JPH0414635A - Information recording member - Google Patents

Abstract

PURPOSE:To prevent dimensional changes of the substrate surface due to recording laser beam and to prevent decrease in recording sensitivity by providing protective layers essentially comprising oxides, sulfides, carbides, serenides, nitrides, etc., in a multilayer structure adjacent to a recording thin film. CONSTITUTION:The first protective layer 3 is a thin film essentially comprising oxide, nitride, or carbide and has the thermal conductivity between >= 8 W/m.K and <= 60 W/m.K, and more preferably, >= 10 W/m.K and <= 50 W/m.K. The heat generated by irradiation of recording beam is diffused in the first protective layer 3 essentially comprising oxides, nitrides or carbides which have high thermal conductivity. The heat is then shielded by the second protective layer 2 essentially comprising oxides, serenides or sulfides having low thermal conductivity. Therefore, little heat reaches to the grooved resin 7, which prevents deformation or deterioration of the substrate.

Description

[Detailed description of the invention]

[Industrial Application Field 1] The present invention is applicable to FM-modulated analog signals such as video and audio using a recording energy beam such as a laser beam, digital data such as computer data, facsimile signals, and digital audio signals. information,
This invention relates to a thin film for recording information that can be recorded in real time. [Prior art] Known examples (patent publications or literature titles) There are various recording principles for recording on thin films with laser light, but there are various recording principles based on changes in atomic arrangement such as phase transition (also called phase change) of the film material and photodarkening. Since recording involves almost no change in the shape of the film, it has the advantage that a double-sided disc can be created by directly bonding two discs together using resin. A known example related to this type of record is, for example, Japanese Patent Application No. 60-226723.

[Problem to be solved by the invention]

Among the conventional technologies mentioned above, recording by phase change causes a change in atomic arrangement due to heat generated by recording beam irradiation, with almost no change in film shape. The heat transferred to the layers locally warms the substrate and deforms it, leading to increased noise and unstable tracking. An object of the present invention is to provide a recording member in which the shape of the substrate surface is not changed by the laser beam for recording, and the recording sensitivity is less likely to decrease.

[Means for Solving the Problems J] The above object is to provide an information recording member having an information recording thin film formed on a substrate that changes when irradiated with a recording beam. This can be achieved by providing multiple protective layers containing appropriate oxides, sulfides, carbides, selenides, or nitrides as main components. A preferred feature of the present invention is that in a recording medium having an information recording thin film formed on a substrate and which changes when irradiated with a recording beam, the information recording thin film is formed in the vicinity of the information recording thin film, or Adjacent to the information recording thin film, it is made of at least one material selected from the group consisting mainly of oxides, carbides, or nitrides with a thermal conductivity in the range of 8 W/m·K or more and 60 W/m·K or less, The first protective layer on the side closer to the information recording thin film and an oxide, sulfide, or selenide with a thermal conductivity of 0.5 W/m-K or more and 6 W/m-K (K is absolute temperature) or less. It has a second protective layer made of at least one material selected from the main ingredients. Furthermore, when the above-mentioned protective layer is made of two layers, the first protective layer on the side closer to the recording film is Al20□, Ta205.
Y2O3, Ta2O5, Si, N4. AQN,
S i C, and A Q S i N2, etc. (7)
A thin film whose main component is at least one material selected from Group A consisting of Al-Si-N-based materials and AN-Si-0-N-based materials is used as a second protective layer on the side far from the recording film. are SiO, SiO3, Ta2O5, TiO2, Zr
O, and ZnS. CdS, In2S3, ZnSe, CdSe and n2
A thin film whose main component is at least one material selected from Group B consisting of Se is used. More preferably, the first protective layer is Si3N4. AlS
i A material having a composition close to N2 or Al2o3 is used as the second protective layer. ZnS or a mixed material of ZnS and at least one of the oxides of group B is used. [Function] The thin film mainly composed of oxide, carbide, or nitride as the first protective layer is made of oxide, carbide, or nitride with high thermal conductivity.
Alternatively, it is a thin film mainly composed of nitride, which diffuses the heat generated in the recording film by irradiation with the recording beam and is strong against external forces, especially tensile forces. The thin film of the second protective layer whose main component is oxide, selenide, or sulfide is an oxide or selenide with low thermal conductivity. Alternatively, it is a thin film mainly composed of sulfide, which prevents the heat generated by the recording beam irradiation from being transmitted to the resin layer. Thereby, it is possible to prevent the resin from being altered or deformed due to the influence of the recording beam irradiation. The first protective layer, a thin film mainly composed of oxide, carbide, or nitride, has a thermal conductivity of 8 W/m.
The preferred range is K or more and 60 W/m° or less, and the film thickness is 1
The range is preferably from 0 nm to 11000 nm. especially,
If a thin film mainly composed of oxide or nitride with a thermal conductivity of 10 W/m·K or more and 50 W/m·K or less and a film thickness of about 50 nm or more and 200 nm or less is used, the decrease in recording sensitivity is small. Thermal diffusion coefficient is 2.3 cm”/sec or more6.
The thermal conductivity of the second protective layer is preferably 9 cm''/sec or less.
K is absolute temperature) or less, and the film thickness is preferably 10 nm.
A range of 11000n or less is preferable. In particular, the thermal conductivity is 2 W/m・K or more and 5 W/m・K or less, and the film thickness is about 50
When a thin film whose main component is oxide, selenide, or sulfide with a thickness of 300 nm or more is used, the effect of preventing deterioration or deformation caused by the above-mentioned recording beam irradiation is remarkable. Thermal diffusion coefficient is 0.46cm2/s
ee or more and 1.15 cm2/sec or less is preferable. The thickness of the recording film is preferably in the range from 20 nm to 250 nm in terms of recording sensitivity, S/N ratio, etc., and is preferably adjusted in conjunction with the thicknesses of the first protective layer and the second protective layer. The sum of the film thicknesses of the first protective layer and the second protective layer is 10 nm or more11
A range of 000n or less is preferable. The thickness of this protective layer is
In order to obtain a large reproduced signal by utilizing the interference effect of light,
It is preferable to adjust the thickness in accordance with the thickness of the recording film. Generally, when a thin film is irradiated with light, the reflected light is a superposition of reflected light from the surface of the thin film and light reflected from the rear surface of the thin film, causing interference. When reading a signal based on reflectance, it is preferable to adjust the thickness of each of the films described above to satisfy the condition that the reflectance value is small. This is because the contrast ratio at the time of signal reading becomes large and the recording sensitivity also becomes high. A particularly preferable total thickness range of the first protective layer and the second protective layer is 80 nm or more and 600 nm or less. The product of the refractive index and film thickness of the intermediate layer is 50 nm or more6
00nm or less, the product of the refractive index and film thickness of the recording film is 1100n
600 nm or less, and the total product of the refractive index and film thickness of the first protective layer and the second protective layer is 120 nm or more and 1500 nm
The following ranges are particularly preferred. However, regarding the recording film, it is sufficient that the product of the refractive index and the film thickness of at least a portion of the recording film is within the above range. It is preferable that the extinction coefficient k of the laser light used in the first protective layer and the second protective layer is 0.03 or more and 1.0 or less because the recording sensitivity is high. The first protective layer and the protective layer on the side opposite to the first protective layer and the second protective layer (the side opposite to the light incident side) (the layer between the recording film and the reflective layer if a reflective layer is provided) also have the first protective layer and the second protective layer. Materials with compositions similar to those used for the second protective layer can be used, and multiple layers can be similarly formed, but the extinction coefficient is 0.
Since it is preferably less than 1, for example, in the case of an oxide, it is better to reduce the number of oxygen defects. Further adjacent to the thin film mainly composed of oxides, sulfides and nitrides on the side opposite to the light incident side, there is further a layer of material or a metal layer that can be used for the first protective layer and the second protective layer. The strength will be further increased by providing . The thin film containing the oxide or the like of the present invention as a main component may be formed between the recording film and the substrate, or may be provided on the side of the recording film opposite to the substrate. It is more preferable to provide it on both sides. The substrate may be on the light incident side or on the opposite side. It is more preferable to provide an adhesion improving layer containing at least one element among W, Mo, and Cr as a main component between the protective layer on the side opposite to the light incident side of the recording film and the metal layer adjacent thereto. . The thickness of this layer is preferably 1 nm or more and 30 nm or less. Providing this layer is also effective for recording media other than the present invention. The interface between the first protective layer and the second protective layer does not necessarily have to be clear. If the composition changes continuously, there is no risk of peeling at the interface. Furthermore, the first protective layer and the second protective layer do not need to be uniform layers; for example, each of them may be a multilayer film with an average thermal conductivity, refractive index, and thermal diffusion coefficient within the above ranges. Good too. The present invention applies not only to disk-shaped recording media, but also to tape-shaped,
It is also effective for recording media such as cards. It is also effective for recording media based on other recording principles, such as magneto-optical recording films. [Example 1] Hereinafter, an example of the present invention will be described with reference to FIG. First, a substrate 1 (polycarbonate, diameter 13
0 mm, thickness 1.2 mm), a thin film 2 (approximately 200 nm) having a composition close to (z n s) so (S z 0z) 2° is laminated as the second protective layer of the present invention, and the first protective layer is Al20. as a layer. After laminating a thin film 3 (approximately 10,100 nm) made of an oxide with a composition close to A Sn-5b-Te yarn information recording thin film 4 (thickness approximately 30 nm) that causes an atomic arrangement change and an intermediate layer 5 (thickness approximately 200 nm) made of an oxide with a composition close to Al20. A thin film of Al2-Mg alloy (
After laminating a thin film 6 with a thickness of approximately 50 nm), a resin 7 that is cured by irradiation with ultraviolet rays is applied and exposed to ultraviolet rays for approximately 2 minutes in a vacuum (approximately 10 Pa). Discs 8 of the same structure were pasted together. Next, the information recording thin film 4 was irradiated with a recording laser beam from the substrate 1 side (downward on the paper) to record information. Next, the vicinity of the interface between the thin film 2 of the second protective layer and the substrate was examined using a microscope (x40
It was confirmed that the substrate was not altered or deformed. The second protective layer of this example (ZnS
)s. (Sin2) When the film thickness was changed by 2°, the noise level corrected for the laser power required for recording and the change in reflectance after 100 rewrites of recording changed as follows. Film thickness (nm) Recording laser power Noise level, :)
16mW -75dBm10
16 m W -80d B m50 1
6 m W 83 d B m100
17mW -85dBm300 18
mW -85dBm1000 20m
W -85d B m1500 22m
W -85dBm again. The thickness of the first protective layer is 10
It was usable in the range from 50 nm to 11000 nm, but when the wavelength was 50 nm to 200 nm, the noise level was 185 dBm or less, the recording power margin was 15% or more, and recording was possible with low laser power. Part or all of the Al-Mg alloy of the thin film 6 containing the above metal elements as main components is Al, Cu, or Ag. Au, Mg+ si, Ni, Ca, Ti, V, Cr, M
n, 'Fe, Co, Z'n, Zr, Nb, Mo. Rh, Zr, Pd, Sn, Sb, Te, Ta, W. Similar characteristics were obtained even when at least one selected from the group consisting of Ir, Pt, Pb, Bi, and C was replaced with one whose main component was Ir, Pt, Pb, Bi, and C. For example, when a Ni-Cr alloy was used, recording sensitivity was improved. In addition, when the thin film 6 mainly composed of the metal element mentioned above is a thin film with poor adhesiveness, such as a thin film mainly composed of Au, there is a gap between this film and the intermediate layer 5 such as Mo,
When an adhesion improving layer made of one of W and Cr was provided, the number of rewritable times was significantly increased. This film thickness is In
A suitable value was 30 nm or more and 30 nm or less. In addition, a part or all of Al and 01 in the first protective layer may be replaced with Tazo6. Y20yt S i3N4. AQ
N. A Q S i N,, A Q, S i N,, A
lSi2N3 and SiC (ZnS) of the second protective layer is replaced with one whose main component is at least one selected from Group A consisting of SiC. (S i Ox ) ZnS, CdS, In, S, Zn5
e, CdSe, In2Se3, Sin, , Sin, Ti
Similar results can be obtained even if the material is replaced with a material whose main component is at least one material selected from Group B consisting of O2 and ZrO□. Among these materials, An201 and Al-Si-N based materials of Group A are particularly preferred as materials used for the first protective layer. The thermal conductivities of these materials are as follows, by way of example: SiO2: lW/m-KznS:
2 W/m -K T i O2: 5 W/m -KZrO2:
3 W/m-KS i3N,: l 8
W/m-KAl203: 46 W/
m-KY20a: 15 W/m-KA
lN: 30 W/m -K SiC: 8 W/m -K For example, the first protective layer is A Q SiN z and the second protective layer is (Z n S) sa (S x O
z) 2°. Alternatively, the first protective layer is AflSiN2, the second protective layer is ZrO3, Ta2O5, or the first protective layer is Al203, and the second protective layer is SiO2.
Alternatively, the first protective layer may be formed of Al201. Similar results were obtained when the second protective layer was made of ZrO containing a small amount of Y2O3. The thermal conductivity of the thin film mainly composed of oxide, nitride, or carbide of the first protective layer in this example is 8 W/m・K or more 6
0W/m・K or less is preferable, 10W/m・K or more 50
W/m·K or less is particularly preferable. The thermal conductivity of the thin film mainly composed of oxide, sulfide, or selenide of the second protective layer is preferably IW/m·K or more and 6 W/m·K or less. When materials with different thermal conductivities were used, the number of rewrites possible when overriding with the recording laser power changed as follows. 16W >10' 16W >101 05l7 >10' 17mW >105 18 m W >10' 20mW 3xlO' 22mW lX104 In addition, the product of the refractive index and film thickness of the near-amorphous portion of the recording film is loonm or more, A reproduction signal CN ratio of 46 dB or more was obtained when the thickness was 600 nm or less and the product of the refractive index and film thickness of the intermediate layer was 50 nm or more and 600 nm or less. The product of the refractive index and film thickness of the crystalline portion of the recording film may be within the above range. If no intermediate layer is formed,
Although the recording sensitivity decreased by about 50%, there were no major changes in other characteristics, and it was usable. As shown in FIG. 2, a guide groove is formed on the surface of the ultraviolet curable resin layer 11 formed on a glass substrate 10, and a recording layer similar to that of the disk in FIG. A similar effect was obtained even when the disk was composed of a thin film 6 whose main component was a thin film 6) and was used without being bonded to another disk. In this case, an organic protective film 17 is further provided on the thin film 2.
It is preferable to form However, in these cases, the laser light was incident from the side opposite to the substrate 10. As shown in Fig. 3, conventionally, the noise level (B in the figure) increases by about 10 dB due to 105 times of information rewriting, but the first protective layer of the present invention is made of a material with high thermal conductivity, nitride, etc. The second protective layer is overridden multiple times by introducing a thin film mainly composed of oxides, selenides, or sulfides with low thermal conductivity into the second protective layer. It was also found that the noise level (A in the figure) hardly changed and there was little residual noise. When forming the above-mentioned first and second protective layers, as shown in Fig. 4, for example, using a ZnS target and an AU2O target side by side, sputtering is performed while moving the substrate with an in-line sputtering device. , a laminated film of a ZnS layer and an Al20 layer can be easily obtained in one sputtering chamber. The composition of these glabellar areas changes continuously. Effect of the Invention 1 According to the present invention, even if information is recorded by irradiating a recording thin film with a recording beam such as a laser beam, the heat generated by the irradiation with the recording beam is absorbed by the first protective layer. It is diffused by a thin film mainly composed of an oxide, nitride, or carbide with high thermal conductivity, and the second protective layer is mainly composed of an oxide, selenide, or sulfide with low thermal conductivity. Since it is blocked by the thin film, less heat propagates to the grooved resin provided in contact with the resin substrate or glass substrate surface of the disk. Further, the heat generated by the irradiation of the recording beam is also absorbed and diffused by the thin film mainly composed of the metal element, so that less heat is transmitted to the resin used for bonding the disks together. Furthermore, it has fewer pinholes, is resistant to stress generated during recording and erasing, and the resin does not deteriorate or deform.

[Brief explanation of drawings]

FIGS. 1 and 2 are cross-sectional views showing the structure of a recording member according to an embodiment of the present invention, and FIG. 3 shows changes in noise level with respect to the number of times information is rewritten by the recording members of the present invention and a conventional example. The characteristic measurement diagram and FIG. 4 are longitudinal cross-sectional views showing an example of a sputtering apparatus for producing the recording member of the present invention. Explanation of symbols

Claims (1)

[Claims] 1. A recording medium having an information recording thin film formed on a substrate that changes when irradiated with a recording beam,
Thermal conductivity is 8 W/m・K or more and 60 W in proximity to the above information recording thin film or adjacent to the above information recording thin film.
/m・K or less, the first protective layer is made of at least one material selected from materials mainly composed of oxides, carbides, or nitrides, and is located on the side closer to the information recording thin film, and has a thermal conductivity. A second protective layer made of at least one material selected from materials containing oxides, sulfides, or selenides as a main component whose A recording member comprising: 2. The first protective layer is Al_2O_3, Ta_2O_5, Y
Al-Si-N materials such as _2O_3, Si_3N_4, AlN, SiC, and AlSiN_2 and Al
- The second protective layer is made of a material having a composition close to at least one selected from Group A consisting of Si-O-N based materials, and the second protective layer is made of Si-O-N material.
O, SiO_2, TiO_2, ZrO_2 and ZnS
, CdS, In_2S_3, ZnSe, CdSe, and In_2Se_3.