JP2002251809A - Information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an information recording medium by which servo tracking is performed exactly and stable head traveling is possible even in the case of arranging a detector extremely in the neighborhood of the recording medium. SOLUTION: A magneto-optical disk 10 is provided with a magnetic recording layer 16 formed on a disk-like flat supporting body 14 for magnetically recording information and the layer 16 is magnetized previously coaxially with the center of the disk or spirally so as to array magnetized areas A and magnetized areas B of different magnetizing directions alternately in a radial direction. Thus, tracking can continuously be performed and exact servo tracking can be performed. Furthermore, it is not required to form projections and recesses at a disk-like plane substrate and stable head traveling is possible even in the case of arranging the detector extremely in the neighborhood of the recording medium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording medium, and more particularly to an information recording medium in which tracking servo information is magnetically preformatted.

[0002]

2. Description of the Related Art With the dramatic increase in the amount of information handled by personal computers, large-capacity, low-cost, and short-access-time information recording media have been developed one after another. Examples of such a large-capacity information recording medium include a built-in magnetic recording medium such as a hard disk, and a removable magnetic recording medium such as ZIP developed by Iomega Corporation. These hard disks and ZIP
In order to increase the capacity by reducing the track width and increasing the track density, the magnetic head must scan the narrow track accurately and reproduce the recording signal with a good S / N ratio. Tracking servo technology that detects the relative displacement between the head and the track and corrects the position of the magnetic head plays an important role.

In a hard disk or ZIP, a servo signal for tracking, an address information signal, a reproduction clock signal, and the like are recorded with high positional accuracy (preformat recording) in advance when a magnetic recording medium is manufactured. The area where these signals are recorded (servo area) is arranged discretely with respect to the disk surface, and the magnetic head reproduces these signals to check and correct the position of the head and to move along the track. Scanning accurately.

On the other hand, next-generation high-density recording systems include:
A recording method using evanescent light (also referred to as a near-field optical recording method or a near-field recording method) is regarded as promising. In this recording method, 100 gigabit / inch ²
It is expected that the above densification will be possible.

[0005] Evanescent light is generated when light is scattered and diffracted by a minute aperture having a wavelength smaller than the wavelength, and is non-propagating localized near the small aperture (in a region less than the wavelength of the light from the emission end of the small aperture). Light. In addition, solid immersion lenses (SI
Evanescent light can also be generated by condensing light on L (Solid Immersion Lens). By performing optical recording using this evanescent light, it is possible to form a recording mark smaller than a recording mark obtained by ordinary optical recording, thereby greatly increasing the surface recording density of information.

On the other hand, since the evanescent light exists only in a region smaller than the wavelength of light from the minute aperture serving as a recording head or the exit end of the SIL, the evanescent light generating means and its detector (head) are used as a recording medium. (Specifically, an area within several tens of nanometers) to perform recording and reproduction.

[0007]

However, the track width is becoming narrower as the density is further increased. In the conventional servo system, the magnetic head must scan the track accurately (servo following). Is not possible. In particular, at a recording density of 100 gigabits / inch ² or more, there is a high possibility that a problem will occur in servo following. If the servo following is reliably performed by increasing the ratio of the area of the servo area to the area of the disk, the recording area is reduced, and it is difficult to maintain a high recording capacity.

The optical disk employs a servo system for performing tracking using a land / groove structure tracking guide provided concentrically or spirally in the disk. There will be large irregularities. For this reason,
With the next-generation high-density recording method that requires the detector to be located very close to the recording medium, it is difficult to realize a stable head running state.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and it is an object of the present invention to provide a device capable of accurately performing tracking servo and locating a detector very close to a recording medium. Another object of the present invention is to provide an information recording medium that enables stable head running.

[0010]

In order to achieve the above object, an information recording medium according to the present invention has a disk-shaped smooth substrate and magnetically records information formed on the substrate. A magnetic recording layer, wherein the magnetic recording layer is magnetized concentrically or spirally with respect to the center of the disk in advance for tracking, and magnetization regions having different magnetization directions are alternately arranged in the radial direction. It is characterized by being magnetized.

According to the first aspect of the present invention, there is provided an information recording medium having a disk-shaped smooth substrate having no grooves (grooves) or pits (holes) for tracking servo or data recording, and a magnetic recording medium formed on the substrate. And a magnetic recording layer for selectively recording information. Since the magnetic recording layer is magnetized in advance so that magnetization regions having different magnetization directions are alternately arranged in the radial direction for tracking, tracking can be performed based on the difference in magnetization direction of the magnetization regions. Further, since the magnetic recording layer is magnetized concentrically or spirally with respect to the center of the disk in advance for tracking, tracking can be performed continuously, and accurate tracking servo can be performed. Further, since tracking can be performed based on the difference in the magnetization direction of the magnetization region, it is not necessary to form irregularities on a disk-shaped smooth substrate, and even when the detector is arranged very close to the recording medium, A stable head running state can be realized.

According to a second aspect of the present invention, in the information recording medium of the first aspect, the magnetization direction for tracking and the magnetization direction for recording and reproducing information are perpendicular to the disk surface. And By making the magnetization direction perpendicular to the disk surface, the magnetization regions alternately arranged in the radial direction and having different magnetization directions do not weaken each other, and the magnetic force of each magnetization region is stabilized. .

According to a third aspect of the present invention, in the information recording medium according to the first or second aspect, a protective layer is formed on the magnetic recording layer. According to a fourth aspect of the present invention, in the information recording medium of the third aspect, a lubricating film is formed on the protective layer. As a result, corrosion of the magnetic recording layer and abrasion due to pseudo contact or contact sliding between the head and the disk during recording and reproduction of information can be prevented, and running durability and corrosion resistance can be improved. According to a fifth aspect of the present invention, in the information recording medium according to the fourth aspect, the total thickness of the protective layer and the lubricating film is one.
It is characterized in that it is not more than 00 nm. Further, the substrate of the present invention does not use any grooves or pits. This makes it possible to perform recording and reproduction of information by bringing the surface of the magnetic recording layer and the head close to 100 nm or less in the entire data area, that is, in a state where the information recording medium and the head are stably contacting and sliding. Can be. Only when the surface of the magnetic recording layer and the magnetic head are close to 100 nm or less on average on the disk surface, high-density recording using evanescent light becomes possible.

According to a sixth aspect of the present invention, in the information recording medium according to any one of the first to fifth aspects, a reflection film is formed between the substrate and the magnetic recording layer. By forming a reflective film, in magneto-optical recording using ordinary light, not only the reflectivity is increased and the signal intensity is increased, but also when evanescent light is used, the evanescent light that is non-propagating light Since the light is converted into propagating light and reflected by the reflective film, the reflected light due to the propagating light is detected by the Faraday effect when detecting the reflected light of the near-field light on the surface of the magnetic recording layer using the magnetic Kerr effect. As a result, a so-called enhancement effect in which the S / N of the detection signal is improved can be obtained.

According to a seventh aspect of the present invention, in the information recording medium according to any one of the first to sixth aspects, the substrate is a flexible non-magnetic substrate. The use of a flexible non-magnetic substrate reduces the impact when the head comes into contact with the disk, and allows the head to be positioned on the recording medium as in the next-generation high-density recording method using a flying head. Also in the case where the head is arranged in the vicinity, the head and the disk are stably contacted and slid, so that the head can run stably. In addition, since a flexible non-magnetic substrate is used as a base material, it can be manufactured at low cost.

In the magnetic recording layer of the information recording medium, a discrete servo field may be magnetically recorded in advance together with a concentric or spiral tracking signal. By magnetically recording a servo field discretely in advance on the magnetic recording layer, the servo field is read out by using a magneto-optical effect such as the Kerr effect during recording or reproduction, and sector servo is performed. be able to. By using the tracking servo and the sector servo together, accurate tracking becomes possible, and at the same time, the access speed to a predetermined area is increased.

Further, the magnetization region of the magnetic recording layer of the information recording medium may be formed so as to meander at a constant frequency. As described above, by applying the so-called wobble, a clock signal and an address signal can be generated at the same time as detecting the tracking signal. In addition, as a tracking error detection method for performing tracking,
For example, it is possible to use a three-beam method that detects the rotation directions of the polarization planes of the reflected light by the two tracking beams and compares the two detected values.

The information recording medium may be used so that information is magnetically recorded only in a magnetized region magnetized in a predetermined magnetization direction. At this time, if the magnetization regions magnetized in a predetermined magnetization direction are formed wider than the magnetization regions magnetized in different magnetization directions, the format efficiency is improved. In addition, the format efficiency is improved even if the magnetization area magnetized in the predetermined magnetization direction is used so as to be recorded on a plurality of tracks.

The light used for recording and reproducing information on the information recording medium may be a general method in which laser light oscillated by a semiconductor laser or the like is condensed by an optical lens. Recording can also be performed while recording. As the laser light source, for example, a semiconductor laser having an oscillation wavelength in the range of 400 to 780 nm can be used. In order to increase the recording density, it is preferable to use a blue-violet semiconductor laser, a blue-violet SHG laser including an infrared semiconductor laser and a wavelength conversion element (SHG), and the like.
A blue-violet semiconductor laser of about 5 nm is particularly preferred.

[0020]

Embodiments of the present invention will be described below in detail with reference to the drawings. (First Embodiment) The magneto-optical disk 10 according to the first embodiment of the information recording medium of the present invention may be used in the form of a general hard disk drive, but has interchangeability. In order to enable contact recording, it is preferable to use a so-called flexible disk having a center hole formed in the center as shown in FIG. This flexible disk is stored in a cartridge 12 made of plastic or the like. The cartridge 12 usually has an access window (not shown) covered with a metal shutter (not shown).
Recording and reproduction on the magneto-optical disk 10 are performed through the access window.

As shown in FIG. 1 (C), the magneto-optical disk 10 has a magnetic recording layer 16 for magnetically recording information on a disk-shaped smooth support 14, and the magnetic recording layer 16 is deteriorated or worn. And a lubricating film 20 for improving running durability and corrosion resistance by applying a lubricant. The magnetic recording layer 16
Magnetization is performed in the direction perpendicular to the disk surface (preformat magnetization). When the surface opposite to the disk support 14 is used as a recording surface, the support is magnetized in the direction of the S pole and the recording surface is set to the N pole. Magnetized region 16A and the support side is N
Magnetized region 1 magnetized in the direction in which the recording surface side becomes the S pole at the pole
6B. These magnetized regions 16A and magnetized regions 16B are alternately arranged in the disk radial direction. FIG. 1B shows the magnetization state of the recording surface of the magnetic recording layer 16 in the region A of FIG. 1A.
As shown in (B), the magnetization regions 16A and 16A
Each of B is formed concentrically or spirally with respect to the center of the disk, and each constitutes a track. That is, the magnetization region 16A and the magnetization region 16B are used as a tracking guide and also as a recording region due to the difference in the magnetization direction. The magneto-optical disk 10 is irradiated with laser light from the side of the magnetic recording layer 16 to record and reproduce information.

As shown in FIG. 7, the magnetization region 16A
The magnetized region 16B may be formed so as to meander (provide a wobble) at a constant frequency. The meandering frequency of the wobble can be detected and used as a control signal for controlling the linear velocity. For example, by inserting wobbles of the same period from the inner circumference to the outer circumference, it is possible to control the linear velocity to be constant regardless of the radial position. Also,
By inserting wobbles so as to increase the period from the inner circumference to the outer circumference, it is possible to control the angular velocity to be constant. That is, a clock signal and an address signal can be generated by inserting a wobble.

The support 14 is made of a flexible resin film in order to avoid an impact at the time of contact with the head. Examples of such a resin film include aromatic polyimide, aromatic polyamide, aromatic polyamideimide, polyetheretherketone, polyethersulfone, polyetherimide, polysulfone, polyphenylenesulfide, polyethylene naphthalate, polyethylene terephthalate, polycarbonate, and triacetate. A resin film made of cellulose, fluororesin, or the like can be given.

Further, another resin film may be laminated on the support 14. By laminating another resin film, warpage and undulation due to the support itself can be reduced, and the scratch resistance of the magnetic recording layer can be significantly improved. Examples of the laminating method include roll lamination using a heat roller, lamination using a flat plate hot press, dry lamination in which an adhesive is applied to an adhesive surface for lamination, and lamination using an adhesive sheet formed in a sheet shape in advance. The type of the adhesive is not particularly limited, and a general hot-melt adhesive, a thermosetting adhesive, a UV-curable adhesive, an EB-curable adhesive, an adhesive sheet, an anaerobic adhesive, or the like can be used. Wear.

The thickness of the support 14 is 10 μm to 200 μm.
m, preferably 20 μm to 150 μm, more preferably 30 μm to 100 μm. If the thickness of the support 14 is too thin, the stability at the time of high-speed rotation is reduced, and the runout is increased. On the other hand, if the thickness of the support 14 is too large, the rigidity during rotation increases, making it difficult to avoid an impact at the time of contact, and causing the recording head to jump.

The surface of the support 14 is preferably as smooth as possible for recording by a magnetic head. The irregularities on the surface of the support 14 degrade the recording / reproducing characteristics. Specifically, when an undercoat layer described later is used, the surface roughness measured by an optical surface roughness meter is 5 nm or less, preferably 2 nm or less as an average center line roughness Ra, and a stylus roughness meter. Is less than 1 μm, preferably less than 0.1 μm. When the undercoat film is not used, the surface roughness measured by an optical surface roughness meter is 3 nm or less, preferably 1 nm or less in average center line roughness Ra, and the protrusion height measured by a stylus roughness meter. Is within 0.1 μm, preferably within 0.06 μm.

It is preferable to provide an undercoat layer on the surface of the support on which the magnetic recording layer 16 is provided for the purpose of improving flatness. Since the magnetic recording layer 16 is formed by sputtering or the like, the undercoat layer is preferably excellent in heat resistance. As a material of the undercoat layer, for example, a polyimide resin, a polyamideimide resin, a silicon resin, a fluorine resin, or the like is used. Can be. Thermosetting polyimide resin and thermosetting silicone resin are particularly preferable because of their high smoothing effect. The thickness of the undercoat layer is from 0.1 μm to 3.0 μm.
Is preferred. When another resin film is laminated on the support 14, an undercoat layer may be formed before the lamination processing, or an undercoat layer may be formed after the lamination processing.

As the thermosetting polyimide resin, for example, bisallylnadiimide “BAN” manufactured by Maruzen Petrochemical Co., Ltd.
A polyimide resin obtained by thermally polymerizing an imide monomer having two or more terminal unsaturated groups in the molecule as in "I" is preferably used. This imide monomer can be thermally polymerized at a relatively low temperature after being applied to the surface of the support in a monomer state. As described above, since the monomer as a raw material can be directly applied onto the support and cured, a general-purpose solvent can be used, the wraparound to unevenness is good, and the smoothing effect is high.

As the thermosetting silicone resin, a silicone resin polymerized by a sol-gel method using a silicon compound into which an organic group is introduced as a raw material is preferably used. This silicon resin has a structure in which a part of the bond of silicon dioxide is substituted with an organic group, and has a significantly higher heat resistance than silicon rubber, and is more flexible than a silicon dioxide film. Even if a resin film is formed on the support,
Cracks and peeling hardly occur. In addition, since a monomer as a raw material can be applied directly onto a support and cured, a general-purpose solvent can be used, the wraparound of unevenness is good, and the smoothing effect is high. Furthermore, the condensation polymerization reaction
Since the process proceeds from a relatively low temperature by the addition of a catalyst such as an acid or a chelating agent, the resin can be cured in a short time, and a resin film can be formed using a general-purpose coating device.

On the surface of the undercoat layer, for the purpose of reducing the real contact area with the head and improving the sliding characteristics,
It is preferable to provide minute projections. Further, by providing the minute projections, the handleability of the support is improved. As a method of forming the fine protrusions, a method of applying spherical silica particles, a method of applying an emulsion to form organic protrusions, and the like can be used.To secure the heat resistance of the undercoat layer, the spherical silica particles are coated. It is preferable to form minute projections.

The height of the fine projections is preferably 5 nm to 60 nm, more preferably 10 nm to 30 mm. If the height of the minute projections is too high, the recording / reproducing characteristics of the signal will be degraded due to the spacing loss between the recording / reproducing head and the medium, and if the minute projections are too low, the effect of improving the sliding characteristics will be reduced. The density of the fine projections is preferably 0.1 to 100 / μm ² ,
0 / μm ² is more preferable. If the density of the fine projections is too low, the effect of improving the sliding characteristics is reduced. If the density is too high, the number of high projections increases due to the increase in aggregated particles, and the recording / reproducing characteristics deteriorate.

Further, the fine projections can be fixed to the surface of the support by using a binder. As the binder, it is preferable to use a resin having sufficient heat resistance, and as the resin having heat resistance, it is particularly preferable to use a thermosetting polyimide resin or a thermosetting silicone resin.

It is preferable to provide a reflection film between the substrate 14 and the magnetic recording layer 16 as in a general magneto-optical disk. For the reflection film, a light-reflective substance having a high reflectance to laser light is used. Examples of such a light reflective material include Al, Al—Ti, Al—In, and Al—.
Metals such as Nb, Au, Ag, and Cu and metalloids can be mentioned. These substances may be used alone or in combination of two or more. Further, it may be used as an alloy. Among these, it is particularly preferable that the reflection film is made of a light-reflective material such as an Al alloy or an Ag alloy. Near-field light, which is non-propagating light, is converted into propagating light and reflected by the reflective film. Therefore, when detecting near-field light reflected on the magnetic recording layer surface using the magnetic Kerr effect, the propagating light Is reflected by the Faraday effect, and the S / N of the detection signal is improved (enhancement effect). A reflection film made of an Al alloy, an Ag alloy, or the like has a high reflectivity, so that a high enhancement effect can be obtained.

The above-mentioned reflective film can be formed by sputtering the above-mentioned light-reflective substance on the substrate 12 or by vacuum-depositing an electron beam. The thickness of the reflective film is 1
0 nm to 200 nm is preferred.

For the magnetic recording layer 16, magnetic recording materials such as various metal alloys generally used in magneto-optical recording media can be used. The magnetic recording material preferably has a perpendicular magnetic anisotropy, is excellent in magneto-optical properties, and has a Curie point of around 200 ° C. As such a magnetic recording material, a rare-earth transition metal amorphous material is exemplified. , Specifically TbF
Preferred are eCo, NdFeCo, GdFeCo, DyFeCo and the like. Further, it is more preferable to add Cr to these alloys in order to improve corrosion resistance. Among them, TbFe
Co-based alloys are particularly preferable because they have high perpendicular magnetic anisotropy and can stably record even very small recording marks. The magnetic recording layer 16 can be formed by, for example, a sputtering method, and the layer thickness of the magnetic recording layer 16 is preferably 10 nm to 50 nm.

It is preferable to provide a super-resolution layer on the magnetic recording layer 16 for the purpose of reducing recording marks and increasing recording density. The super-resolution layer generates super-resolution by utilizing the property change of the layer constituent material at the center of the laser beam spot. There are two types of typical super-resolution. Optical super-resolution can be used for both recording and reproduction of signals, and both action by heat (heat mode) and action by photons (photon mode) can be used. Examples of the optical super-resolution layer include an Ag-O thin film, an Sb thin film, and a photochromic polymer thin film. Magnetic super-resolution is used for reading out signals by light. For example, when a plurality of magnetic recording layers are stacked, it is possible to take out only the magnetic signals recorded in some of the magnetic recording layers by utilizing the difference in the magnetization change due to heat of each magnetic recording layer. .

For the purpose of enhancing the magneto-optical effect by utilizing light interference and improving the recording characteristics of the magnetic recording layer 16,
It is preferable to provide a dielectric protection film adjacent to the magnetic recording layer 16. For the dielectric protective film, a dielectric material generally used in magneto-optical recording can be used.
-N, Si-O, Al-N, Al-O, Zn-S, and the like. Among them, a material that suppresses the reaction between the metal material contained in the magnetic recording layer and oxygen and has high thermal conductivity is used. Preferably, Si-N or Al-N is particularly preferable. This dielectric protective film is formed by a sputtering method or a chemical vapor reaction method (C
VD method) or the like. The thickness of the dielectric protection film is preferably from 10 nm to 200 nm.

The protective layer 18 prevents corrosion of the metal material contained in the magnetic recording layer 16 and prevents abrasion due to simulated contact or contact sliding between the head and the disk, thereby improving running durability,
It is provided to improve corrosion resistance. In particular, when a rare earth metal is used for the magnetic recording layer 16, the protective layer 18 is indispensable because the rare earth transition metal is very easily corroded.

The protective layer 18 includes oxides such as silica, alumina, titania, zirconia, cobalt oxide and nickel oxide, nitrides such as titanium nitride, silicon nitride and boron nitride, silicon carbide, chromium carbide and boron carbide. Materials such as carbon such as carbide, graphite, and amorphous carbon can be used. The protective layer 18 is preferably a hard film having a hardness equal to or higher than that of the head material, hardly causing seizure during sliding, and maintaining its effect stably because of excellent sliding durability. . Further, those having few pinholes at the same time are more preferable because of their excellent corrosion resistance. As such a protective film, CVD
DLC (Diamond Like Carbon)
And a hard carbon film referred to as "a". Further, silicon nitride is preferable in consideration of optical characteristics.

A lubricating film 20 is provided on the protective layer 18 in order to improve running durability and corrosion resistance. A known hydrocarbon-based lubricant, a fluorine-based lubricant,
Lubricants such as extreme pressure additives are used.

Examples of the hydrocarbon-based lubricant include carboxylic acids such as stearic acid and oleic acid, esters such as butyl stearate, sulfonic acids such as octadecylsulfonic acid, and phosphoric esters such as monooctadecyl phosphate.
Alcohols such as stearyl alcohol and oleyl alcohol, carboxylic acid amides such as stearamide,
Examples include amines such as stearylamine.

Examples of the fluorine-based lubricant include lubricants in which part or all of the alkyl group of the hydrocarbon-based lubricant is replaced with a fluoroalkyl group or a perfluoropolyether group. Examples of the perfluoropolyether group include a perfluoromethylene oxide polymer, a perfluoroethylene oxide polymer, a perfluoro-n-propylene oxide polymer (CF ₂ CF ₂ CF ₂ O) n, and a perfluoroisopropylene oxide polymer (CF ( CF ₃ )
CF ₂ O) n, or a copolymer thereof. Specific examples include a perfluoromethylene-perfluoroethylene copolymer having a hydroxyl group at a molecular weight terminal (trade name “FOMBLIN Z-DOL”, manufactured by Audimont Co., Ltd.).

Examples of extreme pressure additives include phosphoric esters such as trilauryl phosphate, phosphites such as trilauryl phosphite, thiophosphites and thiophosphates such as trilauryl trithiophosphite, And sulfur-based extreme pressure agents such as dibenzyl disulfide.

The above-mentioned lubricants can be used alone or in combination of two or more. A solution obtained by dissolving the lubricant in an organic solvent is applied by a spin coating method, a wire bar coating method, a gravure coating method, a dip coating method or the like. It may be applied to the surface of the protective layer 18 or attached to the surface of the protective layer 18 by a vacuum evaporation method. The amount of the lubricant to be applied is 1 to 30 mg / m
² is preferable, and 2 to 20 mg / m ² is particularly preferable.

In order to further increase the corrosion resistance, it is preferable to use a rust inhibitor in combination. Examples of the rust inhibitor include nitrogen-containing heterocycles such as benzotriazole, benzimidazole, purine, and pyrimidine, and derivatives obtained by introducing an alkyl side chain or the like into the mother nucleus thereof, benzothiazole, 2-mercapton benzothiazole, and tetrazaindene. And nitrogen- and sulfur-containing heterocycles such as ring compounds and thiouracil compounds, and derivatives thereof. These rust inhibitors are
It may be mixed with a lubricant and applied on the protective film, or may be applied on the protective film before applying the lubricant, and the lubricant may be applied thereon. The coating amount of the rust inhibitor is 0.1 to 10 m
g / m ² is preferred, and 0.5 to 5 mg / m ² is particularly preferred.

The method of preformatting the magnetic recording layer 16 is not particularly limited. For example, the magnetized area may be written by a magnetic head, or the magnetized area may be formed by magnetic transfer. In order to form a magnetized region having a fine pattern in a short time, it is particularly preferable to form the magnetized region by magnetic transfer.

As shown in FIGS. 2A to 2C, magnetic transfer is performed from the master carrier 24 on which the magnetic layer 28 is formed.
Slave medium 2 having magnetic recording layer 16 before being magnetized
Second, a method of transferring magnetism to form a magnetized region of a predetermined pattern. The master carrier 24 is made of Co, F having a large magnetic flux density formed according to a transfer pattern on a substrate 26 made of a nonmagnetic material such as silicon or aluminum.
e and a convex magnetic layer 28 made of a ferromagnetic material such as e. A nonmagnetic metal material such as Cr or Ti is provided between the substrate 26 and the magnetic layer 28 as necessary. A conductive layer can be provided. The master carrier 24 can be manufactured using a stamper used for photofabrication or forming a substrate of an optical disc. For example,
A master carrier 24 can be obtained by forming a magnetic layer on a nickel substrate on which a predetermined pattern is formed by a stamper. Hereinafter, a method for forming a magnetized region by magnetic transfer will be specifically described.

First, as shown in FIG.
A DC magnetic field in the direction of arrow A is applied to the slave medium 22 on which the magnetic recording layer 16 before magnetization, the protective layer (not shown), and the lubricating film (not shown) are stacked. The magnetic recording layer 16 of the medium 22 is excited in the direction of arrow A (initial magnetization). Note that the magnetic recording layer 16 is initially magnetized and becomes the entire magnetized region 16A.

Next, as shown in FIG. 2B, the master carrier 24 is brought into close contact with the initially magnetized slave medium 22, and a DC magnetic field or an AC bias magnetic field in the direction of arrow B is applied as a transfer magnetic field. Then, the magnetic layer 28 is excited in the direction of arrow B. As a result, as shown in FIG. 2C, a magnetic field in the direction of arrow B is applied to the corresponding portion of the magnetic recording layer 16 from the portion where the slave medium 22 and the magnetic layer 28 are in contact, Is reversed, and the magnetization region 16A
A magnetized region 16B is formed therein. As a result, a precise preformat of the slave medium 22 is performed.

Next, recording and reproduction of information on the magneto-optical disk will be described. FIG. 5 shows a schematic configuration of a recording / reproducing apparatus which can be used for recording information on the magneto-optical disk and reproducing the recorded information.
1 shows a schematic configuration of a recording / reproducing head unit of the recording / reproducing apparatus.

As shown in FIGS. 5 and 6, the recording / reproducing apparatus includes a flying slider 32 which is attached to the tip of a swing arm 34 and floats as the magneto-optical disk 10 rotates. The flying slider 32 is attached to the lower surface of a gimbal 52 which is a thin leaf spring fixed to the tip of the suspension 38, and the suspension 3
8 is supported by the swing arm 34. The flying slider 32 has a flying surface (ABS: Air B).
An earing surface (40) is arranged above the recording surface of the magneto-optical disk 10 so as to face the recording surface of the magneto-optical disk 10, and the radius of the magneto-optical disk 10 is determined by the rotation of the swing arm 34 in the direction of arrow C. It is possible to move in the direction.

As shown in FIG. 6, the recording / reproducing head section
The flying type slider 32 is provided which floats with the rotation of the magneto-optical disk 10, and a rail pattern 42 for applying a positive pressure or a negative pressure is provided on a flying surface 40 thereof. The flying surface 40 of the flying slider 32 is provided with a minute opening 46 having a diameter smaller than the wavelength of light. An optical fiber 44 is provided in parallel with the suspension 38 to guide light from the outside to the minute opening 46. The emission end of the optical fiber 44 is disposed inside the flying slider 32, and a small aperture 4 is provided below the emission end of the optical fiber 44.
A condensing lens 47 for condensing light is disposed at 6. A magnetic head 50 having an exciting coil is provided on the air bearing surface 40. The magnetic head 50 includes a recording magnetic field control circuit 3 for controlling a magnetic field applied at the time of recording information.
6 is connected. In this device, the light guided by the optical fiber 44 is condensed by the condenser lens 47 into the minute opening 46 and emitted from the minute opening 46, thereby generating the evanescent light 54 near the minute opening 46. it can.

While rotating the magneto-optical disk 10,
When the flying type slider 32 is pressed against the magneto-optical disk 10, the magneto-optical disk 10 and the floating type slider 3 are pressed.
No. 2 stably contacts and slides with a very weak force. this street,
By providing a stable contact sliding state, the distance between the magnetic recording layer 16 of the magneto-optical disk 10 and the magnetic head 50 can be reduced to an average of 100 nm or less on the disk surface. For stable running of the head, the number of rotations of the disk is 1
000 rpm to 10,000 rpm is preferable, and
rpm to 7500 rpm are more preferable. Further, it is preferable that the surface runout of the disk is small, and it is more preferable that the surface runout be about 50 μm or less.

During information recording, the magnetic recording layer 16 is irradiated with evanescent light in the state of stable contact sliding, thereby heating the light-irradiated portion to the Curie temperature or higher, thereby reducing the coercive force of the heated portion. By sufficiently lowering the magnetization, the magnetization is easily reversed even with a relatively small magnetic field intensity. Then, a control signal is supplied from the recording magnetic field control circuit 36 to the magnetic head 50,
Information is magnetically recorded by applying a magnetic field corresponding to information to a region of the magnetic recording layer 16 where the magnetization is likely to be reversed (magnetic field modulation method). When information is recorded by the magnetic field modulation method, as shown in FIG.
A recording signal 58 having substantially the same magnitude as that of the portion heated by light is continuously recorded along each of the magnetized regions 16A and 16B.

When recording information on the magneto-optical disk 10, tracking servo is performed using the magnetic Kerr effect, as described below. As shown in FIG. 3A, when linearly polarized light is applied to the magnetized region 16A magnetized in a direction in which the support side is the S pole and the recording surface side is the N pole, the polarization plane of the reflected light is changed due to the magnetic Kerr effect. The incident light rotates by a predetermined angle θ (for example, clockwise) from the polarization plane of the incident light. On the other hand, as shown in FIG. 3B, when the same linearly polarized light is applied to the magnetized region 16B magnetized in the direction in which the support side is the N pole and the recording surface side is the S pole, the reflected light of the magnetized region 16B is generated by the magnetic Kerr effect. The polarization plane rotates by a predetermined angle −θ (for example, counterclockwise) from the polarization plane of the incident light.

Therefore, the evanescent light irradiated as the recording light is reflected by the magneto-optical disk 10,
The reflected light whose polarization plane has been rotated by a predetermined angle is detected from the reflected light through a polarizing plate or the like, and the relative displacement between the head and the track can be detected based on the intensity of the reflected light to perform tracking servo. . That is, the magnetized regions 16A and 16B provided concentrically or spirally serve as a tracking guide.

As a tracking error detection method, a tracking error detection method used in an optical disc, such as a push-pull method or a three-beam method for obtaining a tracking error signal using a two-part photodetector, can be used. Among them, the three-beam method that produces the highest quality servo error signal is particularly preferable.

The three-beam method will be described with reference to FIGS. The three-beam method is a method of performing tracking by splitting a laser beam generated from a laser light source into a main beam used for recording and reproducing a signal and two sub-beams for performing tracking. FIG.
As shown in FIG.
When 0 is directly above the recording track, the spot A and the spot B by the sub-beam overlap the tracks of the same magnetization direction to the same degree, the rotation angles of the polarization planes of the detected reflected light are substantially equal, and the circuit shown in FIG. The output of the tracking error signal at is zero. On the other hand, as shown in FIGS. 9B and 9C, when spots A and B have different degrees of overlap with tracks having the same magnetization direction,
The output of the tracking error signal in the circuit shown in FIG.
It can be plus or minus. Therefore, the deviation of the main beam from the recording track center can be detected from the output of the tracking error signal.

FIGS. 9 (D) and 9 (E) are views showing a modification of the beam arrangement. FIG. 9 (D) shows an example in which the arrangement of the main beam and the sub beam is changed. 9
(E) is an example in which the servo track read by the sub-beam is separated from the recording track.

At the time of reproducing the information, in a state where the contact sliding is stably performed similarly, as in the case of the tracking servo,
By irradiating evanescent light, which is linearly polarized light, to the magnetized region where the recording signal is recorded, and utilizing the magnetic Kerr effect, the rotation direction of the plane of polarization of the reflected light according to the difference in the magnetization direction is detected, thereby obtaining a magnetic field. Can be read out. Information is reproduced by using MR (M.sub.M) utilizing a magnetoresistance effect in which electric resistance changes according to the strength of a magnetic field.
Agneto Resistive) head, GMR
(Giant Magneto Resistive)
Head, TMR (Tunnel Magneto Re)
It may be performed by using a magnetic head such as an active head. Among them, highly sensitive GMR heads and TMR heads are particularly preferable. In addition, as described below, information is recorded on the magneto-optical disk 10 while performing tracking servo using the magnetic Kerr effect. (Second Embodiment) A magneto-optical disk according to a second embodiment of the information recording medium of the present invention is a so-called hard disk, except that it is configured as a hard disk. Since the configuration is the same as that of the magneto-optical disk according to the above, the description of the same portions will be omitted, and only different points will be described.

As the support 14, a substrate having relatively high hardness, such as an aluminum substrate, a glass substrate, a polycarbonate substrate, or a carbon substrate, is used. The thickness of the support 14 is
0.2 mm to 2.0 mm is preferred, and 0.3 mm to 1.
2 mm is more preferred. The surface of the support 14 is preferably as smooth as possible in order to perform recording with a magnetic head. Specifically, a burnishing process is performed at the time of manufacturing the hard disk substrate, and the surface roughness measured by an optical surface roughness meter is within 5 nm, preferably 2 nm or less in terms of average center line roughness Ra. The protrusion height measured in step 1
μm, preferably within 0.1 μm.

Recording and reproduction of information on and from the magneto-optical disk can be performed in the same manner as the magneto-optical disk according to the first embodiment.

As described above, in the magneto-optical disks according to the first and second embodiments, (1) magnetization regions having different magnetization directions are alternately arranged in the radial direction in advance for tracking the magnetic recording layer. Since it is magnetized in such a manner, tracking can be performed based on the difference in the magnetization direction of the magnetized region. As described above, since tracking can be performed based on the difference in the magnetization direction of the magnetization region, there is no need to form irregularities on the surface of the medium, and even when the detector is arranged very close to the recording medium, a stable head can be obtained. A running state can be realized. (2) Since the magnetic recording layer is magnetized concentrically or spirally with respect to the center of the disk in advance for tracking, tracking can be continuously performed, and accurate tracking servo can be performed. Na S /
N can record and reproduce signals. Further, since information is recorded in a magnetized region magnetized in advance for tracking, a decrease in recording capacity due to an increase in the area of the servo region can be prevented. In particular, since the magnetization direction is perpendicular to the disk surface, magnetized regions alternately arranged in the radial direction and having different magnetization directions do not weaken each other, and the magnetic force of each magnetized region is stabilized. Become (3) Since tracking can be performed based on the difference in the magnetization direction of the magnetization region, there is no need to form irregularities on a disk-shaped smooth substrate, and a next-generation high-density recording method using evanescent light can be used. As described above, even when the detector is arranged very close to the recording medium, a stable head running state can be realized. (4) Since the magneto-optical disk of the first embodiment is made of a support such as a flexible resin film as a base material, an impact at the time of contact with the magnetic head is avoided, and There is an advantage that the magnetic head can stably contact and slide with a very weak force. Furthermore, when a support such as a resin film having flexibility is used as a base material, a magneto-optical disk can be manufactured at low cost. (5) Since the magnetized region is formed by so-called magnetic transfer, a large amount of servo information can be copied at a time when a magnetic field is applied. Therefore, the magnetized region can be magnetized in a very short time. In addition, since it can be magnetized statically, accurate preformat recording is possible.

In the above-described first and second embodiments, an example in which recording and reproduction of information is performed by irradiating a laser beam from the magnetic recording layer side has been described. A configuration for recording and reproducing information may be employed. In this case, a material having a high transmittance to laser light of a predetermined wavelength used for recording and reproduction is used for the support.

Further, in the first and second embodiments, the example in which the magnetic recording layer is provided on one surface of the support has been described, but the magnetic recording layer may be provided on both surfaces of the support. Further, the magnetic recording layers may be provided on both sides of the disk by bonding together the supports each having the magnetic recording layer provided on one side with the support side facing inside.

In the above-described first and second embodiments, an example has been described in which recording and reproduction are performed using evanescent light. However, other laser light sources generally used in an optical information recording apparatus are used. Recording and playback can also be performed.

Also, an example in which an apparatus for generating evanescent light with a minute aperture is used has been described.
Recording and reproduction can also be performed using a device that condenses light on L and generates evanescent light. In this device,
As shown in FIG. 8, the SIL 60 is embedded inside the flying slider 32 such that its emission surface is exposed on the flying surface 40 of the flying slider 32. Above the SIL 60, a condenser lens 62 for condensing light from outside the flying slider 32 is disposed so as to focus on the exit surface of the SIL 60 exposed on the flying surface 40. Condensing lens 62
Condenses light from outside of the flying slider 32 by the SI
The evanescent light 54 is generated near the focal point by focusing on the exit surface of L60. The same components as those of the apparatus shown in FIG. 6 are denoted by the same reference numerals, and description thereof will be omitted.

In the above-described first and second embodiments, an example in which information is recorded by the magnetic field modulation method has been described. However, as shown in FIG. 4, either one of the magnetization region 16A and the magnetization region 16B is recorded. Alternatively, a magnetic field opposite to the magnetization direction may be applied to reverse the magnetization only in the portion irradiated with the laser beam 30 to magnetically record information (optical modulation method). At this time, since the intensity distribution of the laser beam has a Gaussian distribution, the recording signal 31 is formed at the center of the spot having a high intensity. Therefore, a recording signal 31 smaller than the spot of the laser beam 30 is recorded according to the recording signal. As shown in FIG. 4, for example, recording is performed only in the S-type magnetization region 16B, and the N-type magnetization region 16A is used for tracking. The information may be recorded in a part of the magnetized region by dividing the information into regions.

In the above-described first and second embodiments, an example has been described in which the magnetic recording layer is magnetized concentrically or spirally with respect to the center of the disk in advance for tracking and tracking is continuously performed. The magnetic recording layer can be magnetized concentrically or spirally with respect to the center of the disk in advance for tracking, and a servo field can be magnetically recorded discretely in advance on the magnetic recording layer.

FIGS. 12A and 12B show an example in which servo fields are arranged discretely. In this servo field, address information and track information are recorded. In addition to the servo field, a concentric servo band for continuously performing tracking is written.

Thus, the servo field can be read out by utilizing the magneto-optical effect such as the Kerr effect, and sector servo can be performed. By using the tracking servo and the sector servo together, accurate tracking becomes possible, and at the same time, the access speed to a predetermined area is increased.

In the first and second embodiments, N
Although the magnetized region 16A and the magnetized region 16B have substantially the same width, when recording is performed only on the magnetized region 16A and the magnetized region 16B is used for tracking, FIG. As shown in (A), the width of the tracking magnetization region 16B is preferably smaller than the width of the recording magnetization region 16A. The format efficiency is improved by making the width of the recording magnetization region 16A wider. For example, the width of the tracking magnetization region 16B is set to 0.1 μm.
m, and the width of the recording magnetization region 16A can be about 0.2 μm. Also, as shown in FIG.
Further widen the magnetized region 16A for recording may be carried out as the underlying plurality of tracks 16A ₁ ~16A ₅ to the magnetization region 16A for recording, a write from a so-called multi-head having a plurality of magnetic heads .

[0073]

According to the information recording medium of the present invention, the tracking servo can be accurately performed, and the head can run stably even when the detector is arranged very close to the recording medium. To play.

[Brief description of the drawings]

FIG. 1A is a plan view showing a schematic configuration of a magneto-optical disk according to the present embodiment, and FIG. 1B is a portion showing a magnetization state of a surface of a magnetic recording layer in a region A of FIG. It is an enlarged view, (C) is sectional drawing on the AA line of (B).

FIGS. 2A to 2C are cross-sectional views showing steps of magnetic transfer.

FIGS. 3A and 3B are explanatory diagrams illustrating the principle of reading a tracking signal. FIG.

FIG. 4 is a plan view showing a recording pattern when information is recorded by a light modulation method.

FIG. 5 is a plan view showing a schematic configuration of a recording / reproducing apparatus used for recording and reproducing information on and from a magneto-optical disk according to the present embodiment.

6 is a sectional view taken along the optical axis showing a schematic configuration of a recording / reproducing head unit of the recording / reproducing apparatus shown in FIG.

FIG. 7 is a plan view showing a recording pattern when information is recorded by a magnetic field modulation method.

FIG. 8 is a plan view showing another configuration example of the recording / reproducing apparatus used for recording and reproducing information on and from the magneto-optical disk according to the present embodiment.

FIGS. 9A to 9E are diagrams for explaining the principle of tracking by the three-beam method.

FIG. 10 is a diagram illustrating an input / output relationship of a circuit that outputs a tracking error signal.

FIGS. 11A and 11B are diagrams showing a modified example in which servo information is discretely recorded on a magnetic recording layer.

FIG. 12A is a partially enlarged plan view showing a magnetization state (light modulation recording) on the surface of a magnetic recording layer when the width of a recording magnetization region is made wider than the width of a tracking magnetization region; (B) is a partial enlarged plan view showing a magnetization state on the surface of the magnetic recording layer when a plurality of tracks are present in a recording magnetization region.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Magneto-optical disk 12 Cartridge 14 Support 16 Magnetic recording layer 18 Protective layer 20 Lubricating film 16A Magnetized area 16B Magnetized area 18 Protective layer 20 Lubricating film 22 Slave medium 24 Master carrier 32 Floating slider 50 Magnetic head

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) G11B 5/72 G11B 5/72 13/00 13/00 (72) Inventor Yumi Usami 2-chome, Ogimachi, Odawara-shi, Kanagawa No. 1 Fuji Photo Film Co., Ltd. (72) Inventor Shin Nagao 2-1-1, Ogimachi, Odawara-shi, Kanagawa Prefecture 5D075 EE03 FF11 FG04

Claims (7)

[Claims] 1. A disk-shaped smooth substrate, and a magnetic recording layer formed on the substrate and for magnetically recording information, wherein the magnetic recording layer is positioned in advance with respect to the center of the disk for tracking. An information recording medium magnetized concentrically or spirally and magnetized such that magnetized regions having different magnetization directions are alternately arranged in the radial direction. 2. The information recording medium according to claim 1, wherein a magnetization direction for tracking and a magnetization direction for recording / reproducing information are perpendicular to a disk surface. 3. The information recording medium according to claim 1, wherein a protective layer is formed on the magnetic recording layer. 4. The information recording medium according to claim 3, wherein a lubricating film is formed on said protective layer. 5. The combined thickness of the protective layer and the lubricating film is 1
5. The information recording medium according to claim 4, which has a thickness of 00 nm or less. 6. The information recording medium according to claim 1, wherein a reflection film is formed between said substrate and said magnetic recording layer. 7. The information recording medium according to claim 1, wherein said substrate is a flexible non-magnetic substrate.