JPH0737251A - Optical information recording method - Google Patents

Abstract

PURPOSE:To compensate a shape of spreading out the width of a mark in accordance with a medium of discretionary constitution by using a multipulse recording system and making the value of bias power at the time of recording the mark different from the value of bias power at the time of recording or erasing an interval between the marks. CONSTITUTION:An optical information recording medium formed with a recording layer consisting of a phase transition type recording material is irradiated with a pulse-shaped electromagnetic wave to perform recording in utilizing a change of an optical constant of the recording layer. In this case, at the time of recording the mark, a laser diode 16 is driven by adding a suitable bias level to an output of a strategy generating circuit 12 via a recording time bias level adding circuit 13. Then, at the time of recording or erasing the interval between the marks, a bias level that is higher than at the time of recording the mark is added via an erasing time bias level adding circuit 14. By this method, without needing a complicated control mechanism, the compensation for the spread of the rear end part of the recording mark shape due to the recording pulse waveform can be carried out in accordance with a medium of every possible constitution.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art As one of optical information recording media capable of recording, reproducing and erasing information by irradiating electromagnetic waves, particularly laser beams, so-called phase utilizing a transition between crystal-amorphous phase or crystal-crystal phase is known. Variant recording media are well known. This phase-change type recording medium is capable of overwriting with a single beam, which is difficult for a magneto-optical recording medium, and the optical system on the drive side is simpler. There is. As a typical 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
Examples include so-called chalcogen-based alloy materials such as -Te, Se-Te, and Se-As. In addition, for the purpose of improving stability, high-speed crystallization, etc., a Ge—Te system containing Au (Japanese Patent Laid-Open No.
No. 1-219692), Sn and Au (Japanese Patent Laid-Open No. 61-61980).
-270190), Pd (JP-A-62-1949).
No. 0) is added, and for the purpose of improving repeatability of recording / erasing, Ge-Te-Se-Sb, G
A material with a specified composition ratio of e-Te-Sb (Japanese Patent Laid-Open No. 62-
No. 73438) is also proposed. However, none of them can satisfy all of the characteristics required for a rewritable phase change recording medium. In particular, it can be said that the prevention of reduction of the erase ratio due to the unerased portion at the time of overwriting and the improvement of the number of repeated recordings are the most important issues to be solved.

Japanese Patent Laid-Open No. 63-251290 proposes a recording medium provided with a recording layer having a crystal structure of a ternary or higher multi-component compound single phase. Here, a substantially ternary or higher multi-element compound monolayer is defined to include a compound having a stoichiometric composition of ternary or higher (for example, In ₃ SbTe ₂ ) in the recording layer in an amount of 90 atomic% or more. It is supposed that the recording and erasing characteristics can be improved by using this recording layer. However, this recording medium has drawbacks such as a low erasing ratio. Under these circumstances, it has been desired to develop an optical information recording medium having a high erasing ratio and excellent repeating characteristics. Therefore, development of a protective layer material suitable for a recording layer material has been promoted, and ZnSSiO ₂ , Al ₂ O ₃ , T
Materials such as a ₂ O ₅ , SiN and AlN are used.
However, even a combination of a specific recording layer material and these protective layer materials has not obtained all the properties required for an optical information recording medium.

On the other hand, when an EFM signal, for example, is recorded on the optical information recording medium using the above-mentioned various phase change recording materials by a conventional recording method, the output level of the RF signal is different between the unrecorded portion and the recorded portion. Will be things. This is because the unrecorded portion is in a crystalline state and the recorded portion is in an amorphous state, and the reflectance is different in both states. By the way, when observing the recorded mark portion with a TEM (transmission electron microscope), the recording mark should ideally have a mark shape as shown in FIG. The shape is such that the edges are widened. This is remarkable especially when trying to record a long mark, and in an extreme case, it may even show a shape close to a teardrop shape, which is a major obstacle to the improvement of recording / reproducing characteristics. One of the causes of the recording mark having such a shape is that the temperature of the recording layer rises near the rear end of the mark where a long mark is to be recorded due to the heat storage effect of the irradiated high-power laser beam. This is because the width of the mark portion becomes too wide.
The above-mentioned phenomenon occurs even when the thermal conductivity of the reflection / heat dissipation layer is insufficient.

Therefore, in order to prevent the rear end of the mark from spreading, it is conceivable to use a material having a large thermal conductivity for the reflection and heat dissipation layer, but in that case, the sensitivity is lowered, which is not preferable, and conversely. The phenomenon that the mark width becomes narrow near the rear end of the long mark occurs. Further, when the recording layer is made of a material such as Ag—In—Sb—Te system, which greatly contributes to the cooling rate for the mark formation as the recording material, the cooling rate at the front side of the mark is lower than that at the rear end portion. There is a problem that it is small and the mark width becomes narrow. In any case, the reality is that it is very difficult to control the mark shape only with the layer structure.

For these reasons, it is necessary to compensate the recording mark shape by the recording waveform. As a conventional example, JJAP Vol. 31 (1992) p653-6.
58, JJAP Vol. 30 (1991) p677-
681, 4th Phase Change Record Study Group (1992) p76-
81 and p99-104 and the like, there are examples of methods of compensating the recording mark shape by the recording waveform. However, these methods require a complicated control mechanism and are not compatible with media of all configurations.

[0007]

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

[0008]

According to the present invention, in order to solve the above problems, an optical information recording medium having a recording layer made of a phase change recording material formed on a substrate is irradiated with pulsed electromagnetic waves. In the optical information recording method for recording information by utilizing the change of the optical constant of the recording layer due to the irradiation of the electromagnetic wave, the multi-pulse recording method is used as the recording method, and the value of the bias power at the time of mark recording is set between the marks. There is provided an optical information recording method, which is characterized in that it is different from a bias power value at the time of recording or erasing. Further, according to the present invention, in the above, there is provided an optical information recording method characterized in that the bias power value is made different from the bias power value at the time of recording between marks or at the time of erasing, particularly only when recording a long recording mark portion. Provided. According to the present invention, in the above, the optical information is characterized in that the value of the bias power is made different from the value of the bias power at the time of recording between marks or at the time of erasing, especially only at the time of recording at the end of the long recording mark portion. A recording method is provided. Further, according to the present invention, a pulsed electromagnetic wave is irradiated to an optical information recording medium having a recording layer made of a phase-change recording material formed on a substrate, and the change of the optical constant of the recording layer due to the irradiation of the electromagnetic wave is changed. In an optical information recording method for recording information using the multi-pulse recording method as a recording method, the value of the bias power before and / or after giving the last drive pulse of the mark length is recorded between marks. There is provided an optical information recording method, characterized in that it is different from the bias power value at the time of erasing or erasing. 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 characterized by using an optical information recording medium containing a phase change recording material having a composition and a structure represented by the following general formula (I) in a stable state.

Embedded image (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)))

The method of the present invention will be described in detail below. The present invention is an optical information recording method for irradiating a phase-change recording medium with multi-pulse electromagnetic waves for recording, and is intended to compensate for the distortion of the recording mark shape by devising the pulse waveform during mark recording. Yes, specifically, as shown in FIG. 1, the recording mark shape is optimized by setting the bias power value during mark recording to a value different from the bias power value during mark-to-mark recording or erasure. It is a thing. The value of the bias power is set to an appropriate value depending on the recording layer material, the structure, and the like. By adopting such a recording pulse waveform, it is possible to prevent the temperature of the recording layer from rising excessively due to the heat storage effect due to the energy of the irradiation electromagnetic wave, and to suppress the spread of the mark width at the rear end of the long mark. ,
A mark having an optimized shape as shown in FIG. 4 can be obtained.

In the present invention, as shown in FIG. 1, the bias power value at the time of mark recording may be made to be different from the bias power value at the time of recording between marks or at the time of erasing. The bias power value may be set to be different from the bias power value at the time of recording between marks or at the time of erasing only during recording, and the bias power value may be recorded between marks only at the time of recording at the end of a particularly long recording mark portion. It may be different from the bias power value at the time of erase or erase. Further, in the present invention, the bias power value before, after, or both before and after applying the last drive pulse of the mark length may be different from the bias power value at the time of recording between marks or erasing.

An apparatus configuration for implementing the method of the present invention is shown in a block diagram in FIG. This apparatus includes a recording signal generator 11, a strategy generating circuit 12, a recording bias level adding circuit 13, an erasing bias level adding circuit 14, and L.
It is composed of a D drive circuit 15 and an LD (laser diode) 16.

The method of the present invention can be applied to phase-change recording media of any constitution, but in particular, a quaternary recording material of Ag-In-Sb-Te having a high sensitivity as compared with other recording materials is used. It is particularly effective for the conventional phase change recording medium. An optical information recording medium suitable for the method of the present invention will be described below based on the configuration example of FIG.

The recording medium shown in FIG. 3 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 reflection 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 polycarbonate resin.

The recording layer 3 changes the optical constant upon irradiation with electromagnetic waves, and is preferably a phase-change material, particularly preferably containing Ag, In, Sb, Te as constituent elements, A phase change material whose composition and chemical structure are mainly represented by the following general formula (I) is suitable.

Embedded image (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))), and it is preferable that AgSbTe ₂ crystallites which are at or near the stoichiometric composition exist in the unrecorded area and at the time of erasing. The recording layer 3 is formed by various vapor phase growth methods,
For example, vacuum deposition method, sputtering method, plasma CVD
Method, photo CVD method, ion plating method, 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 10000Å, preferably 2
It is good to set it to 00-2000Å. When the film thickness is less than 100Å, the light absorption ability is remarkably lowered, and it does not serve as a recording layer. Further, if the film thickness is thicker than 10000Å, uniform phase change at high speed is difficult to occur.

The constituent material of the upper heat-resistant protective layer 4 is S
oxides such as iO ₂ , SiO, ZnO, and Al ₂ O ₃ , Si ₃
Suitable are nitrides such as N ₄ , AlN and BN, sulfides such as ZnS and TaS ₄ , or mixtures thereof. In particular, when the rotational linear velocity of the medium is low (1.2 to 5.6 m / s), the thermal conductivity of AlN, BN, SiC, etc. is 1 W /
A material of cm · K or more is suitable. Such materials are
The rapid cooling condition promotes the state change of the recording layer 3. Such a heat-resistant protective layer may be formed by various vapor deposition methods such as vacuum deposition method, sputtering method and plasma CVD method.
Method, photo CVD method, ion plating method, electron beam evaporation method, or the like. The thickness of the heat resistant protective layer is 100 to 5000Å, preferably 200 to 2000Å. When the film thickness is less than 100Å, the heat-resistant protective layer does not function. On the contrary, when the film thickness is more than 5000Å, the sensitivity is lowered and the interfacial peeling is likely to occur. Further, the heat-resistant protective layer can be multi-layered if necessary.

For the reflection / heat dissipation layer 5, a metal material such as Al, Ag, Au, or an alloy thereof can be used. The reflection heat dissipation layer is not always necessary, but it is preferable to provide it in order to release excess heat and reduce the heat load on the disk. Such a reflective heat dissipation layer can be formed by various vapor deposition methods such as vacuum deposition method, sputtering method, plasma CVD method, photo CVD method, ion plating method and electron beam evaporation method. The thickness of the reflective heat dissipation layer is 100 to 3000 Å, preferably 500 to 20
It is good to set it to 00Å. When it is thinner than 100Å, it does not function as a reflection and heat dissipation layer, and conversely 2000Å
If the thickness is larger than the above range, the sensitivity is lowered and the interfacial peeling is likely to occur.

The material of the substrate 1 is usually glass, ceramics, or resin, and a resin substrate is preferable in terms of moldability and cost. Typical examples of the resin include polycarbonate resin, acrylic resin, epoxy resin, polystyrene resin, acrylonitrile-styrene copolymer resin, polyethylene resin, polypropylene resin, silicone resin,
Fluorine-based resins, ABS resins, urethane resins and the like can be mentioned, but polycarbonate resins and acrylic resins are preferable from the viewpoints of processability and optical characteristics. Further, the substrate 1 may have a disc shape, a card shape, or a sheet shape.

The phase change recording medium is preferably initialized by an Ar laser or a semiconductor laser. When a semiconductor laser is used, the power density on the medium surface of the laser 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 laser feed rate is 1 μm / A range of rotation to 100 μm / revolution is suitable.

In the present invention, electromagnetic waves used for recording, reproduction and erasing include laser light, electron beam, X-ray, ultraviolet ray,
Various types of visible light, infrared rays, microwaves, etc. can be adopted, but when mounted on a drive, a small and compact semiconductor laser is most suitable.

[0020]

EXAMPLES The present invention will be specifically described below with reference to examples. Example 1 A ZnS / SiO ₂ protective layer 2000Å, Ag-In-Sb-Te was formed on a polycarbonate substrate having a pitch of about 1.6 μm and a depth of about 700Å, a thickness of 1.2 mm and a diameter of 120 mm by RF sputtering. Recording layer (composition ratio: Ag: In: Sb: Te = 12: 13: 51: 24) 2
An optical disk was manufactured by sequentially laminating 00Å, 300 Å of AlN protective layer, and 700Å of Ag reflective layer. Initialization of the optical disk is performed by a semiconductor laser with a power of 10 mW and a linear velocity of 1.3.
It was performed at m / s. As shown in FIG. 1, all marks (from the shortest mark length to the minimum mark length) of the optical disc manufactured by the above method have a lower bias power value at the time of recording marks than during recording between marks (during erasure). Recording was performed with a multi-pulse waveform that gives a value. as a result,
Compared to the case of constant bias power, the mark shape was optimized and the second harmonic distortion and erase ratio were improved.

Example 2 Using the same optical disk as in Example 1, the bias power value was set low only when recording a mark having a particularly long mark length (for example, a length of 7T or 8T or more in the case of the EFM recording system). . Even in this way, the same effect as in Example 1 was obtained.

Example 3 Using the same optical disk as in Example 1, only the bias power value after the last drive pulse for recording a mark having a particularly long mark length was set to be low during multi-pulse drive. . Even in this way, the same effect as in Example 1 was obtained.

Example 4 Using the same optical disk as in Example 1, the value of the bias power was set low before and after the last drive pulse for recording a mark having a particularly long mark length was given during multi-pulse drive. Even in this way, the same effect as in Example 1 was obtained.

[0024]

According to the present invention, the value of the bias power at the time of recording marks is set to a value different from the value of the bias power at the time of recording between marks or at the time of erasing to make the trailing edge of the multi-recording pulse waveform dull. Since the irradiation of pulsed electromagnetic waves is performed, it becomes possible to perform the compensation of the recording mark shape by the recording pulse waveform for media of any configuration without the need for a complicated control mechanism. The recording / reproducing characteristics of the variable recording medium can be further improved.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing an apparatus configuration for implementing the method of the present invention.

FIG. 3 is a cross-sectional view showing a layer structure of a recording medium to which the method of the present invention is preferably applied.

FIG. 4 is a diagram showing an ideal recording mark shape.

FIG. 5 is a diagram showing a recording mark shape in which a mark width of a rear end portion is widened.

[Explanation 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 Strategy Generating Circuit 13 Recording Bias Level Adding Circuit 14 Erasing Bias Level Adding Circuit 15 LD Driving Circuit 16 LD (Laser diode)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshiyuki Kageyama 1-3-6 Nakamagome, Ota-ku, Tokyo Within Ricoh Co., Ltd. (72) Hiroko Iwasaki 1-3-6 Nakamagome, Ota-ku, Tokyo Shares Within Ricoh Company (72) Inventor Katsuyuki Yamada 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company Ricoh (72) Inventor Masaetsu Takahashi 1-3-6 Nakamagome, Tokyo Stockholder Ricoh Company ( 72) Inventor Koji Deguchi 1-3-6 Nakamagome, Ota-ku, Tokyo Within Ricoh Co., Ltd.

Claims (5)

[Claims] 1. An optical information recording medium having a recording layer made of a phase-change recording material formed on a substrate is irradiated with pulsed electromagnetic waves, and the change in the optical constant of the recording layer caused by the irradiation of the electromagnetic waves is utilized. In an optical information recording method for recording information, a multi-pulse recording method is used as a recording method,
An optical information recording method characterized in that a bias power value at the time of recording marks is made different from a bias power value at the time of recording between marks or erasing. 2. The bias power value is made different from the bias power value at the time of recording between marks or at the time of erasing only when recording a particularly long recording mark portion.
The optical information recording method described in. 3. The optical information according to claim 1, wherein the value of the bias power is made different from the value of the bias power at the time of recording between marks or at the time of erasing only at the time of recording at the end of a particularly long recording mark portion. Recording method. 4. An optical information recording medium having a recording layer made of a phase-change recording material formed on a substrate is irradiated with a pulsed electromagnetic wave, and the change in the optical constant of the recording layer caused by the irradiation of the electromagnetic wave is utilized. In an optical information recording method for recording information, a multi-pulse recording method is used as a recording method,
An optical information recording method, characterized in that the value of the bias power before and / or after applying the last drive pulse of the mark length is made different from the value of the bias power at the time of recording between marks or at the time of erasing. 5. A recording layer, a protective layer, and a reflection heat dissipation layer are formed on a substrate as the optical information recording medium, and the recording layer contains at least Ag, In, Sb, and Te as constituent elements, and in a stable state. 5. The optical information recording method according to claim 1, wherein an optical information recording medium mainly composed of a phase change recording material having a composition and structure represented by the following general formula (I) is used. . Embedded image (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)))