JPH05345478A - Optical data recording medium and production thereof - Google Patents

Abstract

PURPOSE:To provide a phase change type data recording medium enhanced in an erasure ratio and capable of repeat recording and erasure by low power. CONSTITUTION:In a rewritable optical data recording medium performing the recording, erasure and reproduction of data by the irradiation with laser beam, a recording layer contains a quaternary phase change type recording material containing Ag, In, Sb and Te as a main component and an AgSbTe2 fine crystal phase composed of a stoichiometric compsn. or near to said compsn. is present at the time of non-recording and erasure.

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, particularly a phase change type information recording medium, in which the recording layer material undergoes a phase change by irradiation with a light beam to record and reproduce information. In addition, the present invention relates to a rewritable information recording medium and 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 crystalline-amorphous phase or crystalline-crystalline phase. Recording media are well known. In particular, it is possible to perform overwriting with a single beam, which is difficult for a magneto-optical memory, and the optical system on the drive side is simpler. 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-based alloy materials such as -Te and Se-As. Further, for the purpose of improving stability and high-speed crystallization, Au is added to Ge-Te system (JP-A-61-21969).
2), Sn and Au (JP-A-61-270190), P
Ge-T for the purpose of proposing a material to which d (Japanese Unexamined Patent Publication No. 62-19490) is added and improving the repetitive performance of recording / erasing.
A material in which the composition ratio of e-Se-Sb and Ge-Te-Sb is specified (JP-A-62-73438, JP-A-63-2284).
33) is also 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 extension of 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. Under these circumstances, it has been desired to develop a recording material which has a high erasing ratio and is suitable for highly sensitive recording and erasing.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems, and to provide an information recording medium having a high erasing ratio and capable of repeating recording-erasing with low power, and a manufacturing method thereof. It is a thing.

[0005]

Therefore, as a result of intensive studies for improvement, the present inventors have found a recording material and a manufacturing method thereof which meet the above-mentioned object. That is, the present invention provides (1) a rewritable optical information recording medium for recording, erasing and reproducing information by irradiating a laser beam, wherein the recording layer is Ag, I
An optical information recording medium containing a quaternary phase-change recording material containing n, Sb, and Te as a main component, and having an AgSbTe ₂ microcrystalline phase present at or near the stoichiometric composition at the time of unrecording and erasing, (2 ) In an information recording medium in which recording and erasing are performed by utilizing a transition between a stable state and a metastable state of the recording layer, the composition and chemical structure of the recording layer provided on the substrate in the stable state are mainly stoichiometric. An optical information recording medium having a composition or a mixed phase of an AgSbTe ₂ phase and a phase composed of In and Sb, which is similar to (3) the stable state of the recording layer when the information is not recorded and the stable state of the recording layer when the information is recorded. The optical recording medium according to (2), which has a stable state.
(4) In the stable state of the recording layer, AgSbTe _{2 at} or near the stoichiometric composition is in the crystalline state, (2) The optical recording medium described in (2), InSb _Z in the crystalline state is observed in the stable state of the recording layer. The optical recording medium according to (2), (6) the optical recording medium according to (4), wherein the stoichiometric composition according to claim 4 or the crystallite diameter of AgSbTe ₂ close to it is 1000 Å or less, (7) recording In an information recording medium in which recording and erasing are performed by utilizing a transition between a stable state and a metastable state of the layer, the composition and the chemical structure of the recording layer provided on the substrate in the stable state are mainly (AgSbTe _{2 + δ / △} ) _X (InSb _Z ) _1-X

[0006]

[Equation 2]

0.4 ≦ x ≦ 0.55 0.5 ≦ Z ≦ 2.5 −0.15 <δ <0.1 (8) Stable state of recording layer when no information is recorded However, in the optical recording medium according to (7), which has a stable state and a metastable state of the recording layer at the time of information recording, (9) in the stable state of the recording layer, the stoichiometric composition or AgSbTe ₂ close thereto is a crystalline state. (7) The optical recording medium, (10) In the stable state of the recording layer, crystalline InSb _Z is not observed, (7) The optical recording medium,
(11) Stoichiometric composition or AgSbTe close to it
The optical recording medium according to (9), wherein the crystallite diameter of ₂ is 1000 Å or less, and (12) the optical information recording medium having a recording layer, a protective layer, and a reflection heat dissipation layer on a substrate, wherein the recording layer is Ag, I.
n, Sb, and Te, and a uniform amorphous phase is formed by rapid cooling after melting. By heating and cooling the amorphous phase below the melting point, at least In, Sb
An optical information recording medium having a structure in which AgSbTe ₂ crystals having a stoichiometric composition or close to it are dispersed with a crystallite diameter of 50Å to 500Å in an amorphous matrix composed of
(13) In an optical information recording medium having a recording layer, a protective layer, and a reflection / heat dissipation layer on a substrate, the recording layer is Ag, In, Sb,
It is made of Te and becomes a uniform amorphous phase by rapid cooling after melting. By heating and cooling the amorphous phase to a temperature equal to or lower than the melting point, a stoichiometric composition at or near A in an amorphous mother phase composed of at least In and Sb is obtained.
gSbTe ₂ crystals are dispersed with a crystallite size of 50Å to 500Å, and the crystal orientation of each crystal grain is 2000Å to 10000.
Optical information recording mediums that are equal in the area of Å, (14)
In an optical information recording medium having a recording layer, a protective layer, and a reflection heat dissipation layer on a substrate, the recording layer is made of Ag, In, Sb, Te, and is melted and rapidly cooled to form a uniform amorphous phase. By heating and gradual cooling to the following, AgSbT at or near the stoichiometric composition in the amorphous matrix composed of at least In and Sb
An optical information recording medium having a structure in which e ₂ crystals are dispersed with a crystallite diameter of 50Å to 500Å, and the protective layer is AlN, (15) a light having a recording layer, a protective layer and a reflection heat dissipation layer on a substrate. In the information recording medium, the recording layer has Ag, In,
It consists of Sb and Te, and becomes a uniform amorphous phase by rapid cooling after melting. By heating and cooling the amorphous phase below the melting point, at least a stoichiometric composition or close to it in the amorphous mother phase composed of In and Sb. AgSbTe ₂ crystals are dispersed with a crystallite size of 50Å to 500Å, and the crystal orientation of each crystal grain is 2000Å to 10
The area is equal to 000Å, and the protective layer is Al
The optical information recording medium of N, (16) the optical recording medium according to (7), in which the stoichiometric composition in the crystalline state or AgSbTe ₂ close thereto is not observed in the metastable state of the recording layer, (17) the quasi-stable state of the recording layer The optical recording medium according to (2), in which crystalline InSb _Z is not observed in the stable state.
(18) In the stable state and the metastable state of the recording layer, A
(7) The optical recording medium according to (7), in which crystals consisting of individual elements of g, Sb, Te, and In are not observed, (19) AgIn in a crystalline state in a stable state and a metastable state of the recording layer.
The optical recording medium according to (7), in which Te ₂ is not observed, (2
0) The recording layer is formed using AgInTe ₂ and Sb as raw materials, and the recording layer in the stable state according to (4) or (5) is obtained by initializing with a laser beam, heat, etc. (2) Description (21) The method for manufacturing an optical recording medium according to (1) above.
In 5), the present invention relates to the method for producing an optical recording medium according to (20), which uses a target mainly composed of AgInTe ₂ and Sb to form a film by a sputtering method.

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, but in addition to this, X-ray microanalysis, Rutherford backscattering,
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 used when a spot-like or Debye ring-like pattern is observed in the electron beam diffraction image, and the amorphous state is obtained when a ring-like 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.

The present invention will be described in more detail. The recording layer according to the present invention contains at least Ag and I as constituent elements.
It contains n, Sb, and Te. The recording layer is often amorphous at the time of film formation, but is initialized by heat treatment after medium formation.

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. AgSbTe ₂ (1 in the figure) and amorphous InSb _Z (2 in the figure) that exist in a stoichiometric composition of the crystalline phase or close to it and exist in a mixed phase state, and AgSbTe ₂ having a stoichiometric composition or close to it have a crystallite size of 1000 Å or less. It is in a microcrystalline state.

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 laser light to become an amorphous phase (transition from recording to metastable state), a uniform phase at a high speed is obtained. A change occurs, and an amorphous phase with little physical or chemical variation is formed. The fine structure of this amorphous phase is difficult to analyze and the details are unknown. For example, the stoichiometric composition of the amorphous phase or AgSbTe close to it
It is considered that a combination of ₂ and the amorphous phase InSb _Z , 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 also occurs uniformly, and therefore the erase ratio is very high. It will be expensive. Also, 1000Å
In the case of fine particles of a certain size, the melting point is lowered due to the size effect, so that the phase transition can occur at a relatively low temperature. That is, the recording sensitivity of the recording medium is improved. In other words, if the crystallite size is 1000 Å or more, the recording sensitivity is deteriorated and the erasing ratio is lowered. A more preferable crystallite size is in the range of 50Å to 500Å. If it is less than 50Å, the reflectance is lowered and a sufficient C / N cannot be obtained. On the other hand, when the crystallite size exceeds 500 Å, the erasing ratio gradually decreases. The cause of such a high erasing ratio is that the amorphous I around amorphous AgSbTe ₂ having a stoichiometric composition or a composition close to the stoichiometric composition.
It is considered that the surrounding of nSb _Z plays a role of preventing the crystallites of AgSbTe ₂ close to or near the stoichiometric composition from coming into contact with _each other to form coarse crystal grains. Further, it is desirable that a region in which adjacent AgSbTe ₂ crystal grains in the amorphous matrix have a stoichiometric composition or are close to the stoichiometric composition and have the same orientation in the range of 1000Å to 10000Å. In this range, sufficient C / N, erasing ratio, and repeatability can be obtained. If this region is 1000 Å or less or 10000 Å or more, the repetitive characteristics deteriorate.

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
It is considered that InTe ₂ and Sb are in an amorphous phase. 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 laser light of appropriate power, heat, or the like will prevent AgSbTe ₂ and amorphous InSb _{Z from} having a stoichiometric composition of microcrystals or close to it.
It is possible to create a uniform mixed phase of.

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 equation 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 may be formed by various vapor phase growth methods such as vacuum deposition, sputtering, plasma CVD,
It can be formed by a photo CVD method, an ion plating method, an electron beam evaporation method or the like. Besides the vapor phase growth method, a wet process such as a sol-gel method can also be applied. The thickness of the recording layer is 100 to 10000Å, preferably 200 to 3
It is good to set it to 000Å. 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 hard 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 on which an e ₂ chip is mounted, one embedded, a mixture of AgInTe ₂ and Sb, a laminated body, a sintered body thereof, and the like, 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. 2 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). Although it is not always necessary to provide the heat-resistant protective layer on both sides of the recording layer, 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 resins include 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 substrate may have a disk shape, a card shape, or a sheet shape.

Materials for the heat-resistant protective layer include SiO, 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 and 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 such as N, BN, SiC, C having a thermal conductivity of 1 W / cm · K or more is suitable. It is extremely difficult to measure the thermal conductivity of a thin film of the order of μm or less, especially 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.multidot.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, but may also be a mixture with each other. In addition, impurities may be included if 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 can be multi-layered. Such a heat resistant protective layer may be 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 heat-resistant protective layer is 200 to 5000 Å, preferably 500.
~ 3000 Å is recommended. When it becomes thinner than 200Å, 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 can be formed by various vapor deposition methods such as vacuum deposition method, sputtering method, plasma CVD method, photo CVD method, ion plating method and electron beam evaporation method.

As the electromagnetic wave used for recording, reproducing and erasing, various kinds such as laser light, electron beam, X-ray, ultraviolet ray, visible ray, infrared ray and microwave can be adopted.
When mounted in a drive, a small and compact laser diode is the best choice.

[0024]

EXAMPLES The present invention will be specifically described below with reference to examples. However, these examples do not limit the present invention.

Example 1 On a polycarbonate disc substrate with a 3.5-inch groove, Si ₃ N ₄ was added as a lower heat-resistant protective layer at 2000Å, A
The g-In-Sb-Te recording layer is 1000 Å, AlN is 1500 Å as the upper heat-resistant protective layer, and Al is the reflection and heat dissipation layer.
500 Å was sequentially laminated and set by the rf magnetron sputtering method. At that time, as a sputtering target, an AgInTe ₂ target with an Sb chip mounted thereon was used. The composition of the recording layer is Ag _0.122 In _0.162 Sb
_0.470 Te _{0.246 Fixed} . The disk characteristics were evaluated by changing the structure of the recording layer by using a semiconductor laser, an Ar laser, or a flash lamp as the initialization method. At this time, the AgSbTe ₂ crystallite diameter is about 200Å to 300.
It was Å. The NA of the optical system is 0.5, the wavelength is 830 nm,
Recording at a linear velocity of 7 m / s, a frequency of 4 MHz and a 50% duty ratio, and measuring the C / N and erasing ratio of a signal of a frequency of 4 MHz when overwriting was performed at a frequency of 5 MHz and a 50% duty ratio, and used as a recording medium. Was judged. The results are shown in Table 1.

[0026]

[Table 1]

Example 2 In the same manner as in Example 1, an initial state of the recording layer was set to a stoichiometric composition or a mixed phase state of AgSbTe ₂ and amorphous (InSb) _Z close to it, and an upper protective layer was formed in the same manner as in Example 1. A disk was prepared by using AlN and by replacing AlN with Si ₃ N ₄ and SiO ₂ for comparison.

The thermal conductivity of each material is AlN: 2.6 W / c
mK, Si ₃ N ₄ : 0.8 W / cmK, SiO ₂ : 0.6
It was W / cmK. Table 2 shows the initial characteristics of C / N and erase ratio, and the repeating characteristics.

[0029]

[Table 2]

Example 3 On a polycarbonate disc substrate with a 3.5-inch groove, ZnS.SiO ₂ (20 m
ol% mixed) 2000 Å, recording layer 1000 Å, AlN 1500 Å as the upper heat-resistant protective layer, and Ag 700 Å as the reflection and 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 3 shows the compositions x, z and δ of the recording layer measured by fluorescent X-ray. All the recording layers at the time of making the disk were in the amorphous phase. The recording layer was sufficiently crystallized with a semiconductor laser beam having a wavelength of 830 nm to bring it into an initialized state (stable state). C / of a signal with a frequency of 0.72 MHz when recorded at a linear velocity of 1.3 m / s, a frequency of 0.72 MHz and a 50% duty ratio and overwritten at a frequency of 0.2 MHz and a 50% duty ratio
The N and erase ratios were measured, and the recording medium was judged.
The results are shown in Table 3. In the table, ● indicates C / N ≧ 50 dB, erasing ratio ≧ −30 dB, ◯ indicates C / N ≧ 40 dB, erasing ratio ≧ −
25 dB, Δ is C / N ≧ 30 dB, erase ratio ≧ −20 d
B and x indicate that C / N <30 dB and erase ratio <-20 dB. FIG. 3 shows the relationship between the compositions x and z and the disk characteristics, and FIG. 4 shows the relationship between δ and the disk characteristics. 0.4 ≦ x ≦ 0.55, 0.5 ≦ z ≦ 2.5, −
It can be seen that good disk characteristics are exhibited in the range of 0.15 <δ <0.1. Further, as shown in Table 3, the recording sensitivity is also very high.

[0031]

[Table 3]

Example 4 On a polycarbonate disk substrate with a 3.5-inch groove, Si ₃ N ₄ was added as 2000 Å, A as a lower heat-resistant protective layer.
The g-In-Sb-Te recording layer is 1000Å, Si ₃ N ₄ is 1000Å as the upper heat-resistant protective layer, and A is the reflection / heat dissipation layer.
500 Å of 1 was sequentially laminated and set by the rf magnetron sputtering method. The composition of the recording layer _{(AgSbTe 2 + δ / △)} X (InSb Z) 1-X , however,

[0033]

[Equation 3]

X = 0.5 Z = 1.5 δ = 0 Initialization was performed by LD. The crystallite diameter can be changed by changing the initialization power. The crystallite size can be calculated from the peak half width of X-ray diffraction data by Scherrer.
It was calculated using the formula. Further, in these recordings, the region where the crystal orientations were uniform was about 2000 Å. The crystal orientation was evaluated by TEM observation.

Recorded at a wavelength of 830 nm, a linear velocity of 7 m / s, a frequency of 4 MHz and a 50% duty ratio, and a frequency of 5 M.
The C / N and the erasing ratio of a signal having a frequency of 4 MHz were measured when overwriting was performed at Hz and a 50% duty ratio, and the recording medium was judged. FIG. 5 shows the crystallite diameter dependence of C / N (solid line) and erase ratio (dotted line). It can be seen that when the crystallite diameter is 50 Å or less, C / N decreases, and when the crystallite diameter is 500 Å or more, the erasing ratio gradually decreases.

Example 5 A disk was prepared in the same manner as in Example 4. Initialization was performed with a semiconductor laser. Linear velocity from 1m / s to 20
It was changed in the range of m / s. By doing this, the size of the region where the crystallographic orientations are aligned is from 500Å to 2000.
I was able to change it in the range of 0Å. Crystallite size is about 2
It is less than 00Å.

FIG. 6 shows the region size dependence of the repeating characteristics. The repeatability is evaluated by the number of times that the reduction of the erasing ratio becomes 10 dB. As you can see from Figure 6, 1000Å
Repetition characteristics deteriorated below or above 10,000 Å.

Example 6 A disk was prepared in the same manner as in Example 4. However, AlN was used as the protective layer. FIG. 7 shows the relationship between the crystallite diameter and the erasing ratio. As compared with the case where the protective layer is Si ₃ N ₄ , the erasing ratio is improved at 500 Å or less.

Example 7 A disk was prepared in the same manner as in Example 5. However, AlN was used as the protective layer. FIG. 8 shows the relationship between the size of the region with uniform crystal orientation and the repeating characteristics. Si protective layer
_The repeatability is improved compared to the case of ₃ N ₄ .

The recording portion of the recording layer of Examples 4, 5, 6, and 7,
When electron diffraction was performed on each of the erased parts,
A halo pattern peculiar to amorphous was observed in the recording portion. On the other hand, in the erased portion, clear diffraction spots were seen in addition to the halo pattern. These diffraction spots coincided with the interplanar spacing of AgSbTe ₂ , and it was confirmed that during the erasing, AgSbTe ₂ having a stoichiometric composition or a composition close to it was fine crystals.

[0041]

As described above, the optical recording medium of the present invention has remarkably excellent erase ratio and recording sensitivity.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view of a stable state of a recording layer of an optical recording medium of the present invention.

FIG. 2 is an explanatory diagram of a layer structure of the optical recording medium of the present invention.

FIG. 3 is an explanatory diagram of the relationship between the results of Example 3 and x and z.

FIG. 4 is an explanatory diagram of the relationship between the result of Example 3 and δ.

FIG. 5 is a diagram showing the results of Example 4 and the dependence of C / N (solid line) and erase ratio (dotted line) on the crystallite diameter.

FIG. 6 is a diagram showing the relationship between the results of Example 5, the repeating characteristics, and the size of the region where the crystal orientations are aligned.

FIG. 7 is a graph showing the relationship between the results of Example 6, the crystallite size, and the erasing ratio.

FIG. 8 is a graph showing the relationship between the results of Example 7, the repeating characteristics, and the size of regions having uniform crystal orientations.

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

Claims (21)

[Claims] 1. A rewritable optical information recording medium for recording, erasing and reproducing information by irradiating a laser beam, wherein a recording layer is a quaternary phase change type recording material containing Ag, In, Sb and Te. AgSbTe ₂ which is contained as the main component and has a stoichiometric composition at or near unrecorded and erased.
An optical information recording medium having a microcrystalline phase. 2. An information recording medium in which recording and erasing are performed by utilizing a transition between a stable state and a metastable state of a recording layer,
The optical information recording characterized in that the composition and chemical structure of the recording layer provided on the substrate in a stable state are mainly in a stoichiometric composition or a mixed phase state of AgSbTe ₂ phase and a phase composed of In and Sb. Medium. 3. The stable state of the recording layer when no information is recorded,
The optical recording medium according to claim 2, wherein a stable state and a metastable state of the recording layer exist during information recording. 4. The optical recording medium according to claim 2, wherein in the stable state of the recording layer, AgSbTe _{2 which} is at or near the stoichiometric composition is in a crystalline state. 5. The optical recording medium according to claim 2, wherein InSb _Z in a crystalline state is not observed in the stable state of the recording layer. 6. The optical recording medium according to claim 4, wherein the stoichiometric composition according to claim 4 or the crystallite diameter of AgSbTe ₂ close thereto is 1000 Å or less. 7. An information recording medium for recording and erasing by utilizing the transition between a stable state and a metastable state of a recording layer,
Composition and chemical structure in the stable state of the recording layer provided on the substrate mainly _{(AgSbTe 2 + δ / △)} X (InSb Z) 1-X , however, Equation 1] 0.4 ≦ x ≦ 0.55 0.5 ≦ Z ≦ 2.5 −0.15 <δ <0.1 An optical recording medium characterized by the following. 8. The stable state of the recording layer when no information is recorded,
8. The optical recording medium according to claim 7, wherein a stable state and a metastable state of the recording layer exist during information recording. 9. The optical recording medium according to claim 7, wherein in the stable state of the recording layer, AgSbTe _{2 which} is at or near the stoichiometric composition is in a crystalline state. 10. The crystalline InSb _Z is not observed in the stable state of the recording layer.
The optical recording medium described. 11. A stoichiometric composition or an Ag close thereto.
The optical recording medium according to claim 9, wherein the crystallite diameter of SbTe ₂ is 1000 Å or less. 12. An optical information recording medium having a recording layer, a protective layer and a reflection / heat dissipation layer on a substrate, wherein the recording layer is Ag, I.
n, Sb, and Te, and a uniform amorphous phase is formed by rapid cooling after melting. By heating and cooling the amorphous phase below the melting point, at least In, Sb
An optical information recording medium having a structure in which an AgSbTe ₂ crystal having a stoichiometric composition or close to it is dispersed with a crystallite diameter of 50 Å to 500 Å in an amorphous matrix composed of. 13. An optical information recording medium having a recording layer, a protective layer, and a reflection and heat dissipation layer on a substrate, wherein the recording layer is Ag, I.
n, Sb, and Te, and a uniform amorphous phase is formed by rapid cooling after melting. By heating and cooling the amorphous phase below the melting point, at least In, Sb
AgSbTe ₂ crystals with a stoichiometric composition or close to it are dispersed in the amorphous matrix consisting of a crystallite diameter of 50Å to 500Å, and the crystallographic orientation of each crystal grain is the same in the range of 2000Å to 10000Å. Optical recording medium. 14. An optical information recording medium having a recording layer, a protective layer and a reflection / heat dissipation layer on a substrate, wherein the recording layer is Ag, I.
n, Sb, and Te, and a uniform amorphous phase is formed by rapid cooling after melting. By heating and cooling the amorphous phase below the melting point, at least In, Sb
Has a structure in which AgSbTe ₂ crystals having a stoichiometric composition or close to the stoichiometric composition are dispersed with a crystallite diameter of 50 Å to 500 Å, and the protective layer is made of Al.
An optical information recording medium characterized by being N. 15. An optical information recording medium having a recording layer, a protective layer, and a reflection / heat dissipation layer on a substrate, wherein the recording layer is Ag, I.
n, Sb, and Te, and a uniform amorphous phase is formed by rapid cooling after melting. By heating and cooling the amorphous phase below the melting point, at least In, Sb
AgSbTe ₂ crystals having a stoichiometric composition or close to it are dispersed in the amorphous matrix consisting of a crystallite diameter of 50Å to 500Å, and the crystallographic orientation of each crystal grain is equal in the region of 2000Å to 10000Å. Is an AlN, an optical information recording medium characterized in that. 16. The optical recording medium according to claim 7, wherein in the metastable state of the recording layer, AgSbTe ₂ having a stoichiometric composition in the crystalline state or close to the stoichiometric composition is not observed. 17. The optical recording medium according to claim 7, wherein InSb _Z in a crystalline state is not observed in the metastable state of the recording layer. 18. The optical recording medium according to claim 7, wherein crystals consisting of a simple substance of each element of Ag, Sb, Te and In are not observed in the stable state and the metastable state of the recording layer. 19. The optical recording medium according to claim 7, wherein AgInTe ₂ in a crystalline state is not observed in the stable state and the metastable state of the recording layer. 20. A stable recording layer according to claim 4 or 5 is obtained by forming a recording layer using AgInTe ₂ and Sb as raw materials and performing initialization with laser light, heat or the like. 3. The method for manufacturing an optical recording medium according to claim 2, which is characterized in that. 21. In Claim 15, mainly AgInT
21. The method for producing an optical recording medium according to claim 20, wherein the film is formed by a sputtering method using a target composed of e ₂ and Sb.