JP2003182217A - Optical recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To develop a recording film high in reflectivity and sensitivity and to inexpensively provide an optical recording medium good in C/N of a feedback signal and excellent in weatherability. <P>SOLUTION: In the optical information recording medium which is composed of at least a transparent substrate 1, the first recording layer 2, and the second recording layer 3 and capable of recording and reproduction by being irradiated with energy beams, the first recording layer 2 mainly comprises Ag, the second recording layer 3 is an alloy layer containing at least two elements of Te and Sb, and the first recording layer 2 and the second recording layer 3 are mixed with each other by being irradiated with light to change an optical constant. <P>COPYRIGHT: (C)2003,JPO

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 capable of recording / reproducing by making an optical change in a recording layer by irradiation with an energy beam.

[0002]

2. Description of the Related Art CD is used as an optical information recording medium (hereinafter referred to as an optical recording medium) which can be recorded by irradiation of a laser beam.
There are write-once type optical recording media such as -R and DVD-R. These optical recording media are CD-ROM or DVD-RO.
It has playback compatibility with M and is used as a small-scale distribution medium and storage medium. However, CD-R, DV
Since D-R is coated with an organic dye, there is a problem that the manufacturing cost is significantly higher than that in the ROM process. Therefore, CD-write once (hereinafter referred to as WO) and DVD-WO media have been developed. WO media are classified into a perforated type, a phase change type, and an alloyed type. The hole recording method is promising from the viewpoint of cost, but the hole recording has a problem that the C / N becomes low. This was because the melted film remained in the pit like a polka dot and swelled up in the peripheral part in the pit part where the hole was formed. Further, if the perforation recording method is used, the layer structure is one layer, but the recording film that has been normally used cannot cope with the high reflectance of the ROM, resulting in a nonstandard product.

In order to realize a high reflectance for ROM with a single layer of the recording film, Al, Ag, Cu, etc. are conceivable, but the reflectance is too high and a hole cannot be opened by ordinary laser irradiation.

Japanese Patent Laid-Open No. 60-17 discloses a recording material for punching.
There are compounds of Te and Au or Ag disclosed in JP-A-9953, JP-A-60-179952, etc., but these materials have a boiling point of 1000 ° C. or higher, which is an extremely low sensitivity optical recording medium. is there.

Further, JP-A-57-157790 discloses an attempt to enhance recording sensitivity by forming a first layer which releases volatile components at a temperature of 400 ° C. or less and a corrosion resistant metal on the first layer. Although the inventions described above are described, they are not intended to increase the reflectance and cannot be ROM compatible. Corrosion-resistant metals are Au, Ag, etc., but these have extremely high thermal conductivity and the heated energy escapes by diffusion, resulting in low effect and unsuitable for high linear velocity recording. It was

As the alloying method, Ge or SiSn is used.
Layer selected from the elements of Au, Ag, Al, C
A method of irradiating a layer made of an element selected from the elements of u with a laser to alloy these two layers for recording is disclosed in Japanese Patent Application Laid-Open No. 4-204
As proposed in Japanese Patent No. 226784, low to
It was a high record and could not be ROM compatible.

As an invention for forming a phase change type recording layer from an alloy of In and Te, there is JP-A-1-162247, and In: Te = 2: 1 to 1: 1 or 2: 3 to.
It is an object of the present invention to provide a phase change type optical recording medium because of 2: 5, but in the present invention, an initialization process is necessary because the state during film formation is amorphous and the reflectance is low. . Therefore, the number of processes is increased and the cost is increased.

Further, in comparison with the phase change type in which it is sufficient to raise the temperature to the melting point, the punching recording method requires a large amount of heat to raise the temperature above the boiling point for recording.
Therefore, a laser power larger than that of the phase change type is required, and the power of the semiconductor laser becomes insufficient for high linear velocity recording. That is, a recording film with higher sensitivity is required.

Further, in Japanese Patent No. 2948899, the first layer (layer-change alloy thin film) contains Ag-Zn, and the second layer (low melting point thin film) contains Te, Se, S as a main component. Although the invention of recording by diffusion is described, this is because the first layer is thickened to 300-700Å and the second layer is thickened to 500-1500Å in order to increase the reflectance, which results in tact and cost during production It is at a disadvantage.

Inorganic WO has various problems as described above.
This has been a major obstacle to the popularization of recording media.

[0011]

Under the above circumstances, the present invention has developed a recording film having high reflectance and sensitivity, and an inexpensive optical recording medium having a good C / N of a reproduced signal and excellent weather resistance can be obtained. It is intended to be provided to.

[0012]

As a result of intensive studies, the present inventors have made an optical information recording which is composed of at least a transparent substrate, a first recording layer and a second recording layer and can be recorded / reproduced by irradiation of an energy beam. In the medium, the first recording layer is mainly made of Ag, and the second recording layer is at least Te and Sb.
And an optical recording medium characterized in that the first recording layer and the second recording layer are mixed with each other by irradiation of light to change the optical constants. It was possible to obtain an optical recording medium having high reflectance and sensitivity. That is, when the surfaces are heated to above the melting points of the first recording layer and the second recording layer by irradiation of light, the two layers are melted by this and the two layers are mixed by diffusion. Then, when they are mixed, the reflectance is lowered in the film structure of the present invention. As a result, high to low
It has become possible to obtain a write-once type optical recording medium which has a change in reflectance and is ROM compatible.

A recording method based on diffusion of two layers has been considered for some time. For example, Ge / Al or the like. However, the conventional methods are basically low to hi.
The reflectance was changed by gh, and it was not ROM compatible.

In the present invention, silver having a high reflectance is thinly formed on the laser irradiation side to form an Sb-Te film thereon, and the first recording layer and the second recording layer are formed by light irradiation. By mixing them together, it was possible to obtain a reflectance change of high to low. Although the mechanism of this recording mechanism has not been elucidated accurately, one idea is that electrons generated by absorption of light by the Sb-Te semiconductor forming the second recording layer are trapped in the impurity level, etc. It is considered that electrolysis is generated, and this attracts Ag +, which has become positive ions, to cause diffusion. Further, it is considered that the heat generation due to the absorption of light also enhances the diffusion effect. At this time, Sb-In, In-Te, and In-Sb-Te also showed the same effect.

In the present invention, (the film thickness of the first recording layer) /
Since the (thickness of the second recording layer) is in the range of 0.1 to 1.0, the two characteristics of high reflectance and high sensitivity have been successfully achieved.

Further, the film thickness of the first recording layer is 50-200Å
Therefore, when Ag was used as the first recording layer, the reflectance was too high to absorb light and the thermal conductivity was too high to raise the temperature of the film. By setting the film thickness within the range, it becomes possible to obtain an optical recording medium having high reflectance and high sensitivity.

Further, the thickness of the second recording layer is set to 200-50.
By setting it to 0Å, it was possible to achieve a reflectance that would allow ROM compatibility despite the medium having only two layers of recording film. Also, with a two-layer structure, high to
Since it is possible to record low, it has been possible to significantly reduce costs.

The ratio of Te and Sb of the second recording layer is Tex.
When Sb100-x, the composition is 10% in atm%.
It has been found that the diffusion efficiency of these two layers of recording films is improved and the environment resistance characteristics are improved because they are in the range of x <70. Here, if x is 10 atm% or less, the diffusion efficiency is lowered, and if 70% atm or more, the environmental resistance is deteriorated.

In order to further improve the environment resistance of the recording layer, one element selected from Pt, Co and Ni can be added to the second recording layer in an amount of 1 to 3 atm%.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Specific embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a configuration example of the present invention as a DVD, but the application of the present invention is not limited to a DVD. These are a first recording layer 2 and a second recording layer 3 on a transparent substrate 1.
Is deposited and the ultraviolet curable resin layer 4 is laminated. The cover substrate 5 and the cover substrate 5 are bonded together by an adhesive layer 6.

The material of the transparent substrate 1 is usually glass, ceramics, or resin, and a resin substrate is preferable in terms of moldability. Typical examples include polycarbonate, acrylic, epoxy, polystyrene, polypropylene, silicone, fluororesin, ABS, urethane, etc.
Polycarbonate resin is preferable from the viewpoints of workability and optical characteristics. In addition, the shape of the substrate is disk-shaped, card-shaped,
Alternatively, it may be in the form of a sheet.

Regarding the bonding method, radical U
The method is not particularly limited to any of the V method, the cation method, the heat seal method, and the double-sided adhesive sheet method, but in the configuration without the ultraviolet curable resin layer, a method that does not permeate oxygen and moisture like the radical UV method is desirable.

The recording layers 2 and 3 of the present invention are formed by various vapor phase growth methods,
For example, it can be formed by a vacuum vapor deposition method, a sputtering method, an electron beam method, or the like.

The structure of the present invention will be described below based on embodiments.

(Example) The structure of the present invention will be described with reference to FIG. 1 (in the case of DVD). Pitch 0.74 μm, with groove of depth 400A, thickness 0.6 mm, diameter Φ120 mm
The first recording layer 2 is formed on the polycarbonate resin information substrate 1 of 100 A, the second recording layer 3 is laminated on 400 A by the sputtering method, and the ultraviolet curable resin layer 4 is spin-coated thereon. It was formed by UV irradiation. The cover substrate 5 was attached by radical UV method. The evaluation conditions are a recording linear velocity of 3.5 m / s (1 × speed) and a linear density = 0.26.
7 μm / bit, recording laser wavelength 635 nm, NA =
The laser power is 0.6, and the laser power at which the reflectance and C / N are 55 dB or more when the second recording layer 3 has each composition is shown in Table 1 in comparison with the 1 × speed and the 2 × speed.
Also, ⊚ for those whose reflectance did not change at all at 85 ° C. 100H storage test ◯ for changes within 3% ○ for those showing 3% or more change
Is shown in the column of light resistance in the table.

[0026]

[Table 1]

In FIG. 2, the first recording layer 2 is represented by Ag (50, 1).
00, 200Å), the second recording layer 3 is In30Sb40
Taking the case of Te30 as an example, In30Sb40Te
The change in reflectivity when the film thickness of 30 is changed and the laser power showing a signal intensity of 55 dB or more at 1 × speed are shown. When the thickness of the second recording layer 3 is thin, the reflectance is low. Also, as shown in FIG. 3, if the film thickness is too thick (500
It can be seen that the recording power increases and the sensitivity deteriorates when the value exceeds Å. The recording here is a 3T rectangular wave recording.

[0028]

According to the present invention, the following excellent effects can be obtained. In an optical information recording medium which is composed of at least a transparent substrate, a first recording layer and a second recording layer and which can be recorded / reproduced by irradiation with an energy beam, the first recording layer is mainly made of Ag, The recording layer of is an alloy layer containing at least two kinds of elements Te and Sb, and the first recording layer and the second recording layer are mixed with each other by irradiation of light, and the optical constant can be changed. By using such an optical recording medium, it was possible to obtain an optical recording medium having high reflectance and sensitivity. That is, a thin film of silver having a high reflectance is formed on the laser irradiation side, an Sb-Te film is formed on the thin film, and the first recording layer and the second recording layer are mixed by irradiation of light to obtain a high film. The reflectance could be changed to to low.

Although the mechanism of this recording mechanism has not been elucidated accurately, one idea is that electrons generated by the absorption of light by the Sb-Te semiconductor forming the second recording layer are trapped in impurity levels and the like. It is considered that negative electrolysis is generated, and this attracts Ag +, which has become positive ions, to cause diffusion. Further, it is considered that the heat generation due to the absorption of light also enhances the diffusion effect. Note that Sb-In, In-
The same was true for Te and In-Sb-Te.

In the present invention, (the film thickness of the first recording layer) /
Since the (thickness of the second recording layer) is in the range of 0.1 to 1.0, the two characteristics of high reflectance and high sensitivity have been successfully achieved.

Further, the film thickness of the first recording layer is 50-200Å
Therefore, when Ag was used as the first recording layer, the reflectance was too high to absorb light and the thermal conductivity was too high to raise the temperature of the film. By setting the film thickness within the range, it becomes possible to obtain an optical recording medium having high reflectance and high sensitivity.

The film thickness of the second recording layer is set to 200-50.
By setting it to 0Å, it was possible to achieve a reflectance that would allow ROM compatibility despite the medium having only two layers of recording film. Also, with a two-layer structure, high to
Since it is possible to record low, it has been possible to significantly reduce costs.

The ratio of Te and Sb of the second recording layer is Tex.
When Sb100-x, the composition is 10% in atm%.
It has been discovered that when the range of x <70 is satisfied, the diffusion efficiency of these two layers of recording films is further enhanced and the environmental resistance characteristics are improved.
Here, if x is 10 atm% or less, the diffusion efficiency is lowered, and if 70% atm or more, the environmental resistance is deteriorated.

Further, one element selected from Pt, Co and Ni can be added to the second recording layer in an amount of 1 to 3 atm% in order to further improve the environment resistance of the recording layer.

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of an optical recording medium of the present invention.

FIG. 2 is a diagram showing the relationship between the thickness of the second recording layer and the reflectance.

FIG. 3 is a diagram showing the recording sensitivity showing the relationship between the layer thickness of the second recording layer and the recording power.

[Explanation of symbols]

1 transparent substrate 2 First recording layer 3 Second recording layer

Continued front page    F-term (reference) 2H111 EA03 EA12 EA21 EA33 EA37                       EA39 FA02 FB09 FB12 FB17                       FB23 FB30                 5D029 JA01 JB35

Claims (9)

[Claims] 1. In an optical information recording medium comprising at least a transparent substrate, a first recording layer and a second recording layer and capable of recording / reproducing by irradiation with an energy beam, the first recording layer is mainly made of Ag. , The second recording layer is at least T
An optical recording medium, which is an alloy layer containing two kinds of elements, e and Sb, wherein the first recording layer and the second recording layer are mixed with each other by irradiation of light, and the optical constant can be changed. 2. In an optical information recording medium comprising at least a transparent substrate, a first recording layer and a second recording layer and capable of recording / reproducing by irradiation with an energy beam, the first recording layer is mainly made of Ag. , The second recording layer is at least T
An optical recording medium, which is an alloy layer containing two kinds of elements, e and In, wherein the first recording layer and the second recording layer are mixed with each other by irradiation of light, and the optical constant can be changed. 3. An optical information recording medium comprising at least a transparent substrate, a first recording layer and a second recording layer and capable of recording / reproducing by irradiation with an energy beam, wherein the first recording layer is mainly made of Ag. , The second recording layer is at least I
An optical recording medium, which is an alloy layer containing two kinds of elements, n and Sb, wherein the first recording layer and the second recording layer are mixed with each other by irradiation of light, and the optical constant can be changed. 4. In an optical information recording medium comprising at least a transparent substrate, a first recording layer and a second recording layer and capable of recording / reproducing by irradiation with an energy beam, the first recording layer is mainly made of Ag. , The second recording layer is at least T
Optical recording, which is an alloy layer containing three kinds of elements of e, Sb, and In, wherein the first recording layer and the second recording layer are mixed with each other by irradiation of light, and the optical constant can be changed. Medium. 5. The optical recording medium according to claim 1, wherein (thickness of first recording layer) / (thickness of second recording layer) is 0.1-1.0. The optical recording medium is characterized in that 6. The optical recording medium according to claim 1, wherein the thickness of the first recording layer is 50 to 200Å. 7. The film thickness of the second recording layer is 200-500Å
The optical recording medium according to any one of claims 1 to 6, wherein 8. The ratio of Te and Sb of the second recording layer is Te
When xSb100-x, the composition is 10 atm%.
The optical recording medium according to claim 1, wherein the optical recording medium is in the range of <x <70. 9. The optical recording medium according to claim 1, wherein 1 to 3 atm% of one element selected from Pt, Co and Ni is added to the second recording layer. Optical recording medium.