JPH01302549A - Information recording medium - Google Patents

Abstract

PURPOSE:To obtain the recording medium which allows stable recording and erasing of information by forming a recording layer which generates a phase change reversible between different phases by irradiation of a light beam by adding N to an alloy film consisting of the specific constitutional formula. CONSTITUTION:An optical disk is constituted by forming a protective layer 12, the recording layer 13, and the protective layers 14, 15 in this order on a substrate 11. The recording layer 13 is formed by adding the N to the ternary alloy expressed by the formula at this time. In the formula, x attains the value of 48.0<=x<=52.0atomic%, y of 0.05<=y<=5.0atomic%. The recording layer 13 constitutes the phase mixed with the fine crystal of an InSb intermetallic compd. and the fine crystal of InTe or Sb Te at the time of initializing and erasing of the information and constitutes the mixed phase in which the fine crystal of InSb coexists in the amorphous InTe or Sb Te at the time of recording. The speed of the phase change, i.e., recording and erasing of information is, therefore, increased and the stability of the recording film and the recorded part of information is improved by the addition of the N.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) This invention relates to an information recording and erasing method that causes a phase change in a recording layer by irradiating it with a light beam such as a laser beam. Regarding recording media.

(Prior Art) In recent years, optical disks have been attracting attention as information recording media that can be used as a large-capacity memory.

Then, depending on the laser beam irradiation conditions, holes or bubbles are formed in the recording film formed on the glass or resin-based transparent substrate to perform one-time recording.
The iteQnce type distribution system has already been put into practical use for electronic document files and the like.

In line with this, erasable optical discs have been developed in which previously recorded information can be erased and then recorded again, and some of these discs are on the verge of being put into practical use. Erasable optical disks can be roughly divided into magneto-optical optical disks, in which the spin direction of a perpendicularly magnetized film is selectively changed using a magnetic field and heat generated by laser beam irradiation, and magneto-optical optical disks, in which the recording film is changed into one structural state depending on the laser beam irradiation conditions. Phase change forms that reversibly change from one to another structural state are currently known.

Such phase-change materials include, for example,
Qe, Te Qe, In Se, 3b
3e.

Examples include semiconductors such as 5bTe, semiconductor compounds, and intermetallic compounds. These selectively take two states, a crystalline phase and an amorphous phase, depending on the temperature, and in each state, N-n
Since the complex refractive index expressed by -1k is different, these two states are reversibly changed by heat treatment with a laser beam to record and erase information (S, R, 0vshins
ky Metallurgical Transact
ions 2 6411971).

On the other hand, unlike the above-mentioned method, there is also a technique in which information is recorded and erased by reversibly changing the phase between different crystals 94 by irradiation with a laser beam. A 1n-3b alloy is known as a material that undergoes such a phase change.

1 ml of In-Sb alloy becomes fine crystal grains when irradiated with a weak laser beam having a relatively long pulse width. Also,
By irradiating a laser beam with a short pulse width and high power, these fine crystal grains grow into relatively large crystals in a short period of time. These two crystal structures have different complex refractive indices,
When performing reproduction by irradiating a laser beam, the crystal state is distinguished, for example, based on the difference in the amount of reflected light.

However, all of the above-mentioned materials used in the technology for recording and erasing information by changing the phase between crystalline and amorphous have a slow crystallization rate and require a long time to erase information at the initial stage. Put it away. In addition, the part of the recording layer where information is recorded is usually amorphous, but amorphous has low stability when fishing on a boat, and will crystallize if used for a long time in a high-temperature environment.
This has the disadvantage that it becomes difficult to distinguish between the recorded portion and the non-recorded portion.

On the other hand, in the case of an optical disc in which the recording layer is formed of 1n-3b and the phase changes between different crystalline materials, the portion where information is recorded is crystalline, and the recorded information is stable. . Further, a composition close to the intermetallic compound of Ir1soSbso has the advantage that the crystallization rate is extremely fast.

However, in this case, since Sb segregation does not occur, it is substantially difficult to record information. On the other hand, attempts have also been made to form a recording layer using an alloy having a composition in which Sb is slightly more abundant than In5oSbso.

By irradiating the recording layer with a laser beam, the recording layer becomes a mixed phase of In5oSbso crystal grains and Sb crystal grains, and the size of the Sb crystal grains changes depending on the laser beam irradiation conditions. This allows the recording level to be maintained. However, since the crystallization speed of sb is low, the speed of initialization and erasing is low, and these cannot be made faster, which may result in defective initialization and unerased data. Furthermore, when recording information, if the optical disk rotates at high speed, there is a risk that sufficient crystal growth may not occur, resulting in insufficient recording.

(Problems to be Solved by the Invention) In other words, in conventional information recording media, it is not possible to initialize and erase information at high speed, and it is not possible to obtain excellent characteristics in both recording and erasing information. could not.

The present invention has been made in view of the above circumstances, and provides an information recording medium that can perform initialization and erasure of information at high speed, and that can obtain excellent characteristics in both recording and erasing information. The purpose is to

[Structure of the Invention] (Means for Solving the Problems) An information recording medium according to the present invention has a recording layer that undergoes a reversible phase change between different phases when irradiated with a light beam. It is characterized in that it is formed of an alloy consisting of the formula (% formula % ≦5.0 atomic %) to which N is added.

(Function) In this invention, the recording layer has a composition within the above-mentioned range. An alloy with this composition can be formed by 1n depending on the light beam irradiation conditions.
3b intermetallic compound microcrystals and in Te or 5bTe
A mixed phase of fine crystals of lnTe or 5bTe
The phase changes between the amorphous state and a mixed phase in which fine crystals of In5b are mixed.

In such a composition, the crystallization rate is fast, and
Since the phase change speed between microcrystals and a mixed phase in which microcrystals are mixed in an amorphous state is fast, initialization, information recording, and erasing speeds can be increased. Furthermore, since microcrystals are mixed in the area where information is recorded, information can be recorded stably.

By adding N to the film, the crystallization rate increases rapidly, which improves the thermal stability and information stability of the film, making it possible to obtain stable information recording and erasing characteristics. .

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

As the inventor has already filed as Japanese Patent Application No. 62-230004, (InxSbtoo-x)1oo-yTey(48,0
A ternary alloy film consisting of 0 atomic % (≦X≦52.0 atomic %, 0≦y≦5゜0 atomic %) exhibits excellent information recording and erasing properties. In other words, 1nSb forming this alloy film
The alloy has the property of fast crystallization, which is an advantage of open metal compounds.

In sb T which added a small amount of Te to this 1n3b alloy
e In the ternary alloy film, information is recorded and erased by the following mechanism.

When a light beam is irradiated onto a distribution layer made of InSbTe, depending on the irradiation conditions of the light beam, a phase containing a mixture of fine crystals of InSb intermetallic compound and fine crystals of (n7'e or 5bTe) and a phase of inTe Or, the phase changes between 5bTe amorphous and n3b fine crystals mixed therein. When initializing and erasing information, the phase becomes a mixture of [nSb intermetallic compound microcrystals and lnTe or 5bTe microcrystals, and when information is recorded, Jn l"e
Or, it becomes a mixed phase in which fine crystals of (n 3b) are mixed in the amorphous state of Sb Te.

Therefore, (InxSbtoo-x)too-yl'eV(48≦
It can be seen that the ternary alloy film consisting of X≦52 atomic % and 0xy≦5 atomic % has excellent information recording and erasing characteristics even at high speeds. However, when the amount of Te added exceeds 5 atomic %, the amorphous nature during information recording increases, so the magnitude of the reproduced signal from the area where information is recorded increases, but at the same time, erased residue occurs. There is a problem with this.

It is a well-known fact that Te itself is a material that is easily oxidized.On the other hand, the aforementioned rntoo-xSbx (48≦X≦52 atomic%) alloy has almost no segregation of sb, so the recorded signal is small. . In this case, in order to record information effectively, Te is 0.
．． 0.05 atom % or more is required.

It is a well-known fact that Te itself is a material that easily oxidizes, and the fine crystal grains of In5oSbso and Sb
There are also some problems with the storage stability of the information-recorded portion consisting of an amorphous mixed phase of Te.

Therefore, as a result of careful study by the present inventor, the above-mentioned In5
By roughly adding N to the bTe alloy, the information reproduction signal is increased without impairing the high-speed erasing characteristics, and the crystallization temperature rises rapidly, which improves the storage stability of the recording film and improves the information recording area. The storage stability was also found to be significantly improved.

The effect of this addition of N is not clear because the amount of N added in the lnSbTeN film cannot be quantified by normal ICP analysis or EDX methods, but since the atomic radius of N atoms is small, adding this 4 It is thought that this is because SbTe becomes amorphous more easily in the original alloy film than in the film to which only Te is added.

In addition, because the atomic radius of N atoms is small, the effect of N addition on structural changes that occur during the crystallization process is small.
This is probably because the characteristics of high-speed crystallization are not hindered. Furthermore, the addition of N to the lnSb 7e IJ can be qualitatively confirmed by Ausch electron spectroscopy.

For example, as shown in FIG. 1, the information recording medium according to this embodiment includes a substrate 11, a recording layer 13, and a protection II! 12,1
4.15.

The substrate 11 is made of a material that is transparent and has little change over time, such as glass or polycarbonate resin. A group (iM) is formed on this substrate 11.

(7) On the M board 11, there is a symbol "l!" ! 112, F2 record R
13, a protection layer 14 and a protection layer 115 are formed in this order. Ho II! ! ff12.14 is made of SiO2, for example, and prevents the recording layer 13 from melting. The protective layer 15 is made of an ultraviolet curing resin and has a 1 m capacity to prevent scratches from occurring on the surface during handling.

The recording layer 13 is made of an alloy having the composition described above,
Due to differences in laser beam irradiation conditions, the phase changes between microcrystals and a mixed phase in which microcrystals are mixed in an amorphous state.

(Experimental Example-1) The information recording medium shown in FIG. 1 was manufactured as shown below using the reactive sputtering container 20 shown in FIG. 2.

First, the reaction vessel 20 was evacuated to 10<-6 >torr using a cryopump (not shown). Next, the polycarbonate substrate 11 is rotated together with the rotating base 21, and the valve 2
2, Ar gas was introduced into the reaction vessel 20 at a flow rate of about 1108 CC.

Next, adjust the opening and closing of the valve 23 to prevent the Ar inside the reaction vessel 2°.
After setting the gas pressure to 6 mtorr, electrode 2
4, a radio frequency power (R, F, power) of 13.56 MH2 was applied to 400 W to cause plasma discharge by Ar gas on the SiO2 target 17. After about 2 minutes of pre-sputtering, shutter 3
0 and started forming a 5i02 dielectric film on the polycarbonate substrate 11. 5i0 of about 1000A after 6 minutes
After forming two films, set the shutter 30 to R and F.

I turned off the power.

Next, N2 gas was introduced into the reaction vessel 20 through the valve 22. The flow rate ratio N2 of this introduced Ar gas and N2 gas
/Ar was set to 0.05.

In addition, the electrode 26 has a power of 200W, the l pole 25 has a power of 20W,
F. Power was applied to generate a plasma discharge using a mixed gas of Ar gas and N2 gas on the in 4 s Sb 52 alloy target 29 and the Te target 28.

After about 2 minutes of bliss sputtering, shutter 31.32
was opened at the same time, and during SiO2 training (In4a 5bs2
)95 Tes +N film formation was started. After about 4 minutes (Ill<asbs2)c+5Tes+Nl
! 1000, the limb and shutters 31 and 32 were closed, and the R, F, and power were turned off. The introduction of N2 gas into the reaction vessel 10 was stopped, and (Illsa 5b
s2) 95 Tes + S+0211 on NMR and 1000 AtclL. Thereafter, the sample was taken out from the reaction vessel 20 and the cured resin was irradiated with a spin code and v-light using a spinner (not shown) to cure it. (Hereinafter, this sample will be referred to as sample D).

Flow of N2 gas and Ar gas ff1 during film formation of recording film
tll, the value of Nz/Ar is O (no N2 gas), 0°0
1.0.05, 0.02, 0.5, 1.0, and 1 No. were manufactured under the same manufacturing conditions as above, but with different N content (In
An information recording medium was manufactured in which a recording film made of 4aSbs2)N was sandwiched between S+02 films. These samples are hereinafter referred to as sample A, sample B, sample C, sample E, sample F, and sample G.

(Experiment Example-2) Each sample A-G manufactured by the method shown in Experiment Example-1 above
was applied to a gravity evaluation device to evaluate its characteristics. The information recording medium rotates at a high speed of 11,000 rpm. The evaluation procedure is shown below.

(1) Immediately after initial crystallization, the recording film, which is in an amorphous state, is irradiated with a series of 7 mw laser beams to form an equilibrium phase RNS.

5bso, and the crystal phase changes to SbTeN.

(2) At the beginning of recording, the crystallized recording layer is irradiated with a laser beam of laser power 121RL pulse width 1Q Q n5ec duty 50% to form In5o on the crystal in the equilibrium phase.
A recording bit consisting of a mixed phase of a crystalline phase of Sbso and an amorphous phase of SbTeN was formed.

Thereafter, the reproduced signal from this bit was read out using continuous reproduction light from a Q, 5 mW laser beam, and the signal amplitude was measured.

(3) Elimination basis 5 Basically, the initial crystallization and agitation procedure of (1) produces 7 mw.
The recording bit was irradiated with a continuous laser beam to return the recording bit consisting of a mixed phase of a crystalline phase and an amorphous phase to a crystalline layer in an equilibrium phase. However, in initial crystallization, the same part must be continuously irradiated many times until it is completely crystallized, but when erasing information, only one revolution is irradiated, and if the crystal does not completely return to the equilibrium phase, As the remaining information is deleted,
0°51! This size was determined using a reproducing laser beam of 1W.

(1; 3. Bottom margin) Table 1 Evaluation Results Table 1 shows the evaluation results. According to this evaluation result, 1
Even at high speed rotation of 20OrpIIl, In50S
1) It can be seen that the amplitude of the recording signal increases rapidly as N is added without impairing the high speed crystallization which is an advantage of the intermetallic compound composition of 50. That is, T
When e is added at 5 atomic % or more, the signal increases, but the erased residue also becomes larger, but in the case of Te +N, only the signal increase is detected without the erased residue.

(Experiment Example 3) Using exactly the same method as in Experiment Example 1 above, R, F, and power for injecting in and sb targets were gradually changed to replace the recording film consisting of (In4s 81152 )95 T135 +N. (In<5sb5s>9sTes+N.

(Inso 5bso) 95 Tes +N.

(rns2Sb4 e)95 Te +N.

(InssSb4s) A record consisting of c+5Tes+N!
19 to 5iO211! A sandwiched information recording medium was manufactured. At this time, the N2/Ar flow ratio was 0°05, which had the best characteristics according to the evaluation results (Table 1) shown in Experimental Example 2 above.

Similar to Experimental Example 2, when it was applied to the motion evaluation device, (I
n455bS5 ) 95 Tes +N, 3 b
-rich (Ill), the amplitude of the recorded signal was as large as 200 mw, but it could not be erased.
The signal amplitude did not increase even when N was added because the composition shifted too far to the -rich side.

(Inso 5b50 )95 Tes +N and (I
Regarding the information recording medium with the recording film made of ns2Sb4a)c+5Tes+N, almost the same results as in Experimental Example 2 could be obtained.

(Experimental Example 4) Using exactly the same manufacturing method as in Experimental Example 1 above, only a recording film of (In48Sbs2)gsTe5+N with a thickness of 3000 mm was fabricated on a small piece of glass substrate. Flow ratio N of N2 gas and Ar gas
2/AI'' is O, 0, as in (Experimental Example 1)
The test was carried out at 01, 0, 05, Oll, 0°2, 0.5, 1.0.

These samples were subjected to differential scanning calorimetry (DSC) to measure the crystallization temperature. The results are shown in FIG.

As shown in FIG. 3, as the amount of (In48Sb52)95Te5+N added increases, the crystallization temperature rises rapidly. Therefore, the reason why the number of initial crystallizations increased and information remained after deletion in Samples F and G shown in Experimental Example 2 is because
This is thought to be due to the crystallization temperature being too high. However, if the N2/AI'flXt amount ratio is 0.5 or less, the higher the crystallization temperature, the better the thermal stability of the film itself and the storage stability of recording bits. Considering the evaluation results of Experimental Example 2, it is appropriate that the N2/Ar flow rate during production of the recording film be 0.5 or less.

[Effects of the Invention] As explained above, according to the present invention, it is possible to provide an information recording medium that has excellent information recording and erasing characteristics, and excellent recording film stability and information stability. .

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an information recording medium according to an embodiment of the present invention, and FIG. 2 is a sectional view showing an information recording medium according to an embodiment of the present invention. ! FIG. 3 is a diagram showing the relationship between the N2 Ar flow fog ratio and the crystallization temperature in the information recording medium of the present invention. 11...Substrate 13...Recording film

Claims (1)

[Scope of Claims] An information recording medium comprising a substrate and a recording layer provided on the substrate and causing a reversible phase change between different phases when irradiated with a light beam, wherein the recording layer is the general formula (InxSb_1_0_0_-_X)_1_0_0_-
_YTey (48.0≦x≦52.0 atomic%, 0.05
An information recording medium characterized in that it is made by adding N to an alloy film consisting of y≦y≦5.0 atomic %).