JP2596478B2 - Rewritable optical information recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called rewritable optical information recording medium capable of optically recording, reproducing and erasing information (hereinafter simply referred to as an optical medium). It is an object of the present invention to provide a recording film material for an optical medium which has improved durability against environmental temperature in a state and shortens an erasing time.

[0002]

2. Description of the Related Art Reversible structural change (phase change) between an amorphous state and a crystalline state of a substance caused by light irradiation, mainly laser light irradiation, is actively used for recording information. Such a phase-change rewritable optical information recording medium has a large recording capacity in addition to a high-speed information processing capability, and is expected as a future information storage device.

[0003] As the speed of information processing becomes more severe in this optical medium, the performance of erasing information recorded at high speed at higher speed is required. On the other hand, efforts are being made to improve the environmental stability of the recorded information. Have been paid. Normally, recording on an optical medium is performed by irradiating a laser beam on a recording film that has been crystallized in advance to form an amorphous region. Will rapidly crystallize and disappear. Therefore, it is desired that the crystallization temperature be as high as possible.

[0004]

It is known that a Ge—Te—Sb ternary recording film material has a high-speed erasing performance in a compound composition on a line connecting GeTe and Sb ₂ Te _3. It stayed at 130-150 ° C. Efforts have been made to further increase the crystallization temperature of this recording film material, and it has been found that excessive addition of Sb makes it possible. However, as the addition amount of Sb is increased, the crystallization temperature is increased, but on the other hand, the erasing time is prolonged. Therefore, efforts to increase the crystallization temperature are limited as long as high-speed erasing performance is maintained. And the crystallization temperature was limited to about 170 ° C.

According to the present invention, in a Ge—Te—Sb ternary recording film, the recording film containing Sb in excess from the line of the compound connecting GeTe and Sb ₂ Te ₃ increases as the Sb content of the recording film increases. In view of the contradictory nature of the erasing time, which is longer than the crystallization temperature, an attempt was made to increase the crystallization temperature without increasing the erasing time even when Sb was excessively added. Things.

The present invention was made to solve the above problems, replacing excess Te elements of the recording film added with Sb to the compound composition on the line connecting the GeTe and Sb ₂ Te ₃ in Se element At the same time , the recording film is formed by replacing the Sb element with the Bi element.
[(Sb-Bi) ₂ (Te-Se) ₃ ] z｝ 1-x · S
When represented by bx, y / z is 0.5 to 3, and x is 0.5
From 0.7 to 0.05 or from 0.05 to 0.15
And the substitution amount of Bi is 1 to 3 at% and that of Se
The substitution amount is in the range of 1 to 10 at%.
You.

[0007]

The crystallization is achieved by adding an excessive amount of Sb to partially replace the Te element, which is a constituent element of the Ge—Te—Sb ternary recording film, with the Se element, and further replacing a part of the Sb element with the Bi element. It is possible to simultaneously improve and raise the temperature and shorten the erasing time.

[0008]

【Example】

Embodiment 1 FIG. 1 shows an example of the configuration of the optical medium of the present invention. Transparent substrate 11
Dielectric film 12, recording film 13, dielectric film 14, and metal film on top
15 are sequentially laminated. The transparent substrate 11 is a sufficiently cleaned glass substrate, and the dielectric films 12 and 14 are Z
nS and an Al alloy were used for the metal film 15. The substrate material is not limited to glass, but may be any material that can be used. For example, a resin such as polycarbonate or PMMA can be used. The dielectric film material is ZnS
The sulfide other than ZnS, Si
Oxides such as O ₂ and Al ₂ O ₃ , nitrides such as Si ₃ N ₄ , Z
Se compound such as nSe, mixed film of sulfide and oxide such as ZnS and SiO ₂ , mixed film of Se compound and oxide such as ZnSe and SiO ₂ , mixed of sulfide and nitride such as ZnS and Si ₃ N ₄ A film, a mixed film of a nitride of a Se compound such as ZnSe, Si ₃ N _{4 and the} like, and the like can be used. Dielectric film
The thickness of each of the dielectric film 12, the dielectric film 14, and the metal film 15 is 120, respectively.
nm, 20, and 100 nm. The recording film 13 has Ge, T
Five elements e, Sb, Bi and Se were used as main constituent elements, and {(GeTe) _Y [(Sb-Bi) ₂ (Te-Se) ₃ ] _z } _1- X.Sbx was used. The thickness of the recording film 13 was about 20 nm. Dielectric film 1
2. The dielectric film 14, the recording film 13, and the metal film 14 were all formed by high-frequency magnetron sputtering. This film forming method is not limited to the high-frequency magnetron sputtering method, for example, DC sputtering method, vacuum evaporation method,
Any method capable of forming a film, such as a spin coating method and a plasma CVD method, may be used. A composite target or an alloy target was used as the target for the recording film. The composition of the recording film was confirmed by photoelectron optical analysis. The crystallization temperature of the recording film was measured for the As-Depo film by a differential scanning calorimeter.

As shown in FIG. 2, the recording and erasing characteristics in the stationary state are as follows.
Laser beam from optical head 21 consisting of 0.52 objective lens
22 was examined by focusing and irradiating a laser beam 22 on the recording film 13 from the glass substrate 11 side. Prior to the measurement of the recording / irradiation characteristics, the recording film 13 was initially crystallized by laser annealing or heat treatment. When performing the heat treatment, the surface of the metal film 15 was further covered with a dielectric film (about 100 nm). The recording is the signal contrast C I _C: signal strength of the recording state I _A: defined as the signal strength of unrecorded state, was recorded a recording pulse value as a constant. The shortest erasing time was determined as the minimum pulse width required for relaxing the erasing signal output with the erasing laser output kept constant while recording was performed with a constant signal contrast. Table 1 shows the composition of the recording film material, the crystallization temperature, the shortest erasing time, and the number of recording / erasing repetitions determined by experiments.

[0010]

[Table 1]

The shortest erasing time was measured with a constant pulse width of 90 ns and a signal contrast of 25-30%. X =
0.6, Y / Z = 2 and the substitution amount of Be and Se respectively
At 4.4at%, the crystallization temperature is 28 ℃ more than when X = 0
The temperature increased to 178.5 ° C, which was a good value. The shortest erasing time at that time was as short as about 70 ns, which was desirable for high-speed erasing. The crystallization temperature was further increased to 196.6 ° C. when the amount of Bi was reduced to に while the amount of Se was substituted as it was, which was desirable for environmental stability of the recorded state. At this time, the shortest erasing time was 60 ns, and the high-speed erasing performance was preserved and showed a good value. Conversely, the replacement amount of Bi is 5 at.
%, It is not preferable because the shortest erasing time stops at about 60 ns, but the crystallization temperature is rapidly lowered, and in addition, it becomes difficult to be non-crystallized.

When the Bi substitution amount is set to 4.4 at% and the Se substitution amount is increased to 6.7 at%, the crystallization temperature is increased, and the shortest erasing time is about 60 ns. Was. However, the replacement amount of Se is 10at%.
As described above, the crystallization temperature is gradually increased to about 200 ° C. as the substitution amount increases, but this is not preferable because the shortest erasing time rapidly deteriorates. From X = 0.5
In the range of 0.15, not only does the crystallization temperature drop, but also
The shortest erasing time was prolonged, which was not preferable. X
In the range of 0.15 to 0.05, a high crystallization temperature such as X = 0.5 or more cannot be obtained, but a 10-25 ° C improvement over that of the compound composition can be achieved, and high-speed erasing performance can be maintained. Met. When X is more than 0.7, the effect of improving the crystallization temperature cannot be expected, and in addition, it becomes difficult to form an amorphous state, which is not preferable.

When the ratio Y / Z is 3/1 or more, the crystallization temperature is increased, and the high-speed erasing performance is preserved. However, the repetition characteristics of recording and erasing deteriorate, and it is difficult to repeat 106 times. Was. When Y / Z is に な る or less, the high-speed erasing performance is preserved, but the crystallization temperature is lowered, which is not desirable. Te Se
If the substitution of either one without performing the substitution with Bi and the substitution of Sb with Bi at the same time, the following undesirable results were obtained. As shown in Table 1, only the substitution of Te with Se is preferable in that a small amount of substitution increases the crystallization temperature and attains high-speed erasing performance. However, the repetition performance of recording and erasing deteriorates, and the number of repetitions is 105. It was something that stopped. This is not desirable because not only the crystallization temperature is remarkably lowered like Bi of Sb, but also it becomes difficult to be amorphized.

[0014]

According to the Ge-Te-Sb- based recording film material, a predetermined amount of Te element is replaced by Se element in the recording film in which Sb is excessively added to the compound composition on the line connecting GeTe and Sb ₂ Te _3. By replacing the Sb element with the Bi element by a predetermined amount without deteriorating the high-speed erasing performance
By improving the crystallization temperature, it becomes possible to increase the environmental temperature durability in the recording state.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view showing a configuration of an optical medium according to one embodiment of the present invention.

FIG. 2 is a layout diagram showing a measurement form of recording and erasing characteristics in a stationary state.

[Explanation of symbols]

 11 Transparent substrate 12 Dielectric film 13 Recording film 14 Dielectric film 15 Metal film 21 Optical head 22 Laser light

 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-1-287836 (JP, A) JP-A-63-225934 (JP, A) JP-A-1-116937 (JP, A) Application in the spring of 1988 Proceedings of the Physical Society of Japan 3rd volume, 838 pages, Lecture number 28p-ZQ-1

Claims (2)

(57) [Claims] 1. A rewritable optical information recording medium in which light irradiation causes a reversible phase transition between an amorphous state and a crystalline state of a recording medium, thereby enabling information recording and erasing. Is ｛(GeTe) y [(Sb-Bi) ₂ (Te-S
e) When ₃ ] z｝ 1-x · Sbx, y / z is in the range of 0.5 to 3, x is in the range of 0.5 to 0.7, and the substitution amount of Bi is 1 to 3 at% and A rewritable optical information recording medium, wherein the amount of Se is in the range of 1 to 10 at%. 2. A rewritable optical information recording medium in which light irradiation causes a reversible phase transition between an amorphous state and a crystalline state of a recording medium, thereby enabling information recording and erasing. Is ｛(GeTe) y [(Sb-Bi) ₂ (Te-S
e) When ₃ ] z｝ 1-x · Sbx, y / z is in the range of 0.5 to 3, x is in the range of 0.05 to 0.15, and the substitution amount of Bi is 1 to 3 at% and The amount of Se substitution is in the range of 1 to 10 at%.
Rewritable optical information recording medium that.