JPH05109115A - Optical information recording medium - Google Patents

Abstract

PURPOSE:To improve durability by forming heat resistant protective layers of a mixture composed of elements having >=1600K p. and low-alkalinity glass. CONSTITUTION:This optical information recording medium is constituted successively of the heat resistant protective layer 2, an optically active layer 3, the 2nd heat resistant protective layer 2, and an org. resin protective layer 5 on a substrate 1. The heat resistant protective layers are formed of the low- alkaline glass dispersed with Nb, Mo, Ta, etc. The recording medium having a high CN and small deterioration in characteristics is obtd. and the durability is good. the low-alkaline glass consists essentially of SiO2, BaO, B2O3, Al2O3, etc. The alkaline metal content thereof is <1% in terms of an alkaline metal oxide and the compsn. thereof is 30 to 70% SiO2, 10 to 40% BaO, 5 to 25% B2O3 and 5 to 15% Al2O3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording medium. More specifically, the present invention relates to an optical information recording medium of a type capable of writing or reproducing arbitrary information by irradiating the optically active layer with a laser beam and further erasing recorded information. Regarding new configuration.

[0002]

2. Description of the Related Art Various types of optical information recording media, which are expected to be used as large-capacity and high-density information recording media, have been developed depending on differences in their recording systems and shapes.
Among them, the method of recording by utilizing the reversible phase change of the recording layer due to the irradiation of the laser beam, various improvements for practical use have been proposed as the most advanced recording method.

In a non-destructive type optical disc in which recorded information can be rewritten, various transparent resin substrates such as polycarbonate and glass substrates are used, but in particular, they are inexpensive and excellent in processability, Transparent resin substrates are widely used.

However, the transparent resin substrate may be thermally damaged by the laser beam applied when it is used as an optical information recording medium. In order to prevent this damage, the transparent resin substrate may be directly above or directly below the optically active layer. It has been proposed to provide a heat-resistant protective layer made of oxide or the like. In particular,
It has been reported that SiO ₂ and silicon nitride are effective materials for the heat-resistant protective layer.

[0005]

However, even in the optical information recording medium provided with the heat-resistant protective layer made of the above-mentioned material, C increases as the number of times of rewriting the recorded information increases.
There are problems such as deterioration of the / N ratio and cracking of the film when a durability test is performed.

Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art and to provide a novel optical information recording medium having a high physical and optical durability.

[0007]

That is, according to the present invention,
A substrate, a heat-resistant protective layer loaded on the substrate, an optically active layer loaded above the heat-resistant protective layer, and a physical protection layer loaded above the optically active layer. In an optical information recording medium of a method of recording information by irradiating the active layer with a laser beam to change the optical constant of the optically active layer, the heat resistant protective layer comprises a high melting point element having a melting point of 1600 K or more and a low melting point element. Provided is an optical information recording medium characterized by being formed of a mixture with an alkali glass.

[0008]

The main feature of the optical information recording medium according to the present invention is that the heat-resistant protective layer loaded to prevent the deterioration of the substrate is formed of a mixture of a specific element and a low alkali glass. There is.

That is, in the optical information recording medium of the type in which the optical constant of the optically active layer is changed by irradiating the recording beam to record or erase information, between the transparent resin substrate and the optically active layer, or The heat-resistant protective layer provided directly on the optically active layer has heretofore been formed of an oxide thin film or the like. However, it is known that the characteristics of an optical information recording medium provided with such a heat-resistant protective layer deteriorates during repeated writing and erasing of information, and durability as a practical information recording medium. Was not satisfied.

On the other hand, in the optical information recording medium according to the present invention, the heat resistant protective layer is formed of a mixture of a high melting point element having a melting point of 1600K or more and a low alkali glass. Here, the element having a melting point of 1600 K or more specifically means
Examples thereof include Nb, Mo, Ta, Ti, Cr, Zr, and Si, but are not limited to these.

That is, an optical information recording medium equipped with a heat-resistant protective layer formed of a low alkali glass in which an element having a high melting point is dispersed has a high C / N ratio, and even when writing / erasing of information is repeated. Little deterioration in characteristics. Further, as will be specifically described later, the durability test does not cause physical defects in the protective layer.

If the melting point of the element added to the heat-resistant protective layer of the optical information recording medium according to the present invention is less than 1600K, the desired effect cannot be obtained.

The mixing ratio of the low melting point glass and the high melting point element is preferably in the range of 90:10 to 30:70 (wt%). That is, when the mixing ratio is out of the above range, the desired effect cannot be obtained.

The low alkali glass used as the heat-resistant protective layer material of the optical information recording medium according to the present invention is Si
The main component is O ₂ , BaO, B ₂ O ₃ , Al ₂ O _3, etc., and the alkali metal content is 1 in terms of alkali metal oxide.
%, Meaning that the composition of SiO ₂ is 30-70%,
BaO is 10~40%, B ₂ O ₃ is 5~25%, Al ₂ O ₃ is 5
15%.

Hereinafter, the present invention will be described in more detail with reference to examples, but the following disclosure is merely an example of the present invention and does not limit the technical scope of the present invention.

[0016]

【Example】

[Embodiment] FIG. 1 is a sectional view showing the basic structure of an optical information recording medium according to the present invention.

As shown in the figure, this optical information recording medium comprises a heat-resistant protective layer 2, an optically active layer 3, a second heat-resistant protective layer 2 and an organic resin protective layer 5 which are sequentially formed on a substrate 1. Has been done.

Here, the substrate 1 is generally disk-shaped, but may be card-shaped or drum-shaped. As a material for forming the substrate 1, a transparent resin material such as a polycarbonate resin, a polymethylmethacrylate resin, an epoxy resin and an amorphous polyolefin resin can be preferably used. The optically active layer 3 is made of a material that has a large change in refractive index or extinction coefficient due to a phase change and is reversible in the phase change and capable of recording and erasing. More specifically
Te-based media such as TeGeSb, TeGeSn, TeSb, TeSeSn, InSe, In
In-based media such as SbTe, InSb and InSbSe can be used.

The second heat-resistant protective layer 2 may be omitted in the structure shown in FIG.

FIG. 2 is a sectional view showing another structure of the optical information recording medium to which the present invention can be applied. As shown in the figure, this optical information recording medium is one in which a reflective layer 4 is added between the second heat-resistant protective layer 2 and the organic resin protective layer 5 of the optical information recording medium shown in FIG. .. Note that in FIG. 2, common reference numerals are given to constituent elements common to FIG.

Here, as the material of the reflective layer 4, Au, A
A high-reflectance metal containing l, Ag, NiCr or the like as a main component can be preferably used.

[Manufacturing Example 1] An optical information recording medium having the structure shown in FIG. 1 was actually manufactured by using a disk substrate with a spiral groove made of polycarbonate resin having a diameter of 130 mm.

Corning # 7059 was used as the low alkali glass for forming the heat-resistant protective layer. This product contains the following composition: _{SiO 2: 49.2%, BaO:} 25.0%, B 2 O 3: 14.5%, Al 2 O 3: 10.9%: Na 2 O: less than 0.2%, K ₂ O: low alkali containing such a composition less than 0.1% A heat-resistant protective layer was formed on the substrate by a binary simultaneous sputtering method using glass and Nb as targets. The film formation was performed in the presence of 4 mTorr of argon gas. The heat-resistant protective film obtained had a mixing ratio of 80:
It was a mixture of 20 wt% low alkali glass and Nb, and its thickness was 1000Å.

Then, a TeGeSb thin film (composition ratio 55:
15:30 at.%) Was deposited by the DC sputtering method. The thickness of the optically active layer was 800Å.

Further, after the second heat-resistant protective layer having a thickness of 1000Å is formed on the optically active layer by using the same material and method as the above-mentioned film formation of the heat-resistant protective layer, finally, the ultraviolet curability is set. A resin (SD-301 manufactured by Dainippon Ink Co., Ltd.) was applied to a thickness of 10 μm by a spin coating method, and this was cured by ultraviolet rays to form a protective layer.

With respect to the optical information recording medium manufactured as described above, 60 ° from the center of rotation of the medium rotating at 1800 rpm
The frequency is 3.7M with a semiconductor laser of wavelength 830nm at the position of mm.
After recording the repetitive signal of Hz and duty22%, the operation of reproducing and erasing this signal was repeated. The recording power when writing information is 14 mW, and the erasing power is 8 mw.
And Table 1 shows the result of measuring the C / N ratio of the reproduced signal in such an operation together with the initial value.

Further, this optical information recording medium is provided with JIS C 0
After the Z / AD cycle test specified in 028,
The number of cracks generated on the medium was counted. The counting results are shown in Table 2.

Comparative Example 1 An optical information recording medium basically having the same structure as that shown in FIG. 1 was manufactured by using a disk substrate having the same specifications as those used in Manufacturing Example 1. However, different materials were used for the heat-resistant protective layer.

That is, in this comparative example, a silicon nitride thin film formed by carrying out an RF reactive sputtering method using a silicon target in the presence of a mixed gas of 4 mTorr of Ar and nitrogen was used as a heat resistant protective layer. The heat-resistant protective layer had a thickness of 1000Å.

Then, an optically active layer having the same specifications as those in Preparation Example 1 was formed by the DC sputtering method, and then a second heat resistant protective layer was formed again using a silicon target. Finally, an ultraviolet curable resin (SD-301 manufactured by Dainippon Ink & Co., Inc.) was applied as a protective film by a spin coating method to a thickness of 10 μm and then irradiated with ultraviolet rays to be cured to complete an optical information recording medium.

The optical information recording medium manufactured as described above was evaluated for characteristics and durability in the same manner as in Manufacturing Example 1. The evaluation results are also shown in Tables 1 and 2.

[Manufacturing Example 2] An optical information recording medium was manufactured using a disk substrate having the same specifications as those in Manufacturing Example 1 and Comparative Example 1.

Targeting SiO ₂ and Nb, 4 mto
Thin film of mixture of SiO ₂ and Nb by _binary co-sputtering method in the presence of Ar gas of rr (mixing ratio 80:20 wt%)
To form a heat resistant protective layer. The thickness of the heat-resistant protective layer is 1000
Å

Then, TeGeSb is formed by DC sputtering.
1000 heat resistant protective layer consisting of (composition ratio 55:15:30 atom%)
Å A film was formed, and finally, an ultraviolet curable resin (SD-301 manufactured by Dainippon Ink & Co., Ltd.) was applied in a thickness of 10 μm by a spin coating method, and then cured by ultraviolet irradiation to form a protective layer.

With respect to the optical information recording medium manufactured as described above, the characteristics and durability were evaluated by the same method as in Manufacturing Example 1. The evaluation results are also shown in Tables 1 and 2.

[0036] Comparative Example 2 The heat-resistant protective layer 1000Å of SiO ₂ was formed by RF sputtering φ130mm polycarbonate resin spiral grooved disc substrate in an argon gas pressure of 4mtorr using SiO ₂ target,

Subsequently, 800 Å of an optically active layer of TeGeSb (composition ratio 55:15:30 atom%) was formed by DC sputtering, and then 1000 Å of a heat-resistant protective layer of SiO ₂ was formed again by RF sputtering. .. Finally, an ultraviolet curable resin (SD-301 manufactured by Dainippon Ink & Co., Ltd.) was applied by a spin coating method to a thickness of 10 μm and then cured by irradiation with ultraviolet rays to form a protective layer.

The optical information recording medium manufactured as described above was evaluated for characteristics and durability in the same manner as in Manufacturing Example 1. The evaluation results are also shown in Tables 1 and 2.

[Manufacturing Example 3] An optical information recording medium having the structure shown in FIG. 2 was manufactured using a disk substrate having the same specifications as those in Manufacturing Example 1 and Comparative Example 1.

Low-alkali glass (Corning # 705
Using 9) and Zr as targets, a mixture thin film (mixing ratio 80: 20% by weight) to be a heat resistant protective layer was formed by a binary simultaneous sputtering method in the presence of 4 mtorr of argon gas. The thickness of the heat-resistant protective layer was 1500Å.

Subsequently, a 400 Å-thick optically active layer of TeGeSb (composition ratio 55:15:30 atom%) was formed by DC sputtering, and then low alkali glass was formed again by binary simultaneous sputtering. The second heat-resistant protective layer was formed from a thin film of a mixture with Zr (mixing ratio 80: 20% by weight). The thickness of the second heat-resistant protective layer is
It was 400Å.

Next, the thickness of Al formed by DC sputtering is 3
A 00Å reflective layer was deposited. Finally, 5 μm of UV curable resin (SD-17 made by Dainippon Ink) was applied by spin coating.
After being applied to a thickness of m, it was cured by ultraviolet irradiation to form a protective layer.

The optical information recording medium manufactured as described above was evaluated for characteristics and durability in the same manner as in Manufacturing Example 1. The evaluation results are also shown in Tables 1 and 2.

Comparative Example 3 An optical information recording medium having the structure shown in FIG. 2 was produced using the disk substrate having the same specifications as in Production Example 3.

Using a silicon target in the presence of a mixed gas of 4 mtorr of argon and nitrogen, RF reactive sputtering was performed to form a silicon nitride film having a thickness of 1500.
A heat resistant protective layer of Å was formed on the substrate.

Then, Te is formed by DC sputtering.
After forming a 400 Å-thick optically active layer made of GeSb (composition ratio 55:15:30 atom%), a second heat-resistant protective layer made of silicon nitride was again formed by RF reactive sputtering. Second
The thickness of the heat-resistant protective layer was 400 Å.

Next, a reflective layer of Al having a thickness of 300Å was formed by DC sputtering. Finally, a 5 μm-thick UV curable resin (SD-17 manufactured by Dainippon Ink & Co., Ltd.) was applied by a spin coating method, and this was cured by UV irradiation to form a protective layer.

The optical information recording medium manufactured as described above was evaluated for characteristics and durability in the same manner as in Manufacturing Example 1. The evaluation results are also shown in Tables 1 and 2.

[0049]

[Table 1]

[0050]

[Table 2]

[0051]

As described above, the optical information recording medium according to the present invention is excellent not only in its recording characteristics but also in its durability.

[Brief description of drawings]

FIG. 1 is a sectional view showing a typical structure of an optical information recording medium to which the present invention is applicable.

FIG. 2 is a cross-sectional view showing another structure of the optical information recording medium to which the present invention can be applied.

[Explanation of symbols]

1 substrate, 2 heat resistant protective layer, 3 optically active layer, 4 reflective layer, 5 organic resin protective film

Claims (8)

[Claims] 1. A substrate, a heat-resistant protective layer loaded on the substrate, an optically active layer loaded above the heat-resistant protective layer, and a physical protection layer loaded above the optically active layer. In the optical information recording medium of the type which records information by changing the optical constant of the optically active layer by irradiating the optically active layer with laser light, the heat resistant protective layer has a melting point of 1600K or more. An optical information recording medium, which is formed of a mixture of a high melting point element and a low alkali glass. 2. The optical information recording medium according to claim 1, further comprising a second heat-resistant protective layer between the optically active layer and the physical protective layer, the second heat-resistant protective layer. But 16
An optical information recording medium comprising a mixture of a high melting point element having a melting point of 00K or more and a low alkali glass. 3. The optical information recording medium according to claim 1, further comprising a reflective layer above the optically active layer or the second heat-resistant protective layer. recoding media. 4. The optical information recording medium according to any one of claims 1 to 3, wherein a mixing ratio of the low alkali glass and the high melting point element is 90:10 by weight or more.
An optical information recording medium characterized by being in the range of 30:70. 5. The optical information recording medium according to claim 1, wherein the refractory element is Nb, Mo, Ta, Ti, Cr, Zr or Si. An optical information recording medium comprising at least one element selected from the more selected elements. 6. The optical information recording medium according to any one of claims 1 to 5, wherein the low alkali glass has an alkali metal content of less than 1% in terms of alkali metal oxide. An optical information recording medium characterized by: 7. The optical information recording medium according to any one of claims 1 to 6, wherein the low alkali glass is mainly SiO ₂ , BaO, B ₂ O ₃ or Al ₂ O ₃ . An optical information recording medium characterized by being used as a component. 8. The optical information recording medium according to any one of claims 1 to 7, wherein the low alkali glass is SiO ₂ : 30 to 70%, BaO: 10 to 40%, B An optical information recording medium comprising a composition containing ₂ O ₃ : 5 to 25% and Al ₂ O ₃ : 5 to 15% as a main component.