JPH09330534A - Phase change-type optical information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a phase change-type optical information recording medium which has a high C/N ratio, a high erase ratio and an excellent repetition characteristic and whose time-dependent stability is high by a method wherein an Fe2 O3 film is used for a second dielectric layer which is formed so as to be separated from a substrate more than a first dielectric layer. SOLUTION: A first dielectric layer 102, a recording layer 103, a second dielectric layer 104, a reflecting layer 105 and a protective layer 106 are formed on a transparent substrate 101 in this order. That is to say, an Fe2 O3 film as the dielectric layer 104 is formed on the surface of the recording layer 103 in a film thickness in a range of 20 to 60nm, and the dielectric layer 104 is formed by an RF sputtering method in an Ar atmosphere by using an Fe2 O3 target. Then, a temperature and humidity acceleration test is performed, for many hours, to a phase change-type optical information recording medium whose C/N ratio characteristic and erase ratio characteristic are excellent and in which the Fe2 O3 film and an AlN film are used for the dielectric layers. Thereby, the recording film 103 is not stripped from the dielectric layer 104. Then, the medium has a high C/N ratio, a high erase ratio and an excellent repetition characteristic, and it has a high time-dependent stability.

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, and more particularly, it is capable of recording, reproducing and erasing information by causing a phase change in a recording layer material by irradiating a light beam. The present invention relates to a possible phase change type optical information recording medium.

[0002]

2. Description of the Related Art In recent years, a large amount of rewritable optical discs, which replaces floppy discs, are in an important position as society as a whole is rapidly moving to multimedia. Well-known rewritable optical disks are a magneto-optical disk that uses a perpendicular magnetization film as a recording layer and a phase change optical disk that uses a material that causes a crystal phase-amorphous phase or a crystal-crystal transition in the recording layer. There is.

Since the phase change type optical disk can be overwritten by a single light beam, and the optical system on the drive side may have a simpler structure, its research and development has recently become more active. In particular, rewritable compact discs (CD-E: Compact Disk-Erasable) and rewritable digital video discs (DVD-RAM: Digital Video Dirasable).
Application to sk-Read After Memory) is expected.

As typical examples of the materials used for the recording layer of the phase change optical disk, the GeTeSb-based materials disclosed in JP-A-61-89889 and JP-A-1-32438 and JP-A-6-988 are disclosed. There is an AgInSbTe-based material disclosed in JP-A-333266.

Further, in an actual optical disc, a recording layer is sandwiched between dielectric layers to prevent deterioration due to repeated overwriting, and a difference in reflectance (modulation degree) between a recorded portion and an unrecorded portion is utilized by utilizing an interference effect. It is common to improve the reproduction characteristics.

The phase change type optical disk disclosed in the above-mentioned Japanese Patent Laid-Open No. 6-333266 has a ZnS-SiO ₂ film as a first dielectric layer on the upper surface of a transparent substrate,
AgInSbTe film as a recording layer is provided on the upper surface of the dielectric layer, and AlN, S as a second dielectric layer is provided on the upper surface of the recording layer.
A film using any one of i ₃ N ₄ , C—BN, SiO ₂ and ZnS—SiO ₂ is provided, and further, a second
On the upper surface of the dielectric layer, a structure using any one material of Ag, Au, Al and Al-Ti is used as a reflective layer.

[0007]

However, the above-mentioned second problem
In the material used for the dielectric layer of AlN, Si ₃
Since metal nitride films such as N ₄ and C-BN have high hardness,
Although it is possible to obtain a high erasing ratio of -35 dB or more, the adhesion to the recording film is not sufficient, cracks may occur due to warpage or twisting of the disc, and peeling from the recording film may occur during long-term storage. There was a problem that was likely to occur.

Further, although SiO ₂ and ZnS-SiO ₂ have high adhesion to the recording film, they have a problem that the erasing ratio is as low as -25 dB or less and the repeating characteristics are inferior to the metal nitride film. .

Therefore, there is a trade-off relationship between obtaining a high erase ratio and obtaining a high stability over time.

[0010]

In order to solve the above problems, the invention according to claim 1 of the present invention is a transparent substrate which transmits a light beam, and a first dielectric provided on the upper surface of the transparent substrate. Layer, a recording layer provided on the upper surface of the first dielectric layer, which causes a reversible state change between a crystalline phase and an amorphous phase by irradiation of a light beam, and a second recording layer provided on the upper surface of the recording layer. A phase change type optical information recording medium comprising a dielectric layer and a reflection layer provided on the upper surface of the second dielectric protection layer and reflecting a part of a light beam to the recording layer side. The body layer is Fe ₂ O ₃ .

The invention according to claim 2 of the present invention is the phase-change optical information recording medium according to claim 1, wherein the first dielectric layer is a ZnS-SiO film having a film thickness of 110 to 150 nm.
₂ and the recording layer is made of AgInS having a thickness of 20 to 40 nm.
bTe and the second dielectric layer has a thickness of 15 to 35 nm
Fe ₂ O ₃ and the reflective layer is Al having a film thickness of 60 to 100 nm.

According to the first aspect of the present invention, the material of the second dielectric layer is made of a metal oxide having a high mechanical strength and an adhesion property to the recording film rather than the metal nitride film. Since Fe ₂ O ₃ is high, it is possible to obtain a phase change type optical information recording medium having a high erasing ratio and excellent stability over time.

According to the second aspect of the present invention, a high CNR can be obtained because a high erasing ratio can be obtained, the stability with time is excellent, and the contrast of the recording signal can be made large.
It is possible to obtain a phase change type optical information recording medium that can obtain (Carrier to Noise Ratio).

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below with reference to the drawings and tables. FIG. 1 is a schematic view showing the cross-sectional structure of an embodiment of the phase change type optical information recording medium of the present invention. Transparent substrate 101 made of polycarbonate resin having a diameter of 120 mm (groove width = 0.5 μm, groove depth = 60
nm) and ZnS-S as the first dielectric layer 102.
The iO ₂ film was formed by changing the film thickness in the range of 20 nm to 220 nm for each sample. Deposition of the first dielectric layer 102, using a ZnS-SiO ₂ target was performed by RF sputtering in an Ar atmosphere.

An AgInSbTe film is formed as a recording layer 103 on the upper surface of the first dielectric layer 102 in a thickness of 20 nm for each sample.
To a film thickness of The recording layer 103 was formed by RF sputtering in an Ar atmosphere using a target adjusted so that the composition of the recording layer was Ag _{1 2} In _{1 3} Sb _{2 6} Te _{4 9} .

The second dielectric layer 1 is formed on the upper surface of the recording layer 103.
As No. 04, an Fe ₂ O ₃ film was formed by changing the film thickness in the range of 20 nm to 60 nm for each sample. The second dielectric layer 104 was formed by an RF sputtering method using an Fe ₂ O ₃ target in an Ar atmosphere.

On the upper surface of the second dielectric layer 104, an Al film having a thickness of 60 nm was formed as a reflective layer 105. The reflective layer was formed by RF sputtering in an Ar atmosphere using an Al target.

The protective layer 1 is formed on the upper surface of the reflective layer 105.
As No. 06, an ultraviolet curable resin was applied and formed by spin coating so as to have a film thickness of 5 μm, and was irradiated with ultraviolet rays to be cured to form a film.

As described above, the first dielectric layer 102
And several types of phase-change optical information recording media manufactured by changing the film thickness of the second dielectric layer 104, the initialization was performed at a wavelength of 7
Using a semiconductor laser of 80 nm, laser output 6 mW,
Continuous irradiation was performed at a linear velocity of 1.2 m / s.

Next, for each initialized phase-change optical information recording medium, a semiconductor laser having a wavelength of 780 nm was used to obtain a laser output of 13 mW and a linear velocity of 1.2 m / s.
At a recording frequency of 720 kHz and a duty of 50%, and a frequency of 200 kHz and a duty of 5%.
The ratio (contrast) of the reflectance of the recorded portion to the reflectance of the unrecorded portion of the signal having a frequency of 200 kHz when 0% signal was recorded and overwrite was performed was measured.

FIG. 2 is a characteristic diagram showing the dependence of contrast on the film thickness of the first dielectric layer and the second dielectric layer. As can be seen from FIG. 2, Zn that is the first dielectric layer 102
The S-SiO ₂ film has a thickness of 110 to 150 nm, and the Fe ₂ O ₃ film as the second dielectric layer 104 has a thickness of 15 to 35.
In the range of nm, a large contrast of 0.6 or more can be obtained.

Further, Ag _{1 2} In _{1 3} S, which is the recording layer 103, is used.
Similar results were obtained when the thickness of the b _{2 6} Te _{4 9} film was changed in the range of 20 to 40 nm and the thickness of the Al film as the reflective layer 105 was changed in the range of 60 to 120 nm.

However, when the film thickness of the recording layer 103 is set to a film thickness other than the above range, the contrast is lowered as a whole, and a contrast of 0.6 or more cannot be obtained. Further, when the film thickness of the reflective layer 105 is set to 60 nm or less, the reflectance of the Al film is low, so that the contrast is lowered, and when the film thickness is set to 120 nm or more, the heat dissipation effect becomes too large. And the erasing property is deteriorated.

Next, the recording layer 1 having a film thickness of 120 nm of the first dielectric layer 102 having a contrast of 0.6 or more.
03 has a thickness of 20 nm, and the second dielectric layer 104 has a thickness of 25
C / N (Carr (Carr) of a 200 kHz signal of a phase-change optical information recording medium having a structure in which the thickness of the reflective layer 105 is 60 nm).
ier to Noise ratio) and erase ratio were measured. In addition, as a comparative example, the second dielectric layer 104 has a thickness of A of 20 nm.
The C / N and the erasure ratio of the 200 kHz signal were also measured for the phase change type optical information recording medium having a structure of 1N and a film thickness of 20 nm of ZnS—SiO ₂ . The results are shown in Table 1.

[0025]

[Table 1]

As can be seen from Table 1, the second dielectric layer 1
No change was observed in the characteristics repeated 10 ⁵ times in any of 04 types of materials. However, when ZnS—SiO ₂ is used for the second dielectric layer 104, the C / N and erase ratio characteristics are inferior to the other two materials.

Next, with respect to the phase change type optical information recording medium using the Fe ₂ O ₃ film and the AlN film as the second dielectric layer 104, which has excellent C / N and erasing ratio characteristics, stability over time is obtained. Linear velocity 1.2m / s, laser power 13m
Record the EFM signal using the multi-pulse method with W, 7
The change in block error when the temperature and humidity acceleration test at 0 ° C. and 85% RH was performed was measured. FIG. 3 is a characteristic diagram showing the results of the temperature and humidity acceleration test.

As is apparent from FIG. 3, the layer change type optical information recording medium using the Fe ₂ O ₃ film as the second dielectric layer 104 of the present invention is effective even after a long time temperature and humidity acceleration test. It was found that peeling did not occur between the recording film 103 and the second dielectric layer 104, and the stability over time was superior to that using the conventional AlN film.

[0029]

As described above, the phase change type optical information recording medium using the Fe ₂ O ₃ film for the _second dielectric layer of the present invention has a high C content.
/ N, a high erasing ratio and excellent repeatability, and high stability over time.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a cross-sectional structure of an embodiment of a phase change optical information recording medium of the present invention.

FIG. 2 is a characteristic diagram showing the film thickness dependence of the ratio (contrast) of the reflectance of the recorded portion to the reflectance of the unrecorded portion in the first dielectric layer and the second dielectric layer.

FIG. 3 is a characteristic diagram showing the results of a temperature and humidity acceleration test.

[Explanation of symbols]

 101 Transparent Substrate 102 First Dielectric Layer 103 Recording Layer 104 Second Dielectric Layer 105 Reflective Layer 106 Protective Layer

Claims (2)

[Claims] 1. A transparent substrate that transmits a light beam, a first dielectric layer provided on the upper surface of the transparent substrate, and a crystal provided by irradiation of the light beam provided on the upper surface of the first dielectric layer. A recording layer that causes a reversible state change between a phase and an amorphous phase; a second dielectric layer provided on the upper surface of the recording layer; and a second dielectric layer provided on the upper surface of the second dielectric protective layer, A phase change type optical information recording medium comprising a reflection layer for reflecting a part of a light beam to the recording layer side, wherein the second dielectric layer is Fe ₂ O ₃ Optical information recording medium. 2. The phase-change optical information recording medium according to claim 1, wherein the first dielectric layer is a Zn film having a thickness of 110 to 150 nm.
S-SiO ₂ , and the recording layer is made of AgInSbTe having a thickness of 20 to 40 nm.
And the second dielectric layer is made of Fe ₂ O _{3 having} a thickness of 15 to 35 nm.
The phase change type optical information recording medium, wherein the reflective layer is Al having a film thickness of 60 to 100 nm.