JP2003059102A - Phase change type optical information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical information recording medium which is a phase transition optical information recording medium using a protective film of Al2 O3 , solves the problem of its overwriting characteristic and permits a high density and high transfer rate. SOLUTION: A rear earth oxide is added to the protective film of the optical information recording medium having a recording film capable of recording information by a phase transition between a crystalline state and an amorphous state by incidence of light and the protective film consisting of the Al2 O3 .

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 which records or reproduces information by a phase change between a crystalline state and an amorphous state by a laser beam or the like, and more particularly has a high density and a high transfer rate. The present invention relates to a phase-change type information recording medium capable of recording.

[0002]

2. Description of the Related Art Optical disks such as CD-R and CD-RW are provided with a recording layer on a circular substrate made of plastic such as polycarbonate, and a metal such as aluminum, gold or silver is vapor-deposited or sputtered on the recording layer to be reflected. A layer is formed and laser light is incident from the substrate surface side to record and reproduce signals. Since the amount of information handled by computers has increased in recent years, DVD-RAM, DVD
-Increasing the signal recording capacity of optical discs such as RW and increasing the density of signal information are progressing.

While the recording capacity of a CD is about 650 MB, the capacity of a DVD is about 4.7 GB,
In the future, higher recording density and higher transfer rate will be required. In order to realize such a high recording density medium,
It has been proposed to shorten the laser wavelength used to the blue light region. Further, by increasing the numerical aperture of the objective lens used in the pickup for recording / reproducing, the spot size of the laser beam irradiated on the optical recording medium can be reduced, and high recording density can be achieved. Further, as an optical disk capable of high transfer rate, an optical disk using an Al ₂ O ₃ protective film has been announced (Proc. Of
PCOS2000. 65 (2000)). It has been reported that a high transfer rate is possible by using Al ₂ O ₃ having a relatively high thermal conductivity. However,
The optical disk using this Al ₂ O ₃ has a problem in overwrite characteristics.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above background, and in the phase change type optical information recording medium using the Al ₂ O ₃ protective film, solves the problem of the above overwrite characteristics, An object of the present invention is to provide an optical information recording medium having a high density and a high transfer rate.

[0005]

As a result of intensive studies to solve the above problems, the present inventor has found a phase change type information recording medium which meets the above object. That is, according to the present invention, firstly, in claim 1, a recording film capable of recording information by a phase change between a crystalline state and an amorphous state by incidence of light and a protective film made of Al ₂ O ₃ are provided. An optical information recording medium having the phase change type optical information recording medium, characterized in that a rare earth oxide is added to the protective film.

Secondly, in the second aspect, in the phase change type optical information recording medium according to the first aspect, the rare earth oxide is
There is provided a phase change type optical information recording medium, which is any one of La ₂ O ₃ , Y ₂ O ₃ , and Lu ₂ O ₃ or a mixture thereof.

Thirdly, in the third aspect, in the phase change type optical information recording medium according to the first or second aspect, the amount of the rare earth oxide added is 0.03 to 0.2 mol%. Provided is a phase change type optical information recording medium.

Fourthly, in the fourth aspect, in the phase change type optical information recording medium according to any one of the first to third aspects, it is formed on the front side of the recording film as seen from the light incident side. Provided is a phase change type optical information recording medium, wherein the protective film has a thickness of 30 to 170 nm.

Fifth, in the fifth aspect, in the phase change type optical information recording medium according to any one of the first to fourth aspects, it is formed on the inner side of the recording film when viewed from the light incident side. There is provided a phase change type optical information recording medium, wherein the thickness of the protective film is 5 to 50 nm.

Sixth, in the sixth aspect, in the phase change type optical information recording medium according to any one of the first to fifth aspects, the recording film contains an Sb-Te eutectic alloy as a main component. A phase change type optical information recording medium is provided.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The optical information recording medium of the present invention will be described in detail below. FIG. 1 is a schematic sectional view of an optical information recording medium according to an embodiment of the present invention. The substrate 1 has a structure in which a lower protective film 2, a recording film 3, an upper protective film 4, a reflective heat radiation film 5, and an overcoat layer 6 are sequentially accumulated.

The material of the substrate 1 is usually glass, ceramics or resin, and a resin substrate is suitable in terms of moldability and cost. Examples of the resin include polycarbonate resin, acrylic resin, epoxy resin, polystyrene resin,
Acrylonitrile-styrene copolymer resin, polyethylene resin, polypropylene resin, silicone resin, fluorine resin, ABS resin, urethane resin and the like can be mentioned, but polycarbonate resin and polymethylmethacrylate excellent in moldability, optical characteristics and cost. Acrylic resins such as (PMMA) are preferred. An uneven pattern such as a guide groove is formed on the substrate 1, and the substrate 1 is molded by injection molding or a photopolymer method. The thickness of the substrate is not particularly limited.

The material of the recording film 3 is a Ge--Te system,
Although chalcogen alloy thin films such as Ge-Te-Sb system and Ge-Sn-Te system are often used, the Sb-Te eutectic system thin film has very good recording (amorphization) sensitivity / speed and erase ratio. Therefore, it is suitable as a material for the recording film. Other elements or impurities such as Ag, In and Ge can be added to these recording film materials for the purpose of further improving performance and reliability. The recording film using an inorganic material can be formed by various vapor phase growth methods such as vacuum deposition method, sputtering method, plasma CVD method, photo CVD method, ion plating method and electron beam evaporation method. Among them, the sputtering method is excellent in mass productivity and film quality.

As the reflection / heat radiation film 5, Al, Au, A
A metal material such as g, Cu, Ta, or an alloy thereof can be used. Further, as an additive element, C
r, Ti, Si, Cu, Ag, Pd, Ta or the like is used. Such a reflective heat dissipation film can be formed by various vapor deposition methods such as vacuum deposition method, sputtering method and plasma CVD method.
Method, photo CVD method, ion plating method, electron beam evaporation method, or the like. Among them, the sputtering method is excellent in mass productivity and film quality. Reflective heat dissipation film 5
Has a thickness of 50 to 200 nm, preferably 80 to 150 nm
It is good to say When the thickness is less than 50 nm, the reflectance is low, and when the thickness is more than 200 nm, the sensitivity is lowered.

As the lower protective film 2 and the upper protective film 4, A
A material consisting of l ₂ O ₃ and a trace amount of rare earth oxide is used. A
With l ₂ O ₃ alone, there arises a problem that the characteristics during overwriting deteriorate. It is known that the addition of a trace amount of rare earth oxide to Al ₂ O ₃ causes the rare earth ions to segregate at the grain boundaries of Al ₂ O ₃ to improve the creep resistance. Generally, in recording on a phase-change type optical disk, a large amount of energy is applied to the recording film because the recording film is melted by laser light irradiation and is rapidly cooled to form an amorphous mark. In order for the characteristics after overwriting to be about the same as those after one-time writing, the protective film adjacent to the recording film is difficult to deform even if energy is applied, that is, it has excellent creep resistance. Is considered desirable. From such a viewpoint, the present inventors have found that an optical disc using this material as a protective film was manufactured and evaluated, and as a result, deterioration of characteristics during overwriting was suppressed. La ₂ O ₃ , Y ₂ O ₃ , L as rare earth oxides
u ₂ O ₃ is effective in improving overwrite. The amount of the rare earth oxide added is preferably 0.03 to 0.2 mol%. If it is less than 0.03 mol%, the effect of the present invention cannot be obtained. If it is more than 0.2 mol%, the thermal conductivity will change and high density recording will be difficult. The thickness of the lower protective film 2 is 3
The thickness is preferably 0 to 170 nm. When the thickness is less than 30 nm, heat may affect the substrate when recording, and the substrate may be deformed. On the other hand, if the thickness is more than 170 nm, it becomes difficult to manufacture an optical disc having excellent mass productivity. The thickness of the upper protective film 4 is 5 to 50 nm, preferably 7
It is preferable that the thickness is ˜30 nm. When it becomes thicker than 50 nm,
Repeated recording performance deteriorates. When the thickness is less than 5 nm, the function as a protective film cannot be achieved. Such a protective film can be formed by various vapor phase growth methods such as vacuum deposition method, sputtering method, plasma CVD method, photo CVD method, ion plating method and electron beam evaporation method. Among them, the sputtering method is excellent in mass productivity and film quality.

[0016]

EXAMPLES Next, the present invention will be described in more detail by way of examples. However, the present invention is not limited to the following examples.

Examples 1-3 and Comparative Examples 1-2 It has a diameter of 12 cm and a thickness of 0.6 mm.
On polycarbonate substrate with unevenness of racking guide
ZnS-SiO as a lower protective film₂Is 100 nm
Ag as a recording film₁In₇Sb₇₀Te_{twenty two}6 nm, top protection
As the film, Al ₂O₃To Y₂O₃0.05 mol% was added
20 nm, and AlTi 140 n as a reflection and heat dissipation film.
m was sequentially formed into a film. The film formation method is a spa in Ar gas atmosphere.
This is the Tatta method. Also, with the same structure, as the upper protective film
Al₂O₃To La₂O₃Containing 0.05 mol% of
And as an upper protective film, Al₂O₃To Lu₂O₃To 0.0
A film added with 5 mol% was formed. On top of that, Spinco
Phase change type optical data
I made a disk. Then, a large-diameter semiconductor laser
Initialization of the recording layer of the disc by the initialization device that has
Processed. As a comparative example, the upper protective film is
Al each₂O₃, ZnS-SiO₂A disc with
It was made. Each of the produced discs is described under the following conditions.
I recorded it. Laser wavelength: 407 nm, NA = 0.65,
Linear velocity: 13 m / s, track pitch: 0.40 μm, line
Optimal recording sensitivity and jitter at a density of 0.18 μm / bit
-, And the jitter after recording 10,000 times was measured.
As shown in Table 1 for each media, the light according to the example
After the disc has been recorded once and 10,000 times,
It is clear that the target is low and excellent.

[0018]

[Table 1]

Examples 4 to 6 and Comparative Example 3 An optical disk was manufactured in the same manner as in Example 1 except for the upper protective film and the lower protective film. Example 4 was used as the lower protective film.
6, respectively, 100 nm and film doped Y ₂ O ₃ and 0.05 mol% to Al ₂ O _3, the Al ₂ O ₃ and La ₂ O ₃ 0.05
The film added with mol% is 100 nm, and Al ₂ O ₃ is added with Lu ₂ O ₃
A film having a thickness of 100 nm was prepared by adding 0.05 mol% of. As Comparative Example 3, 100% Al ₂ O ₃ was used for the lower protective film.
nm was produced. Examples of the upper protective film include
In both comparative examples, ZnS—SiO ₂ having a thickness of 20 nm was used. Table 2 shows the results of evaluation performed in the same manner as in Example 1. As can be seen from this, it is clear that the optical discs according to the examples are excellent in that the jitter after recording 10,000 times is low.

[0020]

[Table 2]

Examples 7 to 9 and Comparative Examples 4 to 5 Optical discs were manufactured in the same manner as in Example 1 except for the upper protective film. For the upper protective film, Al ₂ O ₃ and Y ₂ O ₃ were added to 0.03, 0.1 and 0.2 mol%, respectively, to have a thickness of 20 nm. As a reference example, Al ₂ O ₃
A disk was prepared by laminating 0.01 to 0.3 mol% of Y ₂ O ₃ on the disk. The optical disk thus manufactured was evaluated in the same manner as in Example 1. The results are shown in Table 3, and it is clear that the optical disks according to the examples are excellent. FIG. 2 is a graph showing the relationship between the amount of Y ₂ O ₃ added and the jitter after recording once and 10,000 times, including the results of other trial experiments. As can be seen from this figure, the amount of rare earth oxide added is 0.03 to
Good results were obtained in the range of 0.2 mol%.

[0022]

[Table 3]

Examples 10 to 14 and Comparative Examples 6 to 7 Optical discs having the same layer structure as in Example 1 except for the upper protective film were prepared. The upper protective film is made of Al ₂ O ₃ and Y ₂ O ₃
Was added in an amount of 0.05 mol%, and film thicknesses of 5, 10, 30, 40, and 50 nm were prepared. As a reference example, a film having a film thickness of 3, 60 nm was also manufactured. The optical disk thus manufactured was evaluated in the same manner as in Example 1. The results are shown in Table 4. It was found that good results were obtained in the range of 5 to 50 nm for the upper protective film, and that if the thickness was thinner than that, the sensitivity was poor, and if it was thicker, the jitter after recording 10,000 times deteriorated.

[0024]

[Table 4]

Examples 15 to 18 and Comparative Examples 8 to 9 Optical discs having the same layer structure as in Example 4 except for the lower protective film were prepared. The lower protective film includes Al ₂ O ₃ and Y ₂ O ₃
Was added in an amount of 0.05 mol%, and film thicknesses thereof were 30, 50, 100 and 170 nm, respectively. As a reference example, a film having a film thickness of 25 and 180 nm was manufactured. The optical disc manufactured in this manner was used in Example 4.
Evaluation was performed in the same manner as in. The results are shown in Table 5. Good results were obtained for the lower protective film in the range of 30 to 170 nm. If it is thinner than 30 nm, the jitter after recording 10,000 times is deteriorated, and if it is thicker than 170 nm, the characteristics as an optical disk are good, but it is not preferable in terms of tact at the time of production and cost.

[0026]

[Table 5]

[0027]

As described above, according to the first aspect of the present invention, since the rare earth oxide is added to the protective film made of Al ₂ O ₃ , the characteristics at the time of overwriting are excellent and the density is high. An optical information recording medium capable of high transfer rate can be obtained.

According to the second aspect of the invention, since the rare earth oxide is specified as described above, it is possible to more effectively obtain the optical information recording medium having excellent overwrite characteristics.

According to the third aspect of the present invention, since the amount of the rare earth oxide added is specified as described above, it is possible to obtain an optical information recording medium having good sensitivity and good overwrite characteristics.

According to the fourth aspect of the present invention, since the thickness range of the lower protective film made of Al ₂ O ₃ to which the rare earth oxide is added is specified as described above, the recording characteristics are good and the mass productivity is good. An optical information recording medium can be obtained.

According to the invention of claim 5, the upper protective film made of Al ₂ O ₃ to which a rare earth oxide is added has a film thickness range specified as described above. It is also possible to obtain an excellent optical information recording medium.

According to the sixth aspect of the present invention, since the constituent elements of the recording layer are specified as described above, it is possible to obtain an optical information recording medium having an excellent erasing ratio and good overwriting characteristics.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of an optical information recording medium showing an example of the present invention.

FIG. 2 is a graph showing the relationship between the amount of rare earth oxide added and jitter.

[Explanation of symbols]

1 substrate 2 protective film 3 recording film 4 Upper protective film 5 Reflective heat dissipation film 6 Overcoat layer

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2H111 EA04 EA23 EA31 FA14 FA25                       FB09 FB12                 5D029 JA01 JB18 LA14 LA19 LB07

Claims (6)

[Claims] 1. An optical information recording medium having a recording film capable of recording information by a phase change between a crystalline state and an amorphous state upon incidence of light and a protective film made of Al ₂ O ₃ , wherein the protective film contains a rare earth element. A phase-change type optical information recording medium characterized by adding an oxide. 2. The phase change type optical information recording medium according to claim 1, wherein the rare earth oxide is La ₂ O ₃ , Y ₂ O ₃ or Lu _2.
A phase-change type optical information recording medium characterized by being any one of O ₃ and a mixture thereof. 3. The phase-change optical information recording medium according to claim 1, wherein the amount of rare earth oxide added is 0.03.
A phase change type optical information recording medium, characterized in that the content is ˜0.2 mol%. 4. The phase-change optical information recording medium according to claim 1, wherein the protective film formed on the front side of the recording film has a thickness of 30 to 30 when viewed from the light incident side. 170
A phase-change type optical information recording medium characterized by having a thickness of nm. 5. The phase change type optical information recording medium according to claim 1, wherein the protective film formed on the inner side of the recording film has a thickness of 5 to 5 when viewed from the light incident side. A phase change type optical information recording medium having a thickness of 50 nm. 6. The phase-change optical information recording medium according to claim 1, wherein the recording film contains an Sb—Te eutectic alloy as a main component. Information recording medium.