JPH06166268A - Optical information recording medium and its manufacture - Google Patents

Abstract

PURPOSE:To obtain an optical information recording medium wherein an excellent property as a phase changing type optical recording medium is provided and an erasing ratio and a repetitive characteristic are especially rapidly improved. CONSTITUTION:In an erasable optical information recording medium which records, erases, and reads out information by irradiation with laser beams, a recording layer contains four elements series phase changing type recording materials containing at least Ag, In, Sb, Te as main components, and an AgSbTe2 crystalline phase which is a stoichiometric composition or near that exists in unrecording and erasing. Then, a target consisting of AgInTe2, and Sb is used by taking principally such a recording medium, and a film is manufactured by a sputtering method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording medium, in particular a phase change type information recording medium, which causes a phase change in a recording layer material by irradiating a light beam to record and reproduce information. The present invention also relates to a rewritable information recording medium, which is applied to optical memory-related equipment.

[0002]

2. Description of the Related Art As one of optical memory media capable of recording, reproducing and erasing information by irradiation of electromagnetic waves, especially laser beams, so-called phase change utilizing a transition between a crystalline-amorphous phase or a crystalline-crystalline phase. Recording media are well known. In particular, since it is possible to overwrite with a single beam, which is difficult for a magneto-optical memory, and the optical system on the drive side is simpler, research and development has recently become active. As a typical example, USP3
Ge-Te, G, as disclosed in 530441.
e-Te-Sn, Ge-Te-S, Ge-Se-S, G
e-Se-Sb, Ge-As-Se, In-Te, Se
Examples include so-called chalcogen alloy materials such as —Te and Se—As. Further, for the purpose of improving stability and high-speed crystallization, Au is added to the Ge--Te system (Japanese Patent Laid-Open No. 61-1969).
2), Sn and Au (JP-A-61-270190),
For the purpose of proposing a material to which Pd (Japanese Patent Laid-Open No. 19490/1987) is added and improving the recording / erasing repetition performance,
-Te-Se-Sb and Ge-Te-Sb with specified composition ratios (JP-A-62-73438, JP-A-63-22)
8433) has also been proposed. However,
None of them can satisfy all of the characteristics required for a phase-change rewritable optical memory medium. In particular, improvement of recording sensitivity and erasing sensitivity, prevention of reduction of erasing ratio due to unerased portion during overwriting, and prolongation of service life of recorded and unrecorded areas are the most important issues to be solved.

Japanese Unexamined Patent Publication No. 63-251290 proposes a recording medium having a recording layer composed of a multi-component compound single phase whose crystal state is substantially ternary or more. Here, the term “substantially ternary or higher multi-component compound monolayer” refers to a compound having a stoichiometric composition of ternary or higher (for example, In ₃ SbTe ₂ ) in the recording layer.
It is supposed to contain 0 atomic% or more. It is said that the recording and erasing characteristics can be improved by using such a recording layer. However, it has drawbacks such as a low erasing ratio and the laser power required for recording and erasing has not been sufficiently reduced. Due to these circumstances, the erase ratio is high,
It has been desired to develop a recording material suitable for high sensitivity recording and erasing.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides an information recording medium having a high erasing ratio and capable of repeating recording-erasing with low power, and a manufacturing method thereof. Is.

[0005]

As a result of intensive studies to solve the above problems, the present inventors have found a recording material which meets the above-mentioned object and a manufacturing method thereof. That is, the present invention is
(1) In a rewritable optical information recording medium that records, erases, and reproduces information by irradiating a laser beam, the recording layer is mainly a quaternary phase-change recording material containing at least Ag, In, Sb, and Te. AgSbTe ₂ which is contained as a component and has a stoichiometric composition at or near unrecorded and erased contents.
An optical information recording medium having a crystalline phase, (2) AgSbTe which has a stoichiometric composition at or near unrecorded and erased states.
The optical information recording medium according to (1), which has a structure in which _two crystalline phases and an amorphous phase composed of at least In and Sb are mixed, and (3) the recording layer is at least Ag, In, Sb, and T.
It has a uniform amorphous phase at the time of recording and has a stoichiometric composition or close to that of AgSbTe at the time of erasing.
The optical information recording medium according to (1), which has a structure in which _two crystalline phases and an amorphous phase composed of at least In and Sb are mixed, and (4) the same orientation of AgSbTe _{2 in} the recording layer in the initialized or erased state. The optical information recording medium according to (2) or (3), wherein the size of the region is 2000 Å to 10000 Å, (5) The composition and chemical structure at the time of erasing are mainly

[0006]

[Equation 3]

However,

[0008]

[Equation 4]

0.4 ≦ X ≦ 0.55 0.5 ≦ Z ≦ 2.5 −0.15 <δ <0.1 The optical information recording medium according to the above (1) to (3), ( 6) The optical information recording according to any one of (1) to (3), which has a recording layer, a protective layer, and a reflection heat dissipation layer on a substrate, and the protection layer between the recording layer and the reflection heat dissipation layer is AlN. Medium,
(7) In manufacturing a rewritable optical recording medium that records, erases, and reproduces information by irradiating a laser beam, a recording layer is formed by a sputtering method using a target mainly composed of AgInTe ₂ and Sb. (8) A method for producing an optical information recording medium according to (7), wherein after the film formation, initialization is first performed with an Ar laser, and then initialization is performed with a semiconductor laser. Is related to.

In the present invention, as the composition of the recording layer, the value obtained by measuring the recording film by fluorescent X-ray was used.
Analytical methods such as Auger electron spectroscopy are possible. In that case, it is necessary to calibrate with the value obtained by fluorescent X-ray.

X-ray diffraction or electron beam diffraction is suitable for observing the substance contained in the recording layer. Electron diffraction is suitable for observing the crystalline state. That is, as the determination of the crystalline state, the crystalline state is set when a spot-like or Debye ring-shaped pattern is observed in the electron beam diffraction image, and the amorphous state is set when a ring-shaped pattern or halo pattern is observed. The crystallite diameter can be obtained from the half width of the X-ray diffraction peak using Scherrer's formula. Further, the crystallite size can be obtained from TEM observation. To explain the present invention in more detail, the recording layer according to the present invention contains at least Ag, In, Sb, and Te as constituent elements. Further, the disk characteristics can be improved by adding other additive elements. For example, by adding a transition metal element such as IVa or Va (Ti, V, Cr, Zn, Nb, Mo, etc.), the crystallization rate can be easily controlled, and the structural stability and the repeatability can be improved. . The recording layer is often amorphous at the time of film formation, but is initialized by heat treatment after forming the medium.

FIG. 1 is a diagram schematically showing the optimum stable state (unrecorded portion) of the recording layer based on the results of electron microscope observation, electron beam diffraction and X-ray diffraction. An amorphous phase composed of AgSbTe ₂ and at least In and Sb, which are at or near the stoichiometric composition of the crystal phase, exist in a mixed phase state. The structure of this recording layer was determined as follows.

Select the crystal plane spacing from the electron beam diffraction pattern of the initialized portion or erased portion of the recording layer to select.
ed Powder Diffraction Dat
afor Metals and Alloys (Co
piled by the Joint Commi
ttee on Powder Diffratio
(n Standards) well agrees with the AgSbTe ₂ crystal data in the range of measurement error. In this electron beam diffraction pattern, a halo pattern slightly appears in addition to the diffraction points, indicating that the recording layer is in a state in which a crystalline phase and an amorphous phase are mixed. FIG. 2 is a TEM observation photograph, showing an example of a state in which a crystalline phase and an amorphous phase are mixed. Therefore, it can be seen that the crystal part seen in this TEM photograph is the AgSbTe ₂ crystal phase.

On the other hand, when this recording layer is annealed with an electron beam under a pressure of 1 × 10 ^-4 Pa to crystallize the amorphous phase shown in FIG. 2, the electron beam diffraction pattern shows AgSbTe ₂
In addition, a diffraction pattern corresponding to the hexagonal InSb crystal comes to appear. From this, it is clear that the mixed phase amorphous phase found in the recording layer in the initialized or erased state is composed of at least In and Sb. The size of the region of the recording layer in the initialized state or the erased state, which has the stoichiometric composition or is close to the stoichiometric composition and faces the same direction of AgSbTe ₂ , was evaluated by taking a dark field image of TEM. If the size of this region is less than 2000 Å, the repetitive properties deteriorate, and if it exceeds 10,000 Å, the C / N decreases.

The mixed phase state is at least In and Sb in the AgSbTe ₂ crystal phase which is at or near the stoichiometric composition.
AgSb dispersed in the amorphous phase composed of at least In or Sb
The Te ₂ crystal phase can be dispersed or mixed.

Although the mechanism of forming such a structure is not clear, it can be considered as follows. When Ag, In, Sb, Te, and a quaternary system are solidified from a molten state at a constant cooling rate, phase separation into a metastable state AgSbTe ₂ phase and an In-Sb phase and an AgSbTe ₂ crystal with a high crystallization rate Therefore, the AgSbTe ₂ crystal phase and the amorphous phase composed of at least In—Sb coexist.
At this time, when the crystallization rate of the In-Sb phase is slower than the cooling rate, it becomes an amorphous phase.

The amorphous phase is generally said to have a highly isotropic structure. On the other hand, since AgSbTe ₂ also has a cubic crystal structure, which is an isotropic crystal structure, for example, when it is rapidly cooled from a high temperature by a laser beam to become an amorphous phase (transition from recording to metastable state), a uniform phase at high speed is obtained. A change occurs, resulting in an amorphous phase with little physical or chemical variation. It is difficult to analyze the fine structure of the amorphous phase, and the details are unknown. For example, the stoichiometric composition of the amorphous phase or AgSbTe close thereto is used.
It is considered that a combination of ₂ and an amorphous phase composed of at least In and Sb, or a completely different single amorphous phase is formed.

On the contrary, in the transition from the highly uniform amorphous phase to the isotropic crystal structure (transition from erase to stable state), crystallization occurs uniformly, and therefore the erase ratio is very high. It will be expensive. In addition, in the mixed state as shown in FIG. 1, since the melting point is lowered due to the size effect,
A phase transition can occur at relatively low temperatures. That is,
As a recording medium, recording sensitivity is improved.

Such a mixed phase state is caused by AgInTe ₂ and S.
It can be prepared by using b and b as raw materials. The recording film during film formation reflects the chemical structure of the raw materials and is Ag
It is considered to be an amorphous phase of InTe ₂ and Sb. This is because AgInTe ₂ and Sb are formed by heat treatment at a temperature near the crystallization transition point (190 to 220 ° C.).
It can be confirmed that the crystal phase of Initializing such a recording film with a laser beam of appropriate power, heat, or the like creates a uniform amorphous mixed phase of AgSbTe ₂ and at least In and Sb, which has a fine stoichiometric composition or is close to the stoichiometric composition. be able to. That is, in a system containing at least Ag, In, Sb, and Te, an appropriate structure can be obtained by changing the structure by causing a substitution reaction as an initialization process for the recording film during film formation. This process consists of heating the recording film during film formation, bringing it into a molten or near-active state, and then cooling it at an appropriate cooling rate. If the cooling rate is too fast, the recording layer will have an amorphous structure. Conversely, if it is too slow, the desired fine mixed phase structure will not be obtained, and the phase composed of In and Sb will also crystallize.

Recording / erasing is performed at a low linear velocity (1 m / s to 5.6 m /
s), the range of X, Z, δ in the above formula is
0.4 ≦ X ≦ 0.55, 0.5 ≦ Z ≦ 2.5, -0.1
The range of 5 ≦ δ ≦ 0.1 is preferable. More preferable ranges are 0.4 ≦ X ≦ 0.55, 0.7 ≦ Z ≦ 2.2, −0.
15 <δ <0.05, more preferably 0.42
≦ X ≦ 0.5, 0.7 ≦ Z ≦ 2.2, −0.1 <δ <
It is 0.02.

The recording layer of the present invention can be formed by various vapor deposition methods such as vacuum vapor deposition, sputtering, plasma CVD, photo CVD, ion plating and electron beam vapor deposition. In addition to the vapor phase growth method, a wet process such as a sol-gel method can be applied. The thickness of the recording layer is 100 to 10000Å, preferably 200 to 30
It is good to set it to 00Å. When the thickness is less than 100Å, the light absorption ability is remarkably lowered and the recording layer cannot serve as a recording layer.
If it is thicker than 10000Å, uniform phase change at high speed is difficult to occur.

As the sputtering target, A
gInTe ₂ target with Sb chip on it,
Or embedded, Sb target AgInT
Various forms are conceivable, such as one with an e ₂ chip mounted or embedded, a mixture of AgInTe ₂ and Sb, a laminated body, a sintered body thereof, and any of these methods may be used. Further, a target mainly containing AgInTe ₂ and Sb may be prepared from Ag, In, Sb, Te alone or a mixture of these compounds. The composition ratio of the four elements, the size and number of chips, the mixing ratio of AgInTe ₂ and Sb, the area ratio, and the like can be appropriately determined depending on the sputtering apparatus, conditions, and the like. At that time, depending on the composition of the target, Ag, In, Sb, or Te alone or a binary compound thereof may be mixed in the target, but this does not significantly affect the performance of the recording film.
Note that AgInTe ₂ does not necessarily mean the stoichiometric composition.

The present invention will be described below with reference to the accompanying drawings.
FIG. 3 shows a configuration example of the present invention. A heat-resistant protective layer (2), a recording layer (3), a heat-resistant protective layer (4), and a reflection / heat dissipation layer (5) are provided on a substrate (1). It is not always necessary to provide the heat-resistant protective layer on both sides of the recording layer, but it is desirable to provide the heat-resistant protective layer (2) when the substrate is a material having low heat resistance such as polycarbonate resin.

The substrate material is usually glass, ceramics,
Alternatively, it is a resin, and a resin substrate is preferable in terms of moldability and cost. Typical examples of the resin are polycarbonate resin, acrylic resin, epoxy resin, polystyrene resin,
Examples thereof include acrylonitrile-styrene copolymer resin, polyethylene resin, polypropylene resin, silicone resin, fluorine resin, ABS resin, urethane resin, and the like, but polycarbonate resin and acrylic resin are preferable in terms of processability and optical characteristics. . The shape of the substrate may be disk-shaped, card-shaped or sheet-shaped.

Materials for the heat resistant protective layer include SiO and S.
iO ₂ , ZnO.SnO ₂ , Al ₂ O ₃ , TiO ₂ , In ₂ O ₃ ,
Metal oxides such as MgO and ZrO ₂ , Si ₃ N ₄ , Al
Nitride such as N, TiN, BN, ZrN, ZnS, In
₂ S ₃ , sulfides such as TaS ₄ , SiC, TaC, B ₄ C,
Carbides such as WC, TiC, and ZrC, diamond-like carbon, or a mixture thereof can be used. Especially Al
A protective layer having a thermal conductivity of 1 W / cm · K or more such as N, BN, SiC, and C is suitable. It is extremely difficult to measure the thermal conductivity of a thin film of the order of μm or less, particularly an insulating thin film itself used for a heat-resistant protective layer. Therefore, the thermal conductivity described in the present invention is a value measured by the vertical direct method or the laser flash method, with the bulk state of the same substance being measured.

A material having a value of 1.0 W / cm · deg or more was thinned by an appropriate film-forming means described in the present specification and used as the upper heat-resistant protective layer. These materials may be used alone as the protective layer, or may be a mixture with each other. Further, it may contain impurities as necessary. However, the melting point of the heat-resistant protective layer needs to be higher than that of the recording layer. If necessary, the protective layer may be multi-layered. Such a heat resistant protective layer may be formed by various vapor phase growth methods such as vacuum deposition method, sputtering method, plasma CVD method, photo CVD method, ion plating method,
It can be formed by an electron beam evaporation method or the like. The thickness of the heat-resistant protective layer is 100 to 5000Å, preferably 200.
~ 3000 Å is recommended. When it becomes thinner than 100Å, it does not function as a heat resistant protective layer, and conversely it becomes 5
When the thickness is more than 000Å, the sensitivity is lowered and the interfacial peeling is likely to occur.

As the reflection / heat dissipation layer, a metal material such as Al, Au, Ag, or an alloy thereof can be used. The reflection / heat dissipation layer is not always necessary, but it is desirable to provide it in order to release excess heat and reduce the heat load on the recording medium itself. Such a reflective heat dissipation layer is formed by various vapor deposition methods such as vacuum deposition method, sputtering method, plasma CVD method, photo CVD method, ion plating method,
It can be formed by an electron beam evaporation method or the like. The thickness of the reflective heat dissipation layer is 100 to 3000 Å, preferably 500.
~ 2000Å is recommended. When the thickness is less than 100 Å, the function of the reflection and heat dissipation layer is not fulfilled. On the contrary, when the thickness is more than 3000 Å, the sensitivity is lowered and the interface peeling is likely to occur.

A method for initializing the optical information recording medium is as follows.
Various methods such as an r laser method, a semiconductor laser method, and a flash lamp method can be used. In particular, the method of first performing the initialization with the Ar laser and then the initialization with the semiconductor laser is excellent in the erase ratio. The reason for this is not clear, but it is considered that the structure of the recording layer is changed by combining the initialization methods. The power of Ar laser is 3
The range of 00mW to 4W, the linear velocity of the disk is 1.0m /
Range of s to 10m / s, laser feed speed is 1um
A range of / revolution to 20um / revolution is suitable. The power of the semiconductor laser is suitably in the range of 5 mW to 20 mW, and the linear velocity is suitably in the range of 1.2 m / s to 10 m / s.

Initialization using a large-diameter LD (semiconductor laser) is excellent in film homogeneity, disk signal characteristics, and productivity. The beam diameter is preferably 1.0 to 5.0 μm in width and 10 to 300 μm in length. Power is 100 to 3
The range of 000 mW and the linear velocity of 1 to 20 m / s are suitable. Electromagnetic waves used for recording, reproduction and erasing include laser light, electron beams, X-rays, ultraviolet rays, visible rays, infrared rays,
Various types such as microwaves can be used, but a small and compact semiconductor laser is most suitable for mounting on a drive.

[0030]

EXAMPLES The present invention will be specifically described below with reference to examples. Example 1 ZnS.SiO ₂ (20 m) as a lower heat-resistant protective layer was formed on a polycarbonate disk substrate with a 3.5-inch groove.
ol%) is 2000 liters, a recording layer made of Ag, In, Sb, Te is 350 liters, and AlN is 3 as an upper heat-resistant protective layer.
00 Å, Ag 700 Å as a reflection and heat dissipation layer were sequentially deposited by sputtering. At this time, as the sputtering target for the recording layer, a 6-inch φ target having eight 15 mm □ Sb chips on the AgInTe ₂ target erosion part was used. The composition of the obtained recording layer was represented as follows.

[0031]

[Equation 5]

X = 0.48 Z = 1.9 δ = -0.07 A method using a semiconductor laser and a method using oven annealing were selected as the initialization method, the structure of the recording layer was changed, and the disk characteristics were evaluated. . Initialization with a semiconductor laser was performed using a pickup having a wavelength of 780 nm and an NA of 0.5. The linear velocity of the disk was 1.2 m / s. Initialization power was set to DC 13 mW and the initialization was performed 5 times. In initialization with a semiconductor laser, AgSbTe ₂ crystal phase and In
It was found from the results of TEM observation and electron diffraction that the structure has a mixture of -Sb amorphous phases. It was also found that a crystal phase of AgInTe ₂ and Sb was formed by oven annealing.

The evaluation of the optical disc is carried out at a wavelength of 780 nm and NA.
This was done using a 0.5 pickup. The linear velocity of the disk was 1.2 m / s. Recording frequency 720 kHz,
Alternate overwrite recording of 200kHz signal,
The C / N and erasing ratio of the signal of 20 kHz were used as characteristic values. Table 1 shows the evaluation results. Excellent disk characteristics were obtained when the structure of the recording layer was a mixture of AgSbTe ₂ crystal phase and In—Sb amorphous phase.

[0034]

[Table 1]

Example 2 ZnS.SiO ₂ (20) was formed on a polycarbonate substrate having a pitch of about 1.6 μm and a depth of about 700 Å and a thickness of 1.2 mm and a diameter of 120 mm by RF sputtering.
mol%), protective layer 2000Å, Ag, In, Sb, T
e recording layer 200Å, AlN protective layer 1500Å,
An optical disc was manufactured by sequentially laminating an Ag reflection layer 500Å. At that time, the recording layer was formed in the same manner as in Example 1. Initialization of the optical disk was performed by a semiconductor laser. Initialization power is 5mW to 15mW, linear velocity is 1.3
m / s. The initialization power changed the size of the area facing the same direction.

The evaluation of the optical disk is performed with a wavelength of 780 nm and NA.
This was done using a 0.5 pickup. The linear velocity of the disk was 1.3 m / s. Recording frequency 720kHz, 20
Overwrite recording of 0kHz signal alternately at 720k
The C / N and the erasing ratio of the Hz signal were used as characteristic values. After the disc characteristics were evaluated, TEM observation of the recording layer was carried out, and the size of the region oriented in the same direction was obtained. FIG. 4 shows the relationship between the size of the region of the AgSbTe ₂ crystal oriented in the same direction and the repeating characteristics. C / N is 3 as the characteristic value of the disc repeatability
The number of overwrite recordings with a decrease of dB was used. It can be seen that when the size of the region facing the same direction becomes 2000 liters or less, the repeating characteristics deteriorate rapidly, which is not preferable. From the results of TEM observation and electron diffraction, it was confirmed that the recording layer had a structure in which AgSbTe ₂ crystal phase, In—Sb, and amorphous phase were mixed.

FIG. 5 shows the relationship between the C / N and the size of the region of the AgSbTe ₂ crystal facing the same direction. It has been found that when the size of the region facing the same direction becomes 10,000 Å or more, the C / N decreases, which is not suitable for practical use.

Example 3 ZnS.SiO ₂ (20 m) was used as a lower heat-resistant protective layer on a 3.5-inch grooved polycarbonate disk substrate.
ol% mixture), 2000 Å, recording layer, 1000 Å, AlN 1500 Å as the upper heat-resistant protective layer, and Ag 700 Å as the reflection / heat dissipation layer, which were sequentially laminated and set by the rf magnetron sputtering method. The composition of the recording layer was changed by adjusting the target composition. Table 2 shows the compositions x, z and δ of the recording layer measured by fluorescent X-ray. The recording layers at the time of making the disks were all in an amorphous phase. The recording layer was brought into an initialized state (stable state) with a semiconductor laser beam having a wavelength of 830 nm. Linear velocity 1.3m / s, frequency 0.72MH
z, recorded at 50% duty ratio, frequency 0.2MH
The C / N and erasing ratio of a signal having a frequency of 0.72 MHz when overwriting was performed at z and a 50% duty ratio were measured, and the recording medium was judged. The results are shown in Table 2. In the table, ● indicates C / N ≧ 50 dB, erasing ratio ≧ −30 d
B, ◯: C / N ≧ 40 dB, erasure ratio ≧ −25 dB, Δ: C / N ≧ 30 dB, erasure ratio ≧ −20 dB, ×: C / N <
It shows that it is 30 dB and the erasing ratio is <-20 dB. FIG. 6 shows the relationship between the compositions x and z and the disk characteristics.
7 shows the relationship between δ and the disk characteristics. 0.4 ≦
x ≦ 0.55, 0.5 ≦ z ≦ 2.5, −0.15 <δ <
It can be seen that good disk characteristics are exhibited in the range of 0.1. Further, as shown in Table 2, the recording sensitivity is also very high.

[0039]

[Table 2]

Example 4 The disk was evaluated in the same manner as in Example 1. However, as an initialization method, initialization by Ar laser (300
After performing 0 mW, 8 m / s, 1 μm / rotation, initialization by a semiconductor laser (13 mW, 1.2 m / s,
5 times), initialization by semiconductor laser,
Initialization by Ar laser was selected and compared. Table 3 shows the evaluation results.

[0041]

[Table 3]

As can be seen from Table 3, the erase ratio is improved by performing the initialization by the semiconductor laser after the initialization by the Ar laser.

Example 5 A disk was prepared in the same manner as in Example 1. However, three types of AlN, Si ₃ N ₄ , and SiO ₂ were used as the upper protective layer, and the disk characteristics were compared. The thermal conductivity of each protective layer is AlN: 2.6 W / cmK, Si ₃ N ₄ : 0.
8 W / cmK, SiO ₂ : 0.6 W / cmK. Table 4 shows the initial characteristics of C / N and erase ratio of each disk and the repeating characteristics. It can be seen that the repeatability is improved by using AlN.

[0044]

[Table 4]

[0045]

INDUSTRIAL APPLICABILITY The present invention can provide a phase change type optical recording medium having excellent performance, in particular, a dramatically improved erasing ratio and repetitive characteristics.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing an optimum stable state of a recording layer.

FIG. 2 is an electron micrograph showing a metal structure of the present invention.

FIG. 3 is a diagram showing a configuration example of the present invention.

FIG. 4 is a graph showing the relationship between the size of a region of AgSbTe ₂ crystal oriented in the same direction and the repeating characteristics.

FIG. 5 is a graph showing the relationship between C / N and the size of regions of the AgSbTe ₂ crystal facing the same direction.

FIG. 6 is a graph showing the relationship between composition and disk characteristics.

FIG. 7 is a graph showing the relationship between δ and disk characteristics.

[Explanation of symbols]

 1 substrate 2 heat resistant protective layer 3 recording layer 4 heat resistant protective layer 5 reflective heat dissipation layer

 ─────────────────────────────────────────────────── --Continued front page (72) Inventor Hiroko Iwasaki 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (8)

[Claims] 1. A rewritable optical information recording medium for recording, erasing and reproducing information by irradiating a laser beam, wherein the recording layer is a quaternary phase-change recording material containing at least Ag, In, Sb and Te. Containing as a main component, Ag at or near the stoichiometric composition during unrecorded and erased
An optical information recording medium having an SbTe ₂ crystal phase. 2. A non-recorded and erased AgSbTe ₂ crystalline phase having a stoichiometric composition or a composition close to the stoichiometric composition and at least I
The optical information recording medium according to claim 1, wherein the optical information recording medium has a structure in which amorphous phases composed of n and Sb are mixed. 3. The recording layer comprises at least Ag, In, Sb,
It is made of Te and has a uniform amorphous phase during recording.
At the time of erasure, the stoichiometric composition or its near AgSbT
The optical information recording medium according to claim 1, wherein the optical information recording medium has a structure in which an e ₂ crystal phase and an amorphous phase composed of at least In and Sb are mixed. 4. The size of a region of AgSbTe ₂ facing the same direction in the recording layer in the initialized or erased state is 2000Å to 10000Å.
The optical information recording medium described. 5. The composition and chemical structure at the time of erasing are mainly represented by However, 4. The optical information recording according to claim 1, wherein 0.4 ≦ X ≦ 0.55 and 0.5 ≦ Z ≦ 2.5 −0.15 <δ <0.1. Medium. 6. A recording layer, a protective layer, and a reflection / heat dissipation layer are provided on a substrate, and the protection layer between the recording layer and the reflection / heat dissipation layer is AlN. The optical information recording medium described in 1. 7. A method of manufacturing a rewritable optical recording medium in which information is recorded, erased, and reproduced by irradiating a laser beam, a recording layer is formed by a sputtering method using a target mainly composed of AgInTe ₂ and Sb. A method for manufacturing an optical information recording medium, comprising: 8. The method for manufacturing an optical information recording medium according to claim 7, wherein after the film formation, the initialization is first performed by the Ar laser and then the initialization is performed by the semiconductor laser.