JPH0361081A - Information recording medium - Google Patents

Abstract

PURPOSE:To enable initialization, recording and deletion to be performed at high speed and ensure that recorded information is stable and reliable by forming a recording layer with an alloy of specific composition. CONSTITUTION:A substrate 1 is formed with plastic such as polyolefin, epoxy, polycarbonate or polymethacrylate or glass. A protecting layer 3, a recording layer 2, a protecting layer 4 and a protecting layer 5 are formed sequentially on the substrate 1. The recording layer 2 is formed with an alloy of such a composition as expressed by (Inx, Sby, Tez)100-alphaMalpha (where x, y, z, alpha are atomic %, x+y+z=100 and are in a range of 25<=x<=55, 27<y 55, 20<=z<=50, 0<alpha<=20 respectively. M is at least, one kind of element selected from a group of Se, As, P, S, Ge, Si, B, C, N or Ar).

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention provides information by irradiating a recording layer with a light beam such as a laser beam and inducing a phase change in the irradiated area depending on the irradiation conditions. is recorded or erased, and the reflectance associated with this phase change,
The present invention relates to an information storage medium that reproduces information by detecting changes in optical characteristics such as transmittance.

(Prior Art) Conventionally, large-capacity information recording media on which information can be recorded and erased, a type of so-called erasable optical disk, have been used.
Phase change types are widely known. This phase change type information recording medium includes a substrate made of, for example, glass or plastic (polycarbonate resin, polymethyl methacrylate resin, etc.), and a recording layer formed on this M plate.

For example, chalcogenide alloys such as GeTe are known as materials for forming this recording layer, and these can be transformed between crystal and amorphous by irradiating them with light under different conditions (for example, a laser beam). Since the phase changes reversibly, information can be recorded and erased using this phase change, and changes in optical properties such as reflectance or transmittance accompanying these phase changes can be read.

As such a recording layer, a material having a eutectic composition or a material forming an intermetallic compound that easily undergoes a phase change depending on the light irradiation conditions is suitable.

(Problem to be Solved by the Invention) However, although alloys such as GeTe that have been conventionally used as the recording layer of phase change information recording media satisfy the above conditions, they still do not have sufficient characteristics as information recording media. It cannot be said that the In particular, it is desired to speed up initialization, recording, and erasing. Also, crystal-
When recording or erasing information through a phase change between amorphous states, the recorded area usually becomes amorphous, but since amorphous states generally have relatively low stability, it is necessary to make the amorphous state more stable. It is also required to do so. Furthermore, it is also required to further improve reliability.

The present invention was made in view of the above circumstances, and provides an information recording medium that can speed up initialization, recording, and erasing, has stable recorded information, and is highly reliable. The purpose is to

[Structure of the Invention (Means for Solving the Problems) In order to solve the above problems, the present invention provides a recording layer in which the irradiated portion changes phase between an equilibrium phase and a non-equilibrium phase by irradiating the substrate with light. An information recording medium having a general formula (InxSbyTeZ) 100-a M, (
However, x, y, z, a are atomic %, x+y+z=100
and 25≦x≦55.27<y≦55.20≦, respectively.
Within the range of 2≦50.0 and α≦20, M is Se, A
s, P, SGe, St, B, C, N, and Ar) I will provide a.

(Function) In the In-8b-Te system, InxSbyTez (
However, x + y + z - 100, X, r, z are atomic %),
25≦×≦55゜27<y≦55.20, respectively
Since the In-8b-Te alloy having a composition in the range of ≦2≦50 has the advantage of not becoming amorphous, the above-mentioned alloy with the above composition in which M is added to this composition or a composition in the vicinity of this composition is , is a material that satisfies the conditions as a recording layer of a phase change type information recording medium as described above. Further, when the element represented by M is contained in a range lower than 20 at %, the melting point is lowered, and thus the recording sensitivity is improved. Further, since the crystallization speed is relatively high, initialization and erasing can be performed at high speed.

Furthermore, the presence of the M element makes it easier to become amorphous, thereby making it possible to stabilize the amorphous state. Furthermore, the recording layer with this composition not only easily becomes amorphous but also has a relatively high crystallization speed, so that initialization, recording, and erasing can be performed at high speed.

(Example) Hereinafter, the present invention will be specifically described with reference to the accompanying drawings. FIG. 1 is a sectional view showing an information recording medium according to an embodiment of the invention. Substrate 1 is polyol/fin,
It is made of a material commonly used in this technical field, such as epoxy, plastic such as polycarbonate (PC), polymethyl methacrylate (PMMA), or glass. A protective layer 3, a recording layer 2, a protective layer 4, and a protective layer 5 are formed above this substrate 1 in this order.

The protective layer 3 and the protective layer 4 are disposed to sandwich the recording layer 2 and are made of an organic polymer material, such as a thermoplastic resin such as polymethyl methacrylate or polystyrene, or an ultraviolet curing resin (so-called 2P resin), or 5i02 ,A
l□03, AIN.

It is formed of a dielectric material such as ZnSS or ZrO2. These protective layers 3.4 have the function of preventing the recording layer 2 from being affected by moisture in the air, and prevent the irradiated portion of the recording layer 2 from scattering or forming holes due to light such as a laser beam during recording and erasing. It has the effect of preventing the formation of. These protective layers 3.4 can be suitably formed by a spin coding method, a vapor deposition method, a sputtering method, or the like.

Note that the thickness of these protective layers 3.4 is preferably 10 angstroms to several tens of micrometers.

The protective layer 5 is provided to prevent scratches, dust, etc. on the surface when handling the information recording medium, and is coated with an ultraviolet curing resin using a spin code method or the like, and then irradiated with ultraviolet rays. It is formed by curing. The thickness of this protective layer 5 is preferably 100 angstroms to several tens of micrometers. In addition, protective layer 3
．． 4.5 is preferably provided, but does not necessarily have to be provided.

Recording layer 2 is (InxSbyTez)100-# Ma=
(However, X, Y+Zs α is atomic %, x+y+z−1
00, respectively 25≦x≦55.27<y55.20
≦2≦50.0 and α≦20, M is Se,
As, P, S, Ge, Si, B.

At least one selected from the group consisting of C, N and Ar
It is made of an alloy with a composition represented by Here, it is desirable that the recording layer 2 has a signal reproduction value (C/N) of 45 dB or more at a practical level, and such a signal reproduction value (C/N) is determined by the reflectance of the recording layer 2. Obtained when the change is 4% or more. Reflectance change is 4%
In this case, the composition range of Inx5byTez is 25 at% or more and 55 at% or less [(Sb
7oTe3o) When In is changed in the state of Inx. X is atomic percent. ], and Sb is more than 27 at% 5
5 atomic % or less [(InsoTes.) in the state of sby,
When changing Sb. y is atomic percent. ], and Te is 20 at% or more and 5o at% or less [(I n5osb, o
) When Te is changed in the state of Te z. 2 is atomic percent. ].

That is, if the recording layer 2 is composed of In, Sb, and Te within these composition ranges, a signal reproduction value (C/N) at a practical level can be obtained.

The composition of In, Sb and Te is Inx5byTez, 25≦x≦55.27<y≦55 and 20≦2≦5
0 (However, x+y+z=100.x.

y and 2 are atomic percent. ). In this region, the crystallization temperature of the recording layer 2 is about 240 degrees.

The temperature is higher than room temperature. When the crystallization temperature of the recording layer 2 is high, the amorphous state becomes stable.

In addition, since the activation energy for crystallization generally tends to be high, the crystallization speed is also high, making it suitable for high-speed erasing. It can be formed suitably. still,
When performing vapor deposition or sputtering using an alloy target, it is necessary to take into account that there is a difference between the target composition and the composition of the layer actually formed. Further, the layer can also be formed by simultaneous vapor deposition of multiple elements, simultaneous sputtering of multiple elements, or the like. The thickness of the recording layer 2 is preferably 100 to 3000 angstroms.

The recording layer 2 is polished (InxSbyTez). . −
In.

Since sb and Te have a composition that easily becomes amorphous, the stability of the amorphous state as a non-equilibrium phase is excellent. In addition, since crystallization speed is high and it is easy to become amorphous, initialization, recording, and erasing speeds are high. Furthermore, the recording sensitivity is high because the melting point is lowered by the presence of the M element.

Next, an example of a method for forming the recording layer of the information recording medium according to this embodiment will be described with reference to FIGS. 2 and 3. FIG. 2 is a longitudinal cross-sectional view showing a schematic configuration of a sputtering apparatus used to form the recording layer of this embodiment, and FIG. 3 is a cross-sectional view thereof. In the figure, a vacuum vessel 10 is shown in the center, and this vacuum vessel 10 has a gas introduction port 11 and a gas discharge port 12 on its bottom surface.

This gas exhaust port 12 is connected to an exhaust device 13, and the inside of the vacuum container 10 is evacuated by this exhaust device 13 via the exhaust port 12. Also, gas introduction port 1
1 is connected to an argon gas cylinder 14 , and argon gas as a sputtering gas is introduced from the cylinder 14 into the vacuum container 10 through a gas introduction port 11 . In the upper part of the vacuum container 10, a disk-shaped rotary base 15 for supporting a substrate is arranged with its surface horizontal, and the substrate 1 is supported on its lower surface. In addition, near the bottom of the vacuum container 10, a base] 5
Sputtering sources 21, 22, 23 each made of a predetermined element constituting the recording layer 2 are arranged so as to face each other, and a high frequency power source (not shown) is connected to each sputtering source 21, 22, 23. ing. Monitor devices 24, 25, 26 are provided above these sputtering sources 21, 22, 23, respectively.
The amount of sputtering from 22.23 is monitored, and each sputtering source 21.2 is adjusted so that the recording layer has a predetermined composition.
2.23 The amount of electricity input is adjusted.

In such a sputtering apparatus, first, the inside of the vacuum device 10 is evacuated to 10-6 Torr by the exhaust device 13. Next, while introducing argon gas into the vacuum device 10 through the gas introduction port 11, the exhaust device 13 is introduced.
The inside of the vacuum container 10 is maintained at a predetermined pressure in an argon gas atmosphere by adjusting the exhaust amount. In this state, while rotating the substrate 1, a predetermined power is applied to the suba 1 swaying sources 21, 22, and 23 for a predetermined period of time. As a result, a recording layer having a predetermined composition is formed on the substrate 1. When forming the protective layer, prior to forming the recording layer 2, the sputtering source 21, 22, 23 adjusted to the composition of the protective layer is used to sputter the substrate 1 as described above. The protective layer 4 can be formed on the recording layer 2 under the same conditions as when the protective layer 3 is formed first, then the recording layer 2 is formed, and then the protective layer 3 is formed.

Note that when the additive element M is N2 or Ar, it is added using sputtering gas. That is, when adding N2, sputtering is performed in N2 gas or a mixed gas of N2 gas and Ar gas, and when adding Ar, conditions such as gas flow rate are adjusted to predetermined conditions at the Ar gas mountain. Setting and sputtering.

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

2 Initialization recording Jψ2 is usually amorphous immediately after layering, but it needs to be crystalline in order for information to be recorded, so the entire recording layer 2 is irradiated with light such as a laser beam and heated and slowly cooled. Then, the recording layer 2 is crystallized.

Recording of Information A recording layer 2 is irradiated with high-output light having a short pulse width, and the irradiated portion is heated and rapidly cooled to change its phase to an amorphous state, thereby forming a recording mark.

Erasing information A recording mark portion formed on the recording layer 2 is irradiated with light having a lower output and a longer pulse width than during recording to change the phase of the recording mark portion into a crystal, thereby erasing information.

Reproducing information A relatively weak light is irradiated onto the recording layer 2 on which information is recorded, and the information is read by detecting the difference in optical characteristics, such as reflectance, between the recorded mark portion and the non-recorded portion.

In addition, since the information recording medium according to the present invention has a high crystallization speed, overriding is possible.

Overriding refers to power-modulating light such as a 3-laser beam emitted from a single light source between two power levels PE (erasure) and Pw (recording), as shown in Figure 4. The method involves superimposing light at a recording power level on light at an erasing power level to overwrite new information while erasing already recorded information.

Next, test examples of the present invention will be explained.

Test Example 1 Inx5byTez alloy thin layers of various compositions were formed on a heat-resistant glass substrate using the sputtering apparatus shown in FIGS. 2 and 3, and the structures of these thin layers were confirmed by X-ray diffraction. The range indicated by diagonal lines in the ternary composition diagram in Figure 5, that is, 25≦x≦55.27<y≦55.20≦2
As a result of confirmation in the composition range of ≦50, all were amorphous immediately after layering. In this composition range, the crystallization temperature is 130° C. or higher, and an amorphous state exists stably at room temperature. Furthermore, it was confirmed that by selecting the laser beam irradiation conditions, it can be used as a phase-change type recording layer that can record and burn information.

Test Example 2 For Inx5byTez having the composition range of Test Example 1, S
e, As, P, S, Ge, Si, B, C.

Samples to which N, Ar, Bi, Pb, or Sn were added were prepared, and the crystallization temperature of each sample was measured. As a result, Se, As, P, and S.

The crystallization temperature increased in samples to which Ge, Si, B, C, N, or Ar were added, and decreased in the samples to which Bi, Pb, and Sn were added.

From this, Inx5byTez has Se, As, P,
It was confirmed that the amorphous state was stabilized by adding S, Ge, St, B, C, N, or Ar.

In addition, Se, As, and P are added to Inx5byTez.

As a result of measuring the melting point of samples to which S, Ge, Si, B, C, N, or Ar were added, In x S byT
The melting point was lower than that of ez. From this, it was found that the addition of these elements improves the recording sensitivity5.

Test Example 3 The sample prepared in Test Example 2 was irradiated with a laser beam from the substrate side while changing the irradiation conditions, and the crystallization rate was examined. Figure 6 shows 5, 10, 20, and 30 atomic% of Se, respectively.
The results for the added samples are shown below. FIG. 6 is a graph showing the relationship between these, with the horizontal axis representing the pulse width of the irradiated laser beam and the vertical axis representing the amount of change in reflectance. In this graph, changes in reflectance correspond to phase changes between amorphous and crystalline. Note that FIG. 6 shows a case where the power of the irradiated laser beam is 7 mW.

As shown in this figure, the crystallization rate is highest when no Se is added, and decreases as the amount of Sn added increases.
When the amount added was 30 atomic %, the crystallization rate was 1 μsec. This is due to the fact that the amorphous state was stabilized by the addition of Se.

In other words, a sufficient crystallization rate is maintained within a range where the amount of Se added is small. Considering the sharpness, the crystallization rate is 1.
Since it is desirable that the time is less than μsec, it is appropriate that the amount of Se6 added be less than 20 atomic %.

As, P, S, Ge, Si instead of Se.

Similar results were obtained when similar tests were conducted on samples formed with alloys containing B, C, N, or Ar, and the practical addition amount for these is 20 at.%.
The following was confirmed to be appropriate.

Furthermore, similar effects could be obtained even when some of these additive elements were added in combination. In this case, it was confirmed that when the total amount added exceeds 20 atomic %, the crystallization temperature decreases.

The above results indicate that it is possible to use (InxSbyTez)+oo-a Me gold alloy phase change type recording layer in the above range, and that such a recording layer can be changed to an amorphous state with the addition of M element. It was confirmed that the stability of the compound increased and the crystallization rate was as fast as 1 μsec or less.

In this embodiment, an example is shown in which a flat plate-like substrate is used, but the substrate is not limited to this, and various forms such as a tape-like shape or a drum-like shape can be used.

[Effects of the Invention] As explained above, according to the present invention, recording stability in an amorphous state which is a non-equilibrium phase is excellent, initialization, recording and erasing can be performed at high speed, and Since the melting point of the recording layer can be lowered, an information recording medium with high recording sensitivity can be obtained.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing an information recording medium according to an embodiment of the present invention, FIG. 2 is a vertical cross-sectional view showing a schematic configuration of an apparatus for forming a recording layer, and FIG. 3 is a cross-sectional view thereof. Figure 4 shows the power of the laser beam during override, and Figure 5 shows the power of the laser beam during override.
The figure shows I, which is the basic recording layer of the information recording medium according to the present invention.
A composition diagram showing the composition range of the n-5bTe ternary alloy, and FIG. 6 is a graph showing the relationship between the pulse width of the irradiating laser beam and the amount of change in reflectance.

Claims (1)

[Claims] An information recording medium comprising a substrate and a recording layer whose irradiated portion changes phase between an equilibrium phase and a non-equilibrium phase upon irradiation with light, the recording layer having the general formula (InxSbyTez)_
1_0_0_-_αM_α (where x, y, z, α are atomic %, x+y+z=100, each 25≦x≦5
5, 27<y≦55, 20≦z≦50, 0<α≦20, and M is Se, As, P, S, Ge, Si,
1. An information recording medium characterized in that it is formed of an alloy having a composition represented by: at least one element selected from the group consisting of B, C, N, and Ar.