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

Abstract

This fluorine-containing ether compound is represented by the following formula. R1-O-CH2-R2-CH2-O-R3 (R2 is a perfluoropolyether chain. R1 is formula (2-1) or formula (2-2). R3 is an organic group having at least one polar group and having 2-65 carbon atoms. In formula (2-1), X1 is a divalent linking group having 1-40 carbon atoms. Y1 and Z1 are each an organic group having 1-12 carbon atoms or a hydrogen atom. At least one of X1, Y1, and Z1 contains a primary hydroxy group. In formula (2-2), X2 is a divalent linking group having 1-40 carbon atoms. Y2 is an organic group having 1-12 carbon atoms or a hydrogen atom. Z2 is an organic group having 1-12 carbon atoms. At least one of X2, Y2, and Z2 contains a primary hydroxy group.)

Description

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

[0001] The present invention relates to a fluorine-containing ether compound, a lubricant for a magnetic recording medium, and a magnetic recording medium. This application claims priority to Japanese Patent Application No. 2023-218393, filed on December 25, 2023, the contents of which are incorporated herein by reference.

[0002] In order to increase the recording density in magnetic recording and reproducing devices, magnetic recording media suitable for high recording densities are being developed. Conventional magnetic recording media include those in which a recording layer is formed on a substrate and a protective layer made of carbon or the like is formed on the recording layer. The protective layer protects the information recorded on the recording layer and improves the sliding properties of the magnetic head. The protective layer also covers the recording layer to prevent the metal contained in the recording layer from being corroded by environmental substances.

[0003] However, the durability of a magnetic recording medium cannot be sufficiently achieved by simply providing a protective layer on the recording layer. Therefore, a lubricant is applied to the surface of the protective layer to form a lubricating layer. The lubricating layer disposed on the outermost surface of a magnetic recording medium is required to have various properties, such as the flying stability of the magnetic head and wear resistance, in addition to improving the durability and protective power of the protective layer.

[0004] The lubricant used in forming the lubricating layer of the magnetic recording medium is -CF ２ It has been proposed to use a fluorine-based polymer having a repeating structure containing -, and a compound having a polar group such as a hydroxyl group or an amide group at the end of the polymer (see, for example, Patent Documents 1 to 4).

[0005] Patent Document 1 discloses a lubricant comprising a compound having terminal groups that are straight-chain saturated aliphatic hydrocarbons or fluorinated derivatives thereof having 3 to 12 carbon atoms and containing one or more etheric oxygen atoms at both ends of a perfluoropolyether chain, and that have multiple hydroxyl groups, with the shortest distance between the hydroxyl groups being 3 atoms or more.

[0006] Patent Document 2 discloses a fluorine-containing ether compound in which divalent linking groups having polar groups are linked to both ends of a perfluoropolyether chain, and at least one of the chains is linked to an end group in which one or more hydrogen atoms of a chain organic group having 1 to 8 carbon atoms have been substituted with a group having an amide bond.

[0007] Patent Document 3 describes a lubricant containing a fluoropolyether compound having an aromatic group and a hydroxyl group, and also describes a fluoropolyether compound having H, an alkoxy group having 1 to 4 carbon atoms, an amino group, or an amide group bonded to the end via a phenylene group.

[0008] Patent Document 4 discloses a method for synthesizing a fluoropolyalkyl ether amide used as a lubricant for magnetic recording media. Patent Document 4 describes a method for producing a fluoropolyalkyl ether amide in which amide groups are directly bonded to both ends of a perfluoropolyalkyl ether by reacting ester groups located at both ends of the fluoropolyalkyl ether with an amine compound having a polar group.

[0009] Japanese Patent No. 4632144 (B) International Publication No. 2019 / 039265 (A) Japanese Patent Application Laid-Open No. 2013-163667 (A) U.S. Patent No. 6,187,954 (B)

[0010] In order to increase the capacity of magnetic recording and reproducing devices, development of magnetic recording media suitable for high recording density is progressing. In recent years, in order to improve the recording density of magnetic recording media, there has been a demand for further shortening the distance between the magnetic head and the magnetic layer of the magnetic recording media, thereby reducing the magnetic spacing (flying height). Therefore, there is a demand for further reducing the thickness of the protective layer and / or lubricating layer in the magnetic recording media.

[0011] However, generally, when the thickness of the lubricating layer is reduced, the covering property of the lubricating layer is reduced, and the adhesion between the lubricating layer covering the surface of the protective layer and the protective layer is insufficient, which results in the fluorine-containing ether compound in the lubricating layer easily adhering to the magnetic head, causing pickup.

[0012] The present invention has been made in view of the above circumstances, and aims to provide a fluorine-containing ether compound that can form a lubricating layer that has a high bond ratio to a protective layer, which is an index of adhesion between the lubricating layer and the protective layer, even when the thickness is thin, and that suppresses pickup, and that can be suitably used as a material for a lubricant for a magnetic recording medium.

[0013] Another object of the present invention is to provide a lubricant for magnetic recording media, which contains the fluorine-containing ether compound of the present invention and is capable of forming a lubricating layer that has a high bond ratio to a protective layer and suppresses pick-up even when the lubricating layer is thin. Another object of the present invention is to provide a magnetic recording medium, which has a lubricating layer containing the fluorine-containing ether compound of the present invention, has good adhesion between the lubricating layer and the protective layer, and has excellent pick-up resistance.

[0014] The present inventors have conducted extensive research to solve the above-mentioned problems. As a result, they have found that a fluorine-containing ether compound can be obtained by bonding end groups consisting of an organic group having 2 to 65 carbon atoms and at least one polar group to both ends of a perfluoropolyether chain via a methylene group and an ether oxygen atom, and at least one of the end groups is a specific organic group containing an amide bond and a primary hydroxyl group, and have arrived at the present invention. Specifically, the present invention relates to the following:

[0015] [1] A fluorine-containing ether compound represented by the following formula (1): １ -O-CH ２ -R ２ -CH ２ -O-R ３ (1) (In formula (1), R ２ is a perfluoropolyether chain. １ is expressed by formula (2-1) or formula (2-2). ３ is an organic group having 2 to 65 carbon atoms and at least one polar group. １ and R ３ may be the same or different from each other.)

[0016] (In formula (2-1), X １Y is a divalent linking group having 1 to 40 carbon atoms which may contain at least one of a polar group and an ether oxygen atom. １ and Z １ are each independently an organic group having 1 to 12 carbon atoms which may contain at least one of a polar group and an ether oxygen atom, or a hydrogen atom. １ and Z １ may be bonded to each other to form a ring. １ , Y １ , Z １ At least one of the following groups contains a primary hydroxyl group. ２ Y is a divalent linking group having 1 to 40 carbon atoms which may contain at least one of a polar group and an ether oxygen atom. ２ is an organic group having 1 to 12 carbon atoms which may contain at least one of a polar group and an ether oxygen atom, or a hydrogen atom. ２ is an organic group having 1 to 12 carbon atoms which may contain at least one of a polar group and an ether oxygen atom. ２ and Z ２ may be bonded to each other to form a ring. ２ , Y ２ , Z ２ At least one of the groups contains a primary hydroxyl group.

[0017] [2] Y in the formula (2-1) １ and Z １ at least one of the groups contains a primary hydroxyl group, and Y in the formula (2-2) ２ and Z ２ The fluorine-containing ether compound according to [1], wherein at least one of the following groups contains a primary hydroxyl group.

[0018] [3] Y in the formula (2-1) １ and Z １ At least one of the above is represented by formula (3-1), and Y in formula (2-2) ２ and Z ２ The fluorine-containing ether compound according to [2], wherein at least one of the following is represented by formula (3-1): -[(CH ２ ) ａ１ -O] ｂ１-H (3-1) (In formula (3-1), a1 is an integer of 1 to 4. b1 is an integer of 1 to 3. When b1 is 2 or 3, each a1 may be the same or different.)

[0019] [4] Y in the formula (2-1) １ and Z １ one of which is represented by the formula (3-1) and the other is selected from the group consisting of a group represented by the formula (3-1), an organic group having 1 to 12 carbon atoms and not containing a polar group, and a hydrogen atom; ２ and Z ２ one of which is represented by the formula (3-1) and the other is selected from the group consisting of a group represented by the formula (3-1), an organic group having 1 to 12 carbon atoms and not containing a polar group, and a hydrogen atom (provided that Z ２ does not become a hydrogen atom), the fluorine-containing ether compound according to [3].

[0020] [5] X in the formula (2-1) １ and X in the formula (2-2) ２ are each independently a linking group selected from formula (4-1) or (4-2):

[0021] (In formula (4-1), c4 is an integer of 1 to 3, and c1 to c3 are each independently an integer of 1 to 4. When c4 is 2 or 3, c1 and c2 may be the same or different. * represents -R ２ -CH ２ represents a site connecting to the oxygen atom of -O-, and ** represents a site connecting to the carbonyl carbon atom or nitrogen atom that constitutes an amide bond.) (In formula (4-2), c5 is an integer of 1 to 5, c6 is an integer of 0 to 3, and c7 is an integer of 1 to 5. When c6 is 2 or 3, the respective c5s may be the same or different. * represents -R ２ -CH ２ represents the site of bonding to the oxygen atom of —O—, and ** represents the site of bonding to the carbonyl carbon atom or nitrogen atom that constitutes an amide bond.

[0022] [6] X in the formula (2-1) １ and X in the formula (2-2) ２ is a linking group containing at least one primary hydroxyl group. １ and X in the formula (2-2) ２ is a linking group containing at least one primary hydroxyl group, and Y in the formula (2-1) １ , Z １ and Y in the formula (2-2) ２ , Z ２ are each independently selected from the group consisting of organic groups having 1 to 12 carbon atoms and not containing a polar group, and a hydrogen atom (provided that Z ２ does not become a hydrogen atom), the fluorine-containing ether compound according to [1].

[0023] [8] X in the formula (2-1) １ and X in the formula (2-2) ２ are each independently a linking group represented by formula (5-1). ２ ) ｅ -[O-(CH ２ ) ｆ ] ｇ -CHR ４ - [(CH ２ ) ｈ -O] ｊ - (CH ２ ) ｉ -** (5-1) (In formula (5-1), e, f, h, and i each independently represent an integer of 0 to 4. g and j each independently represent an integer of 0 to 2. When g is 2, each f may be the same or different. When g is 2, -(CH ２ ) ｆ f in - cannot be 0. When e is 0, g is 0. When j is 2, each h may be the same or different. When j is 2, -(CH ２ ) ｈ - h in the - is never 0. If i is 0, j is 0. R ４is expressed by formula (6-1). * is -R ２ -CH ２ represents the site of bonding to the oxygen atom of —O—, and ** represents the site of bonding to the carbonyl carbon atom or nitrogen atom that constitutes an amide bond. ２ ) ｄ１ -O] ｄ２ -H (6-1) (In formula (6-1), d1 is an integer of 1 to 4. d2 is an integer of 1 to 3. When d2 is 2 or 3, each d1 may be the same or different.)

[0024] [9] R in the formula (1) ３

[10] The fluorine-containing ether compound according to any one of [1] to [8], wherein R in formula (1) is represented by formula (2-1) or formula (2-2). １ and R ３ The fluorine-containing ether compound according to [9], wherein

[0025]

[11] R in the formula (1) ３ is any group represented by the following formulas (7-1) to (7-3): (In formula (7-1), y1 is 1 or 2, and y2 is an integer of 0 to 3. Q is an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, an alkynyl group, or a polar group. When y1 is 1, Q is a polar group. When Q is an aromatic hydrocarbon group or an unsaturated heterocyclic group, an atom constituting the ring structure in Q bonds to the methylene group adjacent to Q. When Q is an alkenyl group or an alkynyl group, a carbon atom constituting the unsaturated bond in Q bonds to the methylene group adjacent to Q.) (In formula (7-2), y3 is an integer of 1 to 3, y4 is 0 or 1, and y5 is an integer of 0 to 3. Q is an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, an alkynyl group, or a polar group. When y4 is 0, Q is a polar group. When Q is an aromatic hydrocarbon group or an unsaturated heterocyclic group, an atom constituting the ring structure in Q bonds to the methylene group adjacent to Q. When Q is an alkenyl group or an alkynyl group, a carbon atom constituting the unsaturated bond in Q bonds to the methylene group adjacent to Q.) (In formula (7-3), y6 is 0 or 1, y7 is an integer of 1 to 3, and y8 is an integer of 0 to 3. Q is an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, an alkynyl group, or a polar group. When y6 is 0, Q is a polar group. When Q is an aromatic hydrocarbon group or an unsaturated heterocyclic group, an atom constituting the ring structure in Q bonds to the methylene group adjacent to Q. When Q is an alkenyl group or an alkynyl group, a carbon atom constituting the unsaturated bond in Q bonds to the methylene group adjacent to Q.)

[0026]

[12] R in the formula (1) ２ is a perfluoropolyether chain represented by the following formula (8): ２ ) ｗ１ -O-(CF ２ O) ｗ２ -(CF ２ CF ２ O) ｗ３ -(CF ２ CF ２ CF ２ O) ｗ４ -(CF ２ CF ２CF ２ CF ２ O) ｗ５ -(CF ２ ) ｗ６ - (8) (In formula (8), w2, w3, w4, and w5 represent the average degree of polymerization, and each independently represents 0 to 20. However, w2, w3, w4, and w5 cannot all be 0 at the same time. w1 and w6 are CF ２ The repeating units in formula (8) are (CF ２ O), (CF ２ CF ２ O), (CF ２ CF ２ CF ２ O), (CF ２ CF ２ CF ２ CF ２ There are no particular restrictions on the arrangement order of O).

[0027]

[13] R in the formula (1) ２ is any one selected from perfluoropolyether chains represented by the following formulas (8-1) to (8-4): ２ -(OCF ２ CF ２ ) ｗ７ -(OCF ２ ) ｗ８ -OCF ２ - (8-1) (In formula (8-1), w7 and w8 represent the average degree of polymerization, w7 represents 1 to 20, and w8 represents 0 to 20.) -CF ２ CF ２ -(OCF ２ CF ２ CF ２ ) ｗ９ -OCF ２ CF ２ - (8-2) (In formula (8-2), w9 represents the average degree of polymerization and represents 1 to 15.) -CF ２ CF ２ CF ２ -(OCF ２ CF ２ CF ２ CF ２ ) ｗ１０-OCF ２ CF ２ CF ２ - (8-3) (In formula (8-3), w10 represents the average degree of polymerization and represents 1 to 10.) - (CF ２ ) ｗ１１ -O-(CF ２ CF ２ CF ２ O) ｗ１２ -(CF ２ CF ２ O) ｗ１３ -(CF ２ ) ｗ１４ - (8-4) (In formula (8-4), w12 and w13 represent the average degree of polymerization, each independently representing 1 to 20. w11 and w14 represent CF ２ is an average value representing the number of

[0028]

[14] The fluorinated ether compound according to any one of [1] to

[13] , wherein the fluorinated ether compound represented by formula (1) is any one of compounds represented by the following formulae (1A) to (1J) and (2A) to (2J): (In formula (1A), p1A and q1A represent an average degree of polymerization, p1A represents 1 to 20, and q1A represents 0 to 20.) (In formula (1B), p1B and q1B represent an average degree of polymerization, p1B represents 1 to 20, and q1B represents 0 to 20.) (In formula (1C), p1C and q1C represent an average degree of polymerization, p1C represents 1 to 20, and q1C represents 0 to 20.) (In formula (1D), p1D and q1D represent an average degree of polymerization, p1D represents 1 to 20, and q1D represents 0 to 20.) (In formula (1E), p1E and q1E represent an average degree of polymerization, p1E represents 1 to 20, and q1E represents 0 to 20.) (In formula (1F), p1F and q1F represent an average degree of polymerization, p1F representing 1 to 20, and q1F representing 0 to 20.) (In formula (1G), r1G represents an average degree of polymerization and represents 1 to 15.) (In formula (1H), r1H represents an average degree of polymerization and represents 1 to 15.) (In formula (1I), r1I represents an average degree of polymerization and represents 1 to 15.) (In formula (1J), r1J represents an average degree of polymerization and represents 1 to 15.) (In formula (2A), p2A and q2A represent an average degree of polymerization, p2A represents an integer of 1 to 20, and q2A represents an average degree of polymerization.) (In formula (2B), p2B and q2B represent an average degree of polymerization, p2B represents an integer of 1 to 20, and q2B represents an average degree of polymerization.) (In formula (2C), p2C and q2C represent an average degree of polymerization, p2C represents an integer of 1 to 20, and q2C represents an average degree of polymerization.) (In formula (2D), p2D and q2D represent an average degree of polymerization, p2D represents an integer of 1 to 20, and q2D represents an average degree of polymerization.) (In formula (2E), p2E and q2E represent an average degree of polymerization, p2E represents an integer of 1 to 20, and q2E represents an average degree of polymerization.) (In formula (2F), p2F and q2F represent an average degree of polymerization, p2F representing 1 to 20, and q2F representing 0 to 20.) (In formula (2G), r2G represents an average degree of polymerization, representing 1 to 15.) (In formula (2H), r2H represents an average degree of polymerization, representing 1 to 15.) (In formula (2I), r2I represents an average degree of polymerization, representing 1 to 15.) (In formula (2J), r2J represents an average degree of polymerization, representing 1 to 15.)

[0029]

[15] The fluorinated ether compound according to any one of [1] to

[14] , having a number average molecular weight in the range of 500 to 10,000.

[16] A lubricant for magnetic recording media, comprising the fluorinated ether compound according to any one of [1] to

[15] .

[17] A magnetic recording medium comprising at least a magnetic layer, a protective layer, and a lubricating layer sequentially provided on a substrate, wherein the lubricating layer comprises the fluorinated ether compound according to any one of [1] to

[15] .

[18] The magnetic recording medium according to

[17] , wherein the lubricating layer has an average film thickness of 0.5 nm to 2.0 nm.

[0030] The fluorine-containing ether compound of the present invention is a compound represented by the above formula (1), and is suitable as a material for a lubricant for a magnetic recording medium.Since the lubricant for a magnetic recording medium of the present invention contains the fluorine-containing ether compound of the present invention, even if the thickness is reduced, the bond ratio to the protective layer, which is an index of the adhesion between the lubricating layer and the protective layer, is high, and a lubricating layer that suppresses pick-up can be formed.The magnetic recording medium of the present invention has a lubricating layer that contains the fluorine-containing ether compound of the present invention.Therefore, the magnetic recording medium of the present invention has good adhesion between the lubricating layer and the protective layer, has excellent pick-up resistance, and has excellent reliability and durability.

[0031] 1 is a schematic cross-sectional view showing an embodiment of a magnetic recording medium of the present invention.

[0032] In order to solve the above problems, the present inventors have focused on the relationship between the molecular structure of a fluorine-containing ether compound contained in a lubricant and the protective layer, and have conducted extensive research as described below. Conventionally, fluorine-containing ether compounds having a polar group such as a hydroxyl group at the end of a perfluoropolyether chain have been preferably used as materials for lubricants for magnetic recording media (hereinafter sometimes abbreviated as "lubricants") that are applied to the surface of a protective layer.

[0033] The polar groups contained in the fluorine-containing ether compound bond with the active sites on the protective layer to improve the adhesion of the lubricating layer to the protective layer. For this reason, fluorine-containing ether compounds having polar groups not only at the ends of the chain structure but also within the chain structure are preferably used as lubricant materials.

[0034] However, conventional lubricating layers containing fluorine-containing ether compounds, even when formed using fluorine-containing ether compounds having multiple polar groups in the molecule, sometimes fail to achieve sufficient adhesion to the protective layer. This is presumably because the fluorine-containing ether compounds contained in the lubricating layer contain polar groups that are not adsorbed to the active sites on the protective layer.

[0035] If there are polar groups in the lubricating layer that are not adsorbed to the active points on the protective layer, the fluorine-containing ether compounds contained in the lubricating layer will attract each other and interact with each other, causing local aggregation, or some of the molecules of the fluorine-containing ether compound to float from the surface of the protective layer, resulting in the formation of unevenness on the surface of the lubricating layer.As a result, the state of the lubricant in the lubricating layer becomes bulky, and the coating state of the lubricating layer on the protective layer becomes uneven.If the coating state of the lubricating layer is uneven, the magnetic head is likely to collide with the fluorine-containing ether compound in the lubricating layer, which is likely to lead to pickup in which the lubricant adheres to the magnetic head.In addition, if the adhesion between the lubricating layer and the protective layer is insufficient, the surface structure of the lubricating layer is likely to change when the magnetic recording medium is rotated at high speed, which causes a decrease in durability and reliability.

[0036] Therefore, the present inventors focused on the bond between the polar group contained in the fluorine-containing ether compound and the active site on the protective layer, and conducted extensive research to realize a fluorine-containing ether compound that is less likely to produce polar groups that are not involved in the bond with the active site on the protective layer, has a high bond rate to the protective layer, and can form a lubricating layer with good pick-up resistance.

[0037] As a result, as represented by the above formula (1), a divalent linking group (—CH ２ The present inventors have found that a fluorine-containing ether compound can be obtained by bonding an end group consisting of an organic group having 2 to 65 carbon atoms and having at least one polar group to the fluorine-containing ether compound via a fluorine-containing ether group (—O—), and at least one of the end groups is an organic group represented by the above formula (2-1) or (2-2).

[0038] In such a fluorine-containing ether compound, for reasons <1> to <4> shown below, polar groups that are not involved in bonding with the active sites present on the protective layer are unlikely to be generated, and the amide bond moiety and primary hydroxyl group contained in the organic group represented by formula (2-1) or formula (2-2) located at at least one end of the perfluoropolyether chain are firmly adhered to the protective layer.As a result, the fluorine-containing ether compound of this embodiment is unlikely to be bulky when applied to the protective layer, is easily wetted and spread on the protective layer, and a lubricating layer having a uniform coating state is easily obtained.As a result, it is estimated that a lubricating layer having good adhesion to the protective layer, a high bond rate, and excellent pick-up resistance can be formed.

[0039] <1> The fluorine-containing ether compound represented by the formula (1) has an organic group represented by the formula (2-1) or (2-2) arranged at at least one end. The formulas (2-1) and (2-2) contain at least one primary hydroxyl group. The primary hydroxyl group is a methylene group (—CH ２ -). Therefore, the area around the primary hydroxyl group is sterically empty. Furthermore, primary hydroxyl groups generally have a high degree of freedom and can move more freely than secondary hydroxyl groups. For these reasons, the primary hydroxyl group contained in the organic group represented by formula (2-1) or formula (2-2) located at at least one of the two ends of the perfluoropolyether chain can spontaneously move to the active site on the protective layer, and can easily form a bond with the active site on the protective layer.

[0040] <2> Formula (2-1) and Formula (2-2) contain at least one primary hydroxyl group and an amide bond site (C(═O)N). The amide bond site, as a polar group, exhibits moderate interaction with the protective layer. In Formula (2-1) and Formula (2-2), at least one carbon atom is located between the amide bond site and the primary hydroxyl group. Therefore, in the above-mentioned fluorine-containing ether compound, the amide bond site and the primary hydroxyl group contained in the organic group represented by Formula (2-1) or Formula (2-2) do not inhibit each other from bonding with the active site on the protective layer. Moreover, in the organic group represented by Formula (2-1) or Formula (2-2), the primary hydroxyl group, which has a strong bond to the protective layer, bonds to the active site on the protective layer, thereby shortening the distance between the amide bond site and the protective layer, and allowing the amide bond site to assume an orientation that easily induces adsorption to the protective layer. Therefore, the amide bond moiety and the primary hydroxyl group contained in the organic group represented by formula (2-1) or formula (2-2) are likely to bond simultaneously with the active site on the protective layer. That is, the organic group represented by formula (2-1) or formula (2-2) contained in the above fluorinated ether compound provides a synergistic effect due to the bond between the amide bond moiety and the active site on the protective layer and the bond between the primary hydroxyl group and the active site on the protective layer.

[0041] <3> In the amide bond sites contained in formula (2-1) and formula (2-2), the bond between the carbonyl carbon atom and nitrogen atom constituting the amide bond and the carbon atom adjacent thereto is unlikely to freely rotate. Therefore, in the above-mentioned fluorine-containing ether compound, the amide bond site contained in the organic group represented by formula (2-1) or formula (2-2) and the polar group adjacent to this amide bond site (the primary hydroxyl group contained in formula (2-1) or formula (2-2) and the polar group that may be contained in formula (2-1) or formula (2-2)) are unlikely to interact. Therefore, in the above-mentioned fluorine-containing ether compound, the amide bond site and the polar group contained in the organic group represented by formula (2-1) or formula (2-2) have extremely little ability to inhibit each other's interaction with the protective layer. As a result, in the above-mentioned fluorine-containing ether compound, the amide bond site and the polar group contained in the organic group represented by formula (2-1) or formula (2-2) located at at least one end can each independently bond to a large number of active sites present on the protective layer.

[0042] <4> In the above fluorine-containing ether compound, the organic group represented by formula (2-1) or formula (2-2) located at at least one end and the adjacent perfluoropolyether chain are bonded to each other via a —CH ２ Therefore, the organic group represented by formula (2-1) or formula (2-2) has appropriate flexibility and mobility relative to the perfluoropolyether chain. ２ Because they are bonded via -O-, the amide bond moiety and polar group contained in the organic group represented by formula (2-1) or formula (2-2) are at an appropriate distance from the perfluoropolyether chain. For these reasons, in the above-mentioned fluorine-containing ether compound, the amide bond moiety and polar group contained in the organic group represented by formula (2-1) or formula (2-2) and located at at least one end are unlikely to be inhibited from bonding with the active site on the protective layer by a bulky portion in the fluorine-containing ether compound, such as a nearby perfluoropolyether chain.

[0043] Furthermore, the inventors have confirmed that by forming a lubricating layer on the protective layer of a magnetic recording medium using a lubricant containing the above-mentioned fluorine-containing ether compound, it is possible to form a lubricating layer that has good adhesion to the protective layer, a high bond ratio, and excellent pick-up resistance, and have thus conceived the present invention.

[0044] The fluorine-containing ether compound, lubricant for magnetic recording media, and magnetic recording media of the present invention are described in detail below. The present invention is not limited to the following embodiments. The number, amount, ratio, composition, type, position, material, and configuration of the present invention can be added, omitted, substituted, or modified within the scope of the present invention. The term "polar group" used in this specification does not include halogeno groups (such as -F, -Cl, and -Br) or ether bonds (-O-).

[0045] [Fluorine-containing ether compound] The fluorine-containing ether compound of the present embodiment is represented by the following formula (1): １ -O-CH ２ -R ２ -CH ２ -O-R ３ (1) (In formula (1), R ２ is a perfluoropolyether chain. １ is expressed by formula (2-1) or formula (2-2). ３ is an organic group having 2 to 65 carbon atoms and at least one polar group. １ and R ３ may be the same or different from each other.)

[0046] (In formula (2-1), X １ Y is a divalent linking group having 1 to 40 carbon atoms which may contain at least one of a polar group and an ether oxygen atom. １ and Z １ are each independently an organic group having 1 to 12 carbon atoms which may contain at least one of a polar group and an ether oxygen atom, or a hydrogen atom. １ and Z １ may be bonded to each other to form a ring. １ , Y １ , Z１ At least one of the following groups contains a primary hydroxyl group. ２ Y is a divalent linking group having 1 to 40 carbon atoms which may contain at least one of a polar group and an ether oxygen atom. ２ is an organic group having 1 to 12 carbon atoms which may contain at least one of a polar group and an ether oxygen atom, or a hydrogen atom. ２ is an organic group having 1 to 12 carbon atoms which may contain at least one of a polar group and an ether oxygen atom. ２ and Z ２ may be bonded to each other to form a ring. ２ , Y ２ , Z ２ At least one of the groups contains a primary hydroxyl group.

[0047] (R ２ In the fluorine-containing ether compound represented by formula (1), R ２ is a perfluoropolyether chain (hereinafter, sometimes referred to as a "PFPE chain"). ２ When a lubricating layer is formed by applying a lubricant containing the fluorine-containing ether compound of this embodiment onto a protective layer, the PFPE chain represented by the formula (R) coats the surface of the protective layer and imparts lubricity to the lubricating layer, thereby reducing the frictional force between the magnetic head and the protective layer. ２ The PFPE chain represented by the formula (I) is appropriately selected depending on the performance required of the lubricant containing the fluorine-containing ether compound.

[0048] R ２ Examples of the PFPE chain represented by the formula (1) include those made of a polymer or copolymer of perfluoroalkylene oxide. Examples of perfluoroalkylene oxide include perfluoromethylene oxide, perfluoroethylene oxide, perfluoro-n-propylene oxide, perfluoroisopropylene oxide, and perfluorobutylene oxide.

[0049] R in formula (1) ２is preferably a PFPE chain represented by the following formula (8) derived from a polymer or copolymer of perfluoroalkylene oxide: -(CF ２ ) ｗ１ -O-(CF ２ O) ｗ２ -(CF ２ CF ２ O) ｗ３ -(CF ２ CF ２ CF ２ O) ｗ４ -(CF ２ CF ２ CF ２ CF ２ O) ｗ５ -(CF ２ ) ｗ６ - (8) (In formula (8), w2, w3, w4, and w5 represent the average degree of polymerization, and each independently represents 0 to 20. However, w2, w3, w4, and w5 cannot all be 0 at the same time. w1 and w6 are CF ２ The repeating units in formula (8) are (CF ２ O), (CF ２ CF ２ O), (CF ２ CF ２ CF ２ O), (CF ２ CF ２ CF ２ CF ２ There are no particular restrictions on the arrangement order of O).

[0050] In formula (8), w2, w3, w4, and w5 represent average degrees of polymerization, each independently representing 0 to 20, preferably 0 to 15, and more preferably 0 to 10. In formula (8), w1 and w6 represent CF ２ The values ​​of w1 and w6 are determined depending on the structure of the repeating units located at the ends of the chain structure in the PFPE chain represented by formula (8). ２ O), (CF ２ CF ２ O), (CF ２ CF ２ CF２ O), (CF ２ CF ２ CF ２ CF ２ O) is a repeating unit. There is no particular limitation on the arrangement order of the repeating units in formula (8). There is also no particular limitation on the number of types of repeating units in formula (8).

[0051] R in formula (1) ２ is preferably any one selected from the PFPE chains represented by the following formulas (8-1) to (8-4): ２ is any one selected from the PFPE chains represented by formulas (8-1) to (8-4), the resulting fluorine-containing ether compound provides a lubricating layer with good lubricity. ２ is any one selected from the PFPE chains represented by formulas (8-1) to (8-4), the ratio of the number of oxygen atoms (the number of ether bonds (-O-)) to the number of carbon atoms in the PFPE chain is appropriate. This results in a fluorine-containing ether compound with appropriate hardness. Therefore, the fluorine-containing ether compound applied to the protective layer is less likely to aggregate on the protective layer, and a thinner lubricating layer can be formed with a sufficient coverage.

[0052] -CF ２ -(OCF ２ CF ２ ) ｗ７ -(OCF ２ ) ｗ８ -OCF ２ - (8-1) (In formula (8-1), w7 and w8 represent the average degree of polymerization, w7 represents 1 to 20, and w8 represents 0 to 20.) -CF ２ CF ２ -(OCF ２ CF ２ CF ２ ) ｗ９ -OCF ２ CF ２ - (8-2) (In formula (8-2), w9 represents the average degree of polymerization and represents 1 to 15.) -CF ２ CF ２ CF ２ -(OCF ２ CF ２ CF ２ CF２ ) ｗ１０ -OCF ２ CF ２ CF ２ - (8-3) (In formula (8-3), w10 represents the average degree of polymerization and represents 1 to 10.) - (CF ２ ) ｗ１１ -O-(CF ２ CF ２ CF ２ O) ｗ１２ -(CF ２ CF ２ O) ｗ１３ -(CF ２ ) ｗ１４ - (8-4) (In formula (8-4), w12 and w13 represent the average degree of polymerization, each independently representing 1 to 20. w11 and w14 represent CF ２ is an average value representing the number of

[0053] In formula (8-1), the repeating unit (OCF ２ CF ２ ) and (OCF ２ There is no particular limitation on the arrangement order of (OCF ２ CF ２ ) number w7 and (OCF ２ The number w8 of (OCF ２ CF ２ The PFPE chain represented by formula (8-1) may be a polymer of (OCF ２ CF ２ ) and (OCF ２ ) may be any of a random copolymer, a block copolymer, and an alternating copolymer.

[0054] In formulas (8-1) to (8-3), w7, which indicates the average degree of polymerization, is 1 to 20, w8 is 0 to 20, w9 is 1 to 15, and w10 is 1 to 10, so that the fluorine-containing ether compound can provide a lubricating layer with good lubricity. Furthermore, in formulas (8-1) to (8-3), w7 and w8, which indicate the average degree of polymerization, are 20 or less, w9 is 15 or less, and w10 is 10 or less, so that the viscosity of the fluorine-containing ether compound does not become too high, and a lubricant containing the fluorine-containing ether compound is easily applied, which is preferable. Since w7, w8, w9, and w10, which indicate the average degree of polymerization, are fluorine-containing ether compounds that easily wet and spread on the protective layer and easily provide a lubricating layer with a uniform film thickness, they are preferably 1 to 10, more preferably 1.5 to 8, and even more preferably 2 to 7.

[0055] In formula (8-4), the repeating unit (CF ２ CF ２ CF ２ O) and (CF ２ CF ２ In formula (8-4), there is no particular limitation on the arrangement order of (CF ２ CF ２ CF ２ O) number w12 and (CF ２ CF ２ The number w13 of monomer units (CF ２ CF ２ CF ２ O) and (CF ２ CF ２ O) may be a random copolymer, a block copolymer, or an alternating copolymer.

[0056] In formula (8-4), w12 and w13, which represent the average degree of polymerization, are each independently 1 to 20, preferably 1 to 15, and more preferably 1 to 10. w11 and w14 in formula (8-4) are each independently 1 to 20, more preferably 1 to 15, and more preferably 1 to 10. ２ and each independently represents 1 to 2. w11 and w14 are determined depending on the structure of the repeating unit located at the end of the chain structure in the perfluoropolyether chain represented by formula (8-4).

[0057] (R １ In the fluorine-containing ether compound represented by formula (1), R １ is represented by the following formula (2-1) or (2-2). In the fluorine-containing ether compound of this embodiment, R １ The amide bond site and the primary hydroxyl group contained in the terminal group represented by R exhibit strong interaction with the active site on the protective layer. １ The terminal group represented by the formula (I) is appropriately selected depending on the performance required of the lubricant containing the fluorine-containing ether compound.

[0058] (In formula (2-1), X １ Y is a divalent linking group having 1 to 40 carbon atoms which may contain at least one of a polar group and an ether oxygen atom. １ and Z １ are each independently an organic group having 1 to 12 carbon atoms which may contain at least one of a polar group and an ether oxygen atom, or a hydrogen atom. １ and Z １ may be bonded to each other to form a ring. １ , Y １ , Z １ At least one of the following groups contains a primary hydroxyl group. ２ Y is a divalent linking group having 1 to 40 carbon atoms which may contain at least one of a polar group and an ether oxygen atom. ２ is an organic group having 1 to 12 carbon atoms which may contain at least one of a polar group and an ether oxygen atom, or a hydrogen atom. ２ is an organic group having 1 to 12 carbon atoms which may contain at least one of a polar group and an ether oxygen atom. ２ and Z ２ may be bonded to each other to form a ring. ２ , Y ２ , Z ２ At least one of the groups contains a primary hydroxyl group.

[0059] <X in formula (2-1) １ and X in formula (2-2) ２ > X in formula (2-1)１ and X in formula (2-2) ２ is a divalent linking group having 1 to 40 carbon atoms. １ and X in formula (2-2) ２ has a chain structure and does not inhibit the interaction between the amide bond moiety contained in formula (2-1) and formula (2-2) and the protective layer, and therefore preferably does not contain a ring structure.

[0060] X １ and X ２ is a divalent linking group having one or more carbon atoms, the distance between the perfluoropolyether chain and the amide bond moiety and primary hydroxyl group contained in formula (2-1) and formula (2-2) is not too close. Therefore, the amide bond moiety and primary hydroxyl group contained in formula (2-1) and formula (2-2) can adhere to the protective layer without being affected by the bulkiness of the perfluoropolyether chain. １ and X ２ is a linking group having 40 or less carbon atoms, the distance between the perfluoropolyether chain and the amide bond moiety contained in formula (2-1) and formula (2-2) is not too far. Therefore, the interaction between the amide bond moiety contained in formula (2-1) and formula (2-2) and the protective layer can be effectively prevented from causing the perfluoropolyether chain to float up from the protective layer. Since the distance between the amide bond moiety contained in formula (2-1) and formula (2-2) is more appropriate, X １ and X ２ The divalent linking group represented by the formula (I) preferably contains 1 to 30 carbon atoms, and more preferably 1 to 15 carbon atoms.

[0061] X in formula (2-1) １ and X in formula (2-2) ２ may contain at least one of a polar group and an ether oxygen atom (—O—). １ and X ２ Examples of the polar group that may be contained in the divalent linking group represented by the formula (I) include a hydroxyl group (—OH), an amino group (—NR ５ R ６ ;R ５ and R ６are each independently a hydrogen atom or an organic group.), a carboxy group (-COOH), a formyl group (-(C=O)H), a carbonyl group (-CO-), a sulfo group (-SO ３ X includes a cyano group (-H), a cyano group (-CN), etc. １ and X ２ When the divalent linking group represented by the formula (I) contains a hydroxyl group as a polar group, it may be a primary hydroxyl group, a secondary hydroxyl group, or a tertiary hydroxyl group.

[0062] X １ and X ２ When the divalent linking group represented by X contains a polar group other than a primary hydroxyl group, such as a secondary hydroxyl group, the formula (2-1) and the formula (2-2) have a polar group other than the amide bond site and the primary hydroxyl group. Therefore, the lubricating layer containing the fluorine-containing ether compound represented by formula (1) has even better adhesion to the protective layer and good pick-up resistance. １ and X ２ When the divalent linking group represented by the formula (I) contains a polar group, it is difficult for a polar group that is not involved in bonding with the active site present on the protective layer to be generated, and therefore the number of polar groups is preferably 1 or 2, and more preferably 1.

[0063] X １ and X ２ When the divalent linking group represented by the formula (2-1) contains an ether oxygen atom, the formula (2-1) and the formula (2-2) have appropriate flexibility. Therefore, the lubricating layer containing the fluorine-containing ether compound represented by the formula (1) has even better adhesion to the protective layer. X １ and X ２ When the divalent linking group represented by the formula (I) contains an ether oxygen atom, the number of ether oxygen atoms is preferably 1 or 2, and more preferably 1, since the resulting fluorine-containing ether compound is less likely to aggregate.

[0064] X １ and X ２When the divalent linking group represented by the formula (I) contains a plurality of ether oxygen atoms, adjacent ether oxygen atoms are preferably bonded to each other via a linking group linking two or more carbon atoms, because the distance between adjacent ether oxygen atoms becomes appropriate, resulting in a fluorine-containing ether compound that is less likely to aggregate.

[0065] X １ and X ２ When the divalent linking group represented by the formula: contains a primary hydroxyl group, X １ and X ２ The primary hydroxyl group contained in R ２ Between the perfluoropolyether chain represented by X １ and X ２ and one or more carbon atoms forming a divalent linking group represented by formula (2-1) or formula (2-2) and R ２ and a perfluoropolyether chain represented by -CH ２ -O- is placed. １ and X ２ and the primary hydroxyl group contained in R ２ Since the distance to the perfluoropolyether chain shown by X is too close, １ and X ２ The primary hydroxyl groups contained in X are not affected by the bulkiness of the perfluoropolyether chain and can easily bond with the active sites on the protective layer. １ and X ２ The primary hydroxyl group contained in R ２ Therefore, the distance between the X and the perfluoropolyether chain is not too long. １ and X ２ By bonding the primary hydroxyl groups contained in the compound to the active sites on the protective layer, the perfluoropolyether chains can be effectively prevented from floating up from the protective layer, and a lubricating layer with even better adhesion to the protective layer can be formed.

[0066] X １ and X ２ When the divalent linking group represented by the formula: contains a primary hydroxyl group, X １ and X ２ is preferably a group represented by the following formula (5-1): １ and X２ and the primary hydroxyl group contained in R ２ This is because the primary hydroxyl group is positioned at a position where the distance from the perfluoropolyether chain is more appropriate. ２ ) ｅ -[O-(CH ２ ) ｆ ] ｇ -CHR ４ - [(CH ２ ) ｈ -O] ｊ - (CH ２ ) ｉ -** (5-1) (In formula (5-1), * is -R ２ -CH ２ represents the site of bonding to the oxygen atom of —O—, and ** represents the site of bonding to the carbonyl carbon atom or nitrogen atom that constitutes an amide bond.

[0067] In formula (5-1), e, f, h, and i each independently represent an integer of 0 to 4. Since this makes it easier to ensure the proportion of fluorine atoms in the fluorinated ether compound molecule, e, f, h, and i are preferably integers of 0 to 2. e, f, h, and i may all be the same, or some or all of them may be different.

[0068] In formula (5-1), g and j each independently represent an integer of 0 to 2. When g and j are 2 or less, the molecular weight of formula (2-1) or formula (2-2) is large, which reduces the proportion of fluorine atoms in the fluorine-containing ether compound molecule, thereby preventing the surface free energy of the entire molecule from increasing. When g and / or j are 1 or 2, X in formula (2-1) １ Or X in formula (2-2) ２ The ether bond contained in the compound (1) provides a fluorine-containing ether compound with appropriate flexibility. Therefore, a lubricating layer containing the fluorine-containing ether compound represented by formula (1) has even better adhesion to a protective layer.

[0069] When g is 2, each f may be the same or different. When g is 2, -(CH ２ ) ｆf in - cannot be 0. When e is 0, g is 0. When j is 2, each h may be the same or different. When j is 2, -(CH ２ ) ｈ h in - does not become 0. When i is 0, j is 0. Therefore, the group represented by formula (5-1) does not contain -O-O-, and the atoms at both ends do not become oxygen atoms.

[0070] In formula (5-1), R ４ is a group containing a primary hydroxyl group and is represented by the following formula (6-1): -[(CH ２ ) ｄ１ -O] ｄ２ In formula (6-1), the atom bonding to the trisubstituted carbon atom in formula (5-1) is a carbon atom. Even when formula (6-1) contains an ether oxygen atom (when d2 is 2 or 3), the ether oxygen atom and the trisubstituted carbon atom in formula (5-1) are bonded via one or more carbon atoms.

[0071] In contrast, R in formula (5-1) ４ When the ether oxygen atom in R in formula (5-1) is directly bonded to the tri-substituted carbon atom in formula (5-1), the effect of improving structural flexibility due to the ether bond is large, and the mobility of the primary hydroxyl group may be relatively increased. As a result, the bond between the primary hydroxyl group site and the active site on the protective layer becomes dominant, and the amide bond site, which has relatively poor adsorptivity, may be liberated from the protective layer. ４ When represented by formula (6-1), the adsorptivity of the primary hydroxyl group is appropriately controlled, and R １ The amide bond site and the primary hydroxyl group contained in R have excellent adhesiveness. ４ is represented by formula (6-1), it is possible to suppress intermolecular aggregation and a decrease in coverage, which is preferable.

[0072] In formula (6-1), d1 is an integer of 1 to 4. d1 is preferably 1 to 3, since this makes it easier to ensure the proportion of fluorine atoms in the fluorine-containing ether compound molecule. When d2 is 2 or 3, the —(CH ２) ｄ１ In formula (6-1), d1 is more preferably 2 or 3. In this case, the oxygen atoms are not too close to each other, making it difficult for them to aggregate, and chemical stability can be easily ensured. In formula (6-1), d2 is an integer of 1 to 3. When d2 is 2 or 3, the respective d1's may be the same or different.

[0073] In formula (6-1), d2 is more preferably 1 or 2. The primary hydroxyl group and R ２ and the amide bond moiety contained in formula (2-1) or formula (2-2), the distance between the amide bond moiety and the primary hydroxyl group becomes more appropriate, allowing the amide bond moiety and the primary hydroxyl group to strongly interact with the active site on the protective layer. Furthermore, when d2 in formula (6-1) is 1 or 2, the molecular weight of formula (2-1) or formula (2-2) is not too large, so that the proportion of fluorine atoms in the fluorine-containing ether compound molecule is less likely to decrease, and the surface free energy of the entire molecule can be prevented from increasing.

[0074] X １ and X ２ When the divalent linking group represented by the formula (2-1) does not contain a primary hydroxyl group (that is, when the divalent linking group represented by the formula (2-1) does not contain a primary hydroxyl group), １ and Z １ or when at least one of the following groups contains a primary hydroxyl group, or when Y ２ and Z ２ at least one of which contains a primary hydroxyl group), X １ and X ２ is preferably a group represented by the following formula (4-1):

[0075] (* in formula (4-1) is -R ２ -CH ２ represents the site of bonding to the oxygen atom of —O—, and ** represents the site of bonding to the carbonyl carbon atom or nitrogen atom that constitutes an amide bond.

[0076] X １ and X ２ is a group represented by formula (4-1), R ２The distance between the perfluoropolyether chain represented by formula (4-1) and the amide bond site and primary hydroxyl group contained in formula (2-1) or formula (2-2) is neither too close nor too far. Therefore, the amide bond site and primary hydroxyl group can strongly interact with the active site on the protective layer. Furthermore, the group represented by formula (4-1) contains a secondary hydroxyl group. Moreover, the secondary hydroxyl group of the group represented by formula (4-1) is at an appropriate distance from the amide bond site and primary hydroxyl group contained in formula (2-1) or formula (2-2), and is not too close. For these reasons, X １ and X ２ When the divalent linking group represented by the formula (4-1) is a group represented by the formula (4-1), a lubricating layer having even better adhesion to the protective layer and good pick-up resistance can be formed.

[0077] In formula (4-1), c4 is an integer of 1 to 3. When c4 is 2 or 3, c1 and c2 may be the same as or different from each other. c4 is preferably 1 or 2, since this makes it easier to ensure the proportion of fluorine atoms in the fluorinated ether compound molecule.

[0078] In formula (4-1), c1 to c3 each independently represent an integer of 1 to 4. In formula (4-1), the sum of c1, c2, and c3 (when c4 is 2 or greater, it means the sum of all c1s, c2s, and c3) is preferably 10 or less. R ２ and the amide bond site and primary hydroxyl group contained in formula (2-1) or formula (2-2), the distance between the perfluoropolyether chain represented by the formula (4-1) and the amide bond site and primary hydroxyl group becomes more appropriate, allowing the amide bond site and primary hydroxyl group to strongly interact with the active site on the protective layer. Moreover, when the sum of c1, c2, and c3 in formula (4-1) is 10 or less, the molecular weight of formula (2-1) or formula (2-2) is not too large, so that the proportion of fluorine atoms in the fluorine-containing ether compound molecule is less likely to decrease, and the surface free energy of the entire molecule can be prevented from increasing.

[0079] In formula (4-1), c2 and c3 are preferably each independently 1 or 2. When c2 and / or c3 is 1, R ２The distance between the perfluoropolyether chain represented by the formula (2-1) or (2-2) and the amide bond site and the primary hydroxyl group is likely to be more appropriate, and the amide bond site and the primary hydroxyl group can strongly interact with the active site on the protective layer. １ and X ２ The distance between the secondary hydroxyl group in the divalent linking group represented by the formula (2-1) and the amide bond site and the primary hydroxyl group contained in the formula (2-2) is more appropriate. １ and X ２ The secondary hydroxyl group in the formula (2-1) interacts with the amide bond moiety and primary hydroxyl group contained in formula (2-2), thereby preventing inhibition of the interaction between the secondary hydroxyl group, the amide bond moiety, and the primary hydroxyl group and the protective layer.

[0080] X １ and X ２ When the divalent linking group represented by the formula (2-1) does not contain a primary hydroxyl group (that is, when the divalent linking group represented by the formula (2-1) does not contain a primary hydroxyl group), １ and Z １ or when at least one of the following groups contains a primary hydroxyl group, or when Y ２ and Z ２ at least one of which contains a primary hydroxyl group), X １ and X ２ is also preferably a group represented by the following formula (4-2).

[0081] (* in formula (4-2) is -R ２ -CH ２ represents the site of bonding to the oxygen atom of —O—, and ** represents the site of bonding to the carbonyl carbon atom or nitrogen atom that constitutes an amide bond.

[0082] X １ and X ２ is a group represented by formula (4-2), R ２The distance between the perfluoropolyether chain represented by formula (2-1) or formula (2-2) and the amide bond moiety and primary hydroxyl group is neither too close nor too far, and is appropriate, allowing the amide bond moiety and primary hydroxyl group to strongly interact with the active site on the protective layer.

[0083] In formula (4-2), c6 is an integer of 0 to 3. When c6 is 2 or 3, each c5 may be the same or different. c6 is preferably 0 to 2, since this makes it easier to ensure the proportion of fluorine atoms in the fluorine-containing ether compound molecule. When c6 is 1 or more, X １ and X ２ The divalent linking group represented by the formula (2-1) contains an ether oxygen atom. Therefore, the formula (2-1) and the formula (2-2) have appropriate flexibility, and the adhesion to the protective layer is further improved.

[0084] In formula (4-2), c5 is an integer of 1 to 5, and c7 is an integer of 1 to 5. When c5 and / or c7 are integers of 5 or less, the molecular weight of formula (2-1) or formula (2-2) is not too large, so that the proportion of fluorine atoms in the fluorine-containing ether compound molecule is less likely to decrease, and the surface free energy of the entire molecule can be prevented from increasing. In addition, when c5 and / or c7 are integers of 5 or less, R ２ The distance between the perfluoropolyether chain represented by the formula (2-1) and the amide bond site and the primary hydroxyl group in the formula (2-2) is appropriate. ２ In formula (4-2), c5 and / or c7 are preferably integers of 1 to 3, so that the perfluoropolyether chains represented by the formula (4-2) are less likely to lift off the protective layer, the bulkiness of the lubricating layer from the protective layer is reduced, and a lubricating layer having even better adhesion to the protective layer can be formed.

[0085] In formula (4-2), the sum of c5 and c7 (when c6 is 2 or more, it means the sum of all c5s and c7s) is preferably 10 or less. ２and the amide bond site and primary hydroxyl group contained in formula (2-1) or formula (2-2), the distance between the perfluoropolyether chain represented by the formula (4-2) and the amide bond site and primary hydroxyl group contained in formula (2-1) or formula (2-2) becomes more appropriate, allowing the amide bond site and primary hydroxyl group to strongly interact with the active site on the protective layer. Moreover, when the sum of c5 and c7 in formula (4-2) is 10 or less, the molecular weight of formula (2-1) or formula (2-2) is not too large, so that the proportion of fluorine atoms in the fluorine-containing ether compound molecule is less likely to decrease, and the surface free energy of the entire molecule can be prevented from increasing.

[0086] In formula (4-2), when c6 is 1 or more, the sum of c5 and c7 is preferably 2 or more, and more preferably 3 or more, because the amide bond moieties contained in formula (2-1) and formula (2-2) can adhere to the protective layer without being affected by the bulkiness of the perfluoropolyether chain.

[0087] <Y in formula (2-1) １ , Z １ , and Y in formula (2-2) ２ , Z ２ > Y in formula (2-1) １ and Z １ , and Y in formula (2-2) ２ are each independently an organic group having 1 to 12 carbon atoms which may contain at least one of a polar group and an ether oxygen atom, or a hydrogen atom. ２ is an organic group having 1 to 12 carbon atoms which may contain at least one of a polar group and an ether oxygen atom.

[0088] In the fluorine-containing ether compound of the present embodiment, Z in formula (2-2) ２ Therefore, at the amide bond site included in formula (2-2), the carbonyl carbon atom constituting the amide bond does not have Z ２ The carbon atom contained in the amide bond is bonded to the nitrogen atom. ２ and the carbon atoms contained in Y ２The carbon atom or hydrogen atom contained in formula (2-2) is bonded to the carbonyl carbon atom and the carbon atom bound to the nitrogen atom constituting the amide bond site (i.e., Z ２ and X ２ and Y ２ The carbon atom that may be included in the amide bond site in formula (2-2) and the carbon atom that may be included in X are difficult to rotate freely. ２ , Y ２ , Z ２ The polar groups contained in at least one of the above hardly interact with each other, and can independently bond to the numerous active sites present on the protective layer without inhibiting their mutual interactions with the protective layer.

[0089] Y in formula (2-1) １ , Z １ , and Y in formula (2-2) ２ , Z ２ When the organic group is the organic group, the number of carbon atoms is 1 to 12, and preferably 1 to 6. This is because it becomes easier to ensure the proportion of fluorine atoms in the fluorine-containing ether compound molecule.

[0090] Y in formula (2-1) １ , Z １ , and Y in formula (2-2) ２ , Z ２ is the organic group, Y １ , Z １ , Y ２ , Z ２ may contain at least one of a polar group and an ether oxygen atom (—O—). １ , Z １ , Y ２ , Z ２ Examples of the polar group that may be contained in the organic group represented by the formula: １ or X ２ The polar groups may be the same as those that may be contained in the divalent linking group represented by Y １ , Z １ , Y ２ , Z ２When the organic group represented by the formula (I) contains a polar group, it is more difficult for a polar group that is not involved in bonding with an active site present on the protective layer to be generated, and therefore the number of polar groups is preferably 1 or 2, and more preferably 1.

[0091] Y １ , Z １ , Y ２ , Z ２ When the organic group represented by the formula: contains an ether oxygen atom, Y １ , Z １ , Y ２ , Z ２ The organic group represented by the formula (I) has appropriate flexibility and easily adheres to the protective layer. Therefore, the fluorine-containing ether compound can form a lubricating layer that has even better adhesion to the protective layer. １ , Z １ , Y ２ , Z ２ When the organic group represented by the formula (I) contains an ether oxygen atom, the number of ether oxygen atoms is preferably 1 or 2, and more preferably 1, since this results in a fluorine-containing ether compound that is less likely to aggregate.

[0092] Y in formula (2-1) １ and Z １ , Y in formula (2-2) ２ and Z ２ may be bonded to each other to form a ring. １ and Z １ , Y ２ and Z ２ Examples of the ring that may be formed by bonding each other include -Y １ -Z １ - or -Y ２ -Z ２ - is a ring having a structure formed by a linking group consisting of a plurality of methylene groups to which a polar group may be bonded and an ether oxygen atom; and -Y １ -Z １ - or -Y ２ -Z ２ - is a ring having a structure in which a plurality of methylene groups, each of which may have a polar group bonded thereto, are exemplified. １ and Z １ , Y ２and Z ２ However, the ring which may be formed by bonding with each other is preferably a 5- to 7-membered ring, more preferably a 5- or 6-membered ring.

[0093] In the fluorine-containing ether compound of the present embodiment, Y in formula (2-1) １ and Z １ at least one of the groups contains a primary hydroxyl group, and Y in formula (2-2) ２ and Z ２ It is preferable that at least one of the groups contains a primary hydroxyl group. This is because, by arranging a primary hydroxyl group having a high bonding ability to the protective layer at the extreme end of the fluorinated ether compound represented by formula (1), a lubricating layer having even better adhesion to the protective layer can be formed.

[0094] Furthermore, Y in formula (2-1) １ and Z １ and at least one of Y in formula (2-2) ２ and Z ２ When a primary hydroxyl group contained in at least one of the formula (1) bonds with an active site on the protective layer, the adjacent amide bond site is also positioned close to the protective layer, thereby promoting the interaction of the amide bond site with the protective layer, and as a result, the adhesion of the entire fluorinated ether compound represented by formula (1) to the protective layer is improved.

[0095] Y in formula (2-1) １ and Z １ and at least one of Y in formula (2-2) ２ and Z ２ When at least one of the groups contains a primary hydroxyl group, the group containing a primary hydroxyl group is preferably a group represented by the following formula (3-1): -[(CH ２ ) ａ１ -O] ｂ１ -H (3-1)

[0096] In formula (3-1), b1 is an integer of 1 to 3. When b1 is 2 or 3, each a1 may be the same or different. b1 is preferably 1 or 2, since this makes it easier to ensure the proportion of fluorine atoms in the fluorinated ether compound molecule.

[0097] In formula (3-1), a1 is an integer of 1 to 4. When a1 is an integer of 4 or less, the molecular weight of formula (2-1) or formula (2-2) is not too large, so that the proportion of fluorine atoms in the fluorinated ether compound molecule is less likely to decrease, and the surface free energy of the entire molecule can be prevented from increasing.

[0098] In formula (3-1), when b1 is 1, a1 is preferably 2 to 4. ２ This is because the distance between the perfluoropolyether chain represented by formula (2-1) or formula (2-2) and the amide bond site in formula (3-1) is not too close, which is more appropriate, and the primary hydroxyl group can move more freely. As a result, the amide bond site and the primary hydroxyl group interact more strongly with the active site on the protective layer, resulting in better adhesion to the protective layer.

[0099] In formula (3-1), when b1 is 2 or 3, a1 is preferably an integer of 1 to 3. When a1 is an integer of 3 or less, R ２ This is because the distance between the perfluoropolyether chain represented by the formula (2-1) or (2-2) and the amide bond site in the formula (3-1) and the primary hydroxyl group in the formula (3-1) is appropriate, and the amide bond site and the primary hydroxyl group can strongly interact with the active site on the protective layer. When b1 is 2 or 3, the -(CH ２ ) ａ１ In -, a1 is more preferably 2 or 3. In this case, the oxygen atoms are not too close to each other, so aggregation is unlikely to occur, and chemical stability is easily ensured.

[0100] Y in formula (2-1) １ and Z １ When at least one of the following does not contain a primary hydroxyl group, and when Y ２ and Z ２When at least one of the groups does not contain a primary hydroxyl group, the resulting fluorine-containing ether compound is less likely to aggregate, and therefore the group not containing a primary hydroxyl group is preferably an organic group having 1 to 12 carbon atoms not containing a polar group, or a hydrogen atom, more preferably an alkyl group having 1 to 12 carbon atoms, or a hydrogen atom, and even more preferably any one of a methyl group, an ethyl group, a propyl group, and a hydrogen atom. ２ never becomes a hydrogen atom.

[0101] Y in formula (2-1) １ and Z １ , (or Y in formula (2-2) ２ and Z ２ ) may be the same or different. Specifically, Y １ and Z １ When one of the groups is represented by formula (3-1), the other group may be represented by formula (3-1), or may be an organic group having 1 to 12 carbon atoms and not containing a polar group, or may be a hydrogen atom. ２ and Z ２ When one of the groups is represented by formula (3-1), the other group may be represented by formula (3-1), or may be an organic group having 1 to 12 carbon atoms and not containing a polar group, or may be a hydrogen atom. ２ never becomes a hydrogen atom.

[0102] The number of primary hydroxyl groups contained in each of formula (2-1) and formula (2-2) is preferably 1 to 3, more preferably 1 or 2. When the number of primary hydroxyl groups is 3 or less, the interaction between primary hydroxyl groups within the same molecule or between molecules is unlikely to become large. This makes it possible to prevent the fluorine-containing ether compound from aggregating and thereby reducing its affinity for active sites on the protective layer. Furthermore, when the number of primary hydroxyl groups is 2 or more, the effect of containing primary hydroxyl groups that have a strong bonding strength to the protective layer becomes more pronounced, resulting in better adhesion to the protective layer.

[0103] In this embodiment, R １ is formula (2-1), X １ , Y １ , Z １In formula (2-1), at least one of X contains a primary hydroxyl group. １ is a linking group containing at least one primary hydroxyl group, Y １ , Z １ are each independently selected from the group consisting of a methyl group, an ethyl group, a propyl group, and a hydrogen atom. １ and Z １ If only one of the groups contains a primary hydroxyl group, X １ is preferably a linking group selected from formula (4-1) and formula (4-2). １ and Z １ When both of X and X contain a primary hydroxyl group, １ is preferably a linking group selected from formula (4-1) and formula (4-2). １ is a linking group containing at least one primary hydroxyl group, Y １ and Z １ It is also preferred that at least one of the groups contains a primary hydroxyl group.

[0104] In formula (2-1), X １ is a linking group containing at least one primary hydroxyl group, examples of which include, but are not limited to, the following formulas (2-1-AA) to (2-1-AO) and (2-1-BA) to (2-1-BO).

[0105]

[0106]

[0107]

[0108] In formula (2-1), Y １ and Z １ Examples of the structure in which at least one of the groups contains a primary hydroxyl group include, but are not limited to, the following formulae (2-1-CA) to (2-1-CL) and (2-1-DA) to (2-1-DO).

[0109]

[0110]

[0111] In this embodiment, R １ is formula (2-2), X ２ , Y ２ , Z ２ In formula (2-2), at least one of X contains a primary hydroxyl group. ２ is a linking group containing at least one primary hydroxyl group, Y ２ , Z ２ are each independently selected from the group consisting of a methyl group, an ethyl group, a propyl group, and a hydrogen atom. ２ and Z ２ If only one of the groups contains a primary hydroxyl group, X ２ is preferably a linking group selected from formula (4-1) and formula (4-2). ２ and Z ２ When both of X and X contain a primary hydroxyl group, ２ is preferably a linking group selected from formula (4-1) and formula (4-2). ２ is a linking group containing at least one primary hydroxyl group, Y ２ and Z ２ It is also preferred that at least one of the groups contains a primary hydroxyl group.

[0112] In formula (2-2), X ２ is a linking group containing at least one primary hydroxyl group, examples of which include, but are not limited to, the following formulas (2-2-AA) to (2-2-AP) and (2-2-BA) to (2-2-BM).

[0113]

[0114]

[0115]

[0116] In formula (2-2), Y ２ and Z ２Examples of structures in which at least one of the above groups contains a primary hydroxyl group include, but are not limited to, the following formulae (2-2-CA) to (2-2-CN) and (2-2-DA) to (2-2-DP).

[0117]

[0118]

[0119]

[0120] (R ３ In the fluorine-containing ether compound represented by formula (1), R ３ The terminal group represented by R is an organic group having 2 to 65 carbon atoms and at least one polar group. ３ The terminal group represented by the formula (I) is preferably an organic group having 2 to 30 carbon atoms, more preferably an organic group having 3 to 20 carbon atoms.

[0121] R ３ Examples of the polar group possessed by the terminal group represented by the formula (I) include a hydroxyl group (—OH), an amino group (—NR ５ R ６ ;R ５ and R ６ are each independently a hydrogen atom or an organic group.), a carboxy group (—COOH), a formyl group (—(C═O)H), a carbonyl group (—CO—), a sulfo group (—SO ３ H), a cyano group (—CN), a group having an amide bond (—NR ７ COR ８ or -CONR ９ R １０ ;R ７ , R ８ , R ９ and R １０ are each independently a hydrogen atom or an organic group.) The "group having an amide bond" refers to a group that bonds at a carbon atom that constitutes an amide bond, as shown in the above formula (for example, a carboxamide group (-C(=O)NH ２ )) and a group bonding at a nitrogen atom constituting an amide bond (for example, an acetamide group (—NHC(═O)CH ３In the group having an amide bond, the R ７ and R ８ may be bonded to each other to form a ring, ９ and R １０ may be bonded to each other to form a ring. ７ , R ８ , R ９ and R １０ are preferably each independently selected from the group consisting of a hydrogen atom, a methyl group, an ethyl group, a propyl group, and a butyl group.

[0122] R ３ When the terminal group represented by the formula (I) has a polar group containing a carbon atom (for example, a carboxy group, a formyl group, a carbonyl group, a cyano group, or a group having an amide bond), the carbon atom contained in the polar group is ３ The number of carbon atoms in the terminal group indicated by is included in the number of carbon atoms.

[0123] R ３ In order to obtain a fluorine-containing ether compound capable of forming a lubricating layer having even better adhesion to the protective layer, the number of polar groups possessed by the terminal group represented by the formula (I) is preferably 1 to 3, and more preferably 2 or 3. If the number of polar groups is 3 or less, in a magnetic recording medium having a lubricating layer containing a fluorine-containing ether compound, aggregation of the fluorine-containing ether compound due to too many polar groups contained in the fluorine-containing ether compound can be prevented, and a decrease in smoothness can be prevented.

[0124] R ３ When R contains two or more polar groups, it is preferable that the two or more polar groups are bonded to different carbon atoms, and that one or more carbon atoms are present between the carbon atoms to which adjacent polar groups are bonded. In this case, the adjacent polar groups are bonded with an appropriate interatomic distance compared to when the carbon atoms to which adjacent polar groups are bonded are directly bonded. For this reason, R ３ The plurality of polar groups of R are all oriented so as to be able to adhere to the protective layer. ３ The multiple polar groups contained in the protective layer are less likely to aggregate and can easily form bonds with the active sites on the protective layer.

[0125] R３ The terminal group represented by R may be an organic group having 1 to 3 polar groups and further having a carbon-carbon unsaturated bond site. ３ has a carbon-carbon unsaturated bond moiety, the terminal group is preferably an organic group having at least one selected from the group consisting of an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, and an alkynyl group.

[0126] Examples of aromatic hydrocarbon groups include a phenyl group, a methoxyphenyl group, a fluorinated phenyl group, a naphthyl group, a methoxynaphthyl group, etc. As described above, aromatic hydrocarbon groups also include groups in which a substituent such as a methoxy group or a fluoro group is bonded to an aromatic hydrocarbon.

[0127] Examples of unsaturated heterocyclic groups include pyrrolyl, pyrazolyl, methylpyrazolyl, imidazolyl, furyl, furfuryl, oxazolyl, isoxazolyl, thienyl, thiazolyl, isothiazolyl, pyridyl, pyrimidinyl, pyridazinyl, pyrazinyl, indolinyl, benzofuranyl, benzothienyl, benzimidazolyl, benzoxazolyl, benzothiazolyl, benzopyrazolyl, benzisoxazolyl, benzisothiazolyl, quinolyl, isoquinolyl, quinazolinyl, quinoxalinyl, phthalazinyl, and cinnolinyl groups. As mentioned above, unsaturated heterocyclic groups also include groups in which a substituent such as a methyl group is bonded to an unsaturated heterocycle.

[0128] Examples of the alkenyl group include a vinyl group, an allyl group, a butenyl group, a pentenyl group, a hexenyl group, etc. Examples of the alkynyl group include a 1-propynyl group, a propargyl group, a butynyl group, a pentynyl group, a hexynyl group, etc.

[0129] R ３ When the terminal group represented by the formula (I) has a carbon-carbon unsaturated bond moiety, the lubricating layer containing the fluorine-containing ether compound has excellent adhesion to the protective layer, and the thickness can be reduced, which is preferable. The reason for this is explained below.

[0130] Among the numerous active sites present on the protective layer, there are locally charged sites and sites where the charge distribution is widespread. １ The hydroxyl group and amide bond site contained therein (and R ３ a hydroxyl group when R has a hydroxyl group) and ３ and the carbon-carbon unsaturated bond moieties contained in the terminal groups represented by the formula (I) are adsorbed to different sites on the protective layer.

[0131] Specifically, R in formula (1) １ The hydroxyl group and amide bond site contained therein (and R ３ The hydroxyl group when R has a hydroxyl group) exhibits adsorption ability by interacting with the locally charged site on the protective layer through the hydrogen atom and the carbonyl group. ３ The carbon-carbon unsaturated bond moiety contained in the terminal group represented by has a delocalized charge, and therefore exhibits adsorption ability by interacting with the moiety on the protective layer where the charge distribution is widespread.

[0132] Therefore, R in formula (1) １ The hydroxyl group and amide bond site contained therein (and R ３ a hydroxyl group when R has a hydroxyl group) and ３ The carbon-carbon unsaturated bond moieties contained in the terminal groups represented by R can independently interact with the active sites on the protective layer. ３ The lubricating layer containing a fluorine-containing ether compound in which the terminal group represented by the formula (I) has a carbon-carbon unsaturated bond moiety has even better adhesion to the protective layer and higher pick-up resistance.

[0133] R ３ may be a terminal group represented by the formula (2-1) or (2-2). １ and R ３ Both of these groups contain an amide bond site and a primary hydroxyl group. １ and R ３ The amide bond site and the primary hydroxyl group contained in R can form strong interactions with the protective layer. ３ When R is a terminal group represented by formula (2-1) or formula (2-2), a preferred example of the structure is１ The terminal group represented by is the same as that described above.

[0134] R ３ is a terminal group represented by the formula (2-1) or (2-2), R １ and R ３ and may be the same or different, and are preferably the same. １ and R ３ When R is the same, the fluorine-containing ether compound is more uniformly coated on the protective layer, and a lubricating layer having better adhesion can be formed. １ and R ３ If the values ​​are the same, the product can be easily produced with fewer steps, which is preferable.

[0135] R ３ is not a terminal group represented by formula (2-1) or formula (2-2), R ３ The terminal group represented by R preferably contains two or three polar groups, at least one of which is a secondary hydroxyl group. ３ Specifically, the terminal group represented by the formula (7-1) is preferably any one of the terminal groups represented by the formulas (7-1) to (7-3) below.

[0136] (In formula (7-1), y1 is 1 or 2, and y2 is an integer of 0 to 3. Q is an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, an alkynyl group, or a polar group. When y1 is 1, Q is a polar group. When Q is an aromatic hydrocarbon group or an unsaturated heterocyclic group, an atom constituting the ring structure in Q bonds to the methylene group adjacent to Q. When Q is an alkenyl group or an alkynyl group, a carbon atom constituting the unsaturated bond in Q bonds to the methylene group adjacent to Q.) (In formula (7-2), y3 is an integer of 1 to 3, y4 is 0 or 1, and y5 is an integer of 0 to 3. Q is an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, an alkynyl group, or a polar group. When y4 is 0, Q is a polar group. When Q is an aromatic hydrocarbon group or an unsaturated heterocyclic group, an atom constituting the ring structure in Q bonds to the methylene group adjacent to Q. When Q is an alkenyl group or an alkynyl group, a carbon atom constituting the unsaturated bond in Q bonds to the methylene group adjacent to Q.) (In formula (7-3), y6 is 0 or 1, y7 is an integer of 1 to 3, and y8 is an integer of 0 to 3. Q is an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, an alkynyl group, or a polar group. When y6 is 0, Q is a polar group. When Q is an aromatic hydrocarbon group or an unsaturated heterocyclic group, an atom constituting the ring structure in Q bonds to the methylene group adjacent to Q. When Q is an alkenyl group or an alkynyl group, a carbon atom constituting the unsaturated bond in Q bonds to the methylene group adjacent to Q.)

[0137] In formulas (7-1) to (7-3), when Q is an aromatic hydrocarbon group, an atom constituting the ring structure in Q is bonded to the methylene group adjacent to Q. When Q is an aromatic hydrocarbon group, the aromatic hydrocarbon groups exemplified above can be used as Q. In formulas (7-1) to (7-3), when Q is an unsaturated heterocyclic group, an atom constituting the ring structure in Q is bonded to the methylene group adjacent to Q. When Q is an unsaturated heterocyclic group, the unsaturated heterocyclic groups exemplified above can be used as Q.

[0138] In formulas (7-1) to (7-3), when Q is an alkenyl group, the carbon atom constituting the unsaturated bond in Q is bonded to the methylene group adjacent to Q. When Q is an alkenyl group, Q may be, for example, -CH=CH ２ , -CH=CHR １１ (R １１ is an organic group.), —CR １２ = CHR １３ (R １２ , R １３ is an organic group.), —CR １４ =CR １５ R １６ (R １４ , R １５ , R １６ is an organic group. １１ ~R １６ Each of the organic groups represented by the formulas (7-1) to (7-3) is preferably a hydrocarbon group having 1 to 3 carbon atoms. When Q in the formulas (7-1) to (7-3) is an alkenyl group, Q is preferably -CH=CH ２ It is preferred that the formula is -CH=CH ２ has an appropriate bulkiness. Therefore, when Q is -CH=CH ２ A lubricating layer containing a fluorine-containing ether compound having an end group of the formula (I) tends to have a low bulkiness on the protective layer, resulting in good smoothness.

[0139] In formulas (7-1) to (7-3), when Q is an alkynyl group, the carbon atom constituting the unsaturated bond in Q is bonded to the methylene group adjacent to Q. When Q is an alkynyl group, examples of Q include -C≡CH, -C≡CR １７ (R １７ is an organic group. １７ The organic group represented by the formula (7-1) to (7-3) is preferably a hydrocarbon group having 1 to 3 carbon atoms. When Q in the formulas (7-1) to (7-3) is an alkynyl group, Q is preferably —C≡CH, since this results in a terminal group with appropriate bulkiness.

[0140] In formulas (7-1) to (7-3), when Q is a polar group, the polar groups exemplified above can be used as Q. Among these polar groups, Q is preferably a hydroxyl group, a group having an amide bond, or a cyano group. When Q is a hydroxyl group, a group having an amide bond, or a cyano group, when a lubricating layer is formed on a protective layer using a lubricant containing this, a more favorable interaction occurs between the lubricating layer and the protective layer. When Q in formulas (7-1) to (7-3) is a polar group, a lubricating layer containing a fluorine-containing ether compound is preferable because it has even better adhesion to the protective layer and can be made thinner. The reasons for this are explained below.

[0141] In formulas (7-1) to (7-3), the secondary hydroxyl groups in formulas (7-1) to (7-3) and Q are bonded via a divalent organic group that may contain an ether bond. Therefore, even if Q is a polar group, the distance between the secondary hydroxyl groups in formulas (7-1) to (7-3) and the polar group represented by Q is appropriate. As a result, the secondary hydroxyl groups in formulas (7-1) to (7-3) and the polar group represented by Q are less likely to be inhibited from bonding with active sites on the protective layer by other polar groups. Furthermore, the secondary hydroxyl groups in formulas (7-1) to (7-3) and the polar group represented by Q are less likely to aggregate.

[0142] Therefore, the secondary hydroxyl group in formulas (7-1) to (7-3) and the polar group represented by Q can each independently adsorb to the active site on the protective layer. As a result, a lubricating layer containing a fluorinated ether compound having a terminal group in which Q in formulas (7-1) to (7-3) is a polar group has even better adhesion to the protective layer and excellent pick-up resistance.

[0143] Among the above, Q in formulas (7-1) to (7-3) is a hydroxyl group, a group having an amide bond, a cyano group, -CH=CH ２ It is preferable that the compound is any one of the following compounds, because this will result in a fluorine-containing ether compound that can form a lubricating layer with a higher coverage and better adhesion and pick-up resistance.

[0144] In the terminal group represented by formula (7-1), y1 is 1 or 2, and y2 is an integer from 0 to 3. When y1 is 1, Q is a polar group, and formula (7-1) has two polar groups. In this case, since formula (7-1) has two polar groups, a lubricating layer with good adhesion to the protective layer can be formed. When y1 is 2, Q may be any of an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, an alkynyl group, and a polar group. When y1 is 2 and Q is any of an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, and an alkynyl group, formula (7-1) also has two polar groups. Therefore, a lubricating layer with good adhesion to the protective layer can be formed. In addition, because Q is an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, or an alkynyl group, a lubricating layer with excellent adhesion and pick-up resistance can be formed by the π-π interaction between the carbon-carbon unsaturated bond site of Q and the protective layer without impairing the adhesion of the two hydroxyl groups contained in formula (7-1) to the protective layer. Furthermore, when y1 is 2 and Q is a polar group, formula (7-1) has three polar groups. Therefore, a lubricating layer with better adhesion to the protective layer can be formed.

[0145] In the terminal group represented by formula (7-1), y2 is an integer of 0 to 3. In the terminal group represented by formula (7-1), even if Q in formula (7-1) is a polar group, the distance between Q and the secondary hydroxyl group in formula (7-1) is not too close, so the polar group in formula (7-1) is less likely to aggregate. When Q in formula (7-1) is a polar group, the distance between Q and the secondary hydroxyl group in formula (7-1) becomes more appropriate, so y2 is preferably 1 or more. In the terminal group represented by formula (7-1), y2 is 3 or less, so the mobility of Q in formula (7-1) does not become too high, and each polar group possessed by the terminal group can sufficiently adhere to the protective layer. It is more preferable that y2 is 2 or less.

[0146] In the terminal group represented by formula (7-2), y3 is an integer of 1 to 3. When y4 is 0, Q is a polar group. Since y3 is an integer of 1 or greater, when y4 is 0, the distance between Q and the secondary hydroxyl group in formula (7-2) is appropriate, and even if Q is a polar group, the polar group in formula (7-2) is less likely to aggregate. Furthermore, since y3 is an integer of 1 or greater, when y4 is 1, the distance between the secondary hydroxyl groups in formula (7-2) is not too close, and the secondary hydroxyl groups in formula (7-2) are less likely to aggregate. In the terminal group represented by formula (7-2), y3 is 3 or less, so the mobility of the terminal group represented by formula (7-2) is not too high, and each polar group possessed by the terminal group can sufficiently adhere to the protective layer. It is preferable that y3 is 2 or less.

[0147] In the terminal group represented by formula (7-2), y4 is 0 or 1. When y4 is 0, Q is a polar group, and formula (7-2) has two polar groups. In this case, since formula (7-2) has two polar groups, a lubricating layer with good adhesion to the protective layer can be formed. When y4 is 1, Q may be any of an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, an alkynyl group, and a polar group. When y4 is 1 and Q is any of an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, and an alkynyl group, formula (7-2) also has two polar groups. Therefore, a lubricating layer with good adhesion to the protective layer can be formed. In addition, because Q is an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, or an alkynyl group, a lubricating layer with excellent adhesion and pick-up resistance can be formed by the π-π interaction between the carbon-carbon unsaturated bond site of Q and the protective layer without impairing the adhesion of the two hydroxyl groups contained in formula (7-2) to the protective layer. Furthermore, when y4 is 1 and Q is a polar group, formula (7-2) has three polar groups. Therefore, a lubricating layer with excellent adhesion to the protective layer can be formed.

[0148] In the terminal group represented by formula (7-2), y5 is an integer of 0 to 3. In the terminal group represented by formula (7-2), even if Q in formula (7-2) is a polar group, the distance between Q and the secondary hydroxyl group in formula (7-2) is not too close, so the polar group in formula (7-2) is unlikely to aggregate. When Q in formula (7-2) is a polar group, the distance between Q and the secondary hydroxyl group in formula (7-2) is more appropriate, so y5 is preferably 1 or more. Also, when y4 is 0, even if y5 is 0, the distance between the polar group Q and the secondary hydroxyl group in formula (7-2) is appropriate due to the y3 methylene groups. When y4 is 0, it is preferable that y5 is 1 or more, because the distance between the polar group Q and the secondary hydroxyl group in formula (7-2) is more appropriate due to the y3 + y5 methylene groups. In the terminal group represented by formula (7-2), since y5 is 3 or less, the mobility of Q in formula (7-2) does not become too high, and each polar group possessed by the terminal group can sufficiently adhere to the protective layer. y5 is preferably 2 or less.

[0149] In the terminal group represented by formula (7-3), y6 is 0 or 1. When y6 is 0, Q is a polar group, and formula (7-3) has two polar groups. In this case, since formula (7-3) has two polar groups, a lubricating layer with good adhesion to the protective layer can be formed. When y6 is 1, Q may be any of an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, an alkynyl group, and a polar group. When y6 is 1 and Q is an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, or an alkynyl group, formula (7-3) also has two polar groups. Therefore, a lubricating layer with good adhesion to the protective layer can be formed. In addition, because Q is an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, or an alkynyl group, a lubricating layer with excellent adhesion and pick-up resistance can be formed by the π-π interaction between the carbon-carbon unsaturated bond site of Q and the protective layer without impairing the adhesion of the two hydroxyl groups contained in formula (7-3) to the protective layer. Furthermore, when y6 is 1 and Q is a polar group, formula (7-3) has three polar groups. Therefore, a lubricating layer with excellent adhesion to the protective layer can be formed.

[0150] In the terminal group represented by formula (7-3), y7 is an integer of 1 to 3. Since y7 is 1 or more, when y6 is 1, the distance between the secondary hydroxyl groups in formula (7-3) does not become too close. Therefore, the secondary hydroxyl groups in formula (7-3) are less likely to aggregate. In the terminal group represented by formula (7-3), since y7 is 3 or less, the mobility of the terminal group represented by formula (7-3) does not become too high, and each polar group possessed by the terminal group can sufficiently adhere to the protective layer. It is preferable that y7 is 2 or less.

[0151] In the terminal group represented by formula (7-3), y8 is an integer of 0 to 3. Therefore, the carbon atom to which Q is bonded and the carbon atom to which the secondary hydroxyl group adjacent to Q is bonded are each bonded directly or via a chain linking group of 1 to 3 atoms. This provides an appropriate distance between Q and the secondary hydroxyl group adjacent to Q, facilitating interaction between Q and the secondary hydroxyl group and the protective layer, thereby improving adhesion to the protective layer. In the terminal group represented by formula (7-3), y8 is 3 or less, so that the mobility of Q in formula (7-3) is not too high, allowing each polar group in the terminal group to adhere sufficiently to the protective layer. It is preferable that y8 is 0 to 2.

[0152] In the fluorine-containing ether compound represented by formula (1), R １ and R ３ The type of the terminal group represented by can be appropriately selected depending on the performance required of the lubricant containing the fluorine-containing ether compound.

[0153] Specifically, the fluorine-containing ether compound represented by (1) is preferably any of the compounds represented by the following formulas (1A) to (1J) and (2A) to (2J): When the compound represented by formula (1) is any of the compounds represented by the following formulas (1A) to (1J) and (2A) to (2J), the raw materials are easily available, and a lubricating layer having excellent adhesion even when thin and even more excellent pick-up resistance can be formed.

[0154] In the PFPE chains of formulas (1A) to (1J) and (2A) to (2J), p, q, and r are values ​​indicating the average degree of polymerization, and are not necessarily integers. １ and R ３ and is a group represented by formula (2-1) or formula (2-2).

[0155] (In formula (1A), p1A and q1A represent an average degree of polymerization, p1A represents 1 to 20, and q1A represents 0 to 20.) (In formula (1B), p1B and q1B represent an average degree of polymerization, p1B represents 1 to 20, and q1B represents 0 to 20.) (In formula (1C), p1C and q1C represent an average degree of polymerization, p1C represents 1 to 20, and q1C represents 0 to 20.) (In formula (1D), p1D and q1D represent an average degree of polymerization, p1D represents 1 to 20, and q1D represents 0 to 20.) (In formula (1E), p1E and q1E represent an average degree of polymerization, p1E represents 1 to 20, and q1E represents 0 to 20.)

[0156] (In formula (1F), p1F and q1F represent an average degree of polymerization, p1F representing 1 to 20, and q1F representing 0 to 20.) (In formula (1G), r1G represents an average degree of polymerization and represents 1 to 15.) (In formula (1H), r1H represents an average degree of polymerization and represents 1 to 15.) (In formula (1I), r1I represents an average degree of polymerization and represents 1 to 15.) (In formula (1J), r1J represents an average degree of polymerization and represents 1 to 15.)

[0157] (In formula (2A), p2A and q2A represent an average degree of polymerization, p2A represents an integer of 1 to 20, and q2A represents an average degree of polymerization.) (In formula (2B), p2B and q2B represent an average degree of polymerization, p2B represents an integer of 1 to 20, and q2B represents an average degree of polymerization.) (In formula (2C), p2C and q2C represent an average degree of polymerization, p2C represents an integer of 1 to 20, and q2C represents an average degree of polymerization.) (In formula (2D), p2D and q2D represent an average degree of polymerization, p2D represents an integer of 1 to 20, and q2D represents an average degree of polymerization.) (In formula (2E), p2E and q2E represent an average degree of polymerization, p2E represents an integer of 1 to 20, and q2E represents an average degree of polymerization.)

[0158] (In formula (2F), p2F and q2F represent an average degree of polymerization, p2F representing 1 to 20, and q2F representing 0 to 20.) (In formula (2G), r2G represents an average degree of polymerization, representing 1 to 15.) (In formula (2H), r2H represents an average degree of polymerization, representing 1 to 15.) (In formula (2I), r2I represents an average degree of polymerization, representing 1 to 15.) (In formula (2J), r2J represents an average degree of polymerization, representing 1 to 15.)

[0159] The fluorine-containing ether compound of this embodiment preferably has a number-average molecular weight (Mn) in the range of 500 to 10,000, more preferably in the range of 500 to 5,000, and particularly preferably in the range of 1,000 to 3,000. When the number-average molecular weight is 500 or more, the lubricant containing the fluorine-containing ether compound of this embodiment is less likely to evaporate, and the lubricant can be prevented from evaporating and transferring to the magnetic head. Furthermore, when the number-average molecular weight is 10,000 or less, the viscosity of the fluorine-containing ether compound is appropriate, and by applying a lubricant containing this, a thin lubricating layer can be easily formed. When the number-average molecular weight is 5,000 or less, the viscosity becomes easy to handle when applied to a lubricant, and this is more preferable.

[0160] The number average molecular weight (Mn) of the fluorine-containing ether compound was measured by AVANCEIII400 manufactured by Bruker Biospin. １ H-NMR and １９ This is a value measured by F-NMR. １９The number average molecular weight is determined by calculating the number of repeating units of the PFPE chain from the integrated value measured by F-NMR. For NMR (nuclear magnetic resonance) measurements, samples were diluted in a single or mixed solvent such as hexafluorobenzene, d-acetone, or d-tetrahydrofuran and used for the measurements. １９ The reference for F-NMR chemical shifts was set to the peak of hexafluorobenzene at −164.7 ppm. １ The reference for H-NMR chemical shifts was set to the acetone peak at 2.2 ppm.

[0161] The fluorine-containing ether compound of this embodiment is preferably subjected to molecular weight fractionation by an appropriate method to make the molecular weight dispersity (ratio of weight average molecular weight (Mw) / number average molecular weight (Mn)) 1.3 or less. In this embodiment, the method for molecular weight fractionation is not particularly limited, and for example, molecular weight fractionation by silica gel column chromatography, gel permeation chromatography (GPC), or the like, molecular weight fractionation by supercritical extraction, or the like can be used.

[0162] "Production Method" The production method of the fluorinated ether compound of this embodiment is not particularly limited, and the compound can be produced using a conventionally known production method. The fluorinated ether compound of this embodiment can be produced, for example, using the production method shown below.

[0163] <First Production Method> R in formula (1) １ and R ３ are the same as each other, and are a group represented by formula (2-1) or formula (2-2), and X in formula (2-1) １ and X in formula (2-2) ２ is a group represented by formula (4-2), and Y in formula (2-1) １ or Z １ and Y in formula (2-2) ２ or Z ２ When a fluorine-containing ether compound is produced in which is a group represented by formula (3-1), a production method represented by the following formula (9-1) can be used.

[0164] (In formula (9-1), R ２ is R in formula (1). ２It is the same as PG １ represents a protecting group. X represents a (pseudo)halogen group. A １ is -C(=O)N(-Y １ ) -, -C(=O)N(-Z １ ) -, -N(-Y ２ )C(=O)-, -N(-C(=O)Z in formula (2-2) ２ )--. １ is the ether oxygen atom and the amide bond site A １ and represents a divalent linking group disposed between L and ２ is the primary hydroxyl group and the amide bond site A １ and Y in formula (2-1) is a divalent linking group arranged between １ Or Z １ or Y in formula (2-2) ２ Or Z ２ It corresponds to a partial structure of the group represented by the formula:

[0165] (First Reaction) R in Formula (1) ２ At both ends of the PFPE chain corresponding to ２ A fluorine-based compound having Y １ Or Z １ , or Y ２ Or Z ２ A suitable protecting group (PG) corresponding to the primary hydroxyl group in １ ) and the amide bond site (A １ A (pseudo)halogenated alkyl compound having both a hydroxymethyl group (X) and a (pseudo)halogen group (X) is prepared. Then, the (pseudo)halogen groups of the (pseudo)halogenated alkyl compound are reacted with the hydroxymethyl groups at both ends of the fluorine-based compound. At this time, the reaction ratio of the fluorine-based compound having hydroxymethyl groups at both ends to the (pseudo)halogenated alkyl compound is set to about 1:2 (molar ratio). As a result, R ２ At both ends of the PFPE chain corresponding to １ A first intermediate compound is produced which is bonded to a group having both a primary hydroxyl group to which a hydroxyl group (a hydroxyl group) is bonded and an amide bond site.

[0166] Examples of the (pseudo) alkyl halide compound used in the first production method (the method represented by formula (9-1)) include compounds represented by the following formulae (AA) to (AL) and (BA) to (BN). Such (pseudo) alkyl halide compounds can be produced by known methods, and commercially available products may also be used.

[0167] In formulas (AA) to (AL), X represents a (pseudo)halogen group. PG represents a protecting group. １ The two PGs in the same molecule may be the same or different, and one of them corresponds to PG in formula (9-1). １ Corresponding to.)

[0168] In formulas (BA) to (BN), X represents a (pseudo)halogen group. PG represents a protecting group. １ The two PGs in the same molecule may be the same or different, and one of them corresponds to PG in formula (9-1). １ Corresponding to.)

[0169] (Second Reaction) Next, the first intermediate compound obtained in the first reaction in the first production method (the method represented by formula (9-1)) is subjected to the removal of the protecting group (PG) bonded to the primary hydroxyl group. １ ) is deprotected under appropriate conditions. １ and R ３ are the same as each other, and are a group represented by formula (2-1) or formula (2-2), and X in formula (2-1) １ and X in formula (2-2) ２ is a group represented by formula (4-2), and Y in formula (2-1) １ or Z １ and Y in formula (2-2) ２ or Z ２ is a group represented by formula (3-1), thereby obtaining a fluorine-containing ether compound.

[0170] <Second Production Method> R in formula (1) １ and R ３are the same as each other, and are a group represented by formula (2-1) or formula (2-2), and X in formula (2-1) １ and X in formula (2-2) ２ When a fluorine-containing ether compound is produced in which is a group represented by formula (5-1), a production method represented by the following formula (9-2) can be used.

[0171] (In formula (9-2), R ２ is R in formula (1). ２ It is the same as PG ４ represents a protecting group bonded to a group corresponding to the primary hydroxyl group in formula (5-1). X represents a (pseudo)halogen group. A ２ is -X'-C(=O)N(-Y １ )-Z １ or -X'-N(-Y ２ )C(=O)-Z ２ (Y １ , Z １ is Y in formula (2-1) １ , Z １ are groups corresponding to the following: ２ , Z ２ is Y in formula (2-2) ２ , Z ２ X' is a group corresponding to -[(CH ２ ) ｈ -O] ｊ - (CH ２ ) ｉ represents a group corresponding to -. ３ represents a divalent linking group located between the ether oxygen atom and the methine carbon atom, and —(CH ２ ) ｅ -[O-(CH ２ ) ｆ ] ｇ - is a group corresponding to L ４ represents a divalent linking group located between the primary hydroxyl group and the methine carbon atom, and R in formula (5-1) ４ It corresponds to the partial structure of

[0172] (First Reaction) R in Formula (1) ２ At both ends of the PFPE chain corresponding to ２A fluorine-based compound having Y １ and a group corresponding to Z １ or a group corresponding to Y ２ and a group corresponding to Z ２ An amide bond site (A ２ ) and a suitable protecting group (PG) corresponding to the primary hydroxyl group in formula (5-1). ４ A (pseudo)halogenated alkyl compound having both a primary hydroxyl group to which a hydroxymethyl group (X) is bonded and a (pseudo)halogen group (X) is prepared. Then, the (pseudo)halogen groups of the (pseudo)halogenated alkyl compound are reacted with the hydroxymethyl groups at both ends of the fluorine-based compound. At this time, the reaction ratio of the fluorine-based compound having hydroxymethyl groups at both ends to the (pseudo)halogenated alkyl compound is set to about 1:2 (molar ratio). As a result, R ２ At both ends of the PFPE chain corresponding to ４ A first intermediate compound is produced which has a group having both a primary hydroxyl group and an amide bond site bonded thereto.

[0173] Examples of the (pseudo) alkyl halide compound used in the second production method (the method represented by formula (9-2)) include compounds represented by the following formulae (HA) to (HO) and (IA) to (IM). Such (pseudo) alkyl halide compounds can be produced by known methods, and commercially available products may also be used.

[0174] In formulas (HA) to (HM), X represents a (pseudo)halogen group. PG represents a protecting group. ４ Corresponding to.)

[0175] In the formulae (HN) and (HO), X represents a (pseudo)halogen group. PG represents a protecting group. ４ Corresponding to.)

[0176] In formulas (IA) to (IM), X represents a (pseudo)halogen group. PG represents a protecting group. ４Two PGs in the same molecule may be the same or different, and the PG bonded to the oxygen atom of the group not bonded to the nitrogen atom corresponds to PG in formula (9-2). ４ Corresponding to.)

[0177] (Second Reaction) Next, the first intermediate compound obtained in the first reaction in the second production method (the method represented by formula (9-2)) is subjected to the removal of the protecting group (PG) bonded to the primary hydroxyl group. ４ , PG) is deprotected under appropriate conditions. １ and R ３ are the same as each other, and are a group represented by formula (2-1) or formula (2-2), and X in formula (2-1) １ and X in formula (2-2) ２ is a group represented by formula (5-1).

[0178] <Third Production Method> R in formula (1) １ and R ３ are the same as each other, and are a group represented by formula (2-1) or formula (2-2), and X in formula (2-1) １ and X in formula (2-2) ２ is a group represented by formula (4-1), and Y in formula (2-1) １ or Z １ and Y in formula (2-2) ２ or Z ２ When a fluorine-containing ether compound is produced in which is a group represented by formula (3-1), a production method represented by the following formula (10) can be used.

[0179] (In formula (10), R ２ is R in formula (1). ２ It is the same as PG ２ represents a protecting group. ３ is -C(=O)N(-Y １ ) -, -C(=O)N(-Z １ ) -, -N(-Y ２ )C(=O)-, -N(-C(=O)Z in formula (2-2) ２ )--. ５A is the carbon atom to which a secondary hydroxyl group is bonded and the amide bond site A ３ and represents a divalent linking group disposed between L and L, and corresponds to the partial structure of formula (4-1). ６ is the primary hydroxyl group and the amide bond site A ３ represents a divalent linking group disposed between Y １ Or Z １ or Y in formula (2-2) ２ Or Z ２ It corresponds to a partial structure of the group represented by the formula:

[0180] (First Reaction) R in Formula (1) ２ At both ends of the PFPE chain corresponding to ２ A fluorine-based compound having Y １ Or Z １ , or Y ２ Or Z ２ A suitable protecting group (PG) corresponding to the primary hydroxyl group in ２ ) and the amide bond site (A ３ An epoxy compound having both a hydroxymethyl group at both ends of the fluorine-based compound and an epoxy group corresponding to the group represented by formula (4-1) is prepared. Then, the epoxy group of the epoxy compound is reacted with the hydroxymethyl groups at both ends of the fluorine-based compound. At this time, the reaction ratio of the fluorine-based compound having hydroxymethyl groups at both ends to the epoxy compound is set to about 1:2 (molar ratio). This results in the formation of a fluorine-based compound having R ２ At both ends of the PFPE chain corresponding to ２ A first intermediate compound is produced which has a group having both a primary hydroxyl group and an amide bond site bonded thereto.

[0181] Examples of the epoxy compound used in the third production method (the method represented by formula (10)) include compounds represented by the following formulae (CA) to (CO) and (DA) to (DP). Such epoxy compounds can be produced by known methods, and commercially available products may also be used.

[0182] In formulas (CA) to (CO), PG represents a protecting group. PG protecting a primary hydroxyl group is PG in formula (10).２ The two PGs in the same molecule may be the same or different, and one of the two PGs protecting the primary hydroxyl groups corresponds to PG in formula (10). ２ Corresponding to.)

[0183] In formulas (DA) to (DO), PG represents a protecting group. PG protecting a primary hydroxyl group is PG in formula (10). ２ The two PGs in the same molecule may be the same or different, and one of the two PGs protecting the primary hydroxyl groups corresponds to PG in formula (10). ２ Corresponding to.)

[0184] In formula (DP), PG represents a protecting group. PG protecting a primary hydroxyl group is PG in formula (10). ２ Corresponding to.)

[0185] (Second Reaction) Next, the first intermediate compound obtained in the first reaction in the third production method (the method represented by formula (10)) is subjected to the removal of the protecting group (PG) bonded to the primary hydroxyl group. ２ , PG) is deprotected under appropriate conditions. １ and R ３ are the same as each other, and are a group represented by formula (2-1) or formula (2-2), and X in formula (2-1) １ and X in formula (2-2) ２ is a group represented by formula (4-1), and Y in formula (2-1) １ or Z １ and Y in formula (2-2) ２ or Z ２ is a group represented by formula (3-1), thereby obtaining a fluorine-containing ether compound.

[0186] <Fourth Production Method> R in formula (1) １ and R ３ are the same and are a group represented by formula (2-1) or formula (2-2), and X in formula (2-1) １ and X in formula (2-2) ２ When a fluorine-containing ether compound is produced in which is a group represented by formula (5-1), a production method represented by the following formula (11) can be used.

[0187] (In formula (11), R ２ is R in formula (1). ２ It is the same as PG ３ represents a protecting group bonded to a group corresponding to the primary hydroxyl group in formula (5-1). X represents a (pseudo)halogen group. A ４ is -C(=O)N(-Y １ )-Z １ (Y １ , Z １ is Y in formula (2-1) １ , Z １ ) or -N(-Y ２ )C(=O)-Z ２ (Y ２ , Z ２ is Y in formula (2-2) ２ , Z ２ ) are groups corresponding to the following. ７ represents a divalent linking group located between the primary hydroxyl group and the methine carbon atom, and R in formula (5-1) ４ It corresponds to the partial structure of L ８ is the ether oxygen atom and the amide bond site A ４ and represents a divalent linking group disposed between

[0188] (First Reaction) R in Formula (1) ２ At both ends of the PFPE chain corresponding to ２ A fluorine-based compound having a hydroxymethyl group at one end of the fluorine-based compound is provided. A suitable protecting group (PG) corresponding to the primary hydroxyl group in formula (5-1) is provided for the hydroxymethyl group at one end of the fluorine-based compound. ３ The primary hydroxyl group to which R is bonded is reacted with an epoxy compound having both an epoxy group. At this time, the reaction ratio of the fluorine-based compound having hydroxymethyl groups at both ends to the epoxy compound is set to about 1:2 (molar ratio). ２ At both ends of the PFPE chain corresponding to ３ A first intermediate compound having a group having both a primary hydroxyl group and a secondary hydroxyl group, to which a hydroxyl group (i.e., a hydroxyl group) is bonded, is produced.

[0189] Examples of the epoxy compound used in the fourth production method (the method represented by formula (11)) include compounds represented by the following formulae (EA) to (EF). Such epoxy compounds can be produced by known methods, and commercially available products may also be used.

[0190] (In formulas (EA) to (EF), PG represents a protecting group, and PG in formula (11) ３ Corresponding to.)

[0191] (Second reaction) Next, Y １ and a group corresponding to Z １ or a group corresponding to Y ２ and a group corresponding to Z ２ An amide bond site (A ４ A (pseudo)halogenated alkyl compound having both a hydroxyl group (X) and a (pseudo)halogen group (X) is prepared. Then, the (pseudo)halogen group of the (pseudo)halogenated alkyl compound is reacted with the secondary hydroxyl group contained in the first intermediate compound obtained by the first reaction in the fourth production method (the method represented by formula (11)). The reaction ratio of the first intermediate compound to the (pseudo)halogenated alkyl compound is preferably about 1:2 (molar ratio). This allows the formation of a compound having R ２ At both ends of the PFPE chain corresponding to ３ A second intermediate compound having both a primary hydroxyl group to which the hydroxyl group (C) is bonded and an amide bond site is obtained.

[0192] Examples of the (pseudo) alkyl halide compound used in the fourth production method (the method represented by formula (11)) include compounds represented by the following formulae (FA) to (FI) and (GA) to (GI). Such (pseudo) alkyl halide compounds can be produced by known methods, and commercially available products may also be used.

[0193] (In formulae (FA) to (FI) and formulae (GA) to (GI), X represents a (pseudo)halogen group. PG represents a protecting group.)

[0194] (Third Reaction) Next, the second intermediate compound obtained in the second reaction in the fourth production method (the method represented by formula (11)) is subjected to the removal of the protecting group (PG) bonded to the primary hydroxyl group. ３ , PG) is deprotected under appropriate conditions. １ and R ３ are the same and are a group represented by formula (2-1) or formula (2-2), and X in formula (2-1) １ and X in formula (2-2) ２ is a group represented by formula (5-1).

[0195] <Fifth Production Method> R in formula (1) １ and R ３ Unlike R １ and R ３ is a group represented by formula (2-1) or formula (2-2), and X in formula (2-1) １ and X in formula (2-2) ２ is a group represented by formula (4-2), and Y in formula (2-1) １ or Z １ and Y in formula (2-2) ２ or Z ２ When a fluorine-containing ether compound in which is a group represented by formula (3-1) can be produced, for example, the production method shown below can be used.

[0196] (First Reaction) R in Formula (1) ２ At both ends of the PFPE chain corresponding to ２ A fluorine-based compound having a hydroxymethyl group at one end and a (pseudo) alkyl halide compound is prepared. A (pseudo) halogenated compound that can be used in the first production method is also prepared. Then, the (pseudo) halogenated group of the (pseudo) alkyl halide compound is reacted with the hydroxymethyl group at one end of the fluorine-based compound. In this case, in the fifth production method, unlike the first production method, the reaction ratio of the fluorine-based compound having hydroxymethyl groups at both ends and the (pseudo) alkyl halide compound is set to about 1:1 (molar ratio). As a result, R ２ A protecting group (PG) was attached to one end of the PFPE chain corresponding to １A first intermediate compound is produced which is bonded to a group having both a primary hydroxyl group to which a hydroxyl group (a hydroxyl group) is bonded and an amide bond site.

[0197] (Second Reaction) Next, R of the first intermediate compound ２ A hydroxymethyl group (-CH) located at one end of the PFPE chain corresponding to ２ OH) is reacted with a (pseudo) alkyl halide compound that can be used in the first production method and is different from the (pseudo) alkyl halide compound used in the first reaction. At this time, the reaction ratio of the first intermediate compound to the (pseudo) alkyl halide compound is set to about 1:1 (molar ratio). ２ A protecting group (PG) was attached to one end of the PFPE chain corresponding to １ a group having both a primary hydroxyl group to which a protecting group (PG) is bonded and an amide bond site; and a group different from the group bonded to the terminal, which is a protecting group (PG) １ A second intermediate compound is produced which has a group having both a primary hydroxyl group to which the hydroxyl group (A) is bonded and an amide bond site.

[0198] (Third Reaction) Next, the second intermediate compound obtained in the second reaction in the fifth production method is subjected to the reaction of removing the protecting group (PG) bonded to the primary hydroxyl group. １ ) is deprotected under appropriate conditions. １ and R ３ Unlike R １ and R ３ is a group represented by formula (2-1) or formula (2-2), and X in formula (2-1) １ and X in formula (2-2) ２ is a group represented by formula (4-2), and Y in formula (2-1) １ or Z １ and Y in formula (2-2) ２ or Z ２ is a group represented by formula (3-1), thereby obtaining a fluorine-containing ether compound.

[0199] <Sixth Production Method> R in formula (1) １ is a group represented by formula (2-1) or formula (2-2), and X in formula (2-1) １and X in formula (2-2) ２ is a group represented by formula (4-2), and Y in formula (2-1) １ or Z １ and Y in formula (2-2) ２ or Z ２ is a group represented by formula (3-1), and R in formula (1) ３ When a fluorine-containing ether compound having an end group represented by any one of formulas (7-1) to (7-3) is produced, for example, the production method shown below can be used.

[0200] (First Reaction) In the same manner as in the fifth production method, R ２ A protecting group (PG) was attached to one end of the PFPE chain corresponding to １ A first intermediate compound is produced which is bonded to a group having both a primary hydroxyl group to which a hydroxyl group (a hydroxyl group) is bonded and an amide bond site.

[0201] (Second Reaction) Next, R of the first intermediate compound ２ A hydroxymethyl group (-CH) located at one end of the PFPE chain corresponding to ２ OH) is reacted with an epoxy compound having a partial structure corresponding to any of the terminal groups shown in formulas (7-1) to (7-3). At this time, the reaction ratio of the first intermediate compound to the epoxy compound is set to about 1:1 (molar ratio). ２ A protecting group (PG) was attached to one end of the PFPE chain corresponding to １ A second intermediate compound is produced in which a group having both a primary hydroxyl group to which the hydroxyl group (7-1) is bonded and an amide bond site is bonded, and a partial structure corresponding to any of the terminal groups shown in formulas (7-1) to (7-3) is bonded to the other terminal.

[0202] The epoxy compound having a partial structure corresponding to any one of the terminal groups represented by formulas (7-1) to (7-3) used in the sixth production method can be produced by a known method depending on the structure of any one of the terminal groups represented by formulas (7-1) to (7-3), and a commercially available product may also be used.

[0203] (Third Reaction) Next, the second intermediate compound obtained in the second reaction in the sixth production method is subjected to the reaction of removing the protecting group (PG) bonded to the primary hydroxyl group. １) is deprotected under appropriate conditions. １ is a group represented by formula (2-1) or formula (2-2), and X in formula (2-1) １ and X in formula (2-2) ２ is a group represented by formula (4-2), and Y in formula (2-1) １ or Z １ and Y in formula (2-2) ２ or Z ２ is a group represented by formula (3-1), and R in formula (1) ３ is a terminal group represented by any one of formulas (7-1) to (7-3).

[0204] In the fifth and sixth production methods described above, the first reaction, the second reaction, and the third reaction were carried out in this order, but the second reaction may be carried out before the first reaction. In the first reaction of the fifth and sixth production methods, a (pseudo) alkyl halide compound that can be used in the first production method was used, but instead of the (pseudo) alkyl halide compound that can be used in the first production method, a (pseudo) alkyl halide compound that can be used in the second production method may be used (in this case, R １ or R ３ However, the second manufacturing method R １ and R ３ Alternatively, an epoxy compound that can be used in the third production method may be used (in this case, an intermediate compound having a structure corresponding to R １ or R ３ However, the third manufacturing method R １ and R ３ (An intermediate compound having a structure corresponding to

[0205] In the second reaction of the fifth production method, a (pseudo) alkyl halide compound that can be used in the first production method and is different from the (pseudo) alkyl halide compound used in the first reaction was used. However, instead of this, a (pseudo) alkyl halide compound that can be used in the second production method may be used (in this case, R １ or R ３ However, the second manufacturing method R １and R ３ Alternatively, an epoxy compound that can be used in the third production method may be used (in this case, an intermediate compound having a structure corresponding to R １ or R ３ However, the third manufacturing method R １ and R ３ (An intermediate compound having a structure corresponding to

[0206] The (pseudo)halogen group (X) contained in the compound used in the above-described Production Method 1, Production Method 2, and Production Method 4 to Production Method 6 can be, for example, a halogeno group, an arylsulfonyloxy group, an alkylsulfonyloxy group which may be substituted with a fluorine atom, etc. More specifically, the (pseudo)halogen group (X) can be at least one selected from a chloro group, a bromo group, an iodo group, a p-toluenesulfonyloxy group, a methanesulfonyloxy group, a trifluoromethanesulfonyloxy group, a perfluoroalkylsulfonyloxy group, and a nitrobenzenesulfonyloxy group.

[0207] In the above-described first to sixth production methods, the case where the reaction for deprotecting the protecting group bonded to the hydroxyl group is carried out as a separate reaction step has been described as an example. However, the reaction for deprotecting the protecting group may be carried out during post-treatment of the previous reaction.

[0208] [Lubricant for magnetic recording media] The lubricant for magnetic recording media of this embodiment contains a fluorine-containing ether compound represented by formula (1). The lubricant of this embodiment can be used by mixing, as needed, with known materials used as lubricant materials, as long as the properties resulting from the inclusion of the fluorine-containing ether compound represented by formula (1) are not impaired.

[0209] Specific examples of known materials include FOMBLIN (registered trademark) ZDIAC, FOMBLIN ZDEAL, FOMBLIN AM-2001 (all manufactured by Solvay Solexis), Moresco A20H (manufactured by Moresco), etc. The known material to be mixed with the lubricant of this embodiment preferably has a number average molecular weight of 500 to 10,000.

[0210] When the lubricant of this embodiment contains a material other than the fluorinated ether compound represented by formula (1), the content of the fluorinated ether compound represented by formula (1) in the lubricant of this embodiment is preferably 50% by mass or more, more preferably 70% by mass or more, and may even be 80% by mass or more, or 90% by mass or more.

[0211] The lubricant of this embodiment contains the fluorine-containing ether compound represented by the formula (1) above, and therefore has excellent adhesion to the protective layer, and can cover the surface of the protective layer with a high coverage even when the thickness is small, thereby forming a lubricating layer with good coverage. Therefore, the lubricant of this embodiment can form a lubricating layer that has good adhesion to the protective layer, a high bond ratio, and excellent pick-up resistance even when the thickness is small.

[0212] [Magnetic Recording Medium] The magnetic recording medium of this embodiment has at least a magnetic layer, a protective layer, and a lubricating layer sequentially provided on a substrate. In the magnetic recording medium of this embodiment, one or more underlayers can be provided between the substrate and the magnetic layer as needed. An adhesive layer and / or a soft magnetic layer can also be provided between the underlayer and the substrate.

[0213] 1 is a schematic cross-sectional view showing one embodiment of a magnetic recording medium of the present invention. The magnetic recording medium 10 of this 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.

[0214] "Substrate" The substrate 11 may be, for example, a non-magnetic substrate in which a film made of NiP or a NiP alloy is formed on a base made of a metal or alloy material such as Al or an Al alloy. Alternatively, the substrate 11 may be a non-magnetic substrate made of a non-metallic material such as glass, ceramics, silicon, silicon carbide, carbon, or resin, or a non-magnetic substrate in which a film of NiP or a NiP alloy is formed on a base made of such a non-metallic material.

[0215] "Adhesion Layer" The adhesion layer 12 prevents the progress of corrosion of the substrate 11, which occurs when the substrate 11 and the soft magnetic layer 13 provided on the adhesion layer 12 are disposed in contact with each other. The material of the adhesion layer 12 can be appropriately selected from, for example, Cr, Cr alloy, Ti, Ti alloy, CrTi, NiAl, AlRu alloy, etc. The adhesion layer 12 can be formed by, for example, a sputtering method.

[0216] "Soft Magnetic Layer" The soft magnetic layer 13 preferably has a structure in which a first soft magnetic film, an intermediate layer made of a Ru film, and a second soft magnetic film are laminated in this order. That is, the soft magnetic layer 13 preferably has a structure in which the intermediate layer made of a Ru film is sandwiched between two soft magnetic films, and the soft magnetic films above and below the intermediate layer are anti-ferro-coupling (AFC).

[0217] Examples of materials for the first and second soft magnetic films include CoZrTa alloys and CoFe alloys. It is preferable to add Zr, Ta, or Nb to the CoFe alloy used for the first and second soft magnetic films. This promotes the amorphization of the first and second soft magnetic films. As a result, it is possible to improve the orientation of the first underlayer (seed layer) and reduce the flying height of the magnetic head. The soft magnetic layer 13 can be formed, for example, by sputtering.

[0218] "First Underlayer" The first underlayer 14 is a layer that controls the orientation and crystal size of the second underlayer 15 and magnetic layer 16 that are provided thereon. Examples of the first underlayer 14 include a Cr layer, a Ta layer, a Ru layer, or a CrMo alloy layer, a CoW alloy layer, a CrW alloy layer, a CrV alloy layer, and a CrTi alloy layer. The first underlayer 14 can be formed by, for example, a sputtering method.

[0219] "Second Underlayer" The second underlayer 15 is a layer that controls the orientation of the magnetic layer 16 so that it is favorable. The second underlayer 15 is preferably a layer made of Ru or a Ru alloy. The second underlayer 15 may be a layer consisting of a single layer, or may be made of multiple layers. When the second underlayer 15 consists of multiple 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, for example, by a sputtering method.

[0220] "Magnetic Layer" The magnetic layer 16 is made of a magnetic film whose axis of easy magnetization is oriented perpendicular or horizontal to the substrate surface. The magnetic layer 16 is a layer containing Co and Pt. To improve the SNR characteristics, the magnetic layer 16 may be a layer containing oxides, Cr, B, Cu, Ta, Zr, etc. Examples of oxides contained in the magnetic layer 16 include SiO ２ , SiO, Cr ２ O ３ , CoO, Ta ２ O ３ , TiO ２ etc.

[0221] The magnetic layer 16 may be composed of a single layer, or may be composed of multiple magnetic layers made of materials with different compositions. For example, when the magnetic layer 16 is composed of three layers, a first magnetic layer, a second magnetic layer, and a third magnetic layer stacked in this order from the bottom, the first magnetic layer preferably has a granular structure made of a material containing Co, Cr, and Pt and further containing an oxide. As the oxide contained in the first magnetic layer, it is preferable to use an oxide of, for example, Cr, Si, Ta, Al, Ti, Mg, Co, or the like. Among them, TiO is particularly preferable. ２ , Cr ２ O ３ , SiO ２ The first magnetic layer is preferably made of a composite oxide containing two or more kinds of oxides. ２ O ３ -SiO ２ , Cr ２ O ３ -TiO ２ , SiO ２ -TiO２ The first magnetic layer may contain, in addition to Co, Cr, Pt, and oxides, one or more elements selected from B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb, Ru, and Re.

[0222] The second magnetic layer can be made of the same material as the first magnetic layer. The second magnetic layer preferably has a granular structure. The third magnetic layer preferably has a non-granular structure made of a material containing Co, Cr, and Pt and not containing oxides. In addition to Co, Cr, and Pt, the third magnetic layer can contain one or more elements selected from B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb, Ru, Re, and Mn.

[0223] When the magnetic layer 16 is formed of multiple magnetic layers, it is preferable to provide a non-magnetic layer between adjacent magnetic layers. When the magnetic layer 16 is formed of three layers, namely, a first magnetic layer, a second magnetic layer, and a third magnetic layer, it is preferable to provide a non-magnetic layer between the first magnetic layer and the second magnetic layer and between the second magnetic layer and the third magnetic layer.

[0224] The non-magnetic layer provided between adjacent magnetic layers of the magnetic layer 16 can be suitably made of, for example, Ru, a Ru alloy, a CoCr alloy, or a CoCrX1 alloy (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).

[0225] The non-magnetic layer provided between adjacent magnetic layers of the magnetic layer 16 is preferably made of an alloy material containing an oxide, a metal nitride, or a metal carbide. Specifically, the oxide may be, for example, SiO ２ , Al ２ O ３ , Ta ２ O ５ , Cr ２ O ３ , MgO, Y ２ O ３ , TiO ２ Examples of metal nitrides that can be used include AlN and Si. ３ N ４, TaN, CrN, etc. can be used as the metal carbide. TaC, BC, SiC, etc. can be used as the metal carbide. The non-magnetic layer can be formed by, for example, sputtering.

[0226] To achieve higher recording density, the magnetic layer 16 is preferably a magnetic layer for perpendicular magnetic recording, in which the axis of easy magnetization is oriented perpendicular to the substrate surface. The magnetic layer 16 may also be a magnetic layer for in-plane magnetic recording. The magnetic layer 16 may be formed by any conventionally known method, such as vapor deposition, ion beam sputtering, or magnetron sputtering. The magnetic layer 16 is usually formed by sputtering.

[0227] "Protective Layer" The protective layer 17 protects the magnetic layer 16. The protective layer 17 may be composed of one layer or multiple layers. Examples of materials for the protective layer 17 include carbon, nitrogen-containing carbon, and silicon carbide. A carbon-based protective layer can be preferably used as the protective layer 17, and an amorphous carbon protective layer is particularly preferred. If the protective layer 17 is a carbon-based protective layer, the interaction with the polar group contained in the fluorine-containing ether compound in the lubricating layer 18 is further enhanced, which is preferable.

[0228] The adhesion between the carbon-based protective layer and the lubricating layer 18 can be controlled by using hydrogenated carbon and / or nitrogenated carbon for the carbon-based protective layer and adjusting the hydrogen and / or nitrogen contents in the carbon-based protective layer. The hydrogen content in the carbon-based protective layer is preferably 3 atomic % to 20 atomic % as measured by hydrogen forward scattering (HFS). The nitrogen content in the carbon-based protective layer is preferably 4 atomic % to 15 atomic % as measured by X-ray photoelectron spectroscopy (XPS).

[0229] The hydrogen and / or nitrogen contained in the carbon-based protective layer does not need to be uniformly contained throughout the carbon-based protective layer. The carbon-based protective layer is preferably a compositionally graded layer, for example, in which nitrogen is contained on the lubricating layer 18 side of the protective layer 17 and hydrogen is contained on the magnetic layer 16 side of the protective layer 17. In this case, the adhesion between the magnetic layer 16 and the lubricating layer 18 and the carbon-based protective layer is further improved.

[0230] The thickness of the protective layer 17 is preferably 1 nm to 7 nm. When the thickness of the protective layer 17 is 1 nm or more, sufficient performance as the protective layer 17 can be obtained. When the thickness of the protective layer 17 is 7 nm or less, it is preferable from the viewpoint of making the protective layer 17 thinner.

[0231] The protective layer 17 can be formed by sputtering using a target material containing carbon, chemical vapor deposition (CVD) using a hydrocarbon raw material such as ethylene or toluene, ion beam deposition (IBD), or the like. When a carbon-based protective layer is formed as the protective layer 17, it can be formed by DC magnetron sputtering, for example. In particular, when a carbon-based protective layer is formed as the protective layer 17, it is preferable to form an amorphous carbon protective layer by plasma CVD. An amorphous carbon protective layer formed by plasma CVD has a uniform surface with little roughness.

[0232] "Lubricant Layer" The lubricant layer 18 prevents contamination of the magnetic recording medium 10. The lubricant layer 18 also reduces the frictional force of the magnetic head of the magnetic recording / reproducing device sliding on the magnetic recording medium 10, thereby improving the durability of the magnetic recording medium 10. As shown in FIG. 1 , the lubricant layer 18 is formed on and in contact with the protective layer 17. The lubricant layer 18 contains the above-mentioned fluorine-containing ether compound.

[0233] When the protective layer 17 disposed below the lubricating layer 18 is a carbon-based protective layer, the lubricating layer 18 bonds with the protective layer 17 with particularly high bonding strength. As a result, even if the thickness of the lubricating layer 18 is thin, it becomes easier to obtain a magnetic recording medium 10 in which the surface of the protective layer 17 is covered with a high coverage, and contamination of the surface of the magnetic recording medium 10 can be effectively prevented.

[0234] The average thickness of the lubricating layer 18 is preferably 0.5 nm (5 Å) to 2.0 nm (20 Å), and more preferably 0.5 nm (5 Å) to 1.0 nm (10 Å). When the average thickness of the lubricating layer 18 is 0.5 nm or more, the lubricating layer 18 is formed with a uniform thickness without forming an island or mesh-like structure. This allows the lubricating layer 18 to cover the surface of the protective layer 17 with a high coverage. Furthermore, by setting the average thickness of the lubricating layer 18 to 2.0 nm or less, the lubricating layer 18 can be made sufficiently thin, and the flying height of the magnetic head can be sufficiently reduced.

[0235] If the surface of the protective layer 17 is not covered with the lubricating layer 18 at a sufficiently high coverage rate, environmental substances adsorbed to the surface of the magnetic recording medium 10 will pass through the gaps in the lubricating layer 18 and penetrate into the layer below the lubricating layer 18. The environmental substances that penetrate into the layer below the lubricating layer 18 will adsorb and bond to the protective layer 17, generating contaminants. Then, during magnetic recording and reproduction, these contaminants (aggregated components) will adhere (transfer) to the magnetic head as smear, damaging the magnetic head or degrading the magnetic recording and reproduction characteristics of the magnetic recording and reproduction device.

[0236] Environmental substances that generate contaminants include, for example, siloxane compounds (cyclic siloxanes, linear siloxanes), ionic impurities, hydrocarbons with relatively high molecular weights such as octacosane, and plasticizers such as dioctyl phthalate. Examples of metal ions contained in ionic impurities include sodium ions and potassium ions. Examples of inorganic ions contained in ionic impurities include chloride ions, bromide ions, nitrate ions, sulfate ions, and ammonium ions. Examples of organic ions contained in ionic impurities include oxalate ions and formate ions.

[0237] "Method for forming lubricating layer" As a method for forming the lubricating layer 18, for example, a method is given in which a magnetic recording medium in the middle of manufacture in which each layer up to the protective layer 17 is formed on the substrate 11, and a solution for forming a lubricating layer is applied to the protective layer 17 and dried.

[0238] The lubricant layer-forming solution can be obtained by dissolving and dispersing the magnetic recording medium lubricant of the above-described embodiment in a solvent as needed, and adjusting the viscosity and concentration to suit the coating method. Examples of the solvent used in the lubricant layer-forming solution include fluorine-based solvents such as Vertrel (registered trademark) XF (trade name, manufactured by DuPont-Mitsui Fluorochemicals Co., Ltd.) and / or Asahiklin (registered trademark) AE-3000 (trade name, manufactured by AGC).

[0239] The method for applying the lubricant layer-forming solution is not particularly limited, and examples thereof include spin coating, spraying, paper coating, and dipping. When using the dipping method, the following method can be used, for example. First, the substrate 11 on which each layer up to the protective layer 17 has been formed is immersed in the lubricant layer-forming solution placed in the immersion tank of a dip coating device. Next, the substrate 11 is pulled out of the immersion tank at a predetermined speed. In this way, the lubricant layer-forming solution is applied to the surface of the protective layer 17 of the substrate 11. By using the dipping method, the lubricant layer-forming solution can be applied uniformly to the surface of the protective layer 17, and the lubricant layer 18 can be formed on the protective layer 17 with a uniform film thickness.

[0240] In this embodiment, it is preferable to perform a heat treatment on the substrate 11 on which the lubricating layer 18 is formed. By performing the heat treatment, the adhesion between the lubricating layer 18 and the protective layer 17 is improved, and the adhesive force between the lubricating layer 18 and the protective layer 17 is also improved. The heat treatment temperature is preferably 100 to 180°C. If the heat treatment temperature is 100°C or higher, the effect of improving the adhesion between the lubricating layer 18 and the protective layer 17 is sufficiently obtained. Furthermore, by setting the heat treatment temperature to 180°C or lower, thermal decomposition of the lubricating layer 18 can be prevented. The heat treatment time is preferably 10 to 120 minutes.

[0241] The magnetic recording medium 10 of this embodiment has at least a magnetic layer 16, a protective layer 17, and a lubricating layer 18 sequentially formed on a substrate 11. In the magnetic recording medium 10 of this embodiment, a lubricating layer 18 containing the above-mentioned fluorine-containing ether compound is formed on and in contact with the protective layer 17. This lubricating layer 18 has excellent adhesion to the protective layer 17, and even though it is thin, it can cover the surface of the protective layer 17 with a high coverage rate, has good adhesion to the protective layer, and has excellent pickup resistance. Therefore, the magnetic recording medium 10 of this embodiment allows a magnetic head to levitate stably, and has good long-term reliability and durability.

[0242] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0243] [Example 1] The compound represented by the above formula (1A) was obtained by the following method. ２ CF ２ O (CF ２ CF ２ O) ｐ (CF ２ O) ｑ CF ２ CH ２ 5.0 g of a compound (number average molecular weight: 997, molecular weight distribution: 1.1) represented by formula (1A-1) (where p, indicating the average degree of polymerization, is 4.5, and q, indicating the average degree of polymerization, is 4.5), 2.8 g of compound (1A-1) represented by formula (12) below (molecular weight: 266, 10.5 mmol), and 9.4 mL of t-butanol were charged and stirred at room temperature to form a mixed solution. 1.4 g of potassium tert-butoxide (molecular weight: 112, 12.5 mmol) was added to this mixed solution, and the mixture was reacted at 70°C for 8 hours with stirring.

[0244] (In formula (12), THP represents a tetrahydropyranyl group.)

[0245] Compound (1A-1) represented by formula (12) was produced by protecting the hydroxyl group of 1-amino-2-ethanol with 3,4-dihydro-2H-pyran and acylating the amino group of the resulting compound with bromoacetyl chloride.

[0246] The reaction solution obtained after the reaction was returned to room temperature, and 33 g of a 10% hydrogen chloride-methanol solution (hydrogen chloride-methanol reagent (5-10%), manufactured by Tokyo Chemical Industry Co., Ltd.) was added, followed by stirring at room temperature for 2 hours. The reaction solution was transferred little by little to a separatory funnel containing 100 mL of brine, and extracted three times with 200 mL of ethyl acetate. The organic layer was washed with 100 mL of brine, 100 mL of saturated sodium bicarbonate water, and 100 mL of brine, in that order, and then dehydrated using anhydrous sodium sulfate. After filtering off the desiccant, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 4.5 g (number average molecular weight 1198) of compound (1A) (in formula (1A), p1A, which indicates the average degree of polymerization, is 4.5, and q1A, which indicates the average degree of polymerization, is 4.5).

[0247] The obtained compound (1A) １ H-NMR and １９ F-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 3.45 to 4.45 (20H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -55.6 to -51.5 (9F), -78.5 (2F), -80.5 (2F), -91.2 to -88.4 (18F)

[0248] Example 2 The same operation as in Example 1 was performed, except that 3.1 g (molecular weight 294, 10.5 mmol) of compound (1B-1) represented by the following formula (13) was used instead of compound (1A-1) represented by the above formula (12), to obtain 4.4 g (number average molecular weight 1254) of compound (1B) (in formula (1B), p1B representing the average degree of polymerization is 4.5, and q1B representing the average degree of polymerization is 4.5).

[0249] (In formula (13), THP represents a tetrahydropyranyl group.)

[0250] Compound (1B-1) represented by formula (13) was produced by protecting the hydroxyl group of 1-amino-4-butanol with 3,4-dihydro-2H-pyran and acylating the amino group of the resulting compound with bromoacetyl chloride.

[0251] The obtained compound (1B) １ H-NMR and １９ F-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 0.75 to 1.54 (8H), 3.44 to 4.46 (20H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -55.6 to -51.5 (9F), -78.5 (2F), -80.5 (2F), -91.2 to -88.4 (18F)

[0252] Example 3 The same operation as in Example 1 was performed, except that 3.3 g (molecular weight 310, 10.5 mmol) of compound (1C-1) represented by the following formula (14) was used instead of compound (1A-1) represented by the above formula (12), to obtain 4.6 g (number average molecular weight 1286) of compound (1C) (in formula (1C), p1C indicating the average degree of polymerization is 4.5, and q1C indicating the average degree of polymerization is 4.5).

[0253] (In formula (14), THP represents a tetrahydropyranyl group.)

[0254] Compound (1C-1) represented by formula (14) was produced by reacting the hydroxyl group of 1-amino-2-ethanol with 2-(2-bromoethoxy)tetrahydro-2H-pyran, and then acylating the amino group of the resulting compound with bromoacetyl chloride.

[0255] The obtained compound (1C) １ H-NMR and １９ F-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 3.39 to 4.45 (28H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -55.6 to -51.5 (9F), -78.5 (2F), -80.5 (2F), -91.2 to -88.4 (18F)

[0256] [Example 4] HOCH ２ CF２ O (CF ２ CF ２ O) ｐ (CF ２ O) ｑ CF ２ CH ２ OH (where p indicating the average degree of polymerization is 4.5, and q indicating the average degree of polymerization is 4.5), ２ CF ２ O (CF ２ CF ２ O) ｐ (CF ２ O) ｑ CF ２ CH ２ The same operations as in Example 1 were performed, except that 5.0 g of a compound (number average molecular weight: 1000, molecular weight distribution: 1.1) represented by formula (1D-1) below (in which p representing the average degree of polymerization is 7.1, and q representing the average degree of polymerization is 0) was used, and 4.1 g (molecular weight: 394, 10.5 mmol) of compound (1D-1) represented by formula (15) below was used instead of compound (1A-1) represented by formula (12) above, to obtain 4.3 g (number average molecular weight: 1291) of compound (1D) (in formula (1D), p1D representing the average degree of polymerization is 7.1, and q1D representing the average degree of polymerization is 0).

[0257] (In formula (15), THP represents a tetrahydropyranyl group.)

[0258] Compound (1D-1) represented by formula (15) was prepared by protecting the two hydroxyl groups of diethanolamine with 3,4-dihydro-2H-pyran and acylating the amino group of the resulting compound with bromoacetyl chloride.

[0259] The obtained compound (1D) １ H-NMR and １９ F-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 3.35 to 4.50 (28H) １９ F-NMR (acetone-D ６): δ [ppm] = -78.6 (2F), -81.3 (2F), -91.0 to -88.0 (28.4F)

[0260] Example 5 The same operation as in Example 4 was performed, except that 2.7 g (molecular weight 259, 10.5 mmol) of compound (1E-1) represented by the following formula (16) and 0.1 g (molecular weight 112, 1.0 mmol) of potassium tert-butoxide were used instead of compound (1D-1) represented by formula (15) above, to obtain 4.2 g (number average molecular weight 1351) of compound (1E) (in formula (1E), p1E indicating the average degree of polymerization is 7.1, and q1E indicating the average degree of polymerization is 0).

[0261] (In formula (16), THP represents a tetrahydropyranyl group.)

[0262] Compound (1E-1) represented by formula (16) was synthesized by the following method. First, the hydroxyl group of 1-amino-2-ethanol was protected using 3,4-dihydro-2H-pyran. The amino group of the obtained compound was acylated using acetoxyacetyl chloride. Thereafter, the acetyl group bonded to the hydroxyl group was deprotected, and the resulting hydroxyl group was reacted with epibromohydrin to produce compound (1E-1).

[0263] The obtained compound (1E) １ H-NMR and １９ F-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 3.27 to 4.55 (32H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -78.6 (2F), -81.3 (2F), -91.0 to -88.0 (28.4F)

[0264] [Example 6] (First Reaction) In a 300 mL recovery flask, HOCH ２ CF ２ O (CF ２ CF ２ O) ｐ (CF ２ O) ｑ CF２ CH ２ 5.0 g of a compound (number average molecular weight: 1000, molecular weight distribution: 1.1) represented by formula (17), 3.8 g of compound (1F-1) represented by formula (17) below (molecular weight: 363, 10.5 mmol), and 9.4 mL of t-butanol were charged and stirred at room temperature to prepare a mixed solution. 1.4 g of potassium tert-butoxide (molecular weight: 112, 12.5 mmol) was added to this mixed solution, and the mixture was reacted at 70°C for 8 hours with stirring.

[0265] (In formula (17), Bn represents a benzyl group, and Ts represents a p-toluenesulfonyl group.)

[0266] Compound (1F-1) represented by formula (17) was produced by acylating the amino group of 1-amino-2-ethanol with benzyloxyacetyl chloride, and then reacting the hydroxyl group with p-toluenesulfonyl chloride.

[0267] The reaction product obtained after the reaction was cooled to 25°C, transferred to a separatory funnel containing 100 mL of water, and extracted three times with 100 mL of ethyl acetate. The organic layer was washed with water and dehydrated with anhydrous sodium sulfate. After filtering off the desiccant, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 4.5 g (number average molecular weight 1384) of intermediate compound (1F-2) represented by the following formula (18).

[0268] (In formula (18), Bn represents a benzyl group, p representing the average degree of polymerization is 7.1, and q representing the average degree of polymerization is 0.)

[0269] (Second Reaction) Under a nitrogen gas atmosphere, 4.5 g of the intermediate compound (1F-2) represented by formula (18) (number average molecular weight: 1384, 3.3 mmol), 45 mL of methanol, and 4.5 mL of formic acid were placed in a 200 mL recovery flask and stirred at room temperature until the mixture became homogeneous. 0.45 g of palladium on carbon (Pd / C) was added to the homogeneous solution, and the mixture was stirred at 70°C for 8 hours to react.

[0270] The reaction solution obtained after the reaction was filtered to remove Pd / C, and the filtrate was concentrated. After concentration, the residue was purified by silica gel column chromatography to obtain 3.5 g of compound (1F) (in formula (1F), p1F indicating the average degree of polymerization is 7.1, and q1F indicating the average degree of polymerization is 0) (number average molecular weight 1201).

[0271] The obtained compound (1F) １ H-NMR and １９ F-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 3.32 to 4.30 (20H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -78.6 (2F), -81.3 (2F), -91.0 to -88.0 (28.4F)

[0272] [Example 7] HOCH ２ CF ２ O (CF ２ CF ２ O) ｐ (CF ２ O) ｑ CF ２ CH ２ OH (where p indicating the average degree of polymerization is 7.1, and q indicating the average degree of polymerization is 0), ２ CF ２ CF ２ O (CF ２ CF ２ CF ２ O) ｒ CF ２ CF ２ CH ２ The same operation as in Example 6 was performed except that 5.0 g of a compound (number average molecular weight: 1008, molecular weight distribution: 1.1) represented by formula (1H-H) (in which r, representing the average degree of polymerization, is 4.4) was used, and 4.1 g (molecular weight: 391, 10.5 mmol) of compound (1G-1) represented by formula (19) below was used instead of compound (1F-1) represented by formula (17) above, to obtain 3.6 g (number average molecular weight: 1264) of compound (1G) (in formula (1G), r, representing the average degree of polymerization, is 4.4).

[0273] (In formula (19), Bn represents a benzyl group, and Ts represents a p-toluenesulfonyl group.)

[0274] Compound (1G-1) represented by formula (19) was produced by acylating the amino group of 1-amino-2-ethanol with 4-benzyloxybutanoyl chloride, and then reacting the hydroxyl group with p-toluenesulfonyl chloride.

[0275] The obtained compound (1G) １ H-NMR and １９ F-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 0.80 to 1.50 (4H), 1.90 to 2.40 (4H), 3.30 to 4.44 (20H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.3 to -82.8 (17.6F), -86.4 (4F), -124.0 (4F), -130.0 to -128.2 (8.8F)

[0276] Example 8 The same operation as in Example 7 was performed, except that 4.1 g (molecular weight 391, 10.5 mmol) of compound (1H-1) represented by the following formula (20) was used instead of compound (1G-1) represented by formula (19) above, to obtain 3.6 g (number average molecular weight 1263) of compound (1H) (in formula (1H), r1H representing the average degree of polymerization is 4.4).

[0277] (In formula (20), Bn represents a benzyl group, and Ts represents a p-toluenesulfonyl group.)

[0278] Compound (1H-1) represented by formula (20) was produced by acylating the amino group of 1-amino-3-propanol with 3-benzyloxypropanoyl chloride, and then reacting the hydroxyl group with p-toluenesulfonyl chloride.

[0279] The obtained compound (1H) １ H-NMR and １９ F-NMR measurement was carried out, and the structure was identified from the following results.１ H-NMR (acetone-D ６ ): δ [ppm] = 0.70 to 1.45 (4H), 1.90 to 2.35 (4H), 3.32 to 4.45 (20H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.3 to -82.8 (17.6F), -86.4 (4F), -124.0 (4F), -130.0 to -128.2 (8.8F)

[0280] Example 9 The same operation as in Example 7 was carried out, except that 2.9 g (molecular weight 279, 10.5 mmol) of compound (1I-1) represented by the following formula (21) and 0.1 g (molecular weight 112, 1.0 mmol) of potassium tert-butoxide were used instead of compound (1G-1) represented by formula (19) above, to obtain 3.8 g (number average molecular weight 1384) of compound (1I) (in formula (1I), r1I, which indicates the average degree of polymerization, is 4.4).

[0281] (In formula (21), Bn represents a benzyl group.)

[0282] Compound (1I-1) represented by formula (21) was produced by acylating the amino group of 1-amino-2-ethanol with 3-benzyloxypropanoyl chloride, followed by reacting the hydroxyl group with epibromohydrin.

[0283] The obtained compound (1I) １ H-NMR and １９ F-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 1.90 to 2.35 (4H), 3.27 to 4.45 (32H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.3 to -82.8 (17.6F), -86.4 (4F), -124.0 (4F), -130.0 to -128.2 (8.8F)

[0284] Example 10 The same operation as in Example 9 was performed, except that 3.1 g (molecular weight 293, 10.5 mmol) of compound (1J-1) represented by the following formula (22) was used instead of compound (1I-1) represented by the above formula (21), to obtain 3.9 g (number average molecular weight 1411) of compound (1J) (in formula (1J), r1J representing the average degree of polymerization is 4.4).

[0285] (In formula (22), Bn represents a benzyl group.)

[0286] Compound (1J-1) represented by formula (22) was produced by acylating the amino group of 1-amino-2-ethanol with 3-benzyloxypropanoyl chloride, reacting the hydroxyl group with 4-bromo-1-butene, and oxidizing the double bond site of the resulting compound with mCPBA.

[0287] The obtained compound (1J) １ H-NMR and １９ F-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 0.90 to 1.35 (4H), 1.90 to 2.34 (4H), 3.32 to 4.55 (32H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.3 to -82.8 (17.6F), -86.4 (4F), -124.0 (4F), -130.0 to -128.2 (8.8F)

[0288] [Example 11] The compound represented by the above formula (2A) was obtained by the following method. (First reaction) HOCH ２ CF ２ O (CF ２ CF ２ O) ｐ (CF ２ O) ｑ CF ２ CH ２5.0 g of a compound (number average molecular weight: 997, molecular weight distribution: 1.1) represented by formula (2A-1) (where p, indicating the average degree of polymerization, is 4.5, and q, indicating the average degree of polymerization, is 4.5), 1.7 g of compound (2A-1) represented by formula (23) below (molecular weight: 158, 10.5 mmol), and 9.4 mL of t-butanol were charged and stirred at room temperature to form a mixed solution. 0.1 g of potassium tert-butoxide (molecular weight: 112, 1.0 mmol) was added to this mixed solution, and the mixture was reacted at 70°C for 8 hours with stirring.

[0289] (In formula (23), THP represents a tetrahydropyranyl group.)

[0290] The reaction product obtained after the reaction was cooled to 25°C, transferred to a separatory funnel containing 100 mL of water, and extracted three times with 100 mL of ethyl acetate. The organic layer was washed with water and dehydrated with anhydrous sodium sulfate. After filtering off the desiccant, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 4.6 g (number average molecular weight 1313) of intermediate compound (2A-2) represented by the following formula (24).

[0291] (In formula (24), THP represents a tetrahydropyranyl group. p, which represents the average degree of polymerization, is 4.5, and q, which represents the average degree of polymerization, is 4.5.)

[0292] (Second Reaction) Under a nitrogen gas atmosphere, 4.6 g (number average molecular weight 1313, 3.5 mmol) of intermediate compound (2A-2) represented by formula (24), 1.3 g (molecular weight 152, 8.7 mmol) of 2-bromo-N-methylacetamide, and 7 mL of DMF were placed in a 200 mL recovery flask and stirred at room temperature until a homogeneous mixture was obtained. 4.5 g (molecular weight 325, 14.0 mmol) of cesium carbonate was added to the homogeneous mixture, and the mixture was stirred at 70°C for 8 hours to react.

[0293] The reaction solution obtained after the reaction was returned to room temperature, and 23 g of a 10% hydrogen chloride-methanol solution (hydrogen chloride-methanol reagent (5-10%), manufactured by Tokyo Chemical Industry Co., Ltd.) was added, followed by stirring at room temperature for 2 hours. The reaction solution was transferred little by little to a separatory funnel containing 100 mL of brine, and extracted three times with 200 mL of ethyl acetate. The organic layer was washed with 100 mL of brine, 100 mL of saturated sodium bicarbonate water, and 100 mL of brine, in that order, and then dehydrated using anhydrous sodium sulfate. After filtering off the desiccant, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 3.5 g (number average molecular weight 1286) of compound (2A) (in formula (2A), p2A, which indicates the average degree of polymerization, is 4.5, and q2A, which indicates the average degree of polymerization, is 4.5).

[0294] The obtained compound (2A) １ H-NMR and １９ F-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 2.65 to 2.80 (6H), 3.40 to 4.42 (22H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -55.6 to -51.5 (9F), -78.5 (2F), -80.5 (2F), -91.2 to -88.4 (18F)

[0295] [Example 12] The compound represented by the above formula (2B) was obtained by the following method. (First reaction) HOCH ２ CF ２ O (CF ２ CF ２ O) ｐ (CF ２ O) ｑ CF ２ CH ２5.0 g of a compound (number average molecular weight: 997, molecular weight distribution: 1.1) represented by formula (2B-1) (where p, indicating the average degree of polymerization, is 4.5, and q, indicating the average degree of polymerization, is 4.5), 4.1 g of compound (2B-1) represented by formula (25) below (molecular weight: 266, 10.5 mmol), and 9.4 mL of t-butanol were charged and stirred at room temperature to form a mixed solution. 1.4 g of potassium tert-butoxide (molecular weight: 112, 12.5 mmol) was added to this mixed solution, and the mixture was reacted at 70°C for 8 hours with stirring.

[0296] (In formula (25), Bn represents a benzyl group, and Ts represents a p-toluenesulfonyl group.)

[0297] Compound (2B-1) represented by formula (25) was synthesized by the following method. First, the primary hydroxyl group of 3-(hydroxymethyl)oxolan-2-one was protected using 3,4-dihydro-2H-pyran. The resulting compound was reacted with methylamine to open the lactone ring and obtain an amide compound. Thereafter, the resulting hydroxyl group was protected with a benzyl group, and the tetrahydropyranyl (THP) group was deprotected. The resulting hydroxyl group was then reacted with p-toluenesulfonyl chloride to produce compound (2B-1).

[0298] The reaction product obtained after the reaction was cooled to 25°C, transferred to a separatory funnel containing 100 mL of water, and extracted three times with 100 mL of ethyl acetate. The organic layer was washed with water and dehydrated with anhydrous sodium sulfate. After filtering off the desiccant, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 4.5 g (number average molecular weight 1435) of intermediate compound (2B-2) represented by the following formula (26).

[0299] (In formula (26), Bn represents a benzyl group, p representing the average degree of polymerization is 4.5, and q representing the average degree of polymerization is 4.5.)

[0300] (Second Reaction) Under a nitrogen gas atmosphere, 4.5 g of the intermediate compound (2B-2) represented by formula (26) (number average molecular weight: 1435, 3.1 mmol), 45 mL of methanol, and 4.5 mL of formic acid were placed in a 200 mL recovery flask and stirred at room temperature until the mixture became homogeneous. 0.45 g of palladium on carbon (Pd / C) was added to the homogeneous solution, and the mixture was allowed to react at 70°C for 8 hours with stirring.

[0301] The reaction solution obtained after the reaction was filtered to remove Pd / C, and the filtrate was concentrated. After concentration, the residue was purified by silica gel column chromatography to obtain 3.6 g (number average molecular weight 1252) of compound (2B) (in formula (2B), p2B indicating the average degree of polymerization is 4.5, and q2B indicating the average degree of polymerization is 4.5).

[0302] The obtained compound (2B) １ H-NMR and １９ F-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 0.80 to 1.45 (4H), 1.90 to 2.35 (2H), 2.65 to 2.80 (6H), 3.38 to 4.40 (16H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -55.6 to -51.5 (9F), -78.5 (2F), -80.5 (2F), -91.2 to -88.4 (18F)

[0303] Example 13 The same operation as in Example 12 was performed, except that 4.3 g (molecular weight 405, 10.5 mmol) of compound (2C-1) represented by the following formula (27) was used instead of compound (2B-1) represented by the above formula (25), to obtain 3.7 g (number average molecular weight 1280) of compound (2C) (in formula (2C), p2C indicating the average degree of polymerization is 4.5, and q2C indicating the average degree of polymerization is 4.5).

[0304] (In formula (27), Bn represents a benzyl group, and Ts represents a p-toluenesulfonyl group.)

[0305] Compound (2C-1) represented by formula (27) was produced by reacting ethyl 3-hydroxy-2-(hydroxymethyl)propionate with propylamine to form an amide compound, protecting one hydroxyl group in the obtained amide compound with a benzyl group, and reacting the other hydroxyl group with p-toluenesulfonyl chloride.

[0306] The obtained compound (2C) １ H-NMR and １９ F-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 0.75 to 1.20 (6H), 1.50 to 1.80 (4H), 1.90 to 2.35 (2H), 3.00 to 4.42 (20H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -55.6 to -51.5 (9F), -78.5 (2F), -80.5 (2F), -91.2 to -88.4 (18F)

[0307] [Example 14] HOCH ２ CF ２ O (CF ２ CF ２ O) ｐ (CF ２ O) ｑ CF ２ CH ２ OH (where p indicating the average degree of polymerization is 4.5, and q indicating the average degree of polymerization is 4.5), ２ CF ２ O (CF ２ CF ２ O) ｐ (CF ２ O) ｑ CF ２ CH ２The same operation as in Example 12 was performed except that 5.0 g of a compound (number average molecular weight: 1000, molecular weight distribution: 1.1) represented by formula (2D-1) below (in which p2D indicating the average degree of polymerization is 7.1, and q2D indicating the average degree of polymerization is 0) was used, and 4.3 g (molecular weight: 405, 10.5 mmol) of compound (2D-1) represented by formula (28) below was used instead of compound (2B-1) represented by formula (25) above, to obtain 3.7 g (number average molecular weight: 1284) of compound (2D) (in formula (2D), p2D indicating the average degree of polymerization is 7.1, and q2D indicating the average degree of polymerization is 0).

[0308] (In formula (28), Bn represents a benzyl group, and Ts represents a p-toluenesulfonyl group.)

[0309] Compound (2D-1) represented by formula (28) was synthesized by the following method. First, the primary hydroxyl group of 4-(2-hydroxyethyl)oxolan-2-one was protected with a benzyl group. The resulting compound was reacted with methylamine to open the lactone ring and obtain an amide compound. Then, the resulting hydroxyl group was reacted with p-toluenesulfonyl chloride to produce compound (2D-1).

[0310] The obtained compound (2D) １ H-NMR and １９ F-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 0.80 to 1.43 (6H), 1.80 to 2.40 (4H), 2.65 to 2.80 (6H), 3.32 to 4.30 (16H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -78.6 (2F), -81.3 (2F), -91.0 to -88.0 (28.4F)

[0311] Example 15 The same operation as in Example 14 was performed, except that 4.5 g (molecular weight 421, 10.5 mmol) of compound (2E-1) represented by the following formula (29) was used instead of compound (2D-1) represented by formula (28), to obtain 3.8 g (number average molecular weight 1335) of compound (2E) (in formula (2E), p2E indicating the average degree of polymerization is 7.1, and q2E indicating the average degree of polymerization is 0).

[0312] (In formula (29), Bn represents a benzyl group, and Ts represents a p-toluenesulfonyl group.)

[0313] Compound (2E-1) represented by formula (29) was synthesized by the following method. First, ethyl 3-hydroxy-2-(hydroxymethyl)propionate was reacted with methylamine to form an amide compound. Then, one of the hydroxyl groups in the obtained amide compound was protected with a benzyl group, and the other hydroxyl group was reacted with 1,2-bis(tosyloxy)ethane to produce the compound.

[0314] The obtained compound (2E) １ H-NMR and １９ F-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 1.85 to 2.35 (2H), 2.65 to 2.80 (6H), 3.32 to 4.30 (24H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -78.6 (2F), -81.3 (2F), -91.0 to -88.0 (28.4F)

[0315] [Example 16] In the first reaction, HOCH ２ CF ２ O (CF ２ CF ２ O) ｐ (CF ２ O) ｑ CF ２ CH ２ OH (where p indicating the average degree of polymerization is 4.5, and q indicating the average degree of polymerization is 4.5), ２ CF ２ O (CF２ CF ２ O) ｐ (CF ２ O) ｑ CF ２ CH ２ The same operations as in Example 11 were performed except that 5.0 g of a compound (number average molecular weight: 1000, molecular weight distribution: 1.1) represented by OH (in the formula, p2F indicating the average degree of polymerization is 7.1, and q2F indicating the average degree of polymerization is 0) was used, and 1.5 g of N-(2-bromoethyl)acetamide (molecular weight: 166, 8.7 mmol) was used instead of 2-bromo-N-methylacetamide in the second reaction, to obtain 3.5 g (number average molecular weight: 1318) of compound (2F) (in formula (2F), p2F indicating the average degree of polymerization is 7.1, and q2F indicating the average degree of polymerization is 0).

[0316] The obtained compound (2F) １ H-NMR and １９ F-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 1.85 to 2.30 (6H), 3.32 to 4.30 (26H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -78.6 (2F), -81.3 (2F), -91.0 to -88.0 (28.4F)

[0317] [Example 17] In the first reaction, HOCH ２ CF ２ O (CF ２ CF ２ O) ｐ (CF ２ O) ｑ CF ２ CH ２ OH (where p indicating the average degree of polymerization is 7.1, and q indicating the average degree of polymerization is 0), ２ CF ２ CF ２ O (CF ２ CF ２ CF ２ O) ｒ CF ２ CF ２ CH ２The same operations as in Example 11 were performed except that 5.0 g of a compound (number average molecular weight: 1008, molecular weight distribution: 1.1) represented by formula (OH) (in which r, indicating the average degree of polymerization, is 4.4) was used, 1.8 g (molecular weight: 172, 10.5 mmol) of compound (2G-1) represented by formula (30) below was used instead of compound (2A-1) represented by formula (23), and 1.4 g (molecular weight: 166, 8.7 mmol) of N-(2-bromoethyl)acetamide was used instead of 2-bromo-N-methylacetamide in the second reaction, to obtain 3.6 g (number average molecular weight: 1353) of compound (2G) (in formula (2G), r, indicating the average degree of polymerization, is 4.4).

[0318] (In formula (30), THP represents a tetrahydropyranyl group.)

[0319] The obtained compound (2G) １ H-NMR and １９ F-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 0.80 to 1.35 (4H), 1.85 to 2.30 (6H), 3.20 to 4.55 (26H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.3 to -82.8 (17.6F), -86.4 (4F), -124.0 (4F), -130.0 to -128.2 (8.8F)

[0320] Example 18 The same operations as in Example 17 were performed, except that in the first reaction, 2.3 g (molecular weight 216, 10.5 mmol) of compound (2H-1) represented by the following formula (31) was used instead of compound (2G-1) represented by the above formula (30), and in the second reaction, 1.4 g (molecular weight 180, 8.0 mmol) of N-(3-bromopropyl)acetamide was used instead of N-(2-bromoethyl)acetamide, to obtain 3.4 g (number average molecular weight 1470) of compound (2H) (in formula (2H), r2H representing the average degree of polymerization is 4.4).

[0321] (In formula (31), THP represents a tetrahydropyranyl group.)

[0322] Compound (2H-1) represented by formula (31) was obtained by reacting 3-buten-1-ol with 2-(2-bromoethoxy)tetrahydro-2H-pyran, and then oxidizing the double bond of the obtained compound with mCPBA.

[0323] The obtained compound (2H) １ H-NMR and １９ F-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 0.75 to 1.58 (8H), 1.85 to 2.30 (6H), 3.23 to 4.63 (32H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.3 to -82.8 (17.6F), -86.4 (4F), -124.0 (4F), -130.0 to -128.2 (8.8F)

[0324] [Example 19] HOCH ２ CF ２ O (CF ２ CF ２ O) ｐ (CF ２ O) ｑ CF ２ CH ２ OH (where p indicating the average degree of polymerization is 4.5, and q indicating the average degree of polymerization is 4.5), ２ CF ２ CF ２ O (CF ２ CF ２ CF ２ O) ｒ CF ２ CF ２ CH ２The same operation as in Example 12 was performed except that 5.0 g of a compound (number average molecular weight: 1008, molecular weight distribution: 1.1) represented by formula (OH) (in which r, representing the average degree of polymerization, is 4.4) was used, and 4.1 g (molecular weight: 391, 10.5 mmol) of compound (2I-1) represented by formula (32) below was used instead of compound (2B-1) represented by formula (25) above, to obtain 3.7 g (number average molecular weight: 1262) of compound (2I) (in formula (2I), r, representing the average degree of polymerization, is 4.4).

[0325] (In formula (32), Bn represents a benzyl group, and Ts represents a p-toluenesulfonyl group.)

[0326] Compound (2I-1) represented by formula (32) was synthesized by the following method. First, the primary hydroxyl group of homoserine was protected using 3,4-dihydro-2H-pyran. Next, the amino group was acetylated, and the carboxyl group of the resulting compound was reduced. Thereafter, the resulting hydroxyl group was protected with a benzyl group, the tetrahydropyranyl (THP) group was deprotected, and the resulting compound was reacted with p-toluenesulfonyl chloride to produce compound (2I-1).

[0327] The obtained compound (2I) １ H-NMR and １９ F-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 0.75 to 1.35 (4H), 1.85 to 2.30 (6H), 3.12 to 4.34 (18H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.3 to -82.8 (17.6F), -86.4 (4F), -124.0 (4F), -130.0 to -128.2 (8.8F)

[0328] Example 20 The same operation as in Example 19 was performed, except that 5.3 g (molecular weight 511, 10.5 mmol) of compound (2J-1) represented by the following formula (33) was used instead of compound (2I-1) represented by the above formula (32), to obtain 3.5 g (number average molecular weight 1320) of compound (2J) (in formula (2J), r2J representing the average degree of polymerization is 4.4).

[0329] (In formula (33), Bn represents a benzyl group, and Ts represents a p-toluenesulfonyl group.)

[0330] Compound (2J-1) represented by formula (33) was synthesized by the following method. First, the primary hydroxyl group of 2-amino-5-hydroxypropionic acid was protected using 3,4-dihydro-2H-pyran. Next, the amino group was acylated using benzyloxyacetyl chloride, and the carboxyl group of the resulting compound was reduced. Thereafter, the resulting hydroxyl group was protected with a benzyl group, the tetrahydropyranyl (THP) group was deprotected, and the resulting compound was reacted with p-toluenesulfonyl chloride to produce compound (2J-1).

[0331] The obtained compound (2J) １ H-NMR and １９ F-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 0.75 to 1.43 (8H), 3.12 to 4.54 (24H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.3 to -82.8 (17.6F), -86.4 (4F), -124.0 (4F), -130.0 to -128.2 (8.8F)

[0332] The compounds (1A) to (1J) and (2A) to (2J) of Examples 1 to 20 thus obtained were each substituted into formula (1) to give R １ , R ２ , R ３ The structures of the compounds are shown in Tables 1 to 4.

[0333]

[0334]

[0335]

[0336]

[0337] Comparative Example 1 Compound (3A) represented by the following formula (35) was synthesized by the method described in Patent Document 2.

[0338] (In formula (35), p, which indicates the average degree of polymerization, is 4.5, and q is 4.5.)

[0339] Comparative Example 2 Compound (3B) represented by the following formula (36) was synthesized by the method described in Patent Document 2.

[0340] (In formula (36), p, which indicates the average degree of polymerization, is 4.5, and q is 4.5.)

[0341] [Comparative Example 3] Compound (3C) represented by the following formula (37) was synthesized by the following method. First, the hydroxyl group of glycolylpiperidine was reacted with epibromohydrin to synthesize an epoxy compound having an amide group. Next, HOCH ２ CF ２ CF ２ O (CF ２ CF ２ CF ２ O) ｒ CF ２ CF ２ CH ２ A compound (number average molecular weight: 1,000, molecular weight distribution: 1.1) represented by OH (where r, which indicates the average degree of polymerization, is 4.5), the above epoxy compound having an amide group, and t-butanol were charged and stirred at room temperature until homogenous to obtain a mixture. Potassium tert-butoxide was added to this mixture, and the mixture was reacted by stirring at 70°C for 16 hours.

[0342] The reaction mixture was then transferred little by little to a separatory funnel containing brine and extracted twice with ethyl acetate. The organic layer was washed with brine, saturated sodium bicarbonate water, and brine, in that order, and then dehydrated over anhydrous sodium sulfate. After filtering off the desiccant, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain compound (3C).

[0343] (In formula (37), r, which indicates the average degree of polymerization, is 4.5.)

[0344] [Comparative Example 4] Compound (3D) represented by the following formula (38) was synthesized with reference to the method described in Patent Document 3. More specifically, compound (3D) was produced with reference to the method described in Example 1 of Patent Document 3, using glycidyl 4-acetaminophenyl ether instead of the glycidyl phenyl ether used in Example 1 of Patent Document 3.

[0345] (In formula (38), p, which indicates the average degree of polymerization, is 4.5, and q is 4.5.)

[0346] [Comparative Example 5] Compound (3E) represented by the following formula (39) was synthesized with reference to the method described in Patent Document 4. More specifically, compound (3E) was produced with reference to the method described in Example 1 of Patent Document 4, using 2-(2-aminoethoxy)ethanol instead of 3-amino-1,2-propanediol used in Example 1 of Patent Document 4.

[0347] (In formula (39), p, which indicates the average degree of polymerization, is 4.5, and q is 4.5.)

[0348] The number average molecular weights (Mn) of the compounds of Examples 1 to 20 and Comparative Examples 1 to 5 thus obtained were determined by the method described above. １ H-NMR and １９ The average molecular weight of the synthesized compounds was determined from the results of F-NMR measurements. The results are shown in Tables 5 and 6. It is estimated that there is a variation of about 1 to 5 in the average molecular weight of the synthesized compounds due to the molecular weight distribution of the fluoropolyethers used as raw materials for the compounds and differences in the operations used to synthesize the compounds.

[0349]

[0350]

[0351] Next, solutions for forming lubricating layers were prepared by the method described below using the compounds obtained in Examples 1 to 20 and Comparative Examples 1 to 5. Then, using the obtained solutions for forming lubricating layers, lubricating layers for magnetic recording media were formed by the method described below, thereby obtaining the magnetic recording media of Examples 1 to 20 and Comparative Examples 1 to 5.

[0352] "Lubricant Layer-Forming Solution" Each of the fluorine-containing ether compounds obtained in Examples 1 to 20 and Comparative Examples 1 to 5 was dissolved in a fluorine-based solvent, Vertrel (registered trademark) XF (trade name, manufactured by DuPont-Mitsui Fluorochemicals Co., Ltd.), and diluted with Vertrel XF so that the film thickness when applied to the protective layer would be 9 Å to 10 Å, to prepare a lubricant layer-forming solution.

[0353] "Magnetic Recording Media" A magnetic recording medium was prepared by sequentially depositing an adhesive layer, a soft magnetic layer, a first underlayer, a second underlayer, a magnetic layer, and a protective layer on a 65 mm diameter substrate. The protective layer was made of carbon. The lubricating layer-forming solutions of Examples 1 to 20 and Comparative Examples 1 to 5 were each applied by dipping onto the protective layer of the magnetic recording medium, on which each of the layers up to the protective layer had been formed. The dipping was performed under conditions of an immersion speed of 10 mm / sec, an immersion time of 30 seconds, and a withdrawal speed of 1.2 mm / sec. The magnetic recording medium coated with the lubricating layer-forming solution was then placed in a thermostatic chamber at 120°C and heated for 10 minutes to remove the solvent in the lubricating layer-forming solution, thereby forming a lubricating layer on the protective layer and obtaining a magnetic recording medium.

[0354] "Film Thickness Measurement" The peak heights of the C-F vibrational stretching of the lubricating layers of the magnetic recording media of Examples 1 to 20 and Comparative Examples 1 to 5 obtained in this manner were measured using an FT-IR (product name: Nicolet iS50, manufactured by Thermo Fisher Scientific). Next, using a correlation equation obtained by the method described below, the film thickness of the lubricating layer was calculated from the measured values ​​of the peak heights of the C-F vibrational stretching of the lubricating layer.

[0355] "Method of calculating the correlation equation" A disk was prepared, which had an adhesive layer, a soft magnetic layer, a first underlayer, a second underlayer, a magnetic layer, and a protective layer formed in that order on a substrate with a diameter of 65 mm. A lubricating layer was formed on the protective layer of this disk, with a thickness of 6 to 20 Å (in 2 Å increments).

[0356] Then, for each disk on which a lubricating layer was formed, an ellipsometer was used to measure the increase in film thickness from the disk surface on which a lubricating layer was not formed, and this was taken as the lubricating layer film thickness. Furthermore, for each disk on which a lubricating layer was formed, the peak height of the C-F vibrational stretching was measured using FT-IR. A correlation equation was then determined between the peak height obtained by FT-IR and the lubricating layer film thickness obtained using the ellipsometer.

[0357] Next, the magnetic recording media of Examples 1 to 20 and Comparative Examples 1 to 5 were evaluated by measuring the bond ratio and conducting a pickup characteristic test according to the following methods. The results are shown in Tables 5 and 6.

[0358] [Measurement of Adhesion (Bonding Ratio) Between Lubricating Layer and Protective Layer] After measuring the thickness of the lubricating layer of the magnetic recording medium formed with the lubricating layer using the method described above, the magnetic recording medium was immersed in a solvent, Vertrel XF, for 10 minutes and then removed for cleaning. The magnetic recording medium was immersed in the solvent at a speed of 10 mm / sec and removed at a speed of 1.2 mm / sec. The thickness of the lubricating layer after immersion in the solvent (after cleaning) was then measured using the same method as that used to measure the thickness of the lubricating layer before cleaning.

[0359] The film thickness of the lubricating layer before cleaning was defined as α, and the film thickness of the lubricating layer after cleaning (after solvent immersion) was defined as β. The bonding ratio of the lubricant (bond ratio) was calculated from the ratio of α to β ((β / α) × 100 (%)). Using the calculated bond ratio, the adhesion between the lubricating layer and the protective layer was evaluated according to the following criteria. The bond ratio can be used as an index representing the bonding strength between the lubricating layer and the protective layer. If the adhesion between the lubricating layer and the protective layer is poor, part of the fluorine-containing ether compound contained in the lubricating layer will dissolve into the Vertrel XF and be washed away. As a result, the film thickness of the lubricating layer after cleaning becomes smaller, and the bond ratio decreases.

[0360] "Adhesion (bond ratio) evaluation criteria" A: Bond ratio 65% or more B: Bond ratio 60% or more to less than 65% C: Bond ratio 40% or more to less than 60% D: Bond ratio less than 40%

[0361] [Pickup characteristic test] The magnetic recording medium and magnetic head were mounted on a spin stand and rotated under reduced pressure (approximately 250 torr) at room temperature, allowing the magnetic head to float at a fixed point for 10 minutes. The surface of the magnetic head facing the magnetic recording medium was then analyzed using an ESCA (Electron Spectroscopy for Chemical Analysis) analyzer. The intensity of the fluorine-derived peak (signal intensity (a.u.)) obtained by analysis using the ESCA analyzer indicates the amount of lubricant attached to the magnetic head. The obtained signal intensity was used to evaluate the pickup characteristics according to the following evaluation criteria.

[0362] "Evaluation criteria" A: Signal strength less than 160 (very little adhesion amount) B: Signal strength 160 or more but less than 300 (little adhesion amount) C: Signal strength 300 or more but less than 1000 (lots of adhesion amount) D: Signal strength 1000 or more (very much adhesion amount)

[0363] "Overall Evaluation" An overall evaluation was made based on the results of the bond rate measurement and the pickup characteristic test, according to the following evaluation criteria.

[0364] "Evaluation criteria for overall evaluation" A: The bond rate and pick-up characteristics are rated A. B: The bond rate and pick-up characteristics are rated A or B, with at least one of them being B. C: At least one of the bond rate and pick-up characteristics is rated C, and no D is given. D: At least one of the bond rate and pick-up characteristics is rated D.

[0365] As shown in Table 5, the magnetic recording media of Examples 1 to 20 were all rated "A" or "B" for bond ratio and pickup characteristics, and the overall rating was "A" or "B." This confirms that the magnetic recording media of Examples 1 to 20 have good pickup resistance and a highly adhesive lubricating layer.

[0366] In particular, Examples 2 and 7, which used compounds (1B) and (1G) in which b1 is 1 and a1 is 3 or 4 in formula (3-1), were given an overall rating of "A" and were good. ２and the distance between the amide bond site in formula (2-1) or formula (2-2) and the primary hydroxyl group in formula (3-1) is more appropriate, and the primary hydroxyl group can move more freely, so that the amide bond site and the primary hydroxyl group interact more strongly with the active site on the protective layer.

[0367] Furthermore, Example 4, which used a compound (1D) having two primary hydroxyl groups in formula (2-1), and Example 20, which used a compound (2J) having two primary hydroxyl groups in formula (2-2), were given an overall rating of "A," which was good. This is because the inclusion of two primary hydroxyl groups, which have strong bonding strength to the protective layer, resulted in better adhesion to the protective layer. Example 8, which used a compound (1H) in formula (4-2) where c7 is 3 or more, was given an overall rating of "A," which was good. This is presumably because the amide bond moiety contained in formula (2-2) adhered to the protective layer without being affected by the bulkiness of the perfluoropolyether chain.

[0368] In addition, Examples 9 and 10, which used compounds (1I) and (1J) having a secondary hydroxyl group, in which c3 in formula (4-1) is 2, were given an overall rating of "A" and were good. ２ This is presumably because the distance between the secondary hydroxyl group in the divalent linking group represented by the formula (2-1) and the amide bond moiety and primary hydroxyl group contained in formula (2-2) becomes more appropriate, and the interaction between the secondary hydroxyl group, the amide bond moiety, and the primary hydroxyl group and the protective layer is not inhibited.

[0369] In addition, Examples 11, 15 to 17, which used compounds (2A), (2E) to (2G) in which g or j in formula (5-1) is 1, were given an overall rating of "A" and were good. １ Or X in formula (2-2) ２ It is presumed that the ether bond contained in the compound (II) gives the compound an appropriate degree of flexibility, resulting in better adhesion to the protective layer.

[0370] In contrast, as shown in Table 6, Comparative Examples 1 to 5, which had lubricating layers formed using any of Compounds (3A) to (3E), were all rated "C" or "D" in bond ratio and pick-up properties, which were inferior to Examples 1 to 20. This is presumably because in Comparative Examples 1 to 5, the lubricating layers were formed using fluorine-containing ether compounds that do not satisfy Formula (1).

[0371] Specifically, in Comparative Examples 1 to 3, the lubricating layer was formed using compounds (3A) to (3C) that did not contain primary hydroxyl groups but had secondary hydroxyl groups and amide bond sites at both ends of the perfluoropolyether chain. Secondary hydroxyl groups have less mobility than primary hydroxyl groups. For this reason, it is presumed that in Comparative Examples 1 to 3, the adhesion strength due to the bond between the hydroxyl groups and the active sites on the protective layer was insufficient. Furthermore, in Comparative Examples 1 to 3, the amide bond sites were not adsorbed to the protective layer due to the attraction of the primary hydroxyl groups, which have a strong bond to the protective layer, and therefore it is presumed that the adhesion strength due to the bond between the amide bond sites and the active sites on the protective layer was also insufficient.

[0372] In addition, in Comparative Example 4, the lubricating layer is formed using compound (3D), which has an end group comprising an amide bond and a secondary hydroxyl group at one end of the perfluoropolyether chain.Compound (3D) does not contain a primary hydroxyl group, which has a strong bond strength to the protective layer, at the end of the side having the amide bond.Therefore, in compound (3D), the amide bond site is not attracted by the primary hydroxyl group and adsorbed to the protective layer, and the bulky aromatic ring arranged between the perfluoropolyether chain and the amide bond site inhibits the bond between the amide bond site and the active site on the protective layer, which is presumed to be the reason why the adhesion between the amide bond site and the active site on the protective layer is insufficient.As a result, in Comparative Example 4, the lubricating layer is likely to lift off the protective layer, resulting in poor bond rate and pick-up properties.

[0373] In addition, in comparative example 5, the compound (3E) that amide group and primary hydroxyl group are arranged at both ends of perfluoropolyether chain is used to form lubricating layer.But in compound (3E), perfluoropolyether chain and amide group are directly bonded without the intervention of linking group.Therefore, the mobility of amide group is insufficient, and the adsorption of amide bond site to the active point on protective layer is poor, so amide group and adjacent perfluoropolyether chain are easy to float from protective layer.Therefore, it is estimated that the lubricating layer formed by using compound (3E) has poor adhesion to protective layer, resulting in poor bond rate and pick-up property.

[0374] By using a lubricant for magnetic recording media containing the fluorine-containing ether compound of the present invention, it is possible to form a lubricating layer that has good adhesion to the protective layer and excellent pick-up resistance even if it is thin.

[0375] REFERENCE SIGNS LIST 10 magnetic recording medium 11 substrate 12 adhesive layer 13 soft magnetic layer 14 first underlayer 15 second underlayer 16 magnetic layer 17 protective layer 18 lubricating layer

Claims

1. A fluorine-containing ether compound characterized by being represented by the following formula (1). R １ -O-CH ２ -R ２ -CH ２ -O-R ３ (1) (In formula (1), R ２ is a perfluoropolyether chain. R １ is represented by formula (2-1) or formula (2-2). R ３ is an organic group having at least one polar group and having 2 to 65 carbon atoms. R １ and R ３ may be the same or different from each other.) (In formula (2-1), X １ is a divalent linking group having 1 to 40 carbon atoms which may contain at least one of a polar group and an ether oxygen atom. Y １ and Z １ are each independently an organic group having 1 to 12 carbon atoms which may contain at least one of a polar group and an ether oxygen atom, or a hydrogen atom. Y １ and Z １ may be bonded to each other to form a ring. At least one of X １ , Y １ , Z １ contains a primary hydroxyl group.) (In formula (2-2), X ２ is a divalent linking group having 1 to 40 carbon atoms which may contain at least one of a polar group and an ether oxygen atom. Y ２ is an organic group having 1 to 12 carbon atoms which may contain at least one of a polar group and an ether oxygen atom, or a hydrogen atom. Z ２ is an organic group having 1 to 12 carbon atoms which may contain at least one of a polar group and an ether oxygen atom. Y ２ and Z ２ may be bonded to each other to form a ring. At least one of X ２ , Y ２ , Z ２ contains a primary hydroxyl group.) 2. Y in the formula (2-1) １ and Z １ at least one of which contains a primary hydroxyl group, and Y in the formula (2-2) ２ and Z ２ The fluorine-containing ether compound according to claim 1, wherein at least one of which contains a primary hydroxyl group.

3. Y in the formula (2-1) １ and Z １ at least one of which is represented by the formula (3-1), and Y in the formula (2-2) ２ and Z ２ at least one of which is represented by the formula (3-1). The fluorine-containing ether compound according to claim 2. -[(CH ２ ) ａ１ -O] ｂ１ -H (3-1) (In the formula (3-1), a1 is an integer of 1 to 4. b1 is an integer of 1 to 3. When b1 is 2 or 3, each a1 may be the same or different.) 4. Y in the formula (2-1) １ and Z １ One of them is represented by the formula (3-1), and the other is selected from the group consisting of a group represented by the formula (3-1), an organic group having 1 to 12 carbon atoms containing no polar group, and a hydrogen atom. Y in the formula (2-2) ２ and Z ２ One of them is represented by the formula (3-1), and the other is selected from the group consisting of a group represented by the formula (3-1), an organic group having 1 to 12 carbon atoms containing no polar group, and a hydrogen atom (however, Z ２ will not be a hydrogen atom.), The fluorine-containing ether compound according to claim 3.

5. X in the formula (2-1) １ , and X in the formula (2-2) ２ are each independently a linking group selected from formula (4-1) or (4-2). The fluorine-containing ether compound according to claim 2. (In formula (4-1), c4 is an integer of 1 to 3, and c1 to c3 are each independently an integer of 1 to 4. When c4 is 2 or 3, each of c1 and c2 may be the same or different. * represents the site linked to the oxygen atom of -R ２ -CH ２ -O-. ** represents the site linked to the carbonyl carbon atom or nitrogen atom constituting the amide bond.) (In formula (4-2), c5 is an integer of 1 to 5, c6 is an integer of 0 to 3, and c7 is an integer of 1 to 5. When c6 is 2 or 3, each of c5 may be the same or different. * represents the site linked to the oxygen atom of -R ２ -CH ２ -O-. ** represents the site linked to the carbonyl carbon atom or nitrogen atom constituting the amide bond.) 6. X in the formula (2-1) １ , and X in the formula (2-2) ２ is a linking group containing at least one primary hydroxyl group, and the fluorine-containing ether compound according to claim 1.

7. X in the formula (2-1) １ , and X in the formula (2-2) ２ are linking groups containing at least one primary hydroxyl group, and Y １ , Z １ in the formula (2-1), and Y ２ , Z ２ in the formula (2-2) are each independently selected from the group consisting of an organic group having 1 to 12 carbon atoms that does not contain a polar group, and a hydrogen atom (however, Z ２ will not be a hydrogen atom.), The fluorine-containing ether compound according to claim 1.

8. X in the formula (2-1) １ , and X in the formula (2-2) ２ are each independently a linking group represented by the formula (5-1). The fluorine-containing ether compound according to claim 6. *-(CH ２ ) ｅ -[O-(CH ２ ) ｆ - ｇ -CHR ４ -[(CH ２ ) ｈ -O] ｊ -(CH ２ ) ｉ -** (5-1) (In the formula (5-1), e, f, h, and i are each independently an integer from 0 to 4. g and j are each independently an integer from 0 to 2. When g is 2, each f may be the same or different.) When g is 2, f in —(CH ２ ) ｆ — sandwiched between two oxygen atoms will not be 0. When e is 0, g is 0. When j is 2, each h may be the same or different. When j is 2, h in —(CH ２ ) ｈ — will not be 0. When i is 0, j is 0. R ４ is represented by formula (6-1). * represents the site linked to the oxygen atom of —R ２ —CH ２ —O—, and ** represents the site linked to the carbonyl carbon atom or nitrogen atom that constitutes the amide bond.) —[(CH ２ ) ｄ１ —O] ｄ２ —H (6-1) (In formula (6-1), d1 is an integer from 1 to 4. d2 is an integer from 1 to 3. When d2 is 2 or 3, each d1 may be the same or different.) 9. R in the formula (1) ３ The fluorine-containing ether compound according to claim 1, wherein is represented by the formula (2-1) or the formula (2-2).

10. R in the formula (1) １ and R ３ are the same, the fluorine-containing ether compound according to claim 9.

11. R in the formula (1) ３ is any group represented by the following formulas (7-1) to (7-3), the fluorine-containing ether compound according to claim 1. (In formula (7-1), y1 is 1 or 2, and y2 is an integer from 0 to 3. Q is an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, an alkynyl group, or a polar group. When y1 is 1, Q is a polar group. When Q is an aromatic hydrocarbon group or an unsaturated heterocyclic group, the atoms constituting the ring structure in Q are bonded to the methylene group adjacent to Q. When Q is an alkenyl group or an alkynyl group, the carbon atom constituting the unsaturated bond in Q is bonded to the methylene group adjacent to Q.) (In formula (7-2), y3 is an integer from 1 to 3, y4 is 0 or 1, and y5 is an integer from 0 to 3. Q is an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, an alkynyl group, or a polar group. When y4 is 0, Q is a polar group. When Q is an aromatic hydrocarbon group or an unsaturated heterocyclic group, the atoms constituting the ring structure in Q are bonded to the methylene group adjacent to Q. When Q is an alkenyl group or an alkynyl group, the carbon atom constituting the unsaturated bond in Q is bonded to the methylene group adjacent to Q.) (In formula (7-3), y6 is 0 or 1, y7 is an integer from 1 to 3, and y8 is an integer from 0 to 3. Q is an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, an alkynyl group, or a polar group. When y6 is 0, Q is a polar group. When Q is an aromatic hydrocarbon group or an unsaturated heterocyclic group, the atoms constituting the ring structure in Q are bonded to the methylene group adjacent to Q. When Q is an alkenyl group or an alkynyl group, the carbon atom constituting the unsaturated bond in Q is bonded to the methylene group adjacent to Q.) 12. R in the formula (1) ２ is a perfluoropolyether chain represented by the following formula (8), the fluorine-containing ether compound according to claim 1. —(CF ２ ) ｗ１ —O—(CF ２ O) ｗ２ —(CF ２ CF ２ O) ｗ３ —(CF ２ CF ２ CF ２ O) ｗ４ —(CF ２ CF ２ CF ２ CF ２ O) ｗ５ —(CF ２ ) ｗ６ — (8) (In the formula (8), w2, w3, w4, and w5 represent the average degree of polymerization and each independently represents 0 to 20. However, all of w2, w3, w4, and w5 do not become 0 at the same time. w1 and w6 are average values representing the number of CF ２ and each independently represents 1 to 3. The repeating units (CF ２ O), (CF ２ CF ２ O), (CF ２ CF ２ CF ２ O), (CF ２ CF ２ CF ２ CF ２ O) in the formula (8) have no particular limitation on the sequence order.) 13. R in the formula (1) ２ is any one selected from perfluoropolyether chains represented by the following formulas (8-1) to (8-4). The fluorine-containing ether compound according to claim 1. -CF ２ -(OCF ２ CF ２ ) ｗ７ -(OCF ２ ) ｗ８ -OCF ２ - (8-1) (In the formula (8-1), w7 and w8 represent the average degree of polymerization, w7 represents 1 to 20, and w8 represents 0 to 20.) -CF ２ CF ２ -(OCF ２ CF ２ CF ２ ) ｗ９ -OCF ２ CF ２ - (8-2) (In the formula (8-2), w9 represents the average degree of polymerization and represents 1 to 15.) -CF ２ CF ２ CF ２ -(OCF ２ CF ２ CF ２ CF ２ ) ｗ１０ -OCF ２ CF ２ CF ２ - (8-3) (In the formula (8-3), w10 represents the average degree of polymerization and represents 1 to 10.) -(CF ２ ) ｗ１１ -O-(CF ２ CF ２ CF ２ O) ｗ１２ -(CF ２ CF ２ O) ｗ１３ -(CF ２ ) ｗ１４ - (8-4) (In the formula (8-4), w12 and w13 represent the average degree of polymerization and each independently represents 1 to 20. w11 and w14 are average values representing the number of CF ２ and each independently represents 1 to 2.) 14. The fluorine-containing ether compound represented by the formula (1) is any of the compounds represented by the following formulas (1A) to (1J) and (2A) to (2J), and the fluorine-containing ether compound according to claim 1. (In formula (1A), p1A and q1A represent the average degree of polymerization, p1A represents 1 to 20, and q1A represents 0 to 20.) (In formula (1B), p1B and q1B represent the average degree of polymerization, p1B represents 1 to 20, and q1B represents 0 to 20.) (In formula (1C), p1C and q1C represent the average degree of polymerization, p1C represents 1 to 20, and q1C represents 0 to 20.) (In formula (1D), p1D and q1D represent the average degree of polymerization, p1D represents 1 to 20, and q1D represents 0 to 20.) (In formula (1E), p1E and q1E represent the average degree of polymerization, p1E represents 1 to 20, and q1E represents 0 to 20.) (In formula (1F), p1F and q1F represent the average degree of polymerization, p1F represents 1 to 20, and q1F represents 0 to 20.) (In formula (1G), r1G represents the average degree of polymerization and represents 1 to 15.) (In formula (1H), r1H represents the average degree of polymerization and represents 1 to 15.) (In formula (1I), r1I represents the average degree of polymerization and represents 1 to 15.) (In formula (1J), r1J represents the average degree of polymerization and represents 1 to 15.) (In formula (2A), p2A and q2A represent the average degree of polymerization, p2A represents 1 to 20, and q2A represents 0 to 20.) (In formula (2B), p2B and q2B represent the average degree of polymerization, p2B represents 1 to 20, and q2B represents 0 to 20.) (In formula (2C), p2C and q2C represent the average degree of polymerization, p2C represents 1 to 20, and q2C represents 0 to 20.) (In formula (2D), p2D and q2D represent the average degree of polymerization, p2D represents 1 to 20, and q2D represents 0 to 20.) (In formula (2E), p2E and q2E represent the average degree of polymerization, p2E represents 1 to 20, and q2E represents 0 to 20.) (In formula (2F), p2F and q2F represent the average degree of polymerization, p2F represents 1 to 20, and q2F represents 0 to 20.) (In formula (2G), r2G represents the average degree of polymerization and represents 1 to 15.) (In formula (2H), r2H represents the average degree of polymerization and represents 1 to 15.) (In formula (2I), r2I represents the average degree of polymerization and represents 1 to 15.) (In formula (2J), r2J represents the average degree of polymerization and represents 1 to 15.) 15. The fluorine-containing ether compound according to claim 1, wherein the number average molecular weight is in the range of 500 to 10,000.

16. A lubricant for a magnetic recording medium, comprising the fluorine-containing ether compound according to any one of claims 1 to 15.

17. A magnetic recording medium having at least a magnetic layer, a protective layer, and a lubricating layer sequentially provided on a substrate, wherein the lubricating layer contains the fluorine-containing ether compound according to any one of claims 1 to 15.

18. The magnetic recording medium according to claim 17, wherein the average film thickness of the lubricating layer is 0.5 nm to 2.0 nm.

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