JP2001035009A - Optical information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical information recording medium in which the reloadable number of times is increased for the purpose of using it as a high density disk in the coming generation or the like. SOLUTION: A phase transition type optical information recording medium having a first dielectric layer 2, a recording layer 3, a second dielectric layer 4, a reflecting layer 5 and a protective layer 6 laminated on a substrate 1 in this order comprises SiON (sialon) used in any of the first dielectric layer 2 and the second dielectric layer 4 or in the both and in a part or all of each dielectric layer.

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, to a phase change type optical information recording / reproducing and rewritable information recording / reproducing irradiating a laser beam with a recording layer. It relates to a recording medium.

[0002]

2. Description of the Related Art As one of optical information recording media capable of recording, reproducing and erasing information by irradiating an electromagnetic wave, particularly a laser beam, a so-called phase utilizing a transition between a crystal and an amorphous phase or between a crystal and a crystal phase. A variable optical information recording medium is known. In particular, since overwriting with a single beam, which is difficult with a magneto-optical recording medium, is possible and the optical system on the drive side is simpler, research and development thereof have been actively conducted in recent years.

[0003] For example, an information recording medium using GeSbTe as a phase change recording type information recording medium (Japanese Patent Laid-Open No. 5-62193).
And those using AgInSbTe (JP-A-11-11531)
3) etc. are used. However, none of them can satisfy all of the properties required for a phase-change optical information recording medium. In particular, the biggest problem of these phase change type information recording media is that the number of rewritable times is smaller than that of the magneto-optical method (overwrite characteristics are poor). In order to improve the overwrite characteristics, the material of the dielectric layer is limited (Japanese Patent No. 286).
No. 5775). Conventionally, ZnS—SiO 2 (20 mol%) has been used as the dielectric layer.

[0004]

Among phase change type information recording media, AgInSbTe is used for a rewritable compact disc (CD-RW) because of its good erasing rate and the like. However, there is a drawback that the number of rewritable times is as small as about 1000 times, and improvement in increasing the number of rewritable times is the most important issue for use in next-generation high-density discs (video disk recorders) and the like.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has a first dielectric layer 2, a recording layer 3, a second dielectric layer 4, a reflective layer 5, a protective layer 5 on a substrate 1. In the optical information recording medium 10 of the phase change type in which the layers 6 are laminated in this order, one or both of the first dielectric layer 2 and the second dielectric layer 4 and a part of each dielectric layer Alternatively, an optical information recording medium 10 entirely using SiON (Sialon) is provided.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the optical information recording medium according to the present invention will be described in detail with reference to the drawings. Before that, the background that led to the present invention will be described. In the phase change type information recording, it is necessary to protect the recording layer with a high melting point protective layer in order to at least partially dissolve the recording layer during recording. In addition, another item required for the dielectric layer is that the dielectric layer be transparent in the used wavelength region.
Have appropriate thermal constants (thermal conductivity, specific heat). Etc. are required. Due to such demands, ZnS-SiO2 (20 mol%) has been generally used as a dielectric layer used above and below the recording layer because of its good characteristics.

[0007] However, the conventional one using ZnS-SiO2 for the dielectric layer and using AgInSbTe for the recording layer has a practical problem that the number of rewritable times (direct overwrite, DOW) is as small as about 1000 times. . In order to improve the DOW characteristics, as described in Japanese Patent No. 2865775, it is good to use a material mainly composed of an oxide as the dielectric layer, but the amount of oxygen is too large. In this case, the recording layer is oxidized and the reliability is lowered.

Therefore, as an item required for the dielectric layer in order to improve the DOW characteristics, it is better that the thermal conductivity is large enough not to lower the sensitivity. The thermal expansion coefficient is preferably as small as the recording layer. The thing which can control oxygen concentration moderately is good. Therefore, the inventors focused on SiON (SiAlON) which has been conventionally used for the protective layer of the thermal printer head, and examined it.

FIG. 1 shows an optical information recording medium 10 according to the present invention.
FIG. 2 is a schematic configuration diagram showing a first embodiment of the present invention, and FIG. 2 is a schematic configuration diagram showing a second embodiment of the optical information recording medium 10 according to the present invention. In both figures, the optical information recording medium 10
Denotes a substrate having an optically smooth surface 1, a first dielectric layer 2 covering the surface of the substrate 1, a light absorbing recording layer 3 covering the surface of the first dielectric layer 2, and a recording layer 3 3, a second dielectric layer 4 covering the surface 3, a reflective layer 5 covering the surface of the second dielectric layer 4, and a protective layer 6 covering the surface of the reflective layer 5.

As the substrate 1, a polycarbonate resin (PC) molded substrate having a continuous groove having a thickness of 0.6 mm and a track pitch of 0.74 μm was used. The signal is 8
A / 16 modulated signal was evaluated as a recording / reproducing signal at a linear velocity of 3.5 m / sec and a channel bit rate of 26.16 Mbps.

As the first dielectric layer 2, ZnS-Si
O2 is formed by an RF sputtering method and has a thickness of 75 nm. Similarly, the second dielectric layer 4 is made of ZnS-SiO2 by RF.
The film is formed by a sputtering method and has a thickness of 15 nm. In addition,
In the present embodiment, the second dielectric layer 4 is made of SiON.
(Sialon).

As a method of forming a SiON film, a method of introducing an Ar gas or N2 gas using a SiON target to form a film by an RF sputtering method, or a method of introducing an Ar gas, N2 gas, or O2 gas using a Si target. There is a method of forming a film by a DC sputtering method, but either method may be used. In this example, the film was formed by the DC sputtering method. The film formation pressure was 0.6 Pa, and the gas flow rate was Ar = 2.
A mixture of 0 sccm, N2 = 3 sccm and O2 = 3 sccm is used, and the DC power is 0.4 A-600 V
(240 W), and the film formation rate was 2.5 ° / sec. The refractive index of SiON is 1.45 and the extinction coefficient is 0.0
It was 2.

As the recording layer 3, Ag,
Some include In, Sb, and Te, and others include In, Sb, and Te, and are composed of ternary or more ternary compounds. In addition, as the recording layer 3, there is a recording layer 3 which exhibits a reversible structural change between a crystal and a crystal phase, such as a Cu-Al-based alloy and an Ag-Zn-based alloy. Sets the composition ratio (atom%) of Ag, In, Sb, and Te to, for example, 2: 8: 59: 31. In this example, the composition was performed at this composition ratio, but the composition ratio is not necessarily limited to this range.

As the reflection layer 5, an Al alloy containing 1.5% by weight of TI is used. Further, as the protective layer 6, an ultraviolet curable resin is used, and after the application of the ultraviolet curable resin, it is cured by irradiating ultraviolet rays.

[0015] ZnS-SiO2 was formed by the RF sputtering method, and compared with the present invention, the DOW characteristics were compared to examine whether or not there was any effect. The thickness of each of the first dielectric layers 2 is 7
5 nm, the recording layer 3 is 22 nm, and the second dielectric layer 4 is 15 n
m, the reflective layer 5 was basically 150 nm. As a conventional example, ZnS-SiO2 was used for all the dielectric layers, and Ag2In8Sb59Te31 at% was used for the recording layer composition.

[0016]

EXAMPLE 1 First, it was examined whether the DOW characteristics could be improved when the second dielectric layer 4 was changed to SiON. Since the refractive index of SiON was 1.45, the optical film thickness was set to standard ZnS-SiO2.
(The refractive index of ZnS-SiO2 is 2.15 and the film thickness is 15n
m, the optical film thickness is nd = 2.15 * 15 = 3
2.25), the film thickness was set to 24 nm (nd =
1.45 * 24 = 34.8). As an evaluation method, evaluation was made by the values of the leading edge jitter (LE) and the trailing edge jitter (TE) in the case of groove recording, with both adjacent recordings. (The jitter is a value obtained by normalizing the σ of the jitter from the data edge at which the conversion point of the original signal is temporally advanced or delayed to the PLL clock when reproducing the mark recorded on the optical disc by 1T. ). The result is as shown in FIG. According to FIG. 3, the conventional one has a large jitter value after 2000 rewrites, but the present invention has
Less degradation and 10% jitter value after 1000 rewrites
The table is kept and it can be seen that it can withstand actual use.

[0017]

Embodiment 2 FIG. 4 shows the result of studying the case where a part of the second dielectric layer 4 and the first dielectric layer 2 is made of SiON. Initial jitter is slightly lower than standard, but 1000 and 200
Even if the number of times of rewriting is zero, the jitter is not deteriorated at all, and a good result is obtained. When the first dielectric layer 2 was entirely made of SiON, both initial jitter and DOW characteristics were not so good. Usually, a part of the first dielectric layer 2 means that the thickness of the first dielectric layer 2 is 75 nm for ZnS-SiO2, but in the present invention, a 25 nm SiON film is formed from the substrate 1 side. , And ZnS-Si on it
O2 was deposited to a thickness of 50 nm. This was used as the first dielectric layer 2, and the second dielectric layer 4 was also changed from ZnS-SiO2 to SiON.

[0018]

According to the present invention, by using a dielectric layer of SiON, an optical information recording medium having 1000 stable rewritable times without any jitter deterioration can be provided. It can respond to high density.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a first embodiment of an optical information recording medium 10 according to the present invention.

FIG. 2 is a schematic configuration diagram showing a second embodiment of the optical information recording medium 10 according to the present invention.

FIG. 3 is a diagram illustrating jitter characteristics when a second dielectric layer is changed to SiON.

FIG. 4 shows a second dielectric layer and a part of the first dielectric layer formed of SiON.
FIG. 9 is a diagram illustrating jitter characteristics when the frequency is changed to.

Claims (1)

[Claims] A first dielectric layer, a recording layer, a second dielectric layer, a reflective layer, and a protective layer, which are laminated in this order on a substrate; Layer and second
An optical information recording medium characterized in that SiON (SiAlON) is used for one or both of the dielectric layers, and for part or all of the respective dielectric layers.