JP2001291277A - Recording medium and recording and reproducing device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recording medium having separated recording units in which recording sensitivity is improved and fast recording and reproduction are possible, and to provide a recording device which uses the medium. SOLUTION: In the recording medium having recording units 14 and a separation layer 13 to separate each recording unit 14 from others, the separation layer 13 absorbs light to convert it into heat, absorbs light to change the volume or absorbs light to transfer the energy to the recording units.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a recording medium capable of recording at high density by light and a recording / reproducing apparatus using the same.

[0002]

2. Description of the Related Art In an information-oriented society in recent years, a recording / reproducing method having a remarkably high recording / recording density, and a recording / reproducing apparatus and a recording medium based on the recording / reproducing method, corresponding to an ever-increasing amount of information. Is long-awaited. Along with this, it has been required to cope with miniaturization of a recording unit which is a unit for writing information in these recording / reproducing devices and recording media.

However, in a recording / reproducing apparatus and a recording medium, it is difficult to cope with miniaturization of a recording unit.

In a normal magnetic medium, several tens Gb / inch ²
Therefore, it is considered that recording cannot be performed due to thermal disturbance and the recording medium is shifted to a perpendicular magnetization recording medium. Several hundred Gb / i
nch occur thermal agitation at ² in the vertical magnetic recording medium, therefore high magnetic coercivity media is required. However, also in this case, a strong magnetic field is required, and recording cannot be performed. Therefore, light (heat) assisted magnetic recording, in which the medium temperature is increased by light or heat to reduce the coercive force and then written by a magnetic head, has attracted attention. For reading, a high-sensitivity magnetic sensor such as a GMR head is used. However, even when a perpendicular magnetization medium is used, the terabit density that requires a domain wall of 30 nm or less is expected to be considerably severe.

[0005] In the current recording medium, a polycrystal having a wide particle size distribution is used for the recording layer. However, due to the thermal fluctuation of the crystal, recording becomes unstable in a small polycrystal. There is no problem when the recording unit is large, but if the recording unit is small, recording instability and noise increase. This is because the number of crystal grains included in the recording unit is reduced, and the interaction between the recording cells is relatively large.

The situation is the same in optical recording using a phase change medium, and recording is not possible at a recording density of several hundred gigabits per inch square or more, where the recording unit size is almost the same as the crystal size of the phase change medium. The medium becomes unstable and the medium noise increases.

In order to avoid this problem, there has been proposed a magnetic recording medium in which medium noise is reduced by isolating magnetic particles of uniform size (SY Chou, SY).
et. al. J. Appl. Phys. 76 (199
4), pp6673-6675). It has also been proposed to perform recording and reproduction with one isolated magnetic particle.

On the other hand, as a technique for realizing optical recording, a Near spot capable of forming a minute spot smaller than the wavelength of light is used.
-Field Scanning Optical M
A technique using the microscope (NSOM) has been proposed. For example, Betzig et al. Irradiate the output of an Ar ion laser to a Co / Pt multilayer film with an NSOM probe to try to record / reproduce information magneto-optically and obtain a diameter of 60 nm.
m recording pattern (Appl. Phys).
s. Lett. 61, 142 (1992)). Also, H
osaka et al, the NSOM probe of the output of the semiconductor laser, the phase is changed by irradiating the _Ge 2 _Sb 2 Te ₅ thin film having a thickness of 30 nm, it is realized recording pattern having a diameter of 50nm (Thin Solid Films 273,1
22 (1996); Appl. Pbys. 79,8
082 (1996)). However, it is expected that these methods cannot cope with a recording density on the order of 1 terabit per square inch where the spot diameter is about 20 nm because the recording spot becomes large due to heat diffusion and the required energy is large. .

On the other hand, Japanese Patent Application Laid-Open No. 8-45122 discloses that
A recording medium for performing recording by forming a dot-shaped (domain structure) recording region having a diameter of 10 to 100 nm made of an organic dye molecule, which can be expected to be capable of higher density, and injecting electric charge into the recording region is disclosed. Have been.

As described above, in order to enable ultrahigh-density recording on the order of 1 terabit per square inch, a recording medium in which recording units are separated by a separation layer is indispensable from the viewpoint of recording stability and reduction of noise. Thought,
No practical recording medium has been realized yet. The major cause is the recording sensitivity. That is, as the recording density increases, the recording time / reading time of one recording unit decreases. Therefore, the amount of energy of light or the like applied to the recording unit is reduced, so that it is required not only to separate the recording units but also to increase the recording / reading sensitivity.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to increase the recording sensitivity in a recording medium in which recording units are separated,
An object of the present invention is to provide a recording medium capable of high-speed recording / reproducing and a recording / reproducing apparatus using the same.

[0012]

According to the present invention, there is provided a recording medium provided with a recording unit and a separation layer for separating each recording unit, wherein the separation layer absorbs light and converts the light into heat. Or absorbing light to cause a volume change, or absorbing light and transferring energy to a recording unit.

That is, by activating the separation layer with respect to light, which has been almost inactive to light or heat, the light energy efficiency can be increased and the recording / reading sensitivity can be increased.

In the heat mode recording, heat obtained by absorbing light by the separation layer is transmitted to the recording unit as heat,
Also, the energy efficiency is increased by the separation layer transmitting light energy to the recording unit by energy transfer and converting it into heat in the recording unit. For heat conduction, the temperature of the separation layer rises rapidly, and it is preferable to conduct heat to the recording unit by increasing the temperature gradient, and a substance having low specific heat, high thermal conductivity, and high light absorption Is preferred. As such a substance, for example, graphite, a metal or a semiconductor having a small reflection coefficient, for example, chromium or silicon is preferable. For energy transfer, it is preferable that the separation layer contains a fluorescent substance, and the recording unit contains a substance whose fluorescence and absorption wavelength overlap. Also, when the separation layer absorbs light and causes a volume change, distortion occurs at the interface between the separation layer and the recording unit. By utilizing the distortion, the transfer of the recording medium can be easily caused. As such a recording medium, organic and inorganic phase change media can be preferably used.

In photon mode recording, the light energy obtained by the separation layer is transmitted to a recording unit by energy transfer. For energy transfer, it is preferable that the separation layer contains a fluorescent substance, and the recording unit contains a substance whose fluorescence and absorption wavelength overlap. Examples of such a photon mode recording medium include a photochromic medium, a photocharge medium whose conductivity changes by light and switches charge injection, a medium whose magnetic properties change by light, and a photoisomerization medium.

The above-described heat transfer, energy transfer, and volume change have a greater effect when combined with each other than when they occur alone.

Further, the recording medium according to the present invention is further characterized in that a separation layer having a higher light absorption rate than the recording unit is provided, that the thickness of the recording unit is larger than the minimum width of the recording unit, The recording unit and the separation layer may be sandwiched by a material layer having higher thermal conductivity than the recording unit.

Generally, it is difficult for a recording unit to increase only light absorption due to repetition of recording and readout characteristics. Therefore, the effect described above becomes more remarkable by making the light absorption rate of the separation layer larger than the recording unit. The heat transfer and energy transfer from the separation medium to the recording medium become remarkable when the film thickness of the recording unit and the minimum width of the recording unit approach, that is, when the recording density increases. When the film thickness of the recording unit is larger than the minimum width of the recording unit, the effect is particularly remarkable. When the recording unit and the separation layer are sandwiched by a material layer having a higher thermal conductivity than the recording unit, heat generated in the recording unit can be quickly released to the material layer, so that light-assisted magnetic recording is performed. In this case, it is easy to invert the recording and to make the phase change recording amorphous. However, if heat escapes too easily, it will not be possible to record in recording units,
The thermal conductivity of the material layer is preferably substantially the same as or lower than that of the separation layer.

In a recording / reproducing apparatus according to the present invention, in a recording medium provided with a recording unit and a separation layer for separating each recording unit, whether the separation layer absorbs light and converts it into heat,
A recording medium characterized by absorbing light and causing a volume change, or absorbing light and transferring energy to a recording unit, means for irradiating the recording medium with near-field light, and recording on the recording layer. Means for reading out the read signal.

As means for irradiating near-field light, a minute aperture may be formed on a flying or contact slider such as a magnetic disk drive as a near-field light head, or a probe used in a probe microscope, such as a probe. May be installed together with means for precisely controlling the vertical distance. The recording medium can be used in the form of a disk which is rotated or used in combination with a near-field optical head which is two-dimensionally driven in the form of a card. One or more means for irradiating near-field light to one recording medium may be used.

As a means for sensing light, a method utilizing a change in a photodiode or laser oscillation is preferable. As a means for sensing magnetism, a head utilizing the magnetoresistance effect is preferable. As a means for sensing an electric field, a field effect transistor and a single electron transistor are preferable.

Further, these may be combined with a write head for applying a magnetic field or an electric field. The means for irradiating near-field light and the means for writing or reading a signal may be provided separately, or may be provided integrally with one head.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to embodiments.

First Embodiment FIG. 1 shows a sectional view of a recording medium 10 shown in this embodiment.

Chromium and gold are respectively deposited on the surface of a quartz substrate 11 having a diameter of 2.5 inches by vacuum evaporation to a thickness of 10 nm and 50 nm as an electrode layer 12, and a magnetic particle burying layer (separation layer) 13 is formed on the surface as europium as a coloring center. Was doped to a thickness of 100 nm by a sputter deposition method. Al-OH bonds, which are polar groups, are formed on the surface of alumina. The silicon substrate was immersed in an aqueous dispersion of 40 nm-diameter fine particles of polystyrene covered with an amino group having an affinity for Al-0H for 10 minutes, and excess fine particles were removed by washing with water. After drying, the obtained fine particle film was observed by AFM. As a result, fine particles were formed on one surface, and almost no defects without fine particles were observed.

Next, the surface of the fine particles is etched by 10 nm by RIE to leave an interval between the fine particles, and then platinum is laminated as a mask by sputtering to a thickness of 10 nm. Thereafter, the particles were removed by ultrasonic treatment in toluene, and the separation layer 13 was exposed on the surface only where the particles were present, and the other surface was covered with a mask.

The thus-prepared product was subjected to RIE using fluorocarbon to form a separation layer of 100 nm until it reached the electrode layer 12.
m anisotropic etching, diameter 20nm, depth 100nm
A cylindrical hole was made. Thereafter, nickel was buried in a hole as a magnetic material by electroplating using the electrode 12 as an electrode to produce a recording unit 14. Further, an amorphous carbon film was deposited thereon as a protective film 15 to a thickness of 20 nm. A magnetic recording medium 10 in which recording units having a diameter of 20 nm and a depth of 100 nm arranged at intervals of 40 nm were isolated was prepared.

Next, a recording / reproducing apparatus 20 shown in FIG. 2 was prepared.

The output 6 having a wavelength of 620 nm for inputting the recording medium 10, the slider head 21, and the near-field light head light 6
A mW semiconductor laser 22 and an objective lens 23 were installed. 24 is a motor for rotating the disk. A near-field optical head 25, a magnetic head 26, and a GMR head 27 are integrated in the slider head.

The recording medium 10 is rotated at 4000 rpm, and the magnetic head 26 is continuously irradiated with near-field light.
The signal was written with. For reproduction, a magnetic signal was read by the GMR head 27. A signal of 400 gigabits per square inch could be read at a CN ratio of 28 dB.

Comparative Example 1 A recording medium and a recording / reproducing apparatus were produced in the same manner as in Example 1 except that colorless and transparent alumina was used instead of europium-doped alumina.

A signal was written with a magnetic head while rotating the recording medium at 4000 rpm and continuously irradiating near-field light. For reproduction, a magnetic signal was read by a GMR head. 400 gigabits per inch squared signal 7d
It was found that data could not be read at the B / N ratio of B, and that writing of data was insufficient.

Second Embodiment FIG. 3 is a cross-sectional view of a recording medium 30 according to the present embodiment. An optically polished glass disk 31 having a diameter of 120 mm and a thickness of 1.2 mm is formed on a glass disk 31 having a conductive layer and a reflective film. Membrane 3
2 was deposited in a thickness of 200 nm. An electron beam resist and a mixed solution of tetraphenylporphyrin and polydiisobutyl fumarate were spin-coated as a colored separation layer 33 to a thickness of 50 nm. Using an EB lithography apparatus, a circular region having a diameter of 30 nm was irradiated with an electron beam at intervals of 50 nm at the center. After developing with ethanol, the chemical formula

Embedded image The organic dye molecules which cause the crystal-amorphous transition indicated by are deposited. After the vapor deposition, the substrate was heated at 140 ° C. for 2 hours in a nitrogen atmosphere. AFM observation confirmed that the organic dye molecules were arranged as recording units 34 in a dot shape having a diameter of 30 nm. The organic dye molecule is considered to have a crystalline state. SiO2 was sputtered thereon as a protective film 35 to produce the recording medium 30. The thermal conductivity of the Al film 32 and the protective film 35 is higher than that of the recording unit 34.

Next, a recording / reproducing apparatus 40 shown in FIG. 4 was prepared.

Near-field light is emitted from a semiconductor laser 41 having a wavelength of 450 nm and an output of 10 mW via an optical fiber 42 having an opening having a diameter of 10 nm, and the recording medium 30 is transmitted to a motor 4.
Irradiation was performed in a spiral shape while rotating at 1000 rpm using the No. 3 to change the organic dye molecule dots from crystalline to amorphous. Reference numeral 44 denotes a mount for fixing the optical fiber, and a lubricant (not shown) is interposed between the recording medium and the mount to keep the distance at 20 nm. Reference numeral 45 denotes a power supply of the semiconductor laser, which can change the output. The reflected light having an output of 2 mW was detected by the semiconductor photodiode 46. 47
Is a condenser lens, and 48 is an optical fiber. 200 gigabits per inch square signal is 20dB C
Reading was possible at N ratio.

Comparative Example 2 A recording medium and a recording / reproducing apparatus were produced in the same manner as in Example 2 except that only colorless and transparent polyisobutyl fumarate was used instead of tetraphenylporphyrin and polydiisobutyl fumarate. . In the same manner as in Example 2, a signal of 200 gigabits per square inch could be read out only at a CN ratio of 7 dB, and it was found that recording was insufficient.

Third Embodiment A recording medium and a recording / reproducing apparatus were manufactured in the same manner as in the second embodiment except that a polyimide film was used instead of the Al film and a polyimide film was used instead of the SiO2 film.
As in the second embodiment, 20 per inch square is used.
A 0 gigabit signal could be read with a 15 dB CN ratio.

Fourth Embodiment FIG. 5 shows a sectional view of a recording medium 50 shown in this embodiment. An electron beam resist and colored separation are applied on a glass disk 51 having a diameter of 120 mm and a thickness of 1.2 mm which has been optically polished. Chemical formula for layer 52

Embedded image Was spin-coated with a mixed solution of a fluorescent dye and polydiisobutyl fumarate to a thickness of 50 nm.
Using an EB lithography system, the center of a circular region having a diameter of 30 nm is 5
An electron beam was irradiated at intervals of 0 nm. After developing with ethanol, the chemical formula

Embedded image The photochromic dye shown by was vapor-deposited. After the vapor deposition, the substrate was heated at 140 ° C. for 2 hours in a nitrogen atmosphere. AFM observation confirmed that the photochromic dye molecules were arranged as dots having a diameter of 30 nm as recording units 53.
SiO2 was sputtered thereon as a protective film 54 to produce a recording medium 50.

Next, a recording / reproducing apparatus 60 shown in FIG. 6 was prepared.

Near-field light is transmitted from a semiconductor laser 61 having a wavelength of 400 nm and an output of 10 mW via an optical fiber 62 having an opening having a diameter of 10 nm, and the recording medium 50 is transmitted to a motor 6.
Using No. 3, irradiation was performed in a spiral shape while rotating at 1000 rpm to react the photochromic dye. Reference numeral 64 denotes a mount for fixing an optical fiber. A lubricant (not shown) is interposed between the recording medium and the mount, and the distance is 2 mm.
It is kept at 0 nm. Numeral 65 denotes a power supply of the semiconductor laser, whose output can be varied. 67 is a condenser lens and 68
Is an optical fiber. The fluorescent molecule (2) can be energy-transferred to the photochromic dye (3).

The reading was performed by using a semiconductor laser 69 having a wavelength of 480 nm and an output of 2 mW, and measuring the reflected light with a semiconductor photodiode 66. A signal of 200 gigabits per square inch could be read at a CN ratio of 18 dB.

[0042]

As described above, according to the present invention, there is provided a recording medium capable of increasing recording sensitivity and recording / reproducing at high speed in a recording medium in which recording units are separated, and a recording apparatus using the same. And its industrial value is enormous.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a recording medium according to a first embodiment.

FIG. 2 is a diagram showing the recording / reproducing apparatus shown in the first embodiment.

FIG. 3 is a sectional view of a recording medium according to a second embodiment.

FIG. 4 is a diagram showing a recording / reproducing apparatus according to a second embodiment.

FIG. 5 is a cross-sectional view of a recording medium according to a fourth embodiment.

FIG. 6 is a diagram showing a recording / reproducing device according to a fourth embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Magnetic recording medium 11 ... Quartz substrate 12 ... Electrode layer 13 ... Separation layer 14 ... Recording unit 15 ... Protective film 20 ... Recording / reproducing apparatus 21 ... Slider head 22 ... Semiconductor laser 23 ... Objective lens 24 ... Motor 25 ... Near-field light Head 26 ... Magnetic head 27 ... GMR head 30 ... Magnetic recording medium 31 ... Glass disk 32 ... Al film 33 ... Separation layer 34 ... Recording unit 35 ... Protective film 40 ... Recording / reproducing device 41 ... Semiconductor laser 42 ... Optical fiber, 43 ... Motor 44 mount 45 power supply 46 semiconductor photodiode 47 condensing lens 48 optical fiber 50 recording medium 51 glass disk 52 separation layer 53 recording unit 54 protective film 60 recording / reproducing device 61 semiconductor laser 62 Optical fiber 63 ... Motor 64 ... Mount 65 ... Power supply 66 ... Semiconductor photodiode 67 ... Condensing lens 68 ... Optical fiber 69 ... Semiconductor laser

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G11B 11/10 502 G11B 11/10 502Z 11/105 566 11/105 566C

Claims (5)

[Claims] In a recording medium provided with a recording unit and a separation layer for separating each recording unit, the separation layer absorbs light and converts it into heat, or absorbs light and causes a volume change. Or a recording medium, which absorbs light and transfers energy to the recording unit. 2. The recording medium according to claim 1, further comprising a separation layer having a higher light absorption than the recording unit. 3. The recording medium according to claim 1, wherein a thickness of the recording unit is larger than a minimum width of the recording unit. 4. The recording medium according to claim 1, wherein the recording unit and the separation layer are sandwiched by a material layer having higher thermal conductivity than the recording unit. 5. In a recording medium provided with a separation layer for separating each of the recording units and each of the recording units, the separation layer absorbs light and converts it into heat, or absorbs light and converts the volume into a volume. A recording medium that causes a change or absorbs light to transfer energy to the recording unit, a unit that irradiates the recording medium with near-field light, and a unit that reads a signal recorded in the recording unit. A recording / reproducing apparatus characterized in that: