JPH117656A - Optical information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflective layer containing a noble metal and a protective layer made of a resin material in an optical information recording medium, which have poor adhesion and are difficult to form by lamination. The purpose is to enable adhesion and to enable lamination of both layers. A material layer (6) selected from the group consisting of nitride, oxide, fluoride, carbide, and sulfide is provided between a reflective layer (5) containing a noble metal and a protective layer (7) made of a resin material.
To form The thickness of the material layer 6 is set to 5 to 20 nm so as not to affect the optical and thermal characteristics, and is most preferably about 10 nm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording medium for optically recording, reproducing, and erasing information.

[0002]

2. Description of the Related Art As an optical information recording medium, for example, an optical disk generally has a multilayer structure having a recording layer, a reflection layer, and a light interference layer, and reads out a signal using a multiple interference effect. Conventionally, registered patent 1949320, registered patent 209
No. 4839 is known, and the reflection layer optically increases the amount of light absorbed by the recording layer and thermally diffuses the heat generated in the recording layer quickly. In addition, it also has a role of protecting the multilayer film from the use environment. Among metals, noble metals are not easily oxidized and have excellent corrosion resistance, so that they are suitable for the reflective layer material. In particular, Au is excellent in corrosion resistance, and is most excellent as a reflective layer material which has a thin film thickness and satisfies rapid cooling conditions.

[0003]

However, noble metals are hardly oxidized and are chemically stable as compared with polymetals, so that their adhesion to resins is poor. For example, when Au is used for the reflective layer, there is a problem that the adhesiveness of the acrylic resin to the protective layer is so poor that it cannot be formed on the reflective layer.

An object of the present invention is to solve the above problems and to form a protective layer of a resin on a reflective layer containing a noble metal.

[0005]

SUMMARY OF THE INVENTION In order to solve this problem, the present invention provides an optical information recording medium having a reflective layer containing at least a noble metal on a substrate and a protective layer made of a resin material. A material layer selected from the group consisting of nitride, oxide, fluoride, carbide, and sulfide is formed between the layers.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to a first aspect of the present invention, there is provided a recordable recording layer comprising a reflective layer containing a noble metal, a protective layer made of a resin material, and a single layer or a plurality of layers on a substrate. An optical information recording medium having a layer, wherein the recording layer is formed between the substrate and the reflective layer, and a nitride, an oxide, a fluoride, a carbide, a sulfide is provided between the reflective layer and the protective layer. A material layer selected from a group formed from objects is formed.

According to a second aspect of the present invention, there is provided an optical device having a reflective layer containing a noble metal on a substrate, a protective layer made of a resin material, and a single or multiple information recording layer. An information recording medium, wherein the recording layer is formed between the substrate and the reflective layer, the protective layer is mainly composed of an epoxy resin, and the curing shrinkage X of the protective layer is 0 ≦ X ≦
5 (%), and the viscosity Y before curing of the protective layer at 25 ° C. is 600 ≦ Y ≦ 1400 (cP).

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a configuration example of an optical information recording medium of the present invention, in which a first light interference layer 2, a recording layer 3, a second light interference layer 4, a reflection layer 5, and a material layer 6 are provided on a substrate 1.
Are sequentially laminated to form a single-plate structure in which a protective layer 7 is applied.

As the substrate 1, a disk-shaped substrate such as a resin such as PMMA, polycarbonate or amorphous polyolefin or glass, which is transparent and has a smooth surface, which is usually used for an optical disk, is selected.

The first light interference layer 2 and the second light interference layer 4 are dielectric thin films, and adjust the path length of light to increase the light absorption efficiency to the recording layer, and reduce the change in the amount of reflected light before and after recording. Enlarge and C
It has the function of raising the N ratio. The light interference layers 2 and 4 are, for example, S
oxides such as iO ₂ and Ta ₂ O ₅ , GeN, SiN, Al
Nitride such as N and TiN, sulfide such as ZnS, SiC
Such as carbides, fluorides such as CaF ₂ and mixtures thereof, such as ZnS—SiO ₂ ,
It can be formed by a method such as sputtering or vapor deposition. The thickness of the first and second optical interference layers can be determined, for example, by a matrix method (for example, Hiroshi Kubota, “Wave Optics”, Iwanami Shinsho, 19
(Refer to Chapter 3 in 1971) can be strictly determined so as to satisfy the condition that the change in reflectance before and after recording is larger and the light absorption to the recording layer is sufficiently large.

The material of the recording layer 3 is a material which causes a reversible phase transformation between a crystalline phase and an amorphous phase, and is typically Ge-Sb-Te, Ge-Te, In-Sb-T.
e, Ge-Sb-Te-Pd, Ag-Sb-In-Te
Or an oxide or nitride thereof. Tb-Fe-Co and Gd-Fe-C are magneto-optical recording materials comprising a rare earth element and a transition metal element.
o, Gd-Tb-Fe-Co, Dy-Fe-Co, Gd
-Dy-Fe-Co or the like can also be used.

Au, Pt, Ag, Pd
Alternatively, an alloy containing these as main components can be used. The reflection layer optically increases the amount of light absorbed by the recording layer, thermally diffuses the heat generated in the recording layer quickly, and furthermore, has a role of protecting the multilayer film from the use environment. Also has. Among them, Au is an excellent material which is excellent in corrosion resistance and has a small thickness and satisfies the quenching condition.

The material layer 6 is made of GeN, SiN, Al
Nitrides such as N and TiN, oxides such as SiO ₂ and Ta ₂ O ₅ , fluorides such as CaF _2, and carbides such as SiC;
As a sulfide such as ZnS and a mixture thereof, ZnS-
SiO ₂ or the like can be used. Light interference layers 2 and 4
However, since the function of the material layer 6 is an adhesive layer for forming the protective layer 7 on the reflective layer 5, the optical properties and thermal properties of the multilayer structure do not change. It is formed with a thin film thickness. Therefore, the thickness is at most 30 nm, preferably about 10 nm.

The protective layer 7 is a material containing an acrylic resin as a main component. For example, a mixture of a UV-curable urethane acrylate and an acrylate monomer can be used. Since the optical information recording medium is rotated and applied, the lower the viscosity, the easier the application, and the thinner and more uniform the thin film can be formed in a short time. If it is thin, it cures in a short ultraviolet irradiation time, and the time from application to curing can be shortened. Therefore, the viscosity is preferably in the range of 10 to 100 cP,
0 cP or less is more preferable.

FIG. 2 is a partial cross-sectional view of another embodiment of the optical information recording medium of the present invention, in which a first light interference layer 2, a recording layer 3, and a second light interference layer 4 are formed on a substrate 1. The reflective layer 5 is sequentially laminated to form a single-plate structure in which a protective layer 8 is applied. FIG.
The material of the first optical interference layer 2, the recording layer 3, the second optical interference layer 4, and the reflective layer 5 is selected from the same group as described with reference to FIG. 8 is formed. This configuration does not require the material layer 6, so that the number of layers in the multilayer configuration can be reduced by one.

The protective layer 8 is made of a material mainly composed of an epoxy resin. For example, a mixture of an epoxy resin and a styrene copolymer is used.
It can be formed by applying it on the top and polymerizing and curing by irradiation of ultraviolet rays. When applied directly to the reflective layer containing a noble metal, the higher the viscosity, the better the adhesion. At least 600 cP or more viscosity is required and 1000 cP or more and 1400 c
Most preferably P or less. Further, since the composition is applied directly on the reflection layer containing a noble metal, the shrinkage ratio due to curing is preferably as small as 5% at most.

In the above description, an optical information recording medium having a single-plate structure in which a protective layer is formed has been described as an example.
In addition, the present invention can be similarly applied to an optical information recording medium having a double-sided structure in which two optical information recording media formed up to the protective layer are bonded to each other on the protective layer side with, for example, a hot-melt adhesive.

[0018]

Next, embodiments of the present invention that we have experimented will be described.

(Example 1) An experiment was conducted using a stationary facing type sputtering apparatus having a target having a diameter of 203 mm and seven vacuum chambers provided with a power supply for generating vacuum discharge. First, a first optical interference layer, a recording layer, a second optical interference layer,
Each layer was formed on a glass substrate piece using the materials and conditions shown in Table 1 to measure the sputter rates of the reflective layer and the material layer.

[0020]

[Table 1]

Ar gas was used as a sputtering gas. The sputter rate was determined by measuring the film thickness by the stylus method. Strictly control the film thickness from the obtained sputter rate,
A thin film sample for determining the refractive index n and the extinction coefficient k of each layer was prepared. The thin film had an extremely thin film thickness of about 20 nm, at which the transmittance was sufficiently high in order to increase the accuracy of determining n and k. For the recording layer, n and k of the amorphous phase and the crystalline phase are determined. Since the amorphous phase after sputtering, the crystalline phase was prepared by heat treatment in a nitrogen atmosphere. The film thickness is measured by the above method, and the reflectance and the transmittance are measured by a spectrometer, and n, k are calculated by using the measurement results.
It was determined. The obtained sputter rates and n and k are shown in (Table 2).

[0022]

[Table 2]

(Embodiment 2) Using the n and k values determined in Embodiment 1, optical calculation of a multilayer structure is performed by a matrix method to determine the film thicknesses of the first light interference layer and the second light interference layer. did. The calculation does not include the material layer. The recording layer is 23 nm,
The reflection layer is fixed to 10 nm, and the reflectance Rc in the crystalline state, the reflectance change ΔR, the absorptivity Ac in the crystalline state, the absorptivity ratio Ac / Aa between the crystalline phase and the amorphous phase are calculated, and Rc> 20.
%, ΔR> 15%, Ac> 60%, and Ac / Aa> 1, the thickness of the light interference layer was determined. Calculation wavelength is 790
nm. The values of the determined film thickness, reflectance and absorptance are shown in (Table 3). The thickness of each layer had a tolerance of ± 5%.

[0024]

[Table 3]

[0025] (Example 3) in the case of forming the material layer ZnS-SiO ₂ on a reflective layer configuration decided in Example 2, changes in optical characteristics with respect to the thickness of the material layer was calculated, does not change the optical properties The thickness range of the material layer was determined. The calculation results are shown in (Table 4).

[0026]

[Table 4]

From the results shown in Table 4, the thickness of the material layer was 30 n.
m or more, the change in the optical characteristics becomes large.
It turns out that about 10 nm is most preferable in m.

(Embodiment 4) Based on the calculation results of Embodiment 3, the first light interference layer 2 is 130 nm, and the recording layer 3 is 23 n.
m, the second light interference layer 4 is 24 nm, and the reflection layer 5 is 10 nm.
The thickness of the material layer 6 is 0 nm, 5 nm, 10 nm,
Seven types of discs of 20 nm, 30 nm, 50 nm, and 100 nm were prototyped, and the application state of the acrylic resin was confirmed. 120 m diameter with 1.2 μm pitch guide grooves
The first light interference layer 2, the recording layer 3, and the second light were formed on the polycarbonate substrate 1 with the stationary facing sputtering apparatus described in Example 1 under the film forming conditions described in (Table 1). The interference layer 4, the reflection layer 5, and the material layer 6 were sequentially laminated. After lamination, the disk was taken out of the vacuum chamber, and the protective layer 7 was applied through an initialization step. For the protective layer 7, a mixture of urethane acrylate and acrylic acid ester monomers was used, applied at a rotation speed of 1250 rpm, and spread over the entire surface with a thickness of about 3 μm at 4500 rpm for 2 seconds. A low viscosity is more suitable for thin and uniform application, and the acrylic resin used in this example has a viscosity of about 23 cP. After spreading all over, 50
Ultraviolet rays having an intensity of 0 mW / cm ² were irradiated for 3 seconds for curing. The results of visually confirming the state after curing are shown in (Table 5).

[0029]

[Table 5]

From these results, it was found that when the material layer 6 was not provided, it could not be directly applied to the reflective layer 5, but when the material layer 6 was 5 nm, it could be applied uniformly to the entire surface of the disk.

(Embodiment 5) The recording characteristics of the innermost peripheral portion and the outermost peripheral portion of the disk prototyped in Example 4 were evaluated. The reflectance was also measured. When the material layer 6 has a thickness of 0 nm (disk A), the protective layer 7 cannot be applied.
nm (C), 20 nm (D), 30 nm (E), 50 n
For the discs of m (F) and 100 nm (G), the recording layer was compared with the film thickness of the material layer 6 without applying the protective layer 7, and a relative comparison was made. The purpose of this experiment is to clarify the thickness range of the material layer 6 in which the thermal characteristics of the disk do not change. Further, by measuring the reflectivity of the prototype disk, a comparison with the calculation results performed in Example 2 can be made, and the range of the film thickness of the material layer 6 that does not change the optical characteristics can be experimentally determined. The evaluation conditions of the recording characteristics are a disk rotation speed of 2000 rpm, a laser wavelength of 780 nm, and a recording signal of a 1.5T signal. The CN ratio was measured by changing the recording peak power while fixing the erase bias power at both the innermost and outermost portions. Assuming that the peak power at which the CN ratio is 43 dB is −25%, the peak powers of −25, 0, and + 10% at the innermost and outermost portions are determined from the evaluation result of the disk A, and the disks B, C, D, E, and F About CN
The ratio was measured. The results are shown in (Table 6).

[0032]

[Table 6]

The recording peak power at the outermost periphery is 9 m in order.
W, 12 mW, 13.2 mW and erase bias power of 6
mW fixed, the recording peak power at the innermost circumference is 7.5 m in order
W, 10mW, 11mW, erase bias power is 4mW
Fixed. From this result, the thickness of the material layer 6 is 0 to 20 n.
Up to m, the saturation value of the CN ratio does not change. At a recording peak power of −25%, there is a slight difference in the CN ratio between the innermost portion and the outermost portion, but it can be determined that there is substantially no change in the recording sensitivity. Further, when the thickness is 30 nm or more, the decrease in the CN ratio becomes remarkable, and it can be seen that both optically and thermally affect the disk characteristics. When compared with the results of the optical calculations performed in Example 3, the tendency that ΔR and Ac decrease from 30 nm agrees well. Next, Table 7 shows the measurement results of the reflectance at the innermost peripheral portion and the outermost peripheral portion.

[0034]

[Table 7]

Regarding the reflectance, the calculated value is in good agreement with the calculated optical value, and does not affect the reflectance up to 30 nm. From the above results, the thickness range of the material layer 6 that can be formed without causing optical and thermal changes is 5 to 30 nm,
It is clear that nm is optimal.

(Embodiment 6) Embodiments 1, 2, 3, 4, 5
Was performed for the other noble metal elements Pt, Ag, and Pd as the reflection layer 5, and similar results were obtained.

(Embodiment 7) Embodiments 1, 2, 3, 4, 5
For the material layer 6, Ta ₂ O ₅ , GeN, ZnS, Si
Similar results were obtained for C and CaF ₂ .

(Embodiment 8) Next, a second invention will be described. 120 m in diameter with the materials and film forming conditions described in (Table 1)
The first optical interference layer 2 was formed on the polycarbonate substrate 1 by a thickness of 130 nm, the recording layer 3 was formed to a thickness of 23 nm, the second optical interference layer 4 was formed to a thickness of 24 nm, and the reflection layer 5 was formed to a thickness of 10 nm by sputtering. In order to determine the viscosity of the resin that can be directly applied to the reflective layer 5, an application experiment was performed by changing the mixing ratio of the epoxy resin and the styrene copolymer. (Table 8)
Shown in

[0039]

[Table 8]

The resin having a viscosity of 1000 to 1500 cP is Au
The coating could be performed without repelling the reflective layer 5, and the coating was repelled below 500 cP, causing application unevenness. If the viscosity is large, the coating thickness becomes large.
000-1400 cP is most preferred. In addition, not only epoxy resin but also acrylic resin has a viscosity of 1000 to 140.
It was confirmed that it was possible to apply to other noble metals such as Ag, Pt and Pd if it was 0 cP. Although the coating time and the coating thickness are larger than those of a resin having a low viscosity, the equipment can be simplified because the material layer does not need to be formed.

[0041]

As described above, the present invention relates to an optical information recording medium having a reflective layer containing at least a noble metal and a protective layer made of a resin material on a substrate, wherein a nitride is provided between the reflective layer and the protective layer. By forming a material layer selected from the group consisting of oxides, fluorides, carbides, and sulfides, a resin having a low viscosity is formed on the noble metal reflection layer without changing the optical and thermal characteristics. The effect of being able to apply was obtained.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view of an embodiment of an optical information recording medium of the present invention.

FIG. 2 is a partial sectional view of another embodiment of the invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 1st light interference layer 3 recording layer 4 2nd light interference layer 5 reflection layer 6 material layer 7 protective layer 8 protective layer

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Noboru Yamada 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (10)

[Claims] 1. An optical information recording medium having a reflective layer containing a noble metal on a substrate, a protective layer composed of a resin material, and a recording layer composed of a single layer or a plurality of layers on which information can be recorded. And the recording layer is formed between the reflective layer and a material layer selected from the group consisting of nitride, oxide, fluoride, carbide, and sulfide between the reflective layer and the protective layer. An optical information recording medium characterized by being formed. 2. An optical information recording medium having a reflective layer containing a noble metal on a substrate, a protective layer made of a resin material, and a recording layer capable of recording information comprising a single layer or a plurality of layers. The recording layer is formed between the protective layer and the reflective layer, the protective layer is mainly composed of an epoxy resin, and the curing shrinkage X of the protective layer is 0 ≦ X ≦ 5 (%). The viscosity Y before curing at 600 ° C. is 600 ≦ Y ≦ 14
00 (cP). 3. The optical information recording medium according to claim 1, wherein the optical information recording medium is of a read-only type in which an uneven pit signal is recorded on a substrate. 4. The recording medium according to claim 1, wherein at least a write-once recording layer is provided between the substrate and the reflective layer.
The optical information recording medium according to the above. 5. The recording medium according to claim 1, further comprising at least a rewritable recording layer between the substrate and the reflection layer.
The optical information recording medium according to the above. 6. A protective layer comprising an acrylic resin as a main component, a curing shrinkage A of 8 ≦ A ≦ 12 (%) and a viscosity B before curing at 25 ° C. of 10 ≦ B ≦ 100 (cP). The optical information recording medium according to claim 1, wherein: 7. The thickness d of the protective layer is 2 ≦ d ≦ 30 (μm)
The optical information recording medium according to claim 1, wherein: 8. The thickness D of the material layer is 5 ≦ D ≦ 30 (nm)
The optical information recording medium according to claim 1, wherein: 9. The optical information recording medium according to claim 1, wherein the reflection layer contains Au as a main component. 10. The optical information recording medium according to claim 1, wherein the material layer contains ZnS—SiO ₂ as a main component.