JP3255204B2 - Optical information recording method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for irradiating a pulsed electromagnetic wave to an optical information recording medium having a recording layer made of a phase-change recording material formed on a substrate and irradiating the recording layer with an optical constant. The present invention relates to an optical information recording method for recording information using a change in the information.

[0002]

2. Description of the Related Art As one of optical information recording media on which information can be recorded, reproduced and erased by irradiation of electromagnetic waves, particularly laser beams, a so-called phase utilizing a transition between a crystal and an amorphous phase or a crystal and a crystal phase. Variants are well known. This phase-change recording medium can be overwritten by a single beam, which is particularly difficult for magneto-optical recording media, and the drive-side optical system is simpler. I have. As a typical example of the material used for the phase change recording medium, as disclosed in US Pat. No. 3,530,441, G
e-Te, Ge-Te-Sn, Ge-Te-S, Ge-
Se-S, Ge-Se-Sb, Ge-As-Se, In
And so-called chalcogen-based alloy materials such as -Te, Se-Te, and Se-As. For the purpose of improving stability, high-speed crystallization, etc., Au was added to Ge-Te system (Japanese Patent Laid-Open No.
No. 1-219692), Sn and Au (Japanese Patent Application Laid-Open No. SHO 61-61).
-270190), Pd (JP-A-62-1949).
No. 0 publication) or the like, and Ge-Te-Se-Sb, G
A material having a specified e-Te-Sb composition ratio (Japanese Unexamined Patent Publication No.
No. 73438). However, none of them can satisfy all the characteristics required as a rewritable phase-change recording medium. In particular, it can be said that prevention of a reduction in the erasing ratio due to unerased data during overwriting and improvement in the number of repetitive recordings are the most important issues to be solved.

Japanese Patent Application Laid-Open No. 63-251290 proposes a recording medium provided with a recording layer having a crystal structure of a ternary or higher compound single phase. Here, the ternary or higher multi-component compound monolayer is defined as a recording layer containing 90 atomic% or more of a compound having a ternary or higher stoichiometric composition (eg, In ₃ SbTe ₂ ). By using this recording layer, the recording and erasing characteristics can be improved. However, this recording medium has disadvantages such as a low erasing ratio. Under these circumstances, development of an optical information recording medium having a high erasing ratio and excellent repetition characteristics has been desired. For this reason, the development of a protective layer material suitable for the recording layer material has been advanced, and ZnSSiO ₂ , Al ₂ O ₃ , T
Materials such as a ₂ O ₅ , SiN, and AlN are used.
However, even with a combination of a specific recording layer material and these protective layer materials, a material that satisfies all of the various characteristics required for an optical information recording medium has not been obtained.

On the other hand, when a mark recorded on a conventional phase-change recording medium by a conventional method is observed with a TEM (transmission electron microscope), the recording mark should ideally have a mark shape as shown in FIG. The thing which should be, in fact, has a shape in which the rear end of the mark is widened as shown in FIG. This is particularly remarkable when a long mark is to be recorded. In an extreme case, the shape may be close to a teardrop shape, which is a major obstacle to improving the recording and reproducing characteristics. One of the causes of the recording mark having such a shape is that near the rear end of the mark where a long mark is to be recorded, the temperature of the recording layer rises due to the heat storage effect of the irradiated high-power laser beam. The width of the mark portion is too large. The above-mentioned phenomenon also occurs when the thermal conductivity of the reflection heat radiation layer is slightly insufficient.

In order to prevent the rear end of the mark from spreading, it is conceivable to use a material having a high thermal conductivity for the reflective heat dissipation layer. In that case, however, the sensitivity is lowered, which is not preferable. A phenomenon that the mark width becomes narrow near the rear end of a long mark occurs. When the recording layer is made of a recording material such as Ag-In-Sb-Te, which greatly contributes to the formation of the mark, such as an Ag-In-Sb-Te system, the cooling rate at the front of the mark is lower than that at the rear end. There is a problem that the mark width is small and the mark width becomes narrow. In any case, it is actually difficult to control the mark shape only with the layer configuration.

[0006] For these reasons, it is necessary to compensate the recording mark shape by the recording waveform. 31 (1992) p653-6
58, JJP Vol. 30 (1991) p677-
681, 4th Phase Change Recording Research Group (1992) p76-
There is an example of a method of compensating a recording mark shape by a recording waveform such as 81 and p99-104. However, these methods require a complicated control mechanism and cannot be applied to media of all configurations.

[0007]

SUMMARY OF THE INVENTION In view of the above-mentioned circumstances of the prior art, the present invention does not require a complicated control mechanism, and can compensate for the shape of a recording mark by a recording waveform for any type of media. It is an object to provide an optical information recording method.

[0008]

According to the present invention, in order to solve the above-mentioned problems, a pulse-like electromagnetic wave is applied to an optical information recording medium having a recording layer made of a phase-change recording material formed on a substrate. In an optical information recording method for recording information using a change in an optical constant of a recording layer due to irradiation of the electromagnetic wave, irradiation of a pulse-like electromagnetic wave is performed by slowing down a falling edge of a recording pulse waveform. An optical information recording method is provided. Further, according to the present invention, there is provided an optical information recording method according to the above, wherein a multi-pulse waveform is used as a recording pulse waveform, and a falling edge of each waveform of the multi-pulse train is blunted. Further, according to the present invention, there is provided an optical information recording method as described above, characterized in that when recording a particularly long recording mark, the falling edge of only the pulse waveform for recording the last part of the recording mark is blunted. Further, according to the present invention, in the above, as the optical information recording medium, a recording layer, a protective layer, and a reflective heat dissipation layer are formed on a substrate, and the recording layer contains at least Ag, In, Sb, and Te as constituent elements. There is provided an optical information recording method comprising using an optical information recording medium comprising a phase-change recording material having a composition and a structure mainly represented by the following general formula (I) in a stable state.

(AgSbTe _{(2 + σ / Δ)} ) _x (InSb _z ) _1-x (I) (where 0.4 ≦ x ≦ 0.55, 0.5 ≦ z ≦ 2.
5, −0.15 ≦ σ ≦ 0.1, Δ = (1−σ) x / (1+
3x + z (1-x)).

Hereinafter, the method of the present invention will be described in detail. The present invention is directed to an optical information recording method for performing recording by irradiating a pulse-shaped electromagnetic wave to a phase-change recording medium, in which an attempt is made to compensate for distortion of a recording mark shape by devising a pulse waveform at the time of mark recording. Specifically, as shown in FIG. 1, the shape of the recording mark is optimized by slowing down the fall of the recording pulse waveform. By adopting such a recording pulse waveform, it is possible to prevent the temperature of the recording layer from excessively rising due to the heat storage effect by the energy of the irradiation electromagnetic wave, and to suppress the spread of the mark width at the rear end of a long mark. 7, a mark having an optimized shape as shown in FIG. 7 can be obtained.

In the present invention, as the driving method of the recording laser pulse, a one-pulse recording method as shown in FIG. 1 or a multi-pulse recording method as shown in FIG. 2 can be used. When the one-pulse recording method is used, only the pulse waveform used when recording a long recording mark may be blunted at the falling portion. In the case of using the multi-pulse recording method, the falling edge of each waveform of the multi-pulse train may be blunted as shown in FIG. Only the fall may be blunted.

FIG. 3 is a conceptual diagram of a drive circuit for slowing down the fall of the recording pulse waveform, and FIG. 4 is an operation timing chart thereof. FIG. 5 is a block diagram showing an apparatus configuration for implementing the method of the present invention. This apparatus comprises a recording signal generator 11, a driving pulse generation circuit 1
2, rising drive circuit 13, falling drive circuit 1
4. LD drive circuit 15 and LD (laser diode)
16 is comprised.

The method of the present invention can be applied to a phase-change type recording medium having any structure, but particularly uses a quaternary recording material of Ag-In-Sb-Te which is more sensitive than other recording materials. This is particularly effective for a phase change type recording medium. Hereinafter, an optical information recording medium suitable for the method of the present invention will be described based on the configuration example of FIG.

The recording medium shown in FIG. 6 comprises a substrate 1 on which a lower heat-resistant protective layer 2, a recording layer 3, an upper heat-resistant protective layer 4, and a reflective heat dissipation layer 5 are provided. The lower heat-resistant protective layer 2 is not necessarily provided, but is preferably provided when the substrate 1 is made of a material having low heat resistance such as a polycarbonate resin.

The recording layer 3 changes the optical constant when irradiated with an electromagnetic wave, and is preferably a phase-change material, particularly preferably containing Ag, In, Sb or Te as a constituent element. A phase-change material whose composition and chemical structure are mainly represented by the following general formula (I) is preferable.

(AgSbTe _{(2 + σ / Δ)} ) _x (InSb _z ) _1-x (I) (where 0.4 ≦ x ≦ 0.55, 0.5 ≦ z ≦ 2.
5, −0.15 ≦ σ ≦ 0.1, Δ = (1−σ) x / (1+
3x + z (1-x))) It is preferable that AgSbTe ₂ microcrystals having a stoichiometric composition or a similar stoichiometric composition exist at the unrecorded portion and at the time of erasing. The recording layer 3 is formed by various vapor deposition methods,
For example, vacuum deposition, sputtering, plasma CVD
, An optical CVD method, an ion plating method, an electron beam evaporation method, or the like. In addition to the vapor phase growth method, a wet process such as a sol-gel method can be used. The thickness of the recording layer 3 is 100 to 10,000 °, preferably 2 to 100 °.
It is good to be 00-2000 degrees. When the film thickness is less than 100 °, the light absorbing ability is remarkably reduced, and the film does not function as a recording layer. On the other hand, when the film thickness is more than 10,000 °, uniform phase change at high speed becomes difficult to occur.

The constituent material of the upper heat-resistant protective layer 4 is S
oxides such as iO ₂ , SiO, ZnO, Al ₂ O ₃ , Si ₃
Nitride such as N ₄ , AlN and BN, sulfide such as ZnS and TaS ₄ or a mixture thereof is suitable. In particular, when the medium has a low rotational linear velocity (1.2 to 5.6 m / s), the thermal conductivity of AlN, BN, SiC, etc. is 1 W /
Materials of cm · K or more are preferred. Such materials are
The rapid cooling condition promotes a change in the state of the recording layer 3. Such a heat-resistant protective layer can be formed by various vapor deposition methods, for example, a vacuum deposition method, a sputtering method, and a plasma CVD method.
, An optical CVD method, an ion plating method, an electron beam evaporation method, or the like. The thickness of the heat-resistant protective layer is 100 to 5000 °, preferably 200 to 2000 °. When the thickness is less than 100 °, the function as a heat-resistant protective layer is not achieved. Conversely, when the thickness is more than 5000 °, the sensitivity is lowered and interface peeling is liable to occur. If necessary, the heat-resistant protective layer may have a multilayer structure.

The reflective heat radiation layer 5 can be made of a metal material such as Al, Ag, Au, or an alloy thereof. Although the reflective heat radiation layer is not always necessary, it is preferable to provide the heat radiation layer so as to release excessive heat and reduce the heat load on the disk. Such a reflective heat dissipation layer can be formed by various vapor deposition methods, for example, a vacuum evaporation method, a sputtering method, a plasma CVD method, a photo CVD method, an ion plating method, an electron beam evaporation method, and the like. The thickness of the reflective heat dissipation layer is 100 to 3000 °, preferably 500 to 20 °.
It is good to be 00 °. When the thickness is less than 100 °, the function as a reflective heat dissipation layer is not achieved, and conversely, 2000 °.
If the thickness is larger than that, the sensitivity is lowered or the interface is easily peeled.

The material of the substrate 1 is usually glass, ceramics or resin, and a resin substrate is suitable in terms of moldability and cost. Representative examples of the resin include polycarbonate resin, acrylic resin, epoxy resin, polystyrene resin, acrylonitrile-styrene copolymer resin, polyethylene resin, polypropylene resin, silicone resin,
Examples thereof include a fluorine resin, an ABS resin, and a urethane resin, and a polycarbonate resin and an acrylic resin are preferable in view of workability and optical characteristics. The substrate 1 may have a disk shape, a card shape or a sheet shape.

It is preferable that the phase change recording medium is initialized by an Ar laser or a semiconductor laser. When a semiconductor laser is used, the power density of the laser on the surface of the medium is in the range of 5 × 10 ⁷ to 1 × 10 ¹⁰ W / m ² , the linear velocity of the medium is 1 m / s to 30 m / s, and the feed speed of the laser is 1 μm / A range of rotation to 100 μm / rotation is suitable.

In the present invention, the electromagnetic waves used for recording, reproducing and erasing include laser light, electron beam, X-ray, ultraviolet light,
Various types of light, such as visible light, infrared light, and microwave, can be used, but when mounted on a drive, a small and compact semiconductor laser is optimal.

[0020]

The present invention will be specifically described below with reference to examples. Example 1 A ZnSSiO ₂ protective layer 2 was formed on a polycarbonate substrate having a pitch of about 1.6 μm and a depth of about 700 ° and a thickness of 1.2 mm and a diameter of 120 mm by RF sputtering.
Ag-In-Sb-Te recording layer (composition ratio is A
g: In: Sb: Te = 12: 13: 51: 24) 20
An optical disk was manufactured by sequentially laminating 0%, an AlN protective layer 300%, and an Ag reflective layer 700%. Initialization of the optical disk is performed by a semiconductor laser with a power of 10 mW and a linear velocity of 1.3 m.
/ S. The switches SW1 and SW2 are turned ON / OFF at the timing shown in FIG. 4 by using the drive circuit having the concept shown in FIG. 3 on the optical disk created by the above method.
By turning it off, as shown in FIG. 1, an optical output pulse waveform of a one-pulse drive system with a slow fall was obtained. Marks formed by laser irradiation with this pulse waveform have an improved rear end spread, and a second harmonic distortion of 3
Up to 5 dB.

Example 2 An optical disk similar to that of Example 1 was used, and a one-pulse recording method similar to that of Example 1 was used, but only the pulse waveform used for recording a long recording mark had a slow fall. As a result, as a whole, the mark shape could be improved as in the first embodiment.

Using the same optical disk as in the first embodiment, using a multi-pulse two-step modulation recording method, and using a driving circuit whose concept is shown in FIG. At the timing shown, each switch SW1, S
Recording was performed by driving the LD by turning on / off W2 to slow down the falling edge of each pulse of the multi-pulse. As a result, the mark shape was improved, and the second harmonic distortion was improved by 3 to 5 dB.

[0023]

According to the present invention, a pulse-like electromagnetic wave is emitted by slowing down the falling edge of a recording pulse waveform, so that a recording mark using a recording pulse waveform can be obtained without requiring a complicated control mechanism. Shape compensation can be performed for media of any configuration, and the recording / reproducing characteristics of the phase change recording medium can be further improved.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a recording pulse waveform in a one-pulse recording method according to the present invention.

FIG. 2 is an explanatory diagram of a recording pulse waveform in a multi-pulse recording method according to the present invention.

FIG. 3 is a conceptual diagram of a drive circuit for forming a recording pulse waveform with a falling edge.

FIG. 4 is an operation timing chart of the drive circuit of FIG. 3;

FIG. 5 is a block diagram showing an apparatus configuration for realizing the method of the present invention.

FIG. 6 is a sectional view showing a layer structure of a recording medium to which the method of the present invention is suitably applied.

FIG. 7 is a diagram showing an ideal recording mark shape.

FIG. 8 is a diagram illustrating a recording mark shape in which a mark width at a rear end is widened.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Substrate 2 Lower heat-resistant protective layer 3 Recording layer 4 Upper heat-resistant protective layer 5 Reflective heat dissipation layer 11 Recording signal generator 12 Drive pulse generation circuit 13 Rise drive circuit 14 Fall drive circuit 15 LD drive circuit 16 LD (laser diode)

──────────────────────────────────────────────────続 き Continuing on the front page (72) Yoshiyuki Kageyama 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Hiroko Iwasaki 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company, Ltd. (72) Katsuyuki Yamada, Inventor 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company Ricoh Company (72) Masayoshi Takahashi 1-3-6, Nakamagome, Ota-ku, Tokyo Stock Company In Ricoh Company (72) Inventor Koji Deguchi 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company Limited (56) References JP-A-62-170035 (JP, A) JP-A-1-107335 ( JP, A) JP-A-2-64927 (JP, A) JP-A-3-9880 (JP, A) JP-A-4-78031 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 7/00-7/013 G11B 7/125 G11B 7/24

Claims (4)

(57) [Claims] An optical information recording medium in which a recording layer made of a phase-change recording material is formed on a substrate is irradiated with a pulsed electromagnetic wave, and a change in the optical constant of the recording layer due to the irradiation of the electromagnetic wave is used. 1. An optical information recording method for recording information, comprising: irradiating a pulse-like electromagnetic wave by slowing down a falling edge of a recording pulse waveform. 2. The optical information recording method according to claim 1, wherein a multi-pulse waveform is used as a recording pulse waveform, and a falling edge of each waveform of the multi-pulse train is blunted. 3. An optical information recording method according to claim 1 or 2, characterized in that blunt end portion fall of only a pulse waveform for recording of the recording marks when recording the recording mark. 4. As the optical information recording medium, a recording layer, a protective layer, and a reflective heat radiation layer are formed on a substrate, and the recording layer contains at least Ag, In, Sb, and Te as constituent elements, and is in a stable state. The optical information recording method according to any one of claims 1 to 3, wherein an optical information recording medium mainly comprising a phase-change recording material having a composition and a structure represented by the following general formula (I) is used. . (AgSbTe _{(2 + σ / Δ)} ) _x (InSb _z ) _1-x (I) (where 0.4 ≦ x ≦ 0.55, 0.5 ≦ z ≦ 2.
5, −0.15 ≦ σ ≦ 0.1, Δ = (1−σ) x / (1+
3x + z (1-x)).