JPH0963119A - Optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a recording medium excellent in erasing characteristics over a wide linear velocity region and jitter characteristics after overwriting and having a long service life by forming a reflecting layer with an alloy of one or more kinds of metals with Si or/and Ge. SOLUTION: This recording medium has at least a 1st dielectric layer, a recording layer, a 2nd dielectric layer and a reflecting layer on the substrate. Information can be recorded, reproduced and erased by irradiating the recording layer with light and information is recorded and erased by a phase change between amorphous and crystal phases. The reflecting layer is made preferably of an alloy of one or more kinds of metals each having a higher absolute value of the heat of formation of oxide than Si or/and Ge with Si or/and Ge because optical deterioration is suppressed and shelf stability is improved. The alloy is especially preferably represented by the formula Mx X1-x [where M is Zr, Ti or Hf, X is Si or/and Ge and (x) is 0.1-0.8 and shows the molar ratio between the elements].

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to
The present invention relates to an optical information recording medium capable of recording, erasing, and reproducing information.

In particular, the present invention relates to a rewritable phase change type optical recording medium such as an optical disc having a function of erasing and rewriting recorded information and capable of recording information signals at high speed and high density.

[0003]

2. Description of the Related Art The conventional techniques for rewritable phase change type optical recording media are as follows.

These optical recording media have a recording layer containing tellurium as a main component, and at the time of recording, a focused laser light pulse is irradiated to the recording layer in a crystalline state for a short time to partially cover the recording layer. To melt. The melted part is quenched by heat diffusion,
The recording marks are solidified to form amorphous recording marks.
The light reflectance of this recording mark is lower than that of the crystalline state and can be reproduced optically as a recording signal.

Further, at the time of erasing, the recording mark portion is irradiated with a laser beam and heated to a temperature not lower than the melting point of the recording layer and not lower than the crystallization temperature to crystallize the recording mark in an amorphous state and to restore the original unrecorded state. Return to the state.

As a material for the recording layer of these rewritable phase change optical recording media, alloys such as Ge ₂ Sb ₂ Te ₅ (N.Ya
mada et al, Proc. Int. Symp.on Optical Memory 1987 p
61-66) is known.

Optical recording media using these Te alloys as recording layers have a high crystallization rate, and high speed overwriting with a circular single beam is possible only by modulating the irradiation power. In an optical recording medium using these recording layers, a dielectric layer having heat resistance and translucency is usually provided on both surfaces of the recording layer to prevent deformation and opening of the recording layer during recording. Further, a metal reflective layer such as a light-reflective metal such as Al is provided on the dielectric layer on the side opposite to the light beam incident direction to improve the signal contrast at the time of reproduction by an optical interference effect and to cool the recording layer. Is known to facilitate the formation of recording marks in an amorphous state and improve erasing characteristics and repetitive characteristics.

In particular, in the "quick cooling structure" in which the dielectric layer between the recording layer and the recording layer and the reflecting layer is thinned to about 20 nm, respectively, the "gradual cooling structure" is formed in which the dielectric layer is thickened to about 200 nm.
It is known that the characteristics of recording are less changed by repeated rewriting, and the erasing power margin is wider than that of T.Ohota et al, Japanese Journal.
of Applied Physics, Vol28 (1989) Suppl. 28-3 pp123-12
8).

The problems in the above-described conventional rewritable phase change type optical recording medium are as follows.

In the conventional disk structure, since the difference in reflectance between the recorded amorphous recording mark and the crystalline state is large, the amount of light absorbed in the amorphous state of the recording film is higher than that in the crystalline state. Also, the crystal part needs to absorb energy corresponding to latent heat of fusion. Therefore, there is a difference in the temperature rise state during recording depending on whether the portion before overwrite recording is crystalline or amorphous mark, and as a result, the shape and formation position of the newly overwritten recording mark are overwritten. It was modulated by the previous signal, which was a cause of limiting the erasing rate and the jitter characteristics after overwriting. In particular, if high density technology is applied such as using a short wavelength laser to make the light spot smaller, or adopting mark length recording instead of the conventional pit position recording, the above problems become serious. Come on.

The following techniques are known as means for solving the problem that the light absorption amount in the amorphous state becomes higher than that in the crystalline state. That is, JP-A-5-15936
As in Japanese Patent Laid-Open No. 0-0,096, Ti having a thickness of about 50 nm is formed as a light absorbing layer after the second dielectric layer having a thickness of 220 nm,
Further, there is a technique of forming a relatively thin Al layer having a thickness of about 50 nm as a heat dissipation layer in order to reduce a thermal load on the light absorption layer due to a temperature rise due to light absorption.

[0012]

However, in the above-described structure, the second dielectric layer has a large thickness of 220 nm, which is a so-called gradual cooling structure, so that the degree of cooling of the recording layer during recording is low. Therefore, there are problems that the deterioration of recording characteristics due to repetitive rewriting is large and that a sufficient carrier-to-noise ratio (C / N) cannot be obtained in the low linear velocity region.

An object of the present invention is to improve the erasing property and the jitter property after overwriting of an optical recording medium having a conventional rapid cooling structure, which exhibits excellent properties such as the rewriting repetitive property described above. An object of the present invention is to provide an optical recording medium having excellent erasing characteristics and jitter characteristics after overwriting over a wide range of linear velocities from a high speed range to a high linear speed range.

Another object of the present invention is to provide an optical recording medium having excellent storage stability and long life.

[0015]

According to the present invention, information is recorded by irradiating a recording layer formed on a substrate with light.
It is erasable and reproducible, and recording and erasing of information is performed by a phase change between an amorphous phase and a crystalline phase, and at least the first
An optical recording medium having a dielectric layer, a recording layer, a second dielectric layer, and a reflective layer, the reflective layer containing at least one metal, and S.
The present invention relates to an optical recording medium characterized by being formed of an alloy of i or / and Ge.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The reflective layer of the present invention is made of an alloy material having a low reflectance and a light absorptivity at a wavelength λ of light used for recording and reproduction. This light absorption effect reduces the amount of light absorption of the amorphous recording layer. By using such a material having a high light absorption property, the light absorption amount of the recording layer in the crystalline state can be made larger than that in the amorphous state. As a result, the difference in temperature rise at the time of recording becomes small, and the disorder of the shape of the recording mark, the deviation of the forming position, etc. can be reduced, and the erasing characteristic and the jitter characteristic after overwriting can be improved. Further, since heat is easily retained by absorbing light in the reflective layer, the erasing rate and recording sensitivity at high linear velocity can be improved.

Further, in the reflection layer of the present invention, the absolute value of the heat of formation of the oxide is larger than that of Si and / or Ge.
An alloy of at least one kind of metal and Si or / and Ge is preferable because optical deterioration is suppressed and storage stability becomes high.

In particular, an alloy represented by the following composition formula is preferable because it has high storage stability and excellent recording characteristics such as recording sensitivity, erasing rate, and jitter after overwriting.

Composition formula M _x X _1-x 0.1 ≦ x ≦ 0.8 (where M is Be, Al, Sc, Ti, Cr, M
n, Fe, Co, Ni, Cu, Y, Zr, Nb, Ru,
Rh, Pd, Ag, Hf, Re, Os, Ir, Pt, A
represents at least one metal selected from u, and X
Represents at least one element selected from Si and Ge, and x represents the molar ratio of the elements. ) The range of the molar ratio x is preferably 0.1 or more and 0.8 or less. When the molar ratio x is larger than 0.8, the real part of the refractive index of the present invention becomes small, the difference in the light absorption amount between the crystalline state and the amorphous state of the recording layer becomes small, and the jitter value after overwriting increases. To do. When the molar ratio x is smaller than 0.1, the imaginary part of the refractive index is small and the light absorption amount of the reflective layer is small.

Si or / and G of the reflective layer material of the present invention
The metals in the e alloy are Be, Al, Sc, Ti, Cr, M.
n, Fe, Co, Ni, Cu, Y, Zr, Nb, Ru,
Rh, Pd, Ag, Hf, Re, Os, Ir, Pt, A
u is preferred. Among them, Zr, Ti, and Hf are more preferable because they are excellent in storage stability.

The crystallographic structure of the inventive reflective layer material is preferably substantially amorphous. If it has a crystalline structure, phase segregation may occur and the film may become uneven, or the temperature may rise during mark recording, causing a structural phase transition, which may cause a decrease in overwrite repeatability such as film peeling. .

The real part of the refractive index of the material of the present invention is 3.0 or more and 5.0 or less.
It is preferable because it has excellent recording characteristics such as / N.
When it is 3.0 or less, the difference in the amount of light absorption between the crystal and the amorphous of the recording layer becomes small, and the jitter after overwriting deteriorates. Further, when it is 5.0 or more, the difference in reflectance between the crystal and the amorphous of the recording layer becomes small, and the C / N becomes small.

Since the imaginary part of the refractive index of the material of the present invention is 2.5 or more and 4.0 or less, recording characteristics such as recording sensitivity, jitter after overwriting, and C / N laser power margin are excellent. preferable. When it is 2.5 or less, the light absorption amount of the reflective layer becomes small, the sensitivity is lowered in the high linear velocity region, and the jitter after overwriting becomes large. Also 4.
When it is 0 or more, the degree of cooling becomes small, recrystallization easily occurs at the time of mark recording at a low linear velocity, C / N is lowered at high laser power, and the laser power margin of C / N becomes small.

Particularly, the range of the real part of the refractive index is 3.5 or more and 5.0 or less, and that of the imaginary part is 2.7 or more and 3.5 or less. It is more preferable because a large difference in absorption amount can be secured and it is effective in reducing jitter after overwriting.

The optical recording medium having the reflective layer of the present invention has a so-called quenching structure in which the thickness of the recording layer is 5 nm or more and 40 nm or less and the thickness of the second dielectric layer is 3 nm or more and 30 nm or less. Are preferable because of excellent recording characteristics such as repeated durability, jitter after overwriting, and erasing rate. When the film thickness of the recording layer is thinner than 5 nm or the film thickness of the second dielectric layer is thinner than 3 nm, defects such as cracks occur and the repeated durability is deteriorated. If the thickness of the recording layer is thicker than 40 nm, the crystal in the recording layer-
The difference in light absorption amount between amorphous materials becomes small, which causes an increase in the jitter value after overwriting. The thickness of the second dielectric layer is 3
If it is larger than 0 nm, the degree of cooling becomes small, so that the erasing rate at a low linear velocity decreases.

In particular, in order to improve the jitter characteristic after overwriting, in order to further increase the light absorption difference,
More preferably, the film thickness of the recording layer is 5 nm or more and 15 nm or less, and the film thickness of the second dielectric layer is 3 nm or more and 15 nm or less.

On the reflective layer of the present invention, a protective layer such as SiO ₂ , ZnS, ZnS-SiO ₂ or the like, a resin layer such as an ultraviolet curable resin, or another substrate is attached to the reflective layer within a range that does not impair the effects of the present invention. You may provide the adhesive layer of.

The first and second dielectric layers of the present invention have the effect of protecting the substrate and the recording layer from heat, such as preventing the substrate and the recording layer from being deformed by heat during recording and deteriorating the recording characteristics. The optical interference effect has the effect of improving the signal contrast during reproduction.

For this dielectric layer, ZnS, Si
There are inorganic thin films such as O ₂ , silicon nitride, and aluminum oxide. In particular, a thin film of ZnS, Si, Ge, Al, Ti,
A metal oxide thin film such as Zr and Ta, a nitride thin film such as Si and Al, a carbide thin film such as Ti, Zr and Hf, and a film of a mixture of these compounds are preferable because of high heat resistance. Further, a mixture of carbon and a fluoride such as MgF ₂ is also preferable because the residual stress of the film is small. Especially mixed film of ZnS and SiO ₂ or a mixed film of ZnS and SiO ₂ and carbon are recorded, even by the repetition of erasing, preferably since the recording sensitivity, C / N, hardly occurs deterioration, such as erasure ratio, especially ZnS And Si
A mixed film of O ₂ and carbon is preferable.

The thickness of the first dielectric layer is approximately 10-50.
It is 0 nm. The thickness is preferably 50 to 400 nm because it is difficult to peel from the substrate or the recording layer and defects such as cracks are hard to occur. In particular, the thickness of the first dielectric layer is preferably set to satisfy the following equation in order to make the light absorption amount of the recording layer in the crystalline state as large as possible in comparison with that in the amorphous state.

(Formula) Nλ / 4−0.2λ ≦ nd1 ≦ Nλ / 4 + 0.2λ where N is an integer selected from 1 and 3, and λ
Is the wavelength used for recording, n is the refractive index (real part) of the first dielectric layer, and d1 is the thickness of the first dielectric layer.

The recording layer of the present invention is not particularly limited, but an In-Se alloy, Ge-Sb-Te alloy, In-Sb-Te alloy, Pd-Ge-Sb-Te alloy, Nb-Ge is used. -Sb-Te alloy, Pt-Ge-Sb-
Te alloy, Co-Ge-Sb-Te alloy, Ag-In-
Examples thereof include Sb-Te alloy and Nb-Pd-Ge-Sb-Te alloy.

Since the recording can be rewritten many times, the Ge-Sb-Te alloy, Pd-Ge-Sb-Te alloy, Nb-Ge-Sb-Te alloy, Pt-Ge-Sb-
Te alloy and Nb-Pd-Ge-Sb-Te alloy are preferable.

In particular, Pd-Ge-Sb-Te alloy, Nb-
Ge-Sb-Te alloy, Pt-Ge-Sb-Te alloy,
The Nb-Pd-Ge-Sb-Te alloy has a short erasing time and can record and erase many times,
It is preferable because it has excellent recording characteristics such as C / N and erasing rate.

In particular, since the recording sensitivity is high, the one-beam overwrite can be performed at a high speed, the erasing rate is large, and the erasing characteristic is good, the main part of the optical recording medium can be constructed as follows. preferable.

That is, G as a constituent element in the recording layer.
Using an alloy containing at least three elements of e, Sb, and Te,
The thickness of the first dielectric layer is d1, the refractive index (real part) of the first dielectric layer is n, an integer selected from 1 and 3 is N, the laser wavelength used for recording is λ, and the thickness of the recording layer is When dr, the thickness of the second dielectric layer is d2, and the thickness of the reflective layer is da, it is preferable to set the layer thickness so as to satisfy the following equation.

(Formula) Nλ / 4−0.2λ ≦ nd1 ≦ Nλ / 4 + 0.2λ 5 ≦ dr ≦ 40 (unit nm) 3 ≦ d2 ≦ 30 (unit nm) 10 ≦ da ≦ 300 (unit nm) In particular, The dielectric layer is a mixed film containing at least ZnS and SiO ₂ as constituent materials, and the mixing ratio of SiO ₂ is 15 to 35.
It is more preferable that the content is mol% and the composition of the recording layer is in the range represented by the following formula.

Compositional formula M _z (Sb _x Te _1-x ) _1-yz (Ge _0.5 Te _0.5 ) _y 0.35 ≦ x ≦ 0.5 0.2 ≦ y ≦ 0.5 0.0005 ≦ z ≦ 0 .01 Here, M represents at least one metal selected from palladium, niobium, platinum, silver, gold, and cobalt. Also,
x, y, z, and numbers represent the number of atoms of each element (the number of moles of each element).

As the material of the substrate of the present invention, various transparent synthetic resins, transparent glass and the like can be used. In order to avoid the influence of dust and scratches on the substrate, it is preferable to use a transparent substrate and perform recording from the substrate side with a focused light beam.As such a transparent substrate material, glass, polycarbonate, polymethylmethacrylate, Examples thereof include polyolefin resin, epoxy resin and polyimide resin.

Polycarbonate resin and amorphous polyolefin resin are particularly preferable because they have small optical birefringence, small hygroscopicity, and easy molding.

The thickness of the substrate is not particularly limited, but 0.01 mm to 5 mm is practical. 0.01m
If it is less than m, even when recording with a light beam focused from the substrate side, it is easily affected by dust, and if it is 5 mm or more,
It becomes difficult to increase the numerical aperture of the objective lens, and the spot size of the irradiation light beam becomes large, so that it becomes difficult to increase the recording density. The substrate may be flexible or rigid. The flexible substrate is used in the form of a tape, a sheet, or a card. The rigid substrate is used in the form of a card or a disk. Further, these substrates may be formed into an air sandwich structure, an air incident structure, or a close bonding structure using two substrates after forming a recording layer and the like. The light source used for recording the optical recording medium of the present invention is a laser light, a high-intensity light source such as strobe light, and in particular, the semiconductor laser light has a small light source, low power consumption, and easy modulation. It is preferable because it exists.

Recording is performed by irradiating a recording layer in a crystalline state with a laser light pulse or the like to form an amorphous recording mark. Alternatively, a recording mark in a crystalline state may be formed on a recording layer in an amorphous state. Erase by laser light irradiation,
Crystallize an amorphous recording mark, or
The recording mark in a crystalline state can be made amorphous.

Since the recording speed can be increased and the recording layer is hardly deformed, it is preferable to form amorphous recording marks during recording and crystallize during erasing.

When forming a recording mark, the light intensity is high.
The one-beam overwrite in which the light is slightly weakened at the time of erasing and rewriting is performed by irradiating the light beam once is preferable because the rewriting time is shortened.

Next, a method for manufacturing the optical recording medium of the present invention will be described.

As a method for forming the reflective layer, the recording layer and the like on the substrate, there are known known thin film forming methods in vacuum, such as a vacuum vapor deposition method, an ion plating method and a sputtering method. In particular, the sputtering method is preferable because the composition and the film thickness can be easily controlled.

The thickness of the recording layer or the like to be formed can be easily controlled by monitoring the deposition state with a well-known technique such as a crystal oscillator film thickness meter.

The recording layer and the like may be formed with the substrate fixed, moved, or rotated. Since the in-plane uniformity of the film thickness is excellent, it is preferable to rotate the substrate on its own axis, and it is more preferable to combine the revolution.

[0049] Further, in not significantly impaired range the effects of the present invention, after forming the like reflective layer, flaws, such as for prevention of deformation, ZnS, such as SiO _2, ZnS and a mixed film of SiO _2, dielectric A layer or a resin protective layer such as an ultraviolet curable resin may be provided as necessary. Further, after forming the reflective layer or the like, or after further forming the above-mentioned resin protective layer, the two substrates may be opposed to each other and bonded with an adhesive.

The recording layer is preferably preliminarily crystallized by irradiation with light such as a laser beam or a xenon flash lamp before actual recording.

[0051]

EXAMPLES The present invention will be described below based on examples.

(Analysis and measurement method) The compositions of the reflective layer and the recording layer were confirmed by ICP emission analysis (manufactured by Seiko Denshi Kogyo KK). The C / N and the erasing rate (difference in reproduced carrier signal intensity after recording and after erasing) were measured by a spectrum analyzer. The jitter after overwriting was measured by a time interval analyzer.

The film thickness during the formation of the recording layer, the dielectric layer and the reflective layer was monitored by a crystal oscillator film thickness meter. The thickness of each layer was measured by observing the cross section with a scanning or transmission electron microscope.

The crystal structure of the reflective layer was measured using a powder X-ray diffractometer (CuKα). The optical constant of the reflective layer is measured by ellipsometry (NPDM-100 manufactured by Nikon Corporation).
0). The heat of formation of the oxide of the metal element constituting the reflective layer was evaluated by differential scanning calorimetry (DSC).

(Fabrication, Evaluation) (Example 1) Thickness 1.2 mm, diameter 13 cm, 1.2 μ
A recording layer, a dielectric layer, and a reflective layer were formed by a high-frequency sputtering method while rotating an m-pitch polycarbonate substrate with a spiral groove at 30 rpm.

First, the inside of the vacuum vessel was evacuated to 1 × 10 ^-5 Pa, and then SiO 2 in an Ar gas atmosphere of 2 × 10 ^-1 Pa.
ZnS containing 20 mol% of ₂ was sputtered to form a 230 nm-thick first dielectric layer on the substrate. continue,
A three-element single target composed of Ge, Sb, and Te is sputtered to form a film having a composition Ge _0.24 Sb _0.22 Te _{0.54 and} a film thickness of 20 n.
m recording layer was formed. Further, a second dielectric layer of the same material as the first dielectric layer is formed to a thickness of 20 nm, and Hf, S
A two-element single target made of i was sputtered to form a reflection layer having a composition Hf _0.8 Si _{0.2 and} a thickness of 60 nm.

As a result of DSC, the absolute value of heat of formation of SiO ₂ was 912 kJ / mol, whereas that of HfO ₂ was 1118 kJ / mol, which was larger than that of SiO ₂ . Separately from this, the above-mentioned reflective layer 15 is formed on the glass substrate.
As a result of 0 nm sputtering and measurement of optical constants, a wavelength of 6
At 80 nm, the real part of the refractive index was 3.0 and the imaginary part was 4.0. When the crystal structure was examined by an X-ray diffractometer, no sharp peak corresponding to the structure of Hf silicide appeared, and it was found to be amorphous. After the disk was taken out of the vacuum container, an acrylic ultraviolet curable resin (SD-101 manufactured by Dainippon Ink and Chemicals, Inc.) was spin-coated on the reflective layer and cured by ultraviolet irradiation to give a film thickness of 10
A μm resin layer was formed to obtain an optical recording medium of the present invention. Further, a double-sided disk was prepared by laminating a disk of the same type as the disk formed in the same manner with a hot melt adhesive (XW30 manufactured by Toagosei Kagaku Kogyo Co., Ltd.).

This optical recording medium was irradiated with a semiconductor laser beam having a wavelength of 820 nm to crystallize and initialize the recording layer on the entire surface of the disk.

As a result of calculation from the refractive index and the thickness of each layer at a light wavelength of 680 nm, the amounts of light absorption in the recording layer of this disc in the crystalline state and the amorphous state are 70% and 6 respectively.
It was 4%, and the light absorption amount in the crystalline state was 6% larger than that in the amorphous state. Further, the reflectance in the crystalline state obtained from the calculation was 22%, which was almost the same as the value actually measured in the mirror portion of the disk, and therefore the result of this calculation was confirmed to be valid.

Thereafter, this disk was moved at a linear velocity of 20 m / s.
At a frequency of 3.00 MHz (duty 4) using a semiconductor laser optical head with a numerical aperture of 0.55 and a wavelength of 680 nm on a track with a radius of 57 mm.
5%), peak power 8-15mW, bottom power 3
After overwriting recording 100 times with a semiconductor laser beam modulated to each condition of ˜8 mW, a semiconductor laser beam with a reproducing power of 1.2 mW is irradiated to C under a condition of a bandwidth of 30 kHz.
/ N was measured.

The frequency of 1.88 MHz (duty 45
%), The semiconductor laser light modulated in the same manner as above was overwritten and recorded 100 times, and then one-beam overwriting was performed at a frequency of 3.00 MHz, and the erasing rate of the pre-recorded signal of 1.88 MHz at this time was measured. Peak power 10mW
With the above, a C / N of 60 dB or more was obtained, and at the bottom power of 5.5 to 7.5 mW, an erasing rate of 25 dB or more and a maximum of 32 dB was obtained.

Further, the jitter at the edge of the end portion of the reproduced signal of the recording mark in this portion was measured. Peak power 13
The jitter value (σ) is 2.mW and the bottom power is 6.5 mW.
0 ns.

Further, under the conditions of a peak power of 13 mW, a bottom power of 6.5 mW, and a frequency of 3.00 MHz, one beam overwrite was repeated 10,000 times, and the same measurement was carried out. In each case, almost no deterioration was observed within 2 dB.

Under the same conditions as above, only the linear velocity is 10 m / s.
When C / N, erasure rate, and jitter after overwriting were measured, the peak power was 7 mW or more.
Deletion rate of 25d with bottom power of 3 to 5.5mW and above dB
The jitter value after overwriting was 2.5 ns at B or higher, a peak power of 9 mW, and a bottom power of 4 mW.

After the optical recording medium was left in an environment of 80 ° C. and 80% relative humidity for 1000 hours, the recorded portion was reproduced, but the change in C / N was less than 2 dB, and there was almost no change. Further, recording and erasing were performed again, and the C / N and the erasing rate were measured.

(Example 2) Z was used as the material for the reflective layer of the optical recording medium.
r _0.3 Ge _0.7 and the composition of the recording layer was Nb _0.005 Ge
_A disk was prepared and evaluated in the same manner as in Example 1 _{except that 0.175} Sb _0.26 Te _0.56 , the film thickness was 13 nm, and the thickness of the second dielectric layer was 10 nm.

Apart from this, in the same manner as in Example 1,
As a result of measuring the optical constant, the real part of the refractive index was 4.5 and the imaginary part was 2.7 at the wavelength of 680 nm.

When the crystal structure was examined by an X-ray diffractometer, no sharp peak appeared and it was found to be amorphous.

As a result of DSC, it was found that the absolute value of heat of formation of GeO ₂ was 580 kJ / mol, whereas that of ZrO ₂ was 1101 kJ / mol, which was larger than that of GeO ₂ .

As a result of calculation from the refractive index and thickness of each layer at a light wavelength of 680 nm, the amounts of light absorption in the recording layer of this disc in the crystalline state and in the amorphous state were 58% and 4%, respectively.
It was 0%, and the light absorption amount in the crystalline state was 18% larger than that in the amorphous state. Further, the reflectance in the crystalline state obtained from the calculation was 19%, which was almost the same as the value actually measured by the mirror portion of the disk, and therefore it was confirmed that this calculation result was appropriate.

When measured in the same manner as in Example 1, C / N was 55 dB or more at a linear velocity of 10 m / s and 20 m / s.
An erasing rate of 25 dB or more was obtained. Also, when the jitter after overwriting was measured, the linear velocity was 10 m / s,
It was 2.3 ns and 1.7 ns at m / s.

The recording laser power is the peak power,
When the one-beam overwrite was repeated 10,000 times in the same manner as in Example 1 except that the bottom power was adjusted to the optimum value for this disc, the changes in C / N and erase rate were
Almost no deterioration was observed within 2 dB.

Furthermore, after the optical recording medium was left in an environment of 80 ° C. and 80% relative humidity for 1000 hours, the recorded portion was reproduced, but the change in C / N was less than 2 dB, and there was almost no change. Further, recording and erasing were performed again, and the C / N and the erasing rate were measured.

(Example 3) The material of the reflective layer of the optical recording medium was T.
i _0.1 Si _0.9 and the composition of the recording layer is Pd 0.001 Nb
_0.005 Ge _0.169 Sb _0.265 Te _0.56 , film thickness 11 nm
A disk was prepared and evaluated in the same manner as in Example 1 except that the second dielectric layer had a thickness of 5 nm. Separately, the optical constant was measured in the same manner as in Example 1, and as a result, at the wavelength of 680 nm, the real part of the refractive index was 4.
0 and the imaginary part were 2.5.

When the crystal structure was examined by an X-ray diffractometer, no sharp peak appeared and it was found to be amorphous.

As a result of DSC, it was found that the absolute value of the heat of formation of TiO ₂ was 945 kJ / mol, which was larger than that of SiO ₂ .

As a result of calculation from the refractive index and thickness of each layer at a light wavelength of 680 nm, the amount of light absorption in the crystalline state and the amount of amorphous state in the recording layer of this disc were 52% and 3 respectively.
2%, and the light absorption amount in the crystalline state was 20% larger than that in the amorphous state. Further, the reflectance in the crystalline state obtained from the calculation was 19%, which was almost the same as the value actually measured by the mirror portion of the disk, and therefore it was confirmed that this calculation result was appropriate.

When measured in the same manner as in Example 1, at linear velocities of 10 m / s and 20 m / s, C / N was 55 dB or more,
An erasing rate of 25 dB or more was obtained. Also, when the jitter after overwriting was measured, the linear velocity was 10 m / s,
It was 1.9 ns and 1.3 ns at m / s.

The recording laser power is the peak power,
When the one-beam overwrite was repeated 10,000 times in the same manner as in Example 1 except that the bottom power was adjusted to the optimum value for this disc, the changes in C / N and erase rate were
Almost no deterioration was observed within 2 dB.

Further, after the optical recording medium was placed in an environment of 80 ° C. and 80% relative humidity for 1000 hours, the recorded portion was reproduced, but the change in C / N was less than 2 dB, and there was almost no change. Further, recording and erasing were performed again, and the C / N and the erasing rate were measured.

(Example 4) Z was used as the reflection layer material of the optical recording medium.
r _0.4 Si _0.6 and the composition of the recording layer is Pd 0.002 Nb
_A disk was prepared and evaluated in the same manner as in Example 1 _{except that 0.003} Ge _0.175 Sb _0.26 Te _0.56 , the film thickness was 11 nm, and the second dielectric layer had a thickness of 5 nm.

Apart from this, in the same manner as in Example 1,
As a result of measuring the optical constant, the real part of the refractive index was 3.6 and the imaginary part was 3.4 at the wavelength of 680 nm.

When the crystal structure was examined by an X-ray diffractometer, no sharp peak appeared and it was found to be amorphous.

As a result of calculation from the refractive index and thickness of each layer at a light wavelength of 680 nm, the amounts of light absorption in the crystalline state and the amorphous state in the recording layer of this disc were 55% and 3 respectively.
It was 5%, and the light absorption amount in the crystalline state was 20% larger than that in the amorphous state. In addition, the reflectance of the crystalline state obtained from the calculation is 20%, which is almost the same as the value actually measured by the mirror portion of the disk, so that it can be confirmed that this calculation result is appropriate.

When measured in the same manner as in Example 1, at linear velocities of 10 m / s and 20 m / s, C / N was 55 dB or more,
An erasing rate of 25 dB or more was obtained. Also, when the jitter after overwriting was measured, the linear velocity was 10 m / s,
It was 2.0 ns and 1.5 ns at m / s.

The recording laser power is the peak power,
When the one-beam overwrite was repeated 10,000 times in the same manner as in Example 1 except that the bottom power was adjusted to the optimum value for this disc, the changes in C / N and erase rate were
Almost no deterioration was observed within 2 dB.

Furthermore, after the optical recording medium was placed in an environment of 80 ° C. and 80% relative humidity for 1000 hours, the recorded portion was reproduced, but the change in C / N was less than 2 dB, and there was almost no change. Further, recording and erasing were performed again, and the C / N and the erasing rate were measured.

Comparative Example Similar to Example 1, except that the reflective layer material of the optical recording medium of Example 1 was Al, the thickness of the recording layer was 20 nm, and the thickness of the second dielectric layer was 5 nm. Then, a disk having a conventional quenching structure was manufactured.

Separately from this, 1 Al was deposited on the glass substrate.
As a result of spattering 50 nm and measuring optical constants, when the wavelength is 680 nm, the real part of the refractive index is 1.7 and the imaginary part is 3.1.
Met.

When the crystal structure was examined by an X-ray diffractometer, a peak corresponding to the face-centered cubic structure of Al appeared, and it was found that the crystal had a face-centered cubic structure.

The amount of light absorbed in the recording layer of this disc was calculated from the refractive index and thickness of each layer, and as a result, the wavelength of light was 680 n.
In m, both the crystalline state and the amorphous state were 77%. The reflectance of the crystalline state calculated from the calculation is 19%
Since it agrees with the value actually measured by the mirror part of the disk, it was confirmed that the result of this calculation is appropriate.

When measured in the same manner as in Example 1, there was no difference in C / N and erase rate at a linear velocity of 10 m / s from Example 1, but the jitter after overwriting was 3.0 ns, and Was inferior. C / at a linear velocity of 20 m / s
N was obtained over 55 dB, but the maximum erasure rate was 20 d
B, the jitter after overwriting is 4.0 ns, and the first embodiment is shown.
Was inferior.

[0093]

According to the present invention, since the optical recording medium is provided with a novel reflective layer formed of an alloy of one or more kinds of metals and Si or / and Ge, the following effects are obtained.

(1) Both the high linear velocity and the low linear velocity have good erasing rate and good jitter characteristics after overwriting. (2) Even if recording and erasing are repeated a large number of times, the operation is stable and there is almost no deterioration of characteristics or occurrence of defects. (3) Excellent heat and moisture resistance and oxidation resistance, and long life. (4) Can be easily manufactured by sputtering.

Claims (8)

[Claims] 1. Information can be recorded, erased, and reproduced by irradiating a recording layer formed on a substrate with light, and the recording and erasing of information can be performed in a phase between an amorphous phase and a crystalline phase. An optical recording medium having at least a first dielectric layer, a recording layer, a second dielectric layer and a reflective layer, wherein the reflective layer is made of an alloy of one or more metals and Si or / and Ge. An optical recording medium characterized by being formed. 2. The reflection layer is formed of one or more kinds of metals having an absolute value of heat of formation of oxides larger than Si or / and Ge and an alloy composed of Si or / and Ge. The optical recording medium according to claim 1, wherein: 3. The composition of the material of the reflective layer is an alloy having a composition represented by the following formula:
The optical recording medium described. Compositional formula M _x X _1-x 0.1 ≦ x ≦ 0.8 where M is Be, Al, Sc, Ti, Cr, Mn,
Fe, Co, Ni, Cu, Y, Zr, Nb, Ru, R
h, Pd, Ag, Hf, Re, Os, Ir, Pt, Au
Represents at least one metal selected from
Represents at least one element selected from Si and Ge,
x represents the molar ratio of the elements. 4. The composition of the material of the reflective layer is an alloy having a composition represented by the following formula:
The optical recording medium described. Compositional formula M _x X _1-x 0.1 ≦ x ≦ 0.8 where M represents at least one metal selected from Zr, Ti and Hf, and X is selected from Si and Ge. Represents at least one element, and x represents the molar ratio of the elements. 5. The optical recording medium according to claim 1, wherein the crystallographic structure of the material of the reflective layer is substantially amorphous. 6. The real part of the refractive index of the material of the reflective layer is 3.0 or more and 5.0 or less, and the imaginary part of the refractive index is 2.5 or more and 4.0 or less. 2. The optical recording medium according to 2. 7. The optical recording medium according to claim 1, wherein the thickness of the recording layer is 5 nm or more and 40 nm or less, and the thickness of the second dielectric layer is 3 nm or more and 30 nm or less. 8. The optical recording medium according to claim 1, wherein the recording layer has a film thickness of 5 nm or more and 15 nm or less, and the second dielectric layer has a film thickness of 3 nm or more and 15 nm or less.