JPH01162247A - Rewriting type phase transfer optical recording medium - Google Patents

Abstract

PURPOSE:To obtain a rewriting type phase transfer optical recording medium which has the excellent repeatability of recording and erasing and stability with age, is high in erasing speed, allows easy recording and has an excellent recording sensitivity by specifying the atom. number ratios of In and Te of the optical recording medium having the optical recording layer consisting of the alloy film which is composed of the In and Te. CONSTITUTION:The optical recording medium which is provided with the optical recording medium 1 consisting of the alloy film composed of the Ga and Te on a glass substrate 1 and has the atom. number ratio of the Ga and Te between 2:1 and 1:1 or between 2:3 and 1:3 can be lowered in m.p. and, therefore, allows easy recording and has the excellent recording sensitivity; in addition, said medium has the excellent repeatability of recording and erasing and the stability with age. The erasing speed is additionally increased by adding at least one among Ge, Sb, Sn, As, Se, Au, Pb, Ti, Pt, and Pb thereto.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a rewritable phase change optical recording medium that records information by irradiating a laser beam and causing an optical change in the irradiated area. .

(Prior art and problems to be solved by the invention) Recently,
Optical recording, in which information is recorded and erased by irradiating a thin film-like medium on a substrate with focused laser light to create holes in the thin film or structural changes such as amorphous-crystal transition, is a high-density, large-capacity recording method. It is attracting attention as a new technology that makes it possible. The material of the thin film medium used for these recordings is usually chalcogen such as Te or Se, or Bl+Sn.
A multi-component material including metals such as , pb, and sb, and semiconductors such as Go is used.

Furthermore, among the above-mentioned technologies, optical recording based on structural changes such as amorphous-crystalline transitions is capable of recording and erasing information many times in principle, and is suitable as a so-called rewritable optical recording medium. This optical recording is expected to have a wide range of applications.This optical recording uses a laser beam to heat a thin film optical recording medium above its melting point, and then rapidly cools it to amorphize the laser irradiated area for recording. The erased portion is heated to a temperature higher than the crystallization temperature using another laser beam and annealed to return it to a crystalline state and erase the erased portion.

Such optical recording media include 5bSe and 5bTe.
Research has been conducted on alloy films with compound compositions mainly composed of
No. 97), in an alloy film with such a compound composition,
Recording and erasing is possible at 1 IJsec or less, but (2) there is little controllability during production in order to obtain a certain specific compound composition.

(2) During repeated recording and erasing, there are problems such as the tendency to deviate from the initial crystalline state, which impairs the initial characteristics of the medium. In order to solve these problems, for example,
As seen in No. 2-166508, high melting point InT
It has also been proposed to use a composition between the two compound compositions of e+ IntTes, but in this case, it is superior in controllability during fabrication, repeatability of recording and erasing, and stability of the recorded state over time at room temperature. However, due to its high melting point, a high-power laser is required for recording, which poses a problem in the recording sensitivity of the medium. Furthermore, since a plastic substrate is used in an actual optical disk, it is necessary that the substrate does not deform even after 106 or more recording and erasing operations. For this reason, there is a restriction that the melting point of the medium cannot be made too high.

(Objective of the Invention) The object of the present invention is to provide a rewritable phase change optical recording medium that has excellent repeatability of recording and erasing, stability over time, fast erasing speed, easy recording, and excellent recording sensitivity. It is about providing.

(Means for Solving the Problems) In order to achieve the above object, the present invention comprises a substrate and an optical recording layer provided on the substrate, the optical recording layer being made of [n and Te]. An optical recording medium which is an alloy film and has an atomic ratio of In and Te between 2:1 and 1:1 or between 2:3 and 2:5; The recording medium is an alloy film made of Ga and Te,
The atomic ratio of e is between 2:1 and 1;1, or 2:3
and 1:3.

However, according to the present invention, the atomic ratio of In and Te is 2:
By setting the ratio between 1 and 1:1 or between 2:3 and 285, the melting point can be lowered compared to when the atomic ratio is between 1:1 and 2:3. It can be an optical recording medium that has the advantages of easy recording and excellent recording sensitivity, and does not lose the characteristics of the latter composition, such as excellent repeatability of recording and erasing and stability over time. Further, by forming the optical recording layer with an alloy film made of Ga and Te, the same effects as those obtained with the above-mentioned In-Te alloy film can be obtained. Also, Ge, Sb+ Sn, As, S
e+ Au, Pb+ Ti.

The erasing speed can be further increased by adding at least one element among Pt and Pd.

Next, examples of the present invention will be described. Note that the embodiments are merely illustrative, and it goes without saying that various changes and improvements can be made without departing from the spirit of the present invention.

(Example 1) FIG. 1 is a sectional view showing a first example of a rewritable phase change optical recording medium l according to the present invention, and in FIG. 710, 2 indicates a thickness of 1.
2m+s glass substrate, 3 is 5lots on glass substrate 2
4 is a recording layer formed with a thickness of 90n on the base N3, and its composition is In□↑e.
hs, and was manufactured using the RF sputtering method. 5 is a transparent film with a thickness of 100 ns formed on the recording layer 4. ! It is a layer. In addition, a3・dap.

Record N4 was amorphous.

The laser recording characteristics were evaluated using the medium I having the above configuration as a sample. First, by -like laser heating,
After the entire surface was brought into a crystalline state, information could be recorded by forming an amorphous spot on the sample surface using a 13 ml I4° 100 na laser pulse.
The conditions under which crystallization was possible were measured while changing the laser power and pulse width, and then the shortest erasing speed was determined. As a result, recorded bits could be erased with a 5 mW, 0.6 μs laser pulse. Further, when the above-described recording and erasing was repeated 10'il&l under the same conditions, no change was observed in the recording and erasing characteristics. In addition, as a result of near-infrared spectroscopy, the change in reflectance between the amorphous state and the crystalline state is 1
It was about 0%.

In addition, the above medium 1 was fixed on a heater and heated, and 10
When the recording state was observed while increasing the temperature at a constant rate of 180° C., it was found that no crystallization occurred up to 180° C., and the recording state at room temperature was sufficiently stable.

Further, in order to evaluate the crystal structure, medium 1 was heat treated at 200° C. for 30 minutes and observed with an X-ray diffractometer. As a result, the diffraction peak was 1nlTe*(333
), (66G), and no peaks of other compound phases appeared.

(Example 2) Next, a second example according to the present invention will be described. In this example, the medium configuration is the same as that of Example 1, and the recording M4 is
Example 1 Using an alloy film having the composition of n5sTeai
A similar experiment was conducted.

First, after heating the whole surface to a crystalline state by -1 laser heating, a 148141100 ns laser pulse is used to form an amorphous spot on the sample surface, which allows information to be recorded. The conditions for crystallization were measured while changing the power and pulse width, and then the shortest erasing speed was determined. As a result, 6mW, 0.5
The recorded bits could be erased with a μs laser pulse. Furthermore, when the above-described recording and erasing was repeated 10 times under the same conditions, no change was observed in the recording and erasing characteristics. Further, as a result of near-infrared spectroscopy, the change in reflectance between the amorphous state and the crystalline state was about 20%.

In addition, the above medium 1 was fixed on a heater and heated, and 10
When the recording state was observed while the temperature was raised at a constant rate of 190° C./min, it was found that no crystallization occurred up to 190° C., and the recording state at room temperature was sufficiently stable.

In addition, to evaluate the crystal structure, the medium was heated to 200°C.
The sample was heat-treated for 30 minutes and observed using an xwA diffractometer. As a result, InTe (110
), (220), (330) peaks appear,
No other compound phase peaks appeared.

Table 1 summarizes the results of tests conducted on alloy films made of In and Te having compositions other than In and Te.

(Example 3) In the third example described here, the same experiment as in Example 1 was conducted using the same medium configuration as in Example 1 and using an alloy film having a composition of Ga□Teas for the recording layer 4. Ta.

First, after making the entire surface into a crystalline state by -like laser heating, a 14 mW, 100 ns laser pulse is used to form an amorphous spot on the sample surface, which allows information to be recorded. The conditions for crystallization were measured while changing the laser power and pulse width, and then the shortest erasing speed was determined. As a result, 6.5mW, 0
．． The recorded bits could be erased with a 7 μs laser pulse. Furthermore, under the same conditions, the above-mentioned recording and erasing can be carried out at 1O
After repeating h times, no change was observed in the recording and erasing characteristics.

Further, as a result of near-infrared spectroscopic analysis, the reflectance change between the amorphous state and the crystalline state was about 15%.

In addition, the above medium 1 is fixed on a heater and heated to lO
When the recording state was observed while increasing the temperature at a constant rate of .degree. C./min, it was found that crystallization did not occur up to 210.degree. C., and the recording state at room temperature was sufficiently stable.

(Example 4) Next, Example 4 will be described. In Example 4, a medium configuration similar to that of Example 1 was used, and Gal1 was used as the recording layer 4.
．． An experiment similar to Example 1 was conducted using an alloy film having a composition of Te44.

First, after making the entire surface into a crystalline state by -like laser heating, an amorphous spot is formed on the sample surface using a laser pulse of 15 mW and LOOns, which enables information to be recorded. The conditions for crystallization were measured while changing the laser power and pulse width, and then the shortest erasing speed was determined. As a result, 7mW, 0.6
The recorded bits could be erased with a μs laser pulse. Furthermore, when the above-mentioned recording and erasing was repeated 10" times under the same conditions, no change was observed in the recording and erasing characteristics. Also, as a result of near-infrared spectroscopy, the reflection in the amorphous state and the crystalline state The rate change was about 18%.

In addition, the above medium 1 is fixed on a heater and heated to lO
When the recording state was observed while increasing the temperature at a constant rate of .degree. C./min, it was found that crystallization did not occur up to 205.degree. C., and the recording state at room temperature was sufficiently stable.

(Example 5) In Example 5, a ternary alloy film obtained by adding 7% to 10% of Au or Ti to the alloy film having the composition of In5sTeths used in Example 1 was used as the recording layer 4, and this medium 1 was , the same experiment as in Example 1 was conducted.

First, after making the entire surface into a crystalline state by laser heating, a laser pulse of 100 ns at %lhW was applied to form an amorphous spot on the sample surface, which allowed information to be recorded. The conditions for crystallization were measured while changing the laser power and pulse width, and then the shortest erasing speed was determined. As a result, 5mW, 0.2
The recorded bits could be erased with a μs laser pulse, and the erasing speed could be increased due to the effect of adding the third element. Furthermore, under the same conditions, the above recording and erasing was performed 10 times.
When the process was repeated six times, no change was observed in the recording and erasing characteristics.

In addition, the above medium 1 was fixed on a heater and heated, and 10
When the recording state was observed while increasing the temperature at a constant rate of 160° C., it was found that no crystallization occurred up to 160° C., and the recording state at room temperature was sufficiently stable.

Furthermore, when the ternary alloy film used in this example was observed with a scanning electron microscope (SEM) after initial crystallization, the size of the crystal grains decreased from about 900 before addition to 300. I also understood that.

Note that in the above examples, Au was used as the additive metal.

Although we have explained the case of T1, in addition to this, Ge, sb
.

It can also be applied to Sn, As, Se, Pbt, Pt, and Pd.

(Effects of the Invention) As explained above, according to the present invention, writing and erasing can be performed by setting the atomic ratio of In and Te to between 2:1 and 1:1 or between 2:3 and 2:5. Even if the process is repeated, the initial medium characteristics can be maintained without loss. In addition, this composition has the advantage that since the crystallization temperature is relatively high, the recording state is stable at room temperature, and when erasing is performed by irradiation with a laser beam, crystallization can be performed quickly with a size of 1 μ3 or less. Further, according to the present invention, since the laser power during recording can be reduced, there is an advantage that recording sensitivity is improved.

For the recording layer, Ga and Te are used instead of In and Te, and the atomic ratio is changed from 2:1 to 181 or 2:
By changing the ratio from 3 to 1:3, a medium having the same characteristics as above can be constructed.

Furthermore, Ss, sb, Snt Au+ Pb+^s
, Ti, and Pt+I'd has the advantage of further improving the erasing speed.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a rewritable phase change optical recording medium according to the present invention. l...Optical recording medium 2...Glass substrate 3...Underlayer 4...T1 layer 5...Protective layer Fig. 1

Claims (8)

[Claims] (1) Comprising a substrate and an optical recording layer provided on the substrate, the optical recording layer is an alloy film made of In and Te, and the atomic ratio of In and Te is 2:1 and 1:1. A rewritable phase change optical recording medium characterized by being between. (2) Comprising a substrate and an optical recording layer provided on the substrate, the optical recording layer is an alloy film made of In and Te, and the atomic ratio of In and Te is 2:3 and 2:5. A rewritable phase change optical recording medium characterized by being between. (3) Ge, Ga, and Sb are added to an alloy film consisting of In and Te with an atomic ratio of In and Te between 2:1 and 1:1.
2. The rewritable phase change optical recording medium according to claim 1, wherein at least one element selected from the group consisting of , Sn, As, Se, Au, Pb, Ti, Pt, and Pd is added. (4) Ge, Ga, and Sb are added to an alloy film consisting of In and Te with an atomic ratio of In and Te between 2:3 and 2:5.
3. The rewritable phase change optical recording medium according to claim 2, wherein at least one element selected from the group consisting of , Sn, As, Se, Au, Pb, Ti, Pt, and Pd is added. (5) Comprising a substrate and an optical recording layer provided on the substrate, the optical recording layer is an alloy film made of Ga and Te, and the atomic ratio of Ga and Te is 2:1 and 1:1. A rewritable phase change optical recording medium characterized by being between. (6) Comprising a substrate and an optical recording layer provided on the substrate, the optical recording layer is an alloy film made of Ga and Te, and the atomic ratio of Ga and Te is 2:3 and 1:3. A rewritable phase change optical recording medium characterized by being between. (7) Ge, Sb, and Sn are added to an alloy film consisting of Ga and Te with an atomic ratio between 2:1 and 1:1.
6. The rewritable phase change optical recording medium according to claim 5, wherein at least one element selected from the group consisting of , As, Se, Au, Pb, Ti, Pt, and Pd is added. (8) Ge, Sb, and Sn are added to an alloy film consisting of Ga and Te whose atomic ratio is between 2:3 and 1:3.
7. The rewritable phase change optical recording medium according to claim 6, wherein at least one element selected from the group consisting of , As, Se, Au, Pb, Ti, Pt, and Pd is added.