JPH06119657A - Optical information recording medium - Google Patents

Abstract

PURPOSE:To obtain an optical information recording medium causing a slight change of the reflectance due to a variation of the thickness of the recording film, performing satisfactory reproduction and having satisfactory recording sensitivity in spite of its simple two-layered structure not requiring a heat insulating layer or a reflecting layer as an alloy type optical information recording medium fit for high density recording. CONSTITUTION:An amorphous Ge-Sb-Te layer 3 having a compsn. on a line connecting Sb2Te3 and GeTe in a Ge-Sb-Te triangular diagram as a 1st layer and a crystalline Bi-Te layer 4 having 2:3 atomic ratio as a 2nd layer are successively formed as a recording film 2 having a two-layered structure on a transparent substrate 1. A UV-curing resin layer 5 is further formed on the Bi-Te layer 4.

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 used in a large-capacity optical recording memory for storing code data and image data used in a document filing apparatus and a computer.

[0002]

2. Description of the Related Art As a conventional recordable optical information recording medium, a recording film having a low melting point such as Te or Bi provided on a substrate is irradiated with a laser beam to form a hole. There is known an optical information recording medium that records information by changing the reflectance of the recording film depending on the presence or absence of the information.

On the other hand, in the non-perforated type, as disclosed in, for example, Japanese Patent Publication No. 3-80635, the recording film provided on the substrate is heated by irradiation with a laser beam or the like so that the light of the recording film is exposed. There is known an optical information recording medium that records information by changing the absorption coefficient and changing the reflectance of the recording film due to the change of the absorption coefficient.

In other non-perforated type, as disclosed in, for example, Japanese Patent Laid-Open No. 60-28045, a first film having a high transmittance for laser light on a substrate as a recording film.
A layer and a second layer that absorbs laser light are provided on the first layer, and these two layers are alloyed by irradiation of the laser light from the substrate side, and interference conditions of multiple repeated reflection of the laser light on the recording film are provided. There is known an optical information recording medium that records information by changing the reflectance and changing the reflectance of the recording film viewed from the substrate side. Among the above types, the two-layer alloyed type optical information recording medium has excellent characteristics suitable for high density recording.

However, in the two-layer alloy type optical information recording medium, when the extinction coefficient of the first layer provided on the substrate is close to zero, the laser beam incident from the substrate side is the first laser beam.
Since the attenuation in the layer is small, the interference condition of multiple repeated reflections in the recording layer sharply changes with the variation of the first layer thickness. Therefore, the change in the reflectance of the recording film caused by the change in the first layer thickness becomes large.

On the other hand, when the extinction coefficient of the first layer is increased, the multiple reflection light is absorbed and attenuated, so that the interference effect becomes small and the change in the reflectance due to the change in the thickness of the first layer becomes small. However, if the extinction coefficient becomes too large, there is a problem in that the change in reflectance before and after recording cannot be made large by utilizing the interference effect, resulting in a decrease in S / N of the reproduced signal.

[0007]

As described above, in the conventional two-layer alloyed type optical information recording medium, the change in the reflectance caused by the change in the film thickness of the recording film is large,
This increases the jitter of the reproduced signal and causes an error. Further, it is necessary to provide a heat insulating layer and a reflective layer, and there is a problem that an optical information recording medium having a simple two-layer structure and good recording sensitivity cannot be obtained.

Therefore, the present invention solves the above problems in an alloy type optical information recording medium suitable for high density recording, that is, the change in reflectance caused by the film thickness variation of the recording film is small and good. Can be played, and moreover,
An object of the present invention is to provide an optical information recording medium having a good recording sensitivity with a simple two-layer structure that does not require a heat insulating layer or a reflecting layer.

[0009]

In order to solve the above-mentioned problems, the present invention irradiates a recording film laminated in two layers on a transparent substrate with a laser beam from the substrate side so that the constituent atoms of the two layers are mutually exchanged. An optical information recording medium for recording information by changing the reflectance condition of the recording film by changing the interference condition of multiple repetitive reflection of the laser light with respect to the recording film by diffusing and alloying with the substrate. the first layer is an amorphous Ge-Sb-Te layer, which is a composition on the line connecting Sb ₂ Te ₃ and GeTe in a triangular diagram consisting of Ge-Sb-Te, the first layer of the recording film provided The second layer provided above is crystalline Bi-Te with an atomic ratio of 2: 3.
It is configured such that an ultraviolet curable resin layer is further provided on the second layer.

[0010]

In the two-layer alloy type optical information recording medium having the above structure, assuming that a semiconductor laser having a wavelength of 830 nm which is generally used as the laser beam, the extinction coefficient of the first layer is about 1. It is in the range of 5 to 2.5, and both effects of light interference and attenuation can be obtained without being biased to one side. Therefore, it is possible to obtain a sufficient S / N ratio as a reproduction signal and reduce the change in reflectance due to the change in the thickness of the first layer. Further, since the first layer is semitransparent to the laser light, a part of the laser light incident from the substrate side is absorbed by the first layer, and the transmitted light has large absorption (the extinction coefficient is about 3.4) Further absorption in the second layer. Therefore, the heat conversion efficiency of laser energy is increased, and sufficient recording sensitivity can be obtained with a simple two-layer structure.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a layer structure of an optical information recording medium A, in which a recording film 2 having a two-layer structure is sequentially formed on a transparent substrate 1, and an amorphous Ge-Sb-Te layer is formed as a first layer. 3 and a crystalline Bi-Te layer 4 having an atomic ratio of 2: 3 as the second layer 4
To provide. Further, an ultraviolet curable resin layer 5 is provided on the Bi-Te layer 4.

Amorphous Ge-Sb-Te is used as the first layer.
The layer 3 is an amorphous Ge-Sb-Te layer having a composition on the line connecting Sb ₂ Te ₃ and GeTe in the triangular diagram formed of Ge-Sb-Te shown in FIG. 2, and for example, the atomic ratio is 1 :. The amorphous Ge-Sb-Te layer is one of 2: 4, 1: 4: 7, and 2: 2: 5.

Then, the amorphous Ge-Sb-Te layer 3 and the crystalline Bi-Te layer 4 in the portion of the recording film 2 irradiated with the laser beam 6 are diffused by the laser beam 6 incident from the substrate 1 side. Information recording / reproduction is performed by alloying and improving the reflectance of this diffusion / alloying portion 7 as compared with other portions.

Further, the amorphous Ge-Sb-Te layer 3 as the first layer of the recording film 2 is attenuated at the same time as the transmission of the laser beam 6, that is, it is absorbed, so that the amorphous Ge-Sb-Te layer 3 is less than the conventional one.
The heat exchange efficiency of the energy is increased, and good recording sensitivity can be obtained.

Crystalline Bi as the second layer of the recording film 2
The -Te layer 4 is composed of the amorphous Ge-Sb-Te layer 3 and the crystalline B.
It is preferable for promoting diffusion and alloying of the i-Te layer 4. The ultraviolet curable resin layer 5 is made of amorphous Ge-S.
While protecting the recording film 2 of the b-Te layer 3 and the crystalline Bi-Te layer 4, it has a small thermal conductivity and contributes to the improvement of recording sensitivity.

Thus, the optical information recording medium A of the present invention
In the case of a semiconductor laser having a wavelength of 830 nm that is generally used as the laser light 6,
The extinction coefficient of the amorphous Ge-Sb-Te layer 3 as a layer is within the range of about 1.5 to 2.5, and both effects of light interference and attenuation can be obtained without being biased to one side. Therefore, a sufficient S / N ratio can be obtained as a reproduction signal, and the change in reflectance due to the change due to the thickness of the amorphous Ge-Sb-Te layer 3 as the first layer can be reduced.

FIG. 3 shows the relationship between the film thickness variation of the first layer and the reflectance. In the figure, (a) is the reflectance curve of the optical information recording medium of the present invention, and (b) is a comparison. The reflectance curve of the example is shown, and it is confirmed that the variation of the reflectance due to the variation due to the thickness of the amorphous Ge—Sb—Te layer 3 as the first layer can be reduced.

Amorphous Ge-Sb-T is used as the first layer.
Since the e layer 3 is semi-transparent to the laser light 6, a part of the laser light 6 incident from the substrate 1 side is absorbed by the amorphous Ge-Sb-Te layer 3 as the first layer and transmitted. The absorbed light is further absorbed by the crystalline Bi-Te layer 4 as the second layer having a large absorption (the extinction coefficient is about 3.4). Therefore, the heat conversion efficiency of laser energy is increased, and sufficient recording sensitivity can be obtained with a simple two-layer structure as shown in FIG.

Even if the first layer has the same composition, the crystalline layer has an extinction coefficient of 3 or more, so that the effect of interference cannot be seen and a sufficient S / N cannot be obtained as a reproduced signal.

Usually, a sputtering method is used for forming the recording film. In general, when an intermetallic compound is used as a sputtering target, the composition of the formed film hardly changes. In the present invention, the first
Since the compositions of the amorphous Ge-Sb-Te layer 3 as the layer and the crystalline Bi-Te layer 4 as the second layer are the same as those of the intermetallic compound, the intermetallic compound is directly used as the sputtering target. Thus, the recording layers 3 and 4 having almost no composition deviation can be obtained, and the stable production of the information recording medium A becomes possible.

As described above, according to the present invention, a diffusion / alloying type optical information recording medium A having a small change in reflectance with respect to the change in the film thickness of the first layer of the double-layered recording film 2 is obtained. Further, good recording sensitivity was obtained with a simple layer structure without providing a heat insulating layer or a reflective layer. The present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made without departing from the spirit of the present invention.

[0023]

As described above, according to the present invention, in the alloy type optical information recording medium suitable for high density recording, the change in reflectance caused by the change in the film thickness of the recording film is small and good reproduction is possible. Further, it is possible to provide an optical information recording medium having a good recording sensitivity with a simple two-layer structure that does not require a heat insulating layer or a reflecting layer.

[Brief description of drawings]

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

FIG. 2 is a triangular diagram composed of Ge-Sb-Te.

FIG. 3 is an explanatory diagram showing the relationship between the variation in film thickness of the first layer and the reflectance of the optical information recording medium of the present invention.

FIG. 4 is a recording power and C of the optical information recording medium of the present invention.
Explanatory drawing which shows the relationship with / N.

[Explanation of reference numerals] 1 ... Transparent substrate, 2 ... Recording film having a two-layer structure, 3 ... Amorphous Ge
-Sb-Te layer (first layer), 4 ... Crystalline Bi-Te layer (second layer) having an atomic ratio of 2: 3, 5 ... UV curable resin layer, 6
… Laser light, 7… Diffusion / alloying part.

Claims (2)

[Claims] 1. The recording of the laser light by irradiating the recording film laminated in two layers on a transparent substrate with laser light from the side of the substrate to mutually diffuse and alloy the constituent atoms of the two layers. In an optical information recording medium for recording information by changing the interference condition of multiple repeated reflection with respect to the film and changing the reflectance of the recording film, the first layer of the recording film provided on the substrate is Ge-S.
In the trigonometric diagram consisting of b-Te, Sb ₂ Te ₃ and GeT
In the amorphous Ge-Sb-Te layer having a composition on the line connecting e, the second layer provided on the first layer has an atomic ratio of 2: 3.
2. An optical information recording medium, characterized in that the crystalline Bi-Te layer of 1. is further provided with an ultraviolet curable resin layer on the second layer. 2. The recording of the laser light by irradiating the recording film laminated in two layers on a transparent substrate with laser light from the substrate side so that the constituent atoms of the two layers are mutually diffused and alloyed. In an optical information recording medium for recording information by changing the interference condition of multiple repetitive reflection with respect to the film and changing the reflectance of the recording film, the first layer of the recording film provided on the substrate has an atomic ratio. The amorphous Ge-Sb-Te layer of any one of 1: 2: 4, 1: 4: 7 and 2: 2: 5, wherein the second layer provided on the first layer has an atomic ratio. An optical information recording medium comprising a 2: 3 crystalline Bi-Te layer and an ultraviolet curable resin layer further provided on the second layer.