JPH1064128A - Optical recording medium and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical recording medium at a low cost. SOLUTION: This optical recording medium is an optical recording medium to which the recording, erasing and reproducing of information are made possible by irradiating the recording layer formed on a substrate with light and the recording and erasing of the information are executed by a phase change between an amorphous phase and a crystalline phase. The recording layer is formed as the crystalline phase. The process for producing such optical recording medium is executed by keeping the substrate temp. at >=70 deg.C and forming the recording layer by sputtering at the time of producing the optical recording medium with which the recording, erasing and reproducing of the information are made possible by irradiating the recording layer formed on the substrate with the light and the recording and erasing of the information are executed by the phase change between the amorphous phase and the crystalline phase. As a result, the stage for heating and crystallizing the recording layer by a laser, etc., after the film forming stage is eliminated and the production of the phase change recording medium is executed at a low cost.

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 provides a method for erasing recorded information,
The present invention relates to a rewritable phase-change optical recording medium such as an optical disk having a rewritable function and capable of recording an information signal at high speed and at high density.

[0002]

2. Description of the Related Art The technology of a conventional rewritable phase-change optical recording medium is as follows. A method is known in which after a recording film is formed, it is heated by an Ar laser, a semiconductor laser, a halogen lamp, or the like to be crystallized (JP-A-2-5246).

[0003]

An object of the above-mentioned conventional rewritable phase-change optical recording medium having a quenching structure is that the recording film is heated and crystallized after its formation, so that the production cost is high. Therefore, if the recording film is formed in a crystalline state, a heating crystallization process after the formation becomes unnecessary, and the cost can be reduced.

An object of the present invention is to solve the problems of the conventional optical recording medium and to provide a low-cost optical recording medium and a method for manufacturing the same.

[0005]

The present invention employs the following means to solve the above-mentioned problems. That is, the optical recording medium of the present invention can record, erase, and reproduce information by irradiating a recording layer formed on a substrate with light, and can record and erase information in an amorphous phase and a crystalline phase. Wherein the recording layer is formed as a crystalline phase. In the method for manufacturing such an optical recording medium, information can be recorded, erased, and reproduced by irradiating a recording layer formed on a substrate with light, and information recording and erasing can be performed in an amorphous phase and a crystalline phase. When manufacturing an optical recording medium performed by a phase change between the recording layers, the recording layer is formed by sputtering at a substrate temperature of 70 ° C. or higher.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the optical recording medium of the present invention,
Laminating at least a first dielectric layer, a recording layer, a second dielectric layer, and a reflective layer on a substrate in this order ensures that the substrate, the recording layer, etc. are deformed by heat during recording and the recording characteristics are degraded. This is preferable because it has an effect of protecting the substrate and the recording layer from heat, such as prevention, and an effect of improving the signal contrast at the time of reproduction by an optical interference effect.

As the first dielectric layer and the second dielectric layer of the present invention, there are inorganic thin films such as ZnS, SiO ₂ , silicon nitride, and aluminum oxide. In particular, a thin film of ZnS, S
a thin film of a metal oxide such as i, Ge, Al, Ti, Zr, Ta, or Ce; a thin film of a nitride such as Si or Al;
A thin film of a carbide such as Zr and Hf and a film of a mixture of these compounds are preferable because of high heat resistance. Also,
A mixture of these and a fluoride such as MgF ₂ is also preferable because the residual stress of the film is small. Especially Z
A mixed film of nS and SiO ₂ or a mixed film of ZnS, SiO ₂ and carbon is preferable because ZnS and SiO ₂ hardly deteriorate even when recording and erasing are repeated, especially ZnS and SiO 2. A mixed film of ₂ and carbon is preferred. In a mixed film of ZnS and SiO ₂ , SiO ₂
Is preferably 15 to 35 mol%, and ZnS and Si
In a mixed film containing O ₂ and carbon as constituent materials, Si
The mixing ratio of O ₂ is preferably 15 to 35 mol%, and the mixing ratio of carbon is preferably 1 to 15 mol%.

The material of the reflection layer of the present invention includes metals such as Al and Au having light reflectivity, alloys containing these as a main component and containing additional elements such as Ti, Cr and Hf, and metals such as Al and Au. Examples thereof include a mixture of a metal with a metal compound such as a metal nitride such as Al and Si, a metal oxide, and a metal chalcogenide. Metals such as Al and Au and alloys containing these as main components are preferable because of high light reflectivity and high heat conductivity. As an example of the above alloy, Al, Si, Mg, Cu, Pd, T
at least one of i, Cr, Hf, Ta, Nb, Mn, etc.
A total of 5 atomic% or less and 1 atomic% or more of various kinds of elements, or Au, Cr, Ag, Cu, Pd, Pt,
There is a material in which at least one element such as Ni is added in a total amount of 20 atomic% or less and 1 atomic% or more. In particular, an alloy containing Al as a main component is preferable because the price of the material can be reduced, and in particular, Al has at least one selected from Ti, Cr, Ta, Hf, Zr, Mn, and Pd because of good corrosion resistance. 5 atomic% or less in total of one or more metals.
An alloy containing 5 atomic% or more is preferable. In particular, since the corrosion resistance is good and hillocks and the like are unlikely to occur, the reflective layer is made up of a total of 0.5 atomic% or more of the additive element.
Al-Hf-Pd alloy, Al-Hf alloy, Al-Ti alloy, Al-Ti-Hf alloy, Al-C containing less than atomic%
r alloy, Al-Ta alloy, Al-Ti-Cr alloy, Al
It is preferable to be composed of an alloy containing any of Al as a main component of a -Si-Mn alloy.

The recording layer of the present invention is not particularly limited, but may be a Pd-Ge-Sb-Te alloy, Nb-G
e-Sb-Te alloy, Pd-Nb-Ge-Sb-Te alloy, Pt-Ge-Sb-Te alloy, Ge-Sb-Te alloy, Co-Ge-Sb-Te alloy, In-Sb-Te alloy, Ag-In-Sb-Te alloy, In-Se alloy and the like are available. Because the record can be rewritten many times,
e-Sb-Te alloy, Pd-Ge-Sb-Te alloy, N
b-Ge-Sb-Te alloy, Pd-Nb-Ge-Sb-
Te alloys and Pt-Ge-Sb-Te alloys are preferred. In particular, Pd-Ge-Sb-Te alloy, Nb-Ge-Sb-
Te alloy, Pd-Nb-Ge-Sb-Te alloy, Pt-
Ge-Sb-Te alloys are preferable because they have a short erasing time, can be repeatedly recorded and erased many times, and have excellent recording characteristics such as C / N and erasing rate. Moreover,
The composition is more preferably in the range represented by the following formula, from the viewpoint of excellent thermal stability and repetition stability.

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, and platinum. In addition, 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 effects 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, and such transparent substrate materials include glass, polycarbonate, polymethyl methacrylate, Polyolefin resin, epoxy resin, polyimide resin and the like can be mentioned. In particular, a polycarbonate resin and an amorphous polyolefin resin are preferable because they have low optical birefringence, low hygroscopicity, and are easy to mold.

Although the thickness of the substrate is not particularly limited, it is practically 0.01 mm to 5 mm. 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. In addition, these substrates may be formed into an air sandwich structure, an air incident structure, or a close bonding structure by using two substrates after forming a recording layer or the like. The light source used for recording on the optical recording medium of the present invention is a high-intensity light source such as a laser beam or a strobe light. In particular, a semiconductor laser beam has a small light source, low power consumption, and easy modulation. It is preferable because of its existence.

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.

Further, at the time of forming a recording mark, the light intensity is high,
One-beam overwriting, in which erasing is slightly weakened and rewriting is performed by one light beam irradiation, is preferable because the time required for rewriting is reduced.

The crystal phase of the recording layer is preferably a rhombohedral system or a face-centered cubic system. It is preferable to use a rhomboid symmetrical system because the reflectance is high, the contrast is large, and an optical recording medium having a large signal intensity can be manufactured. A face-centered cubic crystal phase is preferable because it can be produced at a low substrate heating temperature.

Next, a method for manufacturing the optical recording medium of the present invention will be described. That is, by irradiating a recording layer formed on a substrate with light, information can be recorded / erased / reproduced, and information recording / erasing can be performed by a phase change between an amorphous phase and a crystalline phase. In producing a medium, as a method of forming a reflective layer, a recording layer, a dielectric layer, and the like on a substrate, a method of forming a thin film in a vacuum, for example, a vacuum deposition method, an ion plating method, a sputtering method, etc. . For the recording layer, the sputtering method is preferable because the composition and the film thickness can be easily controlled at the time of film formation. When the recording layer is formed by sputtering, a crystalline thin film can be deposited.
The film is preferably formed at 0 ° C. or higher. Preferably, since the deposition rate of the crystalline thin film can be increased, the recording layer is preferably formed by sputtering at a substrate temperature of 90 ° C. or higher. More preferably, the substrate temperature is preferably set to 110 ° C. or higher because the film formation rate can be further increased and other sputtering conditions can be widened.

The thickness of the recording layer and the like to be formed can be easily controlled by monitoring the deposition state using 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. The substrate is preferably rotated on its own because of excellent in-plane uniformity of the film thickness, and more preferably combined with revolution.

Further, after forming a reflective layer and the like within a range that does not significantly impair the effects of the present invention, a dielectric layer such as ZnS or SiO ₂ or a resin protection such as an ultraviolet curable resin is used to prevent scratches and deformation. Layers and the like may be provided as necessary. After the formation of the reflection 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.

[0020]

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

(Analysis and Measurement Method) The composition of the reflective layer and the recording layer was determined by ICP emission spectrometry (SPS manufactured by Seiko Denshi Kogyo KK).
4000). The carrier-to-noise ratio and the erasing rate (difference in the reproduced carrier signal strength after recording and after erasing) were measured by a spectrum analyzer.

The X-ray diffraction measurement of the recording layer was performed using Rigaku Denki's R
This was performed using a U-200R, 2155T, RINT type.

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 A recording layer, a dielectric layer, and a reflection layer were formed by magnetron sputtering on a polycarbonate substrate having a spiral groove having a thickness of 1.2 mm, a diameter of 12 cm, and a pitch of 1.2 μm.

First, the inside of the vacuum vessel is evacuated to 1 × 10 ^-5 Pa, and then, the Si is evacuated in an Ar gas atmosphere of 2 × 10 ^-1 Pa.
A first dielectric layer having a thickness of 150 nm was formed on the substrate by sputtering ZnS to which 20 mol% of O ₂ was added. next,
Pd, Nb, G while heating the substrate temperature to 100 ° C.
A target made of e, Sb, and Te is sputtered for 10 minutes, and Nb _0.006 Pd _0.001 Ge _0.173 Sb _0.26 Te
A recording layer having a thickness of 23 nm and a thickness of _0.56 was formed. Next,
Simultaneous sputtering of ZnS and C where the SiO ₂ was added 20 mol%, the molar mixing ratio of ZnS and C, 8: 1 so as to form the second dielectric layer having a film thickness of 37 nm, then Pd _0.001
A 70 nm-thick reflective layer of an Hf _0.02 Al _0.979 alloy was formed.

After the disk was taken out of the vacuum container, an acrylic UV-curable resin (SD-101, manufactured by Dainippon Ink Co., Ltd.) was spin-coated on the reflective layer and cured by UV irradiation to form a 4 μm thick film. A resin layer was formed to obtain an optical recording medium of the present invention.

The recording characteristics were measured on one of the discs thus manufactured, and the X-ray diffraction measurement of the recording layer was performed on another disc. In addition, any of these samples was used as a measurement sample without performing any heat treatment such as laser irradiation.

The recording characteristics were measured at a linear velocity of 12 m / s using an optical head having a numerical aperture of an objective lens of 0.47 and a wavelength of 790 nm of a semiconductor laser at a frequency of 8.8.
7MHz (duty 29%), peak power 8-16m
After recording once with a semiconductor laser beam modulated under the conditions of W and a bottom power of 4 to 9 mW, the semiconductor laser beam having a reproduction power of 1.0 mW was irradiated, and the C / N was measured under the condition of a bandwidth of 30 kHz. Furthermore, this part is 3.33MHz
(Duty 21%), irradiate a semiconductor laser beam modulated in the same manner as above, and perform one-beam overwriting. At this time, the erasure rate of the prerecorded signal of 8.87 MHz and the edge of the end of the reproduced signal of the recording mark are obtained. Was measured. A practically sufficient C / N of 50 dB is obtained with a peak power of 10 mW, and a practically sufficient 20 d with a bottom power of 4 to 7 mW.
The erasure rate of B was obtained.

Further, under the conditions of a peak power of 12 mW, a bottom power of 6 mW, and a frequency of 8.87 MHz, one-beam overwriting was repeated 10,000 times, and the same measurement was performed. In each case, almost no deterioration was observed within 2 dB, and almost no increase in jitter was observed. Also, this optical recording medium is
After 1000 hours in an environment of 0 ° C. and 80% relative humidity,
Thereafter, when the recorded portion was reproduced, the change in C / N was less than 2 dB and hardly changed. Further, recording and erasing were performed again, and the C / N and the erasing rate were measured.

The X-ray diffraction measurement of the recording layer was performed as follows. When peeled off at the interface between the second dielectric layer and the recording layer and the X-ray diffraction pattern was measured, the strongest peak was 2q = 2q = 3.01 Å, which corresponds to the interplanar spacing.
29.6 °, and the second strongest peak was the interplanar spacing of 2.1.
At 2q = 42.6 ° corresponding to 2 Å, the third strongest peak was at 2q = 25.7 ° corresponding to the interplanar spacing of 3.46 Å. This indicates that the recording layer has a face-centered cubic crystal phase.

Example 2 The second dielectric layer of Example 1 was simultaneously sputtered with ZnS and C to which 20 mol% of SiO ₂ was added, and the molar mixture ratio of ZnS, SiO ₂ and C was 8: 2: 1.2. A disk was manufactured in the same manner as in Example 1, except that the disk was manufactured as follows. As a result of measuring the recording characteristics in the same manner as in Example 1, the peak power was 10
At mW, a practically sufficient C / N of 50 dB was obtained, and at a bottom power of 4 to 7 mW, a practically sufficient erasing rate of 20 dB was obtained.

Further, under the conditions of a peak power of 12 mW, a bottom power of 6 mW, and a frequency of 8.65 MHz, one-beam overwriting was repeated 10,000 times, and the same measurement was performed. In each case, almost no deterioration was observed within 2 dB, and almost no increase in jitter was observed.

After the optical recording medium was placed in an environment of 80 ° C. and a relative humidity of 80% for 1000 hours, the recorded portion was reproduced thereafter, but the change in C / N was less than 2 dB and hardly changed. Further, recording and erasing are performed again, and C / N,
When the erasure rate was measured, almost no change was observed. Almost the same good recording and erasing characteristics were obtained.

Example 3 A polycarbonate substrate with a spiral groove having a thickness of 0.6 mm, a diameter of 12 cm, and a pitch of 1.48 μm (land width 0.74 μm, groove width 0.74 μm) was placed on a substrate.
A recording layer, a dielectric layer, and a reflection layer were formed by magnetron sputtering.

First, the inside of the vacuum vessel was evacuated to 6.5 × 10 ^-4 Pa, and then the pressure was reduced in an Ar gas atmosphere of 2 × 10 ^-1 Pa.
ZnS to which 20 mol% of iO ₂ was added was sputtered to form a first dielectric layer having a thickness of 85 nm on the substrate. next,
Ge, Sb, Te while heating the substrate temperature to 115 ° C.
Sputtering a target consisting of
A recording layer of _0.17 Sb _0.264 Te _{0.566 having} a thickness of 20 nm was formed. Next, Z containing 20 mol% of SiO ₂ was added.
nS is sputtered to form a second dielectric layer having a thickness of 10 nm, and then a Pd _0.001 Hf _0.02 Al _0.979 alloy having a thickness of 100 nm is formed.
A reflective layer having a thickness of nm was formed by sputtering.

After the disk was taken out of the vacuum container, an acrylic UV-curable resin (SD-101, manufactured by Dainippon Ink Co., Ltd.) was spin-coated on the reflective layer and cured by UV irradiation to form a film having a thickness of 4 μm. A resin layer was formed to obtain an optical recording medium of the present invention.

When the reflectivity of this optical recording medium was measured from the substrate side, the result was about 23% at 680 nm, which was equivalent to the reflectivity of a disk initialized by heating with a conventional laser.

The recording characteristics of one of the discs thus manufactured were measured. In addition, any of these samples was used as a measurement sample without performing any heat treatment such as laser irradiation.

The recording characteristics were measured at a linear velocity of 6 m / sec by using an optical head having a numerical aperture of an objective lens of 0.6 and a semiconductor laser having a wavelength of 680 nm.
The T pattern was recorded once by mark length recording. At this time, a multi-pulse was used as the recording laser waveform. Also,
The window width at this time was 34 ns. Thereafter, the semiconductor laser light having a reproduction power of 1.0 mW was irradiated, and the C / N was measured under the condition of a bandwidth of 30 kHz. Further, this portion is irradiated with a semiconductor laser beam modulated in the same manner as described above with a 13T signal, and one-beam overwriting is performed. At this time, the erasing rate of the 3T signal and the jitter of the edge at the end of the reproduction signal of the recording mark are measured. did. As a result, the peak power 1
At 0 mW, a practically sufficient C / N of 50 dB was obtained, and at a bottom power of 4 to 7 mW, a practically sufficient erasing rate of 20 dB was obtained. In addition, the jitter was 10% or less of the window width sufficient for practical use.

Further, the same measurement was performed after repeating the one-beam overwriting of the 3T signal 10,000 times under the conditions of the peak power of 12 mW and the bottom power of 6 mW, but the same measurement was performed. In each case, almost no change was observed within 2 dB, and almost no increase in jitter was observed. After the optical recording medium was placed in an environment of 80 ° C. and a relative humidity of 80% for 1000 hours, the recorded portion was reproduced thereafter, but the change in C / N was less than 2 dB and hardly changed. Further, recording and erasing are performed again, and C / N
When the erasure rate was measured, almost no change was observed.

Example 4 A disk was produced in the same manner as in Example 1 except that a glass substrate was used as the substrate material in Example 1 and the substrate temperature when producing the recording film was 350 ° C. As a result of measuring recording characteristics in the same manner as in Example 1, a practically sufficient C / N of 50 dB was obtained at a peak power of 10 mW, and a bottom power of 4 to
At 7 mW, a practically sufficient erasure rate of 20 dB was obtained.

Further, under the conditions of a peak power of 12 mW, a bottom power of 6 mW, and a frequency of 8.65 MHz, one-beam overwriting was repeated 10,000 times, and the same measurement was performed. Every change is 2
Degradation was hardly observed without dB, and almost no increase in jitter was observed.

After the optical recording medium was placed in an environment of 80 ° C. and a relative humidity of 80% for 1000 hours, the recorded portion was reproduced thereafter, but the change in C / N was less than 2 dB and hardly changed. Further, recording and erasing were performed again, and the C / N and the erasing rate were measured. Almost the same good recording and erasing characteristics were obtained.

When the X-ray diffraction pattern of the recording layer was measured in the same manner as in Example 1, the peak having the highest intensity was 2q = 28.
At 6 °, the second strongest peak is at 2q = 42.7 °, corresponding to a spacing of 2.12 Å, and the third strongest peak is 2q = 25.9 °, corresponding to a spacing of 3.44 Å. Was in This indicates that the recording layer has a rhombohedral crystal phase.

Comparative Example 1 A disk was manufactured in the same manner as in Example 1 except that the substrate was not heated. When the recording characteristics were measured in the same manner as in Example 1, the reflectivity was low and focusing was difficult, and the measurement could not be performed.

When the recording layer was subjected to X-ray diffraction measurement, no diffraction peak was observed.

[0047]

According to the present invention, the step of heating the recording layer with a laser or the like after the film formation step to crystallize the recording layer becomes unnecessary, and the effect that the phase change recording medium can be manufactured at low cost is obtained. .

Claims (8)

[Claims] An information recording, erasing and reproducing operation can be performed by irradiating a recording layer formed on a substrate with light, and the information recording and erasing can be performed by a phase change between an amorphous phase and a crystalline phase. An optical recording medium according to claim 1, wherein the recording layer is formed as a crystalline phase. 2. The optical recording medium according to claim 1, wherein said recording layer contains at least Sb or Te. 3. The recording layer according to claim 1, wherein said recording layer comprises at least Ge, Sb and Te.
The optical recording medium according to claim 1, comprising: 4. The optical recording medium according to claim 2, wherein the crystal phase of the recording layer is a rhombohedral symmetric system. 5. A recording medium according to claim 2, wherein the crystal phase of said recording layer is face-centered cubic. 6. The recording, erasing, and reproducing of information is possible by irradiating a recording layer formed on a substrate with light, and the recording and erasing of information is performed by a phase change between an amorphous phase and a crystalline phase. A method for producing an optical recording medium, comprising: forming a recording layer by sputtering at a substrate temperature of 70 ° C. or higher when producing an optical recording medium. 7. The substrate according to claim 6, wherein said substrate temperature is 90 ° C. or higher.
The manufacturing method of the optical recording medium according to the above. 8. The method for manufacturing an optical recording medium according to claim 6, wherein said substrate temperature is 110 ° C. or higher.