JPH1139716A - Optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve recording characteristics such as a high recording sensitivity, a high ratio of a carrier to noise and a high erase rate by successively laminating a first dielectric layer/a recording layer/a second dielectric layer/a reflection layer and specifying refractive indexes, attenuation coefficients and layer thickness in wavelengths within a specified range of the respective layers. SOLUTION: When recording/erasing is performed by light irradiation of a wavelength 390-450 nm, since high contrast is obtained, the refractive index of a first dielectric layer is made within the range of 2.2-2.3, the layer thickness is made to 30-500 nm, a refractive index and an exhaustion coefficient in the amorphous state of the recording layer are made to 2.58-3.3 and 2.6-2.9, a refractive index and an attenuation coefficient in the crystal state are made to 1.77-2.5 and 3.2-3.8, the recording layer thickness is made to 7-35 nm, a second dielectric layer refractive index and layer thickness are made to 2.25-2.4 and 0-25 nm, a reflection layer refractive index and attenuation coefficient are made to 0.4-0.6 and 3.8-4.25, the irradiation power of light recording/erasing is secured, the recording at a high linear velocity is performed, the peeling of the first dielectric layer and the crack occurrence are prevented and stable contrast is obtained.

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 has a function of erasing and rewriting recorded information using green to blue laser light, and is capable of recording information signals at high speed and high density. It relates to an optical recording medium.

[0002]

2. Description of the Related Art A rewritable phase change optical recording medium using a phase change technique is known to have a recording layer mainly composed of a Te alloy. During recording, a focused laser light pulse is applied to the crystalline recording layer for a short time to partially melt the recording layer. The melted portion is quenched by thermal diffusion and solidified to form an amorphous recording mark. 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 lower than the melting point of the recording layer and higher than the crystallization temperature to crystallize the amorphous recording mark and return to the original unrecorded state. return.

[0004] In such an optical recording medium having a Te alloy as a recording layer, the crystallization temperature is high, and high-speed overwriting with a circular beam is possible only by modulating the irradiation power (T. Ohta et al, Proc. . Int. Symp. On optical Me
mory 1989 p49-50). An optical disk is an example of such a rewritable phase change optical recording medium. Since the optical disc performs recording and reproduction by condensing the laser light, the wavelength of the laser light is one of the factors that determine the recording capacity of the optical disc.

In order to increase the recording capacity of such optical discs, the development of shorter wavelength laser light and a higher NA of the lens has been developed. At present, a recording / reproducing apparatus using a semiconductor laser having a wavelength of 680 nm has been commercialized. ing. Investigation of further shortening of the wavelength has been conducted, and wavelengths of 470 nm and 430 nm have been studied.
Development of laser light of nm, 410 nm, etc. is also progressing. Optical discs are designed to obtain good recording sensitivity, carrier-to-noise ratio, erasure rate, and other recording characteristics with respect to the wavelength used for recording, reproduction, and erasure. It is difficult to obtain similar properties when used under laser light. Further, by selecting the refractive index n, the extinction coefficient k, and the thickness of each layer constituting the optical disk, optical characteristics such as contrast, which is a difference in reflectance between the amorphous state and the crystalline state, change. Therefore, in order to obtain a high contrast in a short wavelength region as described above, there is a problem that selection of a refractive index, an extinction coefficient, and a layer thickness is greatly restricted.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the optical recording medium and to provide an optical recording medium which can obtain a high contrast in recording and reproduction using a short-wavelength laser beam. is there.

Another object of the present invention is to provide an optical recording medium having high recording sensitivity and excellent recording characteristics such as a carrier-to-noise ratio and an erasing ratio.

It is still another object of the present invention to provide an optical recording medium which is inexpensive and has excellent productivity.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical recording medium in which information is recorded and erased by a phase change between an amorphous phase and a crystalline phase due to irradiation of light, and at least a first layer is formed on a transparent substrate. 1 dielectric layer / recording layer / second dielectric layer / reflection layer are laminated in this order, and the refractive index, extinction coefficient, and layer thickness of each layer at a wavelength of 390 nm to 450 nm are represented by the following formulas. This is achieved by an optical recording medium characterized by the following relationship.

2.2 ≦ n _a ≦ 2.3 30 ≦ d _a ≦ 500 2.58 ≦ n α ≦ 3.3 2.6 ≦ k α ≦ 2.9 1.77 ≦ n _c ≦ 2.5 3.2 ≦ k _c ≦ 3.8 7 ≦ d _r ≦ 35 (nm) 2.25 ≦ n _b ≦ 2.4 0 <d _b ≦ 25 (nm) 0.4 ≦ nβ ≦ 0.6 3.8 ≦ kβ ≦ 4.25 where, n _a is the refractive index of the first dielectric layer, d _a is the thickness of the first dielectric layer (nm), n [alpha is the refractive index of the amorphous state of the recording layer,
kα is the extinction coefficient of the amorphous state of the recording layer, n _c is the refractive index of the crystalline state of the recording layer, k _c is the extinction coefficient of the crystalline state of the recording layer,
d _r is the thickness of the recording layer (nm), n _b is the refractive index of the second dielectric layer, d _b is the thickness of the second dielectric layer (nm), nβ is the refractive index of the reflective layer, Keibeta reflection Indicates the extinction coefficient of the layer.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The optical recording medium of the present invention has a wavelength of 3
Even in the case where recording and erasing is performed by irradiating light having a wavelength of 90 nm or more and 450 nm or less, it is preferable that the refractive index, the extinction coefficient, and the layer thickness in the above-described formulas be set to obtain high contrast. is important.

When the refractive index of the first dielectric layer in the present invention is smaller than 2.2, the reflectivity increases and the recording sensitivity decreases, or the irradiation power of light for recording and erasing becomes insufficient. Problems such as difficulty in recording at high linear velocity occur. If the refractive index is greater than 2.3, the change in the reflectance difference between the amorphous portion and the crystalline portion of the recording mark relative to the thickness of the first dielectric layer becomes large, deteriorating the signal contrast during reproduction. Let me do it.

As for the thickness of the first dielectric layer, the fluctuation of the reflectance and contrast due to the thickness of the layer is very small.
It is approximately 30 to 500 nm. The first dielectric layer is more preferably 50 to 400 nm because it is difficult to peel off from the substrate or the recording layer and hardly causes defects such as cracks.

In the present invention, the dielectric layer has an 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 and deteriorating the recording characteristics during recording, and an optical interference effect. This has the effect of improving the signal contrast during reproduction.

In the present invention, the second wavelength of 450 nm or less is used.
It is preferable to configure the second dielectric layer so that the refractive index n of the dielectric layer is in the range of 2.25 ≦ n _b ≦ 2.4.
It is preferable because recording characteristics and optical characteristics such as N and erasure ratio can be obtained.

The thickness of the second dielectric layer is greater than about 0 and about 250 nm. To be 25 nm or less,
This is preferable because the range of erasing power at which a good erasing rate can be obtained is wide. More preferably, the thickness is set to 10 to 20 nm because a stable contrast can be obtained.

As the dielectric layer, ZnS, Si
Inorganic thin films such as O ₂ , silicon nitride, and aluminum oxide can be used. In particular, ZnS thin film, Si, Ge, Al,
Thin films of oxides of metals such as Ti, Zr, Ta, etc., Si, A
For example, a thin film of a nitride such as 1, a thin film of a carbide such as Ti, Zr, and Hf and a film of a mixture thereof are preferable because of high heat resistance. Further, those obtained by mixing carbon or a fluoride such as MgF _{2 with} these are also preferably used because the residual stress of the film is small. In particular, a mixed film of ZnS and SiO ₂ or ZnS is used for the base dielectric layer and the second dielectric layer.
And is possible to use SiO ₂ and mixed film of carbon, recording, by the repetition of erasing, recording sensitivity, (the difference between the reproduced carrier signal intensity after erasure and after recording) carrier to noise ratio (C / N) and erasure rate It is preferable since deterioration such as deterioration does not easily occur, and SiO ₂ 1
More preferably, it is 5 to 35 mol% and 1 to 15 mol% of carbon. Further, the second dielectric layer may be composed of a plurality of layers such as a laminate of a layer of a mixed film of ZnS and SiO ₂ and an SiO ₂ layer.

The material of the recording layer of the present invention is a chalcogen compound containing Te as a main component, which can take at least two states, a crystalline state and an amorphous state. As the recording layer of the present invention,
Although not particularly limited, Pd-Ge-Sb-Te,
Nb-Ge-Sb-Te, Pd-Nb-Ge-Sb-T
e, Ni-Ge-Sb-Te, Ge-Sb-Te, Co
-Ge-Sb-Te, In-Se, In-Sb-Te,
Ag-In-Sb-Te, Ag-V-In-Sb-Te
and so on. Pd-Ge-Sb-Te, Nb-Ge-Sb-T
e, Pd-Nb-Ge-Sb-Te, Ni-Ge-Sb
-Te, Ge-Sb-Te, and Co-Ge-Sb-Te are preferred. Especially Pd-Ge-Sb-Te alloy, Pd-N
b-Ge-Sb-Te is preferable because it has a short erasing time, is capable of repeating recording and erasing many times, and has excellent recording characteristics such as C / N and erasing rate.
A Pd-Nb-Ge-Sb-Te alloy is more preferred because of its excellent properties.

In the present invention, the optical constant n and the extinction coefficient k of the recording layer at a wavelength of 450 nm or less are 1.77 ≦ n _C ≦ 2.5 and 3.2 ≦ k _C ≦ 3.8 in a crystalline state. Yes,
In the amorphous state, 2.58 ≦ nα ≦ 3.3, 2.6 ≦ kα ≦
It is preferable to configure the composition of the recording layer so as to fall within the range of 2.9 because good recording characteristics such as C / N and erasure ratio can be obtained. As the above specific alloy, Pd-G
e-Sb-Te, Nb-Ge-Sb-Te, Pd-Nb
-Ge-Sb-Te.

The recording layer has a thickness of 5 to 150 nm. In particular, the recording and erasing sensitivity is high, the recording and erasing can be performed many times, and the fluctuation of contrast is small.

In the present invention, the refractive index n and the extinction coefficient k of the reflective layer at a wavelength of 450 nm or less are 0.4 ≦ nβ ≦ 0.6,
It is preferable to form the reflective layer so as to satisfy the range of 3.8 ≦ kβ ≦ 4.25, since it has excellent thermal stability and can reduce deterioration of recording characteristics.

As a material of the reflection layer, a metal such as Al or Au having light reflectivity, containing these as a main component, Ti, C
alloys containing additional elements such as r and Hf, and metals such as Al and Au, metal nitrides such as Al and Si, metal oxides,
A mixture of a metal compound such as a metal chalcogenide can be used. Metals such as Al and Au and alloys containing these as main components are preferable because of their high light reflectivity and high thermal conductivity. As an example of the above alloy, Al
To Si, Mg, Cu, Pd, Ti, Cr, Hf, Ta,
At least one element such as Nb or Mn is added in a total of 5 atomic% or less and 1 atomic% or more, or Au is added to C
at least one of r, Ag, Cu, Pd, Pt, Ni, etc.
Examples include those in which a total of 1 atomic% or more and 20 atomic% or less of various elements are added. In particular, Al or an alloy containing Al as a main component is preferable because the price of the material is low.
In particular, because of good corrosion resistance, Al and Ti, C
at least one metal selected from the group consisting of r, Ta, Hf, Zr, Mn, and Pd in a total amount of 0.5 atomic% to 5 atomic%
The alloys added below are preferred. Furthermore, since the corrosion resistance is good and hillocks and the like hardly occur, the Al
-Hf-Pd alloy, Al-Hf alloy, Al-Ti alloy,
It is preferable to use an Al-based alloy of any of AlTi-Hf alloy, Al-Cr alloy, Al-Ta alloy, Al-Ti-Cr alloy and Al-Si-Mn alloy. Among these Al alloys, an Al-Hf-Pd alloy having a composition represented by the following formula has particularly excellent thermal stability, so that the recording characteristics are less deteriorated by repeating recording and erasing many times. can do.

Pd _j Hf _k Al _1-jk 0.001 <j <0.01 0.005 <k <0.10 where j and k are the number of atoms of each element (the number of moles of each element).
Represents

The thickness of the above-mentioned reflective layer is approximately 10 nm or more and 200 nm in any case of any alloy.
Hereinafter, the thickness is more preferably set to 50 to 200 nm.

Further, in order to obtain a high contrast at a wavelength of 390 nm to 450 nm, the refractive index of each layer,
It is preferable that the extinction coefficient and the thickness of the layer have any relationship represented by the following formula.

[0026] If the wavelength is less 425nm or 390 nm, (integer including a is _{0) 2.2 ≦ n a ≦ 2.3} 80a + 100 ≦ d a ≦ 80a + 150 (nm) 2.58 ≦ nα ≦ 3.3 2 .64 ≦ kα ≦ 2.9 1.77 ≦ n c ≦ 2.2 3.2 ≦ k c ≦ 3.7 10 ≦ d r ≦ 35 (nm) 2.3 ≦ n b ≦ 2.4 0 <d _{b ≦ 15 (nm) 0.4 ≦} nβ ≦ 0.52 3.8 ≦ kβ ≦ 4.1 or a _{2.2 ≦ n a ≦ 2.3 100a +} 30 ≦ d a ≦ 100a + 80 (nm) (a is 0 including integer) 2.58 ≦ nα ≦ 3.3 2.64 ≦ kα ≦ 2.9 1.77 ≦ n c ≦ 2.2 3.2 ≦ k c ≦ 3.7 10 ≦ d r ≦ 35 (nm) 2.3 ≦ n _b ≦ 2.4 15 <d _b ≦ 25 (nm) 0.4 ≦ nβ ≦ 0.52 3.8 ≦ kβ ≦ 4.1 Further, when the wavelength exceeds 425 nm, 4 For 50nm or _{less, 2.2 ≦ n a ≦ 2.25 100a} + 30 ≦ d a ≦ 100a + 70 (nm) (a is an integer including 0) 2.8 ≦ nα ≦ 3.3 2.64 ≦ kα ≦ 2. _{9 1.85 ≦ n c ≦ 2.2 3.2} ≦ k c ≦ 3.7 10 ≦ d r ≦ 35 (nm) 2.25 ≦ n b ≦ 2.3 0 <d b ≦ 15 (nm) 0 .5 ≦ nβ ≦ 0.6 4.0 ≦ kβ ≦ 4.25 _{or, 2.2 ≦ n a ≦ 2.25 100a} + 50 ≦ d a ≦ 100a + 110 (nm) (a
Integer) 2.8 ≦ nα ≦ 3.3 2.64 ≦ kα ≦ 2.9 1.85 ≦ n c ≦ 2.2 3.2 ≦ k c ≦ 3.7 10 ≦ d r ≦ 35 comprising 0 _{(nm) 2.25 ≦ n b ≦} 2.3 15 <d b ≦ 25 (nm) 0.5 ≦ nβ ≦ 0.6 4.0 ≦ kβ ≦ 4.25 ( where, n _a first dielectric refractive index of the material layer, d _a is the thickness of the first dielectric layer (nm), n [alpha is the refractive index of the amorphous state of the recording layer, ka is the extinction coefficient of the amorphous state of the recording layer, n _c is recorded refractive index of the crystal state of the layer, k _c is the extinction coefficient of the crystalline state of the recording layer, the thickness of d _r is the recording layer (nm), n _b is the refractive index of the second dielectric layer, d _b is the second The thickness (nm) of the dielectric layer, nβ represents the refractive index of the reflective layer, and kβ represents the extinction coefficient of the reflective layer.) As the material of the substrate of the present invention, various transparent synthetic resins,
Transparent glass or 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, polymethyl methacrylate, Polyolefin resin, epoxy resin, polyimide resin and the like can be mentioned. In particular, polycarbonate resins and amorphous polyolefin resins are preferred because of their low optical birefringence, low hygroscopicity, and easy molding.

The thickness of the substrate is not particularly limited, but is practically 0.01 mm to 5 mm.
If it is less than 0.01 mm, even when recording with a light beam focused from the substrate side, it is easily affected by dust and becomes 5 mm
In the case of exceeding, 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. In addition, these substrates, after forming the recording layer and the like,
An air sandwich structure, an air incident structure, and a close bonding structure may be used by using two substrates.

As a light source used for recording on the optical recording medium of the present invention, a high-intensity light source such as a laser beam or a strobe light can be mentioned. In particular, a semiconductor laser beam can be reduced in size and power consumption. This is preferable because the modulation is easy.

The recording is performed by irradiating a laser beam pulse or the like to the crystalline recording layer 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. Erasing can be performed by irradiating a laser beam to crystallize an amorphous recording mark or to make a crystalline recording mark amorphous. Since the recording speed can be increased and the recording layer is hardly deformed, it is preferable to form an amorphous recording mark during recording and crystallize during erasing. In addition, the light intensity is high at the time of forming a recording mark and slightly weakened at the time of erasing, and rewriting is performed by one light beam irradiation.
Beam overwriting is preferable because the time required for rewriting is reduced.

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

The method for forming the reflective layer, the dielectric layer, and the recording layer on the substrate includes a method of forming a thin film in a vacuum, such as a vacuum 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 quartz crystal film thickness meter or the like.

The formation of the recording layer and the like may be performed while the substrate is fixed, or moved or rotated. Since the in-plane uniformity of the film thickness is excellent, the substrate may be rotated on its own or combined with revolution.

As a preferred layer constitution of the optical recording medium of the present invention, a transparent substrate / first dielectric layer / recording layer / second dielectric layer /
One obtained by laminating reflective layers in this order is exemplified. However, the present invention is not limited to this. As long as the effects of the present invention are not significantly impaired, scratches,
In order to prevent deformation, a dielectric layer such as ZnS or SiO2 or a resin protective layer such as an ultraviolet curable resin may be provided as necessary. Light is incident from the transparent substrate side. After the formation of the reflective layer or the like, or after the formation of the above-mentioned resin protective layer, the two substrates may be opposed to each other and bonded with an adhesive.

Before the actual recording, the recording layer is preferably irradiated with a laser beam, a xenon flash lamp, or the like to be crystallized in advance.

[0037]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments.

(Analysis and Measurement Methods) The composition of the reflective layer and the recording layer was determined by ICP emission spectrometry (SPS400 manufactured by Seiko Denshi Kogyo KK).
0). The reflectance was measured by a spectrophotometer (CM2002 manufactured by Minolta Co., Ltd.).

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

(Example 1) Thickness 1.2 mm, diameter 12c
m while rotating the polycarbonate substrate at 40 revolutions per minute, the recording layer, the dielectric layer,
A reflective layer was formed. First, the inside of the vacuum vessel is 1 × 10 ⁻⁴ Pa
, And a ZnS target Zn added with 20 mol% of SiO ₂ in an Ar gas atmosphere of 2 × 10 ^-1 Pa.
S was sputtered to form a first dielectric layer having a thickness of 120 nm on the substrate. Then, Pd, Nb, Ge, Sb, Te
Sputtering target consisting of Nb _0.006 P
thereby forming a d _{0.0 01} Ge _0.173 recording layer having a thickness of 10nm of Sb _0.26 Te _0.56. Further, the second dielectric layer is formed to a thickness of
Then, an Al _98.1 Hf _1.7 Pd _0.2 alloy was sputtered thereon to form a reflectance of 80 nm in thickness, thereby obtaining an optical recording medium of the present invention.

Further, after the reflection layer was formed, an ultraviolet-curable resin (SD-101 manufactured by Dainippon Ink and Chemicals, Inc.) was spin-coated and cured by irradiation with ultraviolet light to form a resin layer having a thickness of 10 μm.

The recording layer on the entire surface of the optical disk was crystallized with a beam of a semiconductor laser having a wavelength of 810 nm and initialized.

Next, the wavelength of the obtained optical recording medium is 410 nm.
As a result of measurement of the reflectivity at, the amorphous part and the crystal part were obtained at 9.5% and 22.4%, respectively, and the contrast was about 13%.

The refractive index and extinction coefficient of each layer formed on the substrate in the same manner as in this optical recording medium were measured by ellipsometry (NPDM-1000, manufactured by Nikon Corporation).
The refractive index of the dielectric layer is 2.28, the refractive index of the amorphous portion of the recording layer is 2.91, the extinction coefficient is 2.67, the refractive index of the crystalline portion of the recording layer is 1.98, and the extinction coefficient is 3.30, the refractive index of the second dielectric layer was 2.33, the refractive index of the reflective layer was 0.48, and the extinction coefficient was 3.90.

(Embodiment 2) The first example of the optical recording medium of Embodiment 1
The thickness of the dielectric layer is 160 nm, and the thickness of the second dielectric layer is 2
An optical recording medium having the same configuration as in Example 1 was prepared except that the thickness was set to 0 nm, and the same measurement as in Example 1 was performed. Wavelength 41
The reflectance at 0 nm is as follows: amorphous portion 15.3%, crystalline portion 3
2.5% and contrast was about 17%.

When the values of the refractive index and the extinction coefficient were measured in the same manner as in Example 1, the refractive index of the first dielectric layer was 2.28, and the refractive index of the amorphous portion of the recording layer was 2.28. 91, the extinction coefficient is 2.67, the refractive index of the crystal part of the recording layer is 1.98, the extinction coefficient is 3.30, the refractive index of the second dielectric layer is 2.33,
The reflective layer had a refractive index of 0.48 and an extinction coefficient of 3.90.

(Example 3) An optical recording medium having the same configuration as in Example 1 was manufactured, and the reflectance at a wavelength of 430 nm was measured in the same manner as in Example 1. The reflectance at a wavelength of 430 nm was 8.5% in the amorphous part, 21.3% in the crystal part, and the contrast was about 13%.

When the values of the refractive index and the extinction coefficient were measured in the same manner as in Example 1, the refractive index of the first dielectric layer was 2.26, and the refractive index of the amorphous portion of the recording layer was 3.26. 07, the extinction coefficient is 2.67, the crystal part of the recording layer has a refractive index of 2.14, the extinction coefficient is 3.40, the refractive index of the second dielectric layer is 2.30,
The reflective layer had a refractive index of 0.53 and an extinction coefficient of 4.06.

Example 4 An optical recording medium having the same structure as in Example 2 was manufactured, and the reflectance at a wavelength of 430 nm was measured in the same manner as in Example 1. The reflectance at a wavelength of 430 nm was 14.6% for the amorphous part, 31.6% for the crystal part, and the contrast was about 17%.

When the values of the refractive index and the extinction coefficient were measured in the same manner as in Example 1, the refractive index of the first dielectric layer was 2.26, and the refractive index of the amorphous portion of the recording layer was 3.26. 07, the extinction coefficient is 2.67, the crystal part of the recording layer has a refractive index of 2.14, the extinction coefficient is 3.40, the refractive index of the second dielectric layer is 2.30,
The reflective layer had a refractive index of 0.53 and an extinction coefficient of 4.06.

Example 5 The composition of the recording layer was Ge _17.1 Sb
An optical recording medium having the same configuration as in Example 1 was prepared except for using only _26.4 Te _56.6, and the reflectance at a wavelength of 410 nm was measured in the same manner as in Example 1. 410n wavelength
m has a reflectance of 11.2% for the amorphous part and 25.
7% and contrast was 14.5%.

When the values of the refractive index and the extinction coefficient of the recording layer were measured in the same manner as in Example 1, the refractive index of the amorphous portion was 2.73, the extinction coefficient was 2.71, and the value of the crystalline portion was 2.71. The refractive index is 1.
80 and the extinction coefficient was 3.33.

Example 6 The composition of the recording layer was Ge _17.1 Sb
An optical recording medium having the same configuration as in Example 2 was prepared except for using only _26.4 Te _56.6, and the reflectance at a wavelength of 410 nm was measured in the same manner as in Example 1. 410n wavelength
m has a reflectance of 17.3% for the amorphous part and 35.
8% and the contrast was 18.5%.

When the values of the refractive index and the extinction coefficient of the recording layer were measured in the same manner as in Example 1, the refractive index of the amorphous portion was 2.73, the extinction coefficient was 2.71, and the value of the crystalline portion was 2.71. The refractive index is 1.
80 and the extinction coefficient was 3.33.

Example 7 The composition of the recording layer was Ge _17.1 Sb
An optical recording medium having the same configuration as in Example 1 was prepared except for using only _26.4 Te _56.6, and the reflectance at a wavelength of 430 nm was measured in the same manner as in Example 1. Wavelength 430n
The reflectance at m is 9.1% for the amorphous part and 22.9 for the crystalline part.
% And contrast were 13.8%.

When the values of the refractive index and the extinction coefficient of the recording layer were measured in the same manner as in Example 1, the refractive index of the amorphous part was 2.95, the extinction coefficient was 2.73, and the value of the crystalline part was 2.73. The refractive index is 2.
02, the extinction coefficient was 3.46.

Example 8 The composition of the recording layer was Ge _17.1 Sb
An optical recording medium having the same configuration as in Example 2 was prepared except for using only _26.4 Te _56.6, and the reflectance at a wavelength of 430 nm was measured in the same manner as in Example 1. Wavelength 430n
m has a reflectance of 15.7% for the amorphous part and 33.
The contrast was 57.8% and the contrast was 17.8%.

When the values of the refractive index and the extinction coefficient of the recording layer were measured in the same manner as in Example 1, the refractive index of the amorphous portion was 2.95, the extinction coefficient was 2.73, and the value of the crystalline portion was 2.73. The refractive index is 2.
02, the extinction coefficient was 3.46.

Example 9 The composition of the recording layer was Ge _18.8 Sb
An optical recording medium having the same configuration as in Example 1 was produced except for using only _25.7 Te _55.7, and the reflectance at a wavelength of 410 nm was measured in the same manner as in Example 1. 410n wavelength
m, the reflectance of the amorphous part is 11.6%, and that of the crystal part 25.m.
The contrast was 0% and the contrast was 13.4%.

When the values of the refractive index and the extinction coefficient of the recording layer were measured in the same manner as in Example 1, the refractive index of the amorphous portion was 2.70, the extinction coefficient was 2.77, and the value of the crystal portion was 2.77. The refractive index is 1.
86 and the extinction coefficient was 3.44.

Example 10 The composition of the recording layer was Ge _18.8 S
An optical recording medium having the same configuration as in Example 2 was prepared except for b _25.7 Te _55.7, and the reflectance at a wavelength of 410 nm was measured in the same manner as in Example 1. Wavelength 410
The reflectance at nm is 18.1% for the amorphous part and 3 for the crystalline part.
5.8% and contrast were 17.7%.

When the values of the refractive index and the extinction coefficient of the recording layer were measured in the same manner as in Example 1, the refractive index of the amorphous portion was 2.70, the extinction coefficient was 2.77, and the value of the crystalline portion was 2.77. The refractive index is 1.
86 and the extinction coefficient was 3.44.

Example 11 The composition of the recording layer was Ge _18.8 S
An optical recording medium having the same configuration as in Example 1 was prepared except for b _25.7 Te _55.7, and the reflectance at a wavelength of 430 nm was measured in the same manner as in Example 1. Wavelength 430
The reflectivity in nm is 9.5% for the amorphous part and 22.
The contrast was 9% and the contrast was 13.4%.

When the values of the refractive index and the extinction coefficient of the recording layer were measured in the same manner as in Example 1, the refractive index of the amorphous portion was 2.93, the extinction coefficient was 2.79, and the value of the crystalline portion was 2.79. The refractive index is 2.
07 and the extinction coefficient were 3.58.

Example 12 The composition of the recording layer was Ge _18.8 S
An optical recording medium having the same configuration as in Example 2 was produced except for b _25.7 Te _55.7 except that the reflectance at a wavelength of 430 nm was measured in the same manner as in Example 1. Wavelength 430
The reflectivity at nm is 16.4% for the amorphous part and 3 for the crystalline part.
The contrast was 3.6% and the contrast was 17.2%.

When the values of the refractive index and the extinction coefficient of the recording layer were measured in the same manner as in Example 1, the refractive index of the amorphous portion was 2.93, the extinction coefficient was 2.79, and the value of the crystalline portion was 2.79. The refractive index is 2.
07 and the extinction coefficient were 3.58.

(Example 13) The composition of the recording layer was Ge _18.3 S
An optical recording medium having the same configuration as in Example 1 was prepared except for b _27.3 Te _54.4, and the reflectance at a wavelength of 410 nm was measured in the same manner as in Example 1. Wavelength 410
The reflectance at nm is 12.9% for the amorphous part and 2 for the crystalline part.
The contrast was 6.3% and the contrast was 13.4%.

When the values of the refractive index and the extinction coefficient of the recording layer were measured in the same manner as in Example 1, the refractive index of the amorphous portion was 2.59, the extinction coefficient was 2.86, and the value of the crystalline portion was 2.86. The refractive index is 1.
78 and the extinction coefficient were 3.43.

Example 14 The composition of the recording layer was Ge _18.3 S
An optical recording medium having the same configuration as that of Example 2 was prepared except for b _27.3 Te _54.4 except for that, and the reflectance at a wavelength of 410 nm was measured as in Example 1. Wavelength 410
The reflectance in nm is 20.2% for the amorphous part and 3% for the crystalline part.
The contrast was 7.0% and the contrast was 16.8%.

When the values of the refractive index and the extinction coefficient of the recording layer were measured in the same manner as in Example 1, the refractive index of the amorphous portion was 2.59, the extinction coefficient was 2.86, and the value of the crystalline portion was 2.86. The refractive index is 1.
78 and the extinction coefficient were 3.43.

(Example 15) The composition of the recording layer was Ge _18.3 S
An optical recording medium having the same configuration as in Example 1 was prepared except for b _27.3 Te _54.4 except that the reflectance at a wavelength of 430 nm was measured in the same manner as in Example 1. Wavelength 430
The reflectance at nm is 10.8% for the amorphous part and 2% for the crystalline part.
3.8% and contrast were 13%.

When the values of the refractive index and the extinction coefficient of the recording layer were measured in the same manner as in Example 1, the refractive index of the amorphous portion was 2.81, the extinction coefficient was 2.90, and the value of the crystalline portion was 2.90. The refractive index is 2.
01, the extinction coefficient was 3.43.

Example 16 The composition of the recording layer was Ge _18.3 S
An optical recording medium having the same configuration as in Example 2 was produced except for b _27.3 Te _54.4 except that the reflectance at a wavelength of 430 nm was measured in the same manner as in Example 1. Wavelength 430
The reflectance at nm is 18.4% for the amorphous part and 3 for the crystalline part.
The contrast was 4.5% and the contrast was 16.1%.

When the values of the refractive index and the extinction coefficient of the recording layer were measured in the same manner as in Example 1, the refractive index of the amorphous portion was 2.81, the extinction coefficient was 2.90, and the value of the crystalline portion was 2.90. The refractive index is 2.
01, the extinction coefficient was 3.43.

Example 17 The composition of the recording layer was Ge _22.0 S
An optical recording medium having the same configuration as in Example 1 was prepared except for b _22.3 Te _55.7, and the reflectance at a wavelength of 410 nm was measured in the same manner as in Example 1. Wavelength 410
The reflectance at nm is 10.7% for the amorphous part and 2% for the crystalline part.
The contrast was 5.0% and the contrast was 14.3%.

When the values of the refractive index and the extinction coefficient of the recording layer were measured in the same manner as in Example 1, the refractive index of the amorphous portion was 2.81, the extinction coefficient was 2.84, and the value of the crystalline portion was 2.84. The refractive index is 1.
85 and the extinction coefficient was 3.41.

Example 18 The composition of the recording layer was Ge _22.0 S
An optical recording medium having the same configuration as in Example 2 was prepared except for b _22.3 Te _55.7, and the reflectance at a wavelength of 410 nm was measured in the same manner as in Example 1. Wavelength 410
The reflectance in nm is 20.2% for the amorphous part and 3% for the crystalline part.
The contrast was 7.0% and the contrast was 16.8%.

When the values of the refractive index and the extinction coefficient of the recording layer were measured in the same manner as in Example 1, the refractive index of the amorphous portion was 2.81, the extinction coefficient was 2.84, and the value of the crystalline portion was 2.84. The refractive index is 1.
85 and the extinction coefficient was 3.41.

(Example 19) The composition of the recording layer was Ge _22.0 S
An optical recording medium having the same configuration as in Example 1 was produced except for b _22.3 Te _55.7, and the reflectance at a wavelength of 430 nm was measured in the same manner as in Example 1. Wavelength 430
The reflectance at nm is 8.9% for the amorphous part and 22.
The contrast was 9% and the contrast was 14%.

When the values of the refractive index and the extinction coefficient of the recording layer were measured in the same manner as in Example 1, the refractive index of the amorphous portion was 3.07, the extinction coefficient was 2.84, and the value of the crystalline portion was 2.84. The refractive index is 2.
06, and the extinction coefficient was 3.54.

(Example 20) The composition of the recording layer was Ge _22.0 S
An optical recording medium having the same configuration as in Example 2 was prepared except for b _22.3 Te _55.7, and the reflectance at a wavelength of 430 nm was measured in the same manner as in Example 1. Wavelength 430
The reflectivity at nm is 15.3% for the amorphous part and 3 for the crystalline part.
The contrast was 3.5% and the contrast was 18.2%.

When the values of the refractive index and the extinction coefficient of the recording layer were measured in the same manner as in Example 1, the refractive index of the amorphous part was 3.07, the extinction coefficient was 2.84, and the value of the crystal part was 2.8. The refractive index is 2.
06, and the extinction coefficient was 3.54.

(Comparative Example 1) The thickness of the first dielectric layer was 160
nm, the thickness of the recording layer is 5 nm, and the thickness of the second dielectric layer is 3
An optical recording medium having the same configuration as in Example 1 was produced except that the thickness was set to 5 nm, and the same measurement as in Example 1 was performed. Wavelength 410
The reflectance at nm is 7.5% for the amorphous portion and 12.1 for the crystalline portion.
The reflectance was 6% and the contrast was about 5%. The reflectance of the amorphous portion and the crystalline portion was low, and the contrast was very low.

(Comparative Example 2) The thickness of the first dielectric layer was set to 100
nm, the thickness of the recording layer is 5 nm, and the thickness of the second dielectric layer is 3
An optical recording medium having the same configuration as in Example 1 was produced except that the thickness was set to 5 nm, and the same measurement as in Example 1 was performed. Wavelength 410
The reflectance at nm is 15.6% for the amorphous part and 1 for the crystalline part.
3.9%, and the reflectances of the amorphous part and the crystal part were reversed, and no contrast was obtained.

Comparative Example 3 An optical recording medium having the same configuration as that of Comparative Example 1 was manufactured, and the reflectance at a wavelength of 430 nm was measured in the same manner as in Example 1. The reflectance at a wavelength of 430 nm was 12.2% for the amorphous part, 18.3% for the crystal part, and about 6.2% for the contrast, and the contrast was extremely small.

Comparative Example 4 An optical recording medium having the same structure as in Comparative Example 2 was manufactured, and the reflectance at a wavelength of 430 nm was measured in the same manner as in Example 1. The reflectance at a wavelength of 430 nm is 11.7% for an amorphous part and 8.4% for a crystal part.
The reflectances of the amorphous part and the crystalline part were reversed, and no contrast was obtained.

[0087]

According to the optical recording medium of the present invention, the following effects can be obtained. (1) A large difference in reflectance between crystal and amorphous is obtained in a short wavelength region of 450 nm or less. (2) A wide selection of the thickness of the dielectric layer is possible. (3) It can be easily manufactured by a sputtering method.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI G11B 7/24 538 G11B 7/24 538C

Claims (8)

[Claims] 1. An optical recording medium in which information is recorded and erased by a phase change between an amorphous phase and a crystalline phase due to light irradiation, wherein at least a first dielectric layer / recording layer / second A dielectric layer / reflection layer is stacked in this order, and the refractive index, extinction coefficient, and layer thickness of each layer at a wavelength of 390 nm to 450 nm are represented by the following formula. Optical recording medium. _{2.2 ≦ n a ≦ 2.3 30 ≦} d a ≦ 500 2.58 ≦ nα ≦ 3.3 2.6 ≦ kα ≦ 2.9 1.77 ≦ n c ≦ 2.5 3.2 ≦ k c ≦ 3.8 7 ≦ d _r ≦ 35 (nm) 2.25 ≦ n _b ≦ 2.4 0 <d _b ≦ 25 (nm) 0.4 ≦ nβ ≦ 0.6 3.8 ≦ kβ ≦ 4.25 here, n _a is the refractive index of the first dielectric layer, d _a is the thickness of the first dielectric layer (nm), n [alpha is the refractive index of the amorphous state of the recording layer,
kα is the extinction coefficient of the amorphous state of the recording layer, n _c is the refractive index of the crystalline state of the recording layer, k _c is the extinction coefficient of the crystalline state of the recording layer,
d _r is the thickness of the recording layer (nm), n _b is the refractive index of the second dielectric layer, d _b is the thickness of the second dielectric layer (nm), nβ is the refractive index of the reflective layer, Keibeta reflection Indicates the extinction coefficient of the layer. 2. The optical recording medium according to claim 1, wherein the refractive index, extinction coefficient, and layer thickness of each layer at a wavelength of 390 nm to 425 nm are represented by the following equations. _{2.2 ≦ n a ≦ 2.3 80a +} 100 ≦ d a ≦ 80a + 150 (nm) ( a represents an integer including 0) 2.58 ≦ nα ≦ 3.3 2.64 ≦ kα ≦ 2.9 1.77 ≦ n _c ≦ 2.2 3.2 ≦ k _c ≦ 3.7 7 ≦ d _r ≦ 35 (nm) 2.3 ≦ n _b ≦ 2.4 0 <d _b ≦ 15 (nm) 0.4 ≦ nβ ≦ 0 here .52 3.8 ≦ kβ ≦ 4.1, n a is the refractive index of the first dielectric layer, d _a is the thickness of the first dielectric layer (nm), n [alpha is the amorphous state of the recording layer Refractive index,
kα is the extinction coefficient of the amorphous state of the recording layer, n _c is the refractive index of the crystalline state of the recording layer, k _c is the extinction coefficient of the crystalline state of the recording layer,
d _r is the thickness of the recording layer (nm), n _b is the refractive index of the second dielectric layer, d _b is the thickness of the second dielectric layer (nm), nβ is the refractive index of the reflective layer, Keibeta reflection Indicates the extinction coefficient of the layer. 3. The optical recording medium according to claim 1, wherein the refractive index, extinction coefficient, and layer thickness of each layer at a wavelength of 390 nm to 425 nm are represented by the following equations. _{2.2 ≦ n a ≦ 2.3 100a +} 30 ≦ d a ≦ 100a + 80 (nm) ( a represents an integer including 0) 2.58 ≦ nα ≦ 3.3 2.64 ≦ kα ≦ 2.9 1.77 ≦ n _c ≦ 2.2 3.2 ≦ k _c ≦ 3.7 7 ≦ d _r ≦ 35 (nm) 2.3 ≦ n _b ≦ 2.4 15 <d _b ≦ 25 (nm) 0.4 ≦ nβ ≦ 0 here .52 3.8 ≦ kβ ≦ 4.1, n a is the refractive index of the first dielectric layer, d _a is the thickness of the first dielectric layer (nm), n [alpha is the amorphous state of the recording layer Refractive index,
kα is the extinction coefficient of the amorphous state of the recording layer, n _c is the refractive index of the crystalline state of the recording layer, k _c is the extinction coefficient of the crystalline state of the recording layer,
d _r is the thickness of the recording layer (nm), n _b is the refractive index of the second dielectric layer, d _b is the thickness of the second dielectric layer (nm), nβ is the refractive index of the reflective layer, Keibeta reflection Indicates the extinction coefficient of the layer. 4. Each layer has a wavelength of 450 n exceeding 425 nm.
2. The optical recording medium according to claim 1, wherein the refractive index, the extinction coefficient, and the layer thickness at m or less have a relationship represented by the following equation. _{2.2 ≦ n a ≦ 2.25 80a +} 30 ≦ d a ≦ 80a + 70 (nm) ( a represents an integer including 0) 2.8 ≦ nα ≦ 3.3 2.64 ≦ kα ≦ 2.9 1.85 ≦ n _c ≦ 2.2 3.2 ≦ k _c ≦ 3.7 7 ≦ d _r ≦ 35 (nm) 2.25 ≦ n _b ≦ 2.3 0 <d _b ≦ 15 (nm) 0.5 ≦ nβ ≦ 0 here .6 4.0 ≦ kβ ≦ 4.25, n a is the refractive index of the first dielectric layer, d _a is the thickness of the first dielectric layer (nm), n [alpha is the amorphous state of the recording layer Refractive index,
kα is the extinction coefficient of the amorphous state of the recording layer, n _c is the refractive index of the crystalline state of the recording layer, k _c is the extinction coefficient of the crystalline state of the recording layer,
d _r is the thickness of the recording layer (nm), n ^b is the refractive index of the second dielectric layer, d _b is the thickness of the second dielectric layer (nm), nβ is the refractive index of the reflective layer, Keibeta reflection Indicates the extinction coefficient of the layer. 5. The wavelength of each layer is larger than 425 nm and 450
2. The optical recording medium according to claim 1, wherein the refractive index, the extinction coefficient, and the thickness of the layer at nm or less have a relationship represented by the following equation. 2.2 ≦ n _a ≦ 2.25 100a + 50 ≦ d _a ≦ 100a + 110 (nm) (a
Integer) 2.8 ≦ nα ≦ 3.3 2.64 ≦ kα ≦ 2.9 1.85 ≦ n c ≦ 2.2 3.2 ≦ k c ≦ 3.7 7 ≦ d r ≦ 35 comprising 0 _{(nm) 2.25 ≦ n b ≦} 2.3 15 <d b ≦ 25 (nm) 0.5 ≦ nβ ≦ 0.6 4.0 ≦ kβ ≦ 4.25 where, n _a first dielectric refractive index of the layer, d _a is the thickness of the first dielectric layer (nm), n [alpha is the refractive index of the amorphous state of the recording layer,
kα is the extinction coefficient of the amorphous state of the recording layer, n _c is the refractive index of the crystalline state of the recording layer, k _c is the extinction coefficient of the crystalline state of the recording layer,
d _r is the thickness of the recording layer (nm), n _b is the refractive index of the second dielectric layer, d _b is the thickness of the second dielectric layer (nm), nβ is the refractive index of the reflective layer, Keibeta reflection Indicates the extinction coefficient of the layer. 6. The optical recording medium according to claim 1, wherein the first dielectric layer and the second dielectric layer contain at least ZnS and SiO ₂ . 7. The recording layer has a composition of three elements of Ge, Sb and Te or three elements of Ge, Sb and Te and Pd, Nb and P
The optical recording medium according to any one of claims 1 to 5, comprising at least one selected from t, Au, Ag, and Ni. 8. The optical recording medium according to claim 1, wherein the reflection layer is made of Al or an Al alloy.