JP2005129207A - Magnetic recording medium and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high capacity magnetic recording medium which has high-performance, and is reliable and inexpensive, by forming a protective layer made of a hard-carbon film without occurring contamination on a magnetic layer having a granular structure. <P>SOLUTION: This magnetic recording medium is provided with the magnetic layer having at least the granular structure, and the protective layer at least on one surface of a support in this order. The protective layer is the hard-carbon film formed by an ion beam deposition method. A ratio (ID/IG) of the intensity (ID) of D peak which has a peak in the range of 1,350-1,430 cm<SP>-1</SP>to the intensity (IG) of G peak which has a peak in the range of 1,500-1,600 cm<SP>-1</SP>in the Raman spectrum by the Raman spectroscopy is 0.5-1.0. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a magnetic recording medium used for recording digital information and a manufacturing method thereof.

  In recent years, with the spread of the Internet, the use form of computers has changed, such as processing of large-capacity moving image information and audio information using a personal computer. Accordingly, the storage capacity required for magnetic recording media such as hard disks is also increasing.

  In the hard disk device, the magnetic head slightly floats from the surface of the magnetic disk as the magnetic disk rotates, and performs magnetic recording without contact. For this reason, the magnetic disk is prevented from being damaged by the contact between the magnetic head and the magnetic disk. As the density increases, the flying height of the magnetic head is gradually reduced. By using a magnetic disk in which a magnetic recording layer or the like is formed on a mirror-polished ultra-smooth glass substrate, the current height is 10 nm to 20 nm. The flying height is realized. In the medium, a CoPtCr-based magnetic layer / Cr underlayer is generally used. By increasing the temperature to 200 ° C. to 500 ° C., the easy direction of magnetization of the CoPtCr-based magnetic layer is in-plane with the Cr underlayer. It is controlled to become. Further, segregation of Cr in the CoPtCr-based magnetic layer is promoted, and magnetic domains in the magnetic layer are separated. Due to such technological innovations as reducing the flying height of the head, improving the head structure, and improving the disk recording film, the surface recording density and recording capacity of the hard disk drive have increased dramatically in the last few years.

  Increasing the amount of digital data that can be handled has created a need for recording and moving large volumes of data such as video data on a removable medium. However, since the hard disk has a hard substrate and the distance between the head and the disk is very small as described above, if it is used as a replaceable medium like a flexible disk or a rewritable optical disk, the impact during operation There is a high risk of malfunction due to entrapment of dust and dust, and it cannot be used.

  Further, when the high-temperature sputter film forming method is used in the production of the medium, not only the productivity is bad, but also the cost is increased at the time of mass production, so that it cannot be produced at a low cost.

On the other hand, a flexible disk is a polymer film with a flexible substrate and is a contact-recordable medium, so it has excellent interchangeability and can be produced at low cost. Is coated on a polymer film together with a polymer binder and an abrasive. Therefore, compared with a hard disk on which a magnetic film is formed by sputtering, the magnetic layer has poor high-density recording characteristics and is 1/10 that of a hard disk. Only the following recording density has been achieved.
Therefore, a ferromagnetic metal thin film type flexible disk in which the recording film is formed by the same sputtering method as that of the hard disk has been proposed. However, if a magnetic layer similar to the hard disk is formed on the polymer film, the heat of the polymer film Damage is great and practical application is difficult. For this reason, proposals have been made to use a highly heat-resistant polyimide or aromatic polyamide film as the polymer film, but these heat-resistant films are very expensive and difficult to put into practical use. If an attempt is made to form a magnetic film while the polymer film is cooled so as not to cause thermal damage to the polymer film, the magnetic properties of the magnetic layer become insufficient, making it difficult to improve the recording density.

  On the other hand, when a ferromagnetic metal thin film magnetic layer made of a ferromagnetic metal alloy and a nonmagnetic oxide or a Ru-based underlayer is used, the film is formed at a high temperature of 200 ° C. to 500 ° C. even when it is formed at room temperature. It has been found that magnetic properties almost equivalent to those of the coated CoPtCr magnetic layer can be obtained (see Patent Documents 1 and 2). Such a ferromagnetic metal thin film magnetic layer made of a ferromagnetic metal alloy and a nonmagnetic oxide has a so-called granular structure proposed for hard disks, and those described in Patent Document 3 and Patent Document 4 can be used.

  However, in a flexible disk using a metal thin film magnetic layer on a polymer film, sufficient running durability is not yet obtained due to sliding wear with a magnetic head during contact recording / reproduction.

  In response to the above-mentioned problems, an RF plasma CVD DLC (diamond-like carbon) protective layer in which a hard protective layer is formed without deformation of the polymer film substrate while the substrate is placed along a can has been studied. (Patent Documents 5, 6, etc.). When forming a protective layer by the RF plasma CVD method, it is necessary to attract ionized carbon in the plasma by applying a bias voltage to the substrate side. However, since a magnetic layer having a granular structure contains a conductive material and an insulating material, a sufficient bias cannot be applied to the surface of the magnetic layer when a bias voltage is applied. Therefore, it has been difficult to obtain a high hardness protective layer.

  Further, when an RF plasma CVD type DLC protective layer is formed in a web type apparatus, a large amount of carbon film adheres to a reaction tube portion where high density plasma is generated. For this reason, if the film is formed for a long time, carbon adheres to the substrate as a contamination and has an adverse effect, and thus it has been difficult to apply to a long web.

  On the other hand, a method of forming a hard protective layer by an ion beam deposition method using an ion beam gun having a hot filament or a grid has been studied (Patent Documents 7, 8, etc.). However, as described in the above disclosure, it has been difficult to form a protective layer for a long time due to the short life of the hot filament and the occurrence of contamination due to the grid between the ion source and the substrate. .

  Write-once and rewritable optical discs typified by DVD-R / RW have excellent interchangeability and are widespread because the head and the disc are not close to each other like a magnetic disc. However, the optical disk has a problem in that it is difficult to use a disk structure having recording surfaces on both sides like a magnetic disk advantageous for increasing the capacity because of the thickness and cost of the optical pickup. Furthermore, since the surface recording density is low and the data transfer speed is low as compared with the magnetic disk, it cannot be said that the performance is still sufficient when considering use as a rewritable large-capacity recording medium.

  As described above, high-capacity rewritable replaceable recording media are highly demanded, but none satisfy the performance, reliability, and cost.

JP 2001-291230 A JP 2003-99918 A JP-A-5-73880 Japanese Patent Laid-Open No. 7-311929 Japanese Patent Laid-Open No. 3-113824 Japanese Patent Laid-Open No. 10-219459 JP 2000-260020 A JP 2002-109718 A

  The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to form a protective layer made of a hard carbon film on a magnetic layer having a granular structure without causing contamination. An object of the present invention is to provide a high-capacity magnetic recording medium having high performance, high reliability, and low cost.

Means for achieving the object is as follows.
1) A magnetic recording medium in which a magnetic layer having at least a granular structure and a protective layer are formed in this order on at least one surface of a support, and the protective layer is a hard carbon film formed by an ion beam deposition method. there are, the ratio of the intensity of the D peak having a peak in the range of the intensity (IG) and 1350～1430Cm ^-1 of G peak having a peak in the range of 1500～1600Cm ^-1 in the Raman spectrum by the Raman spectroscopy (ID) ( (ID / IG) is 0.5 to 1.0.
2) The hard carbon film by the ion beam deposition method uses a gridless ion source having a structure capable of supplying a magnetic field and a voltage, having a gas introduction port capable of introducing at least a hydrocarbon-based gas. The magnetic recording medium as described in 1) above, which is formed by
3) The magnetic recording medium as described in 1) or 2) above, wherein the support is a flexible polymer support.
4) The magnetic recording medium as described in any one of 1) to 3) above, wherein the protective layer has a multilayer structure, and the uppermost protective layer is a hard carbon film added with nitrogen.
5) The magnetic recording medium according to any one of 1) to 4) above, wherein an underlayer containing at least Ru is provided between the support and the magnetic layer.
6) A method of manufacturing a magnetic recording medium in which a magnetic layer having at least a granular structure and a protective layer are formed in this order on at least one surface of a support, wherein the protective layer introduces at least a hydrocarbon-based gas. Formed by an ion beam deposition method using a gridless ion source having a structure capable of applying a magnetic field and a voltage, and a magnetic field applied to the ion source is 0.03 T (300 gauss) The method for producing a magnetic recording medium according to any one of 1) to 4) above, wherein the voltage is in the range of 100 to 3000 V in the range of ˜1 T (10000 gauss).

  According to the present invention, it is possible to inexpensively produce a magnetic recording medium suitable for use in a high-density magnetic recording apparatus, having low interaction between ferromagnetic materials, low noise, and high reliability by room temperature film formation. it can.

  Since the magnetic recording medium of the present invention includes at least a magnetic layer having a granular structure, recording at a high recording density like a hard disk is possible even when a film is formed at room temperature, and the capacity can be increased.

Further, a hard carbon film formed by ion beam deposition as a protective layer on the magnetic layer, and the intensity of G peak having a peak in the range of 1500 to 1600 cm ^{−1 in} the Raman spectrum by Raman spectroscopy ( IG) and a D-peak intensity (ID) ratio (ID / IG) having a peak in the range of 1350 to 1430 cm ⁻¹ , providing a protective layer having a ratio (ID / IG) of 0.5 to 1.0. It is possible to obtain sufficient running durability even during contact recording with the magnetic recording medium, and to provide a highly reliable magnetic recording medium.

  By forming such a magnetic layer and a protective layer, it is possible to obtain a magnetic recording medium having good S / N characteristics even when the substrate temperature is room temperature without the need for conventional substrate heating. Become. For this reason, it is possible to provide not only glass substrates and Al substrates but also flat magnetic tapes and flexible disks that are resistant to contact recording without causing thermal damage even if the support is a polymer film. Become.

As the support of the magnetic recording medium according to the present embodiment, an Al substrate or a glass substrate can be used, but a flexible polymer film is more preferable in terms of productivity. This embodiment can be used in a tape shape or a flexible disk shape.
The present flexible disk using a flexible polymer film support has a structure in which a center hole is formed at the center, and is stored in a cartridge formed of plastic or the like. The cartridge is usually provided with an access window covered with a metallic shutter, and a magnetic head is introduced through the access window to record and reproduce signals on the flexible disk.

Hereinafter, the flexible disk will be described, but the contents can also be applied to a tape.
A flexible disk has a magnetic layer and a protective layer on each of both surfaces of a disk-shaped support made of a flexible polymer film, and further, an undercoat layer for improving surface properties and gas barrier properties, and an adhesion / gas barrier. A gas barrier layer having functions such as a property, an underlayer for controlling the crystal orientation of the magnetic layer, a magnetic layer, a protective layer for protecting the magnetic layer from corrosion and wear, and a lubricating layer for improving running durability and corrosion resistance It is preferable that the layers are stacked in this order.

  The magnetic layer may be an in-plane magnetic recording film having an easy axis of magnetization oriented in the horizontal direction with respect to the support or a perpendicular magnetic recording film oriented in the direction perpendicular to the support. The direction of the easy axis of magnetization can be controlled by the material and crystal structure of the underlayer, the composition of the magnetic film, and the film formation conditions.

  The magnetic layer has a granular structure and is also referred to as a granular magnetic layer. The granular magnetic layer is made of a ferromagnetic metal alloy and a nonmagnetic oxide. In the granular structure, the ferromagnetic metal alloy and the nonmagnetic oxide are mixed macroscopically, but the microscopic structure is such that the ferromagnetic metal alloy fine particles are covered with the nonmagnetic oxide, which is strong. The size of the magnetic metal alloy particles is about 1 nm to 110 nm. With such a structure, a high coercive force can be achieved and the dispersibility of the magnetic particle size can be made uniform, so that a low noise medium can be achieved.

  As the ferromagnetic metal alloy, alloys with elements such as Co, Cr, Pt, Ni, Fe, B, Si, Ta, Nb, and Ru can be used. However, in consideration of recording characteristics, Co—Pt—Cr, Co—Pt are considered. -Cr-Ta, Co-Pt-Cr-B, Co-Ru-Cr and the like are particularly preferable.

  As the nonmagnetic oxide, oxides such as Si, Zr, Ta, B, Ti, Al, Cr, Ba, Zn, Na, La, In, and Pb can be used, but SiOx is most preferable in consideration of recording characteristics.

  The mixing ratio (molar ratio) between the ferromagnetic metal alloy and the nonmagnetic oxide is preferably in the range of ferromagnetic metal alloy: nonmagnetic oxide = 95: 5 to 80:20, and 90:10 to 85:15. It is particularly preferable that the range is By adjusting the mixing ratio as described above, the separation between the magnetic particles becomes sufficient, the coercive force is ensured and the amount of magnetization is secured, so that the signal output is secured.

  The granular magnetic layer preferably has a thickness of 5 nm to 60 nm, more preferably 5 nm to 30 nm, so as to reduce noise and suppress the influence of thermal fluctuation, and to ensure output, and head-media contact Resistance to stress that is sometimes applied can be secured, and running durability can be secured.

  As a method for forming the granular magnetic layer, a vacuum film forming method such as a vacuum deposition method or a sputtering method can be used. Among these, the sputtering method is suitable for the present invention because a good ultra-thin film can be easily formed. As the sputtering method, a known DC sputtering method, RF sputtering method, or the like can be used. As the sputtering method, a web sputtering apparatus for continuously forming a film on a continuous film is suitable, but a sheet-type sputtering apparatus and a passing-type sputtering apparatus used for manufacturing a hard disk can also be used.

  A general argon gas can be used as a sputtering gas during sputtering, but other rare gases may be used. A small amount of oxygen gas may be introduced for the purpose of adjusting the oxygen content of the nonmagnetic oxide or surface oxidation.

  In order to form a granular magnetic layer by sputtering, two types of ferromagnetic metal alloy target and nonmagnetic oxide target can be used, and these co-sputtering methods can be used. It is preferable to use an alloy target of a ferromagnetic metal alloy and a nonmagnetic oxide in order to improve the above and create a homogeneous film. This alloy target can be prepared by a hot press method.

  As Ar pressure at the time of forming a granular magnetic layer by sputtering, 5 to 100 mTorr (0.7 to 13.3 Pa) is preferable, and 10 to 50 mTorr (1.3 to 6.7 Pa) is particularly preferable. By setting the Ar pressure during film formation within this range, the crystallinity of the magnetic layer and the separation between the magnetic particles are ensured, sufficient magnetic properties can be obtained, low noise, high strength and reliable magnetic properties. A recording medium can be provided.

The input power at the time of forming the granular magnetic layer by sputtering, preferably 1~100W / cm ^2, particularly preferably 2~50W / cm ^2, the support modified with adhesion of the crystalline and membrane is secured And the generation of cracks in the sputtered film can be prevented.

  The protective layer is made of a hard carbon film that prevents corrosion of the metal material contained in the magnetic layer, and prevents wear due to pseudo contact or contact sliding between the magnetic head and the magnetic disk, thereby improving running durability and corrosion resistance. To be provided. The protective layer that achieves these objectives is a hard film with a hardness equal to or higher than that of the magnetic head material. It is hard to cause seizure during sliding, and its effect is stable and durable. It is excellent in properties and preferable. At the same time, those with less contamination and pinholes are more preferred because they are excellent in corrosion resistance and running durability. Examples of the hard carbon film used for such a protective layer include what is called DLC (diamond-like carbon).

Examples of the hard carbon film quality evaluation method include Raman spectroscopy. When the Raman spectrum of the hard carbon film is examined, a broad peak is observed at a Raman shift of 1000 to 1800 cm ⁻¹ .
In the present invention, the intensity of the D peak having a peak in the range intensity of G peak having a peak in the range of 1500～1600Cm ^-1 and (IG) of 1350～1430Cm ^-1 in the Raman spectrum by Raman spectroscopy of the hard carbon film ( The hard carbon film is controlled so that the ratio of (ID) (ID / IG) is 0.5 to 1.0, preferably 0.4 to 1.4, and more preferably 0.5 to 1.0.
The G peak is a main peak and the D peak is a shoulder. Although both IG and ID are peaks due to the sp ² structure, the ratio (ID / IG) is said to reflect the ratio of the sp ³ structure.
The organic property of the film (polymer component: non-hard hydrogen-containing carbon component) can be evaluated by the ratio B / A of the G peak intensity B including the background and the G peak intensity A not including the background. In the present invention, the ratio B / A is preferably 1.0 to 2.0, and more preferably 1.0 to 1.5.

  The protective layer can be formed into a multilayer structure in which two or more kinds of thin films having different properties are laminated by using the present ion beam deposition method. For example, by providing a nitrogen-added hard carbon film for improving sliding properties on the surface side and a hard carbon film for improving hardness and corrosion resistance on the magnetic layer side, corrosion resistance and durability are at a high level. It is possible to achieve both.

In magnetic recording / reproduction, a smaller distance between the magnetic head and the magnetic layer is advantageous for high recording density. Therefore, the total thickness of the protective layer is preferably 2 to 10 nm, and more preferably 2 to 8 nm.
Further, the surface resistivity of the magnetic recording medium of the present invention is preferably a value measured by a four-terminal method and within a range of 10Ω / □ to 200Ω / □.

  As a method for forming such a hard carbon film, there is an RF plasma CVD method. As described above, from the viewpoint of film quality, contamination, support deformation, film thickness distribution, etc., this ion beam deposition method is used. desirable.

  A high-density plasma is formed by applying an appropriate magnetic field and electric field to the ion source used in the present ion beam deposition method in a state where a hydrocarbon-based gas is flowed. By applying a strong positive potential to the ion source, ionized carbon is pushed out, so that a dense carbon film is formed. In other words, since there is no need to apply a bias voltage to the support or to cause contamination, it is hard even for a support in which a conductive material such as a granular magnetic layer and an insulating material are mixed. In addition, it is possible to form a hard protective film with little contamination. In addition, since a short-life component such as a hot filament is not used, a hard protective layer can be stably formed over a long period of time.

  As a gas for forming the hard protective layer by the ion beam deposition method, a hydrocarbon gas, a rare gas such as Ar, nitrogen, or the like can be used. The chamber pressure during film formation is preferably 10 mTorr (1.3 Pa) or less, and more preferably 5 mTorr (0.7 Pa) or less. When the chamber pressure is 10 mTorr (1.3 Pa) or less, the carbon ions ionized in the high-density plasma have a low possibility of colliding with other ions, and thus the carbon ions have high energy. Therefore, a denser and harder film is formed when reaching the support.

  The voltage applied to the anode in the ion source is preferably 100 to 3000 V, more preferably 500 to 2000 V. The voltage applied to the cathode is preferably 0 to -1000V, more preferably 0 to -500V. The magnetic field applied to the ion source surface is preferably 0.03 T (300 gauss) to 1 T (10000 gauss), and more preferably 0.05 T (500 gauss) to 0.5 T (5000 gauss). By setting the potential and magnetic field in this way, the plasma density is ensured, ionization is promoted, the energy to be pushed out against the ionized carbon is secured, and a sufficiently dense hard carbon film is formed and the ionized carbon The influence on the support is small, and deformation of the support and the generation of cracks in the film can be prevented, and arcing between the anode and the cathode can also be prevented.

  The underlayer is preferably provided for the purpose of controlling the crystal orientation of the magnetic layer. As such an underlayer, Ru, Ru alloy, Cr, Cr alloy, Ti, Ti alloy or the like can be used, but in order to obtain sufficient crystallinity at room temperature film formation, Ru, Ru It is desirable to use an alloy. 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 5 nm to 100 nm, particularly preferably 5 nm to 50 nm. Within this range, magnetic properties are improved, productivity is secured, crystal grain enlargement is suppressed, and noise is suppressed, and resistance to stress applied during head-media contact is ensured. Therefore, running durability is ensured.

  As a method for forming the underlayer, a vacuum film forming method such as a vacuum deposition method or a sputtering method can be used. Among these, the sputtering method is suitable for the present invention because a good ultra-thin film can be easily formed. As the sputtering method, a known DC sputtering method, RF sputtering method, or the like can be used. In the case of a flexible disk using a flexible polymer film as a support, the sputtering method is preferably a web sputtering apparatus for continuously forming a film on a continuous film, but is used when an Al substrate or a glass substrate is used. Such a sheet-type sputtering apparatus or a passing-type sputtering apparatus can also be used.

  A general argon gas can be used as a sputtering gas during the underlayer sputtering, but other rare gases may be used. Further, a trace amount of oxygen gas may be introduced for the purpose of controlling the lattice constant of the underlayer.

  A seed layer may be provided between the base layer and the support for the purpose of improving the crystal orientation of the base layer and imparting conductivity.

  As such a seed layer, it is desirable to use a Ti-based, W-based or V-based alloy, but other alloys may be used.

  The thickness of the seed layer is preferably 1 nm to 30 nm. Productivity is ensured by setting it as this range, and noise is suppressed by suppressing the enlargement of a crystal grain.

  As a method for forming the seed layer, a vacuum film-forming method such as a vacuum deposition method or a sputtering method can be used. Among these, a sputtering method can easily form a good ultra-thin film.

  For the purpose of improving adhesion and gas barrier properties, it is desirable to provide a gas barrier layer between the support and the underlayer. When providing the seed layer, the gas barrier layer is preferably provided between the seed layer and the support.

  As such a gas barrier layer, a nonmetallic element alone or a mixture thereof, or a layer made of a compound of Ti and a nonmetallic element can be used. These materials are also resistant to stress during head-media contact.

  The thickness of the gas barrier layer is preferably 5 nm to 100 nm, particularly preferably 5 nm to 50 nm. Productivity is ensured by setting it as this range, and noise is suppressed by suppressing the enlargement of a crystal grain.

  As a method for forming the gas barrier layer, a vacuum film-forming method such as a vacuum deposition method or a sputtering method can be used. Among these, a sputtering method can easily form a good ultra-thin film.

  The support is preferably a resin film having flexibility (flexible polymer support), and can avoid impact when the magnetic head and the magnetic disk come into contact with each other. Examples of such resin films include aromatic polyimide, aromatic polyamide, aromatic polyamideimide, polyether ketone, polyether sulfone, polyether imide, polysulfone, polyphenylene sulfide, polyethylene naphthalate, polyethylene terephthalate, polycarbonate, and triacetate cellulose. And a resin film made of fluorine resin or the like. In the present invention, since good recording characteristics can be achieved without heating the support, polyethylene terephthalate or polyethylene naphthalate is particularly preferred from the viewpoint of cost and surface properties.

  Further, a laminate in which a plurality of resin films are laminated may be used as the support. By using the laminate film, it is possible to reduce warpage and undulation caused by the support itself, and to significantly improve the scratch resistance of the magnetic recording layer.

  Examples of the laminating method include roll laminating using a heat roller, laminating using a flat plate heat press, dry laminating by applying an adhesive to the adhesive surface and laminating, and laminating using an adhesive sheet previously formed into a sheet shape. The type of the adhesive is not particularly limited, and a general hot melt adhesive, thermosetting adhesive, UV curable adhesive, EB curable adhesive, pressure-sensitive adhesive sheet, anaerobic adhesive, or the like may be used. Yes.

  The thickness of the support is 10 μm to 200 μm, preferably 20 μm to 150 μm, more preferably 30 μm to 100 μm, so that stability during high-speed rotation is maintained, surface blurring is suppressed, and rigidity during rotation is maintained low. In addition, the impact at the time of contact can be avoided, and jumping of the magnetic head can be prevented.

The strength of the waist of the support is represented by the following formula, and the value at b = 10 mm may be in the range of 0.5 kgf / mm ^{2 to} 2.0 kgf / mm ² (4.9 to 19.6 MPa). ^{preferably, 0.7kgf / mm 2 ~1.5kgf / mm} 2 (6.9~14.7MPa) is more preferable.
The waist of the strength of the support = Ebd ^3/12
In this equation, E represents Young's modulus, b represents film width, and d represents film thickness.

  The surface of the 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, when an undercoat layer described later is used, the surface roughness measured with an optical surface roughness meter is within 5 nm, preferably within 2 nm, with a center line average roughness Ra, and a stylus roughness meter. The height of the protrusion measured in step 1 is within 1 μm, preferably within 0.1 μm. When the undercoat film is not used, the surface roughness measured with an optical surface roughness meter is within 3 nm, preferably within 1 nm, as the centerline average roughness Ra, and the protrusion height measured with a stylus roughness meter Is within 0.1 μm, preferably within 0.06 μm.

  An undercoat layer is preferably provided on the surface of the 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. As the material of the undercoat layer, for example, a polyimide resin, a polyamideimide resin, a silicon resin, a fluorine resin, or the like can be used. . Thermosetting polyimide resins and thermosetting silicone resins are particularly preferred because they have a high smoothing effect. The thickness of the undercoat layer is preferably 0.1 μm to 3.0 μm. When laminating another resin film on the support, an undercoat layer may be formed before laminating, or an undercoat layer may be formed after laminating.

  As the thermosetting polyimide resin, for example, polyimide obtained by thermal polymerization of an imide monomer having two or more terminal unsaturated groups in the molecule, such as bisallyl nadiimide “BANI” manufactured by Maruzen Petrochemical Co., Ltd. Resins are preferably used. Since this imide monomer can be thermally polymerized at a relatively low temperature after being applied to the surface of the support in the monomer state, the monomer as a raw material can be directly applied to the support and cured. In addition, this imide monomer can be used by being dissolved in a general-purpose solvent. It has excellent productivity and workability, has a low molecular weight, and its solution viscosity is low. Is expensive.

  As the thermosetting silicon resin, a silicon resin polymerized by a sol-gel method using a silicon compound having an organic group introduced as a raw material is preferably used. This silicon 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 silicon rubber, and also has a flexibility higher than that of a silicon dioxide film, and thus a flexible film. Even if a resin film is formed on the support, cracks and peeling are unlikely to occur. Moreover, since the monomer used as a raw material can be directly applied and cured on the support, a general-purpose solvent can be used, the wrapping around the unevenness is good, and the smoothing effect is high. 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 have excellent gas barrier properties, and are particularly suitable because they have a high gas barrier property that shields gases that hinder the crystallinity and orientation of the magnetic layer or underlayer generated from the support during the formation of the magnetic layer. .

  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 magnetic disk and improving the sliding characteristics. Moreover, the handling property of the support is improved by providing the fine protrusions. 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 microprojections is preferably 5 nm to 60 nm, and more preferably 10 nm to 30 mm. If the height of the minute protrusion is too high, the recording / reproducing characteristics of the signal deteriorate due to the spacing loss between the recording / reproducing head and the medium, and if the minute protrusion is too low, the effect of improving the sliding characteristic is reduced. The density of minute projections is preferably from 0.1 to 100 pieces / [mu] m ^2, more preferably 1 to 10 / [mu] m ^2. If the density of the microprojections is too small, the effect of improving the sliding characteristics is reduced. If the density is too large, high projections are increased due to an increase in aggregated particles, and the recording / reproducing characteristics are deteriorated.

  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.

  On the protective layer, a lubricating layer is provided in order to improve running durability and corrosion resistance. For the lubricating layer, known lubricants such as hydrocarbon lubricants, fluorine lubricants, and extreme pressure additives are used.

  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 Co., Ltd.).

  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

These lubricants can be used alone or in combination, and 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.

Moreover, in order to further improve corrosion resistance, it is preferable to use a rust inhibitor together. Antirust agents 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-mercapton benzothiazole, tetrazaindene Examples thereof include nitrogen- and sulfur-containing heterocycles such as ring compounds and thiouracil compounds and derivatives thereof. These rust preventives may be mixed with a lubricant and applied onto the protective layer, or may be applied onto the protective layer 18 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.

Specific examples of the present invention will be described below, but the present invention is not limited thereto.
(Example 1)
An undercoat solution consisting of 3-glycidoxypropyltrimethoxysilane, phenyltriethoxysilane, hydrochloric acid, aluminum acetylacetonate, and ethanol on a polyethylene naphthalate film having a thickness of 63 μm and a surface roughness Ra = 1.4 nm is obtained by gravure coating. After coating, drying and curing were performed at 100 ° C., and an undercoat layer made of a silicon resin having a thickness of 1.0 μm was formed. A coating liquid obtained by mixing a silica sol having a particle diameter of 25 nm and the above-described undercoat liquid was applied on the undercoat layer by a gravure coating method, and protrusions having a height of 15 nm were formed on the undercoat layer at a density of 10 pieces / μm ² . This undercoat layer was formed on both sides of the support film. This raw fabric is installed in a web sputtering apparatus, conveyed while adhering the film onto a water-cooled can, and a gas barrier layer made of C is formed with a thickness of 30 nm on the undercoat layer by a DC magnetron sputtering method. An underlayer having a thickness of 20 nm is formed under an Ar pressure of 20 mTorr (2.7 Pa), and a magnetic layer made of (Co ₇₀ —Pt ₂₀ —Cr ₁₀ ) ₈₈ — (SiO ₂ ) ₁₂ is formed into an Ar pressure of 20 mTorr ( It was formed with a thickness of 20 nm under the conditions of 2.7 Pa). The gas barrier layer, underlayer, and magnetic layer were formed on both sides of the film. Next, this raw fabric was set in a web type protective layer film forming apparatus, ethylene gas and argon gas were used as reaction gases, and the chamber pressure was 0.5 mTorr and the present ion beam deposition method was used: C: H = 68 : A DLC protective layer having a 32 mol ratio was formed to a thickness of 8 nm. At this time, a voltage of 1500 V was applied to the anode. This protective layer was also formed on both sides of the film. Next, a gravure coating solution obtained by dissolving a perfluoropolyether lubricant having a hydroxyl group at the molecular end on the surface of the protective layer (FOMBLIN Z-DOL manufactured by Montefluos) in a fluorine lubricant (HFE-7200 manufactured by Sumitomo 3M) This was applied by a method to form a 1 nm thick lubricating layer. This lubricating layer was also formed on both sides of the film. Next, a 3.7 inch size disk was punched out from the original fabric, tape burnished, and then incorporated into a resin cartridge (for Zip 100 manufactured by Fuji Photo Film Co., Ltd.) to produce a flexible disk.

(Example 2)
In Example 1, a disk-shaped sheet having a diameter of 130 mm was punched from the original fabric on which the undercoat layer was formed, and this was fixed to a circular ring. A gas barrier layer, an underlayer, and a magnetic layer having the same composition as in Example 1 are formed on both sides of the sheet using a batch-type sputtering apparatus, and the same ion beam as in Example 1 is formed on the protective layer film forming apparatus. A DLC protective layer was formed by a deposition method. The same lubricating layer as in Example 1 was formed on this sheet by dip coating. Next, a 3.7 inch size disk was punched out from this sheet, tape burnished, and then incorporated into a resin cartridge (for Zip 100 manufactured by Fuji Photo Film Co., Ltd.) to produce a flexible disk.

(Example 3)
In Example 1, after forming a DLC protective layer 4 nm using a hydrocarbon gas, argon gas as a reactive gas, a 2 nm DLC protective layer using a hydrocarbon gas, argon gas, nitrogen gas as a reactive gas is formed. A flexible disk similar to that of Example 1 was prepared except that.

Example 4
A hard disk was formed in the same manner as in Example 2 except that a mirror-polished 3.7 inch glass substrate was used as the support in Example 2. However, no undercoat was applied and it was not incorporated into the cartridge.

(Example 5)
In Example 1, a polyaramid film having a thickness of 9 μm and a surface roughness of 1.0 μm was used as a support, a gas barrier layer, an underlayer, a magnetic layer, and a protective layer were formed on one side of the support, and carbon black was formed on the other side. A back coat layer was formed to produce a magnetic tape having a width of 8 mm.
(Comparative Example 1)
A flexible disk was produced in the same manner as in Example 1 except that the protective layer was not formed in Example 1.

(Comparative Example 2)
A flexible disk was produced in the same manner as in Example 1 except that the protective layer was a carbon film formed by sputtering in Example 1.

(Comparative Example 3)
A flexible disk was produced in the same manner as in Example 1 except that the protective layer was a DLC film formed by RF plasma CVD in Example 1. At this time, a bias voltage of −500 V was applied to the magnetic layer.
(Comparative Example 4)
A flexible disk was produced in the same manner as in Comparative Example 3 except that the magnetic layer was changed to CoPtCr in Comparative Example 3.

The above samples were evaluated by the following, and the results are shown in Table 1.
(Evaluation)
(1) Magnetic properties The coercive force Hc was measured by VSM.
(2) Recording / reproduction characteristics Using a GMR head having a reproduction track width of 0.25 μm and a reproduction gap of 0.09 μm, recording / reproduction was performed at a linear recording density of 400 kFCI, and a reproduction signal / noise (S / N) ratio was measured. At this time, the rotational speed was 4200 rpm and the radial position was 35 mm. In addition, the S / N value showed the increase / decrease from the value on the basis of the value in Example 1.
(3) Running durability During the S / N measurement, the time until media scraping was measured. However, the maximum measurement time was 300 hours.
(4) Evaluation of DLC protective layer film quality by Raman spectroscopy The protective layer film quality was evaluated by the ID / IG ratio and B / A obtained from the Raman spectral spectrum.
Using a Raman spectrometer manufactured by Renyshaw Inc., a Raman spectrum in the 1000 to 2000 cm ⁻¹ range at the time of Ar laser irradiation was measured, waveform separation was performed for the D peak and G peak, and the peak intensity ratio (ID / IG) was determined. Further, the baseline slope excluding the peak portion was used as the background, and the ratio B / A of the intensity B of the G peak including the background and the intensity A of the G peak not including the background was determined.
(5) Surface resistivity evaluation The electrical resistivity was measured using a 4-terminal resistivity meter.

  As can be seen from the above results, it can be seen that the flexible disk, hard disk and magnetic tape of the present invention have achieved sufficient running durability at the time of high-density recording and reproduction by the GMR head. Moreover, it can be seen from the result of (4) that a sufficiently hard protective layer can be formed. On the other hand, in Comparative Example 1 in which the protective layer was not formed and in Comparative Example 2 using the sputtered carbon protective layer, media scraping occurred in a short time after head loading. When the protective layer is formed by the RF plasma CVD method, a hard protective layer can be formed when CoPtCr having a low electrical resistivity is used for the magnetic layer as in Comparative Example 4, but as in Comparative Example 3. When a granular magnetic layer is used, the result of (4) shows that the polymer component ratio is high, the film is not sufficiently hard, and the number of defects by visual observation under strong halogen light irradiation is relatively increased. Therefore, it is estimated that early media scraping occurred because the frictional force at the time of head-media contact increased.

Claims (6)

A magnetic recording medium in which at least one magnetic layer having a granular structure and a protective layer are formed in this order on at least one surface of a support, wherein the protective layer is a hard carbon film formed by an ion beam deposition method. , the ratio of the intensity of the D peak having a peak in the range of the intensity (IG) and 1350～1430Cm ^-1 of G peak having a peak in the range of 1500～1600Cm ^-1 in the Raman spectrum by the Raman spectroscopy (ID) (ID / IG) is from 0.5 to 1.0.   The hard carbon film formed by the ion beam deposition method has a gas introduction port capable of introducing at least a hydrocarbon-based gas, and uses a gridless ion source having a structure capable of applying a magnetic field and a voltage. The magnetic recording medium according to claim 1, wherein the magnetic recording medium is formed.   The magnetic recording medium according to claim 1, wherein the support is a flexible polymer support.   4. The magnetic recording medium according to claim 1, wherein the protective layer has a multilayer structure, and the uppermost protective layer is a hard carbon film to which nitrogen is added.   The magnetic recording medium according to claim 1, wherein an underlayer containing at least Ru is provided between the support and the magnetic layer.   A method of manufacturing a magnetic recording medium in which at least a magnetic layer having a granular structure and a protective layer are formed in this order on at least one surface of a support, wherein the protective layer can introduce at least a hydrocarbon-based gas. It is formed by an ion beam deposition method using a gridless ion source having a gas inlet and a structure capable of applying a magnetic field and a voltage, and a magnetic field applied to the ion source is 0.03 T (300 gauss) to 1 T. 5. The method of manufacturing a magnetic recording medium according to claim 1, wherein the voltage is in the range of 100 to 3000 V in the range of (10000 Gauss).