US20240034951A2 - Fluorine-containing ether compound, lubricant for magnetic recording medium, and magnetic recording medium - Google Patents

Fluorine-containing ether compound, lubricant for magnetic recording medium, and magnetic recording medium Download PDF

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US20240034951A2
US20240034951A2 US17/630,639 US202017630639A US2024034951A2 US 20240034951 A2 US20240034951 A2 US 20240034951A2 US 202017630639 A US202017630639 A US 202017630639A US 2024034951 A2 US2024034951 A2 US 2024034951A2
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formula
layer
fluorine
magnetic recording
ether compound
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US20220259513A1 (en
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Naoya Fukumoto
Daisuke Yagyu
Tsuyoshi Kato
Katsumi Murofushi
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Resonac Corp
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Resonac Corp
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Publication of US20240034951A2 publication Critical patent/US20240034951A2/en
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G65/00—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule
    • C08G65/002—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule from unsaturated compounds
    • C08G65/005—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule from unsaturated compounds containing halogens
    • C08G65/007—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule from unsaturated compounds containing halogens containing fluorine
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
    • C10M107/00—Lubricating compositions characterised by the base-material being a macromolecular compound
    • C10M107/38—Lubricating compositions characterised by the base-material being a macromolecular compound containing halogen
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/62—Record carriers characterised by the selection of the material
    • G11B5/72—Protective coatings, e.g. anti-static or antifriction
    • G11B5/725—Protective coatings, e.g. anti-static or antifriction containing a lubricant, e.g. organic compounds
    • G11B5/7253—Fluorocarbon lubricant
    • G11B5/7257—Perfluoropolyether lubricant
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C43/00—Ethers; Compounds having groups, groups or groups
    • C07C43/02—Ethers
    • C07C43/03—Ethers having all ether-oxygen atoms bound to acyclic carbon atoms
    • C07C43/04—Saturated ethers
    • C07C43/13—Saturated ethers containing hydroxy or O-metal groups
    • C07C43/137—Saturated ethers containing hydroxy or O-metal groups containing halogen
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G65/00—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule
    • C08G65/02—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule from cyclic ethers by opening of the heterocyclic ring
    • C08G65/32—Polymers modified by chemical after-treatment
    • C08G65/329—Polymers modified by chemical after-treatment with organic compounds
    • C08G65/331—Polymers modified by chemical after-treatment with organic compounds containing oxygen
    • C08G65/3311—Polymers modified by chemical after-treatment with organic compounds containing oxygen containing a hydroxy group
    • C08G65/3312—Polymers modified by chemical after-treatment with organic compounds containing oxygen containing a hydroxy group acyclic
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G65/00—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule
    • C08G65/02—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule from cyclic ethers by opening of the heterocyclic ring
    • C08G65/32—Polymers modified by chemical after-treatment
    • C08G65/329—Polymers modified by chemical after-treatment with organic compounds
    • C08G65/331—Polymers modified by chemical after-treatment with organic compounds containing oxygen
    • C08G65/3311—Polymers modified by chemical after-treatment with organic compounds containing oxygen containing a hydroxy group
    • C08G65/3318—Polymers modified by chemical after-treatment with organic compounds containing oxygen containing a hydroxy group heterocyclic
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/62—Record carriers characterised by the selection of the material
    • G11B5/72—Protective coatings, e.g. anti-static or antifriction
    • G11B5/725—Protective coatings, e.g. anti-static or antifriction containing a lubricant, e.g. organic compounds
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/62—Record carriers characterised by the selection of the material
    • G11B5/72—Protective coatings, e.g. anti-static or antifriction
    • G11B5/725—Protective coatings, e.g. anti-static or antifriction containing a lubricant, e.g. organic compounds
    • G11B5/7253—Fluorocarbon lubricant
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/62—Record carriers characterised by the selection of the material
    • G11B5/73—Base layers, i.e. all non-magnetic layers lying under a lowermost magnetic recording layer, e.g. including any non-magnetic layer in between a first magnetic recording layer and either an underlying substrate or a soft magnetic underlayer
    • G11B5/739—Magnetic recording media substrates
    • G11B5/73923—Organic polymer substrates
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
    • C10M2213/00—Organic macromolecular compounds containing halogen as ingredients in lubricant compositions
    • C10M2213/04—Organic macromolecular compounds containing halogen as ingredients in lubricant compositions obtained from monomers containing carbon, hydrogen, halogen and oxygen
    • C10M2213/043—Organic macromolecular compounds containing halogen as ingredients in lubricant compositions obtained from monomers containing carbon, hydrogen, halogen and oxygen used as base material
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
    • C10M2213/00—Organic macromolecular compounds containing halogen as ingredients in lubricant compositions
    • C10M2213/06—Perfluoro polymers
    • C10M2213/0606—Perfluoro polymers used as base material
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10N—INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS
    • C10N2020/00—Specified physical or chemical properties or characteristics, i.e. function, of component of lubricating compositions
    • C10N2020/01—Physico-chemical properties
    • C10N2020/04—Molecular weight; Molecular weight distribution
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10N—INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS
    • C10N2030/00—Specified physical or chemical properties which is improved by the additive characterising the lubricating composition, e.g. multifunctional additives
    • C10N2030/06—Oiliness; Film-strength; Anti-wear; Resistance to extreme pressure
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10N—INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS
    • C10N2040/00—Specified use or application for which the lubricating composition is intended
    • C10N2040/14—Electric or magnetic purposes
    • C10N2040/18—Electric or magnetic purposes in connection with recordings on magnetic tape or disc
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10N—INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS
    • C10N2050/00—Form in which the lubricant is applied to the material being lubricated
    • C10N2050/023—Multi-layer lubricant coatings
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10N—INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS
    • C10N2050/00—Form in which the lubricant is applied to the material being lubricated
    • C10N2050/023—Multi-layer lubricant coatings
    • C10N2050/025—Multi-layer lubricant coatings in the form of films or sheets

Definitions

  • the present invention relates to a fluorine-containing ether compound preferable for application as a lubricant for magnetic recording media, a lubricant for a magnetic recording medium containing the same, and a magnetic recording medium.
  • magnetic recording media having a recording layer formed on a substrate and a protective layer made of carbon or the like formed on the recording layer.
  • the protective layer protects information recorded in the recording layer and enhances the sliding properties of a magnetic head.
  • the protective layer provided on the recording layer is not sufficient for magnetic recording media to obtain sufficient durability. Therefore, it is common to form a lubricating layer on the surface of the protective layer by applying a lubricant.
  • lubricants containing a compound having a polar group such as a hydroxy group at a terminal of a fluorine-based polymer having a repeating structure containing CF 2 have been proposed.
  • Patent Document 1 discloses a fluoropolyether compound wherein two or more perfluoropolyethers are bonded by ether bonds respectively to an aliphatic hydrocarbon chain having 4 to 10 carbon atoms which is located at the center of a molecule thereof.
  • Patent Document 2 discloses a compound in which a substituent is disposed in which a plurality of hydroxyl groups are present at both terminal portions and the shortest distance between the hydroxyl groups is three atoms or more.
  • the present invention has been made in consideration of the above-described circumstances, and an objective of the present invention is to provide a fluorine-containing ether compound that is capable of forming lubricating layers, which have excellent wear resistance and can prevent pickup in spite of a thin thickness, and can be preferably used as a material for lubricants for magnetic recording media.
  • Another objective of the present invention is to provide a lubricant for a magnetic recording medium containing the fluorine-containing ether compound of the present invention.
  • Still another objective of the present invention is to provide a magnetic recording medium having a lubricating layer containing the fluorine-containing ether compound of the present invention and having excellent reliability and durability.
  • the present inventors repeated intensive studies to solve the above-described problem.
  • the present invention relates to the following matters.
  • a compound of a first aspect of the present invention is the following compound.
  • n is an integer of 2 to 6
  • R 1 is a perfluoropolyether chain
  • R 2 is —OCH 2 CH(OH)CH 2 O(CH 2 ) m OH (m in the formula is an integer of 2 to 4).
  • the compound of the first aspect of the present invention preferably has characteristics to be described in the following [2] to [4]. Two or more of the following characteristics are also preferably combined together.
  • a second aspect of the present invention is the following lubricant for a magnetic recording medium.
  • a third aspect of the present invention is the following magnetic recording medium.
  • the fluorine-containing ether compound of the present invention is preferably used as a material for lubricants for magnetic recording media.
  • the lubricant for a magnetic recording medium of the present invention contains the fluorine-containing ether compound of the present invention and is thus capable of forming lubricating layers capable of obtaining excellent wear resistance and preventing pickup, in spite of a thin thickness.
  • the magnetic recording medium of the present invention is provided with a lubricating layer which has excellent wear resistance and can prevent pickup, and thus has excellent reliability and durability.
  • FIG. 1 is a schematic cross-sectional view showing a preferable example of an embodiment of a magnetic recording medium of the present invention.
  • a fluorine-containing ether compound a fluorine-containing ether compound, a lubricant for a magnetic recording medium (hereinafter, abbreviated as “lubricant” in some cases) and a magnetic recording medium of the present invention will be described in detail.
  • lubricant a fluorine-containing ether compound, a lubricant for a magnetic recording medium (hereinafter, abbreviated as “lubricant” in some cases) and a magnetic recording medium of the present invention will be described in detail.
  • lubricant a fluorine-containing ether compound, a lubricant for a magnetic recording medium (hereinafter, abbreviated as “lubricant” in some cases) and a magnetic recording medium of the present invention will be described in detail.
  • the present invention is not limited only to an embodiment to be described below.
  • a fluorine-containing ether compound of the present embodiment is represented by the following formula (1).
  • n is an integer of 2 to 6
  • R 1 is a perfluoropolyether chain
  • R 2 is —OCH 2 CH(OH)CH 2 O(CH 2 ) m OH (m in the formula is an integer of 2 to 4).
  • the fluorine-containing ether compound of the present embodiment has two perfluoropolyether chains represented by R 1 (hereinafter, abbreviated as “PFPE chain” in some cases).
  • the PFPE chain coats the surface of a protective layer and also imparts lubricity to a lubricating layer to reduce a friction force between a magnetic head and the protective layer when the lubricating layer is formed by applying a lubricant containing the fluorine-containing ether compound onto the protective layer.
  • a linking group (—CH(OH)CH 2 OCH 2 —) including a hydroxy group (—OH) is bonded respectively to both terminals of a hydrocarbon chain (—(CH 2 ) n —, (n in the formula is an integer of 2 to 6)), which consists of 2 to 6 methylene groups and is located at the center of a molecule thereof.
  • the hydroxy group contributes to an improvement of adhesion between a protective layer and a fluorine-containing ether compound included in the lubricating layer, and the distance between a hydroxy group included in one linking group and a hydroxy group included in the other linking group is appropriate due to the hydrocarbon chain located between the two linking groups.
  • the fluorine-containing ether compound has appropriate hardness. Therefore, lubricating layers having excellent coatability and wear resistance can be obtained by using a lubricant containing the fluorine-containing ether compound represented by the formula (1).
  • a terminal group represented by R 2 is respectively bonded to a terminal of the two PFPE chains represented by R 1 wherein the terminal is located on the opposite side of the linking group including a hydroxyl group.
  • the terminal group represented by R 2 is —OCH 2 CH(OH)CH 2 O(CH 2 ) m OH (m in the formula is an integer of 2 to 4).
  • Two hydroxy groups (—OH) that are included in each of the two terminal groups represented by R 2 closely attach the fluorine-containing ether compound and the protective layer in the lubricating layer containing the fluorine-containing ether compound of the present embodiment, and thereby suppress pickup.
  • the two hydroxy groups bond to different carbon atoms respectively, and the carbon atoms to which the hydroxy groups bond are bonded to each other through a linking group including an oxygen atom (a linking group including —O— (ether bond)).
  • the linking group including the ether bond imparts flexibility to the terminal group represented by R 2 .
  • the lubricating layer containing the fluorine-containing ether compound of the present embodiment is easily adsorbed to the protective film and is excellent in terms of adhesion between the lubricating layer and the protective layer.
  • a lubricant containing the fluorine-containing ether compound of the present embodiment is capable of coating the surface of the protective layer at a high coating rate in spite of a thin thickness and capable of forming a lubricating layer which has excellent wear resistance and can suppress pickup.
  • R 1 is the perfluoropolyether chain (PFPE chain), and two R 1 included in the fluorine-containing ether compound represented by the formula (1) are the same.
  • R 1 is not particularly limited and can be appropriately selected depending on performance or the like required for lubricants containing the fluorine-containing ether compound.
  • R 1 is preferably represented by any one of the following formula (2) to formula (4).
  • R 1 is represented by any one of the formula (2) to formula (4), the synthesis of the fluorine-containing ether compound is easy, which is preferable.
  • the ratio of the number of oxygen atoms (the number of the ether bonds (—O—)) to the number of carbon atoms in the perfluoropolyether chain is appropriate. Therefore, a fluorine-containing ether compound having appropriate hardness is obtained. Therefore, the fluorine-containing ether compound applied onto the protective layer is less likely to aggregate on the protective layer, and it is possible to form a lubricating layer having a thinner thickness at a sufficient coating rate. In addition, in a case where R 1 is represented by any one of the formula (2) to formula (4), the fluorine-containing ether compound becomes capable of providing lubricating layers having favorable wear resistance.
  • the arrangement sequence of (CF 2 —CF 2 —O) and (CF 2 —O), which are repeating units, is not particularly limited.
  • the number p of (CF 2 —CF 2 —O)'s and the number q of (CF 2 —O)'s may be equal to each other or may be different from each other.
  • the formula (2) may include any of a random copolymer, a block copolymer, and an alternating copolymer composed of the monomer units (CF 2 —CF 2 —O) and (CF 2 —O).
  • R 1 in the formula (1) is the formula (2)
  • p that indicates the average degree of polymerization is 1 to 30, preferably 1 to 20 and more preferably 1 to 15.
  • p may be 3 to 7 or 7 to 13 as necessary.
  • q that indicates the average degree of polymerization is 0 to 30, preferably 0 to 20 and more preferably 0 to 15.
  • q may be 3 to 7 or 7 to 13 as necessary.
  • p is preferably 1 to 17.
  • the number-average molecular weight of the fluorine-containing ether compound of the present embodiment is likely to be within a preferable range.
  • r is preferably 2 to 20 and more preferably 3 to 10.
  • the number-average molecular weight of the fluorine-containing ether compound of the present embodiment is likely to be within a preferable range.
  • s is preferably 2 to 15 and more preferably 2 to 8.
  • n is an integer of 2 to 6, the distance between the hydroxy groups which are present at both terminals of the hydrocarbon chain, which consists of methylene groups and is located at the center of a molecule, is in an appropriate range.
  • the aforementioned n is preferably 4 to 6 as the distance between the hydroxy groups becomes more appropriate.
  • R 2 is —OCH 2 CH(OH)CH 2 O(CH 2 ) m OH (m in the formula is an integer of 2 to 4).
  • the fluorine-containing ether compound represented by the formula (1) is, specifically, preferably any one of the compounds represented by the formulae (A) to (F).
  • p, q, r and s in the formulae (A) to (F) are values indicating the average degree of polymerization and thus do not necessarily need to be integers.
  • n 4
  • R 1 is the formula (2)
  • m in R 2 is 2.
  • n 4
  • R 1 is the formula (3)
  • m in R 2 is 2.
  • n 4
  • R 1 is the formula (4)
  • m in R 2 is 2.
  • n 6
  • R 1 is the formula (2)
  • m in R 2 is 2.
  • n 4
  • R 1 is the formula (2)
  • m in R 2 is 3.
  • the compound represented by the formula (1) is any one of the compounds represented by the formulae (A) to (F), a raw material is easy to procure, and furthermore, it is possible to form lubricating layers from which superior wear resistance can be obtained and pickup can be furthermore suppressed in spite of a thin thickness, which is preferable.
  • the number-average molecular weight (Mn) of the fluorine-containing ether compound of the present embodiment is preferably within a range of 500 to 10000. When the number-average molecular weight is 500 or more, the evaporation of lubricants containing the fluorine-containing ether compound of the present embodiment is less likely to occur, and it is possible to prevent lubricants from being evaporated and transferred to a magnetic head.
  • the number-average molecular weight of the fluorine-containing ether compound is more preferably 1000 or more.
  • the viscosity of the fluorine-containing ether compound becomes appropriate, and it is possible to easily form lubricating layers having a thin thickness by applying lubricants containing the fluorine-containing ether compound.
  • the number-average molecular weight of the fluorine-containing ether compound is preferably 3000 or less in order to obtain a viscosity that makes lubricants to which the fluorine-containing ether compound is applied easily handleable.
  • the number-average molecular weight (Mn) of the fluorine-containing ether compound is a value measured by 1 H-NMR and 19 F-NMR, specifically, 1 H-NMR and 19 F-NMR with AVANCE 111400 manufactured by Bruker BioSpin Group.
  • NMR nuclear magnetic resonance
  • the peak of hexafluorobenzene was set to ⁇ 164.7 ppm
  • the peak of acetone was set to 2.2 ppm.
  • a method for producing the fluorine-containing ether compound of the present embodiment is not particularly limited, and the fluorine-containing ether compound can be produced using a well-known conventional production method.
  • the fluorine-containing ether compound of the present embodiment can be produced using, for example, a production method to be described below.
  • n is an integer of 2 to 6, and R 1 is the same as in the formula (1).
  • Examples of the aliphatic hydrocarbon diepoxide having 6 to 10 carbon atoms that is used in the addition reaction include 1,5-hexadiene diepoxide, 1,6-heptadiene diepoxide, 1,7-octadiene diepoxide, 1,8-nonadiene diepoxide, 1,9-decadiene diepoxide and the like.
  • the compound represented by the formula (1-1) and epichlorohydrin or epibromohydrin are reacted with each other, thereby generating perfluoropolyether having an epoxy group at both ends thereof. Furthermore, the perfluoropolyether having an epoxy group at both ends thereof and any one selected from ethylene glycol, 1,3-propanediol and 1,4-butanediol are reacted with each other.
  • a compound obtained as described above can be separated using, for example, a method in which column chromatography is used.
  • the fluorine-containing ether compound represented by the formula (1) can be obtained by the above-described method.
  • the fluorine-containing ether compound of the present embodiment is a compound represented by the formula (1). Therefore, when a lubricating layer is formed on a protective layer using a lubricant containing this fluorine-containing ether compound, the surface of the protective layer is coated with the two PFPE chains represented by R 1 in the formula (1), and a friction force between a magnetic head and the protective layer is reduced.
  • excellent coatability and wear resistance can be obtained, as the distance between the hydroxy groups included in the two linking groups (—CH(OH)CH 2 OCH 2 —) is appropriate and each linking group includes an ether bond (—O—).
  • the fluorine-containing ether compound of the present embodiment is closely attached onto the protective layer due to bonds between the two hydroxy groups that are included in each of the two terminal groups represented by R 2 and the protective layer. Furthermore, the two hydroxy groups that are included in the terminal group represented by R 2 bond to different carbon atoms, and the carbon atoms to which the hydroxy groups bond are bonded to each other through a linking group including an oxygen atom. Therefore, the lubricating layer containing the fluorine ether compound of the present embodiment has favorable flexibility. Therefore, the lubricating layer containing the fluorine ether compound of the present embodiment is easily adsorbed to the protective film and has excellent adhesion to the protective layer.
  • the lubricating layer and the protective layer are strongly bonded to each other, and a lubricating layer which has excellent wear resistance and can suppress pickup can be obtained.
  • a lubricant for a magnetic recording medium of the present embodiment contains the fluorine-containing ether compound represented by the formula (1).
  • the lubricant of the present embodiment can be used after being mixed as necessary with a well-known material that is used as a material for lubricants as long as characteristics attributed to the fluorine-containing ether compound represented by the formula (1) contained in the lubricant are not impaired.
  • a well-known material examples include FOMBLIN (registered trademark) ZDIAC, FOMBLIN ZDEAL, FOMBLIN AM-2001 (all manufactured by Solvay Solexis), Moresco A20H (manufactured by Moresco Corporation) and the like.
  • the number-average molecular weight of the well-known material that is used by being mixed with the lubricant of the present embodiment is preferably 1000 to 10000.
  • the content of the fluorine-containing ether compound represented by the formula (1) in the lubricant of the present embodiment is preferably 50 mass % or more and more preferably 70 mass % or more.
  • the content may be 80 mass % or more, 90 mass % or more or 95 mass % or more.
  • the lubricant of the present embodiment contains the fluorine-containing ether compound represented by the formula (1) and is thus capable of coating the surface of protective layers at a high coating rate in spite of a thin thickness and capable of forming lubricating layers having excellent adhesion to protective layers. Therefore, according to the lubricant of the present embodiment, lubricating layers which have excellent wear resistance and can suppress pickup can be obtained in spite of a thin thickness.
  • a magnetic recording medium of the present embodiment is sequentially provided with at least a magnetic layer, a protective layer and a lubricating layer on a substrate.
  • a single underlayer or two or more underlayers can be provided as necessary between the substrate and the magnetic layer.
  • FIG. 1 is a schematic cross-sectional view showing an embodiment of the magnetic recording medium of the present invention.
  • a magnetic recording medium 10 of the present embodiment has a structure in which an adhesive layer 12 , a soft magnetic layer 13 , a first underlayer 14 , a second underlayer 15 , a magnetic layer 16 , a protective layer 17 and a lubricating layer 18 are sequentially provided on a substrate 11 .
  • the substrate 11 can be arbitrarily selected, and it is possible to use, for example, a non-magnetic substrate or the like wherein a NiP or NiP alloy film is formed on a base made of a metal or alloy material such as Al or an Al alloy.
  • a non-magnetic substrate made of a non-metal material such as glass, ceramic, silicon, silicon carbide, carbon or resin may be used, and a non-magnetic substrate wherein a NiP or NiP alloy film is formed on a base made of this non-metal material may be used.
  • the adhesive layer 12 prevents the progress of corrosion of the substrate 11 which may occur in a case where the substrate 11 and the soft magnetic layer 13 , which is provided on the adhesive layer 12 , are disposed in direct contact with each other.
  • the material of the adhesive layer 12 can be arbitrarily selected and can be appropriately selected from, for example, Cr, a Cr alloy, Ti, a Ti alloy, CrTi, NiAl, an AlRu alloy and the like.
  • the adhesive layer 12 can be formed by, for example, a sputtering method.
  • the soft magnetic layer 13 can be arbitrarily selected and preferably has a structure in which, for example, a first soft magnetic film, an interlayer made of a Ru film and a second soft magnetic film are sequentially laminated. That is, the soft magnetic layer 13 preferably has a structure in which the interlayer made of a Ru film is sandwiched between two soft magnetic films and thereby the soft magnetic films on and under the interlayer are antiferromagnetically coupled (AFC).
  • AFC antiferromagnetically coupled
  • Examples of the material of the first soft magnetic film and the second soft magnetic film include a CoZrTa alloy, a CoFe alloy and the like.
  • any of Zr, Ta and Nb is preferably added. This accelerates the amorphization of the first soft magnetic film and the second soft magnetic film, makes it possible to improve the orientation of the first underlayer (seed layer) and makes it possible to reduce the flying height of a magnetic head.
  • the soft magnetic layer 13 can be formed by, for example, a sputtering method.
  • the first underlayer 14 is a layer for controlling the orientations or crystal sizes of the second underlayer 15 and the magnetic layer 16 that are provided on the first underlayer 14 .
  • Examples of the first underlayer 14 include a Cr layer, a Ta layer, a Ru layer, an alloy layer of CrMo, CoW, CrW, CrV or CrTi, and the like.
  • the first underlayer 14 can be formed by, for example, a sputtering method.
  • the second underlayer 15 is a layer to control the orientation of the magnetic layer 16 to be favorable.
  • the second underlayer 15 is preferably a Ru or Ru alloy layer.
  • the second underlayer 15 may be a single layer or may be composed of a plurality of layers. In a case where the second underlayer 15 is composed of a plurality of layers, all of the layers may be made of the same material or at least one layer may be made of a different material.
  • the second underlayer 15 can be formed by, for example, a sputtering method.
  • the magnetic layer 16 is made of a magnetic film in which the easy magnetization axis is directed in a perpendicular or parallel direction with respect to the substrate surface.
  • the magnetic layer 16 is a layer containing Co and Pt and may be a layer further containing an oxide and/or Cr, B, Cu, Ta, Zr or the like in order to improve SNR characteristics.
  • Examples of the oxide that is contained in the magnetic layer 16 include SiO 2 , SiO, Cr 2 O 3 , CoO, Ta 2 O 3 , TiO 2 and the like.
  • the magnetic layer 16 may be composed of a single layer or may be composed of a plurality of magnetic layers made of materials with different compositions.
  • the first magnetic layer 16 is preferably a granular structure made of a material containing Co, Cr and Pt and further containing an oxide.
  • oxides of Cr, Si, Ta, Al, Ti, Mg, Co or the like are preferably used.
  • TiO 2 , Cr 2 O 3 , SiO 2 and the like can be preferably used.
  • the first magnetic layer is preferably composed of a composite oxide to which two or more oxides have been added.
  • Cr 2 O 3 —SiO 2 , Cr 2 O 3 —TiO 2 , SiO 2 —TiO 2 and the like can be preferably used.
  • the first magnetic layer may contain, in addition to Co, Cr, Pt and the oxide, one or more elements selected from B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb, Ru and Re.
  • the second magnetic layer the same material as the first magnetic layer can be used.
  • the second magnetic layer is preferably a granular structure.
  • the third magnetic layer preferably has a non-granular structure made of a material containing Co, Cr and Pt but containing no oxides.
  • the third magnetic layer may contain, in addition to Co, Cr, and Pt, one or more elements selected from B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb, Ru, Re and Mn.
  • a non-magnetic layer is preferably provided between the magnetic layers adjacent to each other.
  • the magnetic layer 16 is composed of three layers of the first magnetic layer, the second magnetic layer and the third magnetic layer, it is preferable to provide a non-magnetic layer between the first magnetic layer and the second magnetic layer and a non-magnetic layer between the second magnetic layer and the third magnetic layer.
  • X1 represents one or more elements selected from Pt, Ta, Zr, Re, Ru, Cu, Nb, Ni, Mn, Ge, Si, O, N, W, Mo, Ti, V and B) and the like.
  • an alloy material containing an oxide, a metallic nitride or a metallic carbide is preferably used.
  • the oxide for example, SiO 2 , Al 2 O 3 , Ta 2 O 5 , Cr 2 O 3 , MgO, Y 2 O 3 , TiO 2 and the like can be used.
  • the metallic nitride for example, AlN, Si 3 N 4 , TaN, CrN and the like can be used.
  • metallic carbide for example, TaC, BC, SiC and the like can be used.
  • the non-magnetic layer can be formed by, for example, a sputtering method.
  • the magnetic layer 16 is preferably a magnetic layer of perpendicular magnetic recording in which the easy magnetization axis is directed in a perpendicular direction with respect to the substrate surface in order to realize a higher recording density.
  • the magnetic layer 16 may be a magnetic layer of longitudinal magnetic recording.
  • the magnetic layer 16 may be formed by any well-known conventional method such as a deposition method, an ion beam sputtering method or a magnetron sputtering method.
  • the magnetic layer 16 is normally formed by a sputtering method.
  • the protective layer 17 protects the magnetic layer 16 .
  • the protective layer 17 may be composed of a single layer or may be composed of a plurality of layers.
  • As the material of the protective layer 17 carbon, nitrogen-containing carbon, silicon carbide and the like can be exemplified.
  • a carbon-based protective layer can be preferably used, and, in particular, an amorphous carbon protective layer is preferred.
  • the protective layer 17 is a carbon-based protective layer, the interaction with the hydroxy groups that are included in the fluorine-containing ether compound in the lubricating layer 18 is further enhanced, which is preferable.
  • the adhesive force between the carbon-based protective layer and the lubricating layer 18 can be controlled by forming the carbon-based protective layer with hydrogenated carbon and/or nitrogenated carbon and adjusting the hydrogen content and/or the nitrogen content in the carbon-based protective layer.
  • the hydrogen content in the carbon-based protective layer is preferably 3 to 20 atom % when measured by the hydrogen forward scattering method (HFS).
  • the nitrogen content in the carbon-based protective layer is preferably 4 to 15 atom % when measured by X-ray photoelectron spectroscopy (XPS).
  • the hydrogen and/or nitrogen that are contained in the carbon-based protective layer do not need to be uniformly contained throughout the entire carbon-based protective layer.
  • the carbon-based protective layer is preferably formed as a composition gradient layer in which nitrogen is contained in the lubricating layer 18 side of the protective layer 17 and hydrogen is contained in the magnetic layer 16 side of the protective layer 17 .
  • the adhesive forces between the magnetic layer 16 and the carbon-based protective layer and between the lubricating layer 18 and the carbon-based protective layer further improve.
  • the film thickness of the protective layer 17 is preferably set to 1 nm to 7 nm. When the film thickness of the protective layer 17 is 1 nm or more, the performance of the protective layer 17 can be sufficiently obtained.
  • the film thickness of the protective layer 17 is preferably 7 nm or less from the viewpoint of reduction in the thickness of the protective layer 17 .
  • the protective layer 17 As a method for forming the protective layer 17 , it is possible to use a sputtering method in which a carbon-containing target material is used, a chemical vapor deposition (CVD) method in which a hydrocarbon raw material such as ethylene or toluene is used, an ion beam deposition (IBD) method and the like.
  • CVD chemical vapor deposition
  • IBD ion beam deposition
  • the carbon-based protective layer can be formed by, for example, a DC magnetron sputtering method.
  • an amorphous carbon protective layer is preferably formed by a plasma CVD method.
  • the amorphous carbon protective layer formed by the plasma CVD method has a uniform surface with small roughness.
  • the lubricating layer 18 prevents contamination of the magnetic recording medium 10 .
  • the lubricating layer 18 reduces a friction force of a magnetic head of a magnetic recording/reproducing device, which slides on the magnetic recording medium 10 , and thereby improves the durability of the magnetic recording medium 10 .
  • the lubricating layer 18 is formed in contact with the protective layer 17 as shown in FIG. 1 .
  • the lubricating layer 18 contains the above-described fluorine-containing ether compound.
  • the lubricating layer 18 is bonded to the protective layer 17 with a particularly high bonding force. As a result, it becomes easy to obtain the magnetic recording medium 10 in which the surface of the protective layer 17 is coated with the lubricating layer 18 at a high coating rate in spite of a thin thickness thereof, and it is possible to effectively prevent contamination on the surface of the magnetic recording medium 10 .
  • the average film thickness of the lubricating layer 18 can be arbitrarily selected, but is preferably 0.5 nm (5 ⁇ ) to 3 nm (30 ⁇ ) and more preferably 0.5 nm (5 ⁇ ) to 1 nm (10 ⁇ ).
  • the average film thickness of the lubricating layer 18 is 0.5 nm or more, the lubricating layer 18 does not become an island shape or a mesh shape and is formed in a uniform film thickness. Therefore, the surface of the protective layer 17 can be coated with the lubricating layer 18 at a high coating rate.
  • the average film thickness of the lubricating layer 18 is 3 nm or less, it is possible to sufficiently reduce the thickness of the lubricating layer 18 and to sufficiently decrease the flying height of a magnetic head.
  • an environmental substance adsorbed to the surface of the magnetic recording medium 10 passes through voids in the lubricating layer 18 and intrudes into the layer below the lubricating layer 18 .
  • the environmental substance that has intruded into the layer below the lubricating layer 18 is adsorbed and bonded to the protective layer 17 and generates a contamination substance.
  • this contamination substance adheres (transfers) to a magnetic head as a smear to break the magnetic head or degrade the magnetic recording/reproducing characteristics of magnetic recording/reproducing devices.
  • Examples of the environmental substance that generates the contamination substance include a siloxane compound (cyclic siloxane or linear siloxane), an ionic impurity, a hydrocarbon having a relatively high molecular weight such as octacosane, a plasticizer such as dioctyl phthalate and the like.
  • Examples of a metal ion that is contained in the ionic impurity include a sodium ion, a potassium ion and the like.
  • Examples of an inorganic ion that is contained in the ionic impurity include a chlorine ion, a bromine ion, a nitrate ion, a sulfate ion, an ammonium ion and the like.
  • Examples of an organic ion that is contained in the ionic impurity include an oxalate ion, a formate ion and the like.
  • Examples of a method for forming the lubricating layer 18 include a method in which a magnetic recording medium that is not yet fully manufactured and thus includes the individual layers up to the protective layer 17 formed on the substrate 11 is prepared and a solution for forming the lubricating layer is applied and dried on the protective layer 17 .
  • the solution for forming the lubricating layer can be obtained by dispersing and dissolving the lubricant for a magnetic recording medium of the above-described embodiment in a solvent that is arbitrarily selected as necessary and adjusting the viscosity and concentration to be suitable for the application method.
  • Examples of the solvent that is used for the solution for forming the lubricating layer include a fluorine-based solvent such as VERTREL (registered trademark) XF (trade name, manufactured by Dupont-Mitsui Fluorochemicals Co., Ltd.) and the like.
  • VERTREL registered trademark
  • XF trade name, manufactured by Dupont-Mitsui Fluorochemicals Co., Ltd.
  • a method for applying the solution for forming the lubricating layer is not particularly limited, and examples thereof include a spin coating method, a spraying method, a paper coating method, a dipping method and the like.
  • the substrate 11 on which the individual layers up to the protective layer 17 have been formed is immersed into the solution for forming the lubricating layer contained in an immersion vessel of a dip coater.
  • the substrate 11 is lifted from the immersion vessel at a predetermined speed.
  • the solution for forming the lubricating layer is applied to the surface on the protective layer 17 of the substrate 11 .
  • the use of the dipping method makes it possible to uniformly apply the solution for forming the lubricating layer to the surface of the protective layer 17 and makes it possible to form the lubricating layer 18 on the protective layer 17 in a uniform film thickness.
  • a thermal treatment is preferably carried out on the substrate 11 on which the lubricating layer 18 has been formed.
  • the thermal treatment improves the adhesion between the lubricating layer 18 and the protective layer 17 and improves the adhesive force between the lubricating layer 18 and the protective layer 17 .
  • the thermal treatment temperature is preferably set to 100° C. to 180° C. When the thermal treatment temperature is 100° C. or higher, an effect that improves the adhesion between the lubricating layer 18 and the protective layer 17 can be sufficiently obtained. In addition, when the thermal treatment temperature is set to 180° C. or lower, it is possible to prevent thermal decomposition of the lubricating layer 18 .
  • the thermal treatment time is preferably set to 10 to 120 minutes.
  • a treatment of irradiating the lubricating layer 18 on the substrate 11 before the thermal treatment or after the thermal treatment with ultraviolet rays (UV) may be carried out in order to further improve the adhesive force of the lubricating layer 18 to the protective layer 17 .
  • UV ultraviolet rays
  • the magnetic recording medium 10 of the present embodiment is sequentially provided with at least the magnetic layer 16 , the protective layer 17 and the lubricating layer 18 on the substrate 11 .
  • the lubricating layer 18 containing the above-described fluorine-containing ether compound is formed on the protective layer 17 to be in contact with the protective layer 17 .
  • This lubricating layer 18 coats the surface of the protective layer 17 at a high coating rate in spite of a thin thickness. Therefore, in the magnetic recording medium 10 of the present embodiment, intrusion of an environmental substance that generates a contamination substance such as an ionic impurity through voids in the lubricating layer 18 is prevented.
  • the magnetic recording medium 10 of the present embodiment has excellent reliability and durability.
  • a compound represented by the following formula (5) was produced by a method to be described below.
  • t-BuOK (0.35 g) (molecular weight: 112.21, 3.1 mmol) was added to this homogeneous liquid and stirred at 70° C. for 16 hours to be reacted.
  • reaction product was cooled to 25° C., moved to a separatory funnel containing water (30 mL) and extracted twice with ethyl acetate (80 mL). An organic layer thereof was washed with water and dehydrated with anhydrous sodium sulfate. The drying agent was filtered, the filtrate was then concentrated, and the residue was purified by silica gel column chromatography, thereby obtaining a compound represented by the above-described formula (5) (3.2 g).
  • a compound represented by the following formula (8) (3.5 g) was obtained in the same manner as in Example 1 except that fluoropolyether represented by HOCH 2 CF 2 O(CF 2 CF 2 O) p (CF 2 O) q CF 2 CH 2 OH (in the formula, p is 7.0 and q is 0) (number-average molecular weight: 1000, molecular weight distribution: 1.1) was used in place of the fluoropolyether represented by HOCH 2 CF 2 O(CF 2 CF 2 O) p (CF 2 O) q CF 2 CH 2 OH used in Example 1 (in the formula, p is 4.5 and q is 4.5).
  • a compound represented by the following formula (9) (3.2 g) was obtained in the same manner as in Example 1 except that fluoropolyether represented by HOCH 2 CF 2 CF 2 O(CF 2 CF 2 CF 2 O), CF 2 CF 2 CH 2 OH (in the formula, r is 4.5) (number-average molecular weight: 1000, molecular weight distribution: 1.1) was used in place of the fluoropolyether represented by HOCH 2 CF 2 O(CF 2 CF 2 O) p (CF 2 O) q CF 2 CH 2 OH used in Example 1 (in the formula, p is 4.5 and q is 4.5).
  • a compound represented by the following formula (10) (3.2 g) was obtained in the same manner as in Example 1 except that fluoropolyether represented by HOCH 2 CF 2 CF 2 CF 2 O(CF 2 CF 2 CF 2 O) s CF 2 CF 2 CF 2 CH 2 OH (in the formula, s is 3.0) (number-average molecular weight: 1000, molecular weight distribution: 1.1) was used in place of the fluoropolyether represented by
  • a compound represented by the following formula (11) (3.5 g) was obtained in the same manner as in Example 1 except that 1,9-decadiene diepoxide was used in place of 1,7-octadiene diepoxide used in Example 1.
  • a compound represented by the following formula (12) (3.4 g) was obtained in the same manner as in Example 1 except that 1,3-propanediol was used in place of ethylene glycol used in Example 1.
  • a compound represented by the following formula (13) (3.4 g) was obtained in the same manner as in Example 1 except that 1,4-butanediol was used in place of ethylene glycol used in Example 1.
  • a compound represented by the following formula (15) was synthesized by the method described in Patent Document 1.
  • a compound represented by the following formula (16) was synthesized by the method described in Patent Document 2.
  • solutions for forming a lubricating layer were prepared using the compounds obtained in Examples 1 to 7 and Comparative Examples 1 to 3 by a method to be described below.
  • lubricating layers of magnetic recording media were formed using the obtained solutions for forming a lubricating layer by a method to be described below, and magnetic recording media of Examples 1 to 7 and Comparative Examples 1 to 3 were obtained.
  • Magnetic recording media each having an adhesive layer, a soft magnetic layer, a first underlayer, a second underlayer, a magnetic layer and a protective layer sequentially provided on a substrate having a diameter of 65 mm were prepared.
  • a protective layer a carbon layer was used.
  • the solutions for forming a lubricating layer of Examples 1 to 7 and Comparative Examples 1 to 3 were applied onto the protective layers of the magnetic recording media, in which the individual layers up to the protective layer had been formed, by the dipping method.
  • the dipping method was carried out under conditions of an immersion speed of 10 mm/sec, an immersion time of 30 seconds and a lifting speed of 1.2 mm/sec.
  • the magnetic recording media to which the solutions for forming a lubricating layer had been applied were put into a thermostatic chamber (120° C.) and heated for 10 minutes to remove the solvent in the solutions for forming a lubricating layer, thereby forming lubricating layers on the protective layers and obtaining magnetic recording media.
  • the magnetic recording medium in which a lubricating layer had been formed was washed using a method in which the magnetic recording medium was immersed in Vertrel XF as a solvent for 10 minutes and then withdrawn from the solvent. Immersion of the magnetic recording medium in the solvent was performed at a speed of 10 mm/sec, whereas the withdrawal speed was 1.2 mm/sec.
  • the film thickness of the lubricating layer prior to washing was deemed A
  • the film thickness of the lubricating layer after washing was deemed B
  • the binding ratio (bonding ratio) of the lubricant was calculated from a ratio between A and B ((B/A) ⁇ 100 (%)).
  • the adhesion between the lubricating layer and the protective layer was evaluated against the criteria listed below.
  • the sliding times until the friction coefficients of the surfaces of the lubricating layers sharply increased were measured.
  • the sliding time until the friction coefficient sharply increased was measured four times for the lubricating layer of each magnetic recording medium, and the average value (time) was used as an index of the wear resistance of a lubricant coating.
  • the time until the friction coefficient sharply increased can be used as an index of the wear resistance of the lubricating layers for the reason to be described below.
  • the lubricating layers of the magnetic recording media are getting worn due to the use of the magnetic recording media. This is because, once the lubricating layer disappears due to friction, the contact and the protective layer come into direct contact with each other and the friction coefficient sharply increases.
  • the time until the friction coefficient sharply increased is also considered to correlate with friction tests.
  • the magnetic recording medium and a magnetic head were mounted on a spin stand, and the magnetic head was floated at a fixed point for 10 minutes under normal temperature and reduced pressure conditions (about 250 torr). Subsequently, the surface of the magnetic head facing the magnetic recording medium (the surface of the lubricating layer) was analyzed using an Electron Spectroscopy for Chemical Analysis (ESCA) analyzer. Based on the intensity of the fluorine-derived peak (signal intensity (a.u.)) measured by ESCA, the amount of the lubricant adhered to the magnetic head was evaluated against the criteria shown in Table 3. The smaller amount of the lubricant adhered to the magnetic head is better, and the lower signal intensity is better.
  • ESCA Electron Spectroscopy for Chemical Analysis
  • Example 2 In Comparative Example 2 in which a compound having perfluoropolyether chains bonded at both terminals of a hydrocarbon chain, which was located at the center of the molecule, through a linking group including a hydroxy group, the evaluation of the bonding ratio was B (Permissible), and the evaluation of the wear resistance was A (Favorable). However, the results of the bonding ratio, pickup suppression test and wear resistance thereof were inferior to that of Example 3 which used a compound wherein terminal groups represented by —OCH 2 CH(OH)CH 2 O(CH 2 ) m OH (m in the formula is an integer of 2 to 4) were bonded to the ends of the perfluoropolyether chains through a methylene group.
  • Comparative Example 3 which used a compound wherein terminal groups represented by —OCH 2 CH(OH)CH 2 O(CH 2 ) m OH (m in the formula is an integer of 2 to 4) were bonded to the ends through a methylene group, the evaluation of the wear resistance was A (Favorable). However, since the compound in which the perfluoropolyether chain is located at the center of the molecule was used in Comparative Example 3, the evaluation of the bonding ratio and the pickup suppression test were C (Impermissible).
  • a lubricating layer which exhibits excellent adhesion to the protective layer can suppress pickup, and exhibits excellent wear resistance even when the thickness thereof is reduced to 9 ⁇ to 10 ⁇ , can be obtained by forming the lubricating layer which contains the compounds of Examples 1 to 7 on the protective layer of the magnetic recording medium.
  • the present invention provides a fluorine-containing ether compound that is capable of forming lubricating layers which have excellent wear resistance and can suppress pickup in spite of a thin thickness, and can be preferably used as a material for lubricants for magnetic recording media.
  • a lubricant for a magnetic recording medium containing the fluorine-containing ether compound of the present invention makes it possible to form lubricating layers capable of realizing excellent wear resistance and can suppress pickup, in spite of a thin thickness.

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