JPH07266706A - Rewritable optical data recording method - Google Patents

Abstract

PURPOSE:To embody an optical data recording method excellent in the cycle number of times, long-term preservability and rewriting characteristics. CONSTITUTION:In an optical data recording member wherein a material membrane consisting of at least three elements of Te, Ge and Sb and characterized by that the respective atomic number ratios of Te, Ge and Sb are within the range surrounded by the respective compsn. points A1, B1, C1, D1, E1 in a compsn. diagram showing a compsn. range and the concn. of Te is 50% or more and selected in a compsn. range where free Te is not present is provided on a substrate as a recording layer, the recording layer is irradiated with laser beam to be heated and the irradiated part is quenched to be made amorphous and gradually cooled to be crystallized and a change of optical characteristics based on the generation of reversible phase transition is shown.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention uses a laser beam to
The present invention relates to an optical information recording method capable of recording, erasing, and reproducing information signals on a phase-change recording member at high speed and high density.

[0002]

2. Description of the Related Art In recent years, an optical disk using a laser beam has attracted attention as the amount of information increases, recording and reproduction speeds increase, and density increases. There are two types of optical discs, a write-once type that can be recorded only once and a rewritable type that can erase a recorded signal and can be used many times. The write-once type optical disc,
There are a method of reproducing a recording signal in a perforated state and a method of reproducing by generating unevenness. As a rewritable material, a Te-Ge-based chalcogenide glass thin film utilizing a reversible phase change between amorphous and crystal is well known (for example, Japanese Patent Publication No. 47-26897).

The present inventors have previously proposed a system in which a change in reflectance due to a phase transition of a system containing an oxide such as Te-TeO ₂ is used as a signal. In addition, as a rewritable optical disk utilizing phase transition, various additives are added to Te—TeO ₂ (Sn, Ge, Bi, In, Pb, Tl, S.
e)) (Japanese Patent Laid-Open No. 59-185048).
These recording members are characterized by high C / N and excellent moisture resistance.

A proposal relating to applying a Ge-Sb-Te-based material to a recording medium is disclosed in JP-A-61-89889. In the specification of JP-A-61-89889,
Ge _1-x Sb _4x Te on a resin substrate such as polycarbonate
A recording material represented by a composition formula of _{1 + 5x} (0 <x <1.0) was formed by a method such as vacuum deposition or sputtering, and the recording material layer was irradiated with a laser beam to change from amorphous to crystalline. It has been disclosed that it is possible to cause the transition of the above and obtain a large reflectance change. The gist of the invention is that, based on GeTe, a material having a lower crystallization transition temperature than that of GeTe is constituted, and thereby energy required for crystallization transition can be lowered, that is, a recording material having high recording sensitivity can be obtained. Especially. However, there is no description about whether or not the above composition can cause a transition from crystalline to amorphous, and if so, by what method. In addition, there is no description about the structural requirements necessary for repeatedly performing recording and erasing, for example, the heat-resistant layer for preventing deterioration of the substrate due to repetition.

Another proposal for applying a Ge-Sb-Te-based material to a recording medium is JP-A-62-53886.
Is disclosed in. In the original specification of JP-A-62-53886, (Sb _x Te _1-x ) _y Ge _1-y (where x is 0.05 to 0.7 and y is 0.4 to 0.8). ) Forming the recording material represented by the compositional formula by vapor deposition, sputtering, etc., and irradiating this recording layer with a laser beam causes a change in decrease in transmittance (a change in increase in absorption coefficient), It is disclosed that metal oxides or nitrides may be formed above and below the recording film for the purpose of preventing the recording layer from changing over time. However, in the case of this application as well, only the direction in which the absorption coefficient increases in the case of this application, that is, only the change in the characteristics accompanying the crystallization of amorphous is disclosed, and the above composition is conversely crystalline. There is no disclosure of whether or not it is possible to cause the transition from amorphous to amorphous and, if possible, how to achieve it.

A rewritable recording medium using a Ge-Sb-Te-based material is disclosed in JP-A-62-196181. Here, Ge ₂₃ Sb ₄₆ Te ₃₁ is formed on the resin substrate.
A GeSbTe recording material layer having a typical composition of: is provided by a method such as vapor deposition and sputtering, and Si is formed on both sides of this material thin film.
Providing a protective layer such as O ₂ or SiN, the recording material layer does not completely crystallize by irradiation with a laser beam during recording and erasing, and S
It is disclosed that a structural change between two phases, a (GeTe ₂ + Sb) phase in which b is precipitated and a (Ge + Sb ₂ Te ₃ ) phase in which Ge is precipitated, is caused to cause a change in reflectance. However, there is no description about whether or not a reversible phase change between a crystalline phase and an amorphous phase occurs in a Ge-Sb-Te material composition, and a specific method for causing the reversible phase change.

[0007]

Conventionally, the rewritable information recording method using the information recording member made of chalcogenide generally has a drawback that the stability against repeated recording and erasing is poor. The reason for this is that Te, Ge, which is the main component, and other additive components cause some phase separation in the film during repeated recording and erasing, and the constituent components of the film differ locally between the initial stage and the repeated stage. It seems that it was due to the fact that it ended up.

When an amorphous-crystal phase transition is used for reversible recording on an optical disk, laser light is used as the recording means, the recording film is once melted by laser irradiation, and then the amorphous film is rapidly cooled. However, the current semiconductor laser has an upper limit of power, and a film having a melting point as low as possible is desirable in terms of recording sensitivity. For this reason, the film made of the chalcogenide described above has a composition with a melting point as low as possible, that is, a film composition near the eutectic point where Te is considerably large in order to improve recording sensitivity. However, the fact that the content of Te is higher than that of the other additive components means that phase separation is caused by that much at the time of repetition, and a phase only of Te is easily formed (for example, Te ₉₀ Ge ₁₀ is always separated into Te and GeTe. To). Since the Te phase has a crystallization temperature of room temperature or lower, it causes a problem of destabilizing the amorphous phase. Also, as a result of phase separation, the melting point and crystallization rate of the entire system change,
There arises a problem that the recording sensitivity and the erasing sensitivity change. Therefore, how to fix the excessive Te added to lower the melting point to make the composition hard to move has a great influence on the repeated characteristics, the CNR, and the erasing rate variation with time. That is, even in the case of the Ge—Sb—Te system recording film of the conventional example, it is not enough that only three elements are contained, and the composition ratio must be selected in consideration of the rewriting characteristics. there were.

Recording members containing oxides also have the drawbacks described below. That is, the erasing rate is reduced by repeated recording and re-erasing. A rewritable optical disc is normally recorded in an initial crystalline state and an amorphous recording state. Erasure is made crystalline as in the initial state. The crystalline-amorphous phase transition of the recording member is achieved by changing the conditions of laser slow cooling-quick cooling. That is, after heating with laser light, it becomes crystalline by slow cooling and becomes amorphous by rapid cooling. Therefore, the film goes through a crystalline state and an amorphous state many times due to repeated recording and erasing. In this case, when an oxide is present in the film, the mobility of the chalcogenide is reduced due to the high viscosity of the film, and segregation of the film composition is likely to occur. In addition, the presence of oxides reduces the heat transfer of the film itself,
A temperature distribution difference occurs between the laser light incident side and the opposite side in the film thickness direction, and segregation of the film composition also occurs. For these reasons, the oxide-containing film has a drawback that the characteristics gradually change due to repeated recording and erasing.

The present invention overcomes the drawbacks of the conventional composition consisting of an oxide material and a chalcogenide (low C / N, insufficient erasing rate, poor moisture resistance, poor heat resistance, insufficient repeatability). However, the present invention provides an optical information recording method having excellent rewriting characteristics.

[0011]

In order to solve the above-mentioned problems, the present invention provides Te-Ge-Sb as a recording layer on a substrate.
1. An optical information recording member having a thin film formed of a composition of a system is adopted, and the thin film has a composition ratio of Te, Ge, and Sb in which the atomic ratio is Te, Ge, and Sb.
It is in the region connecting the points D and E, and the Te concentration is 50
% Or more and free Te does not exist, that is, a composition belonging to a region in which Te is less than the composition line connecting two compound composition points of GeTe and Sb ₂ Te ₃ .

During recording and erasing, laser irradiation is performed with the same pulse width during recording and erasing, or in the case of crystallization, laser irradiation with a pulse width relatively longer than that of amorphization is performed to perform recording. Sometimes, after irradiating with a laser beam and heating, it is rapidly cooled to locally change the recording layer in the irradiated part to an amorphous state, and during erasing, a laser beam is irradiated and heated, and then the amorphous part is crystallized by slow cooling. Switch to a state.

[0013]

The feature of the recording material thin film applied to the optical information recording method of the present invention is that Sb is added to the Te-Ge system to fix excess Te. That is, the Te concentration is 50
%, The stable structure of the system is in the form of GeTe-Te, which has a low melting point Te (melting point 450 ° C.) and a high melting point stoichiometric compound GeTe.
(Melting point of 725 ° C.), the two phases having greatly different characteristics are separated. Therefore, when Sb is added, this Sb functions to combine with Te to form the stoichiometric compound Sb ₂ Te ₃ .

When this excess Te is fixed as Sb ₂ Te ₃ , in the Te-Ge-Sb system having a Te concentration of 50 at% or more, its melting point is around 600 ° C. That is, the material phases that can stably exist in the vicinity are Ge ₂ Sb ₂ Te ₅ (melting point 630 ° C.), GeSb ₂ Te, which are ternary compounds.
₄ (melting point 615 ° C.), GeSb ₄ Te ₇ (melting point 605
C) and the melting points of the _binary compounds Sb ₂ Te ₃ (melting point 622 ° C.) are very close to each other, and it is expected that phase separation hardly occurs even if the melting-solidification process is repeated. See Te
Even if the remaining Sb that fixed the
Since it is 0 ° C., there is an advantage that it is easily mixed with the above compound group.

This temperature (around 600 ° C.) is higher by about 200 ° C. than the melting points of Te-Ge system (eutectic point 375 ° C.) and Te-Sn system (eutectic point 405 ° C.) having a composition near the eutectic. However, the crystallization transition temperature of a glass substance is usually said to be 1/2 to 2/3 of the melting point in absolute temperature, and it is known that there is a strong correlation between the melting point and the crystallization transition temperature. Sui, "Science of Glass Amorphous P51). That is, by increasing the melting point, the thermal transition temperature (the temperature at which the amorphous state changes to the crystalline state by heating) of the composition having the above-mentioned composition rises, and Stability is also increased:
When a Te-Ge-Sb-based thin film is used as a rewritable memory medium (usually, the crystalline state is heated and rapidly cooled to become amorphous, and this is used as a recording state), the recording portion in the amorphous state is heated. On the other hand, it becomes stable, so that the stability of the recorded information for a long period of time is secured.

On the other hand, the melting point of 600 ° C. is Te-Ge. Te-Sn or Te ₅₀ Ge ₅₀ (melting point 7
25 ° C.) and the melting point of Te ₅₀ Sn ₅₀ (melting point 750 ° C.) are about 150 ° C. lower. This means that Te-Ge-Sb
When a system thin film is used as a rewritable memory medium, the energy required for recording is small when performing amorphized recording (heating a minute portion of the memory thin film in a crystalline state and then rapidly cooling it to become amorphous). means.

From the above, by adding Sb to the Te-Ge system to fix excess Te,
By setting the concentration of 50% or more to 50% or more, the recording sensitivity (amorphous sensitivity) due to laser light irradiation is not significantly reduced, and the thermal stability of the recording signal is excellent, and recording (amorphization) and erasing (crystallization) are performed. A rewritable memory medium that is less likely to undergo phase separation during the process is obtained, and rewritable recording having excellent repetitive recording and erasing characteristics can be performed using the rewritable memory medium.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A recording member used in the optical information recording method of the present invention will be described below with reference to the drawings with reference to the drawings.

The recording layer of the optical information recording member applied to the optical information recording method of the present invention is made of Te-Ge-Sb. In the present invention, Te exists in the form of being bound to Ge or Sb. It is considered that this is the component mainly responsible for the optical density change in the amorphous state and the crystalline state.

In the Te-Ge system, the stoichiometric composition of T
The melting point of e ₅₀ Ge ₅₀ is about 725 ° C., and a large amount of energy is required to heat and melt this, and to rapidly cool it to an amorphous state, for example, a large laser power is required when laser light is used. On the other hand, at the eutectic composition point, the melting point is about 375 ° C., and the laser power required for recording can be small. However, as described above, in this eutectic composition, since Te is excessively present, Te-TeGe separation is likely to occur, and when recording (amorphization) and erasing (crystallization) are repeated, a partial composition in the film is generated. Cause non-uniformity. Since it is natural that different compositions have different optical characteristics, the nonuniformity of the composition is optically detected as noise.

As described above, the melting point of the Te-Ge-Sb system is about 600 ° C to 630 ° C, although it varies somewhat depending on the composition. Therefore, the laser power required for recording is smaller than that of the Te-Ge system. In addition, there is a merit that the crystallization speed is improved by combining Te with Sb. This is because, for example, in the eutectic composition, there is free Te that is not associated with either Te-Ge or Te-Sb bond.
This is because the coordination of 3 contains 3 coordinations in the melt and only 2 coordinations are stable in the crystal. That is, it is considered that when crystallizing by removing the melt from the melt, Te in the melt has three-coordinates, which are temporarily retained when cooled. Te is -Te-T in the crystalline state.
Since the two-coordinate chain structure of e-Te- is stable, it is necessary to reassemble the once-frozen three-coordinate bond into two-coordination, which slows the crystallization rate. On the other hand, when Sb is added, it is considered that the Te-Sb bond is immediately formed and fixed upon solidification from the melt, so that the crystallization rate is improved. By increasing the crystallization speed, the time required for erasing information can be shortened and a rewritable memory medium that can be used practically can be realized.

Since the amount of Sb added fixes the remaining excess Te bound to Ge, the required concentration is governed by the amount of Te / Ge. FIG. 1 shows the proper range of the recording member composed of Te-Ge-Sb of the present invention. In FIG. 1, each point has the following composition.

A ₁ point: (Te ₈₀ Ge ₅ Sb ₁₅ ) B ₁ point: (Te ₅₅ Ge ₅ Sb ₄₀ ) C ₁ point: (Te ₄₅ Ge ₁₅ Sb ₄₀ ) D ₁ point: (Te ₄₅ Ge ₄₀ Sb ₁₅₎ ) E ₁ point: (Te ₅₃ Ge ₄₀ Sb ₇ ) The amount of Sb added varies depending on the composition ratio of Te-Ge-Sb. For example, in the high Ge concentration region, the crystallization rate of Te-Ge is high, so the Sb concentration is relatively low, and in the region with a small amount of Ge component, the crystallization rate is low, so it is necessary to add a relatively high concentration of Sb. When the content is out of the above range, Ge-TeGe having a high melting point serves as a base material on the Ge (rich) side, for which extremely high power is required for recording and it is unsuitable as a memory material. On the Te (rich) side, the thermal transition temperature from amorphous to crystal is lowered to around 100 ° C., and a memory medium excellent in thermal stability cannot be obtained.
Further, on the Sb (rich) side, it becomes difficult to obtain optical contrast between the signals of the recorded portion and the unrecorded portion, and sufficient recording characteristics cannot be obtained.

For the reasons described above, the present invention is limited to the range surrounded by the points A ₁ -B ₁ -C ₁ -D ₁ -E ₁ in FIG. That is, Te-Ge within this range
When the composition of —Sb is used, information can be recorded, erased and rewritten practically by utilizing the reversibility of crystalline and amorphous.

Next, point A in FIG.₂ -B₂ -C₂ -D₂ −
E₂ The area surrounded by is described. This area
Is point A in FIG.₁ -B₁ -C₁ -D₁ -E₁ Surrounded by
The range is more practical than the range. In Figure 1
A₂ , B₂ , C₂ , D ₂ , E₂ The composition of each point of
It is shown below.

A ₂ points: (Te ₇₈ Ge ₈ Sb ₁₄ ) B ₂ points: (Te ₆₂ Ge ₈ Sb ₃₀ ) C ₂ points: (Te ₅₀ Ge ₂₀ Sb ₃₀ ) D ₂ points: (Te ₅₀ Ge ₃₀ Sb ₂₀₎ ) E ₂ point: (Te ₆₀ Ge ₃₀ Sb ₁₀ ). This region is a composition range of Te ≧ 50 at%, and the thermal transition temperature from amorphous to crystal is 130 ° C. to 195 ° C. A ₂ has the lowest transition temperature, B ₂ , C ₂ , D ₂ ,
The thermal transition temperature rises as the Ge or Sb concentration increases in the E ₂ direction. Especially, the dependence on the Ge concentration is large. This point A is ₂ -B ₂ -C in a region surrounded by ₂ -D ₂ -E ₂ is excellent in both thermal stability and laser beam recording sensitivity. In Figure 1, for a outside the range of _{A 2 -B 2 -C 2 -D 2} -E 2, and the composition in the range of A ₁ -B ₁ -C ₁ -D ₁ -E _1, application , It is necessary to use them properly according to the purpose. That is, of the above compositions, Ge (r
ich) side requires a little larger laser power, but has better thermal stability. Further, on the Te (rich) side, a memory medium having extremely low thermal stability but extremely high sensitivity can be obtained.

The effect of adding Sb to the Te-Ge system generally raises the thermal transition temperature, which means the thermal stability of the memory medium, and lowers the melting point of the film to facilitate amorphization.

For the reasons described above, the Te-G of the present invention is used.
The optimal composition of e-Sb is limited. Next, a method for manufacturing the optical information recording member according to the present invention will be described. FIG. 2 is a schematic view of a cross section of an optical disc formed by using the recording layer of the present invention. In FIG. 2, reference numerals 1 and 5 denote substrates, and it is possible to use a transparent base material such as polycarbonate, acrylic resin, glass or polyester. Reference numerals 2 and 4 are protective layers provided inside the substrates 1 and 5, and various oxides, sulfides, and carbides can be used. The protective layers 2 and 4 prevent thermal deterioration of the substrate due to repeated recording and erasing of the recording film 3 interposed therebetween.
The recording film 3 is protected from humidity. Therefore, the material and film quality of the protective layers 2 and 4 are determined from the above viewpoints. The recording film 3 is formed by vapor deposition, sputtering or the like. In the case of vapor deposition, it is preferable to use a 3-source vapor deposition machine capable of vapor depositing each composition independently, because a uniform film can be formed. The film thickness of the recording film 3 is set to a value that allows a large matching with the optical characteristics of the protective layers 2 and 4, that is, a large difference in reflectance between the recorded portion and the unrecorded portion.

The present invention will be described in detail below with reference to specific examples. (Example 1) Te, Ge, and Sb were simultaneously vapor-deposited from the respective sources on a substrate by using an electron beam vapor deposition machine capable of vapor deposition of three sources. The base material used is 0.3 mm thick x 8 m
On a glass plate of m, vapor deposition was carried out at a rotation speed of 150 rpm of a substrate with a vacuum of 1 × 10 ⁻⁵ Torr and a film thickness of 1000 Å.
The evaporation rate from each source is Te, Ge, Sb in the recording film.
Was changed to adjust the ratio of the number of atoms of. The composition ratios in Table 1 are values converted from the deposition rate,
When a typical composition was analyzed by an X-ray microanalyzer (XMA), a quantitative result almost similar to the charged value was obtained. Therefore, the charging composition in the table seems to be the same in the film. The evaluation method of the test piece prepared by this manufacturing method is described below. [Transition temperature] The transition temperature means a temperature at which an amorphous film immediately after vapor deposition becomes crystalline by heat. The measurement was performed using a device capable of measuring the transmittance of the film, at a temperature at which the transmittance started to decrease when the temperature of the test piece was raised by a heater at a temperature rising rate of 1 ° C./SEC. A high transition temperature means that the film is thermally stable. [Blackening and whitening characteristics] The blackening characteristics indicate the transition rate from the amorphous to crystalline transformation, and the whitening characteristics indicate the transition sensitivity from crystalline to amorphous. It is a thing.
The measurement was performed by using a device in which laser light was focused on a recording film on a φ8 mm glass piece by using a lens and the sample piece could be moved vertically and horizontally. 45 spots of laser light
× 0.4 μm rectangle, pulse width 200 ns (light emission cycle is 500 times per second), power density 10.6 mW / μ
m ² and wavelength were 900 nm. As for the blackening characteristic, the speed of transformation (amorphous to crystalline) is observed when the test piece is moved relatively slowly, and the speed is sufficiently high, and the contrast ratio between the unrecorded portion and the recorded portion is sufficiently large. The item was marked as ◎. “X” indicates that the blackening does not occur even if it is gently moved, or that the contrast ratio is small. ○ and △ are located between ◎ and ×. In this qualitative expression, the practical blackening characteristic is ◯ or higher.

Next, the whitening characteristics will be described. When observing the whitening characteristics, the material is once blackened, and the test piece is quickly moved over the blackened portion to form a rapidly cooled state, and whitening (from crystalline to amorphous) is performed. When the whitening state is ⊚, the whitening occurs even when the moving speed is relatively slow, and the contrast ratio between the amorphous part and the crystalline part is large. X indicates that no whitening occurs. ○ and △ are located between ◎ and ×.

In the above experiment, since the light emission cycle is 500 times / second, when the moving speed is slow, the interval between the part irradiated by the previous pulse and the part irradiated this time is small, and the irradiation is performed before. Due to the influence of heat conduction from the part, the cooling rate is slightly lowered and it becomes easier to crystallize. On the other hand, when the moving speed is high, the part irradiated with the previous irradiation and the part irradiated with the next irradiation are thermally completely cut off, and the cooling speed is increased to easily become amorphous.

Therefore, when the moving speed is sufficiently high, according to the above-mentioned expression, when the blackening and whitening characteristics are very excellent, ⊚ and ⊚ are obtained. , Neither can be ◎,
Desirable materials are ⊚, ∘, ⊚, and Δ, which are somewhat excellent in blackening characteristics. Under the above conditions, both crystallization and amorphization could be realized by laser irradiation with the same pulse width. Table 1 shows the results of the transition temperature and the blackening and whitening characteristics of the film prepared in the range of the present invention.

[0033]

[Table 1]

As is clear from the results of Table 1, the Te-Ge-Sb recording thin film within the scope of the present invention can be blackened and whitened by laser irradiation with the same pulse width. That is, the recording member within this range can be in either an amorphous state or a crystalline state by appropriately selecting the heating conditions, for example, the irradiation intensity of the laser beam to be irradiated and the irradiation time. Yes, it is possible to record and erase information optically. (Example 2) An optical disk was experimentally produced by using a 1.2 mm × φ200 mm thick polycarbonate resin base material having a light guide track as a base material and a thin film of Te ₆₅ Ge ₁₅ Sb ₂₀ composition as a recording film. .

First, a ZnS thin film as a heat-resistant layer was vapor-deposited on a substrate at 900 Å, a recording layer was vapor-deposited thereon to a thickness of about 1000 Å, and a ZnS thin film as a heat-resistant layer was also vapor-deposited at 1800 Å thereon. A signal was recorded by irradiating a laser beam narrowed down from the substrate side of this optical disk using an optical system, and erasing was immediately performed. Prior to recording, an elliptical laser beam with a spot shape of 1 μm × 10 μm
Irradiation was performed along the track with an intensity of 4 mW to crystallize the recording film in the track, and then a laser beam focused to 0.9 μmφ was applied with an intensity of 8 mW. Recording frequency is 2MH
The rotation speed of z and the disk is 5 m / s. At this time, the irradiated portion was amorphized and a signal was recorded along the track. When C / N was measured with a spectrum analyzer, 50 dB was obtained. When the above elliptical spot was irradiated on this track, the signal was completely erased. In the above example, the effective irradiation time is considered to be the length of the spot divided by the rotational linear velocity,
In this case, laser irradiation was performed for 180 ns in the case of amorphization and 2 μs for crystallization. (Example 3) Using the optical disk of Example 2, a life test was conducted under the conditions of 80 ° C and 80% RH. The test method is to record the information in advance, and to hold C under the above conditions.
The deterioration of / N was observed. The decrease in C / N after one month is-
It was a negligible level of 0.5 dB. (Example 4) The recording / erasing repetition characteristics of the optical disk of Example 3 were evaluated. The reduction in C / N after recording and erasing 100,000 times was about 1 dB.

[0036]

As described above, according to the present invention, the heat resistance and the moisture resistance are extremely excellent, and even when recording and erasing are repeated, the recording / erasing / rewriting characteristics change due to the phase separation, the increase of the noise component, and the It is possible to realize extremely excellent rewriting characteristics practically without breaking the film.

[Brief description of drawings]

FIG. 1 is a composition diagram showing a composition range of an optical information recording member to which the present invention is applied.

FIG. 2 is a cross-sectional view showing an example of a film structure of an optical information recording member to which the present invention is applied.

[Explanation of reference numerals] 1 substrate 2 protective layer 3 recording layer 4 protective layer 5 substrate (protective plate)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Susumu Sanai 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (3)

[Claims] 1. A substrate comprising at least three elements of Te, Ge and Sb, and Te, Ge and S thereof.
An optical information recording member having a material layer selected as a recording layer in which the atomic ratio of b is 50% or more in Te concentration and a free Te-free composition range is used, and a laser beam is applied to the recording layer. Rewriting, which is characterized by irradiating the irradiated part with light and heating the irradiated part to make it amorphous, and then gradually cooling to crystallize, thereby causing a change in optical properties based on the occurrence of a reversible phase transition. Possible optical information recording method. 2. The rewritable optics according to claim 1, wherein the laser irradiation is performed during crystallization for the same time as during amorphization, or for a relatively longer time than during amorphization. Information recording method. 3. The rewritable optical information recording according to claim 1, wherein the recording layer is irradiated with an elliptical laser spot before the information recording to convert the recording layer to an erased state. Method.