JPH02219689A - Information recording medium - Google Patents

Abstract

PURPOSE:To provide the title medium of a phase changing type which is capable of recording data at a short pulse width and highly sensitive to a regenerated signal by forming a recording layer consisting of the first layer and the second layer, both containing a common element, and at the same time, which forms a recording area containing an intermetallic compound due to fusion caused by projection of an optical beam. CONSTITUTION:A recording layer 2 for recording information consisting of the first layer 3 and the second layer 4 is formed on a substrate 1 of transparent material with less temporal change. The first layer 3 and the second layer 4 are formed with alloy or an intermetallic compound as a common constituent. Then an optical beam is projected to the recording layer 2 to fuse the first layer 3 and the second layer 4. Consequently, a recording area 5 containing the intermetallic compound is formed. As the recording area 5 contains the intermetallic compound as described above, it is possible to obtain the title medium capable of possessing high crystallization rate and recording data with a short laser pulse.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Field of Application) The present invention is directed to changing the optical characteristics of the beam-irradiated portion of the recording layer by irradiating it with a light beam such as a laser beam or an electron beam. The present invention relates to an information recording medium in which information is recorded by causing a change in optical characteristics, and information is reproduced by detecting the change in optical characteristics.

(Prior Art) Conventionally, as information recording media, there are known a perforation type and a phase change type. In the former, a recording layer 7 made of a low melting point metal, metalloid, or organic material is laminated on a substrate, and information is recorded by irradiating this recording layer with a laser beam to form holes. In the latter method, a recording layer that can undergo a phase change between, for example, a crystalline state and an amorphous state is laminated on a substrate, and information is recorded by irradiating this recording layer with a laser beam to cause a phase change. In either case, information is reproduced by detecting the difference in reflectance, etc. between the recorded portion and the non-recorded portion.

Materials constituting phase change type information recording media include:
TeOx (JP-A-5O-46317) and the like are known. In addition, two-layer structures such as Sb2Se3 and Bi2Te3 are also known (Japanese Patent Laid-Open No. 57-159692
．． 59-35988).

(Conspiracy to be Solved by the Invention) However, the hole-punching type information recording medium has a drawback (p) in that it is difficult to control the shape of the holes with laser light.

Further, the phase change type also has the disadvantage of slow erasing speed due to low crystallization speed. In addition, with a two-layer structure, one layer absorbs heat when irradiated with laser light,
Since the heat causes a phase change in the other layer, it is difficult to record with a short pulse width, and a high transfer rate cannot be obtained. Furthermore, in phase change type recording media, it is desired that the reproduced signal be even larger.

The present invention was made in view of the above circumstances, and it is an object of the present invention to provide a phase change type information recording medium that has a high phase change speed, can record information with a short pulse width, and has a large reproduced signal. purpose.

[Structure of the Invention] (Means for Solving the Problems) An information recording medium according to the present invention includes, firstly, a substrate and a recording layer for recording information by irradiation with a light beam. The recording layer includes a first layer and a second layer.
The first layer and the second layer have a common element, and are characterized in that they are fused by irradiation with a light beam to form a recording region containing an intermetallic compound.

Second, an information recording medium comprising a substrate and a recording layer for recording information by irradiation with a light beam, the recording layer comprising a first layer, a second layer, a first layer and a recording layer. At least two of these first to third layers have elements in common, and these three layers are fused by irradiation with a light beam to form an intermetallic layer. It is characterized by forming a recording site containing a compound.

(Function) By irradiating the recording layer with a light beam, the plurality of layers constituting the recording layer fuse in the heated portion to form a recording region containing an intermetallic compound.

Since these multiple layers contain common components, they are easily fused and form intermetallic compounds. An intermetallic compound is an alloy in which the number of atoms of the constituent elements of the alloy maintains a constant integer ratio, and these constituent atoms form a unit and occupy a specific position in the crystal lattice.

Therefore, a crystal with this composition becomes a single phase, and when a phase transition from amorphous to crystal occurs, it crystallizes by atomic movement over a short distance, so the crystallization rate is extremely fast.

Therefore, it is possible to record with a short pulse width. Furthermore, since a plurality of layers are fused to form a single-phase recording region, it is possible to increase the reproduction signal.

(Embodiments) Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a sectional view showing an information recording medium according to an embodiment of the present invention. The substrate 1 is made of a material that is transparent and has little change over time, such as glass or polymethyl methacrylate.
It is made of resin such as polycarbonate. On this substrate 1, a recording layer 2 for recording information, which is composed of a first layer 3 and a second layer 4, is formed.

The first layer 3 and the second layer 4 are formed of an alloy or an intermetallic compound, and have a common component.

Then, by irradiating the recording layer 2 with a light beam under predetermined conditions, the first layer 3 and the second layer 4 are fused to form a recording region 5 containing an intermetallic compound. Since the recording region 5 thus contains the intermetallic compound, the crystallization rate is high and information can be recorded with a short laser pulse.

Note that, as shown in FIG. 2, the recording layer 6 may have a three-layer structure including a first layer 7, a second layer 8, and a third layer 9 between these layers. In this case, at least two of these layers
It is sufficient that the layers have a common component, and are fused by being irradiated with a laser beam to form a recording region 10 containing an intermetallic compound. In this case, the first layer 7 and the second layer
It is preferable that the third layer 9 contains a common component with the layer 8, and the third layer 9 is formed of a material other than the component common to both layers.

Thereby, the thermal stability of the recording layer 6 can be improved.

Note that a protective layer can be provided between the substrate and the recording layer or on the recording layer, if necessary.

Next, an example of a method for forming a recording layer in an information recording medium according to the present invention will be described with reference to FIGS. 3 and 4. FIG. 3 is a vertical cross-sectional view showing a schematic configuration of sputtering used to form the recording layer, and FIG. 4 is a cross-sectional view thereof. In the figure, numeral 11 indicates a vacuum vessel, and this vacuum vessel 11 has a gas exhaust port 12 and a gas introduction boat 13 on its bottom surface. The gas exhaust boat 12 is connected to an exhaust device 25, and the inside of the vacuum container 11 is evacuated by the exhaust device 25.

The gas introduction boat 13 is connected to an argon gas cylinder 14, and argon gas as a sputtering gas is supplied from the cylinder 14 to the container 1 via the gas introduction boat 13.
1. The disk-shaped substrate 15 is supported by a support device 18 in the upper part of the vacuum container 11 with its surface horizontal, and is rotated by a motor (not shown) during film formation. In addition, near the bottom of the vacuum chamber 11, sputter sources 19.2° each made of each element constituting the recording layer are disposed so as to face the substrate 15. is connected to a high frequency power source (not shown). Monitor devices 22 and 23 are provided above these sputter sources 19 and 20, respectively, to monitor the amount of sputtered elements from each sputter source, and to control each sputter source so that the recording layer has a predetermined composition. The amount of electricity input is adjusted.

In such a sputtering apparatus, first, the inside of the vacuum chamber 11 is heated by the exhaust device 25 to, for example, 10 = To
Evacuate to a high vacuum of rr order. Next, while introducing argon gas from the gas introduction boat 13, the exhaust device 25
The inside of the vacuum container 11 is maintained at a predetermined pressure in an argon atmosphere by adjusting the exhaust amount.

While rotating the substrate 15 in this state, the sputter source 19.2
Sputtering is performed by applying a predetermined power to 0 for a predetermined time. As a result, a recording layer is formed on the substrate 15.

Note that when reproducing recorded information, the recording layer is irradiated with a low-power light beam and the optical/optical characteristics, such as the difference in reflectance, between the recorded area and the non-recorded area are detected.

Next, a test example in which the information recording medium according to the present invention was actually manufactured and tested will be explained.

Test Example 1 GeTe and Sb2Te3 sputtering sources were provided in a vacuum container, and the inside of the container was evacuated to 8×10=Torr. Next, argon gas is introduced and the inside of the container is 5XICI''.
' Adjusted to Torr. Outside diameter 130111% inside the container
A disk-shaped polycarbonate substrate having a thickness of 1.2 mm was installed after being thoroughly cleaned. While rotating this substrate at 6 Orpm, the amount of sputtering of each element from each sputtering source was monitored and the power input to each sputtering source was controlled. First, the GeTe sputtering source was sputtered to form GeTe (intermetallic compound). The first layer of Sb2Te3 (intermetallic compound) was deposited by 500 people, and then the second layer of Sb2Te3 (intermetallic compound) was deposited by sputtering with a 5b2Te3 sputtering source.
A recording layer with a two-layer structure was formed by collapsing the layers.

Next, an ultraviolet curable resin was overcoated by about 10 μm as a protective layer on the recording layer using a spin coater, and was cured by irradiating ultraviolet rays. As a result, an information recording medium sample was formed, and this sample was designated as Example 1.

Example 2 was a sample formed in the same manner as in Example 1, except that the GeTe sputtering source was changed to e 15 Te B5 and the first layer was formed from Ge 15 Te B5 (eutectic composition alloy). .

As comparative examples, G e 1s T e 85 and Bi2
Using Se3 as a sputtering source, the first layer is made of G e 15 T
Example 1.2 with e B5 and second layer made of Bi2Se3
A sample with a similar layer structure was prepared.

For these three samples, the wavelength was 830 nm.

Semiconductor laser light with a beam diameter of 11 was irradiated with various power and pulse width. 5 to 7 are graphs showing the recordable area, with the horizontal axis representing the pulse width of the laser beam and the vertical axis representing the laser power. and 2, and FIG. 7 shows a comparative example.

These results confirmed that both Examples 1 and 2 were capable of recording with shorter pulses than the Comparative Example. Further, when comparing Examples 1 and 2, Example 1 allows recording with a shorter pulse width. this is,
This is due to the fact that both the first layer and the second layer are intermetallic compounds.

Test Example 2 In this test example, Example 1 and Comparative Example were tested using a practical test device. FIG. 8 is a schematic configuration diagram showing the apparatus used in this test.

The information recording medium sample 31 is fixed to a spindle motor 32 and rotated at a predetermined number of rotations. An optical system 33 for focusing laser light onto the sample 31 is disposed above the sample 31 .

This optical system 33 includes a collimator lens 35, a beam splitter 36, a λ/4 wavelength plate 37, and an objective lens 38. The light output from the semiconductor laser 34 becomes parallel light at the collimator lens 35, and the beam splitter 36 and a λ°/4 wavelength plate 37, the recording layer of the sample 31 is condensed and irradiated by the objective lens 38. The reflected light from the sample 31 is split by a beam splitter 36,
The light passes through the detection lens 39 and enters the light receiver 40 to become a detection signal. This signal is also supplied to a servo system 42 which causes a current to flow through a drive coil 41 for driving the objective lens 38. This makes it possible to image a condensed spot on the sample 31 while always keeping the distance to the sample constant.

Using such an apparatus, each sample was fixed on a spindle motor and rotated at 900 rpm, while
At a position with a radius of 50 mm on these samples, a recording frequency of 2
MHz, recording power 10mW.

Recording was performed with a pulse width of 60 nsec.

The C/N (ratio of carrier to noise) at that time is shown in Table 1.

Table 1 As can be seen from Table 1, Example 1 had a higher
It was confirmed that a high C/N of 0 dB or more could be obtained.

Test Example 3 In this test example, a GeTe layer (thickness of 500 layers), a Bi layer (thickness of 100 layers), and a 5b2Te3 (thickness of 600 layers) were sequentially laminated in basically the same manner as in Test Example 1 to form a recording layer. A sample was prepared, and this was designated as Example 3. GeTe of Example 3 is G e 15 T e B
Example 4 was a sample prepared in the same manner as Example 3, except that the sample was changed.

These samples were left in an environment of 60°C for 500 hours,
At that time, the reflectance from the substrate side was measured.

The results are shown in FIG. FIG. 9 is a graph showing changes in reflectance over time, with time on the horizontal axis and reflectance normalized to the initial reflectance R on the vertical axis. From this figure, it was confirmed that Examples 3 and 4 were stable with almost no change in reflectance.

[Effects of the Invention] According to the present invention, it is possible to provide an information recording medium that is capable of recording with a short pulse width, has a large reproduced signal, and is sufficiently durable for practical use.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views of an information recording medium according to an embodiment of the present invention, FIG. 3 is a vertical cross-sectional view showing a schematic configuration of an apparatus for forming a recording layer, and FIG. 4 is a cross-sectional view thereof. Figures 5 and 6 are graphs showing the recordable range of an embodiment of the present invention, Figure 7 is a graph showing the recordable range of a comparative example, and Figure 8 shows a practical recording device. The schematic configuration diagram and FIG. 9 are graphs showing changes in C/N over time. 1; Substrate, 2.6; Recording layer, 3.7: First layer, 4. 8; second layer; 9; third layer.

Claims (2)

[Claims] (1) An information recording medium comprising a substrate and a recording layer for recording information by irradiation with a light beam, the recording layer having a first layer and a second layer; layer and second
An information recording medium characterized in that the layers have a common element and are fused by irradiation with a light beam to form a recording region containing an intermetallic compound. (2) An information recording medium comprising a substrate and a recording layer for recording information by irradiation with a light beam, the recording layer comprising a first layer, a second layer, a first layer and a second layer. At least two of the first to third layers have a common element, and these three layers are fused by irradiation with a light beam to form an intermetallic compound. An information recording medium characterized by forming a recording portion including: