JPH0482780A - Optical recording medium - Google Patents

Abstract

PURPOSE:To improve write, rewrite and retaining time properties of information by making a recording material consisting of [(GaSb)100-y(InSb)y]100-x(Vb2VIb3)x by using GaSb which has a short crystallization time and high amorphous stability, although some difficulty is involved in the ability to become amorphous, InSb which has a smaller optical band gap than GaSb and Vb2VIb3 which is easy to become amorphous and becomes crystallized at higher temperature than Te. CONSTITUTION:Vb2VIb3 of a recording material is composed of a group Vb element and a group VIb element of a periodic table. This chemical quantum theory compound and a bland of two different types or more of the former have a range from x and y set to 7mol%<=x<=85mol%, 5mol%<=y<=70mol%. A 100nm-thick SiO2 protecting layer 2, a 40nm-thick [(GaSb)30(InSb)70]15(Sb2Te3)85 recording layer, a 100nm-thick SiO2 protecting layer 4, a 100nm-thick Al alloy thermal diffusion layer 5, an adhesive layer 6 and a 1.2mm-thick acrylic protecting plate 7 are laminated on a 1.2mm-thick acrylic substrate 1.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention irradiates a recording material layer with a light beam such as a laser beam to change the optical properties of the irradiated area, and changes the optical properties. Use it to record and reproduce information, or to record and reproduce information.
It relates to rewritable optical recording media that perform playback and erasing, and in particular optical recording media that can write or rewrite information at high speed, retain this recorded information for a long period of time, and improve recording sensitivity. It is about improvement.

[Conventional technology]

2. Description of the Related Art Conventionally, magneto-optical recording media have been used as rewritable optical recording media on which information is recorded using a light beam such as a laser beam, and have been put into practical use in some cases. In other words, this method applies optical energy and a magnetic field to write information by reversing the magnetization direction of the recording material layer, while detecting the difference in Faraday rotation angle or Kerr rotation angle depending on the magnetization direction to obtain a reproduction signal. It is a method.

However, this method has been applied only to limited fields because there is no practical method for rewriting at least one sector.

On the other hand, as another rewritable optical recording medium, a so-called phase-change optical recording medium that utilizes a phase change between "crystalline and amorphous" is currently under research.

That is, in this method, as shown in FIG. 2, a part of the recording material layer (a) in a crystalline state (CR) is irradiated with a high-power laser beam, and the recording material layer (a) in that region is After melting, it is rapidly cooled to change it to an amorphous state (am), which usually corresponds to the recorded state.However, when erasing, as shown in Figure 3, a low-power laser beam is irradiated to the recorded area to melt it. After that, the crystalline state (
cr).

In this method, two light beams are used to
In addition to being able to rewrite within one sector (i.e., erasing the recorded information with the preceding beam and then recording with the next light beam), if a recording material with a short crystallization time is used, one sector can be rewritten. Since it is possible to override with a light beam (that is, to simultaneously rewrite information that is recorded or erased while selectively switching the beam output), it has the advantage of being applicable in various fields.

By the way, from the viewpoint of simplifying the optical system or improving the transfer speed, it is preferable that the recording material used in this phase change type optical recording medium has a short crystallization time.
In addition, from the viewpoint of retaining recorded information over a long period of time, it is preferable that the stability in the amorphous phase is high (usually evaluated by the crystallization temperature of the recording material), and the crystallization time is 100 ns or less. , preferably 50 ns or less, while the crystallization temperature was said to be at least 140° C. or higher.

As a material that satisfies these two requirements, [IEICE CPM87-88:1987] and JP-A-63-2
No. 25934 discloses a Ge-8b-Te ternary recording material. That is, although this ternary recording material has a short crystallization time (30 ns), the stability of the amorphous phase is insufficient (crystallization temperature: 100° C.).5
b2Tei and the stability of the amorphous phase are sufficient (
Crystallization temperature: 200°C) has a long crystallization time (100°C).
ns or more) GeTe, and was said to have intermediate properties between the above-mentioned 3b2Te+ and GeTe.

However, as mentioned above, this GeTe has the disadvantage that its crystallization time is long < (100 ns or more), and as the mixing ratio increases, the crystallization time of Ge-3b-Te also increases. Ge composition that ensures temperature
-3b-Te has a crystallization time of 50 ns or more, so although it is possible to put it into practical use, its characteristics are not sufficient.

On the other hand, as another recording material that satisfies the above two requirements, Ga-3b-T
A ternary recording material of e is mentioned.

That is, this Ga-3b-Te is [APPLIED
0PTICS: Vol, 26. No, 22:1
5/Nov, /' 87], the crystallization time is short < (20 ns) and the stability of the amorphous phase is high (crystallization temperature: 350'C), but GaSb has difficulty in becoming amorphous. In addition, Te, which easily becomes amorphous,
This is a recording material in which the amorphous state is improved by the addition of Ge-3b-Te, and, like the above-mentioned Ge-3b-Te, it is said to be a material that meets two requirements regarding crystallization time and stability of the amorphous phase.

[Problem to be solved by the invention]

By the way, in order to improve the amorphization of the GaSb, the Te is desirably 10at
It was necessary to add more than % (atomic %).

However, the proportion of Te in Ga-3b-Te is 10 at%
If the value exceeds the above, the crystallization time of the Ga-3b-Te becomes significantly longer (that is, the crystallization rate However, since the crystallization temperature of Te is as low as 10°C, as the proportion of Te increases, the crystallization temperature of Te increases.
There was a problem that the crystallization temperature of -3b-Te also decreased rapidly and the stability of its amorphous phase also deteriorated.

For this reason, like Ge-5b-Te, although it is possible to put it into practical use, its characteristics are still insufficient.

[Means to solve the problem]

The present invention has been made with attention to the above-mentioned problems, and the problem is to develop GaS, which has difficulty in becoming amorphous but has a short crystallization time and a high stability of the amorphous phase.
b, InSb, which has the same crystal structure as GaSb and has a smaller optical bandgap than GaSb, and Vb2vtb, which has a short crystallization time and can be easily made amorphous, and has a crystallization temperature higher than Te, and the above-mentioned recording material. An object of the present invention is to provide an optical recording medium in which information can be written or rewritten at high speed, the recorded information can be retained for a long period of time, and recording sensitivity can be improved.

That is, the present invention provides a recording material layer on a substrate that undergoes a reversible phase change by means of light, heat, etc., and uses the change in optical properties accompanying this phase change to record/reproduce information, or record/record/reproduce information. Assuming an optical recording medium that performs reproduction and erasing, the above recording material is [(GaSb)1oo-y(InSb)y]1oo-,
(Vb2VIbi).

(However, V b 2 VT, b h are Vb on the periodic table
It is composed of a group element and a group VIb element, and its chemical formula is Vb2.
v'xb, or a mixture of two or more of these stoichiometric compounds, and the range of x and y is 7molX≦X≦85molX, 5molX≦y≦70molX). It is characterized by being composed of the composition shown.

In such technical means, the above V b 2VT b
h includes Vb group elements such as As, Sb, and Bi;
5b2Tea, B, which is composed of VIb group elements such as S, Se, and Te, and whose chemical formula is expressed as Vb2VIbl.
i2Te5, Sb+Se+, Bi2Te5, Sb+S+
, B+2St, AS2Sel, and AstTe+.
Mixtures of two or more species, for example, stoichiometric compounds such as Bi25Te2, other solid solutions, and mixtures can be used.

On the other hand, it is synthesized with GaSb, InSb, and ■b2VIb, and has the general formula [(GaSb)! oo-y(InSb
)y]100-(Vb+VIb+)-, depending on the types of constituent elements of the above-mentioned Vb2'VIbl and the synthesis ratios of GaSb, InSb, and Vb, vhb, for example, stoichiometric compounds may be added. There are those that constitute a solid solution, those that constitute a solid solution, and those that constitute a mixture.

In addition, the synthesis ratio of the above Vb2VIb, that is, the general formula [(GaSb)too-, (InSb)y]1oo-,
(VbxVIbx), the applicable range of X is X≦7
In the case of molX, the improvement of amorphization in GaSb is insufficient, and the above material
nSb)yLoo-(VbzVIb+L becomes difficult to amorphize; on the other hand, in the case of X≧85molX,
[(GaSb)too-y(InSb)i100-, (
Vb+VIbs).

Because there is a risk that the crystallization rate of (
It is necessary to set it within the range of 7molX≦X≦85molX.

On the other hand, the synthesis ratio of the above (InSb), i.e. -mono %
The applicable range of the formula % y is that when y≦5 molX, the effect of InSb, which contributes to the improvement of recording sensitivity, is insufficient, and when y≧10 molX, [(GaSb)100-y(InSb) y]100--
Since there is a risk that the crystallization rate of (Vb+VIbs)- may slow down, it is necessary to set it within the range of (5 molX≦y≦70 molX).

Next, the basic structure of an optical recording medium to which the above-described recording material is applied is basically composed of a light-transmitting substrate and a recording material layer formed on this surface.

In addition, the purpose is to prevent the recording material layer from being deformed after melting and before it solidifies, or to prevent mechanical damage to the recording material layer.
It is also possible to provide a protective layer on the recording material layer for the purpose of preventing oxidation and the like.

In addition to glass, resin materials such as acrinope polycarbonate and epoxy can be used as the light-transmissive substrate. Here, if a resin material is used as the substrate,
To prevent thermal damage to the resin material, between the recording material layer and the substrate,
For example, a substrate protective layer made of SiO□, Zn5Zr02, or a mixture thereof may be provided. still,
In an optical recording medium in which recording, reproduction, and erasure are performed by irradiating a light beam from the opposite side of the substrate, the substrate may of course be made of a light-opaque material such as aluminum.

In addition, examples of the material constituting the protective layer include the same materials as those constituting the substrate protective layer, resin materials such as ultraviolet curing resin, acrylic, polycarbonate, and epoxy, and glass. . Further, the protective layer may be composed of a single layer of these materials, or may be composed of a plurality of laminated layers of the above materials. In addition, for the purpose of increasing the cooling rate, Au, AI
, a thermal diffusion layer made of a metal with high thermal conductivity such as Ag, or a thermal diffusion layer made of a metal with high thermal conductivity such as Ag,
, Ge, GaAs, BeO, AIN, TiC, C
A heat conduction control layer or the like made of a material whose thermal conductivity decreases as the temperature increases, such as FeXRh, Be, Ir, etc., may be provided.

Furthermore, as a method for forming the recording material layer, a sputtering method or a vacuum evaporation method can be used. In other words, the sputtering method described above includes simultaneous sputtering, in which a target composition is synthesized by using multiple targets and the amount of power applied to each target is appropriately adjusted, and the composition is deposited on a substrate at the same time. It is also possible to perform sputtering using one alloy target corresponding to the object. Further, as the above-mentioned vacuum evaporation method, a co-evaporation method can be used in which a target composition is obtained by using a plurality of evaporation sources and adjusting the respective evaporation rates, and simultaneously deposits the same on the substrate.

In the optical recording medium of this technical means, the amorphous phase of the recording material layer may correspond to the recorded state and the crystalline phase thereof may correspond to the erased state, as in the conventional case. The amorphous phase may correspond to the erased state and the crystalline phase may correspond to the recorded state (the selection is arbitrary).

[Effect]

According to the above-mentioned technical means, the recording material can be crystallized in a short period of time, although it is difficult to turn it into an amorphous state.
20 ns), and the stability of the amorphous phase is also high (crystallization temperature: 350°C).The crystal structure is the same as that of GaSb (zincblende structure), and the optical band gap is higher than that of GaSb (0.7 eV). Small InSb (
The following general formula, [(GaSb)too-y(lnsb), was synthesized using V b 2 VI bh, which has a short crystallization time (0.2 eV), is easy to become amorphous, and has a higher crystallization temperature than Te. y]1ao-,
(VblVIbl), it is possible to improve the amorphous state without causing a decrease in the crystallization rate or crystallization temperature, and to keep the amorphous phase in the recorded state. When it is made to correspond to the above, it becomes possible to improve the recording sensitivity.

Here, the above general formula, i.e., f(GaSb)lQa-r(InSb)r)100-f
Even when the composition ratio of VIb group elements such as Te in (VblVIbl)- exceeds 10 at%, the crystallization rate decreases and the crystallization temperature decreases compared to the means disclosed in JP-A-62-241145. The inventor of the present invention infers the reason why the decrease is difficult to occur as follows.

That is, regarding the "crystallization rate", I(GaSb)
1ao-y(JnSb)i100-, (VbpVIb,
) t is a synthesis between GaSb and InSb, which are stoichiometric compounds, and Vb, VIb, which are stoichiometric compounds, or GaSb and InSb, which are stoichiometric compounds, and V b, which is a stoichiometric compound. 2VI b h, and the above-mentioned Garb and InSb both have a zinc blende type structure and have the same crystal structure, and the crystallization rate of the above-mentioned GaSb and VblVIbl is We infer that this is because they are both fast.

On the other hand, "for the crystallization temperature j, [(GaSb)100-y(InSb)y]1oa-(
Vb2VIb+), which forms part of Vb2VIb+).
b! As mentioned above, the crystallization temperature of Te is higher than that of Te, and the crystal structures of GaSb and InSb are the same, so the addition of Vb2VIb and InSb has little effect on the crystallization temperature. I'm reasoning.

Also, [(GaSb)+co-y(InSb)y]10
0-x(Vb2VIEl+).

The reason why the recording sensitivity, that is, the amorphous sensitivity improves, is that the optical bandgap of InSb, which partially replaces GaSb, is 0.2 eV, which is significantly smaller than the value of GaSb (0.7 eV). Due to partial substitution, the above [(GaSb)100-y(InSb)yl! a
It is inferred that this is because the absorption rate of the light beam at o- and (Vb2VIba)- is increased.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

◎First Example As shown in Fig. 1, the optical recording medium according to this example consists of an acrylic substrate (1) with a thickness of 1.2 mm, and
1) A substrate protective layer (2) made of 5iOt with a thickness of 1100 nm formed by RF magnetron sputtering method on top.
On this substrate protective layer (2), a 40 nm thick [(G
aSb) go (InSb) + o] + i (S
A recording material layer (3) made of b2TeiLi and a layer having a thickness of 110 mm formed on this recording material layer (3) by a similar method.
A protective layer (4) made of 0n SiO3 and this protective layer (4)
A heat diffusion layer (5) made of A1 alloy with a thickness of 1100 nm was formed on top by the same method, and an adhesive layer (6) of ultraviolet curable resin was laminated on this heat diffusion layer (5). Thickness 1
．． The main part consists of a 2mm acrylic protection plate (7).

Note that light absorption in this optical recording medium ranges from visible light to near-infrared light, and at least 400 to 860 nm.
It could be used as an optical recording medium within this range.

When using this optical recording medium, the amorphous phase of the recording material corresponds to the recorded state, while the crystalline phase of the recording material corresponds to the erased state, as in the past.

The recording method using this optical recording medium will be described below. First, the optical recording medium was rotated at a speed of 1800 rpm and uniformly irradiated with a 780 nm semiconductor laser to initialize the optical recording medium.

Next, the initialized optical recording medium is rotated at a speed of 1800 rpm, and in this state, a single recording/erasing beam (output during recording, 7 mW, output during erasing: 3 mW) is selectively switched between its output. ) was irradiated to record and erase information by override.

On the other hand, the optical recording medium on which information has been written is rotated at a speed of 1800 rpm, and in this state, a laser beam with an output of 1 mW is irradiated onto the recording material layer (3), and this reflected beam is read by a light receiving element. The recorded information was played back.

In the recording method using this optical recording medium, the recording/erasing time is 50 ns or less, which significantly improves the recording/erasing speed compared to the method using conventional optical recording media. A practical value of 25 dB or more was also obtained.

On the other hand, while heating the recording material layer (3), its reflectance is monitored, and the temperature at which the reflectance starts to change rapidly is defined as the "crystallization temperature A" of the recording material layer (3) applied to this optical recording medium. The crystallization temperature was determined to be 140°C or higher, and the stability of the amorphous phase was also sufficient.

In addition, as mentioned above, the output of the recording/erasing beam is 7 mW during recording and 3 mW during erasing, and the following recording materials in which a part of GaSb is not replaced with InSb, namely (GaSb)s( When Sb2Tea)es is applied to the sales optical recording medium (in this case, the recording time is 12mW
It was confirmed that the recording sensitivity was improved compared to the previous one (which was 5 mW during erasing).

Furthermore, although the information rewriting test was carried out up to 104 times, segregation of the recording material did not occur and no major deterioration in the recording characteristics was observed.

◎Second Example The optical recording medium according to this example has the above-mentioned recording material layer (3)
[(G
aSb)no(InSb)to]1o(Sb2Tea)
io structure and a heat diffusion layer made of A1 alloy (5
) is not provided between the optical recording medium and the optical recording medium according to the first embodiment.

Then, the optical recording medium initialized in the same manner as in the first embodiment is
Rotate at a speed of 800 rpm, and in this state the output J
A single recording/erasing beam (9 mW output during recording, 5 mW output during erasing) is irradiated with a selectively switched recording/erasing beam to record and erase information through override, while the written optical recording medium is was rotated at a speed of 180 rpm, and in this state, a laser beam with an output of 1+nW was irradiated onto the recording material layer (3), and the reflected beam was read by a light receiving element to reproduce the recorded information.

As a result, even in the recording method using the optical recording medium according to the second embodiment, the recording/erasing time is 50 ns or less, the recording/erasing speed is significantly improved, and the erasing rate is also 25 dB or more, making it practical. A value was obtained.

In addition, as mentioned above, the output of the recording/erasing beam is 9 mW during recording and 5 mW during erasing, and the following recording materials in which a part of GaSb is not replaced with 1 nsb, namely (GaSb)io(Sb2Te+ In the case of an optical recording medium to which
, and 7 mW during erasing. However, this optical recording medium is A
It was confirmed that the recording sensitivity was improved compared to that of the previous example (which is equipped with a heat diffusion layer made of U).

Furthermore, when the crystallization temperature of this recording material was determined, it was found to be 16
The stability of the amorphous phase was sufficient at temperatures above 0°C, and even though information rewriting tests were performed up to 20 times, segregation of the recording material did not occur and no major deterioration in recording characteristics was observed.

◎Third Example The optical recording medium according to this example has the above-mentioned recording material layer (3).
[(G
aSb)*1(InSb)t]as(SbzTe+)i
The difference between the optical recording medium and the optical recording medium according to the first embodiment is the same as that of the first embodiment, except that the optical recording medium is constructed of the same structure as above, and the heat diffusion layer (5) made of A1 alloy is not provided.

Then, the optical recording medium initialized in the same manner as in the first embodiment is
It is rotated at a speed of 800 rpm, and in this state, a single recording/erasing beam whose output is selectively switched (output of 11 mW during recording, output of 5 mW during erasing) is irradiated to record information by override.・While erasing, the written optical recording medium is rotated at a speed of 1800 rpm,
In this state, the recording material layer (3) was irradiated with a laser beam with an output of 1 mW, and the reflected beam was read by a light receiving element to reproduce the recorded information.

As a result, even in the recording method using the optical recording medium according to the third embodiment, the recording/erasing time is 50 ns or less, the recording/erasing speed is significantly improved, and the erasing rate is also 25 dB or more, making it practical. A value was obtained.

Further, as mentioned above, the output of the recording/erasing beam is 11 mW during recording and 5 mW during erasing, and the following recording materials in which a part of GaSb is not replaced with InSb, namely (GaSb)9o(Sb+Te+ ) to is applied (in this case, the recording time is 18 m
W, when erasing was 10 mW. However, it was confirmed that this optical recording medium has improved recording sensitivity compared to the optical recording medium (which has a heat diffusion layer made of Au).

Furthermore, when the crystallization temperature of this recording material was determined, it was found to be 20
The stability of its amorphous phase is sufficient at temperatures above 0°C,
In addition, although an information rewriting test was performed up to 10'' times, segregation of the recording material did not occur, and no major deterioration in recording characteristics was observed.

◎Fourth Example The optical recording medium according to this example has the above-mentioned recording material layer (3).
[(G
aSb)ao(InSb)tolsa(Bi+Te+)
So and the heat diffusion layer made of A1 alloy (5
) is not provided between the optical recording medium and the optical recording medium according to the first embodiment.

Then, the optical recording medium initialized in the same manner as in the first embodiment is
It is rotated at a speed of 800 rpm, and in this state, a single recording/erasing beam (output of 9 mW during recording, output of 5 mW during erasing) whose output is selectively switched is irradiated to record and erase information by override. While erasing, the written optical recording medium is rotated at a speed of 1800 rpm, and in this state a laser beam with an output of 1 mW is applied to the recording material layer (3
), and this reflected beam was read by a light receiving element to reproduce the recorded information.

As a result, even in the recording method using the optical recording medium according to the fourth embodiment, the recording/erasing time is 50 ns or less, the recording/erasing speed can be significantly improved, and the erasing rate is also 25 dB or more, which is practical. A value was obtained.

In addition, as mentioned above, the output of the recording/erasing beam is 9 mW during recording and 5 mW during erasing. In the case of an optical recording medium to which Bj2Tes)so is applied (in this case, the recording time is 15 m
W: 7 mW during erasing. However, it was confirmed that this optical recording medium has improved recording sensitivity compared to the optical recording medium (which has a heat diffusion layer made of Au).

Furthermore, when the crystallization temperature of this recording material was determined, it was found to be 16
The stability of its amorphous phase is sufficient at temperatures above 0°C,
In addition, although an information rewriting test was performed up to 105 times, segregation of the recording material did not occur and no major deterioration in recording characteristics was observed.

〔Effect of the invention〕

According to the present invention, the recording material is made of GaSb, which has difficulty in becoming amorphous but has a short crystallization time and high stability of the amorphous phase, and InSb, which has the same crystal structure as GaSb and has a smaller optical band gap than GaSb. and V b r VI b + , which has a short crystallization time, is easy to become amorphous, and has a higher crystallization temperature than Te.
'2VIb +) Become.

Therefore, information can be written or rewritten at high speed, and this recorded information can be retained for a long period of time.

Furthermore, as the recording sensitivity is improved, the output of the light beam during writing can be reduced, which has the effect of reducing the thermal stress applied to the optical recording medium and improving its durability against repeated rewriting.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the structure of an optical recording medium according to an example;
Figures 2 and 3 are explanatory diagrams of the principle of recording and erasing in phase change method 1. [Explanation of symbols] (z)...Substrate (3)...Recording material layer Patent Applicant: Fuji Representative of Xerox Corporation
Person Patent attorney Tomohiro Nakamura (2 others) Recording material layer

Claims (1)

[Claims] A recording material layer that undergoes a reversible phase change by means of light, heat, etc. is provided on a substrate, and a change in optical properties accompanying this phase change is used to record, reproduce, or record information. - In an optical recording medium that performs reproduction and erasing, the recording material is [(GaSb)_1_0_0_-_y(InSb)_y
]_1_0_0_-_x(Vb_2VIb_3)_x (However, Vb_2VIb_3 is a stoichiometric compound composed of a Vb group element and a VIb group element on the periodic table and whose chemical formula is expressed as Vb_2VIb_3, or two or more of these stoichiometric compounds and the range of x and y is 7 mol%
≦x≦85 mol%, 5 mol%≦y≦70 mol%.