JPH0334887A - Data recording medium - Google Patents

Abstract

PURPOSE:To facilitate the high speed crystallization and amorphous conversion of a recording layer and to make a one-beam over-write system possible and to obtain a good over-write characteristics by constituting the recording layer of In, Sb and Te and specifying the compositional ratio of In, Sb and Te. CONSTITUTION:A substrate 1 is formed of a transparent material low in a change with the elapse of time, for example, glass or a resin such as polycarbonate. A protective layer 2, a recording layer 3, a protective layer 4, a reflecting layer 5 and a resin layer 6 are formed on the substrate 1 in this order. The recording layer 3 is formed from an alloy having a composition represented by (In100-xSbx)100-yTey (wherein x and y are respectively atomic% and x is 45<=x<=50 and y is 25<=y<=45). The alloy of this composition satisfies high speed crystallization and amorphous conversion and a one-beam over-write system becomes possible.

Description

[Detailed Description of the Invention] [Key Points of the Invention] (Industrial Application Field) The present invention provides a method for forming a phase between a crystalline phase and an amorphous phase in a recording layer by irradiating a light beam such as a laser beam. The present invention relates to an information recording medium such as an optical disk that can record or erase information by causing a change.

(Prior Art and Problems to be Solved by the Invention) Phase change type optical discs have been known as optical discs from which information can be erased. In such phase-change optical discs, information is recorded and recorded by reversibly changing the irradiated portion of the recording layer between two different structural states depending on the irradiation conditions of the laser beam that irradiates the recording layer.
to erase.

Examples of materials used for such optical discs include Te, Ge, TeGe, and InSe.

Semiconductors, semiconductor compounds, or intermetallic compounds such as 5bSe and 5bTe are known. These can take two states, a crystalline phase and an amorphous phase, depending on the laser beam irradiation conditions, and the complex refractive index N=n-ik in each state is different. The idea of creating an erasable optical memory by reversibly changing the state of the laser beam irradiated portion of the recording layer between a crystalline phase and an amorphous phase through laser beam heat treatment is based on S, R, 0 vs.
It has been proposed by Hinsky et al.
surgical transactions 2
．． 641 (1971)).

According to this, depending on the laser beam irradiation conditions, the irradiated portion U=J is selectively made into either a crystalline or amorphous state, and these states are determined by the difference in reflectance caused by the reproduction phase laser beam irradiation. The information is re-processed 14- by distinguishing between the two states. When recording information, the recording layer is irradiated with a high-power, short-pulse laser beam that can heat the recording layer to a temperature exceeding the melting point of the material, melting and rapidly cooling the irradiated area to form amorphous recording pits. do. In addition, when erasing recorded information, it is necessary to heat the recording layer material to a temperature exceeding the crystallization temperature. returns to crystalline state.

Recording and erasing of such information is possible using a circular spot laser beam for rapid cooling to amorphous and ↑− for slow cooling to crystallize.
It is carried out using a two-beam method using an oblong elliptical spot for J and a beam for vanishing.

However, in the 2-beam system, the optical system is complicated, and in particular, it is difficult to make the long elliptical spot follow the spiral trunk of the disk, making it difficult to use a complicated machine (:111). .

Therefore, research is underway on a 1-beam system in which recording and erasing are performed using a single laser beam.In principle, overrides can be easily performed in this 1-beam system.Override means that the laser beam that is shaved from the heavy laser beam is adjusted to two levels of power level Fl.
The power is modulated between y (extinguishing) and P (recording) (1) W>PE)5, thereby changing the already recorded information to /j'
This is a method of overwriting new information while increasing the number of pages. This method of performing override using one beam of laser is called a one-beam override method.

] beam system can also eliminate other drawbacks of the two-beam system.

However, when applying the 1-beam override method to a phase change recording layer, the following difficulties arise. In other words, whether the beam-irradiated portion of the recording layer becomes amorphous or crystalline depends on the irradiated laser beam! , it is not possible to use slow cooling crystallization to extinguish information. In other words, crystallization must be carried out in as short a time as amorphization.

Also, when recording information, the power level of the recording beam is superimposed on the tli beam power level, so
In non-crystalline recording, it is difficult to form amorphous recording pits because the area around the area where the A pits are to be formed is heated by the non-level laser of the erasing bar and rapidly cooled.

As described above, BIM-oherite is difficult to produce in a phase-change recording layer, and at present very few practical recording layer materials have been found that make this possible. .

This invention was made in view of such circumstances, and
The objective is to provide an information recording medium that is capable of one-beam override and has good characteristics.

[Structure of the Invention] (Means for Solving the Problems) An information recording medium according to the present invention reversibly selectively switches between a crystalline phase and an amorphous phase depending on the substrate and the irradiation conditions of the light beam. An information recording medium having a phase change of iA 1m, wherein the recording layer has (In+oo-x Sbx
) 100-y Te, (T, Xy are each expressed as atomic %, and each 45≦x≦50.25≦y≦
45)).

(Function) A recording layer composed of In, Sb, and Te in the above-mentioned composition ratio can be easily crystallized at high speed and made amorphous. Therefore, even if the recorded portion is rapidly cooled to the same extent as when it is made amorphous, it is still possible to erase the recorded portion, and it is also possible to easily form amorphous recorded pits. Therefore, the 1-beam override method becomes 111 times more efficient, and good override characteristics can be obtained.

(Example) This invention will be explained in detail below.

The first cut is a sectional view showing an information recording medium according to an embodiment of the present invention. The substrate 1 is transparent and does not change easily over time (it is made of a material such as glass or a resin such as polycarbonate).On the substrate 1 there are a protective layer 2, a recording layer 3, a protective layer 4, a reflective layer 5, and resin layer 6 are formed in this order.

The protective layer 2.4 is made of an inorganic dielectric material and has the following functions.

O) A function to prevent the formation of holes due to evaporation of the irradiated portion when the recording layer 3 is irradiated with a laser beam.

■A function to control the temperature of the recording layer 3 so that the desired Japanese food is produced when the laser beam is irradiated onto the recording layer 3.

■A function that uses optical interference to re/ennoise the I=signal.

The anti-cutting layer 5 is formed of a fully bent material such as AI, and reflects the laser beam for reproduction, and cooperates with the protective layer 4 to prevent reproduction (≧
I, f [2] have the function to ennoble the issue.

The resin layer 6 is formed of, for example, an ultraviolet curing resin, and has the function of preventing scratches and the like from occurring.

Although it is preferable to provide the protective layers 2 and 4, the reflective layer 5, and the resin layer 6, it is not necessary to provide them.

The recording layer 3 is (I n +oo-1S b+, ) +oo-y T
e y (where, Xy is each expressed as atomic % -C
and is within the range of 45≦x≦50.25≦y≦45). The metal-containing parts of T and II are shaped like J. This composition is within the range shown by diagonal lines in FIG. 2, and such an alloy of 14-14 satisfies rapid crystallization and amorphization, making it possible to perform BIM overwriting. Below, I will explain the rationale.

In the I n-3b system, I n 5LIS b 5L
It is already known that the crystallization rate of l-gold intercalation compounds is extremely fast. According to the experiments of the present inventor, the crystallization rate was 45 n5cc. Therefore, this In1. S
b. If the i11 precept is based on intermetallic compounds,
High-speed crystallization is possible. On the other hand, In5゜5b5o all 5
In a composition in which there is more sb than in the o compound, the excessive sb precipitates, resulting in a significantly slow crystallization rate.

This will not happen if I n is in excess. Therefore, In5°Sb,. The crystallization rate can be increased not only by intermetallic compounds but also by compositions with a slight excess of In. That is, I n
+oo-8Sb, if the alloy in the range of 45≦x≦50 is shifted to the base, high-speed viscocrystallization is possible. However, since the alloy with such a composition has a fast crystallization rate, it is difficult to make it amorphous. However, as a result of study by the inventor of the present application, it was found that 25 to 45 atomic percent of the alloy with this composition.
T is a chalcogen-based material that can be easily amorphized within the range of
It has been found that by adding e, it becomes easier to make the material amorphous, and the effect of pure Te, which has a fast crystallization rate (approximately 15 nsec), appears, so that a high crystallization rate is maintained.

Therefore, by making the recording layer 3 have the above-mentioned composition, high-speed viscocrystallization and amorphousization can be achieved, and the recording layer 3 can have a performance of 1 B or 1 iJ.

Next, an example of a method for manufacturing an information recording medium configured as described below will be described. First, the plate 1 is placed in a vacuum chamber of a sputtering device, and the inside of the chamber is brought to a high vacuum. Next, argon gas is introduced into the chamber to remove the argon sputter link on the target formed by, for example, Sin. As a result, a protective layer 2 is formed on the board.

While the chamber is kept in the same atmosphere t4j, the recording layer 3 is formed by three-dimensional simultaneous sputtering of targets made of each constituent element of the recording layer, or by sputtering of an alloy target adjusted in advance to the composition of the recording layer to be obtained. Form.

Thereafter, a protective layer 4 is formed in the same manner as the protective layer 2. First, the reflective layer 5 is formed by sputtering a desired total refraction target.

Thereafter, the substrate is removed from the sputtering apparatus, and an ultraviolet curable resin is coated on the reflective layer 5 by the zero spin code method, and the resin layer 6 is formed by irradiating ultraviolet rays.

Next, initialization, overriding and reproduction of information in the information recording medium configured as described above will be explained.

The initialization recording layer 3 is usually amorphous immediately after film formation, so in order to form amorphous recording marks, the recording layer 3 is irradiated with continuous laser beat light to form the recording layer. After raising the temperature above the crystallization temperature, it is slowly cooled to change the phase to a crystalline phase.

Recording (Override) When recording information, as shown in Fig. 3, the laser beam is recorded by changing the power Jη between the recording level PW, which is a high level, and the erasing power PE, which is a level lower than this level. Irradiate layer 3. In the first recording, only recording is performed using Pw to form recording marks 9 on the recording layer 3. From the second time onwards, the previously recorded information is erased using the power of P8 while new information is overwritten. In the case of an optical disc, while rotating the disc at a predetermined speed, apply the PW to the area you want to overwrite.
irradiates a recording beam with a power of

Then, the portions that are not irradiated with the recording beam are irradiated with the beam of the erasing power PE.

As a result, in the part irradiated with PE, the JI quality recording mark 9 of sub-i'+ij changes to a crystalline phase and the information is erased, and in the part irradiated with Pw, the phase changes to an amorphous state and the information is recorded. Marriage 9 is formed.

Reproduction Information is reproduced by irradiating the recording layer 3 with a laser beam whose power is even smaller than P, and by detecting the difference in the intensity of the opposite light between the recording mask 9 and the non-recorded portion using a photoelectric conversion element. .

Next, based on this example, an optical disc was created and its characteristics were evaluated.The results will be described below.

A 5-inch diameter disk-shaped substrate made of polycarbonate with a group was placed in the vacuum chamber of a 3-liter sputtering device, and radio frequency (R, F,) power]2 was applied to the Si02 target. Argon gas was sputtered to form a Si2 layer with a thickness of approximately 600 Å on the cleaning plate as a protective layer.

Next, In. 5b5o all 5o compound target and pure T
Simultaneous sputtering in argon gas was performed by applying R and F powers to the e-target to form a recording layer approximately 400 mm thick. At this time, the composition of the recording layer is (I n
100-x S bx ) +00-y Te y
The R and F powers were adjusted in advance so as to have a predetermined composition expressed by .

Thereafter, 5 in 2 argon sputtering was performed again to form a protective layer of Sin with a thickness of about 600 Å on the recording layer 17.

Furthermore, R, F, and power were applied to the Au target and argon sputtering was performed to form an Au reaction layer with a thickness of about 200 Å on the second side of the SiO2 protective layer to enhance the reproduction signal. did.

Then, take out this disk from the sputtering device, set it on a spinner, and apply about 10 f of ultraviolet curing resin.
The resin layer was spin-coded to a thickness of t m and cured by irradiation with ultraviolet rays 3 to form a resin layer.

In the manner described above, a plurality of optical disk samples with recording layers having various carbonized compositions were prepared. The composition of the recording layer is as follows.

Sample A? ! 7: (I n 5 L I S t) y
;o) 1OLl−F T e +(y−20,25,
30,35,45,50) Sample B group; (1n5
5sb, +li) 100-+ Tey (y=20.2
5,30,35,45.50) Sample C group; (I
n52sb48) 10oy Tey (y=20.2
5, 30, 35, 45. 50) Sample D group; (r
n4ssb, 2) too-F'rey(y=20
．． 25, 30, 35, 45. 50) Sample E group;
(I n, +, S bs5) +00-Y Te.

(y=20.25, 30, 35.45.50) These 35 disk samples were created under the same conditions except for the composition of the recording layer.

Next, while rotating these samples at 1-80 Or, p, m, the dynamic characteristics were evaluated (7) using the following procedure.

(a) First, the power at the recording layer surface is 1.4 mW
Tracks of the 4 iJ layer, which was amorphous immediately after film formation, were crystallized using continuous laser light. In this case, the same track was traced three times with a laser beam so that this portion was completely crystallized.

(b) Then, using a pulsed laser with an override waveform as shown in Figure 3. First, recording was performed once.

In this case, the power is 1.8 mW and the frequency is 4 MH,z
Information was recorded on the above-mentioned crystallized track by a recording pulse having a duty ratio of 50%. Note that the bias power for extinguishing fire was 1.4 mW.

After recording, the group of recording layers was irradiated with a 0.8 mW reproducing laser beam to reproduce the recorded information. The reproduced signal is A/D modified and C/N is processed by a spectroanalyzer.
The value was set to 41.

(C) A pulsed laser with the same conditions as the override waveform described above, except that the recording pulse frequency was changed to 5 MHz and the duty ratio was 50%, was irradiated onto the group that had been recorded once]-1. An override was performed.

After overriding, the recording layer group was again irradiated with a 5O18mW reproduction laser beam to reproduce the recorded information, the reproduced signal was A/I) converted, and the C/N value was measured with a spectroanalyzer. . Further, the C/N value of the A mark was determined at the previous frequency of 4 MHz, and the extent to which the previous recorded mark was erased was measured as the degree of erasure. The results are shown in FIGS. 4 to 8. Figures 4 to 8 are graphs showing the relationship between Te content on the horizontal axis and C/N value and erasure degree on the vertical axis, and are shown for Groups A to E, respectively. It is.

The C/N value and erasure degree referred to here will be explained with reference to FIG. 9. As shown in Figure 9(a), the C/N value of the reproduced signal after one day of recording (4MHz) is A, and (b)
As shown in , if the C/N value of the reproduced signal after overriding (5 MHz) is B, and the C/N value of the erased remaining signal of the first recording after overriding is B, then 11
3-A is the degree of erasure, and C is the C/N value.

In Figures 4 to 8, the C/N value is 30 dB or more,
If the extinction value is -20 dB or less, it is judged as having good override characteristics, and if it is any other value, it is judged as having insufficient characteristics.In this way, compositions judged to have good characteristics are judged as having good override characteristics. The compositions marked with "111" as having insufficient properties are marked with "X" and are shown in the composition diagram shown in FIG.

As is clear from FIG. 10, the composition of the Ti layer is (,1r
1+oo8S bt ) +00-y Te, it was confirmed that good override characteristics can be obtained if 45≦x≦50.25≦y≦45.

Effect of the invention] According to the invention, the composition of the recording layer is (In+oo-x sb, ) 100-y Te,
(T, Xy are each expressed as atomic %, and each is 4
5≦x≦50.25≦y≦45), the recording layer can be crystallized at high speed, and it is easy to make the recording layer amorphous. Therefore, good override characteristics can be obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an information recording medium according to an embodiment of the present invention; FIG. 2 is a 1 n -3b-Te system composition diagram showing the recording layer composition of the information recording medium of the present invention; The figure shows the laser power when overriding power modulation with a single beam, Figures 4 to 8 are graphs showing the relationship between recording layer composition and override characteristics, and Figure 9 shows the relationship between recording layer composition and override characteristics.
The figure is a diagram for explaining the C/N value and erasure degree during override, and FIG. 10 is an In-3b-Te system composition diagram showing the quality of override characteristics obtained through experiments. ], substrate, 2, 4: protective layer, 3. Recording layer, 5; reflective layer,
6. resin layer.

Claims (1)

[Claims] (1) An information recording medium comprising a substrate and a recording layer whose phase changes reversibly and selectively between a crystalline phase and an amorphous phase depending on light beam irradiation conditions, the recording layer comprising: (In_1_0_0_-_xSb_x)_1_0_0_
-_yTe_y (where x and y are each expressed in atomic % and are within the ranges of 45≦x≦50 and 25≦y≦45, respectively). Characteristic information recording media.