JPH0264929A - 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<=10atomic%. The information recording medium of the phase transition 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] (Industrial Application Field) 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
(Coll1pact Dlse), a so-called write once type used in electronic document files, and an erasable type that can record and erase information. At present, read-only optical discs and VRITE 0nce type 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 optical disks have attracted attention as next-generation 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, Te
A recording film made of the above has the disadvantage that the amorphous recording portion quickly returns to the crystalline state. Also, Ge and TeG
Since e has a high melting temperature, 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. I
The nSb alloy undergoes a reversible phase change between a crystal and another crystal different from this crystal, and In has the fastest crystallization rate.

With a metal compound composition of Sb5°, information cannot be erased or recorded. Also, In, Sb+oo-t (x<50)
Although it is possible to record and erase information with a recording film having the composition, it has the disadvantage that the crystallization rate is slow due to the segregation of sb.

According to the studies of the present inventors, an In5bTe alloy in which a small amount of Te is added to InSb with an intermetallic compound composition near In5°5bso can be used without impairing the high-speed crystallization characteristics of the intermetallic compound composition. , it has been confirmed that since the recording signal can be increased due to the amorphous state of Te, it exhibits good information recording and erasing characteristics.

However, such In5bTe alloy also has the following drawbacks. That is, the amount of Te added is 5at
%, the high-speed crystallization property of the intermetallic compound composition of 1nsoSbso is impaired, and crystal phases with slow crystallization acceleration, such as 5bTe and InTe, appear, 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. In order to solve the above-mentioned problem, the present invention has a high crystallization speed, increases the amount of detected signals even during high-speed rotation, and improves the erasing characteristics. The purpose is to provide an information recording medium that can perform

[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 under different irradiation conditions of a light beam. A recording film whose phase changes reversibly between the general formula % 48≦X≦52 atomic %, 0y≦10 atomic %.

It is characterized by being made of a quaternary alloy film of 0<Z≦10 atomic %.

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 is formed by the general formula % 0a≦ It is characterized by being made of a quaternary alloy film consisting of 10 atomic % and 0b≦5 atomic %.

(effect) In the information recording medium of the present invention, Ins.

Since the In5bTeGe alloy is used, which is an In5bTeGe alloy in which Te and Ge are added to the InSb alloy with a property near 5b50, the recording and erasing characteristics are such that the recording signal is large and the erasing speed is fast even when the information recording medium rotates at high speed. It is possible to provide an excellent phase change type information recording medium.

As a result of the inventor's keen studies, In5bT is obtained by adding Te and Ge to InSb with a composition near In5oSb5°.
In a recording film made of an eGe alloy, when information is recorded under certain light beam irradiation conditions, 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 Ge, which is less likely 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 5i02, for example, and prevent the recording film 22 from melting and forming holes when the recording film 22 is irradiated with a laser. Furthermore, the UV cured film 24 prevents scratches that may occur during handling. The recording film 22 has the following general formula: % (48≦X≦52 atomic %, 0≦y≦10 atomic %).

0<z≦10 atomic%) or a quaternary alloy film consisting of the general formula % (0<a≦10 atomic%, 0b≦3 atomic%) It is. 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.

Electrode 6-B, 7-8.8-B, 9-B, power supply 6-C, 7
-C, 8-C, 9-C, shutter 6-D.

It is composed 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 valve 5 and set the gas flow rate to 20.
While introducing 3 CCM, the opening and closing of the valve 4 was adjusted to set the Ar gas pressure in the apparatus 1 to 5 m torr.

Next, the radio frequency of 13.56MHz (hereinafter referred to as R,F)! Turn on R6-C and connect electrode 6-
R, F and power of about IKW were applied to B, and sputtering using Ar gas was started on the 5in2 target 6-A. After pre-sputtering for about 2 minutes, shutter 6
-D is opened, and after forming a 5in2 film on the disk substrate 20, the shutter 6-D is closed, R, F, and the power supply 6-C are opened.
was turned off to complete the formation of the 5tO2 film.

Next, turn on R, F, and power supplies 7-C, 8-C, and 9-C, and apply 200 W to electrodes 7-B, 8-B, and 9-B, respectively.
R and F powers of 20 W and 20 W were applied, respectively, and sputtering of In4sSb, 2-alloy target 7-A, Te target 8-A, and Ge target 9-A using Ar gas was started. Note that the electrodes 8-B and 9-B and the shutter 8-O9-D are not shown because they are not visible in the drawing of FIG.

After about 2 minutes of bliss sputtering, shutter 7-O8-D,
In4g5bs2), which simultaneously opens 9-D. Tes
A thin film having a composition of Ge5 was started to be formed on the 5in2 film.

After forming this 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
close, and at the same time R8F power supply 7-C, 8-C, 9
-C was turned off to complete the film formation.

Thereafter, R, F, and power source 6-C were turned on again, and a 5in2 film was overcoated to a thickness of 1000 angstroms in the same process as before.

5iOz (1000 angstroms) / (I n4ssbs2) eoTes S on the disk substrate 20
es (1000 angstroms)/SiO2(1
This sample, which was formed into a film with a thickness of 0.000 angstroms, was made by leaking the sputtering device 1 to the atmosphere, applying a UV-curable resin using a spin coater (not shown), and applying UV-curable resin.
This was cured by irradiating it with UV light using an irradiation device.

The configuration of the sample created in this way is an information recording medium as shown in FIG. That is, in this sample, SiO is placed on a disc-shaped polycarbonate substrate 20.
2 film 21 has a thickness of 1000 angstroms, (I nnas
bs□), an oTe5 Ses recording film 22 of 1000 angstroms, a SiO□ 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 those described above, with only the recording film varying the amounts of Te and Ge. The compositions of the recording films in these samples are as follows.

■(In4ss b52) 95T eq.

■’(In4aSb, 2)asTe+oGe5.

■(I n asS b 52) 80T e +oG
e1G.

■C1n4aSb, 2)esTe, Ge2゜■(In4
aSbs2) qoTes Ges 1■(I n a
ss b 52) 90T et.

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

Each sample was evaluated by performing the following treatment at a rotation speed of 2000 rpm and at a position with a radius of about 55 mm.

(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 10 mW, which is the same as that used in the initialization, is irradiated once for one track to return the amorphous bits 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 magnitude of the reproduction signal after erasure with respect to the amount of Ge added when the amount of Te added is fixed at 5 at% to InSb with an intermetallic compound composition close to that of In4sSb, 2. Indicates the magnitude of the unerased signal.

From these 4 dream 1 constant results, Te added only 5 at%,
When Ge is not added, the erased residual signal is very large, but as the amount of Ge added increases, the erased residual signal becomes smaller, and in the case of 3 at% Ge added,
It turned out that it was completely erased.

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

FIG. 3(b) shows the magnitude of the recording signal and the amount of erased data remaining with respect to the amount of Ge added when the amount of Te added is fixed at 10 at%. As can be seen from this measurement result, the signal hardly disappears when only 10 at% of Te is added, but it disappears completely when 2 at% of Ge is added. However, when the amount of Ge is further increased, the remaining signal becomes larger.

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 Ge added is preferably 10 at% or less.

(Example 2) A sample was prepared with exactly the same layer structure as the sample prepared in Example 1, except that only the composition of the InSb alloy was changed to In5°5b50 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 Ge 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 in (Example-2), the layer composition was exactly the same as that of the sample produced in (Example-1), but only the composition of the InSb alloy was replaced with In4sS bss, Ins, and Sb4s. A sample to which Te and Ge were added was prepared, and the same dynamic evaluation as in (Example-1) was performed.

As a result, the composition of the intermetallic compound is In5oSb.

For In5b having such a composition which deviates greatly from the above, no effect of addition of Te and Ge was observed at all.

From the above results, the appropriate composition of the In5bTeGe alloy film according to the present invention is expressed by the general formula (Ins 5bloo-x) +00-F -Te
, Gem, the content is 48≦, respectively.
X≦52at%, 0kuy≦10at%, 0kuz≦10a
t%.

That is, in an In5bTeGe alloy film in this composition range, by first adding Te to InSb, which has 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, the erasing properties of the alloy as a whole are improved due to the high-speed crystallization property of Ge, 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 Ge 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, which is provided on this substrate and has a general formula (In_xSb_1_0_0_-_x )_1_0_0 that reversibly changes phase between a first atomic arrangement and a second atomic arrangement depending on different irradiation conditions of a light beam.
_-_y_-_zTe_yGe_z48≦x≦52 atomic%, 0<y≦10 atomic%, 0<z≦10 atomic%. Medium. (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_aGe_b0<a≦10 atomic%, 0<b≦
1. An information recording medium comprising: a recording film made of a quaternary alloy film represented by 5 atomic %.