JPS63234421A - Information recording medium - Google Patents

Abstract

PURPOSE:To obtain the titled recording medium which has high stability of recording and recording level and with which defective initialization and incomplete erasing hardly arise by using amorphous silicon to form parts of 1st and 2nd protective layers adjacent to a recording layer and using a specific alloy to form the recording layer. CONSTITUTION:This recording medium has the recording layer 13 which is recorded with and erased of information by a phase change taking place when irradiated with a light beam and the 1st and 2nd protective layers 12, 14. The parts of the 1st and 2nd protective layers 12, 14 adjacent to the recording layer 13 are formed of the amorphous silicon. The recording layer 13 is formed of the alloy having the compsn. expressed by the formula In50-xMxSb50 (0<x<20 atom.%). In the formula, M is either one element selected from Te and Se. This alloy separates to In50-xSb50-x and SbxTex or SbxSex which exist in the state of being dispersed in the alloy when the light beam is projected on the recording layer. The stability of recording is high, since this SbxTex or SbxSex is stable in the amorphous state. A phase change takes place between the crystalline phase and the amorphous phase when the light beam is projected on the recording layer and, therefore, the high recording level is obtainable.

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) Phase change type optical discs have been known as optical discs from which information can be erased. In this phase change type optical disk, information is recorded and erased by utilizing the reversible phase change of the recording layer between, for example, crystalline and amorphous states by irradiating the recording layer with a laser beam. .

Examples of such phase-changing materials include Te, G
e, TeGe, InSe, 5bSe.

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 tow refractive index expressed by -Lk is different, these two states are reversibly changed by heat treatment with a laser beam to record and erase information (S, R, 0vshins
ky Metallurglcal T ransac
Llons 2 8411971) o In the case of this technology, the recording level is high because the reflectance is significantly different between the crystalline phase and the amorphous phase.

On the other hand, unlike the above-mentioned methods, there is also a technique for recording and erasing information by reversibly changing the phase between different crystals by laser beam irradiation. In-5b alloy is known as a material that undergoes such a phase change.

In the In-3b alloy thin film, fine crystal portions grow into relatively large crystals in a short time by irradiation with a laser beam having a relatively large pulse width. These two crystal structures have different bifurcated refractive indexes, and when reproducing by irradiating with a laser beam, the crystal states are distinguished, for example, by the difference in the amount of reflected light.

This technique has the advantage of high stability of the recorded portion.

In the above-mentioned optical disc, a protective layer is usually formed above and below the recording layer, and this protective layer prevents the portion irradiated with the laser beam from being heated and evaporated, thereby preventing holes from being formed in the recording layer. In addition, in the case of optical discs that record and erase information through a phase change between different crystalline phases, this protective layer heats the laser beam irradiated portion of the recording layer to gradually cool it, and It has the ability to facilitate crystallization and phase change. Such a protective layer is generally 5
i02 is used.

(Problem to be solved by the invention) However, in the case of technology that records and erases information by changing the phase between crystalline and amorphous, the stability is low because the recording portion is mainly amorphous. If the crystallization temperature of the material is low, the amorphous recording bits will gradually crystallize, making it difficult to distinguish between recorded and non-recorded parts. In addition, in the case of an optical disk in which the recording layer is formed of In-5b and the phase changes between different crystals, the recording layer is formed with a composition close to the stable In50Sb50 intermetallic compound. In some cases, there is a problem that the recording level is low. Therefore, when forming a recording layer with such a composition, there is a possibility that information recording may become insufficient.

On the other hand, attempts have been made to form a recording layer using this In-8b alloy with a composition in which sb is slightly excessive. In this case, the laser beam irradiation creates a mixed phase of In5qSb5g crystal grains and sb crystal grains, and the size of the sb crystal grains changes depending on the laser beam irradiation conditions, so it is possible to obtain a certain recording level. The recording level is still not sufficient, and since this sb has a slow crystallization speed, the speed of initialization and erasing is low, and there is a great possibility that initialization failure and unerased data will occur.

In particular, the number of revolutions of the optical disc is, for example, 900 to 1.
At a high speed of 100 rp, the heat retention ability of the S i 02 protective layer becomes insufficient, the cooling rate of the laser beam irradiated area cannot be optimized, and initial crystallization and phase change become difficult to occur. For example, when the rotational speed of an optical disk increases from 900 to 11,000 rpm, even a laser beam with a high output of 10 mW can cut the same track portion from 6 to 8 times.
If it is not irradiated multiple times, it will not be initialized, and the risk of poor initialization will become even greater. Similarly, when erasing information, as the rotational speed of the disk increases, information cannot be completely erased even if the same area is irradiated with a high-power laser beam two or three times, making it even more likely that unerased information will remain. It ends up.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an information recording medium that has high recording stability and high recording level, and is less likely to cause initialization failures and unerased data.

[Structure of the invention] (Means for solving the problem) An information recording medium according to the first invention of this application includes a substrate,
A recording layer in which information is recorded and erased through a phase change when irradiated with a light beam, a first protective layer formed between the substrate and the recording layer, and a second protective layer formed on the recording layer. an information recording medium having a protective layer, wherein at least a portion of the first and second protective layers adjacent to the recording layer is formed of amorphous silicon, and the recording layer has a general formula: M X S b so (0< x <
20 atomic%)0-x, where M is Te
and Se.

Further, the information recording medium according to the second invention of this application includes a substrate, a recording layer on which information is recorded and erased by a phase change when irradiated with a light beam, and a layer formed between the substrate and the recording layer. and a second protective layer formed on the recording layer, wherein at least a portion of the first protective layer adjacent to the recording layer is amorphous. The recording layer is made of silicon, the second protective layer is made of an organic resin, and the recording layer has the following formula:
n M x S b so (0< x < 20
It is formed of an alloy having a composition expressed as 0-x (atomic %), and is characterized in that M is one element selected from Te and Se.

(Function) In the present invention, the recording layer is formed with the above-mentioned composition, and the portions of the first and second protective layers sandwiching the recording layer are both formed of amorphous silicon, or amorphous silicon and an organic resin, respectively. Then, by irradiating the recording layer with a light beam, the alloy with the above composition is converted into In
Sb and 50-x 5O-x Sb) (Te) (or 5b) (Se) (separated into 5
bxTeX or 5bxSex is stable crystalline In
It exists in a dispersed state in Sb.

50-x 50-x This 5bxTex or 5b) (Sex is stable in an amorphous state, so the recording stability is high. Also, 5b) (Tex or 5bXTe) (produced by phase separation) is a light beam. Because the phase changes between a crystalline phase and an amorphous phase by irradiation with 5b, a high recording level can be obtained.
XTex or 5bxSe>( has a high phase change speed, so initialization and erasure can be accelerated, and amorphous silicon and organic resin have a thermal diffusivity of 5i02
Since it is significantly smaller than , crystallization and phase change can be facilitated. Therefore, initialization failures and unerased data can be almost completely prevented.

(Example) Examples of the present invention will be specifically described below.

When the recording layer is formed with xnsOsb50, In5
Since o Sb5 o is an intermetallic compound, it is highly stable, and since the ordering (regularization) of atoms at short distances by laser beam irradiation is extremely fast, crystallization during initialization and erasure is extremely fast. However, in this tn50sb50, even if the laser beam irradiation conditions are changed, the amount of change in crystal grain size is small, and the recording level is low.

In addition, in the case of an alloy with a composition that has a slightly higher amount of Sb than rnsOsb50, In50 S
b5 It becomes a mixed phase of G crystal grains and SB crystal grains, and the size of the SB crystal grains changes depending on the laser beam irradiation conditions, so it is possible to obtain a certain recording level, but the recording level is still not sufficient. , and the crystallization rate is also low. On the other hand, In5°Sbs. In the case where the recording layer is formed of an alloy having a composition slightly higher in InQ than the above, the recording level is extremely low because the change in the size of In crystal grains depending on the laser beam irradiation conditions is small. On the other hand, the recording layer is formed of an alloy having a composition represented by the general formula I n, , M X S b, , M is an element selected from Se and Te, and The recording level can be increased by making the amount smaller than 20 atomic %.

In other words, the above composition can be changed to I n by irradiation with a light beam.
re-x S bsp-x and 5bXSe) (or 5b
xTe) (phase separation into 5b) (Se)
(And since S b X T e X changes phase between crystalline and amorphous depending on the laser beam irradiation conditions, a high recording level can be obtained due to the difference in reflectance of these phases. This 5b) (Te) (and 5bXSeX
Since the phase change speed is high, initialization and erasure can be performed at high speed.

On the other hand, the recording layer is sandwiched between first and second protective layers, and the portions adjacent to these recording layers are both formed of amorphous silicon (hereinafter referred to as a-Si), or a-5i and a-5i are respectively formed. Formed from organic resin. It has been found that this significantly improves the effect of insulating the recording layer, improving not only the initial crystallization and erasing characteristics, but also the recording characteristics. For example, the thermal diffusivity of 5i02 is 0.014 cm2/sec, whereas that of a-8t formed by sputtering is 0.0050 m2 (!
: Extremely small. In addition, in the case of organic resin, the thermal diffusivity is even smaller, about 0.002 cs2/sec. Therefore, the protective layer has a great effect of insulating the recording layer, and the phase change of the portion of the recording layer irradiated with the laser beam can be accelerated. Note that the first protective layer formed on the substrate side of the recording layer becomes high in temperature due to laser beam irradiation, so if the portion adjacent to the recording layer is made of mechanical resin, there is a risk that it will melt.

Furthermore, S b X T e X and 5b)(Se)( are stable even in the amorphous state,
e) (and 5bXSeX is extremely stable In50Sb5
Since it exists in a dispersed state between o crystals, recording stability is high.

In this case, if X becomes 20 atomic % or more, other crystals will appear due to irradiation with the light beam, so X is specified to be less than 20%.

The information recording medium according to this embodiment is configured as shown in FIG. 1, for example. The substrate 11 is made of a material that is transparent and has little change over time, such as glass or polycarbonate resin. A protective layer 12, a recording layer 13, and a protective layer 14 are formed on the substrate 11 in this order. The protective layer 12 is made of a-St, and protects the recording layer 13 from melting.
The recording layer 13 is insulated to suppress heat release from the recording layer 13. The protective layer 14 is composed of a main layer 15 made of a-Si and an auxiliary layer 16 made of ultraviolet curing resin. is formed. The main layer 15 has the same function as the protective layer 12, and the auxiliary layer 16 has the function of preventing scratches from occurring on the surface of the disc during handling. As shown in FIG. 2, a protective layer 17 made of ultraviolet curing resin is formed directly on the recording layer 13, and this protective layer 17 prevents scratches on the disk surface and protects the recording layer 13 from occurring. Heat insulation is suppressed from releasing heat from the recording layer 13.

Such an optical disc is manufactured as follows. First, the substrate 11 is placed in a sputtering device, and sputtered using an a-Si target in an argon atmosphere.
A protective layer 12 made of a-8i is formed. Next, while maintaining the same atmosphere, InTe)(Sb50 or I n,,-
A recording layer 13 made of xS e xS0-x Sbs is formed. Then re & a
A main layer 15 made of a-Si is formed by sputtering with a -Si target, and then the substrate is removed from the sputtering device and an ultraviolet curing resin is applied onto the main layer 15 by a spin code method. The auxiliary layer 16 is formed by irradiating with. When forming the protective layer 17, after forming the recording layer 13, the substrate is removed from the sputtering apparatus, an ultraviolet curing resin is applied onto the recording layer 13 by a spin code method, and this is irradiated with ultraviolet rays. Auxiliary layer 16 is formed.

Next, the operation of such an optical disc will be explained.

Since the initialization recording layer 13 is amorphous immediately after being formed, the recording layer 13 is continuously irradiated with a laser beam having a relatively weak output and a long pulse width to melt and slowly cool the recording layer 13 and solidify it. let me,
The phase is changed to a crystal phase formed by fine grains of 50-x 50-x quality of InSb and fine crystal grains of 5bxTe) (or 5b)(Sex).

5b)(Te)(
Or 5b) Change the phase of fine crystals of (Se) to amorphous to form fine crystal grains of InSb 50-X
50-X and 5b) (Te) (or Sb) (SexM) (Sb3 (
The recording pits 19 are formed in a mixed phase with an amorphous substance.

Irradiating the reproduction recording layer 13 with a relatively weak output laser beam,
Information is read by detecting the intensity of reflected light from the recording pits.

The recording pits 19 are irradiated with the erasing laser beam under basically the same conditions as those for initialization. The recording pits 19 are melted and slowly cooled to solidify as in the case of initialization.
5bxT4 among them! X or 5b) (SexM) (5b
)('s amorphous state becomes microcrystalline, and information is erased.

Next, a test example in which the information recording medium according to this example was manufactured and its characteristics were tested will be described.

Test Example 1 1200 A-8i layers were deposited on a polycarbonate substrate with groups by argon sputtering, and then
On top of that, 850 people formed a film of In35Te15Sb5o ternary alloy by simultaneous sputtering of three elements while strictly controlling the composition, and on top of this recording layer, a-3
The i-layer was deposited by 1200 people. Thereafter, a 10 μm ultraviolet curable resin layer was formed on this a-Si layer to produce an optical disc (this will be referred to as sample A). Next, by using the same layer structure and manufacturing method, the composition of the recording layer was changed to I
n45 Te5 Sb5 o s"40TelOSt)
SOS In47Te3Sb50 and In30T
Optical disk samples of e20 Sb5 D (referred to as samples B, C, D, and E, respectively) were created, and a recording layer was formed of In35Te15Sb5o, and sample A
A sample was created with the a-8i layer of the 5i02 layer (
Sample F). The characteristics of these samples A to F were evaluated using a dynamic characteristic evaluation device. For these samples, the wavelength was 83° when the disk rotation speed was 90 Orpm.
A 0 nm semiconductor laser is used, and during initialization, continuous light is irradiated with an output of 8 mW, and during recording, the output is 11 mW.
mW, pulse width 150ns, duty ratio 50%
A pulsed laser beam was irradiated, and during erasing, continuous irradiation was performed with the same output as for initialization. In addition, for sample A and sample F, the rotation speed was set to 200.400°900.
and 120 Orpm.

As a result, first, upon initialization, samples A to E could be initialized by two laser beam irradiations at 900 rpm. Regarding the recording in this case, the results shown in FIG. 2 were obtained. In Figure 2, the horizontal axis shows In
Te) (Take the value of X of Sb500-x, take the magnitude of the reproduction signal on the vertical axis, and calculate the difference between It is a graph diagram showing the relationship.According to this, in the case of In5g5b5o, the reproduced signal is extremely low, but it can be seen that the reproduced signal increases as X increases.Furthermore, when X increases from 15 atomic %, It can be seen that the playback signal level decreases.X
Although no tests have been conducted on the case where the ratio is greater than 20 atomic %, in this case, other crystal phases appear and the signal level decreases significantly. When erasing, the reproduced signal could be reduced to 0 by irradiating the recording pit with a single laser beam pulse when X was up to 15 atomic %, but when X was 20 atomic %, the reproduced signal was 40 mV. After confirming that the erased portion remains, the results of comparing sample A and sample F will be explained with reference to Table 1.

In the table, the number of initializations indicates the number of rotations of the disk required to crystallize one track during initialization, and the reproduction signal of the recording mark indicates the DC component during reproduction of the recorded part. shows the amplitude of the AC signal with respect to Also,
"Remaining erased" indicates the remaining amount of the AC signal after one laser beam irradiation. As shown in this table, compared to sample F, sample A has a significantly reduced number of laser beam irradiations during initialization, especially when the disk is rotated at high speed, and there are extremely few erased residues. . In addition, in terms of recording characteristics, sample A exhibits a smaller amount of decrease in the reproduced signal even with an increase in rotational speed than sample F, and can be expected to have a sufficient C/N ratio for practical use.

Test Example 2 An optical disk sample having the same layer structure as Test Example 1 was prepared by forming the recording layer of In 5exSbso and varying X within 0-xO<x≦20 atomic %.

As a result of evaluating the properties using the dynamic property evaluation apparatus in the same manner as in Test Example 1, the same properties as in the case of In Tex0-x Sb5o in Test Example 1 were able to be obtained.

Test Example 3 In this test example, a
-A sample in which the 8t layer was omitted, an ultraviolet curable resin was formed directly on the recording layer, and the thickness of the other layers was the same as in Test Example 1 was tested in the same manner as in Test Example 1, and the result was almost the same. I was able to get good results.

[Effect of the invention] According to this invention, 5b) (Te) (or 5bxSe
)( is stable in an amorphous state and exists in a dispersed state in stable crystalline In5oSb5o, resulting in high recording stability. In addition, 5b)(Te) (or 5bxSe) in the recording layer ) (changes in phase between a crystalline phase and an amorphous phase depending on the irradiation conditions of the light beam, so the recording level can be increased and information can be recorded reliably.

Furthermore, 5bxTe) (or 5b)(Se) (has a fast phase change, and can be thermally insulated with a-Si or organic resin protective layer to ensure phase change, speeding up initialization and erasure. This makes it possible to suppress initialization failures and unerased data.

[Brief explanation of the drawing]

FIGS. 1 and 2 are cross-sectional views showing an information recording medium according to an embodiment of the present invention, and FIG. 3 is a graph showing the relationship between X and the magnitude of a reproduced signal.

Claims (3)

[Claims] (1) A substrate, a recording layer on which information is recorded and erased through a phase change when irradiated with a light beam, a first protective layer formed between the substrate and the recording layer, and a top layer on the recording layer. In the information recording medium, the first and second protective layers have at least a portion adjacent to the recording layer made of amorphous silicon, and the recording layer includes: General formula In_5_0_-_xM_xSb_
5_0 (0<x<20 atomic %), wherein M is one element selected from Te and Se. (2) The second protective layer has an amorphous main layer adjacent to the recording layer, and an organic resin auxiliary layer formed on the main layer. The information recording medium according to scope 1. (3) a substrate, a recording layer in which information is recorded and erased through a phase change when irradiated with a light beam, a first protective layer formed between the substrate and the recording layer, and a first protective layer formed on the recording layer; In the information recording medium, the first protective layer has at least a portion adjacent to the recording layer made of amorphous silicon, and the second protective layer is made of an organic material. The recording layer has a general formula In_5_0_-_xM_xSb_5_0 (0<x
<20 atomic %), wherein M is one element selected from Te and Se.