SbO,1
5Te0.45Ge□, a film with a composition ratio of 4 at 100O
Finally, SiQ□ was formed to a thickness of 20 OA by electron beam evaporation.

These samples were rotated at a speed of 900 rl) m and exposed to a semiconductor laser (wavelength: 830 rl) through the transparent substrate.
nm) is focused and irradiated to create a diameter of about 14 nm on the disk.
An information signal was written to the 0ff location. The information signal is a single frequency (5.1MHz) according to the M”FM modulation method.
A pulse train of z) was used. To reproduce the signal, a semiconductor laser beam of the same wavelength is used, and the reproduction is performed at 1.2 mW.
The bit error rate was determined by comparing with the recorded information signal.

When determining the bit error rate, the recording power of the laser was varied and the phase margin was measured, and the recording power at which the phase margin was the widest was determined as the optimum writing power.

When the above sample was evaluated in this way, the optimal write power and bit error rate (hereinafter abbreviated as BER) were 4.4. OmW and 3x10 bows.

Example 10 813N4 was deposited at 400A% Sbo, 15Teo, 5@9 on the same acrylic substrate as in Example 5 by sputtering.
Furthermore, Si3N4 was sequentially formed to a thickness of 40 OA.

When this sample was evaluated in the same manner as in Example 9, the BER was 2×10''.

After the above sample was left in a 90% dish environment at 60°C for 20 days, the previously written signal B113R was examined, and no change was observed at 2X10-6.

Example 11 On the same acrylic substrate as in Example 5 (40OA of 81Q was formed by electron beam evaporation method, and then ternary co-evaporation was performed from three ports containing Sb, Te, and Ge by resistance heating method). by SbO;15 Te0s45
A film with a composition ratio of Ge o.

SiQ was sequentially formed to a thickness of 60 OA.

When this sample was evaluated in the same manner as in Example 9, the BER was I x 10''.Next, one beam of reproduction laser light was applied to the previously recorded track (groove on the substrate).
．． When irradiation was continued at 2 mW and continuous reproduction was performed for 10 days, no change was observed in either BKR or phase margin. Furthermore, this sample is 60
After being left in an environment of °C and 90 SRH for 20 days,
When I checked the BKR of the previously recorded signal, I found that lX10
', and no change was observed.

Example 12 After forming an EliO□ film with a thickness of 500× on the same acrylic substrate as in Example 5 by electron beam evaporation, Sb and Te were formed by electron beam method, and Ge by resistance heating method. Deposit s b o , 2 Te.

:4001 film with a composition ratio of 45Ge0135 is formed,
Further 1: On top of this, 3 Sb is added by electron beam evaporation method.
00λ and 5102 were each formed to a thickness of 50OA.

When this sample was evaluated in the same manner as in Example 9, the BBR was 1 x 10''. Next, after leaving this sample in an environment of 60°C and 90% RH for 20 days, When I checked the BKR of the signal recorded on
10'' and no change was observed.

Example 13 Grooves were prepared in advance by injection molding (depth 700A).
1 width 0.65ttms pitch 1.6μ7+thickness 1.5
Sputtering was performed simultaneously on a U acrylic substrate by high frequency sputtering using 5b2Tθ3 and Ge targets, and the composition was 81) 20 T ess
A recording layer of Ge 4s with a thickness of 500 Å was provided, and an Sb film of 10 OA was further provided thereon by a resistance heating method. Semiconductor laser light (wavelength 830m) passes through the substrate of this medium.
), irradiate it, and transmit a 1.5MHz signal to 60Or
The substrate rotation speed was recorded in pm. The laser power required for recording was 5 mW on the recording surface.

A 1.2 mW semiconductor laser beam was used to reproduce the signal, and a ratio of 58 was obtained. Heat this medium at 60°C180% R
An accelerated test was conducted for 7 days under conditions of H, but the sensitivity and O
No change was observed in either , or J ratio.

Example 14 A groove (depth 700^, width 0
．． 6 μ door, pitch 1.6 PL) was formed on the substrate, and S
b. A recording layer with a thickness of 600 Å was formed by co-evaporating Te3 and Ge. Furthermore, an M layer having a thickness of 100 A was provided on this film by a similar resistance heating method.

When evaluated using the same method as in Example 13, the sensitivity was 6.5.
mW% (,4J ratio 60 dB was obtained.This medium
Even if left in a dryer at 80°C for 10 days, the sensitivity, c,
No change was observed in Ax ratio or reflectance. By the way,
The reflectance at this time was 31%.

Example 15 On the same acrylic substrate as in Example 13, 8b, Te, and Ge were co-evaporated from two evaporation boats containing 8b, Te, and Ge at 20OA and Ge at 100A by resistance heating method. I set it up quite a bit. Furthermore, by using a similar resistance heating method, an Sb film was formed on this film to a thickness of 200 K, and a film on which a Bi, Te film was formed to a thickness of 200 K was prepared. As a comparative example, an sb,'re3 film was formed on a similar substrate to a thickness of 300 H, and then an Sb film was formed on it to a thickness of 200 H. Both samples , the composition ratio of the film is Sb
:Te was approximately 2:3, and the Go content was approximately 40% for the two types with Ge added.

These three recording media were evaluated in the same manner as in Example 3, except that the recorded signal was 5 MHz.
When the reflective layer is sb, the sensitivity is 5 mW% and the ratio is 60 dB.
The reflective layer is Bi and Te3 has a sensitivity of 3.5 mw.
An OA ratio of 57 dB was obtained. In addition, the comparative example has a sensitivity of 4.5
mw%c, r ratio of 60 dB was obtained.

When these recording media were left in a dryer at 60°C for 7 days, there was no change in the sensitivity, so-ratio, or reflectance of the two examples, but the recording media of the comparative example had an initial reflectance of 25. %
This has changed from 40% to 40%, and the CA ratio is 20.
(It had dropped to LB.

Example 16 On the same acrylic substrate as in Example 13, the three elements Sb, Te, and Ge were co-evaporated by a resistance heating method to form a film with a composition ratio (SbxTθt-z)yGet-y of 300%.
It was formed with the same thickness. Here, three types of samples were created with X=0.4 and y values of 0.5, 0.7, and 0.9. For all three of these samples (
On top of SbxTel-x)yGel-y, sb was further formed to a thickness of 200^.

When each medium was evaluated in the same manner as in Example 15, the sensitivity and ratio (5.5 mW, 5
8 dB), (5mW, 60 dB), (4,
5 mW, 60 dB). When these discs were subjected to an acceleration test for 7 days at 6°C and 824RH, and the signal was played back, the y value was 0.
9 medium, the contrast decreases and the OA ratio is 4.
Q had decreased to cLB, but y was 0.5 and 0.7
No change in the φ ratio was observed in the case of .

Effects of the Invention According to the present invention, information is recorded with high sensitivity and height ratio,
Moreover, it is extremely stable with respect to temperature and humidity, and a highly reliable information recording medium can be provided.

[Brief explanation of the drawing]

Fig. 1 is a graph showing the transmittance change of the reference example, Fig. 2 is a graph showing the transmittance change due to heating of Example 1, Fig. 3 is a graph showing the thermal stability of Example 1, and Fig. 4 is a graph showing the transmittance change of Example 1. is Example 2
Graphs showing changes in transmittance, Figures 5, 6, 7,
8 and 9 are graphs showing the reflectance of samples of Example 3, Example 4, and Example 5, respectively; FIG. 10;
11, 12, and 13 are cross-sectional views showing different examples of information recording media according to the present invention, in which 1 is a substrate, 2 is a recording layer, 3 is a reflective layer, and 4 is a metal Each represents a compound layer. Patent applicant: Asahi Kasei Industries, Ltd.

Claims (1)

[Claims] 1. Information recording in which a recording layer made of a material whose light absorption coefficient changes when heated is provided on a substrate, and information is recorded by a change in light reflectance caused by the change in the absorption coefficient. In the medium, the recording layer is made of at least three elements, Sb, Te, and Ge, and these three elements have the general formula (Sb_xTe_1_-_x)_yGe_1_-_y(
However, x is a number in the range of 0.05 to 0.7, and y is a number in the range of 0.4 to 0.8.