JP2001155337A - Method for recording and reproducing information, device for recording and reproducing information and information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an information recording medium and an information recording and reproducing device of high performance by providing a method for forming a minute recording domain and a method for reproducing the formed domain with high resolution as a coherent recording/reproducing system. SOLUTION: In the information recording device having at least a very minute light source and the information recording medium for recording information, the purpose described above is attained by reproducing information recorded on the information recording medium by irradiating an information recording medium surface with light emitted from a very minute light source and detecting change of reflectivities the light before cast to the information recording medium surface and the light after cast and reflection on the medium surface. Further it is most preferable that the very minute light source used in this invention is one where a slit having a minute pin hole on a proceeding way of the light is provided and a diameter of the pin hole is <=300 nm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording apparatus for storing a large amount of information quickly and accurately, and more particularly to a high-performance and highly reliable information recording medium, The present invention relates to a reproducing method suitable for information recording, and further relates to an information recording / reproducing apparatus using the recording medium and the reproducing method.

[0002]

2. Description of the Related Art In recent years, there has been a remarkable progress in the advanced information society, and multimedia in which various forms of information are integrated has rapidly spread. There are a magnetic disk device and an optical disk device as information recording devices supporting this.
These devices are used in fields that take advantage of their respective characteristics.

[0003] At present, the magnetic disk drive is being downsized while improving the recording density. In parallel,
The cost reduction of disk devices is rapidly progressing. By the way, in order to realize high density of magnetic disk,
1) Reducing the distance between the disk and the magnetic head 2)
Indispensable techniques include increasing the coercive force of the medium and 3) devising a signal processing method. Above all, in a magnetic recording medium, an increase in coercive force is indispensable for realizing high-density recording. In addition, in order to achieve high-density recording exceeding 40 Gb / in ² , the unit in which magnetization reversal occurs must be reduced. For that purpose, it is necessary to reduce the size of the magnetic particles, and as a method for achieving this, it has been proposed to provide a seed layer below the magnetic film. One example is USP-4652499.

On the other hand, in an optical disk device that performs recording, reproduction, or erasing using a laser beam, it is effective to form a minute magnetic domain using a laser beam having a short wavelength in order to perform high-density recording. In this case, the wavelength of the laser beam becomes shorter, and the Kerr effect exhibited by the amorphous alloy of the rare earth element and the iron group element, which is the recording medium, decreases, so that the reproduction output-to-noise ratio (S / N) decreases. In some cases, stable information recording cannot be performed. To solve this problem, P that exhibits a large Kerr effect even in the short wavelength region of 400 nm or less
An artificial lattice film in which t and Co are alternately stacked has been proposed.
As an example, JP-A-1-251356 can be mentioned.
In addition, a recording method using a lens having a large aperture ratio has been proposed. Further, in the reproducing method, a reproducing method using a magnetic super-resolution method (MSR) has been proposed in addition to the reproducing method using the short wavelength light. In addition, there has been proposed a magnetic domain enlarging method in which a magnetic domain formed at the time of reproduction is enlarged to increase a reproduction signal.

However, in a phase change type optical recording medium or a write-once type optical recording medium, high density recording is realized by miniaturization of crystal grains such as magnetic recording or MSR such as magneto-optical recording.
It has been difficult to improve the recording density due to this. In particular, the prior art has not sufficiently established a reproducing method having higher resolution without crosstalk than recording.

[0006]

In the above prior art,
A reproduction method corresponding to high-density recording in optical recording using phase change and write-once optical recording has not been fully established,
High density recording has not always been achieved sufficiently.

Accordingly, a first object of the present invention is to provide a method for reproducing a minute recording domain with high resolution. A second object of the present invention is to provide a method for forming a minute recording domain and a method for reproducing the formed domain with high resolution as a consistent recording / reproducing method.
An object of the present invention is to provide a high-performance information recording medium and an information recording / reproducing apparatus.

As described above, an object of the present invention is to provide an information reproducing method and an information recording medium suitable for performing ultra-high-density recording exceeding 100 Gb / inch ² and an information recording and reproducing apparatus using them.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide an information recording apparatus having at least a very small light source and an information recording medium for recording information. The information recorded on the information recording medium is reproduced by detecting a change in the reflectance between the light after the light irradiated on the information recording medium surface is reflected on the medium surface and the light before the irradiation. This can be achieved by: By the way, the extremely small light source used in the present invention has a structure in which a slit having a minute pinhole is provided in the course of light, and the diameter of the pinhole is most preferably 300 nm or less.

[0010] Here, the reflectivity that occurs before and after the reproduction light is reflected on the surface of the information recording medium changes due to the evaporation of the recording medium in the portion irradiated with the laser, or the crystal-amorphous, crystal-crystal, or Most preferably, the change is caused by a phase transformation between / and amorphous-amorphous. The information recording medium used for this purpose is most preferably a chalcogenide compound-based material. More specifically, as an information recording material for chalcogenide compounds, G
e, Sb, In, Pb, As, Sn, Ag, Bi, Ga, Tl, Co, C, Pd and at least one element selected from Te and Se and at least one element selected from Are preferred. Most preferably, such an information recording medium is formed on a disk, a tape, or a circular sheet. The disc may be glass, aluminum alloy, or resin, and NiP
Needless to say, a film may be formed.

More specifically, the apparatus includes an information recording medium formed on at least a substrate, a laser light source that can be narrowed down to a fixed spot size by a lens, a micro light source, a disk drive system, and an electric circuit including at least a signal processing and control system. Most preferably, an information recording / reproducing device is configured. To record information on an information recording medium, a laser light source narrowed down to a certain spot size by at least a lens is used. Then, an information recording / reproducing apparatus configured to detect a change in reflectance as a reproduction signal by using at least an extremely small light source to reproduce the recorded information. In this device, a particularly great effect can be obtained when the recording domain size of the information recorded on the information recording medium is 0.3 μm or less in a width measured in the moving direction (track direction) of the information recording medium. It is most preferable to use a multi-pulse as a recording pulse to form a size recording domain.

Various types of information are recorded, reproduced, or erased by using the information recording medium, the information reproducing method, and the information recording and reproducing apparatus described above. Preferably, the information to be recorded, erased or reproduced is at least one of audio information, code data, image information, and control information for controlling the disk device. In addition, recording using the change in light reflectance can be performed once or at least two times.
Preferably, recording can be performed more than once. For this purpose, it is preferable to use a method in which information is recorded on the information recording medium by causing the information recording medium to melt by irradiation with a recording laser beam and then undergoing a phase transformation upon evaporation or cooling to record the information. .

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to embodiments. (Embodiment 1) This embodiment is a case where recording / reproduction is performed by using a change in light reflectance accompanying a phase change between crystalline and amorphous. In-Sb-Te was used for the recording film. An example of the composition of the recording film is In ₂₂ Sb ₃₇ Te ₄₃ . FIG. 1 shows a schematic diagram of a cross-sectional structure of the manufactured disk. First, the substrate for the disk (1)
A 3.5 ″ diameter polycarbonate substrate having uneven guide grooves on the surface was used as the substrate.
This is just an example, and it goes without saying that the effects of the present invention are not affected by using a disk substrate of any size or by using a substrate made of amorphous polyolefin or the like. The substrate for the recording medium is not limited to a disk shape, and may be a tape-shaped or sheet-shaped film substrate.
Further, a glass or Al alloy substrate may be used.

On this substrate (1), Al-T is used as a light reflecting film (2).
An i film was formed to a thickness of 120 nm. Pure Ar as discharge gas, Al ₉₀
Ti ₁₀ alloy was used for each target. The pressure during sputtering is 15 mTorr, and the input RF power is 0.5 kW / 150 mmφ.
Here, no difference was found between the composition of the obtained thin film and the composition of the target. Next, as an inorganic compound thin film (3), a silicon oxide-zinc sulfide film was formed by a sputtering method. SiO ₂ -ZnS was used as a target, and Ar was used as a discharge gas. The pressure during sputtering is 10 mTorr, and the input RF power is 0.7 kW / 150 mmφ. The thickness of the formed inorganic compound thin film (3) is 25 nm. In the thermal design of the information recording medium, the film thickness is as thick as 200 nm or more for the slow cooling type and conversely, 30 nm or less for the rapid cooling type. On this film, an In ₂₂ Sb ₃₇ Te ₄₃ film was formed as a recording film (4) to a thickness of 25 nm by a sputtering method. The pressure during sputtering is 5mTor
r, Input RF power is 1.5kW / 150mmφ. Finally, as an inorganic compound thin film (3), a silicon oxide-zinc sulfide film was formed to a thickness of 150 nm by a sputtering method.

The reproduction characteristics of the above disk were evaluated. FIG. 2 shows an outline of the apparatus used for the evaluation. Information recording medium (104)
A recording domain (107) having a width of 0.30 μm in the track direction and 0.5 μm in the direction perpendicular to the track is formed in advance. For reproduction, a light source (100) using a semiconductor laser having a wavelength of 680 nm was used, and the light was converted to a pinhole (10 mm) having a diameter of 200 nm.
The information recording medium was irradiated through the slit (101) having 2). Here, the light reflected and returned from the information recording medium (104) was separated by the beam splitter (103). This light is converted into an electric signal by the detector (105), and the information is reproduced. Here, the change is detected when the light reflectance changes.
By using this method, the width in the track direction is 0.3
A magnetic domain of μm to 0.2 μm (0.4 μm perpendicular to the track) was successfully reproduced. When the playback signal output was measured, C /
N = 55-58 dB was obtained. The erasure ratio was 35 dB. Although reproducing the information had been pre-recorded, the user may be his recording, the number of times of rewriting of the information recording medium in this case was at least 10 ⁵ times.

For recording, a recording waveform having a pattern shown in FIG. 3 is used. Here, the laser power is composed of two levels, one of which has a lower power is a crystallization level, and a higher power is an amorphous level. Record data. As described above, it was found that information recorded by using an extremely small light source can be favorably reproduced.

In this embodiment, In-Sb-Te is used for the information recording film. However, Ge-Sb-Te, In-Sb-Se, In-Sb, Sn-Te-
Similar effects were obtained by using a recording material such as Se, Ge-Te-Sn, and In-Se-Tl-Co. (Embodiment 2) This embodiment is an example in which light from an extremely small light source is used for reproducing a write-once optical disc. Here, Se ₂₀ Te ₇₅ Pb ₅ was used as the information recording material. The structure of the disc is
The recording film was directly formed on a glass or plastic substrate by a vacuum evaporation method. For recording, the recording film is irradiated with laser light to evaporate the heated portion of the recording film.
Recording is performed by making a hole in the recording film. A change in reflectance is formed depending on the presence or absence of the recording film. To form a minute recording domain, it is particularly effective to use a multi-pulse. As a result, the recorded information is
The regeneration was carried out using the system shown in FIG. By using this technique, a magnetic domain having a width in the track direction of 0.3 μm to 0.2 μm (0.4 μm in the direction perpendicular to the track) was successfully reproduced. When the reproduction signal output was measured, C / N = 56 to 59 dB was obtained. As described above, it was found that information recorded by using an extremely small light source can be favorably reproduced. In addition, as an information recording film
Te-C, Te-Pd-O, Te-C-Pd, etc. may be used.

(Embodiment 3) In this embodiment, an alloy type recording film is used as the information recording film. As the recording film, a film having a two-layer structure of Sb ₂ Se ₃ / Bi ₂ Te ₃ is used. In this method, recording is performed by utilizing the fact that the reflectivity changes because the recording film is warmed and the two layers form an alloy by mutual diffusion during recording. FIG. 4 is a schematic diagram showing a cross-sectional structure of this disk. First, a 3.5 ″ diameter polycarbonate substrate having an uneven guide groove on the surface was used as a substrate (1) for a disk. The substrate used here is only one example,
It goes without saying that the effect of the present invention is not affected by using a disk substrate of any size or by using a substrate made of amorphous polyolefin or the like.
Further, a glass or Al alloy substrate may be used.

On the substrate (1), Al-T is used as a light reflecting film (2).
An i film was formed to a thickness of 100 nm. Pure Ar as discharge gas, Al ₉₀
Ti ₁₀ alloy was used for each target. The pressure during sputtering is 15 mTorr, and the input RF power is 0.5 kW / 150 mmφ.
Here, no difference was found between the composition of the obtained thin film and the composition of the target. Next, an Sb ₂ Se ₃ film was formed as a heat insulating layer (5) by a vacuum evaporation method. The film thickness is 150 nm.
Next, as the recording layer (6), a Bi ₂ Te ₃ film was formed to a thickness of 15 nm by a vacuum evaporation method. Next, an Sb ₂ Se ₃ film was formed as an antireflection layer (7) by a vacuum evaporation method. The film thickness is 30
nm. Here, the heat absorption is designed to mainly occur in the recording layer. Finally, as the inorganic compound layer (3),
A silicon nitride film was formed by a sputtering method. The film thickness is 50
nm. Si and Al / N2 were used as targets and discharge gases, respectively. The pressure during sputtering is 10 mTorr, and the input RF power is 0.7 kW / 150 mmφ.

The recorded information was reproduced using the system shown in FIG. By using this method, magnetic domains with a width in the track direction of 0.2 μm to 0.1 μm (0.3 to
0.4 μm). When the reproduction signal output was measured, C / N = 56 to 59 dB was obtained. As described above, it was found that information recorded by using an extremely small light source can be favorably reproduced.

[0021]

According to the present invention, a large light reproduction output is obtained by reproducing a change in light reflectance by using a laser beam (ultra-miniature light source) passing through a slit having a fine pinhole of 300 nm or less. be able to. This gives 0.1
It was possible to provide a reproducing method capable of reproducing with good resolution at a high resolution even in a recording domain having a size of μm or less. As a result, an ultra-high-density information recording / reproducing apparatus and a reproducing method suitable for the apparatus can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a cross-sectional structure of an information recording medium.

FIG. 2 is a diagram showing an information reproducing method using a minute light source.

FIG. 3 is a diagram showing an example of a recording waveform of a phase change optical disk.

FIG. 4 is a schematic diagram showing a cross-sectional structure of an information recording medium.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Light reflection film 3 ... Inorganic compound film 4 ... Magnetic film 5 ... Heat insulation layer 6 ... Recording layer 7 ... Antireflection layer 100 ... Laser light source 101 ... Slit 102 ... Pinhole 103 ... Beam splitter 104 ... Information recording medium 105… Detector 106… Comparator 107… Recording domain

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Teruaki Takeuchi 1-1-88 Ushitora, Ibaraki City, Osaka Prefecture Inside Hitachi Maxell Co., Ltd. (72) Koichiro Wakabayashi 1-1-88 Ushitora, Ibaraki City, Osaka Hitachi Maxell F term (reference) 5D029 JB04 JC02 5D090 BB05 CC01 CC04 CC14 CC16 CC18 DD02 EE01 EE11 FF11 GG12 HH01 JJ01 LL02 LL09

Claims (14)

[Claims] 1. An information recording / reproducing method for irradiating an information recording medium with a laser beam to perform recording and performing reproduction using an extremely small light source, wherein the extremely small light source comprises a semiconductor laser and a laser emitted from the semiconductor laser. A semiconductor package provided with at least a slit having a pinhole having a diameter of 50 nm or more and 300 nm or less provided in the course of light, and irradiating light emitted from the pinhole to the surface of the information recording medium, Reproducing information from the information recording medium by detecting a change in reflectivity between the light after the light applied to the surface is reflected on the medium surface and the light before reflection on the medium surface; Playback method. 2. The change in reflectance is caused by a change in reflectance due to evaporation of an information recording medium, or a phase transformation between crystal-amorphous, crystal-crystal, and / or amorphous-amorphous. 2. The information recording / reproducing method according to claim 1, wherein the information recording / reproducing method occurs. 3. The information recording / reproducing method according to claim 1, wherein a width of the recording mark measured in a moving direction of the information recording medium is smaller than a diameter of the pinhole. 4. The information recording / reproducing method according to claim 1, wherein the information recording medium has a recording layer using a chalcogenide compound-based material. 5. The recording layer is composed of Ge, Sb, In, Pb, As, Sn, Ag, B
A material comprising at least one element selected from i, Ga, Tl, Co, C, and Pd and at least one element selected from Te and Se. 4. The information recording / reproducing method according to item 4. 6. The recording using the change in the light reflectance is 1
2. The information recording / reproducing method according to claim 1, wherein the information can be recorded once or at least twice. 7. The information recording / reproducing method according to claim 1, wherein a multi-pulse is used as a recording pulse for recording by irradiating the laser beam. 8. The recording method according to claim 1, wherein the recording is performed by irradiating the information recording medium with a laser beam, wherein the recording layer is melted and then undergoes a phase transformation upon evaporation or cooling. Information recording and reproduction method described. 9. Information comprising at least a laser light source, a lens for narrowing a laser beam emitted from the laser light source to a fixed spot size, a disk drive for rotating an information recording medium, and an electric circuit. An information recording / reproducing apparatus, comprising: a slit having a pinhole having a diameter of 50 nm or more and 300 nm or less in the course of laser light emitted from the laser light source. 10. An information recording / reproducing apparatus according to claim 9, wherein said electric circuit includes a circuit for detecting a change in reflectance. 11. The information recorded on the information recording medium is at least one of audio information, code data, image information, and control information for controlling a magnetic disk drive. 10. The information recording / reproducing apparatus according to 10. 12. A semiconductor laser and a laser beam emitted from the semiconductor laser having a diameter of 50 n provided on the way.
irradiating light emitted from a semiconductor package having at least a slit having a pinhole of m or more and 300 nm or less,
In an information recording medium for reproducing information by detecting a change in reflectivity between light after irradiation and light before reflection, the information recording medium is Ge, Sb, In, P
b, As, Sn, Ag, Bi, Ga, Tl, Co, C, Pd, at least one element selected from the group consisting of at least one element selected from Te, Se An information recording medium comprising: 13. The information processing apparatus according to claim 12, wherein the information on the information recording medium is at least one of audio information, code data, image information, and control information for controlling a magnetic disk drive. Information recording medium. 14. The information recording medium according to claim 12, wherein said information recording medium is a disk, a tape, or a circular sheet.