JPH02167787A - Information recording medium - Google Patents

Abstract

PURPOSE:To increase the stability of an amorphous state and oxidation resistance in a recording layer and accelerate crystallization speed and make a retrieving signal more sensitive by providing the recording layer consisting mainly of an alloy of such composition as expressed by a specific formula. CONSTITUTION:A recording layer 2 which records information and an organic protective layer 3 are formed on a substrate 1 for an information recording medium. The recording layer 2 is composed mainly of an alloy of such a composition as expressed by (InxSb100-x)100-aSea (a,x are atomic % and are within the range of 20<a<=60, 48<=x<=52). The alloy of this composition is changed reversibly between a crystal phase and an amorphous phase by projecting light beams with varying conditions. The alloy is characteristic of high retrieving signal and recording sensitivity, high amorphous stability as a recording state and high oxidation resistance. In addition, the protective layer 2 has both ends sandwiched by inorganic protective layers 4,5 to prevent the temporal change of the recording layer 2.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) This invention aims to change the atomic arrangement in 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 repeatedly recorded and erased by causing a change in atomic arrangement, and information is reproduced by detecting changes in optical characteristics caused by changes in the atomic arrangement.

(Prior Art) So-called phase change type media have been known as information recording media (for example, erasable optical discs) on which information can be erased. Such information recording media include a substrate made of glass or plastic material (polymethyl methacrylate resin, polycarbonate resin, etc.) and a recording layer formed on this substrate. Further, if necessary, a protective layer made of a dielectric material or the like is provided between the substrate and the recording layer or on the recording layer. The material forming the recording layer is T.
metals or metalloids such as e, Se, Ge, Sb, Sn,
or alloys thereof, such as GeTe5bS, AsTeG
e, 5nTeSe.

5bTeSe is known.

In a recording layer formed of such a material, by being irradiated with light beams under different conditions, the irradiated area becomes a highly crystalline state (a state in which atoms are relatively correctly arranged,
It reversibly changes between a state (hereinafter referred to as a crystalline state) and a state in which crystallinity is reduced (a state in which the atomic arrangement is disordered, hereinafter referred to as an amorphous state). These two states have different optical properties such as reversibility and transmittance, so information can be recorded and erased using changes in these states, and information can be retrieved by detecting the optical properties associated with this change. Can be played.

(Problems to be Solved by the Invention) However, the above-mentioned recording layer material has a drawback that the erasing speed is slow because the crystallization speed is low. Further, there are also problems in that the stability of the recording state is low and the oxidation resistance is poor. Furthermore, there are also disadvantages in that the reproduced signal is not sufficient and the sensitivity is low.

Therefore, it has been difficult to put such a material into practical use as the B layer.

The present invention was made in view of the above circumstances, and an object thereof is to provide an information recording medium with a high erasing speed, high recording state stability and oxidation resistance, and high reproduction signal and recording sensitivity. do.

[Structure of the Invention] (Means for Solving the Problems) An information recording medium according to the present invention includes a substrate and a recording layer in which atomic arrangement is changed by irradiation with a light beam and information is recorded and erased in the layer. An information recording medium, wherein the recording layer has the following formula: (I nX 5bloo-x ), 100
-a Sea (However, Sa.

X is atomic % and is in the range of 20 x a≦60.48≦X≦52).

(Function) In-3b alloy is a material that absorbs pulsed light, easily changes between amorphous and crystalline, and has extremely large changes in optical properties (reflectance, transmittance) between these states. It is. Also,
By adding an appropriate amount of Se to In-3b alloy, recording sensitivity is increased, reproduction signal is further increased, amorphous state is stabilized, crystallization speed is increased, and oxidation resistance is increased. Can be done. Therefore, by setting the composition of the recording layer within the above-mentioned range, an information recording medium with extremely good characteristics can be obtained.

(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. A recording layer 2 for recording information is formed on this substrate 1.

This recording layer 2 is (Inx Sb+oo-x) 100-*Sea
(However, a.

The alloy is mainly composed of an alloy having a composition represented by the following formula, where X is atomic % and falls within the range of 20 x a≦60.48≦X≦52. An alloy having such a composition can undergo a reversible phase change between a crystalline state and an amorphous state by irradiation with a light beam under different conditions. Further, it has the characteristics of high reproduction signal and recording sensitivity, high stability of the amorphous state as a recording state, and high oxidation resistance. Furthermore, since the crystallization speed is high, the initialization speed and erasing speed are high. Here, In and s
If the In content is 30 to 60 atomic % relative to the total amount of b, it can be applied as a recording layer, but in order to obtain a sufficient reproduction signal and crystallization speed, the In content should be 48 to 52 atomic % as described above. . Furthermore, if the amount of Se is less than 20 atomic %, the stability will decrease, and if it exceeds 60 atomic %, the contrast between the crystal and the amorphous will become small and the reproduced signal will become small.

Therefore, the amount of Se is defined within the above range. Note that this recording layer 2 can be formed by vacuum deposition, sputtering, or the like.

An organic protection layer 3 is formed on the recording layer 2 . This protective layer 3 is provided to prevent scratches and dust on the surface of the information recording medium when it is handled, and is made of ultraviolet curing resin.

Furthermore, as shown in FIG. 2, the recording layer 2 may be sandwiched between inorganic protective layers 4.5 on both sides. In this case, the material JWII4.5 can be formed of a metal or metalloid oxide, fluoride, sulfide, nitride, or the like. These protective layers 4.5 are provided to prevent the recording layer 2 from deteriorating over time.

Further, as shown in FIG. 3, a protective layer 4.5 of the alloy constituting the above-mentioned recording layer 2 (indicated by A in FIG. 3) is formed on the substrate 1.
It is also possible to provide a recording layer 6 dispersed in a material (indicated by B in FIG. 3) constituting the recording layer.

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. 4 and 5. FIG. 4 is a vertical cross-sectional view showing a schematic structure of sputtering used to form the recording layer, and FIG. 5 is a cross-sectional view thereof. In the figure, 11 indicates a vacuum vessel, and this vacuum vessel 11 has a gas exhaust boat 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 is introduced into the container 11 as a sputtering gas from the cylinder 14 via the gas introduction boat 13. The disk-shaped substrate 15 is a support device 18
It is supported with its surface horizontally in the upper part of the vacuum chamber 11, and is rotated by a motor (not shown) during film formation. Furthermore, near the bottom of the vacuum chamber 11, one sputtering source 20.21 formed of each element constituting the recording layer is disposed so as to face the substrate 15, and each sputtering source is A high frequency power source (not shown) is connected to. These sputter sources 19.20.2
Monitor devices 22, 23, and 24 are provided above 1 to monitor the amount of sputtered elements from each sputter source, and adjust the power input to each sputter source so that the recording layer has a predetermined composition. The amount can be adjusted.

In such a sputtering apparatus, first, the inside of the vacuum chamber 11 is heated to, for example, 10-6 Torr by the exhaust device 25.
Evacuate to a high vacuum of r order. Next, while introducing argon gas from the gas introduction boat 13, the exhaust amount of the exhaust device 25 is adjusted to maintain the inside of the vacuum container 11 in an argon atmosphere at a predetermined pressure.

While rotating the substrate 15 in this state, the sputter source 19.2
At 0.21, sputtering is performed by applying a predetermined power for a predetermined time. As a result, a recording layer is formed on the substrate 15.

Note that when forming the inorganic protective layer, it can be performed in the same manner as described above using a sputtering source adjusted to the composition of the protective layer. Further, when the organic protective layer is formed of an ultraviolet curable resin, the ultraviolet curable resin is applied by a spin cord method and then cured by irradiation with ultraviolet rays.

Next, the initialization of the recording layer and the recording, erasing, and reproducing of information in the information recording medium of the present invention will be explained.

The initialization recording layer 2 is normally amorphous immediately after film formation, but in order to record information it needs to be crystalline, so the recording layer 2 is heated and slowly cooled by irradiating the entire surface with a light beam. , crystallize.

A light beam with high recording power and short pulse width is irradiated onto the recording layer 2,
The dot-paired portion is heated and rapidly cooled to change into an amorphous state, forming a recording mark.

The erasing recording layer 2 is irradiated with a light beam of lower power than that used during recording to change the recording marks into crystals and erase the information.

A light beam of lower power than that used during erasing is irradiated onto the recording layer 2 on which reproduced information is recorded, and a piece of information is reproduced by detecting the difference in optical characteristics, such as reflectance, between the recorded mark and the non-recorded area. .

Note that since the information recording medium according to the present invention has a high crystallization speed, overriding is possible. Overriding is erasing by power modulating a light beam such as a laser beam emitted from a single light source between two power levels PE (erasing) and Pw (recording) as shown in Figure 6. This involves superimposing a pulse at a recording power level on a light beam at a high power level, and overwriting new information while erasing already recorded information.

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 In, Sb, and Se spatter sources were provided in a vacuum container, and the inside of the container was evacuated to 8×10 Torr. Next, argon gas was introduced and the inside of the container was heated to 4 x 10-3T.
Adjusted to orr. A disk-shaped polycarbonate substrate having an outer diameter of 1301111% and a thickness of 1.2 mm was placed inside the container in a thoroughly cleaned state. While rotating this substrate at 60 rpm, sputtering was performed while monitoring the amount of sputtering of each element from each sputtering source and controlling the power input to each sputtering source.
A recording layer was formed by depositing each element until the concentration of 0.00 was reached.

Next, an ultraviolet curable resin was coated as a protective layer on the recording layer by about 10 μm using a spin coater, and the resin was cured by irradiation with ultraviolet rays. As a result, an information recording medium having a recording layer having a desired composition was formed.

Using this method, samples were prepared in which the composition of the recording layer was (1n4ss bs2) +00-X S ex and X was 10, 20, 30, and 40 atomic %, respectively.

As a result of thermal analysis of these using a differential scanning calorimeter (DSC), the results shown in FIG. 7 were obtained.

FIG. 7 is a graph showing the relationship between the amounts of Se added on the horizontal axis and the crystallization temperature on the vertical axis. As shown in this figure, it was confirmed that the crystallization temperature increased as the amount of Se added increased. That is, it was confirmed that the stability of the amorphous recording state increases with an increase in Se.

Test example 2 (I n4sS bsz) too-x S ex
An optical disk sample having a recording layer of 10, 20, 30, 40, and 60 atomic %, respectively, and having the structure shown in FIG. 2 was prepared. 5i02 with a thickness of 1000 mm was used as a protective layer sandwiching both sides of the recording layer. In this case, the recording layer and the organic protective layer were created in the same manner as in Test Example 1, and the 5i02 protective layer was formed by sputtering using the same apparatus as in Test Example 1, using 5i02 as the sputtering source.

In this test example, these samples were tested using a practical test device. FIG. 8 is a schematic configuration diagram showing the apparatus used in this test. Optical disk 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 is
The collimator lens 35 converts the light into parallel light, which passes through the beam splitter 36 and the λ/4 wavelength plate 37 and is focused onto the recording layer of the sample 31 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, for each of the above-mentioned samples, 7
While rotating at 00 rpm, the sample was irradiated with continuous light of 6 mW for one rotation, and this was repeated until the reflectance became constant. As a result, the reflectance became constant after repeating this operation four times for each sample. That is, this caused the irradiated portion to crystallize. Next, recording was performed on the crystallized portion by changing the power and pulse width of the laser beam.

As a result, it was confirmed that the reflectance of the irradiated portion returned to its original state under predetermined conditions, that is, it returned to an amorphous state. This is shown in FIG. Figure 9 shows the relationship between the amount of Se added on the horizontal axis and the minimum laser beam energy required for recording (for the reflectance to return to its original value) on the vertical axis. This is a graph showing. As shown in this figure, it was confirmed that as the amount of Se added increased, the energy required for recording decreased.

Test Example 3 Recording layer (I n4g5 bs2) Ioo-x S
In ex, X is 10, 20.30, 40.60, respectively.
A sample having a layer structure similar to that of the sample of Test Example 2 and having a concentration of 80 atom % was prepared in the same manner as in the Test Example.

This sample was placed in the apparatus shown in Test Example 2, and
While rotating at 0 rpm, a laser beam of a predetermined power and pulse width was irradiated to record a signal. Then, the amount of change in reflectance of this recorded portion was measured. FIG. 10 is a graph showing the relationship between the amount of Se added on the horizontal axis and the ratio (contrast ratio) between the reflectance of the recorded portion and the initial reflection on the vertical axis. As shown in this graph, it was confirmed that the addition of Se increases the contrast ratio, and that a particularly good contrast ratio can be obtained when the amount of Se added is in the range of 20 to 60 atomic %.

[Effects of the Invention] According to the present invention, Se
By adding an appropriate amount of , the stability of the amorphous state and oxidation resistance in the recording layer are increased, the crystallization rate is increased, and the reproduced signal can be further increased. Therefore, it is possible to obtain an information recording medium that has good characteristics and is sufficiently durable for practical use.

[Brief explanation of the drawing]

1 to 3 are cross-sectional views showing an information recording medium according to an embodiment of the present invention, FIG. 4 is a vertical cross-sectional view showing a schematic configuration of an apparatus for forming a recording layer, and FIG. 5 is a cross-sectional view thereof. 6 is a diagram showing the power of the laser beam during override, FIG. 7 is a graph showing the relationship between the amount of Se added to the recording layer and the crystallization temperature, and FIG. 8 is a schematic configuration of the recording device. 9 is a graph showing the relationship between the amount of Se added to the recording layer and the laser power for recording, and FIG. 10 is a graph showing the relationship between the amount of Se added to the recording layer and the contrast ratio. 1: Substrate, 2.6: Recording layer, 3.4.5: Protective layer. Applicant's representative Patent attorney Takehiko Suzue Figure 1 Figure 6 Figure 2 Addition ω εO@A-z Se=&s口I(,i”?'/,)No. 7
Figure 3 Figure 8 Figure ω 3 Otsu 4Q-+5e4770t (&-'5'/-) Figure ω ω 614M1qSe4. IIo amount<*,'r-"t,>Figure 10

Claims (1)

[Claims] An information recording medium comprising a substrate and a recording layer in which information is recorded and erased by a change in atomic arrangement caused by irradiation with a light beam, the recording layer having the general formula (In_xSb_1
_0_0_-_x)_1_0_0_-_aSe_a (However, a and x are atomic %, 20<a≦60, 48≦
An information recording medium mainly comprising an alloy having a composition expressed by x≦52.