JP2004291490A - Write-once optical information recording medium and method for manufacturing it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a write-once optical information recording medium using an inorganic recording material which is capable of corresponding to a high density mark edge recording, having a simpler constitution in comparison with a case where a phase change material is used, having a good storage stability in a long time in comparison with a case where an organic coloring matter is used. <P>SOLUTION: The write-once optical information recording medium (1) has a recording layer comprising a mixture of a metal carbide and a metal oxide and capable of optically changing by irradiating it with a light with a wave length of 600-800 nm and recording a signal and reading it out on a transparent base. In addition, it includes (2) the write-once optical information recording medium described in (1) having a dielectric layer adjoining the recording layer, (3) the write-once optical information recording medium described in (1) or (2) wherein the metal is at least one selected from Si, Ti, Ta, Zr, V and W, and (4) the optical information recording medium described in either one of (1)-(3) wherein a light transmittance of the recording layer is 20-70%, and a refractive index n is ≥2.0. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a write-once optical information recording medium composed of an inorganic material that does not cause environmental degradation during recording and non-recording.
[0002]
[Prior art]
In recent years, optical recording media have been frequently used as storage for video, music, or computers. In particular, there are CD-R / RW, DVD-R / RW, DVD + R / RW, and the like. Optical discs have come into widespread use because they are easy to make, the manufacturing process is stable, and they have good compatibility with CD-ROMs and DVD-ROMs. Among these recordable optical recording media, write-once recording media are most widely used because of their simple processes and low manufacturing costs, and their good tampering prevention when used. . As for the CD-R, DVD-R and DVD + R, recording is mainly performed by a method of thermally coloring a recording layer using an organic dye.
The type using an organic dye generally has a configuration in which a recording layer (light absorbing layer) made of an organic dye or the like is provided on a substrate, and a reflective layer made of aluminum, gold, silver, or the like is further provided thereon. . By irradiating a laser beam as external energy, the recording layer is deformed or denatured to change optical characteristics and record information. Then, information is optically reproduced using the difference in reflectance between the recorded portion and the unrecorded portion.
[0003]
On the other hand, there is an attempt to constitute this write-once type information optical recording medium using an inorganic material. The write-once optical recording method using inorganic materials has attracted attention because, as the recording density has increased from CD to DVD, mark edge recording has become more difficult with organic dyes than with phase change type inorganic materials. This is because it is considered that the controllability is poor, and it is difficult for the edge to be formed in a correct shape and sharply at the set position. (Patent Document 1)
A recent patent publication relating to this write-once type optical information recording medium using an inorganic material is based on a material configuration of a type that decomposes by reaction to generate a gas (Patent Document 2). (Patent Documents 3 to 5), particularly those having a functional layer for reaction (Patent Document 6), and those performing recording by deformation due to light irradiation (Patent Document 7). And a device that records by changing the optical characteristics of a phase change material (Patent Document 1).
[0004]
[Patent Document 1]
WO 99/30908 pamphlet, page 4, lines 18 to 26
[Patent Document 2]
JP-A-5-40959
[Patent Document 3]
JP-A-5-334720
[Patent Document 4]
JP-A-11-227334
[Patent Document 5]
WO 00/4536 pamphlet
[Patent Document 6]
JP-A-2002-117576
[Patent Document 7]
JP-A-2002-298431
[0005]
[Problems to be solved by the invention]
The present invention uses an inorganic recording material that can cope with high-density mark edge recording, has a simpler configuration than when a phase change material is used, and has a long-term storage property compared to a case where an organic dye is used. And a method of manufacturing the same.
[0006]
[Means for Solving the Problems]
The above object is achieved by the following inventions 1) to 10) (hereinafter, referred to as inventions 1 to 10).
1) Having a recording layer made of a mixture of a metal carbide and an oxide, which can be optically changed by irradiating light having a wavelength of 600 to 800 nm on a transparent substrate to record and read signals. A write-once optical information recording medium characterized by the above-mentioned.
2) The write-once optical information recording medium according to 1), further comprising a dielectric layer adjacent to the recording layer.
3) The write-once optical information recording medium according to 1) or 2), wherein the metal is at least one selected from Si, Ti, Ta, Zr, V, and W.
4) The write-once optical information recording medium according to any one of 1) to 3), wherein the recording layer has a light transmittance of 20 to 70% and a refractive index n of 2.0 or more.
5) It has two or more recording layers, and the recording layer on which light first enters has a light transmittance of 40 to 70% and a refractive index n of 2.0 or more. 1) 3. The write-once optical information recording medium according to any one of items 1 to 3,
6) The dielectric layer contains ZnS as a main component and TiO ₂ , SiO ₂ , ZrO ₂ The write-once optical information recording medium according to any one of 2) to 5), comprising a material containing at least one selected from the group consisting of:
7) The write-once optical information recording medium according to 6), wherein the ratio of ZnS in the dielectric layer is 60 to 95 mol%.
8) The method for manufacturing a write-once optical information recording medium according to any one of 1) to 7), wherein the recording layer is formed by RF sputtering using a mixture of a metal carbide and an oxide as a target.
9) The recording layer is formed by direct current or direct current sputtering having a pulsed voltage waveform using a mixture of a metal carbide and an oxide (specific resistance of 0.5 Ω · cm or less) as a target 1). 7. The method for manufacturing a write-once optical information recording medium according to any one of 7) to 7).
10) Targeting only a metal carbide or a mixture of a carbide and an oxide (provided that the specific resistance is 0.5 Ω · cm or less) by DC sputtering having a DC or pulsed voltage waveform in an oxygen-introduced atmosphere. The method for manufacturing a write-once optical information recording medium according to any one of 1) to 7), wherein a recording layer is formed.
[0007]
Hereinafter, the present invention will be described in detail.
The present inventors have studied a material that has a simple structure as compared with the case where a phase change material is used and can secure long-term storage characteristics, has high light absorption and a high melting point, and is stable. As such a material, a nitride or a carbide of each metal can be cited, but if only a nitride or a carbide is used, the melting point and the light absorption are high, but there is also conductivity, so when a predetermined energy is applied. It is considered that heat is diffused due to the conductivity, and is not effective in obtaining mark edge controllability which is the object of the present invention. Further, carbide is a material used also as a molding material for glass press lenses, and a dielectric material (SiO 2 containing a chalcogen component, which is commonly used in optical information recording media) is commonly used. ₂ , TiO ₂ Or a mixture containing glass such as ZnO) or an organic substrate having an oxygen atom. Therefore, as a result of exploring a recording material that has a light absorbing property and can reduce the conductivity, and further has an adhesive property with a dielectric glass and an organic material (assuming a transparent substrate and an environmental protection layer), as a result, metal carbides and oxides were found. The present inventors have found that a mixture of the above is preferable and have led to the present invention. When this mixture is used, light absorption can be ensured by the carbide, and the conductivity can be reduced and the adhesion to the dielectric or the organic material can be improved by mixing the oxide. Although light having a wide wavelength range can be used as light for recording and reading, it is preferably about 600 to 800 nm.
[0008]
Further, it is preferable to provide a dielectric layer adjacent to the recording layer in order to adjust the reflectivity and improve the dynamic range (reflectance difference between recording and non-recording).
Further, it is preferable to use at least one selected from Si, Ti, Ta, Zr, V, and W as the metal. These elements are excellent because the melting points of the respective carbides are extremely high (2810 to 3880 ° C.) and extremely stable at about room temperature.
The recording layer preferably has a light transmittance of 20 to 70% and a refractive index n of the mixture of 2.0 or more. If the light transmittance is less than 20%, the signal reflectivity that can be extracted is extremely low, and an error occurs in reading the difference in reflectivity. On the other hand, if it exceeds 70%, the irradiated light energy is not sufficiently absorbed by the recording layer and is transmitted therethrough, so that it is difficult to take out the difference in the reflectance of the recorded signal. Therefore, the above range of 20 to 70% is preferable as a range in which the reflectance difference can be effectively used on the balance between transmission and absorption. When the refractive index n of the recording layer is less than 2.0, the optical change upon irradiation with predetermined light energy becomes small as an absolute value, and it becomes difficult to obtain a signal amplitude. Since the light transmittance does not simply become the same only by the composition ratio of the carbide and the oxide, it is preferable to specify the light transmittance, that is, the light absorption ratio, instead of the composition ratio. It is also possible to manufacture a multilayer optical information recording medium having two or more recording layers. In this case, the light transmittance of the recording layer on which light is first incident is set to the depth side in the laser beam irradiation direction. Since the recording characteristics of the located recording layer are greatly affected, it is preferable to set the light transmittance of the recording layer on which light first enters to 40 to 70%.
The thickness of the recording layer is usually about 5 to 30 nm, preferably 10 to 20 nm.
[0009]
The dielectric layer is composed mainly of ZnS and TiO ₂ , SiO ₂ , ZrO ₂ It is preferable to use a material containing at least one selected from the group consisting of: Further, the ratio of ZnS in the dielectric layer is preferably set to 60 to 95 mol%. If it exceeds 95 mol%, the light transmittance at a wavelength of 405 nm, which is a blue-violet wavelength, becomes low, and the characteristics are almost the same as those of ZnS alone. If it is less than 60 mol%, the film formation rate and the refractive index n become too small, so that the production efficiency is lowered and the film thickness needs to be increased in order to obtain the same optical film thickness.
The thickness of the dielectric layer is usually about 30 to 200 nm for the lower dielectric layer (between the recording layer and the substrate) and about 10 to 20 nm for the upper dielectric layer.
As a method for forming the recording layer, a method in which a mixture of a metal carbide and an oxide is used as a target to form by a RF sputtering method, a mixture of a metal carbide and an oxide having a specific resistance of 0.5 Ω · cm or less, Or a method of forming a film by DC sputtering having a pulse-like voltage waveform, a target of a metal carbide or a mixture of a carbide and an oxide having a specific resistance of 0.5 Ω · cm or less, a DC or a pulse under an atmosphere in which oxygen is introduced. And a method of forming a film by direct current sputtering having a voltage waveform in a shape.
[0010]
【Example】
Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. For example, the same result can be obtained when the wavelength of the laser beam is not limited to 660 nm but is 780 nm or the like.
[0011]
Example 1
A write-once optical disc having the layer structure shown in FIG. 1 was produced as follows.
First, a recording layer 3 having a thickness of 20 nm was formed on a clean and transparent polycarbonate substrate 1 having a guide groove (thickness: 0.6 mm, track pitch: 0.74 μm, groove width: 0.37 μm, groove depth: 310 °). SiC and SiO ₂ Was formed.
Next, after applying an ultraviolet curable resin to the upper surface of the recording layer, the applied surface was irradiated with ultraviolet rays to form an environment-resistant protective layer 6 having a thickness of 4 μm.
Further, the same blank plate having a thickness of 0.6 mm was bonded using a UV adhesive to complete a disk having a thickness of 1.2 mm.
The recording layer is made of SiC and SiO ₂ And a partial pressure of Ar of 5 × 10 ^-3 Torr was introduced, oxygen was not introduced, and the film was formed by DC sputtering having a pulse-like voltage waveform with a duty of 80%. The composition of this target is SiC: SiO ₂ = 95: 5 (mol%), and the specific resistance was 5 mΩ · cm.
The refractive index n of the recording layer was 2.1 at a wavelength of 660 nm, and the light transmittance was 65% at a wavelength of 660 nm.
The recording layer of the manufactured optical disk was in an amorphous state.
The optical disk was rotated at a linear velocity of 3.5 m / sec, and the recording was performed by irradiating a laser beam having a wavelength of 660 nm, NA of 0.65, an irradiation power of 8 to 10 mW, a simple rectangular wave, and a pulse width of 20 to 25 nsec. An 8-16 modulation random signal having a mark length of 0.4 μm (a mark length about half that of the CD system) was recorded. The reflectance is 15% and the modulation is 60%.
The jitter when performing the random pattern recording was 8.3%, and no particular trouble occurred in both writing and reproducing. The power of the reproducing laser beam was 0.5 mW.
Next, the optical disk after the recording check was stored in a high-temperature and high-humidity bath at 80 ° C. and 85% RH for 400 hours, and the jitter was measured again. As a result, each change was 0.2% or less, which was not a problematic level. In addition, no floating of the film, no peeling of the film, and no occurrence of spot-like discoloration considered to be abnormal were observed.
[0012]
Example 2
A write-once optical disc having the layer structure shown in FIG. 2 was produced.
First, on a clean and transparent polycarbonate substrate 1 having a guide groove (thickness 0.6 mm, track pitch 0.74 μm, groove width 0.37 μm, groove depth 310 °), ZnS.SiO ₂ The dielectric layer 2 of [70:30 (mol%)] was formed by RF sputtering one by one under each condition in a range of 50 to 100 nm in increments of 10 nm.
Next, as the recording layer 3, ZrC and ZrO having a thickness of 20 nm were used. ₂ Was formed.
Next, after applying an ultraviolet curable resin to the upper surface of the recording layer, the applied surface was irradiated with ultraviolet rays to form an environment-resistant protective layer 6 having a thickness of 4 μm.
Further, the same blank plate having a thickness of 0.6 mm was bonded using a UV adhesive to complete a disk having a thickness of 1.2 mm.
The recording layer 3 is made of ZrC and ZrO ₂ Using a mixture target, Ar partial pressure is 5 × 10 ^-3 Torr was introduced, and the film was formed by DC sputtering having a pulsed voltage waveform with a duty of 80%. The composition of this target is 80 atomic% of ZrC, ZrO ₂ It was 20 atomic%, and the specific resistance was 6.5 mΩ · cm. The refractive index n of the completed recording layer was 2.5 at a wavelength of 660 nm. The light transmittance was 30% at a wavelength of 660 nm.
The recording layer of the manufactured optical disk was evaluated by X-ray diffraction of a single film of the separately manufactured recording layer, and as a result, it was in an amorphous state.
This optical disk was rotated at a linear velocity of 3.5 m / sec, and a laser beam having a wavelength of 660 nm, NA of 0.65, an irradiation power of 8 to 10 mW, a simple rectangular wave, and a pulse width of 20 to 25 nsec was recorded to perform recording. An 8-16 modulation random signal having a mark length of 0.4 μm (a mark length about half that of the CD system) was recorded. Reflectance is ZnS / SiO ₂ It changes depending on the thickness of the dielectric layer, and the bottom value becomes about 6% at 70 to 80 nm. It can be seen that the reflectance can be adjusted by the thickness of the dielectric layer like a phase change optical recording medium. Further, the modulation was maximized at the bottom value, and 73% was obtained. The change in the reflectance and the change in the modulation are shown in FIGS.
The jitter when performing the random pattern recording was 8.2%, and no particular trouble occurred in both writing and reproduction. The power of the reproducing laser beam was 0.5 mW.
Next, the optical disk after the recording check was stored in a high-temperature and high-humidity bath at 80 ° C. and 85% RH for 400 hours, and the jitter was measured again. In addition, no floating of the film, no peeling of the film, and no occurrence of spot-like discoloration considered to be abnormal were observed.
[0013]
Example 3
The following test was performed to study the recording principle of the optical information recording medium of the present invention.
In order to prevent thermal deformation, ZnS.SiO ₂ A dielectric layer having a thickness of 12 to 14 nm was formed.
Further, after applying an ultraviolet-curable resin to the upper surface, the applied surface was irradiated with ultraviolet rays to form an environment-resistant protective layer 6 having a thickness of 4 μm, thereby producing a single-plate disk having a thickness of 0.6 mm. Then, it was checked whether the thermal deformation caused by the laser irradiation caused the optical contrast or a change in other optical characteristics.
As a result, when the dielectric layer was laminated on the optical recording layer, the modulation was slightly increased. Therefore, the present inventors have determined that the principle of optical recording of the present invention is not thermal deformation. In addition, the recording principle has not been specified yet because it is not considered to be a material that causes a phase change. However, since the change in reflectance can be reliably read by irradiating a laser beam, photodarkening (atomic (Recording due to sequence change).
[0014]
Example 4 (Example in which the light transmittance of the recording layer on which light first enters is 40 to 70%)
Each layer of a lower dielectric layer (thickness: 80 nm), a recording layer (thickness: 10 nm), and an upper dielectric layer (thickness: 12 nm) was sequentially formed on a first substrate made of the polycarbonate resin substrate used in Example 1 by sputtering. Then, an optical disk having a layer configuration shown in FIG. 3 in which the recording layer was sandwiched between dielectric layers was manufactured (hereinafter, referred to as a first information layer). The dielectric layer is ZnS.SiO ₂ [80:20 (mol%)]. The recording layer is composed of 55 atomic% of TiC, TiO ₂ It was formed by RF sputtering without introducing oxygen using a target consisting of 45 atomic%. When measured separately, the light transmittance of the recording layer of the first information layer was 60% at a wavelength of 660 nm.
Next, a substrate similar to the first substrate is used as a second substrate, and a reflective layer (thickness: 100 nm), a dielectric layer (thickness: 12 nm), an optical recording layer (thickness: 12 nm), a dielectric layer (film) Each layer having a thickness of 100 nm was sequentially formed (hereinafter, referred to as a second information layer). ZnS.SiO for dielectric layer ₂ [80:20 (mol%)] The recording layer was formed by sputtering using a material having the same composition as that of the first information layer, and the reflective layer was formed using an Ag alloy having an Ag ratio of 95 atomic% or more.
Next, an ultraviolet curable resin is applied on the film surface of the first information layer, the second information layer surface side of the second substrate is bonded and spin-coated, and the ultraviolet curable resin is irradiated by irradiating ultraviolet light from the first substrate side. This was cured to form an intermediate layer, thereby producing a two-layer optical disk (two-layer write-once optical information recording medium) having two information layers. The thickness of the intermediate layer was 50 μm.
When the first information layer was evaluated at a wavelength of 660 nm in the same manner as in Examples 1 and 2 for each of the prepared optical discs, the reflectivity was improved by about 10% or more compared to Example 2, and 18 to 22%. Became. As for other characteristics, the modulation was 63% and the jitter when a random pattern was recorded was 8.3%, and no trouble occurred in both writing and reproduction. The power of the reproducing laser beam was 0.8 mW. Further, with respect to the second information layer, recording was performed using the same waveform pattern and evaluated, and the reflectance was 10 to 15%. As for other characteristics, the modulation was 60% and the jitter when a random pattern was recorded was 8.7%, and no trouble occurred in both writing and reproduction.
Next, the optical disk after the recording check was stored in a high-temperature and high-humidity bath at 80 ° C. and 85% RH for 400 hours, and the jitter was measured again. As a result, each change was 0.2% or less, which was not a problematic level. In addition, no floating of the film, no peeling of the film, and no occurrence of spot-like discoloration considered to be abnormal were observed.
[0015]
Example 5
95 atomic% of TiC, TiO ₂ Using a 5 atomic% target, oxygen was introduced at a flow rate of 2.5 sccm in addition to Ar gas (Ar partial pressure was 5 × 10 5 ^-3 Torr, oxygen partial pressure 5.2 × 10 ^-4 An optical disk was manufactured in the same manner as in Example 4, except that the recording layer was formed by performing Torr) sputtering. The specific resistance of the target having the above composition was 4.5 mΩ · cm.
The characteristics of the recording layer (mixed film of Ti carbide and oxide) formed as described above were almost the same as the characteristics of the recording layer formed in Example 4. That is, the refractive index n was 2.74 at a wavelength of 660 nm, and the value of n became higher, but the light transmittance was 59% at a wavelength of 660 nm, which was equivalent to that of Example 4.
When the first information layer was evaluated in the same manner as in Example 4, the reflectance was 18 to 22%, the modulation was 62%, and the jitter when a random pattern was recorded was 8.35%. No trouble occurred in either case. The power of the reproducing laser beam was 0.8 mW. Furthermore, no trouble occurred in both writing and reproduction in the second information layer as in Example 4.
The result of evaluating the storage characteristics in a high-temperature and high-humidity tank was the same as that in Example 4.
[0016]
Example 6
80 atomic% of TaC, Ta ₂ O ₅ Using a target consisting of 20 atomic%, introducing oxygen at a flow rate of 3.5 sccm in addition to Ar gas (Ar partial pressure is 4 × 10 ^-3 Torr, oxygen partial pressure 7.2 × 10 ^-4 An optical disk was manufactured in the same manner as in Example 4, except that the recording layer was formed by performing Torr) sputtering. The specific resistance of the target having the above composition was 0.51 mΩ · cm.
The characteristics of the recording layer (a mixed film of carbide and oxide of Ta) formed as described above were almost the same as the characteristics of the recording layer formed in Example 4. That is, the refractive index n was 2.3 at a wavelength of 660 nm, and the light transmittance was 61% at a wavelength of 660 nm, which was equivalent to that of Example 4.
When the first information layer was evaluated in the same manner as in Example 4, the reflectance was 18.5 to 22.5%, the modulation was 61.5%, and the jitter when a random pattern was recorded was 8.3%. No trouble occurred in both writing and reproduction. The power of the reproducing laser beam was 0.8 mW. Furthermore, no trouble occurred in both writing and reproduction in the second information layer as in Example 4.
The result of evaluating the storage characteristics in a high-temperature and high-humidity tank was the same as that in Example 4.
[0017]
Example 7
SiC and TiO as targets for the recording layer ₂ An optical disk was manufactured in the same manner as in Example 1 except that the mixture target of Example 1 was used. The composition of this target is SiC: TiO ₂ = 80: 20 (mol%), and the specific resistance was 7 mΩ · cm. Ar is used as a sputtering gas at a partial pressure of 5 × 10 ^-3 Torr was introduced, oxygen was not introduced, and the film was formed by DC sputtering having a pulse-like voltage waveform with a duty of 80%.
The refractive index n of the recording layer was 2.3 at a wavelength of 660 nm, and the light transmittance was 65% at a wavelength of 660 nm.
The recording layer of the manufactured optical disk was in an amorphous state.
The optical disk was rotated at a linear velocity of 3.5 m / sec, and the recording was performed by irradiating a laser beam having a wavelength of 660 nm, NA of 0.65, an irradiation power of 8 to 10 mW, a simple rectangular wave, and a pulse width of 20 to 25 nsec. An 8-16 modulation random signal having a mark length of 0.4 μm (a mark length about half that of the CD system) was recorded. The reflectance is 16% and the modulation is 60%.
The jitter when this random pattern recording was performed was 8.4%, and no particular trouble occurred in both writing and reproduction. The power of the reproducing laser beam was 0.5 mW.
Next, the optical disk after the recording check was stored in a high-temperature and high-humidity bath at 80 ° C. and 85% RH for 400 hours, and the jitter was measured again. As a result, each change was 0.2% or less, which was not a problematic level. In addition, no floating of the film, no peeling of the film, and no occurrence of spot-like discoloration considered to be abnormal were observed.
The target is SiC and ZrO. ₂ [SiC: ZrO ₂ = 80: 20 (mol%)], or SiC and Ta ₂ O ₅ [SiC: Ta ₂ O ₅ = 80: 20 (mol%)], almost the same results were obtained.
[0018]
Example 8
The material of the dielectric layer 2 is ZnS.SiO ₂ [70:30 (mol%)] to ZnS.TiO. ₂ A write-once optical disc was produced in the same manner as in Example 2 except that the amount was changed to [70:30 (mol%)]. ₂ Compared to TiO ₂ 4 has a higher refractive index, and thus the curves in FIGS. 4 and 5 are shifted to the left by 14 nm.
Similarly, ZnS.ZrO ₂ When [70:30 (mol%)] was used, the curves in FIGS. 4 and 5 were shifted to the left by 5 nm.
Next, the optical disk after the recording check was stored in a high-temperature and high-humidity bath at 80 ° C. and 85% RH for 400 hours, and the jitter was measured again. In addition, no floating of the film, no peeling of the film, and no occurrence of spot-like discoloration considered to be abnormal were observed.
[0019]
Comparative Example 1
An optical disk was manufactured in the same manner as in Example 1, except that the target for the recording layer was SiC alone. The resistivity of this target is SiC and SiO ₂ Was smaller than that of the mixture target of 2 mΩ · cm. Using this target, a recording layer was formed in the same manner as in Example 1. The characteristics of this recording layer were such that when the film thickness was 20 nm, the refractive index n was 2.5 at a wavelength of 660 nm. The light transmittance at this time was 55% at a wavelength of 660 nm.
Next, an optical disk having a thickness of 1.2 mm was completed in the same manner as in Example 1.
When this optical disc was evaluated using a laser having a wavelength of 660 nm, the jitter value was 12 to 20%, and a stable value was not obtained. Therefore, a test sample having the same structure as that of the optical disc was prepared again, recorded under the same conditions, disassembled, and observed with a scanning electron microscope. .
The reflectance of the optical disk subjected to the lamination / jitter evaluation was 18% and the modulation was 45%.
Further, when this optical disk was stored in a high-temperature and high-humidity bath at 80 ° C. and 85% RH for 400 hours, the recorded mark was inverted in reflectivity and the like. Did not.
[0020]
Comparative Example 2
An optical disk was prepared and evaluated in the same manner as in Example 1, except that a recording film of SiC alone was formed thickly so that the light transmittance was 18% (that is, less than 20%).
As a result, the reflectance was 22%, but the modulation was as low as 40%. When a storage test was performed in a high-temperature and high-humidity chamber in the same manner as in Comparative Example 1, not only a clear eye pattern could not be observed but also a level at which jitter could be measured, as in Comparative Example 1.
[0021]
Comparative Example 3
An optical disk was prepared and evaluated in the same manner as in Example 1, except that a recording film of SiC alone was formed so as to have a light transmittance of 77% (that is, a value exceeding 70%).
As a result, the reflectance was 22%, but the modulation was as low as 40%. When a storage test was performed in a high-temperature and high-humidity chamber in the same manner as in Comparative Example 1, not only a clear eye pattern could not be observed but also a level at which jitter could be measured, as in Comparative Example 1.
[0022]
【The invention's effect】
According to the present invention, an inorganic recording material that can support high-density mark edge recording, has a simpler configuration than when a phase change material is used, and has a long-term storage property as compared with a case where an organic dye is used. And a write-once optical information recording medium using the same. Further, by adjusting the reflectance, a multilayer optical information recording medium can be obtained.
Further, according to the present inventions 8 to 10, the write-once optical information recording medium of the present invention can be easily manufactured, and the ratio of carbide to oxide can be freely selected.
[Brief description of the drawings]
FIG. 1 is a diagram showing a cross section of a layer structure of an optical disc according to a first embodiment.
FIG. 2 is a diagram showing a cross section of the layer structure of the optical disc of Example 2 (a dielectric is present only on the substrate side).
FIG. 3 is a diagram illustrating a cross section of a layer structure of an optical disc of Example 4 (a diagram in which an optical recording layer is sandwiched between dielectrics).
FIG. 4 is a diagram showing a change in the reflectance of the optical disc of Example 2.
FIG. 5 is a diagram showing a change in modulation of the optical disc of the second embodiment.
[Explanation of symbols]
1 substrate
2 Lower dielectric layer
3. Recording layer composed of a mixture of carbide and oxide
4 Upper dielectric layer
5 Reflective layer
6 Environmental protection layer

Claims (10)

On a transparent substrate, it has a recording layer made of a mixture of a metal carbide and an oxide, which can be optically changed by irradiation with light having a wavelength of 600 to 800 nm to record and read signals. Write-once optical information recording medium. 2. The write-once optical information recording medium according to claim 1, further comprising a dielectric layer adjacent to the recording layer. 3. The write-once optical information recording medium according to claim 1, wherein the metal is at least one selected from Si, Ti, Ta, Zr, V, and W. 4. The write-once optical information recording medium according to claim 1, wherein the recording layer has a light transmittance of 20% to 70% and a refractive index n of 2.0 or more. 2. A recording layer having two or more recording layers, wherein the first recording layer on which light is first incident has a light transmittance of 40 to 70% and a refractive index n of 2.0 or more. 3. The write-once optical information recording medium according to any one of 3. Dielectric layer is mainly composed of _ZnS, TiO _2, SiO _2, write-once optical information recording according to that made of a material containing at least one selected from ZrO ₂ in any one of claims 2-5, wherein Medium. 7. The write-once optical information recording medium according to claim 6, wherein a ratio of ZnS in the dielectric layer is 60 to 95 mol%. 8. The method for manufacturing a write-once optical information recording medium according to claim 1, wherein the recording layer is formed by an RF sputtering method using a mixture of a metal carbide and an oxide as a target. The recording layer is formed by direct current or direct current sputtering having a pulsed voltage waveform using a mixture of a metal carbide and an oxide (specific resistance of 0.5 Ω · cm or less) as a target. 8. The method for manufacturing a write-once optical information recording medium according to any one of 7. The recording layer is formed by direct current sputtering having a DC or pulsed voltage waveform in an oxygen-introduced atmosphere, targeting only a metal carbide or a mixture of a carbide and an oxide (provided that the specific resistance is 0.5 Ω · cm or less). The method for manufacturing a write-once optical information recording medium according to claim 1, wherein a film is formed.

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