JPH0264930A - Information recording medium - Google Patents

Abstract

PURPOSE:To increase the rate of crystallization, to increase the quantity of the signals to be detected even during high-speed rotation and to improve an erasing characteristic by using a quaternary alloy film to form a recording film which is reversibly changed in phase between 1st and 2nd atomic configurations according to different irradiation conditions of light beams. CONSTITUTION:The recording film formed of the quaternary alloy film which is reversibly changed in phase between the 1st and 2nd atomic configurations according to the different irradiation conditions of the light beams and is expressed by formula I. The component ratios of this compsn. are specified to 48<=x<=52atomic%, 0<y<=10atomic%, 0<z<=7atomic%. The information recording medium of the phase change type which is large in the recording signal even during the high-speed rotation of the information recording medium, is high in erasing speed and has the excellent recording and erasing characteristics is obtd. in this way.

Description

Detailed Description of the Invention [Object of the Invention] (Field of Industrial Application) The present invention relates to an information recording medium on which information can be recorded and erased.

(Prior Art) In recent years, optical discs have attracted attention as information recording media that can record information at high density. Optical disc is CD
The so-called W disc, which is used for playback-only types such as (Compact Disc), electronic document files, etc.
It is classified into rite 0nce type and erasable type which can record and erase information. Currently, read-only optical discs and write-once optical discs have already been put into practical use and are widely used. Further, erasable optical discs are suitable for uses such as still image and moving image files and computer backup memory, so their development has recently become active.

Erasable optical disks can be further broadly divided into magneto-optical types and phase change types. Magneto-optical optical disks record information by reversing the spin of a part of the perpendicularly magnetized film by heating with laser beam irradiation and applying a magnetic field. Using magnetic force effects, the recorded information is reproduced by reading the portion of the reversed spins.

On the other hand, in a phase-change optical disk, a portion of the recording film is made amorphous or crystallized depending on the laser beam irradiation conditions, and the information is read out as information recording and erasing sections based on a corresponding change in reflectance.

Compared to magneto-optical optical discs, phase-change optical discs do not require a magnetic field and can selectively record and erase information using only laser beam irradiation conditions.

Further, a magneto-optical disk that uses the magnetic Kerr effect has a small reproduction signal, whereas a phase change optical disk can reproduce a large signal. Therefore, phase change type optical disks have attracted attention as the next generation of erasable optical disks.

Conventionally, recording films for phase-change optical discs that can reversibly change between crystalline and amorphous state have been made of Te, Ge, and Te.
Ge, InSe, 5bTe.

Semiconductors and semiconductor compounds such as 5bSe are known. However, since Te is crystalline at room temperature, a recording film made of Te has the disadvantage that the amorphous recording portion quickly returns to the crystalline state. Also, Ge and TeGe
has a high melting temperature, so it has the disadvantage that amorphous recording marks cannot be easily formed by laser beam irradiation. Furthermore, recording films made of Ge or Ge compounds have the disadvantage of being susceptible to rust.

Furthermore, as the composition of the recording film of the phase change optical disk, I
Although nSe, 5bTe, 5bSe, etc. have been announced,
Although these recording films do not have the above-mentioned drawbacks, they generally have the drawback that the crystallization speed (erasing speed) is not very fast. Erasable optical disks are required to have high-speed data transfer and override characteristics in comparison with magnetic disks such as hard disks. Therefore, high-speed erasure (high-speed crystallization) is required, but this high-speed crystallization cannot be achieved with the two-element materials described above, so tertiary and quaternary additives are added to the above materials. Developments to speed up the crystallization rate are actively underway.

According to studies by the present inventors, In5bTe is a material that can be crystallized at a relatively high speed other than the above-mentioned materials.

InSb alloy undergoes a reversible phase change between a crystal and another crystal different from this crystal, and In5oSb has the fastest crystallization rate. In the metal compound composition of
Information cannot be erased or recorded. Also, I n x S
A recording film having a composition of b 10G-m (x < 50) can record and erase information, but has the disadvantage that the crystallization rate is slow due to the segregation of sb.

According to the studies of the present inventors, this intermetallic compound composition is In5°Sb. In the In5bTe alloy, which is made by adding a small amount of Te to InSb, good information recording is possible because the recording signal can be increased due to the amorphous nature of Te without impairing the high-speed crystallization characteristics of the intermetallic compound composition. , it has been confirmed that it exhibits erasing properties.

However, such an In5bTe alloy also had the following drawbacks. That is, the amount of Te added is 5 at%
If the value exceeds 1, the high-speed crystallization property of the intermetallic compound composition of In5oSbso is impaired, and a crystal phase with a slow crystallization acceleration, such as 5bTe or InTe, appears, resulting in a slow crystallization rate as a whole.

On the other hand, if the amount of Te added is within 5 at%, it is basically possible to record and erase information, but the signal amount (change in reflectance) is small, especially for high density and high data transfer speeds. However, when the disk rotates at a high speed, the sensitivity becomes insufficient, and the signal amount further decreases.

(Problems to be Solved by the Invention) Conventional phase-change optical disks have a slow crystallization speed, and also lack sensitivity when disks rotate at high speeds due to increased density and data transfer speeds, and the signal amount also increases. There was a problem in that the value decreased.

In order to solve the above-mentioned problems, the present invention provides an information recording medium that has a high crystallization speed, increases the amount of detected signals even during high-speed rotation, and has improved erasing characteristics. The purpose is to

[Structure of the Invention (Means for Solving the Problems) In order to achieve the above object, the present invention provides a first atomic arrangement and a second atomic arrangement based on different irradiation conditions of a light beam. The recording film that undergoes a reversible phase change between .

Further, in the second invention, the recording film whose phase changes reversibly between the first atomic array and the second atomic array under different irradiation conditions of the light beam has the general formula % 0<a≦ It is characterized by being made of a quaternary alloy film consisting of 10 atomic % and 0b≦3 atomic %.

(Function) In the information recording medium of the present invention, In5°Sb. InSb alloy with Te and Se added to
Since the 5bTeSi alloy is used, it is possible to provide a phase change type information recording medium with excellent recording and erasing characteristics, which has a large recording signal and a high erasing speed even when the information recording medium rotates at high speed.

As a result of careful study by the inventor, Ins. Sb.

I which added Te and Si to I nSb with a composition close to
In a recording film made of n5bTeS i alloy, when information is recorded under certain conditions of irradiation with a light beam, the signal increases due to the amorphization of Te. Furthermore, it has been discovered that when information is erased under different irradiation conditions with a light beam, crystallization occurs quickly due to the effect of adding SL, which tends to crystallize.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

As shown in FIG. 2, the information recording medium according to the present invention has a structure in which a substrate 20, a first protective film 21, a recording film 22, a second protective film 23, and a UV cured film 24 are laminated in this order. It has become.

The substrate 20 is made of glass, plastic, or polycarbonate. The first and second protective films 21 and 23 are made of, for example, 5 in 2 and are used to prevent the recording film 22 from melting and forming a hole when the recording film 11!22 is irradiated with a laser. Furthermore, the UV cured film 24 prevents scratches that may occur during handling. Further, the recording film 22 is formed using the general formula % (where 48≦X≦52 atomic %, 0xy≦10 atomic %,
0xz≦7 atomic%), or a quaternary alloy film consisting of the general formula % (0<a≦10 atomic%, 0xb≦3 atomic%). . This recording film 22 undergoes a reversible phase change between a first atomic arrangement and a second atomic arrangement under different irradiation conditions of the light beam.

Hereinafter, specific examples of the above information recording medium will be described in detail.

(Example 1) Using the sputtering apparatus shown in FIG. 1, an information recording medium shown in FIG. 2 was formed.

This sputtering apparatus 1 includes a rotating base 2, a valve 4.5, and targets 6-A, 7-A, 8-A, and 9-A.

Electrodes 6-B, 7-B, 8-B, 9-B, power supplies 6-C, 7
-C, 8-C, 9-C, shutter 6-D.

It consists of 7-D, 8-D, and 9-D.

First, a polycarbonate disk-shaped disk substrate 20 is set on a rotating base 2, a valve 4 is opened, and a cryopump (not shown) is used to move a sputtering apparatus 1 to a 10-6
The vacuum was pulled down to torr.

In this state, open the valve 5 and set the Ar gas flow rate to 20
While introducing 3CCM, adjust the opening and closing of the valve 4 to set the gas pressure in the device 1 to 5 m torr. It undergoes a reversible phase change between

Hereinafter, specific examples of the above information recording medium will be described in detail.

(Example 1) Using the sputtering apparatus shown in FIG. 1, an information recording medium shown in FIG. 2 was formed.

This sputtering apparatus 1 includes a rotating base 2, a valve 4.5, and targets 6-A, 7-A, 8-A, and 9-A.

Electrode 6-B, 7-8, 8-B, 9-B, power supply 6-C, 7
-C, 8-C, 9-C, shutter 6-D.

It consists of 7-D, 8-D, and 9-D.

First, a polycarbonate disk-shaped disk substrate 20 is set on a rotating base 2, a valve 4 is opened, and a cryopump (not shown) is used to move a sputtering apparatus 1 to a 10-6
The vacuum was pulled down to torr.

In this state, open the valve 5 and set the Ar gas flow rate to 20
While introducing 8CCM, adjust the opening/closing of valve 4 to set the gas pressure in device 1 to 5 mtorr.
9-D should be opened at the same time In4ssb, 2) g2Te5
A thin film having a composition of Si was started to be formed on the Si film. After forming the recording film to a thickness of about 1000 angstroms in about 1 minute and 30 seconds, the shutters 7-D, 8-D, and 9-D are closed, and at the same time, the R0F power supplies 7-C, 8-C, and 9 are turned on. −
C was turned off to complete the film formation.

After that, turn on R, F, t4a*6-C again;
An SiO□ film was overcoated to a thickness of 1000 Å in the same step as before.

SiO2 (1000 angstroms) / (Inngsb52) 92T'e5 on the disk substrate 20
S 1s (1000 angstroms) /S i
This sample was formed into a film with a thickness of 0.02 (1000 angstroms) after leaking the sputtering device 1 to the atmosphere, applying a UV curable resin using a spin coater (not shown), and irradiating it with UV light using a UV irradiation device. Hardened.

The configuration of the sample created in this way is an information recording medium as shown in FIG. That is, in this sample, SlO is deposited on a disc-shaped polycarbonate substrate 20.
□The film 21 has a thickness of 1000 angstroms, (I n4
ssbs2) 9xTes Si3 recording film 22 is 10
The structure is such that a 5in2 film of 1000 angstroms and a UV cured film of about 5 um are laminated in this order.

Next, samples were fabricated under exactly the same fabrication conditions as above, with only the recording film varying the amounts of Te and 81. The compositions of the recording films in these samples are as follows.

■(I n4asbsz) esTes +■(I n
4ssbsz) 5tTetos ii *■(I n
4ss bs2) ssT e tos i 7.

■ (I n4ssbsz) 94T'e'S
S.L.&.

■(I n4ssbsz) 5zTes S i3.

■(1n 4sS b 52) 90T e t.

The samples thus prepared were evaluated using a performance evaluation device.

At a rotation speed of 200 rpm, at a radius of about 55 mm,
Each sample was evaluated by performing the following processing.

(1) Initial Crystallization Since the recording film immediately after film formation is amorphous, it is crystallized for one track by a continuous light beam of 10 mW. At this time, the same track is irradiated with the laser any number of times until crystallization is completed.

(2) Recording pits in an amorphous state are formed on the tracks of the crystallized recording film using a pulsed laser beam having a recording laser power of 15 mw, a frequency of 3 MHz, and a duty of 50%.

(3) Erasing A continuous light beam of lQmw, which is the same as that used in the initialization, is irradiated once for one track to return the amorphous pits to crystals and erase them. After the steps (2) and (3), reproduction is performed using a continuous laser beam of 0.8 mw, and the magnitude of the reproduced signal from the amorphous recording pit and the remaining erased signal after erasing are measured. The size was measured on an oscilloscope. The measurement results are shown in FIG.

Figure 3(a) shows the magnitude of the reproduced signal from the recorded bit and the remaining amount after erasure with respect to the amount of Si added when the amount of Te added is fixed at 5 at% to InSb with a composition close to the intermetallic compound composition of In4asbs2. Indicates the magnitude of the signal.

From this measurement result, it was found that only 5 at% of Te was added and Si
In the case without St, the erased residual signal is very large, but as the amount of Si added increases, the erased residual signal decreases, and in the case of 3 at% St added, complete erasure is achieved. There was found.

It was also found that the reproduction signal from the recorded bits gradually increased due to the addition of St.

FIG. 3(b) shows the magnitude of the recording signal and the amount of erased data remaining with respect to the amount of St added when the amount of Te added is fixed at 10 at %. As can be seen from this measurement result,
When Te is added at only 10 at%, the signal hardly disappears, but when Si is added at 3 at%, it disappears completely. However, when the amount of St is further increased, the residual signal becomes larger and the reproduced signal from the recorded bit becomes smaller.

As is clear from these experimental facts, it has been found that the amount of Te added is preferably 10 at% or less, and the amount of Se added is preferably 7 at% or less.

(Example-2) The layer structure was exactly the same as that of the sample produced in (Example-1), but only the composition of the InSb alloy was Ins.

Samples were prepared by replacing sb, and In52Sb4a. The thickness of each layer of these samples was the same as that of the sample prepared in (Example-1).

The amounts of Te and Si added were also exactly the same as in the sample prepared in (Example-1).

When these samples were subjected to dynamic evaluation under the same conditions as in Example 1, results completely similar to those shown in FIGS. 3(a) and 3(b) were obtained.

(Example-3) In the same manner as (Example-2), the layer structure was exactly the same as that of the sample produced in (Example-1), but only the composition of the InSb alloy was In4. Samples were prepared in which Te and St were added in place of s b55+ I n and sS b45, and the same dynamic evaluation as in Example 1 was performed.

As a result, the composition of the intermetallic compound is In5°Sb.

For InSb having such a composition that deviates greatly from the above, no effect of adding Te and Se was observed at all.

From the above results, the appropriate composition of the In5bTeSi alloy film according to the present invention is expressed by the general formula (Inx S b + oo-x ) +00-y-m
When Tey S l z, the content is 48≦X≦52at%, 0kuy≦10at%, 0kuz, respectively.
It was found that ≦7at%.

That is, in an In5bTeSi alloy film in this composition range, by first adding Te to InSb with a composition near the InSb intermetallic compound composition, it is possible to increase the detected signal amount by making Te amorphous during recording. It is possible. Furthermore, when erasing information, due to the high-speed crystallization property of St, the erasing properties of the alloy as a whole are improved, and it exhibits good properties when the information recording medium is rotated at high speed.

[Effects of the Invention] As explained above, in the information recording medium of the present invention,
It has a high crystallization speed and can provide good recording and erasing characteristics even during high-speed rotation.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a four-source sputtering apparatus for producing an information recording medium according to the present invention, FIG. 2 is a cross-sectional view showing an example of the layer structure of an information recording medium according to the present invention, and FIG. 3 is a diagram according to the present invention. FIG. 2 is a measurement diagram showing the addition effect when Te and Si are added to InSb having a composition near the intermetallic compound composition used in the recording film of the information recording medium. 20 Substrate 22 Recording film

Claims (1)

[Claims] (1) A substrate, and a general formula (In_xSb_1_0_0_-_x)_1_0_0_ which is provided on this substrate and whose phase changes reversibly between a first atomic arrangement and a second atomic arrangement depending on different irradiation conditions of the light beam.
-_y_-_zTe_ySi_z48≦x≦52 atomic%
, 0<y≦10 at.%, and 0<z≦7 at.%. (2) a substrate, which is provided on this substrate and has a general formula (In_4_8Sb_5_2)_1_0_0_-_a_ which reversibly changes phase between a first atomic arrangement and a second atomic arrangement under different irradiation conditions of the light beam;
−_bTe_aSi_b0<a≦10 atomic%, 0<b≦
1. An information recording medium comprising: a recording film made of a quaternary alloy film expressed as 3 atomic %.