JP2005243086A - Magnetic recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide magnetic recording medium which can be use as a removable magnetic recording medium, such as a magnetic tape and a flexible disk having excellent magnetic characteristics, recording characteristics and durability. <P>SOLUTION: This magnetic recording medium has a magnetic layer of a ferromagnetic metal alloy containing at least Co, Pt, Cr, and B at least on a flexible polymer base. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a magnetic recording medium using a flexible polymer support such as a magnetic tape and a flexible disk, and more particularly to a high capacity magnetic tape and a high capacity flexible disk capable of high density magnetic recording.

  In recent years, a large-capacity hard disk is mounted on a personal computer in response to handling of large-capacity image information due to the spread of the Internet and the like. Various types of removable recording media are used to back up a large amount of information stored in a hard disk or use it on another computer. A flexible magnetic recording medium such as a magnetic tape or a flexible disk has many features such as a short time required for recording and reading information, as well as a hard disk, and a small device necessary for recording and reading information. have. For this reason, magnetic tapes and flexible disks are used as typical removable recording media for computer backup and storage of large amounts of data. A magnetic recording medium capable of storing a large amount of data with a small number of magnetic tapes and flexible disks is demanded, and further improvement in recording density is demanded.

  Magnetic recording media using a flexible polymer support such as a magnetic tape and a flexible disk were coated on a substrate with magnetic fine particles containing a metal such as iron, chromium, cobalt dispersed in a polymer binder. An evaporation type magnetic recording medium in which a coating type magnetic recording medium and a cobalt-based alloy are formed by evaporation in a vacuum is used. Compared with the coating type magnetic recording medium, the vapor deposition type magnetic recording medium has the feature that higher density recording is possible, but the magnetic property of the flexible magnetic recording medium in which the metal thin film is formed by the vapor deposition method. The layer is noisy compared to a ferromagnetic metal thin film formed by sputtering of a cobalt-based alloy used in hard disks, and sufficient electromagnetic conversion characteristics are obtained in a high-density recording head using a magnetoresistive element. This is not suitable for high recording density characteristics. As for the magnetic recording medium used for the hard disk device, for example, Patent Documents 1 to 3 describe a magnetic recording medium having a Co alloy layer formed by sputtering on a nonmagnetic material such as a Ni-P plated aluminum substrate. doing.

Thus, although several attempts have been reported to produce a ferromagnetic metal thin film tape by sputtering like a hard disk, it has not been put into practical use. This is because in the manufacture of hard disks, the substrate is heated to about 200 ° C. during sputtering, but if a similar manufacturing method is applied to magnetic tapes and flexible disks, it is generally used as a support for magnetic tapes and flexible disks. This is because such polyethylene terephthalate or polyethylene naphthalate is insufficient in heat resistance and deforms. Even if an aromatic polyamide film with excellent heat resistance is used, dimensional changes such as thermal expansion, thermal contraction, and humidity expansion of the film occur during the manufacturing process, making it difficult to produce a magnetic tape with little deformation. Met. The flexible disk also has the same problem because a magnetic layer is formed using a belt-like support similar to that of a magnetic tape and then punched into a predetermined shape to form a disk.
Patent Document 4 discloses a magnetic recording medium having a magnetic layer composed of a cobalt-containing ferromagnetic metal alloy formed by sputtering on a flexible polymer support and a nonmagnetic metal oxide.

Magnetic recording media such as magnetic tapes and flexible disks enable high-density recording as described above, and in addition to being excellent in magnetic characteristics and recording characteristics, are not required for hard disks, but are in contact with magnetic heads. It is desired to have durability below.

JP-A-4-221418 JP-A-5-182171 JP 2001-93131 A JP 2003-162805 A

  An object of the present invention is to provide a magnetic recording medium such as a magnetic tape and a flexible disk, which is capable of high-density recording and has excellent magnetic characteristics, recording characteristics, and durability.

The problems of the present invention have been solved by a magnetic recording medium having the following configuration.
(1) A magnetic recording medium comprising a magnetic layer made of a ferromagnetic metal alloy containing at least Co, Pt, Cr and B on at least one surface of a flexible polymer support.

As a preferred embodiment, the following configuration is exemplified.
(2) The magnetic recording medium according to (1) above, wherein the content of B in the ferromagnetic metal alloy is 10 to 20 atomic%.

  The magnetic recording medium of the present invention having a magnetic layer made of a ferromagnetic metal thin film containing Co, Pt, Cr and B not only enables a magnetic recording medium excellent in magnetic properties, recordability and durability, The magnetic layer is a layer that can be formed by sputtering on a flexible polymer support at a low temperature such as room temperature, and can be applied to a coating-type magnetic recording medium or a deposition-type magnetic recording medium in which the magnetic layer is formed by coating or vapor deposition. In comparison, a removable magnetic recording medium capable of high-density recording can be provided.

  The magnetic recording medium of the present invention has a magnetic layer made of a ferromagnetic metal alloy containing at least Co, Pt, Cr and B on at least one surface of a flexible polymer support.

[Flexible polymer support]
For example, a synthetic resin film is used as the flexible polymer support of the magnetic recording medium of the present invention. Specifically, aromatic polyimide, aromatic polyamide, aromatic polyamideimide, polyether ketone, polyethersulfone, polyetherimide, polysulfone, polyphenylene sulfide, polyethylene naphthalate, polyethylene terephthalate, polycarbonate, triacetate cellulose, fluororesin, etc. The synthetic resin film which consists of these is mentioned. In the present invention, since good recording characteristics can be achieved without heating the substrate, polyethylene terephthalate or polyethylene naphthalate, which has good surface properties and mechanical strength and is easily available, is particularly preferred.

The surface of the flexible polymer support is preferably as smooth as possible in order to perform recording with a magnetic head. Unevenness on the surface of the support significantly reduces the signal recording / reproducing characteristics. Specifically, in the case of using an undercoat layer to be described later, the surface roughness measured by a light interference type surface roughness meter is 5 nm or less, preferably 2 nm or less, as a center plane average roughness (SRa), stylus type The height of the protrusion measured with a roughness meter is within 1 μm, preferably within 0.1 μm. When the undercoat layer is not used, the surface roughness measured with an optical interference type surface roughness meter is within 3 nm, preferably within 1 nm, with a center surface average roughness (SRa), measured with a stylus roughness meter. The projected height is within 0.1 μm, preferably within 0.06 μm.

[Magnetic layer]
The magnetic layer of the magnetic recording medium of the present invention is made of a ferromagnetic metal alloy containing at least Co, Pt, Cr, and B.
The ferromagnetic metal alloy may contain elements other than Co, Pt, Cr and B, but the total amount of Co, Pt, Cr and B in the ferromagnetic metal alloy is 90 to 100 atomic%. It is preferable that it is 95-100 atomic%.
In addition, it is preferable that the content rate of B is 10-20 atomic%.
As a preferable alloy composition of the ferromagnetic metal alloy, an alloy selected from the range of Co of 65 to 80 atomic%, Pt of 5 to 20 atomic%, Cr of 10 to 20 atomic%, and B of 10 to 20 atomic%. Composition.

  Furthermore, when a nonmagnetic element such as Ta or Si is added to this, it may be added so as to substitute Pt or Cr in the range of 10 atomic% or less in the ferromagnetic metal alloy. The greater the Co content, the greater the magnetization and the higher the signal reproduction output, but the noise also increases at the same time. On the other hand, as the content of nonmagnetic elements such as Cr and Pt increases, the magnetization decreases, but the coercive force increases, so that the signal reproduction output decreases, but the noise decreases. Therefore, it is preferable to adjust the blending ratio of these elements according to the magnetic head to be used and the equipment to be used. Further, when the Pt content is increased and the Cr content is decreased, the magnetic anisotropy constant Ku is increased and stable against thermal fluctuation, but noise tends to increase. Conversely, when the Pt content is decreased and the Cr content is increased, separation of magnetic particles is promoted and noise is reduced, but the magnetic anisotropy constant Ku is lowered and unstable against thermal fluctuation. . In the ferromagnetic metal alloy containing at least Co, Pt, Cr, and B, elements such as Si, Ta, and C may be further added to these elements.

  When the B content is low, the separation of the magnetic material is not promoted and the crystal of the magnetic material becomes large. In addition, since magnetic exchange coupling becomes strong, noise increases remarkably, so that the SNR (signal / noise ratio) tends to decrease. On the other hand, when the B content is high, the amount of magnetization decreases and the signal output decreases, so the SNR tends to decrease.

Other, as an element which can contain, can also contain an O or N. Further, rare gases may be contained.

  The thickness of the magnetic layer made of the ferromagnetic metal alloy is preferably in the range of 5 nm to 40 nm, more preferably 8 nm to 30 nm, from the viewpoint of low noise and high output.

  The anisotropy of magnetization (the direction of the easy axis of magnetization) can be adjusted by conditions such as argon pressure during the formation of the magnetic film, but is preferably determined by an underlayer or seed layer described later. When the underlayer is not used or when an amorphous material is used, the magnetic layer is easily oriented vertically. When Ru or Cr alloy is used as the underlayer, the surface depends on the film formation conditions and the seed layer material. Either the inner orientation or the vertical orientation can be oriented.

  The magnetic layer in the magnetic recording medium of the present invention may be a so-called perpendicular magnetic recording film having an easy magnetization axis in the direction perpendicular to the magnetic layer surface, or an in-plane magnetic recording film having an easy magnetization axis in the horizontal direction. The direction of the easy axis of magnetization can be controlled by the material or crystal structure of the underlayer or seed layer, which will be described later, and the composition and deposition conditions of the magnetic film.

The magnetic layer of the present invention is formed of a ferromagnetic metal alloy containing at least Co, Pt, Cr, and B. Since B forms a grain boundary of magnetic particles, the particle size of the magnetic material is reduced, And it becomes magnetically isolated. A magnetic film having a so-called granular structure is formed. Therefore, a high coercive force can be achieved, and a magnetic recording medium with low noise can be obtained. Further, since such a magnetic film structure can be formed without increasing the substrate temperature, it can be formed without thermally deforming the flexible polymer support of the present invention.

[Method for producing magnetic recording medium]
In the magnetic recording medium of the present invention, a magnetic layer made of a ferromagnetic metal alloy containing at least Co, Pt, Cr and B is formed on at least one surface of the flexible polymer support.
As a method for forming a magnetic layer made of a ferromagnetic metal alloy containing at least Co, Pt, Cr, and B, a sputtering method can be used. Since a sputtering method can easily form a good-quality thin film, Suitable for the invention. As the sputtering method, either a DC sputtering method or an RF sputtering method can be used.
For example, the methods described in JP-A-4-221418, JP-A-5-182171, JP-A-2001-93131 and the like can be used.

  The film quality may be controlled by applying a bias to the substrate during sputtering. In the present invention, since a flexible polymer support is used as the support, a DC pulse sputtering method that has an effect of suppressing an increase in the arc and the support temperature due to charge-up is most preferable. Moreover, it is preferable to use the web sputtering apparatus which forms a film continuously on a continuous film as a sputtering apparatus. Argon can be used as the gas used in the atmosphere during sputtering, but other rare gases may be used. The substrate at the time of sputtering does not need to be heated, and conversely, if the substrate is sputtered in a physically floating state, heat at the time of sputtering is applied to the support, which may cause deterioration of magnetic characteristics and deformation of the support.

  In the present invention, since a flexible polymer support is used as the support, the temperature of the flexible polymer support is preferably kept at 100 ° C. or less, more preferably 0 to 50 ° C. It is desirable to prevent deformation of the support. For this reason, when performing sputtering, it is preferable that the flexible polymer support is brought into close contact with the cooling can and the support is actively cooled as described later. In addition, the temperature of the flexible polymer support during sputtering can be adjusted by adjusting the temperature of the film forming can as described later.

  In particular, in order to form a magnetic layer made of a ferromagnetic metal alloy containing at least Co, Pt, Cr, and B by sputtering as in the present invention, a plurality of different layers such as Co—Pt—Cr and B are used. Although it is possible to use these co-sputtering methods with a target, if a ferromagnetic metal alloy alloy target that matches the composition ratio of the ferromagnetic metal alloy to be formed is used, a magnetic layer with a uniform composition can be obtained. Can be formed.

[Form of magnetic recording medium]
As a more specific form of the magnetic recording medium of the present invention, for example, a magnetic tape and a flexible disk can be mentioned. Hereinafter, the case of a magnetic tape and a flexible disk will be described.

[A. Magnetic tape〕
FIG. 1A is a diagram for explaining an embodiment in which the magnetic recording medium is a magnetic tape, and is a cross-sectional view showing a part thereof. The magnetic tape 11 is obtained by forming a magnetic layer 15 on a belt-like flexible polymer support 12, and the magnetic layer 15 is made of a ferromagnetic metal alloy containing at least Co, Pt, Cr, and B. It is configured. A protective layer 16 is formed on the magnetic layer 15 to prevent the magnetic layer from being deteriorated due to oxidation or the like and to be protected from wear due to contact with the head or the sliding member. A lubricating layer 17 is provided on the protective layer 16 for the purpose of improving running durability and corrosion resistance.

  In addition to the structure shown in FIG. 1A, the surface property of the flexible polymer support 12 is adjusted to the surface on the flexible polymer support 12 as shown in FIG. In addition, an undercoat layer 13 is provided to prevent the gas generated from the flexible polymer support 12 from reaching the magnetic layer 15. Further, an underlayer 14 is provided for controlling the crystal orientation of the ferromagnetic metal formed in the magnetic layer 15 to improve the recording characteristics. In the magnetic tape shown in FIG. 1B, the crystal orientation of the ferromagnetic metal is improved by the underlayer, and a magnetic tape having better characteristics than that shown in FIG. 1A is obtained. The magnetic tape can be used in the form of an open reel or one stored in a cartridge.

(Flexible support polymer support)
When the magnetic recording medium is a magnetic tape, the flexible support used is as described above for the magnetic recording medium.

  The thickness of the flexible polymer support is preferably 3 to 20 μm, more preferably 4 to 12 μm. The thickness of the flexible polymer support is preferably 3 μm or more in terms of sufficient strength, cutting and edge breakage prevention, and the magnetic tape length, volume recording density, and moderate rigidity that can be wound up per magnetic tape roll. The contact with the magnetic head, that is, in terms of followability, is preferably 20 μm or less.

(Undercoat layer)
An undercoat layer is preferably provided on the surface of the flexible polymer support for the purpose of improving planarity and gas barrier properties. Since the magnetic layer is formed by sputtering or the like, the undercoat layer is preferably excellent in heat resistance. Examples of the material of the undercoat layer include polyimide resin, polyamideimide resin, silicone resin, fluorine resin, ultraviolet curable resin, and electron beam curing. Resin or the like can be used. Thermosetting silicone resins and electrosetting resins are particularly preferred because of their high smoothing effect. The thickness of the undercoat layer is preferably 0.1 μm to 3.0 μm.

  As the thermosetting silicone resin, a silicone resin polymerized by a sol-gel method using a silicon compound having an organic group introduced as a raw material is preferably used. This silicone resin has a structure in which a part of the silicon dioxide bond is substituted with an organic group, and is greatly superior in heat resistance to silicone rubber and more flexible than a silicon dioxide film. Even if a resin film is formed on the polymer support, cracks and peeling are unlikely to occur. Moreover, the monomer used as a raw material can be directly applied on a flexible polymer support and cured. In addition, since the monomer can be dissolved and applied in a general organic solvent, it is easy to wrap around unevenness and has a high smoothing effect.

  Furthermore, since the condensation polymerization reaction proceeds from a relatively low temperature by adding a catalyst such as an acid or a chelating agent, it can be cured in a short time, and a resin film can be formed using a general-purpose coating apparatus. Thermosetting silicone resins are excellent in gas barrier properties. For this reason, the gas shielding property which shields the gas which generate | occur | produces from a flexible polymer support body at the time of magnetic layer or base layer formation, and obstructs the crystallinity and orientation of a magnetic layer or base layer is high, and is especially suitable.

  The surface of the undercoat layer is preferably provided with minute protrusions (textures) for the purpose of reducing the true contact area between the sliding member such as the magnetic head and the guide pole and the magnetic tape and improving the sliding characteristics. . In addition, by providing the fine protrusions, the handleability of the flexible polymer support is improved. As a method for forming the fine protrusions, a method of applying spherical silica particles, a method of forming an organic protrusion by applying an emulsion, and the like can be used. However, in order to ensure the heat resistance of the undercoat layer, the spherical silica particles are applied. Thus, it is preferable to form minute protrusions.

The height of the fine protrusion is preferably 5 nm to 60 nm, and more preferably 10 nm to 30 nm. 5 nm or more is preferable from the viewpoint of improving the sliding characteristics, and 60 nm or less is preferable from the viewpoint of preventing deterioration of recording / reproducing characteristics of signals due to spacing loss between the recording / reproducing head and the magnetic recording medium. The density of minute projections is preferably from 0.1 to 100 pieces / [mu] m ^2, more preferably 1 to 10 / [mu] m ^2. 0.1 or in terms of the effect of improving the sliding properties / [mu] m ² or more, to prevent an increase in high projections due to the increase of the agglomerated particles, in that it can prevent the deterioration of the recording and reproducing characteristics are 100 / [mu] m ² or less preferable. In addition, the fine protrusions can be fixed to the support surface using a binder. It is preferable to use a resin having sufficient heat resistance for the binder, and as the resin having heat resistance, a solvent-soluble polyimide resin, a thermosetting polyimide resin, or a thermosetting silicone resin should be used. Is particularly preferred.

(Underlayer)
It is preferable to provide an underlayer below the magnetic layer. Examples of the underlayer include Cr, an alloy of Cr and a metal selected from Ti, Si, W, Ta, Zr, Mo, Nb, and the like, Ru, Ti, and C. These substances may be used alone or in combination of two or more. By using such an underlayer, the orientation of the magnetic layer can be improved, so that the recording characteristics are improved. The thickness of the underlayer is preferably 10 nm to 200 nm, particularly preferably 20 nm to 100 nm. It is particularly preferable that the magnetic layer is formed in a columnar shape by the underlayer. By forming the columnar shape, the separation structure between the ferromagnetic metals is stabilized, high coercive force is obtained, high output is possible, and the dispersion of the ferromagnetic metals is uniform, and the magnetic recording medium is low noise. Is obtained.

(Seed layer)
Further, a seed layer or a gas barrier layer can be provided between the underlayer and the flexible polymer support in order to improve the crystallinity of the underlayer. Ta, Ta-Si, Ni-P, Ni-Al, C, or the like can be used for the seed layer. In order to orient the magnetic layer in the in-plane direction, a seed layer is not used, or an amorphous seed layer is used, and a Ru or Cr alloy may be laminated thereon. On the other hand, in order to vertically align the magnetic layer, a Ru underlayer or Cr underlayer may be used in combination with a seed layer such as a Ni alloy such as Ni—Al, a noble metal such as Au, or an alloy thereof.

(Soft magnetic layer)
When the magnetization anisotropy is perpendicular, a soft magnetic layer may be provided between the magnetic layer and the flexible polymer support. By providing the soft magnetic layer, the recording characteristics when a perpendicular recording head such as a single pole head is used can be improved. As the soft magnetic material, general soft magnetic materials such as permalloy and sendust can be used. The film thickness is preferably 30 to 500 nm.

(Protective layer)
A protective layer is provided on the magnetic layer. The protective layer is provided to prevent corrosion of the metal material contained in the magnetic layer, to prevent wear due to pseudo contact or contact sliding between the magnetic head and the magnetic tape, and to improve running durability and corrosion resistance. The protective layer includes silica, alumina, titania, zirconia, oxides such as cobalt oxide and nickel oxide, nitrides such as titanium nitride, silicon nitride and boron nitride, carbides such as silicon carbide, chromium carbide and boron carbide, graphite, Materials such as carbon such as amorphous carbon can be used.

As the protective layer, a hard film having a hardness equal to or higher than that of the magnetic head material, which is less likely to cause seizure during sliding and has a stable effect, is preferable because of excellent sliding durability. . At the same time, those having few pinholes are more preferred because they have excellent corrosion resistance. As such a protective film, a hard carbon film called diamond-like carbon (DLC) produced by a CVD method can be given. The protective layer can be formed by laminating two or more types of thin films having different properties. For example, by providing a hard carbon protective film for improving sliding characteristics on the surface side and providing a nitride protective film such as silicon nitride for improving corrosion resistance on the magnetic recording layer side, corrosion resistance and durability can be achieved. It is possible to achieve a high level of compatibility.

(Lubrication layer)
On the protective layer, a lubricating layer is provided in order to improve running durability and corrosion resistance. A lubricant such as a hydrocarbon-based lubricant, a fluorine-based lubricant, and an extreme pressure additive is used for the lubricant layer. Hydrocarbon lubricants include carboxylic acids such as stearic acid and oleic acid, esters such as butyl stearate, sulfonic acids such as octadecyl sulfonic acid, phosphate esters such as monooctadecyl phosphate, stearyl alcohol, oleyl alcohol And the like, carboxylic acid amides such as stearamide, and amines such as stearylamine.

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

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

The above lubricants can be used alone or in combination. A solution obtained by dissolving a lubricant in an organic solvent can be used for the surface of the protective layer by spin coating, wire bar coating, gravure coating, dip coating, etc. What is necessary is just to apply | coat to a protective layer surface by a vacuum evaporation method. The coating amount of the lubricant is preferably ^{1~30mg / m 2, 2~20mg / m} 2 is particularly preferred.

(Rust inhibitor)
Moreover, in order to further improve corrosion resistance, it is preferable to use a rust inhibitor together. Examples of rust inhibitors include nitrogen-containing heterocycles such as benzotriazole, benzimidazole, purine, and pyrimidine, and derivatives in which an alkyl side chain is introduced into the mother nucleus, benzothiazole, 2-mercaptobenzothiazole, tetrazaindene ring And nitrogen- and sulfur-containing heterocycles such as thiouracil compounds and derivatives thereof. These rust preventives may be mixed with a lubricant and applied on the protective layer, or may be applied on the protective layer before applying the lubricant, and the lubricant may be applied thereon. As an application quantity of a rust preventive agent, 0.1-10 mg / m < ² > is preferable and 0.5-5 mg / m < ² > is especially preferable.

(Back coat layer)
It is preferable to provide a backcoat layer on the surface of the flexible polymer support opposite to the surface on which the magnetic layer is formed. The backcoat layer has a lubricating effect of preventing wear on the back surface of the magnetic recording medium when the magnetic recording medium and the sliding member slide. Also, by adding the lubricant and rust preventive agent used in the lubricating layer to the back coat layer, the lubricant and rust preventive agent are supplied from the back coat layer side to the magnetic layer side. It becomes possible to hold. Further, the corrosion resistance of the magnetic layer can be further improved by adjusting the pH of the backcoat layer itself. The backcoat layer is made of a non-magnetic powder such as carbon black, calcium carbonate, or alumina, a resin binder such as polyvinyl chloride or polyurethane, and a solution in which a lubricant or curing agent is dispersed in an organic solvent using the gravure method or wire bar method. It can be produced by applying and drying. As a method of applying a rust preventive or lubricant to the back coat layer, it may be dissolved in the above solution or applied to the produced back coat layer.

[B. Flexible disk)
FIG. 2A is a diagram illustrating a case where the magnetic recording medium is a flexible disk. The flexible disk 21 has a magnetic layer 25 formed on both surfaces of a flexible polymer support 22, and the magnetic layer 25 is composed of a ferromagnetic metal alloy containing at least Co, Pt, Cr, and B. Has been. A protective layer 26 is formed on the magnetic layer 25 to prevent the magnetic layer from being deteriorated due to oxidation or the like, and to protect it from abrasion due to contact with the head or the sliding member. A lubricating layer 27 is provided on the protective layer 26 for the purpose of improving running durability, corrosion resistance, and the like. Further, an engaging means 30 for mounting on the flexible disk drive is mounted at the center.

In addition, the magnetic recording medium shown in FIG. 2B adjusts the surface property of the flexible polymer support 22 on the surface of the flexible polymer support 22, and the flexible polymer support. An undercoat layer 23 is provided in order to prevent the gas generated from 22 from reaching the magnetic layer 25. Further, an underlayer 24 is provided for controlling the crystal orientation of the ferromagnetic metal formed in the magnetic layer 25 to enhance the recording characteristics. Further, as in FIG. 2A, the protective layer 26, the lubricating layer 27, and the engaging means 30 are provided.
Compared to the structure shown in FIG. 2A, the material shown in FIG. 2B is superior in crystal orientation of the ferromagnetic metal and has excellent magnetic properties by the underlayer.

(Flexible polymer support)
Next, a case where the magnetic recording medium is a flexible disk will be described. The support of the flexible disk is made of a synthetic resin film having flexibility, that is, a flexible polymer support, in order to avoid an impact when the magnetic head and the flexible disk come into contact with each other.
When the magnetic recording medium is a magnetic tape, the flexible support used is as described above for the magnetic recording medium.

  Moreover, you may use what laminated | stacked several synthetic resin films as a flexible polymer support body. By using a laminated film in which a plurality of sheets are laminated, it is possible to reduce warping and undulation caused by the flexible polymer support itself. As a result, the scratch resistance of the magnetic recording layer due to the collision of the surface of the magnetic recording medium with the magnetic head can be remarkably improved. As a method of laminating the flexible film, roll laminating by a hot roll, flat laminating by flat plate hot press, dry laminating by applying an adhesive on the adhesive surface and laminating, or laminating using a pre-formed adhesive sheet Methods and the like. When an adhesive is used for lamination, a 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.

  The thickness of the flexible polymer support is 10 μm to 200 μm, preferably 20 μm to 150 μm, and more preferably 30 μm to 100 μm. 10 μm or more is preferable in terms of good stability during high-speed rotation and prevention of surface blurring. In addition, it exhibits moderate rigidity during rotation, can avoid impact during contact, and can prevent jumping of the magnetic head. 200 μm or less is preferable.

The waist strength of the flexible polymer support represented by the following formula is 4.
9MPa~19.6MPa is preferably in the range of ^{(0.5kgf / mm 2 ~2.0kgf / mm} 2), 6.9MPa~14.7MPa (0.7kgf / mm 2 ~1.5kgf / mm 2) Is more preferable.
Flexible polymeric support waist strength of = Ebd ^3/12
In this equation, E represents Young's modulus, b represents film width, and d represents film thickness.

(Undercoat layer)
An undercoat layer is preferably provided on the surface of the flexible polymer support for the purpose of improving planarity and gas barrier properties. Since the magnetic layer is formed by sputtering or the like, the undercoat layer is preferably excellent in heat resistance. Examples of the material of the undercoat layer include polyimide resin, polyamideimide resin, silicone resin, fluorine resin, ultraviolet curable resin, and electron beam curing. Resin or the like can be used. Thermosetting silicone resins and electrosetting resins are particularly preferred because of their high smoothing effect. The thickness of the undercoat layer is preferably 0.1 μm to 3.0 μm.

  As the thermosetting silicone resin, a silicone resin polymerized by a sol-gel method using a silicon compound having an organic group introduced as a raw material is preferably used. This silicone resin has a structure in which a part of the silicon dioxide bond is substituted with an organic group, and has a heat resistance significantly higher than that of silicone rubber, and also has a softness superior to that of a silicon dioxide film, and thus a flexible film. Even if a resin film is formed on the polymer support, cracks and peeling are unlikely to occur. Moreover, the monomer used as a raw material can be directly applied on a flexible polymer support and cured. In addition, since the monomer can be dissolved and applied in a general organic solvent, it is easy to wrap around unevenness and has a high smoothing effect.

  Furthermore, since the condensation polymerization reaction proceeds from a relatively low temperature by adding a catalyst such as an acid or a chelating agent, it can be cured in a short time, and a resin film can be formed using a general-purpose coating apparatus. Thermosetting silicone resins are excellent in gas barrier properties. For this reason, the gas shielding property which shields the gas which generate | occur | produces from a flexible polymer support body at the time of magnetic layer or base layer formation, and obstructs the crystallinity and orientation of a magnetic layer or base layer is high, and is especially suitable.

  The surface of the undercoat layer is preferably provided with minute protrusions (textures) for the purpose of reducing the true contact area between the magnetic head and the flexible disk and improving the sliding characteristics. In addition, by providing the fine protrusions, the handleability of the flexible polymer support is improved. As a method for forming the fine protrusions, a method of applying spherical silica particles, a method of forming an organic protrusion by applying an emulsion, and the like can be used. However, in order to ensure the heat resistance of the undercoat layer, the spherical silica particles are applied. Thus, it is preferable to form minute protrusions.

The height of the fine protrusion is preferably 5 nm to 60 nm, and more preferably 10 nm to 30 nm. 5 nm or more is preferable from the viewpoint of improving the sliding characteristics, and 60 nm or less is preferable from the viewpoint of preventing deterioration of recording / reproducing characteristics of signals due to spacing loss between the recording / reproducing head and the magnetic recording medium. The density of minute projections is preferably from 0.1 to 100 pieces / [mu] m ^2, more preferably 1 to 10 / [mu] m ^2. 0.1 or in terms of the effect of improving the sliding properties / [mu] m ² or more, to prevent an increase in high projections due to the increase of the agglomerated particles, in that it can prevent the deterioration of the recording and reproducing characteristics are 100 / [mu] m ² or less preferable. In addition, the fine protrusions can be fixed to the support surface using a binder. It is preferable to use a resin having sufficient heat resistance for the binder, and as the resin having heat resistance, a solvent-soluble polyimide resin, a thermosetting polyimide resin, or a thermosetting silicone resin should be used. Is particularly preferred.

  Further, the base layer, seed layer, soft magnetic layer, protective layer, lubricating layer, rust preventive layer, etc. that the flexible disk may have are the same as those in the above-mentioned magnetic tape.

[Production of magnetic recording medium using flexible polymer support]
FIG. 3 is a diagram illustrating a method for forming a magnetic layer on a flexible polymer support. In the following description, a method for forming a magnetic layer on both surfaces of a flexible polymer support will be described, but it is also possible to form a magnetic layer on only one surface by a similar method. The film forming apparatus 1 includes a vacuum chamber 2, and the tension of the flexible polymer support 4 unwound from the unwinding roll 3 is adjusted by the tension adjusting rolls 5 </ b> A and 5 </ b> B to the film forming chamber 6. Sent. In the film forming chamber 6, argon is supplied at a predetermined flow rate from the sputtering gas supply pipes 7 </ b> A to 7 </ b> D while being depressurized to a predetermined depressurization degree by a vacuum pump. When the flexible polymer support 4 is conveyed while being wound around a film forming can 8A provided in the film forming chamber 6, atoms for forming the base layer may be ejected from the target TA of the base layer sputtering apparatus 9A. A film is formed on a flexible polymer support. Note that the temperature of the flexible polymer support during sputtering can be adjusted by adjusting the temperature of the film forming can. The film forming can is maintained at a predetermined temperature by a refrigerant or water. The temperature of the can is usually −50 to 100 ° C., preferably 0 to 50 ° C.

  Next, in the film formation can 8A on the formed underlayer, the atoms for forming the magnetic layer are released from the ferromagnetic metal alloy target TB attached to the magnetic layer sputtering apparatus 9B to form the magnetic layer on the underlayer. The Next, in a state where the surface on which the magnetic layer is formed is moved while being wound around the film forming can 8B, atoms for forming the underlayer jump out from the target TC of the underlayer sputtering apparatus 9C, and the flexible polymer support The side opposite to the surface on which the magnetic layer was previously formed is formed. Further, on the film formation can 8B, the atoms for forming the magnetic layer are released from the ferromagnetic metal alloy target TD attached to the magnetic layer sputtering apparatus 9D, and a magnetic layer is formed on the underlayer.

  Through the above steps, a magnetic layer is formed on both surfaces of the flexible polymer support and is taken up by the take-up roll 10. After forming the magnetic layer, a protective layer including diamond-like carbon is formed on the magnetic layer by a CVD method.

  FIG. 4 is a diagram for explaining an example of a CVD apparatus using high-frequency plasma applicable to the present invention. The flexible polymer support 32 on which the magnetic layer 31 is formed is unwound from the roll 33, and the bias voltage is supplied from the bias power source 35 to the magnetic layer 31 by the pass roller 34 and wound around the film forming can 36. Run. On the other hand, by the plasma generated by the voltage applied from the high frequency power supply 38, the carbon containing nitrogen and rare gas is formed on the metal thin film on the film forming can 36 from the source gas 37 containing hydrocarbon, nitrogen, rare gas and the like. A protective film 39 is formed and wound on the winding roll 40. Also, greater adhesion can be ensured by cleaning the surface of the magnetic film by glow treatment with a rare gas or hydrogen gas before the carbon protective film is formed. Further, the adhesion can be further enhanced by forming a silicon intermediate layer or the like on the surface of the magnetic layer.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.
[Example 1]
Gravure coating method with an undercoat consisting of 3-glycidoxypropyltrimethoxysilane, phenyltriethoxysilane, hydrochloric acid, aluminum acetylacetonate, and ethanol on a polyethylene terephthalate film with a thickness of 6.3 μm and a surface roughness SRa = 1.2 nm Then, drying and curing were performed at 100 ° C., and an undercoat layer made of a silicone resin having a thickness of 0.5 μm was formed only on one surface of the polyethylene terephthalate film. A coating solution in which silica sol having a particle diameter of 18 nm and a solvent-soluble polyimide resin (PI-100 manufactured by Maruzen Petrochemical Co., Ltd.) is dispersed in cyclohexanone is applied on the obtained undercoat layer by a gravure coating method. Protrusions with a thickness of 15 nm were formed at a density of 10 pieces / μm ² to obtain an original film for magnetic tape.

  Next, the web obtained by the web sputtering apparatus shown in FIG. 3 is mounted, and the film is transported while closely contacting the film-cooled film forming can, and CrTi = 80: 20 (by DC pulse sputtering method on the undercoat layer). A base layer made of an atomic ratio) is formed with a thickness of 30 nm, and subsequently a target having a composition made of a CoPtCrB alloy (Co: Pt: Cr: B = 60: 17: 8: 15 atomic ratio) is used as a sputtering gas and argon A magnetic layer having a thickness of 20 nm was formed by a DC pulse sputtering method using a gas. In forming the underlayer and the magnetic layer, the temperature of the film formation can was adjusted, and the temperature of the original fabric was set to 15 ° C.

  Next, the raw material on which the magnetic layer is formed is mounted on a web-type CVD apparatus as shown in FIG. 4, and C: H: N is obtained by RF plasma CVD using ethylene gas, nitrogen gas, and argon gas as reaction gases. A protective film of nitrogen-added diamond-like carbon (DLC) composed of 62: 29: 7 (mol ratio) was formed to a thickness of 5 nm. At this time, a bias voltage of −400 V was applied to the film formation can.

  Further, a gravure coating method is used in which a solution of a perfluoropolyether lubricant having a hydroxyl group at the molecular end on the surface of the protective layer (FOMBLIN Z-DOL manufactured by Augmont) in a fluorine-based solvent (HFE-7200 manufactured by Sumitomo 3M) is dissolved. Was applied to form a 1 nm thick lubricating layer.

  Next, a back coat solution in which carbon black, calcium carbonate, stearic acid, nitrocellulose, polyurethane, and isocyanate curing agent are dissolved and dispersed in methyl ethyl ketone on the surface opposite to the surface on which the magnetic layer of the flexible polymer support is formed. Was applied by a wire bar method and dried at 100 ° C. to prepare a backcoat layer having a thickness of 0.5 μm.

  The magnetic recording medium thus obtained was cut to a width of 6.35 mm, and the surface was tape burnished and then incorporated into a 6.35 mm video cassette cartridge to produce a magnetic tape. The characteristics of this magnetic tape were evaluated by the following evaluation method. The results are shown in Table 1.

[Comparative Example 1]
A magnetic tape was prepared and carried out in the same manner as in Example 1 except that a target having a composition made of a CoPtCr alloy (Co: Pt: Cr: = 70: 20: 10 atomic ratio) was used as the magnetic layer in Example 1. Evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 2]
In Comparative Example 1, a magnetic tape was prepared in the same manner as in Comparative Example 1 except that the film formation can when forming the underlayer and the magnetic layer was changed to 150 ° C. The evaluation was performed in the same manner as in Example 1. went. The results are shown in Table 1.

(Evaluation method of magnetic tape)
<Magnetic properties>
The coercive force Hc was measured with a sample vibration magnetometer (VSM) to obtain magnetic characteristics.
<Copping amount>
The magnetic tape was cut to a length of 100 mm, placed on a smooth glass plate, and the tape width was measured to evaluate the deformation in the tape width direction as the cupping amount.

<SNR>
Recording / reproduction with a linear recording density of 130 kFCI was performed using an MR head with a reproduction track width of 2.2 μm and a reproduction gap of 0.26 μm, and reproduction signal output / noise (SNR) was measured. At this time, the tape / head relative speed was 10 m / sec, and the head load was 29.4 mN (3 gf). Noise integration was 5 to 260 kFCI.
<Durability>
Still playback was performed with a digital video tape recorder, and the still playback time until the output became the initial value of −3 dB was expressed as endurance time. The measurement environment was 23 ° C. and 10% RH, and the test was performed for a maximum of 24 hours.

  From the above results, it can be seen that the magnetic tape of the present invention is excellent in both recording characteristics and durability. On the other hand, in the magnetic tape of Comparative Example 1 in which B is not added to the magnetic layer, the coercive force (Hc) is lowered and the recording characteristics are lowered. Further, in Comparative Example 2 in which the film formation temperature of the underlayer and the magnetic layer was increased, although the coercive force was improved, the film of the flexible polymer support was deformed by heat and the durability was remarkably deteriorated. Further, when the tape surface was observed with a microscope, fine cracks were generated in the magnetic layer.

[Example 2]
Undercoat layers were formed on both sides of a polyethylene naphthalate film having a thickness of 63 μm and a surface roughness SRa = 1.4 nm. Specifically, after applying an undercoat liquid consisting of 3-glycidoxypropyltrimethoxysilane, phenyltriethoxysilane, hydrochloric acid, aluminum acetylacetonate, and ethanol by a gravure coating method, drying and curing at 100 ° C., An undercoat layer made of silicon resin having a thickness of 1.0 μm was prepared. A coating solution in which silica sol having a particle diameter of 18 nm and a solvent-soluble polyimide resin (PI-100 manufactured by Maruzen Petrochemical Co., Ltd.) is dispersed in cyclohexanone is applied on the undercoat layer by a gravure coating method, and a height of 15 nm is applied on the undercoat layer. Were formed at a density of 5 pieces / μm ² to obtain an original for a flexible disk.

  Next, using the apparatus shown in FIG. 3, a seed layer, an underlayer, and a magnetic layer were formed on both sides of the original fabric. Specifically, the web obtained by the web sputtering apparatus shown in FIG. 3 is mounted, and the film is transported while adhering the film onto a water-cooled film forming can. A seed layer made of 20 nm is formed, and an underlayer made of Ru is formed thereon with a thickness of 30 nm. Subsequently, a CoPtCrB alloy (Co: Pt: Cr: B = 60: 17: 8: 15 atomic ratio) is formed. A magnetic layer having a thickness of 20 nm was formed by DC pulse sputtering using an argon gas as a sputtering gas. By adjusting the temperature of the film forming can, the temperature of the original fabric when forming the seed layer, the underlayer and the magnetic layer was set to 15 ° C.

  Next, the raw material on which the magnetic layer was formed was placed in the web-type CVD apparatus shown in FIG. 4, and C: H: N = 62: 29 by RF plasma CVD using ethylene, nitrogen gas, and argon as reaction gases. A protective film made of nitrogen-added diamond-like carbon consisting of 7 (mol ratio) was formed to a thickness of 10 nm. At this time, a bias voltage of −400 V was applied to the film formation can. A protective layer was also formed on both sides of the film.

  Next, a gravure solution obtained by dissolving a perfluoropolyether lubricant (FOMBLIN Z-DOL manufactured by Montefluos Co., Ltd.) having a hydroxyl group at the molecular terminal on the surface of the protective layer on both surfaces in a fluorine-based solvent (HFE-7200 manufactured by Sumitomo 3M Co.) The coating was applied to form a 1 nm thick lubricating layer.

A disk having a diameter of 94 mm is punched out from the magnetic recording medium thus obtained, tape burnished, and then incorporated into a synthetic resin cartridge for flexible disks (for Zip 100 manufactured by Fuji Photo Film Co., Ltd.). Produced. The characteristics of this flexible disk were evaluated by the following evaluation method. The results are shown in Table 2.

[Comparative Example 3]
A sample was prepared in the same manner as in Example 2 except that a target composed of a CoPtCr alloy (Co: Pt: Cr: = 70: 20: 10 atomic ratio) was used as the magnetic layer in Example 2. Evaluation was performed in the same manner. The results are shown in Table 2.

[Comparative Example 4]
In Comparative Example 3, a flexible disk was prepared in the same manner as in Comparative Example 3 except that the film formation can when the seed layer, the underlayer and the magnetic layer were formed, and the temperature of the original fabric was set to 150 ° C. Was evaluated. The results are shown in Table 2.

(Flexible disk evaluation method)
<Magnetic properties>
The coercive force Hc was measured with a sample vibration magnetometer (VSM) to obtain magnetic characteristics.
<Surface>
The flexible disk was rotated at 3000 rpm, and surface blurring at a radius of 35 mm from the center was measured with a laser displacement meter.

<SNR>
Using a GMR head having a recording track width of 0.40 μm, a recording gap of 0.15 μm, a reproduction track width of 0.25 μm, and a reproduction gap of 0.08 μm, recording / reproduction with a linear recording density of 200 kFCI is performed, and reproduction signal output / noise (SNR) Was measured. At this time, the rotation speed was set to 3000 rpm and the head radius was set to 35 mm. The head load was 29.4 mN (3 gf). The noise was the integral of the modulation noise for the band of 5 to 400 kFCI.

<Modulation>
The reproduction output at the time of the C / N measurement was measured for one round of the disk, and the ratio of the minimum value of this output to the maximum value was expressed in 100%.
<Durability>
The flexible disk was run while repeatedly recording and reproducing with a flexible disk drive (Zip100 drive manufactured by Fuji Photo Film Co., Ltd.). When the output reached an initial value of -3 dB, the running was stopped and the durability time was set. The environment was 23 ° C. and 50% RH, and the test was performed for a maximum of 300 hours.

  As can be seen from the above results, the flexible disk of the present invention is excellent in both recording characteristics and durability. On the other hand, in Comparative Example 3 in which B was not used in the magnetic layer, the coercive force was lowered and the recording characteristics were lowered. Further, in Comparative Example 4 in which the film formation temperature of the magnetic layer was increased, the coercive force was improved, but the flexible polymer support film was deformed by heat, and the surface blurring and durability deteriorated.

FIG. 1 is a sectional view showing one embodiment of the present invention. FIG. 2 is a cross-sectional view showing another embodiment of the present invention. FIG. 3 is a diagram illustrating an example of a method for forming a magnetic layer on a flexible polymer support. FIG. 4 is a diagram showing an example of a CVD apparatus using high-frequency plasma applicable to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Film-forming apparatus, 2 ... Vacuum chamber, 3 ... Unwinding roll, 4 ... Flexible polymer support body, 5A, 5B ... Tension adjusting roll, 6 ... Film-forming chamber, 7A, 7B, 7C, 7D ... Sputtering Gas supply pipe, 8A, 8B ... Film formation can, 9A, 9B, 9C, 9D ... Underlayer sputtering apparatus, TA, TB, TC, TD ... Target, 10 ... Winding roll, 11 ... Magnetic tape, 12 ... Flexible 13 ... undercoat layer, 14 ... undercoat layer, 15 ... magnetic layer, 16 ... protective layer, 17 lubrication layer, 21 ... flexible disk, 22 ... flexible polymer support, 23 ... undercoat layer, 24 ... underlying layer, 25 ... magnetic layer made of a ferromagnetic metal alloy, 26 ... protective layer, 27 ... lubricating layer, 30 ... engaging means, 31 ... magnetic layer, 32 ... flexible polymer support, 33 ... roll , 34 ... pass rollers, 35 ... bias power supply, 36 ... Film scanning, 37 ... feed gas, 38 ... high frequency power source, 39 ... carbon protective film, 40 ... take-up roll

Claims (2)

  A magnetic recording medium comprising a magnetic layer made of a ferromagnetic metal alloy containing at least Co, Pt, Cr and B on at least one surface of a flexible polymer support.   2. The magnetic recording medium according to claim 1, wherein the content of B in the ferromagnetic metal alloy is 10 to 20 atomic%.