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

Abstract

Disclosed is a fluorine-containing ether compound which is represented by the formula shown below. R1-O-CH2-R2-(CH2-R3-CH2-R2)n-CH2-O-R4 (In the formula, R1 is formula (2-1) or formula (2-2). R2 represents a perfluoropolyether chain. R4 represents an organic group that has at least one polar group and 1 to 50 carbon atoms. R3 represents a divalent linking group that has at least one hydroxyl group. n is an integer of 0 to 2.)

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. 2023-218399, filed December 25, 2023, the contents of which are incorporated herein by reference.

[0002] In order to improve the recording density of 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 with a thickness of approximately 0.5 to 3 nm. The lubricating layer improves the durability and protective power of the protective layer and prevents contaminants from penetrating into the magnetic recording medium.

[0004] Examples of lubricants used in forming the lubricating layer of a magnetic recording medium include -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 5).

[0005] Patent Document 1 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 linking groups is linked to an end group in which one or more hydrogen atoms of a chain organic group having 1 to 8 carbon atoms are substituted with a group having an amide bond. Patent Document 2 discloses a fluorine-containing ether compound in which one or both ends of the perfluoropolyether chain have an end group containing a group in which a carbonyl carbon atom or nitrogen atom of an amide bond is directly bonded to an aromatic hydrocarbon, and which has three or more hydroxyl groups.

[0006] Patent Document 3 discloses a method for synthesizing a fluoropolyalkyl ether amide used as a lubricant for magnetic recording media. Patent Document 3 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.

[0007] Patent Document 4 discloses a fluorine-containing ether compound having a skeleton in which a plurality of perfluoropolyether chains are bonded via a linking group having one polar group. Patent Document 4 also discloses a fluorine-containing ether compound in which a divalent linking group having at least one polar group and an end group are bonded in this order to both ends of the skeleton via methylene. Furthermore, Patent Document 4 discloses a fluorine-containing ether compound in which at least one end group is a group having an amide bond.

[0008] Patent Document 5 discloses a fluoropolyether compound containing three or more perfluoropolyether groups, the perfluoroether groups being linked by a linking group containing a hydrocarbon group having at least one hydroxyl group. Patent Document 5 also describes a fluoropolyether compound having terminal groups each having at least one hydroxyl group at both ends.

[0009] International Publication No. WO 2019 / 039265 (A) International Publication No. WO 2023 / 033044 (A) U.S. Patent No. 6,187,954 (B) International Publication No. WO 2023 / 033055 (A) International Publication No. WO 2018 / 147017 (A)

[0010] In magnetic recording and reproducing devices, there is a demand for further reduction in the flying height of the magnetic head. Therefore, there is a demand for further reduction in the thickness of the protective layer and / or lubricating layer in the magnetic recording medium. However, generally, when the thickness of the lubricating layer is reduced, the chemical resistance and wear resistance of the magnetic recording medium tend to decrease. Furthermore, when the flying height of the magnetic head is reduced, pickup may occur, in which the fluorine-containing ether compound in the lubricating layer adheres to the magnetic head.

[0011] 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 excellent chemical resistance and abrasion resistance and can suppress pickup, and that can be suitably used as a material for a lubricant for a magnetic recording medium. Another aim of the present invention is to provide a magnetic recording medium that has a lubricating layer containing the fluorine-containing ether compound of the present invention, has good chemical resistance, excellent abrasion resistance, and suppresses pickup.

[0012] 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 having end groups bonded via a methylene group and an ether oxygen atom to both ends of a perfluoropolyether chain, or to both ends of a skeleton in which two or three perfluoropolyether chains are bonded via a divalent linking group having a hydroxyl group, wherein the end groups contain an amide bond moiety (C(═O)N), and the amide bond moiety is a specific group bonded to the ether oxygen atom via a linking group containing no polar group and containing one or more carbon atoms, or an organic group having 1 to 50 carbon atoms and at least one polar group, and at least one end group is the above-mentioned specific group, and have conceived the present invention. That is, the present invention relates to the following matters.

[0013] [1] A fluorine-containing ether compound represented by the following formula (1): １ -O-CH ２ -R ２ - (CH ２ -R ３ -CH ２ -R ２ ) ｎ -CH ２ -OR- ４ (1) (In formula (1), R １ is expressed by the following formula (2-1) or formula (2-2): ２ is a perfluoropolyether chain. ４ is an organic group having 1 to 50 carbon atoms and at least one polar group. ３is a divalent linking group having at least one hydroxyl group. n is an integer of 0 to 2. When n is 1 or 2, multiple R ２ may be the same in part or in whole, or may be different from each other. ３ may be the same or different.)

[0014] (In formula (2-1), X １ is a divalent linking group having 1 to 12 carbon atoms that does not contain a polar group and may contain an ether oxygen atom. １ and Z １ are each independently an organic group having 1 to 30 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. ２ is a divalent linking group having 1 to 12 carbon atoms that does not contain a polar group and may contain an ether oxygen atom. ２ is an organic group having 1 to 30 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 30 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.)

[0015] [2] X in the formula (2-1) １ and X in the formula (2-2) ２ are each independently represented by the following formula (3):

[0016] In formula (3), p is an integer of 2 to 4, q is an integer of 0 to 2, and r is an integer of 1 to 4. When q is 2, the two p's may be the same or different. ２ -CH ２ The right end is the side that bonds to the oxygen atom of —O—, and the right end is the side that bonds to the carbonyl carbon atom or nitrogen atom that constitutes the amide bond.

[0017] [3] Y in the formula (2-1) １ and Z １ At least one of the above is a hydrogen atom, and Y ２ [3] The fluorine-containing ether compound according to [1] or [2], wherein

[0018] [4] R in the formula (1) ３ is a divalent linking group represented by the following formula (4):

[0019] (In formula (4), s is an integer of 1 to 3, and t is an integer of 1 to 3. The oxygen atom at the left end of formula (4) is R １ -CH on the side ２ -, and the oxygen atom at the right end is R ４ -CH on the side ２ - binds to.)

[0020] [5] R in the formula (1) ４ is not a group represented by the formula (2-1) or the formula (2-2), and R ４ [6] The fluorine-containing ether compound according to any one of [1] to [4], wherein at least one of the polar groups contained in R in formula (1) is a hydroxyl group. ４ [5] The fluorine-containing ether compound according to [5], wherein the compound (I) contains two or three polar groups, and at least one of the polar groups is a secondary hydroxyl group.

[0021] [7] R in the formula (1) ４ is any one of groups represented by the following formulas (5-1) to (5-3):

[0022] (In formula (5-1), a is an integer of 1 to 2, and b is an integer of 0 to 3. Q １ is an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, an alkynyl group, or a polar group. １ is a polar group. １ When Q is an aromatic hydrocarbon group or an unsaturated heterocyclic group, １The atoms constituting the ring structure in １ It bonds to the methylene group adjacent to Q. １ When Q is an alkenyl group or an alkynyl group, １ The carbon atoms that make up the unsaturated bond in Q １ In formula (5-2), c is an integer of 1 to 3, d is an integer of 0 to 1, and e is an integer of 0 to 3. ２ is an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, an alkynyl group, or a polar group. ２ is a polar group. ２ When Q is an aromatic hydrocarbon group or an unsaturated heterocyclic group, ２ The atoms constituting the ring structure in ２ It bonds to the methylene group adjacent to Q. ２ When Q is an alkenyl group or an alkynyl group, ２ The carbon atoms that make up the unsaturated bond in Q ２ In formula (5-3), f is an integer of 1 to 3, g is an integer of 0 or 1, and h is an integer of 0 to 3. ３ is an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, an alkynyl group, or a polar group. ３ is a polar group. ３ When Q is an aromatic hydrocarbon group or an unsaturated heterocyclic group, ３ The atoms constituting the ring structure in ３ It bonds to the methylene group adjacent to Q. ３ When Q is an alkenyl group or an alkynyl group, ３ The carbon atoms that make up the unsaturated bond in Q ３ It bonds to the methylene group adjacent to

[0023] [8] R in the formula (1) ４ [9] The fluorine-containing ether compound according to any one of [1] to [4], wherein R in formula (1) is represented by formula (2-1) or (2-2). １ and R ４ The fluorine-containing ether compound according to [8], wherein

[0024]

[10] R in the formula (1) ２ are each independently a perfluoropolyether chain represented by the following formula (6): -(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 - (6) (In formula (6), 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 (6) 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).

[0025]

[11] R in the formula (1) ２ is any one selected from perfluoropolyether chains represented by the following formulas (6-1) to (6-4): ２ -(OCF ２ CF ２ ) ｗ７ -(OCF ２ ) ｗ８ -OCF ２- (6-1) (In formula (6-1), 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 - (6-2) (In formula (6-2), 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 - (6-3) (In formula (6-3), 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 - (6-4) (In formula (6-4), 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

[0026]

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

[11] , wherein in formula (1), n ​​is 0.

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

[11] , wherein in formula (1), n ​​is 1.

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

[11] , wherein in formula (1), n ​​is 2.

[0027]

[15] The fluorinated ether compound according to claim 1, wherein the fluorinated ether compound represented by formula (1) is any of compounds represented by the following formulae (1A) to (1T) and (2A) to (2E): (Rf in formula (1A) １ In the formula (1B), i and j represent the average degree of polymerization, i represents 1 to 20, and j represents 0 to 20. １ In the formula (1C), i and j represent the average degree of polymerization, i represents 1 to 20, and j represents 0 to 20. １ In the formula (1D), i and j represent the average degree of polymerization, i represents 1 to 20, and j represents 0 to 20. １ In the formula (1E), i and j represent the average degree of polymerization, i represents 1 to 20, and j represents 0 to 20. ２ In the formula, k represents the average degree of polymerization and is a number ranging from 1 to 15. (Rf in formula (1F) ２ In the formula (1G), k represents the average degree of polymerization and represents 1 to 15. ２ In the formula (1H), k represents the average degree of polymerization and represents 1 to 15. ２ In the formula (1I), k represents the average degree of polymerization and represents 1 to 15. ２ In the formula (1J), k represents the average degree of polymerization and represents 1 to 15. ２ In the formula, k represents the average degree of polymerization and is a number ranging from 1 to 15. (Rf in formula (1K) １ In the formula (1L), i and j represent the average degree of polymerization, i represents 1 to 20, and j represents 0 to 20. １ In the formula (1M), i and j represent the average degree of polymerization, i represents 1 to 20, and j represents 0 to 20. １ In the formula (1N), i and j represent the average degree of polymerization, i represents 1 to 20, and j represents 0 to 20. １ In the formula (1O), i and j represent the average degree of polymerization, i represents 1 to 20, and j represents 0 to 20. ２ In the formula, k represents the average degree of polymerization and is a number ranging from 1 to 15. (Rf in formula (1P)２ In the formula (1Q), k represents the average degree of polymerization and represents 1 to 15. ２ In the formula (1R), k represents the average degree of polymerization and represents 1 to 15. ２ In the formula (1S), k represents the average degree of polymerization and represents 1 to 15. ２ In the formula (1T), k represents the average degree of polymerization and represents 1 to 15. ２ In the formula, k represents the average degree of polymerization and is a number ranging from 1 to 15. (Two Rf in formula (2A) １ In the formula, i and j represent the average degree of polymerization, i represents 1 to 20, and j represents 0 to 20. １ In the formula (2B), the average degrees of polymerization may be the same or different. １ In the formula, i and j represent the average degree of polymerization, i represents 1 to 20, and j represents 0 to 20. １ In the formula (2C), the average degrees of polymerization may be the same or different. ２ In the formula, k represents the average degree of polymerization and represents 1 to 15. ２ In the formula (2D), the average degrees of polymerization may be the same or different. １ In the formula, i and j represent the average degree of polymerization, i represents 1 to 20, and j represents 0 to 20. １ In the formula (2E), the average degrees of polymerization may be the same or different. ２ In the formula, k represents the average degree of polymerization and represents 1 to 15. ２ The average degrees of polymerization may be the same or different.

[0028]

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

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

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

[16] .

[18] 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

[16] .

[19] The magnetic recording medium according to

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

[0029] 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. Because the lubricant for a magnetic recording medium of the present invention contains the fluorine-containing ether compound of the present invention, it is possible to form a lubricating layer that has good chemical resistance, high wear resistance, and can suppress pickup, even when the thickness is reduced.

[0030] The magnetic recording medium of the present invention has a lubricating layer containing the fluorine-containing ether compound of the present invention.Therefore, the magnetic recording medium of the present invention has good chemical resistance, excellent wear resistance, and suppressed pick-up, and is excellent in reliability and durability.In addition, the lubricating layer of the magnetic recording medium of the present invention has good chemical resistance and wear resistance, and can suppress pick-up, so it can be made thinner and the flying height of the magnetic head can be reduced.

[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 conducted extensive research as described below. Conventionally, fluorine-containing ether compounds having polar groups such as hydroxyl groups have been preferably used as materials for lubricants for magnetic recording media (hereinafter sometimes abbreviated as "lubricants") applied to the surface of a protective layer. The polar groups contained in the fluorine-containing ether compounds bond with active sites on the protective layer, improving the adhesion of the lubricating layer to the protective layer. In conventional fluorine-containing ether compounds, polar groups are located at the ends of chain structures. Furthermore, when the fluorine-containing ether compound has multiple perfluoropolyether chains, polar groups are also located between adjacent perfluoropolyether chains.

[0033] However, when a thin lubricating layer is formed on a protective layer using a conventional lubricant, the adhesion of the lubricant to the protective layer is insufficient, making it difficult to achieve a lubricating layer that has good chemical resistance, excellent wear resistance, and a high pick-up suppression effect. More specifically, if the adhesion of the lubricant to the protective layer is insufficient, the lubricant applied to the protective layer becomes bulky. As a result, the coating state of the lubricating layer on the protective layer tends to become uneven. If the coating state of the lubricating layer is uneven, the chemical resistance and wear resistance of the lubricating layer will be insufficient.

[0034] Therefore, if the adhesion of the lubricant to the protective layer is insufficient, sufficient chemical resistance and wear resistance cannot be obtained unless the thickness of the lubricant layer is increased to make the lubricant layer uniform on the protective layer. However, if the thickness is increased to make the lubricant layer uniform, the lubricant is more likely to be picked up by the magnetic head, which may lead to a decrease in reliability and durability.

[0035] As a method for improving the adhesion of the lubricant to the protective layer, it is conceivable to use a fluorine-containing ether compound as the lubricant material, in which a plurality of polar groups are bonded to both ends of a chain structure containing a perfluoropolyether chain. However, in the lubricant layer formed using such a fluorine-containing ether compound, the adhesion to the protective layer is too strong, which can impair lubricity and result in insufficient wear resistance.

[0036] In addition, the fluorine-containing ether compound that has a large number of polar groups bonded has a high surface free energy of the whole molecule, so the lubricating layer formed by using it may be easily attached to chemical substances.Furthermore, if the polar groups in the fluorine-containing ether compound are too many, the polar groups that do not bond with the active site on the protective layer are easily generated, and the interaction between the polar groups within and / or between molecules is easily generated.As a result, it is estimated that if the number of polar groups contained in the fluorine-containing ether compound is too large, the effect of improving the adhesion of the lubricating layer to the protective layer due to the inclusion of polar groups is reduced.

[0037] Therefore, the present inventors have focused on the type and arrangement of polar group contained in fluorine-containing ether compound, and the bond between polar group and the active site on protective layer.Then, they have estimated that if the type and arrangement of polar group contained in lubricant is appropriate, the lubricating layer can be obtained, which has uniform coating state and excellent adhesion to protective layer, and have conducted extensive research to realize the fluorine-containing ether compound that can form the lubricating layer with good chemical resistance and abrasion resistance and high pick-up suppression effect.As a result, the present inventors have found that the fluorine-containing ether compound represented by formula (1) is sufficient.

[0038] In a lubricating layer containing a fluorine-containing ether compound represented by formula (1), for the reason <1> shown below, the adhesion to the protective layer is too strong and the wear resistance is not insufficient, for the reason <2> shown below, the surface free energy of the entire fluorine-containing ether compound molecule is not too high and chemical substances do not easily adhere, for the reasons <3> to <5> shown below, the polar groups in the fluorine-containing ether compound can each independently participate in bonding with active sites on the protective layer, and for the reason <6> shown below, the coating state with the protective layer is likely to be uniform. From these reasons, it is presumed that the fluorine-containing ether compound represented by formula (1) can form a lubricating layer that has good adhesion to the protective layer, good chemical substance resistance and wear resistance, and a high pick-up suppression effect.

[0039] <1> The amide bond moiety (C(═O)N) contained in the group represented by formula (2-1) or formula (2-2) contained in the fluorine-containing ether compound represented by formula (1) bonds with an active site on the protective layer, thereby improving the adhesion of the lubricating layer to the protective layer. The amide bond moiety contained in the group represented by formula (2-1) or formula (2-2) located at at least one end does not contain a polar group and is a divalent linking group (X in formula (2-1)) which may contain an ether oxygen atom. １ Or X in formula (2-2) ２ ) through -R ２ -CH ２ -O-(R ２ is bonded to the oxygen atom of the perfluoropolyether chain. ２ -CH ２ Unlike a fluorine-containing ether compound having a divalent linking group containing a polar group between the oxygen atom of -O- and the amide bond site, the terminal group portion does not have too strong adhesion to the protective layer. Therefore, a lubricating layer containing the fluorine-containing ether compound represented by formula (1) is prevented from having a decrease in wear resistance due to too strong adhesion to the protective layer.

[0040] <2> In the fluorine-containing ether compound represented by formula (1), X in formula (2-1) １ and X in formula (2-2) ２ does not contain a polar group, for example, -R ２ -CH ２ Compared with a fluorine-containing ether compound having a divalent linking group containing a polar group between the oxygen atom of -O- and the amide bond site, the surface free energy of the entire molecule is lower. Therefore, the fluorine-containing ether compound represented by formula (1) can prevent the lubricating layer containing this from being prone to adhesion of chemical substances due to the surface free energy of the entire compound being too high. Therefore, the fluorine-containing ether compound represented by formula (1) can suppress the decrease in the chemical resistance and pick-up resistance of the lubricating layer caused by the surface free energy of the entire compound being too high.

[0041] <3> -R ２ -CH ２The oxygen atom of —O— and the amide bond site (C(═O)N) contained in the group represented by formula (2-1) or formula (2-2) are connected by a divalent linking group having 1 to 12 carbon atoms (X in formula (2-1)) which does not contain a polar group and may contain an ether oxygen atom. １ Or X in formula (2-2) ２ ) is bonded to the group represented by formula (2-1) or formula (2-2) having an amide bond site that is difficult to freely rotate. This provides appropriate flexibility to the group represented by formula (2-1) or formula (2-2). Therefore, the fluorine-containing ether compound represented by formula (1) can be obtained by, for example, ２ The mobility (degree of freedom) of the amide bond moiety is higher than in a fluorine-containing ether compound in which the amide bond moiety contained in the group represented by formula (2-1) or (2-2) is directly bonded to a perfluoropolyether chain represented by formula (2-1). Therefore, in the fluorine-containing ether compound represented by formula (1), the amide bond moiety has good affinity for the active site on the protective layer, and is likely to bond to the active site on the protective layer.

[0042] <4> X in formula (2-1) １ and X in formula (2-2) ２ is a divalent linking group having 1 to 12 carbon atoms which does not contain a polar group and may contain an ether oxygen atom, and therefore, the amide bond site contained in the group represented by formula (2-1) or formula (2-2) is ２ Therefore, the amide bond moiety contained in the group represented by formula (2-1) or formula (2-2) has good affinity for the active sites on the protective layer and is likely to bond with the active sites on the protective layer.

[0043] <5> In the fluorine-containing ether compound represented by formula (1), the amide bond moiety contained in the group represented by formula (2-1) or formula (2-2) located at at least one terminal is unlikely to rotate freely. １ , Z １ Or Y in formula (2-2) ２ , Z ２ Even if a polar group is contained in Y in formula (2-1), １ , Z １Or Y in formula (2-2) ２ , Z ２ The polar group contained in formula (2-1) or formula (2-2) is unlikely to be inhibited from bonding to the active site on the protective layer by the amide bond site contained in the group represented by formula (2-1) or formula (2-2).

[0044] In addition, in the fluorine-containing ether compound represented by formula (1), R １ and R ４ Between ２ Therefore, a perfluoropolyether chain represented by R １ and R ４ The distance between R and R is appropriate. １ and a polar group contained in R ４ The polar groups contained in R do not inhibit the bonding with the active sites on the protective layer. １ and R ４ The polar group contained in the protective layer is unlikely to be inhibited from bonding with the active site on the protective layer.

[0045] In addition, in the fluorine-containing ether compound represented by formula (1), when n is 1 or 2, R ２ Between the multiple perfluoropolyether chains represented by ３ ) is placed. ３ and the hydroxyl group contained in R １ and R ４ Between ２ Therefore, a perfluoropolyether chain represented by R ３ The hydroxyl group contained in R １ and R ４ Therefore, the distance between R ３ The hydroxyl group contained in R １ and R ４ This makes it difficult for the bonding with the active points on the protective layer to be inhibited.

[0046] As explained above, the polar group contained in the fluorine-containing ether compound represented by formula (1) is not likely to inhibit the bonding of other polar groups with the active sites on the protective layer, and is not likely to be inhibited by other polar groups with the bonding of other polar groups with the active sites on the protective layer.Therefore, the polar groups contained in the fluorine-containing ether compound represented by formula (1) each independently exhibit good interaction with the protective layer, and can independently participate in the bonding of a large number of active sites present on the protective layer.As a result, in the lubricating layer comprising the fluorine-containing ether compound represented by formula (1), the polar groups that do not bond with the active sites on the protective layer are not likely to occur, and the number of polar groups that do not participate in the bonding with the active sites on the protective layer is reduced, and the interaction between polar groups within and / or between molecules can be suppressed.

[0047] <6> In the group represented by formula (2-1) or formula (2-2) contained in the fluorine-containing ether compound represented by formula (1), the bond of the carbon atom adjacent to the carbonyl carbon atom or nitrogen atom constituting the amide bond is difficult to rotate freely. Therefore, when the amide bond site contained in the group represented by formula (2-1) or formula (2-2) is bonded to an active site on the protective layer, the R ２ The perfluoropolyether chain represented by formula (2-1) is attracted to the protective layer side and is less likely to float up from the protective layer. Moreover, the group represented by formula (2-1) or formula (2-2) has an appropriate distance from other polar groups contained in the fluorine-containing ether compound. Therefore, the amide bond site contained in the group represented by formula (2-1) or formula (2-2) is less likely to aggregate with other polar groups contained in the fluorine-containing ether compound. For these reasons, the fluorine-containing ether compound represented by formula (1) can wet and spread on the protective layer in a uniform coating state, form strong bonds with the active sites on the protective layer, and form a lubricating layer that has excellent adhesion to the protective layer, good smoothness, and is uniformly coated on the protective layer.

[0048] Furthermore, the present inventors have confirmed that by using a lubricant containing the above-mentioned fluorine-containing ether compound to form a lubricating layer on the protective layer of a magnetic recording medium, it is possible to form a lubricating layer that has good chemical resistance and abrasion resistance and a high pick-up suppression effect, and have thus conceived the present invention.

[0049] 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-).

[0050] [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 -R ３ -CH ２ -R ２ ) ｎ -CH ２ -OR- ４ (1) (In formula (1), R １ is expressed by the following formula (2-1) or formula (2-2): ２ is a perfluoropolyether chain. ４ is an organic group having 1 to 50 carbon atoms and at least one polar group. ３ is a divalent linking group having at least one hydroxyl group. n is an integer of 0 to 2. When n is 1 or 2, multiple R ２ may be the same in part or in whole, or may be different from each other. ３ may be the same or different.)

[0051] (In formula (2-1), X １ is a divalent linking group having 1 to 12 carbon atoms that does not contain a polar group and may contain an ether oxygen atom. １ and Z １ are each independently an organic group having 1 to 30 carbon atoms which may contain at least one of a polar group and an ether oxygen atom, or a hydrogen atom. １ and Z １may be bonded to each other to form a ring. ２ is a divalent linking group having 1 to 12 carbon atoms that does not contain a polar group and may contain an ether oxygen atom. ２ is an organic group having 1 to 30 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 30 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.)

[0052] The fluorine-containing ether compound of the present embodiment represented by formula (1) is ２ -R ３ -CH ２ -R ２ ) is an integer of 0 to 2. Therefore, the fluorine-containing ether compound of this embodiment is ２ The compound has (n+1) perfluoropolyether chains represented by the following formula:

[0053] When the fluorine-containing ether compound of the present embodiment contains only one perfluoropolyether chain (hereinafter, sometimes referred to as "PFPE chain") (in other words, when n in formula (1) is 0), R ２ A methylene group and an ether oxygen atom are bonded to both ends of a PFPE chain represented by the formula (2-1) or (2-2), and a group represented by the formula (2-1) or (2-2) is bonded to at least one end of the chain.

[0054] When the fluorine-containing ether compound of the present embodiment contains a plurality of PFPE chains (in other words, when n in formula (1) is 1 or 2), R ２ Between the PFPE chains represented by ３ In this case, a methylene group and an ether oxygen atom are bonded to both sides of the skeleton, and a group represented by formula (2-1) or formula (2-2) is bonded to at least one end of the skeleton.

[0055] In the fluorine-containing ether compound of the present embodiment, n in formula (1) is an integer of 0 to 2. When n is 0, R ２ The PFPE chain represented by the formula (I) is the center, and a group having an amide bond is bonded to at least one end of the PFPE chain represented by the formula (I). Therefore, the fluorine-containing ether compound is easily wetted and spread evenly on the protective layer, and easily forms a lubricating layer having a uniform thickness, which is preferable. When n is 1 or 2, R ３ R linked by a divalent linking group represented by ２ A methylene group and an ether oxygen atom are arranged in this order at both ends of the PFPE chain represented by the formula: ３ Since the divalent linking group represented by the formula (I) has at least one hydroxyl group, the fluorine-containing ether compound has good adhesion to the active sites on the protective layer, and therefore is a fluorine-containing ether compound that easily wets and spreads uniformly on the protective layer, making it easy to obtain a lubricating layer having a uniform thickness, which is preferable.

[0056] (R ２ In the fluorine-containing ether compound represented by formula (1), (n+1) R ２ are each independently 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.

[0057] In the fluorine-containing ether compound represented by formula (1), (n+1) R ２ may be the same in part or in whole, or may be different from each other. ２ It is preferable that all n+1 R are the same. This is because the fluorine-containing ether compound is more uniformly coated on the protective layer, and a lubricating layer having better adhesion can be obtained. ２ Among them, two or more R ２are the same, (n+1) R ２ Among them, R ２ It means that two or more of the same R are included. ２ The term also includes those having the same repeating unit structure but different average degrees of polymerization.

[0058] 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.

[0059] (n+1) R in formula (1) ２ are each independently a PFPE chain derived from a polymer or copolymer of perfluoroalkylene oxide and represented by the following formula (6): -(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 - (6) (In formula (6), 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 (6) are (CF ２ O), (CF ２ CF ２ O), (CF ２ CF ２ CF２ O), (CF ２ CF ２ CF ２ CF ２ There are no particular restrictions on the arrangement order of O).

[0060] In formula (6), 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 (6), 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 (6). ２ O), (CF ２ CF ２ O), (CF ２ CF ２ CF ２ 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 (6). There is also no particular limitation on the number of types of repeating units in formula (6).

[0061] (n+1) R in formula (1) ２ are each independently any one selected from the PFPE chains represented by the following formulas (6-1) to (6-4): ２ are each independently one selected from the PFPE chains represented by formulas (6-1) to (6-4), a fluorine-containing ether compound can be obtained that provides a lubricating layer with good lubricity. ２are each independently any one selected from PFPE chains represented by formulas (6-1) to (6-4), 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 fluorinated ether compound with appropriate hardness. Therefore, the fluorinated ether compound applied to the protective layer is less likely to aggregate on the protective layer, allowing for the formation of an even thinner lubricating layer with sufficient coverage. Furthermore, the fluorinated ether compound has appropriate flexibility, allowing for the formation of a lubricating layer with better chemical resistance.

[0062] -CF ２ -(OCF ２ CF ２ ) ｗ７ -(OCF ２ ) ｗ８ -OCF ２ - (6-1) (In formula (6-1), 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 - (6-2) (In formula (6-2), 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 - (6-3) (In formula (6-3), 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- (6-4) (In formula (6-4), 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

[0063] In formula (6-1), the repeating unit (OCF ２ CF ２ ) and (OCF ２ In formula (6-1), 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 (6-1) 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.

[0064] In formulas (6-1) to (6-3), 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, resulting in a fluorine-containing ether compound that can provide a lubricating layer with good lubricity. Furthermore, in formulas (6-1) to (6-3), 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, resulting in a fluorine-containing ether compound that does not become too viscous, making it easy to apply a lubricant containing the fluorine-containing ether compound. Since w7, w8, w9, and w10, which indicate the average degree of polymerization, are easily wetted and spread on the protective layer, resulting in a fluorine-containing ether compound that can easily provide a lubricating layer with a uniform thickness, they are preferably 1 to 10, more preferably 1.5 to 8, and even more preferably 2 to 7.

[0065] In formula (6-4), the repeating unit (CF ２ CF ２ CF ２ O) and (CF ２ CF ２In formula (6-4), the order of the groups (CF) representing the average degree of polymerization is not particularly limited. ２ CF ２ CF ２ O) number w12 and (CF ２ CF ２ The number w13 of monomer units (CF) may be the same or different. ２ CF ２ CF ２ O) and (CF ２ CF ２ O) may be a random copolymer, a block copolymer, or an alternating copolymer.

[0066] In formula (6-4), 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 (6-4) 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 (6-4).

[0067] (R ３ In the fluorine-containing ether compound represented by formula (1), R ３ is a divalent linking group having at least one hydroxyl group. When n is 1 or 2, R ３ is the adjacent R ２ This allows the R ３ The fluorine-containing ether compound adheres closely to the protective layer, forming a thin lubricating layer with a sufficient coverage.

[0068] (CH ２ -R ３ -CH ２ -R ２ ) is 2, two R ３ may be the same or different. ３When the values ​​are 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.

[0069] In this specification, when n is 2, "two R ３ are the same" means that the three R ２ Among these, R located at the center of the fluorine-containing ether compound represented by formula (1) ２ For two R ３ This means that the atoms contained in the

[0070] R ３ The number of hydroxyl groups contained in the divalent linking group represented by R is preferably 1 to 3, and more preferably 1. ３ contains one or more hydroxyl groups, so R ３ A plurality of R connected via ２ The lubricating layer is unlikely to lift off the protective layer, and the adhesion between the lubricating layer and the protective layer is unlikely to decrease. ３ It is preferable that the number of hydroxyl groups contained in the protective layer is 3 or less, since this makes it more difficult for hydroxyl groups that are not involved in bonding with the active sites on the protective layer to be generated.

[0071] R ３ The divalent linking group represented by the formula (I) preferably has oxygen atoms located at both ends thereof. The oxygen atoms located at both ends of the linking group are preferably R ３ methylene groups (-CH ２ These two ether bonds impart appropriate flexibility to the fluorine-containing ether compound represented by formula (1), and R ３ This increases the affinity between the hydroxyl group of the divalent linking group represented by the formula (I) and the protective layer.

[0072] R ３The divalent linking group represented by the formula (I) is preferably a group in which a group in which a hydrogen atom bonded to at least one carbon atom of an alkylene group having 3 to 7 carbon atoms is substituted with a hydroxyl group is located between two oxygen atoms located at both ends. The alkylene group having 3 to 7 carbon atoms is preferably an alkylene group having 3 to 5 carbon atoms. The alkylene group having 3 to 7 carbon atoms preferably has a linear structure. R ３ is particularly preferably a group in which an oxygen atom is located at each end of a linear alkylene group having 3 to 7 carbon atoms and a hydroxyl group is bonded to a carbon atom located near the center of the linear alkylene group. This is because the fluorine-containing ether compound can be more uniformly coated on the protective layer, resulting in a lubricating layer with better adhesion.

[0073] R ３ Specifically, R is preferably represented by the following formula (4): ３ However, when it is the formula (4), the fluorine-containing ether compound represented by the formula (1) can be easily synthesized, which is preferable.

[0074] (In formula (4), s is an integer of 1 to 3, and t is an integer of 1 to 3. The oxygen atom at the left end of formula (4) is R １ -CH on the side ２ -, and the oxygen atom at the right end is R ４ -CH on the side ２ - binds to.)

[0075] In formula (4), s is an integer of 1 to 3, preferably an integer of 1 or 2, and more preferably 1. This is because the coating state of the fluorine-containing ether compound on the protective layer becomes more uniform, resulting in a lubricating layer with better adhesion. In formula (4), t is an integer of 1 to 3, preferably an integer of 1 or 2, and more preferably 1. This is because the coating state of the fluorine-containing ether compound on the protective layer becomes more uniform, resulting in a lubricating layer with better adhesion.

[0076] In formula (4), when s and / or t are integers of 2 or more, the distance between the hydroxyl group and the PFPE chain in formula (4) becomes longer than when s and t are 1. ３ R for the hydroxyl group ２ The influence of the bulkiness of the PFPE chains represented by the formula (1) is reduced, and a lubricating layer with high adhesion to the protective layer can be formed.

[0077] (R １ In formula (1), R １ is a group having an amide bond and is represented by formula (2-1) or (2-2). In the fluorine-containing ether compound of this embodiment, R １ The amide bond moiety contained in the terminal group represented by R exhibits 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.

[0078] <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 12 carbon atoms that does not contain a polar group and may contain an ether oxygen atom. １ and X ２ is a divalent linking group having one or more carbon atoms, so R ２ and the amide bond site (C(═O)N) contained in formula (2-1) and formula (2-2) are not too close. Therefore, the amide bond site contained in formula (2-1) or formula (2-2) can adhere to the protective layer without being affected by the bulkiness of the PFPE chain.

[0079] Also, X １ and X ２ is a divalent linking group having 12 or less carbon atoms, and therefore R ２The distance between the PFPE chain represented by and the amide bond moiety contained in formula (2-1) and formula (2-2) is not too long. Therefore, the PFPE chain can be effectively prevented from floating up from the protective layer due to the interaction between the amide bond moiety contained in formula (2-1) and formula (2-2) and the protective layer. ２ Since the distance between the PFPE chain and the polymer chain is more appropriate, X １ and X ２ The divalent linking group represented by the formula (I) preferably contains 1 to 10 carbon atoms, and more preferably 1 to 6 carbon atoms.

[0080] X in formula (2-1) １ and X in formula (2-2) ２ X preferably has a chain structure and preferably does not contain a ring structure. １ and X ２ However, when the compound has a chain structure, it is less likely to inhibit the interaction between the amide bond moiety contained in formula (2-1) and formula (2-2) and the protective layer.

[0081] X in formula (2-1) １ and X in formula (2-2) ２ does not contain a polar group. Therefore, as explained in the above <1>, the fluorine-containing ether compound represented by formula (1) does not contain a polar group, for example, X １ or X ２ Unlike when X contains a polar group, the group represented by formula (2-1) or (2-2) does not have too strong adhesion to the protective layer. Therefore, it is possible to suppress a decrease in abrasion resistance due to too strong adhesion to the protective layer. In addition, as explained in <2> above, １ or X ２ Since the compound does not contain a polar group, it is possible to prevent the surface free energy of the entire compound from being too high, which would otherwise cause the lubricating layer containing the compound to have a reduced resistance to chemical substances and a reduced pick-up resistance.

[0082] X in formula (2-1) １ and X in formula (2-2) ２The divalent linking group represented by the formula (2-1) may contain one or more ether oxygen atoms (—O—). When the divalent linking group contains an ether oxygen atom, the formula (2-1) or (2-2) has 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.

[0083] X in formula (2-1) １ and X in formula (2-2) ２ When the divalent linking group represented by the formula (I) has a plurality of ether oxygen atoms, adjacent ether oxygen atoms are preferably bonded to each other via a linking group having two or more carbon atoms linked together, because the distance between adjacent ether oxygen atoms becomes appropriate, resulting in a fluorine-containing ether compound that is less likely to aggregate.

[0084] X in formula (2-1) １ and X in formula (2-2) ２ are preferably each independently a divalent linking group represented by the following formula (3):

[0085] (The left end of formula (3) is -R ２ -CH ２ The right end is the side that bonds to the oxygen atom of —O—, and the right end is the side that bonds to the carbonyl carbon atom or nitrogen atom that constitutes the amide bond.

[0086] X １ and X ２ When the divalent linking group represented by formula (3) is a group represented by formula (3), R ２ and the amide bond moiety contained in formula (2-1) or formula (2-2) is neither too close nor too far, and is therefore appropriate, allowing the amide bond moiety to strongly interact with the active site on the protective layer.

[0087] In formula (3), q is an integer of 0 to 2. When q is 2, each of [-(CH ２ )ｐ In formula (3), when q is 1 or 2, X in formula (2-1) may be the same or different. １ and X in formula (2-2) ２ Since X contains an ether bond, the fluorine-containing ether compound has appropriate flexibility, which is preferable. １ or X ２ The number of ether oxygen atoms contained in X is not too large. １ or X ２ is a linking group represented by formula (3), 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.

[0088] In formula (3), p is an integer of 2 to 4. When p is 2 or more and q is 1 or 2, the adjacent R ２ and the amide bond contained in formula (2-1) or formula (2-2) becomes more appropriate. ２ -CH ２ Two or more methylene groups are arranged between the oxygen atom of -O- and the ether oxygen atom in formula (3), and between the ether oxygen atoms in formula (3). This results in a fluorine-containing ether compound that is less likely to aggregate. Furthermore, when p is 4 or less, even if q is 1 or 2, the linking group represented by formula (3) is not too long, and adjacent R ２ and the amide bond contained in formula (2-1) or formula (2-2) has an appropriate distance. In formula (3), p is preferably 2 or 3. When p is 2 or 3, the molecular weight of formula (2-1) or formula (2-2) is large, and the proportion of fluorine atoms in the fluorine-containing ether compound molecule is reduced, making it possible to prevent the surface free energy of the entire molecule from becoming too large.

[0089] In formula (3), r is an integer of 1 to 4. When r is an integer of 1 to 4, the adjacent R ２and the amide bond contained in formula (2-1) or formula (2-2) has an appropriate distance. Moreover, when r in formula (3) is an integer of 1 to 4, the molecular weight of formula (2-1) or formula (2-2) is large, so that the proportion of fluorine atoms in the fluorine-containing ether compound molecule decreases, and the surface free energy of the entire molecule can be prevented from becoming too large. r is preferably 1 to 3, and more preferably 1 or 2.

[0090] In formula (3), when q is 0, r is preferably 1 or 2. In this case, X in formula (2-1) １ and X in formula (2-2) ２ Since the number of methylene groups contained in X is too large, １ and X ２ Even if the divalent linking group does not contain an ether oxygen atom, the flexibility of the divalent linking group portion is not lost, and a decrease in the affinity of the amide bond site to the protective layer can be suppressed.

[0091] <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 30 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 30 carbon atoms which may contain at least one of a polar group and an ether oxygen atom.

[0092] Y in formula (2-1) １ , Z １ , and Y in formula (2-2) ２ , Z ２ When the organic group is an organic group, it may contain one or more polar groups. Examples of the polar group 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 Examples include a hydroxyl group (-H) and a cyano group (-CN). When the organic group contains a hydroxyl group as a polar group, the hydroxyl group may be a primary hydroxyl group, a secondary hydroxyl group, or a tertiary hydroxyl group. When the organic group contains a polar group, the number of polar groups is preferably 1 or 2, and more preferably 1, because polar groups that are not involved in bonding with active sites present on the protective layer are less likely to be generated.

[0093] Y １ , Y 2 , Z １ , Z ２ When Y is the organic group, it may contain one or more ether oxygen atoms. １ , Z １ , Y ２ , Z ２ The organic group represented by the formula (I) has appropriate flexibility, and the amide bond moiety 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.

[0094] Y in formula (2-1) １ and Z １ , and Y in formula (2-2) ２ and Z ２ is preferably an organic group having 1 to 15 carbon atoms that does not contain 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.

[0095] Y in formula (2-1) １and 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 one or more 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 - may be a ring having a structure in which a plurality of methylene groups, each of which may have a polar group bonded thereto, are linked together. １ and Z １ , Y ２ and 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.

[0096] 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. １ and Z １ It is preferable that at least one of Y is a hydrogen atom. １ and Z １ and Y are both organic groups having 1 to 30 carbon atoms, the fluorine-containing ether compound containing the formula (2-1) has excellent affinity for the protective layer at the amide bond site. ２ is preferably a hydrogen atom. ２ is an organic group having 1 to 30 carbon atoms, the fluorine-containing ether compound containing formula (2-2) has excellent affinity of the amide bond site to the protective layer.

[0097] Examples of the structure of formula (2-1) include, but are not limited to, the following formulas (2-1-A) to (2-1-I).

[0098]

[0099] Examples of the structure of formula (2-2) include, but are not limited to, the following formulae (2-2-A) to (2-2-I).

[0100]

[0101] (R ４ In the fluorine-containing ether compound represented by formula (1), R ４ The terminal group represented by R is an organic group having 1 to 50 carbon atoms and at least one polar group. ４ is preferably an organic group having 1 to 30 carbon atoms, more preferably an organic group having 2 to 20 carbon atoms. When the number of carbon atoms is within the above range, the ratio of the number of carbon atoms to the number of polar groups becomes appropriate, resulting in a fluorinated ether compound with appropriate molecular polarity.

[0102] R ４ 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 Examples of the alkyl group include a cyano group (-H) and a cyano group (-CN).

[0103] R ４ 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), the carbon atom contained in the polar group is ４ The number of carbon atoms in the terminal group indicated by is included in the number of carbon atoms.

[0104] R ４The number of polar groups in the terminal group represented by is preferably 1 to 3, more preferably 2 or 3, and most preferably 2, so that the fluorine-containing ether compound can form a lubricating layer with better adhesion to the protective layer. 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, the fluorine-containing ether compound can be prevented from agglomerating due to too many polar groups contained in the fluorine-containing ether compound, resulting in a decrease in smoothness. Furthermore, if the number of polar groups is 3 or less, a decrease in wear resistance due to too strong adhesion to the protective layer can be suppressed.

[0105] R ４ 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 ４ The plurality of polar groups of R are all oriented so as to be able to adhere to the protective layer. ４ 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.

[0106] R ４ 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. ４ 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.

[0107] 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.

[0108] 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.

[0109] 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.

[0110] R ４ 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.

[0111] 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 amide bond site contained therein and R １ has a hydroxyl group, and R ３ The hydroxyl group contained in R ４ has a hydroxyl group (collectively referred to as "amide bond site and hydroxyl group"), and R ４ 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.

[0112] Specifically, the amide bond site and the hydroxyl group in formula (1) exhibit adsorption ability by interacting with the hydrogen atom and the carbonyl group at the locally charged site on the protective layer. ４ 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.

[0113] Therefore, the amide bond site and the hydroxyl group in formula (1) and R ４ 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. ４ The lubricating layer containing the fluorine-containing ether compound having a carbon-carbon unsaturated bond moiety in the terminal group represented by the formula (I) has even better adhesion to the protective layer and higher pick-up resistance.

[0114] R ４ may be a terminal group represented by the formula (2-1) or (2-2). ４ contains an amide bond moiety as a polar group. In this case, R １ and R ４ Both of R １ and R ４ The amide bond sites contained in each of R can form strong interactions with the protective layer. ４ When R is a terminal group represented by formula (2-1) or formula (2-2), a preferred example of the structure is １ This is the same as that explained for the terminal group represented by

[0115] R ４ is a terminal group represented by the formula (2-1) or (2-2), R １ and R ４ and may be the same or different, and are preferably the same. １ and R ４ 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 ４If the values ​​are the same, the product can be easily produced with fewer steps, which is preferable.

[0116] R ４ is not a terminal group represented by formula (2-1) or formula (2-2), a lubricating layer having excellent adhesion to the protective layer can be formed. ４ At least one of the polar groups contained in R is preferably a hydroxyl group. ４ is not a terminal group represented by formula (2-1) or formula (2-2), R ４ The terminal group represented by R preferably contains two or three polar groups, at least one of which is a secondary hydroxyl group. A lubricating layer having excellent adhesion to the protective layer can be formed, and all of the properties of chemical resistance, abrasion resistance, and pick-up resistance are such that R ４ is a terminal group represented by formula (2-1) or formula (2-2), it is easy to obtain a lubricating layer having a property equal to or better than that obtained when

[0117] R ４ When the terminal group represented by formula (2-1) or formula (2-2) is not an terminal group represented by formula (2-1) or formula (2-2), it is preferably an terminal group represented by any of formulas (5-1) to (5-3) below, because this allows the formation of a lubricating layer that has good chemical resistance and abrasion resistance and excellent pick-up resistance.

[0118] (In formula (5-1), a is an integer of 1 to 2, and b is an integer of 0 to 3. Q １ is an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, an alkynyl group, or a polar group. １ is a polar group. １ When Q is an aromatic hydrocarbon group or an unsaturated heterocyclic group, １ The atoms constituting the ring structure in １ It bonds to the methylene group adjacent to Q. １ When Q is an alkenyl group or an alkynyl group, １ The carbon atoms that make up the unsaturated bond in Q １ In formula (5-2), c is an integer of 1 to 3, d is an integer of 0 to 1, and e is an integer of 0 to 3.２ is an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, an alkynyl group, or a polar group. ２ is a polar group. ２ When Q is an aromatic hydrocarbon group or an unsaturated heterocyclic group, ２ The atoms constituting the ring structure in ２ It bonds to the methylene group adjacent to Q. ２ When Q is an alkenyl group or an alkynyl group, ２ The carbon atoms that make up the unsaturated bond in Q ２ In formula (5-3), f is an integer of 1 to 3, g is an integer of 0 or 1, and h is an integer of 0 to 3. ３ is an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, an alkynyl group, or a polar group. ３ is a polar group. ３ When Q is an aromatic hydrocarbon group or an unsaturated heterocyclic group, ３ The atoms constituting the ring structure in ３ It bonds to the methylene group adjacent to Q. ３ When Q is an alkenyl group or an alkynyl group, ３ The carbon atoms that make up the unsaturated bond in Q ３ It bonds to the methylene group adjacent to

[0119] In formulas (5-1) to (5-3), Q １ ~Q ３ is an aromatic hydrocarbon group, Q １ ~Q ３ The atoms constituting the ring structure in １ ~Q ３ It bonds to the methylene group adjacent to Q. １ ~Q ３ is an aromatic hydrocarbon group, Q １ ~Q ３ In formulas (5-1) to (5-3), the aromatic hydrocarbon groups exemplified above can be used as Q. １ ~Q ３ When is an unsaturated heterocyclic group, Q １ ~Q ３The atoms constituting the ring structure in １ ~Q ３ It bonds to the methylene group adjacent to Q. １ ~Q ３ When is an unsaturated heterocyclic group, Q １ ~Q ３ As the unsaturated heterocyclic group, the unsaturated heterocyclic groups exemplified above can be used.

[0120] In formulas (5-1) to (5-3), Q １ ~Q ３ When Q is an alkenyl group, １ ~Q ３ The carbon atoms that make up the unsaturated bond in Q １ ~Q ３ It bonds to the methylene group adjacent to Q. １ ~Q ３ When Q is an alkenyl group, １ ~Q ３ Examples of the group include -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 (5-1) to (5-3) is preferably a hydrocarbon group having 1 to 3 carbon atoms. １ ~Q ３ When Q is an alkenyl group, １ ~Q ３ -CH=CH ２ It is preferred that the formula is -CH=CH ２ has an appropriate bulkiness. １ ~Q ３ -CH=CH ２A 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.

[0121] In formulas (5-1) to (5-3), Q １ ~Q ３ When Q is an alkynyl group, １ ~Q ３ The carbon atoms that make up the unsaturated bond in Q １ ~Q ３ It bonds to the methylene group adjacent to Q. １ ~Q ３ When Q is an alkynyl group, １ ~Q ３ Examples of the group include -C≡CH and -C≡CR. １７ (R １７ is an organic group. １７ The organic group represented by the formula (5-1) to (5-3) is preferably a hydrocarbon group having 1 to 3 carbon atoms. １ ~Q ３ When Q is an alkynyl group, it becomes a terminal group with appropriate bulkiness. １ ~Q ３ It is preferred that is —C≡CH.

[0122] In formulas (5-1) to (5-3), Q １ ~Q ３ When Q is a polar group, １ ~Q ３ The polar groups exemplified above can be used as Q. １ ~Q ３ is preferably a hydroxyl group or a cyano group. １ ~Q ３ When Q is a hydroxyl group 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. １ ~Q ３ is a polar group, the lubricating layer containing the fluorine-containing ether compound has even better adhesion to the protective layer and can be made thinner, which is preferable. The reasons for this are explained below.

[0123] In formulas (5-1) to (5-3), the secondary hydroxyl group and Q １ ~Q ３ is bonded via a divalent organic group which may contain an ether bond. １ ~Q ３ Even if Q is a polar group, the secondary hydroxyl group and Q in formulas (5-1) to (5-3) １ ~Q ３ As a result, the distance between the secondary hydroxyl group and the polar group represented by formula (5-1) to (5-3) is appropriate. １ ~Q ３ The polar group represented by the formula (5-1) to (5-3) is unlikely to be inhibited from bonding with the active site on the protective layer by other polar groups. １ ~Q ３ It is difficult to aggregate with polar groups represented by the formula:

[0124] Therefore, the secondary hydroxyl groups and Q １ ~Q ３ The polar groups represented by the formulas (5-1) to (5-3) can be independently adsorbed to the active sites on the protective layer. １ ~Q ３ A lubricating layer containing a fluorine-containing ether compound having a terminal group which is a polar group has even better adhesion to the protective layer and excellent pick-up resistance.

[0125] Among the above, Q in formulas (5-1) to (5-3) １ ~Q ３ represents a hydroxyl group, 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.

[0126] In the terminal group represented by formula (5-1), a is 1 or 2, and b is an integer of 0 to 3. When a is 1, Q １ is a polar group, and formula (5-1) has two polar groups. In this case, since formula (5-1) has two polar groups, a lubricating layer with good adhesion to the protective layer can be formed. When a is 2, Q １may be any of an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, an alkynyl group, and a polar group. １ When Q is an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, or an alkynyl group, the formula (5-1) also has two polar groups. Therefore, a lubricating layer having good adhesion to the protective layer can be formed. １ is an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, or an alkynyl group, so that Q １ The π-π interaction between the carbon-carbon unsaturated bond site and the protective layer allows the formation of a lubricating layer with excellent adhesion and pick-up resistance. １ is a polar group, the formula (5-1) has three polar groups, which makes it possible to form a lubricating layer that exhibits superior adhesion to the protective layer.

[0127] In the terminal group represented by formula (5-1), b is an integer of 0 to 3. In the terminal group represented by formula (5-1), Q in formula (5-1) １ Even if Q is a polar group, １ Since the distance between Q and the secondary hydroxyl group in formula (5-1) is not too close, the polar group in formula (5-1) is unlikely to aggregate. １ When Q is a polar group, １ In the terminal group represented by formula (5-1), b is 3 or less, so that the distance between Q and the secondary hydroxyl group in formula (5-1) is more appropriate. １ The mobility of the terminal group does not become too high, and each polar group of the terminal group can adhere sufficiently to the protective layer.

[0128] In the terminal group represented by formula (5-2), c is an integer of 1 to 3. When d is 0, Q ２ is a polar group. Since c is an integer of 1 or more, when d is 0, Q ２ The distance between the secondary hydroxyl group and the compound in formula (5-2) is appropriate, and Q ２is a polar group, the polar group in formula (5-2) is unlikely to aggregate. Furthermore, since c is an integer of 1 or greater, when d is 1, the secondary hydroxyl groups in formula (5-2) are not too close to each other, and the secondary hydroxyl groups in formula (5-2) are unlikely to aggregate. In the terminal group represented by formula (5-2), c is 3 or less, and the mobility of the terminal group represented by formula (5-2) is not too high, allowing each polar group in the terminal group to adhere sufficiently to the protective layer. It is preferable that c is 2 or less.

[0129] In the terminal group represented by formula (5-2), d is 0 or 1. When d is 0, Q ２ is a polar group, and formula (5-2) has two polar groups. In this case, since formula (5-2) has two polar groups, a lubricating layer with good adhesion to the protective layer can be formed. When d is 1, Q ２ may be any of an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, an alkynyl group, and a polar group. ２ When Q is an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, or an alkynyl group, the formula (5-2) also has two polar groups. Therefore, a lubricating layer with good adhesion to the protective layer can be formed. ２ is an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, or an alkynyl group, so that Q ２ The π-π interaction between the carbon-carbon unsaturated bond moiety and the protective layer allows the formation of a lubricating layer with excellent adhesion and pick-up resistance. ２ is a polar group, the formula (5-2) has three polar groups. This makes it possible to form a lubricating layer that exhibits excellent adhesion to the protective layer.

[0130] In the terminal group represented by formula (5-2), e is an integer of 0 to 3. In the terminal group represented by formula (5-2), Q in formula (5-2) ２ Even if Q is a polar group, ２ Since the distance between Q and the secondary hydroxyl group in formula (5-2) is not too close, the polar group in formula (5-2) is unlikely to aggregate. ２ When Q is a polar group,２ In order to make the distance between the secondary hydroxyl group in formula (5-2) and the hydroxyl group in formula (5-3) more appropriate, it is preferable that e is 1 or more. In addition, when d is 0, even if e is 0, the polar group Q ２ When d is 0 and e is 1 or more, the distance between the polar group Q and the secondary hydroxyl group in formula (5-2) is appropriate. ２ In the terminal group represented by formula (5-2), e is 3 or less, so that Q in formula (5-2) is more suitable. ２ The mobility of the terminal groups is not too high, and each polar group of the terminal groups can adhere sufficiently to the protective layer.

[0131] In the terminal group represented by formula (5-3), g is 0 or 1. When g is 0, Q ３ is a polar group, and formula (5-3) has two polar groups. In this case, since formula (5-3) has two polar groups, a lubricating layer with good adhesion to the protective layer can be formed. When g is 1, Q ３ may be any of an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, an alkynyl group, and a polar group. ３ When Q is an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, or an alkynyl group, the formula (5-3) also has two polar groups. This allows the formation of a lubricating layer with good adhesion to the protective layer. ３ is an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, or an alkynyl group, so that Q ３ The π-π interaction between the carbon-carbon unsaturated bond moiety and the protective layer allows the formation of a lubricating layer with excellent adhesion and pick-up resistance. ３ When is a polar group, the formula (5-3) has three polar groups. Therefore, a lubricating layer that exhibits excellent adhesion to the protective layer can be formed.

[0132] In the terminal group represented by formula (5-3), f is an integer of 1 to 3. Since f is 1 or more, when g is 1, the distance between the secondary hydroxyl groups in formula (5-3) does not become too close. Therefore, the secondary hydroxyl groups in formula (5-3) are less likely to aggregate. In the terminal group represented by formula (5-3), f is 3 or less, so the mobility of the terminal group represented by formula (5-3) 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 f is 2 or less.

[0133] In the terminal group represented by formula (5-3), h is an integer of 0 to 3. Therefore, Q ３ and the carbon atom to which Q is bonded ３ The carbon atoms to which the secondary hydroxyl groups are bonded adjacent to Q are bonded directly or via a chain linking group of 1 to 3 atoms. ３ and Q ３ The distance between the adjacent secondary hydroxyl group and Q becomes appropriate. ３ The terminal group represented by formula (5-3) has h of 3 or less, so that Q in formula (5-3) ３ The mobility of the terminal group does not become too high, and each polar group of the terminal group can adhere sufficiently to the protective layer.

[0134] In the fluorine-containing ether compound represented by formula (1), n ​​is 0 and R １ and R ４ and are preferably the same because this results in a fluorine-containing ether compound that is easy to synthesize. In the fluorine-containing ether compound represented by formula (1), n ​​is 1 and R １ and R ４ are the same, and the two R ２ In the fluorine-containing ether compound represented by formula (1), n ​​is 2 and R １ and R ４ are the same, and the two R ３ are the same, and the three R ２are preferably the same, since this results in a fluorine-containing ether compound that is easy to synthesize.

[0135] Specifically, the fluorine-containing ether compound represented by formula (1) is preferably any of the compounds represented by the following formulas (1A) to (1T) and (2A) to (2E): When the compound represented by formula (1) is any of the compounds represented by the following formulas (1A) to (1T) and (2A) to (2E), the raw materials are easily available, and a lubricating layer can be formed which has excellent adhesion even when thin, has good chemical resistance and wear resistance, and is even more excellent in pick-up resistance.

[0136] The compounds represented by the following formulas (2A) to (2E) are all R ２ In the compounds represented by the following formulae (1A) to (1T) and (2A) to (2E), the Rf １ , Rf ２ That is, in the compounds represented by the following formulae (1A) to (1D), (1K) to (1N), (2A), (2B) and (2D), Rf １ is a perfluoropolyether chain represented by the above formula (6-1). In the compounds represented by the following formulas (1E) to (1J), (1O) to (1T), (2C) and (2E), Rf ２ is the perfluoropolyether chain represented by the above formula (6-2). Rf １ i and j, Rf ２ Since k in the above formula is a value indicating the average degree of polymerization, it is not necessarily an integer.

[0137]

[0138] (Rf in formula (1A) １ In the formula (1B), i and j represent the average degree of polymerization, i represents 1 to 20, and j represents 0 to 20. １In the formula (1C), i and j represent the average degree of polymerization, i represents 1 to 20, and j represents 0 to 20. １ In the formula (1D), i and j represent the average degree of polymerization, i represents 1 to 20, and j represents 0 to 20. １ In the formula (1E), i and j represent the average degree of polymerization, i represents 1 to 20, and j represents 0 to 20. ２ In the formula, k represents the average degree of polymerization and is a number ranging from 1 to 15.

[0139] (Rf in formula (1F) ２ In the formula (1G), k represents the average degree of polymerization and represents 1 to 15. ２ In the formula (1H), k represents the average degree of polymerization and represents 1 to 15. ２ In the formula (1I), k represents the average degree of polymerization and represents 1 to 15. ２ In the formula (1J), k represents the average degree of polymerization and represents 1 to 15. ２ In the formula, k represents the average degree of polymerization and is a number ranging from 1 to 15.

[0140] (Rf in formula (1K) １ In the formula (1L), i and j represent the average degree of polymerization, i represents 1 to 20, and j represents 0 to 20. １ In the formula (1M), i and j represent the average degree of polymerization, i represents 1 to 20, and j represents 0 to 20. １ In the formula (1N), i and j represent the average degree of polymerization, i represents 1 to 20, and j represents 0 to 20. １ In the formula (1O), i and j represent the average degree of polymerization, i represents 1 to 20, and j represents 0 to 20. ２ In the formula, k represents the average degree of polymerization and is a number ranging from 1 to 15.

[0141] (Rf in formula (1P) ２ In the formula (1Q), k represents the average degree of polymerization and represents 1 to 15. ２ In the formula (1R), k represents the average degree of polymerization and represents 1 to 15. ２In the formula (1S), k represents the average degree of polymerization and represents 1 to 15. ２ In the formula (1T), k represents the average degree of polymerization and represents 1 to 15. ２ In the formula, k represents the average degree of polymerization and is a number ranging from 1 to 15.

[0142] (Two Rf in formula (2A) １ In the formula, i and j represent the average degree of polymerization, i represents 1 to 20, and j represents 0 to 20. １ In the formula (2B), the average degrees of polymerization may be the same or different. １ In the formula, i and j represent the average degree of polymerization, i represents 1 to 20, and j represents 0 to 20. １ In the formula (2C), the average degrees of polymerization may be the same or different. ２ In the formula, k represents the average degree of polymerization and represents 1 to 15. ２ In the formula (2D), the average degrees of polymerization may be the same or different. １ In the formula, i and j represent the average degree of polymerization, i represents 1 to 20, and j represents 0 to 20. １ In the formula (2E), the average degrees of polymerization may be the same or different. ２ In the formula, k represents the average degree of polymerization and represents 1 to 15. ２ The average degrees of polymerization may be the same or different.

[0143] 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.

[0144] 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. １９ The 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.

[0145] 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.

[0146] "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.

[0147] <First Production Method> In formula (1), n ​​is 0 and R １ and R ４ When a compound in which

[0148] (In formula (7), R ２ is R in formula (1) ２ Hal represents a (pseudo)halogen group. R represents a group corresponding to formula (2-1) or formula (2-2).

[0149] R in formula (1) ２ At both ends of the perfluoropolyether chain corresponding to ２ A fluorine-based compound having hydroxymethyl groups at both ends is prepared. A (pseudo) alkyl halide compound having an amide bond site, including a group corresponding to formula (2-1) or formula (2-2), is reacted with the hydroxymethyl groups at both ends of the fluorine-based compound. The reaction ratio of the fluorine-based compound having hydroxymethyl groups at both ends to the (pseudo) alkyl halide compound is preferably about 1:2 (molar ratio). This allows the reaction of a compound in which n in formula (1) is 0 and R １ and R ４ It is possible to produce a fluorine-containing ether compound in which

[0150] The (pseudo) alkyl halide compound having an amide bond moiety used in the first production method contains a group corresponding to formula (2-1) or formula (2-2), and examples thereof include compounds represented by the following formulae (2-1-a) to (2-1-i) and (2-2-a) to (2-2-i). The compounds represented by formulae (2-1-a) to (2-1-i) and (2-2-a) to (2-2-i) can be produced by known methods, and commercially available products may also be used. The -NH- and -NH- groups forming an amide bond contained in the compounds represented by formulae (2-1-a) to (2-1-i) and (2-2-a) to (2-2-i) ２ The —OH group may be protected with an appropriate protecting group before use in the reaction.

[0151] (In formulas (2-1-a) to (2-1-i), Hal represents a (pseudo)halogen group.)

[0152] (In formulas (2-2-a) to (2-2-i), Hal represents a (pseudo)halogen group.)

[0153] <Second Production Method> In the formula (1), n ​​is 0 and R １ and R ４ When a compound different from the above is produced, the production method shown in the following formula (8) can be used.

[0154] (In formula (8), R ２ is R in formula (1) ２ Hal represents a (pseudo)halogen group. R represents a group corresponding to formula (2-1) or formula (2-2). B represents R ４ represents a partial structure of a terminal group represented by

[0155] (First Reaction) R in Formula (1) ２ At both ends of the perfluoropolyether chain corresponding to ２A fluorine-based compound having a hydroxymethyl group at one end of the fluorine-based compound is prepared. A (pseudo) alkyl halide compound having an amide bond site is reacted with the hydroxymethyl group at one end of the fluorine-based compound. The reaction ratio between the fluorine-based compound having hydroxymethyl groups at both ends and the (pseudo) alkyl halide compound is preferably about 1:1 (molar ratio). This allows the formation of R ２ At one end of the PFPE chain corresponding to R １ A first intermediate compound is prepared having an attached organic group having an amide bond site corresponding to:

[0156] The (pseudo) alkyl halide compound having an amide bond moiety used in the second production method may be the same as that used in the first production method.

[0157] (Second Reaction) Next, the hydroxymethyl group (—CH ２ OH), R in formula (1) ４ The first intermediate compound is reacted with an epoxy compound having a partial structure of R ４ The reaction ratio of the epoxy compound having the partial structure of formula (1) is preferably about 1:1 (molar ratio). １ and R ４ It is possible to produce a fluorine-containing ether compound different from R ４ The epoxy compound having the partial structure of the formula (I) can be produced by the method described below.

[0158] In this embodiment, in the first reaction, one end of the perfluoropolyether chain is reacted with a (pseudo) alkyl halide compound having an amide bond site, and in the second reaction, the other end of the perfluoropolyether chain is reacted with a compound represented by R ４ In the first reaction, an epoxy compound having a partial structure of R ４ and then in the second reaction, reacting with a (pseudo) alkyl halide compound having an amide bond site.

[0159] R １ and R ４Unlike R ４ is a group represented by formula (2-1) or formula (2-2), in the second reaction, R ４ Instead of the epoxy compound having the partial structure of ４ Alternatively, a (pseudo) alkyl halide compound having an amide bond site corresponding to:

[0160] <Third Production Method> In formula (1), n ​​is 1 and R １ and R ４ are the same, and two R ２ When a compound having the same formula (9) is produced, the production method shown in the following formula (9) can be used.

[0161] (In formula (9), R ２ is R in formula (1) ２ Hal represents a (pseudo)halogen group. R represents a group corresponding to formula (2-1) or formula (2-2).

[0162] (First Reaction) In the first reaction of the third production method, R ２ At one end of the PFPE chain corresponding to １ A first intermediate compound is prepared having an attached organic group having an amide bond site corresponding to:

[0163] (Second Reaction) Next, the hydroxymethyl group (—CH ２ OH), in formula (1), R ３ The reaction ratio of the first intermediate compound to the epoxy compound is preferably about 2:1 (molar ratio). This allows the reaction of the first intermediate compound with the epoxy compound in a state where n in formula (1) is 1 and R １ and R ４ are the same, and two R ２ It is possible to produce a fluorine-containing ether compound having the same

[0164] In formula (1), R ３Examples of epoxy compounds having a group having a partial structure of a linking group represented by the formula (4-A) and a (pseudo)halogen group (hereinafter, these may be referred to as (pseudo)halogenated epoxy compounds) include compounds represented by the following formulas (4-A) to (4-C).

[0165] (In formulas (4-A) to (4-C), Hal represents a (pseudo)halogen group.)

[0166] <Fourth Production Method> In formula (1), n ​​is 1 and R １ and R ４ are different from each other, or two R ２ When a compound in which are different from each other is produced, a production method shown in the following formula (10) can be used.

[0167] (In formula (10), R ２ is R in formula (1) ２ is the same as two R ２ may be the same or different. Hal represents a (pseudo)halogen group. R represents a group corresponding to formula (2-1) or formula (2-2). B represents R ４ represents a partial structure of a terminal group represented by

[0168] (First Reaction) In the first reaction of the fourth production method, R １ Side R ２ At both ends of the perfluoropolyether chain corresponding to ２ OH) is prepared, and reacted with a fluorine-based compound having R １ Side R ２ At one end of the PFPE chain corresponding to １ A first intermediate compound is prepared having an attached organic group having an amide bond site corresponding to:

[0169] (Second Reaction) Next, the hydroxymethyl group (—CH ２ The reaction ratio of the first intermediate compound to the (pseudo)halogenated epoxy compound is preferably about 1:1 (molar ratio).１ Side R ２ At one end of the PFPE chain corresponding to １ and an organic group having an amide bond site corresponding to R ３ A second intermediate compound having an epoxy group bonded thereto and having a partial structure of a linking group represented by the following formula is produced.

[0170] The (pseudo)halogenated epoxy compound used in the fourth production method may be the same as that used in the third production method.

[0171] (Third Reaction) R in formula (1) ４ Side R ２ At both ends of the perfluoropolyether chain corresponding to ２ A fluorine-based compound having R in formula (1) is prepared. ４ The epoxy compound having the partial structure of R is reacted with a fluorine-based compound having hydroxymethyl groups at both ends. ４ The reaction ratio with the epoxy compound having the partial structure of R is preferably about 1:1 (molar ratio). ４ Side R ２ At one end of the PFPE chain corresponding to R ４ A third intermediate compound having an attached organic group corresponding to:

[0172] R used in the fourth manufacturing method ４ As the epoxy compound having the partial structure of R, the same compounds as those used in the second production method can be used. １ and R ４ Unlike R ４ is a group represented by formula (2-1) or formula (2-2), in the third reaction, R ４ Instead of the epoxy compound having the partial structure of ４ Alternatively, a (pseudo) alkyl halide compound having an amide bond site corresponding to:

[0173] (Fourth Reaction) Finally, the second intermediate compound obtained by the second reaction is reacted with the third intermediate compound obtained by the third reaction. The reaction ratio of the second intermediate compound to the third intermediate compound is preferably about 1:1 (molar ratio). This allows the reaction of the compound represented by formula (1) where n is 1 and R １ and R ４ are different from each other, or two R ２ It is possible to produce fluorine-containing ether compounds in which the fluorine-containing ether compounds have different valences.

[0174] In the fourth production method, the third reaction was carried out after the second reaction, but the first and second reactions may be carried out after the third reaction. Also, in the fourth production method, the second intermediate compound was obtained by reacting the first intermediate compound with a (pseudo)halogenated epoxy compound, but the compound obtained by reacting the third intermediate compound with a (pseudo)halogenated epoxy compound may be reacted with the first intermediate compound.

[0175] <Fifth Production Method> In the formula (1), n ​​is 2 and R ２ The three perfluoropolyether chains represented by the formula (I) are the same, and the two linking groups R ３ are the same, and the terminal group R １ and R ４ and R are the same, or n in formula (1) is 2 and R ２ Of the three perfluoropolyether chains represented by ２ The only difference is that the two linking groups R ３ are the same, and the terminal group R １ and R ４ When a compound in which

[0176] (First Reaction) R at the center of the molecule in formula (1) ２ At both ends of the perfluoropolyether chain corresponding to ２A fluorine-based compound having a hydroxymethyl group (OH) at both ends of the fluorine-based compound is prepared. Then, the hydroxyl groups of the hydroxymethyl groups at both ends of the fluorine-based compound are reacted with a (pseudo)halogenated epoxy compound. The reaction ratio of the fluorine-based compound to the (pseudo)halogenated epoxy compound is preferably about 1:2 (molar ratio). This allows the R at the center of the molecule in formula (1) to be reacted with the hydroxymethyl group at both ends of the fluorine-based compound. ２ At both ends of the perfluoropolyether chain corresponding to ３ A first intermediate compound having an epoxy group having a partial structure of a linking group represented by the following formula is prepared.

[0177] The (pseudo)halogenated epoxy compound used in the fifth production method may be the same as that used in the third production method.

[0178] (Second Reaction) In the second reaction of the fifth production method, R １ side (=R ４ side) R ２ At both ends of the perfluoropolyether chain corresponding to ２ OH) is prepared, and reacted with a fluorine-based compound having R １ side (=R ４ side) R ２ At one end of the PFPE chain corresponding to １ (=R ４ A second intermediate compound is prepared having an attached organic group having an amide bond site corresponding to the compound (III).

[0179] (Third Reaction) Finally, the first intermediate compound obtained by the first reaction is reacted with the second intermediate compound obtained by the second reaction. The reaction ratio of the first intermediate compound to the second intermediate compound is preferably about 1:2 (molar ratio). This allows the reaction of the compound represented by formula (1) when n is 2 and R ２ The three perfluoropolyether chains represented by the formula (I) are the same, and the two linking groups R ３ are the same, and the terminal group R １ and R ４ or a compound in which n in formula (1) is 2 and R ２ Of the three perfluoropolyether chains represented by２ The only difference is that the two linking groups R ３ are the same, and the terminal group R １ and R ４ It is possible to produce a fluorine-containing ether compound in which

[0180] In the fifth production method, the second reaction is carried out after the first reaction, but the first reaction may be carried out after the second reaction.

[0181] <Sixth Production Method> In the formula (1), n ​​is 2 and two linking groups R ３ are the same, and the terminal group R １ and R ４ , R among the three perfluoropolyether chains １ Side R ２ and R ４ Side R ２ (R not located in the center of the molecule ２ When a compound in which one or more of the above is different is produced, the production method shown below can be used.

[0182] (First Reaction) In the first reaction of the sixth production method, the R at the center of the molecule in formula (1) is converted to a methyl group in the same manner as in the first reaction of the fifth production method. ２ At both ends of the perfluoropolyether chain corresponding to ３ A first intermediate compound having an epoxy group having a partial structure of a linking group represented by the following formula is prepared.

[0183] (Second Reaction) R in formula (1) １ Side R ２ At both ends of the perfluoropolyether chain corresponding to ２ A fluorine-based compound having a hydroxymethyl group at one end of the fluorine-based compound is prepared. A (pseudo) alkyl halide compound having an amide bond site is reacted with the hydroxymethyl group at one end of the fluorine-based compound. The reaction ratio between the fluorine-based compound having hydroxymethyl groups at both ends and the (pseudo) alkyl halide compound is preferably about 1:1 (molar ratio). This allows the formation of R １ Side R ２ At one end of the PFPE chain corresponding to R １ A second intermediate compound is prepared having an attached organic group having an amide bond site corresponding to:

[0184] The (pseudo) alkyl halide compound having an amide bond moiety used in the sixth production method may be the same as that used in the first production method.

[0185] (Third Reaction) In the third reaction of the sixth production method, R ４ Side R ２ At one end of the PFPE chain corresponding to R ４ A third intermediate compound having an attached organic group corresponding to:

[0186] (Fourth Reaction) The first intermediate compound obtained by the first reaction is reacted with the second intermediate compound obtained by the second reaction. The reaction ratio of the first intermediate compound to the second intermediate compound is preferably about 1:1 (molar ratio). １ Side R ２ and R at the center of the molecule in formula (1). ２ and the linking group R ３ and R １ Side R ２ R at the end of １ and at the other end is an organic group having an amide bond site corresponding to R ３ A fourth intermediate compound having an epoxy group having a partial structure of a linking group represented by the following formula is prepared.

[0187] (Fifth Reaction) The fourth intermediate compound obtained by the fourth reaction is reacted with the third intermediate compound obtained by the third reaction. The reaction ratio of the fourth intermediate compound to the third intermediate compound is preferably about 1:1 (molar ratio). This allows n in formula (1) to be 2 and two linking groups R ３ are the same, and the terminal group R １ and R ４ , R among the three perfluoropolyether chains １ Side R ２ and R ４ Side R ２ (R not located in the center of the molecule ２ ) can be produced.

[0188] In the sixth production method, the first to third reactions were carried out in this order, but the order may be reversed. Furthermore, although the fourth intermediate compound was produced by reacting the first intermediate compound with the second intermediate compound, the fluorine-containing ether compound may be produced by reacting the first intermediate compound with the third intermediate compound to obtain an intermediate compound, with the second intermediate compound.

[0189] The (pseudo)halogen group (X) contained in the compounds used in the above-described first to sixth production methods 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.

[0190] R contained in the compounds and intermediate compounds used in the first to sixth production methods １ and / or R ４ The amide bond site and / or polar group forming the partial structure of may be protected by an appropriate protecting group. The protecting group contained in the above-mentioned compound and intermediate compound can be deprotected at an appropriate stage.

[0191] (R ４ A method for producing an epoxy compound having a partial structure of R in formula (1) ４ The epoxy compound having the partial structure of can be produced, for example, by using any of the following (Method 1) to (Method 3). (Method 1) As shown in the following formula (11), ４ The copolymer can be produced by reacting an alcohol (B'-OH) having a terminal group partial structure represented by the following formula with a halogen compound having an epoxy group.

[0192] (In formula (11), B' is R in formula (1) ４The partial structure of the terminal group represented by

[0193] (Method 2) As shown in the following formula (12), ４ The compound can be produced by subjecting an alcohol (B'-OH) having a terminal group partial structure represented by the formula: to an addition reaction with allyl glycidyl ether. Thereafter, the unsaturated bond site contained in the compound obtained by the addition reaction is oxidized by the action of m-chloroperbenzoic acid (mCPBA).

[0194] (In formula (12), B' is R in formula (1) ４ mCPBA represents m-chloroperbenzoic acid.

[0195] (Method 3) As shown in the following formula (13), ４ The alcohol (B'-OH) having a terminal group partial structure represented by the formula (I) is reacted with a halogen compound having an alkenyl group. Then, the unsaturated bond site in the resulting compound is oxidized by the action of m-chloroperbenzoic acid (mCPBA).

[0196] (In formula (13), B' is R in formula (1) ４ mCPBA represents m-chloroperbenzoic acid.

[0197] R ４ As the epoxy compound having the partial structure of the formula (I), a commercially available product may be purchased and used.

[0198] [Lubricant for magnetic recording media] The lubricant for magnetic recording media of this embodiment contains a fluorine-containing ether compound represented by the above 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 the above formula (1) are not impaired.

[0199] 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.

[0200] 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.

[0201] The lubricant of this embodiment contains a fluorine-containing ether compound represented by formula (1), 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 chemical resistance and wear resistance of the magnetic recording medium and has an excellent pickup suppression effect, even when the thickness is small.

[0202] [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.

[0203] 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.

[0204] "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.

[0205] "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.

[0206] "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).

[0207] 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.

[0208] "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.

[0209] "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.

[0210] "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.

[0211] 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 O３ , 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 -TiO ２ etc. can be suitably used.

[0212] The first magnetic layer may contain one or more elements selected from B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb, Ru, and Re, in addition to Co, Cr, Pt, and oxides. The second magnetic layer may be made of the same material as the first magnetic layer. The second magnetic layer preferably has a granular structure.

[0213] The third magnetic layer preferably has a non-granular structure made of a material containing Co, Cr, and Pt and not containing oxides, and may contain one or more elements selected from B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb, Ru, Re, and Mn in addition to Co, Cr, and Pt.

[0214] 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.

[0215] 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).

[0216] 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.

[0217] 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.

[0218] "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.

[0219] 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).

[0220] 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.

[0221] The thickness of the protective layer 17 is preferably 1 nm to 7 nm. If the thickness of the protective layer 17 is 1 nm or more, sufficient performance as the protective layer 17 can be obtained. If the thickness of the protective layer 17 is 7 nm or less, it is preferable from the viewpoint of thinning the protective layer 17. Methods that can be used to form the protective layer 17 include sputtering using a target material containing carbon, CVD (chemical vapor deposition) using a hydrocarbon raw material such as ethylene or toluene, and IBD (ion beam deposition).

[0222] When a carbon-based protective layer is formed as the protective layer 17, it can be deposited by, for example, DC magnetron sputtering. In particular, when a carbon-based protective layer is formed as the protective layer 17, it is preferable to deposit an amorphous carbon protective layer by plasma CVD. The amorphous carbon protective layer deposited by plasma CVD has a uniform surface with little roughness.

[0223] "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.

[0224] 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.

[0225] 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.

[0226] 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.

[0227] 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.

[0228] "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.

[0229] 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).

[0230] 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.

[0231] 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.

[0232] 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 can cover the surface of the protective layer 17 with a high coverage, even if it is thin, and has excellent adhesion to the protective layer, good chemical resistance and wear resistance, and excellent pickup resistance. Therefore, the magnetic recording medium 10 of this embodiment can stably float a magnetic head and has good long-term reliability and durability.

[0233] 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.

[0234] [Example 1] The compound represented by the above formula (1A) was obtained by the following method. (First reaction) HOCH ２ CF ２ O (CF ２ CF ２ O) i (CF ２ O) j CF ２ CH ２5.0 g of a compound (number average molecular weight: 997, molecular weight distribution: 1.1) represented by OH (where i, representing the average degree of polymerization, is 4.5, and j, representing the average degree of polymerization, is 4.5), 1.4 g of 2-bromoacetamide (molecular weight: 137, 10.5 mmol), and 7.3 mL of N,N-dimethylacetamide (DMF) were charged and stirred at room temperature to form a mixed solution. 4.1 g of cesium carbonate (molecular weight: 325, 12.5 mmol) was added to this mixed solution, and the mixture was reacted at 70°C for 8 hours with stirring.

[0235] The reaction product obtained after the reaction was cooled to 0°C, and 50 mL of an aqueous ammonium chloride solution was added to stop the reaction. The reaction solution obtained was transferred to a separatory funnel and extracted three times with 100 mL of ethyl acetate. The organic layer was washed with brine and 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 (1A) (Rf in formula (1A) １ In this example, i, which indicates the average degree of polymerization, is 4.5, and j, which indicates the average degree of polymerization, is 4.5. 4.5 g of a polymer (number average molecular weight 1109) was obtained.

[0236] 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] = 3.70 to 4.45 (8H), 6.00 to 7.50 (4H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -55.6 to -51.5 (9F), -77.5 (2F), -80.5 (2F), -91.2 to -88.4 (18F)

[0237] [Example 2] The same procedure as in Example 1 was carried out, except that 1.9 g of 2-bromo-N-propylacetamide (molecular weight 180, 10.5 mmol) was used instead of 2-bromoacetamide, to obtain compound (1B) (Rf １ In this example, i, which indicates the average degree of polymerization, is 4.5, and j, which indicates the average degree of polymerization, is 4.5. 4.6 g of a polymer (number average molecular weight 1195) was obtained.

[0238] 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 1.20 (6H), 1.50 to 1.80 (4H), 3.00 to 3.45 (4H), 3.70 to 4.45 (8H), 6.00 to 7.50 (2H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -55.6 to -51.5 (9F), -77.5 (2F), -80.5 (2F), -91.2 to -88.4 (18F)

[0239] [Example 3] In the above-mentioned Example 1, HOCH ２ CF ２ O (CF ２ CF ２ O) i (CF ２ O) j CF ２ CH ２ OH (where i, which indicates the average degree of polymerization, is 4.5, and j, which indicates the average degree of polymerization, is 4.5) instead of a compound (number average molecular weight: 997, molecular weight distribution: 1.1) represented by ２ CF ２ O (CF ２ CF ２ O) i (CF ２ O) j CF ２ CH ２ The same procedure as in Example 1 was carried out to obtain compound (1C) (Rf in formula (1C)), except that 5.0 g of a compound (number average molecular weight: 1001, molecular weight distribution: 1.1) represented by the formula OH (where i representing the average degree of polymerization is 7.1, and j representing the average degree of polymerization is 0) was used, and 1.6 g of 3-bromo-propionamide (molecular weight: 152, 10.5 mmol) was used instead of 2-bromoacetamide. １ In this formula, i representing the average degree of polymerization is 7.1, and j representing the average degree of polymerization is 0. 4.6 g of a polymer having a number average molecular weight of 1,143 was obtained.

[0240] The obtained compound (1C) １ H-NMR and１９ 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 2.40 (4H), 3.55 to 4.45 (8H), 6.00 to 7.50 (4H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -78.6 (2F), -81.3 (2F), -91.0 to -88.1 (28.4F)

[0241] [Example 4] The same procedure as in Example 3 was carried out, except that 1.9 g of 2-(2-bromoethoxy)acetamide (molecular weight 182, 10.5 mmol) was used instead of 3-bromo-propionamide, to obtain compound (1D) (Rf １ In this formula, i representing the average degree of polymerization is 7.1, and j representing the average degree of polymerization is 0. 4.7 g of a polymer having a number average molecular weight of 1203 was obtained.

[0242] 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] = 3.45 to 4.60 (16H), 6.00 to 7.50 (4H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -78.6 (2F), -81.3 (2F), -91.0 to -88.1 (28.4F)

[0243] [Example 5] In the above-mentioned Example 1, HOCH ２ CF ２ O (CF ２ CF ２ O) i (CF ２ O) j CF ２ CH ２ OH (where i, which indicates the average degree of polymerization, is 4.5, and j, which indicates the average degree of polymerization, is 4.5) instead of a compound (number average molecular weight: 997, molecular weight distribution: 1.1) represented by ２ CF ２ CF ２O (CF ２ CF ２ CF ２ O) ｋ CF ２ CF ２ CH ２ The same procedure as in Example 1 was carried out, except that 5.0 g of a compound (number average molecular weight: 1008, molecular weight distribution: 1.1) represented by the formula (OH) (where k representing the average degree of polymerization is 4.4) was used, and 3.0 g of an amide compound (molecular weight: 287, 10.5 mmol) represented by the following formula (14) was used instead of 2-bromoacetamide, to obtain compound (1E) (Rf ２ In this case, k, which indicates the average degree of polymerization, is 4.4. 4.8 g of a polymer (number average molecular weight 1238) was obtained.

[0244] The amide compound represented by formula (14) was synthesized by reacting 3-hydroxypropionamide with ethylene glycol ditosylate.

[0245] (In formula (14), Ts represents a p-toluenesulfonyl group.)

[0246] 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] = 1.90 to 2.40 (4H), 3.45 to 4.65 (16H), 6.00 to 7.50 (4H) 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)

[0247] [Example 6] The compound represented by the above formula (1F) was obtained by the following method. (First Reaction) In a nitrogen gas atmosphere, HOCH ２ CF ２ CF ２ O (CF ２ CF ２ CF ２ O) ｋ CF２ CF ２ CH ２ 5.0 g of a compound (number average molecular weight: 1008, molecular weight distribution: 1.1) represented by the formula OH (where k, the average degree of polymerization, is 4.4), 0.6 g of 2-bromoacetamide (molecular weight: 137, 5.0 mmol), and 7.3 mL of N,N-dimethylacetamide (DMF) were charged and stirred at room temperature to form a mixed solution. 2.0 g of cesium carbonate (molecular weight: 325, 6.2 mmol) was added to this mixed solution, and the mixture was reacted at 70°C for 8 hours with stirring.

[0248] The reaction product obtained after the reaction was cooled to 0°C, and 50 mL of an aqueous ammonium chloride solution was added to terminate the reaction. The resulting reaction solution was transferred to a separatory funnel and extracted three times with 100 mL of ethyl acetate. The organic layer was washed with brine and 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 4.2 g of a compound represented by the following formula (15) as intermediate compound (1F-1).

[0249] (In formula (15), Rf ２ is represented by the above formula, and Rf ２ The average degree of polymerization k in the formula is 4.4.

[0250] (Second Reaction) Under a nitrogen gas atmosphere, 4.2 g (number average molecular weight 1065) of the compound represented by formula (15) which is intermediate compound (1F-1), 0.6 g (molecular weight 158, 4.0 mmol) of compound (Ep-1) represented by the following formula (16), and 5.8 mL of t-butanol were charged into a 100 mL recovery flask and stirred at room temperature until the mixture became homogeneous. 0.13 g (molecular weight 112, 1.2 mmol) of potassium tert-butoxide was further added to this homogeneous solution, and the mixture was reacted at 70°C for 16 hours with stirring.

[0251] (In formula (16), THP represents a tetrahydropyranyl group.)

[0252] After the reaction, the reaction solution obtained was returned to room temperature, and 20 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 with anhydrous sodium sulfate. After filtering off the desiccant, the filtrate was concentrated, and the residue was purified by silica gel column chromatography. By performing the above steps, compound (1F) (Rf ２ In this case, k, which indicates the average degree of polymerization, is 4.4. 3.6 g of a polymer (number average molecular weight 1139) was obtained.

[0253] 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] = 3.25 to 4.45 (13H), 6.00 to 7.50 (2H) 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)

[0254] Example 7 The same procedure as in Example 6 was carried out, except that 0.8 g (molecular weight 202, 4.0 mmol) of compound (Ep-2) represented by the following formula (17) was used instead of compound (Ep-1) represented by formula (16) in the second reaction of the above-mentioned Example 6, to obtain compound (1G) (Rf ２ In this case, k, which indicates the average degree of polymerization, is 4.4. 3.7 g of a polymer (number average molecular weight 1183) was obtained.

[0255] The compound (Ep-2) represented by formula (17) was synthesized by a method in which a compound in which the hydroxyl group of ethylene glycol monoallyl ether was protected was oxidized with dihydropyran.

[0256] (In formula (17), THP represents a tetrahydropyranyl group.)

[0257] 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] = 3.25 to 4.50 (17H), 6.00 to 7.50 (2H) 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)

[0258] Example 8 The same procedure as in Example 6 was carried out, except that 0.7 g (molecular weight 188, 4.0 mmol) of compound (Ep-3) represented by the following formula (18) was used instead of compound (Ep-1) represented by formula (16) in the second reaction of the above-mentioned Example 6, to obtain compound (1H) (Rf ２ In this case, k, which indicates the average degree of polymerization, is 4.4. 3.5 g of a polymer (number average molecular weight 1124) was obtained.

[0259] The compound (Ep-3) represented by formula (18) was synthesized by reacting solketal with epibromohydrin.

[0260]

[0261] 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] = 3.25 to 4.55 (19H), 6.00 to 7.50 (2H) 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)

[0262] Example 9 The same procedure as in Example 6 was carried out, except that 1.2 g (molecular weight 320, 4.0 mmol) of compound (Ep-4) represented by the following formula (19) was used instead of compound (Ep-1) represented by formula (16) in the second reaction of the above-mentioned Example 6, to obtain compound (1I) (Rf ２ In this case, k, which indicates the average degree of polymerization, is 4.4. 3.9 g of a polymer (number average molecular weight 1256) was obtained.

[0263] Compound (Ep-4) represented by formula (19) was synthesized by the following method. A tert-butyldimethylsilyl (TBS) group was introduced as a protecting group into the primary hydroxyl group of 3-allyloxy-1,2-propanediol, and a methoxymethyl (MOM) group was introduced as a protecting group into the secondary hydroxyl group of the resulting compound. The TBS group was removed from the resulting compound, and the resulting primary hydroxyl group was reacted with 2-bromoethoxytetrahydropyran. The double bond of the resulting compound was oxidized. Compound (Ep-4) represented by formula (19) was obtained by the above steps.

[0264] (In formula (19), THP represents a tetrahydropyranyl group, and MOM represents a methoxymethyl group.)

[0265] 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] = 3.25 to 4.60 (23H), 6.00 to 7.60 (2H) 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)

[0266] Example 10 The same procedure as in Example 6 was carried out, except that 1.2 g (molecular weight 300, 4.0 mmol) of compound (Ep-5) represented by the following formula (20) was used instead of compound (Ep-1) represented by formula (16) in the second reaction of the above-mentioned Example 6, to obtain compound (1J) (Rf ２In this case, k, which indicates the average degree of polymerization, is 4.4. 4.0 g of a polymer (number average molecular weight 1281) was obtained.

[0267] Compound (Ep-5) represented by the following formula (20) was synthesized by the method shown below. Two equivalents of 3-buten-1-ol were reacted with one equivalent of epichlorohydrin. The obtained compound was reacted with 3,4-dihydro-2H-pyran to protect the secondary hydroxyl group of the compound with a tetrahydropyranyl (THP) group. One double bond of the obtained compound was oxidized using m-chloroperbenzoic acid. Compound (Ep-5) represented by formula (20) was obtained by the above steps.

[0268] (In formula (20), THP represents a tetrahydropyranyl group.)

[0269] 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] = 1.50 to 1.90 (2H), 3.10 to 4.40 (22H), 4.90 to 5.40 (2H), 5.60 to 6.00 (1H), 6.00 to 7.60 (2H) 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)

[0270] [Example 11] The same procedure as in Example 1 was carried out, except that 1.7 g of N-(2-bromoethyl)acetamide (molecular weight 166, 10.5 mmol) was used instead of 2-bromoacetamide, to obtain compound (1K) (Rf １ In this example, i, which indicates the average degree of polymerization, is 4.5, and j, which indicates the average degree of polymerization, is 4.5. 4.5 g of a polymer (number average molecular weight 1167) was obtained.

[0271] The obtained compound (1K) 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 2.20 (6H), 3.70 to 4.45 (12H), 6.00 to 7.50 (2H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -55.6 to -51.5 (9F), -77.5 (2F), -80.5 (2F), -91.2 to -88.4 (18F)

[0272] Example 12 The same procedure as in Example 1 was carried out, except that 1.9 g (molecular weight 180, 10.5 mmol) of compound (1L-1) represented by the following formula (21) was used instead of 2-bromoacetamide, to obtain compound (1L) (Rf １ In this example, i, which indicates the average degree of polymerization, is 4.5, and j, which indicates the average degree of polymerization, is 4.5. 4.6 g of a polymer (number average molecular weight 1195) was obtained.

[0273] The compound (1L-1) represented by the following formula (21) was synthesized by reacting 2-bromoethylamine with propionic anhydride.

[0274]

[0275] The obtained compound (1L) 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), 1.90 to 2.20 (4H), 3.70 to 4.45 (12H), 6.00 to 7.50 (2H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -55.6 to -51.5 (9F), -77.5 (2F), -80.5 (2F), -91.2 to -88.4 (18F)

[0276] Example 13 The same procedure as in Example 3 was carried out, except that 3.2 g (molecular weight 301, 10.5 mmol) of compound (1M-1) represented by the following formula (22) was used instead of 3-bromo-propionamide, to obtain compound (1M) (Rf１ In this formula, i representing the average degree of polymerization is 7.1, and j representing the average degree of polymerization is 0.

[0277] The compound (1M-1) represented by the following formula (22) was synthesized by acetylating the amine moiety of 2-(2-aminoethoxy)ethanol and then reacting the hydroxyl group with p-toluenesulfonyl chloride.

[0278] (In formula (22), Ts represents a p-toluenesulfonyl group.)

[0279] The obtained compound (1M) 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 2.20 (6H), 3.30 to 4.55 (20H), 6.00 to 7.50 (2H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -78.6 (2F), -81.3 (2F), -91.0 to -88.1 (28.4F)

[0280] Example 14 The same procedure as in Example 3 was carried out, except that 3.3 g (molecular weight 315, 10.5 mmol) of compound (1N-1) represented by the following formula (23) was used instead of 3-bromo-propionamide, to obtain compound (1N) (Rf １ In this example, i, which indicates the average degree of polymerization, is 7.1, and j, which indicates the average degree of polymerization, is 0.

[0281] Compound (1N-1) represented by the following formula (23) was synthesized by acetylating the amine moiety of 2-(3-aminopropoxy)ethanol and then reacting the hydroxyl group with p-toluenesulfonyl chloride.

[0282] (In formula (23), Ts represents a p-toluenesulfonyl group.)

[0283] The obtained compound (1N) １H-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 1.30 (4H), 1.90 to 2.20 (6H), 3.30 to 4.55 (20H), 6.00 to 7.50 (2H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -78.6 (2F), -81.3 (2F), -91.0 to -88.1 (28.4F)

[0284] Example 15 The same procedure as in Example 5 was carried out, except that 3.3 g (molecular weight 315, 10.5 mmol) of compound (1O-1) represented by the following formula (24) was used instead of the amide compound represented by formula (14) in the above-mentioned Example 5, to obtain compound (1O) (Rf ２ In this case, k, which indicates the average degree of polymerization, is 4.4. 4.7 g of a polymer (number average molecular weight 1294) was obtained.

[0285] The compound (1O-1) represented by the following formula (24) was synthesized by acetylating the amine moiety of 3-(2-aminoethoxy)propanol and then reacting the hydroxyl group with p-toluenesulfonyl chloride.

[0286] (In formula (24), Ts represents a p-toluenesulfonyl group.)

[0287] The obtained compound (1O) 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 1.40 (4H), 1.90 to 2.20 (6H), 3.30 to 4.55 (20H), 6.00 to 7.50 (2H) 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 16 The same procedure as in Example 6 was carried out, except that 0.9 g (molecular weight 166, 5.5 mmol) of N-(2-bromoethyl)acetamide was used instead of 2-bromoacetamide in the first reaction of the above-mentioned Example 6, to obtain compound (1P) (Rf ２ In this case, k, which indicates the average degree of polymerization, is 4.4. 3.5 g of a polymer (number average molecular weight 1167) was obtained.

[0289] The obtained compound (1P) 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 2.20 (3H), 3.20 to 4.45 (15H), 6.00 to 7.60 (1H) 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)

[0290] Example 17 The same procedure as in Example 7 was carried out, except that 0.9 g (molecular weight 166, 5.5 mmol) of N-(2-bromoethyl)acetamide was used instead of 2-bromoacetamide in the first reaction of the above-mentioned Example 7, to obtain compound (1Q) (Rf ２ In this case, k, which indicates the average degree of polymerization, is 4.4. 3.6 g of a polymer (number average molecular weight 1211) was obtained.

[0291] The obtained compound (1Q) 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 2.20 (3H), 3.20 to 4.50 (19H), 6.00 to 7.60 (1H) 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)

[0292] Example 18 The same procedure as in Example 8 was carried out, except that 0.9 g (molecular weight 166, 5.5 mmol) of N-(2-bromoethyl)acetamide was used instead of 2-bromoacetamide in the first reaction of the above-mentioned Example 8, to obtain compound (1R) (Rf ２ In this case, k, which indicates the average degree of polymerization, is 4.4. 3.4 g of a polymer (number average molecular weight 1152) was obtained.

[0293] The obtained compound (1R) 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 2.20 (3H), 3.20 to 4.55 (21H), 6.00 to 7.60 (1H) 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)

[0294] Example 19 The same procedure as in Example 9 was carried out, except that 0.9 g (molecular weight 166, 5.5 mmol) of N-(2-bromoethyl)acetamide was used instead of 2-bromoacetamide in the first reaction of the above-mentioned Example 9, to obtain compound (1S) (Rf ２ In this case, k, which indicates the average degree of polymerization, is 4.4. 3.8 g of a polymer (number average molecular weight 1284) was obtained.

[0295] The obtained compound (1S) 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 2.20 (3H), 3.20 to 4.60 (25H), 6.00 to 7.60 (1H) 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)

[0296] Example 20 The same procedure as in Example 10 was carried out, except that 0.9 g (molecular weight 166, 5.5 mmol) of N-(2-bromoethyl)acetamide was used instead of 2-bromoacetamide in the first reaction of the above-mentioned Example 10, to obtain compound (1T) (Rf ２ In this case, k, which indicates the average degree of polymerization, is 4.4. 3.8 g of a polymer (number average molecular weight 1309) was obtained.

[0297] The obtained compound (1T) 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] = 1.50 to 1.85 (2H), 1.90 to 2.20 (3H), 3.10 to 4.40 (24H), 4.90 to 5.40 (2H), 5.60 to 6.00 (1H), 6.00 to 7.60 (1H) 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)

[0298] Example 21 (First Reaction) In a 100 mL recovery flask, HOCH ２ CF ２ O (CF ２ CF ２ O) i (CF ２ O) j CF ２ CH ２ 5.0 g of a compound (number average molecular weight: 724, molecular weight distribution: 1.1) represented by the formula OH (where i, representing the average degree of polymerization, is 3.0 and j, representing the average degree of polymerization, is 3.0), 1.0 g of 2-bromoacetamide (molecular weight: 137, 7.6 mmol), and 10.1 mL of N,N-dimethylacetamide (DMF) were charged and stirred at room temperature to form a mixed solution. 4.7 g of cesium carbonate (molecular weight: 325, 14.5 mmol) was added to this mixed solution, and the mixture was reacted at 70°C for 8 hours with stirring.

[0299] The reaction product obtained after the reaction was cooled to 0°C, and 50 mL of an aqueous ammonium chloride solution was added to terminate the reaction. The resulting reaction solution was transferred to a separatory funnel and extracted three times with 100 mL of ethyl acetate. The organic layer was washed with brine and 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 4.0 g of a compound represented by the following formula (25) as intermediate compound (2A-1).

[0300] (In formula (25), Rf １ is represented by the above formula, and Rf １ The average degree of polymerization, i, is 3.0, and the average degree of polymerization, j, is 3.0.

[0301] (Second Reaction) Under a nitrogen gas atmosphere, 4.0 g (number average molecular weight 781) of the compound represented by formula (25), which is intermediate compound (2A-1), 0.35 g (molecular weight 137, 2.6 mmol) of epibromohydrin, and 3.8 mL of t-butanol were placed in a 100 mL recovery flask and stirred at room temperature until the mixture became homogeneous. 0.4 g (molecular weight 112, 4.1 mmol) of potassium tert-butoxide was added to this homogeneous solution, and the mixture was allowed to react at 70°C for 16 hours with stirring.

[0302] The reaction product obtained after the reaction was cooled to 0°C, and 50 mL of an aqueous ammonium chloride solution was added to stop the reaction. The resulting reaction solution was transferred to a separatory funnel and extracted three times with 100 mL of ethyl acetate. The organic layer was washed with brine and dehydrated over anhydrous sodium sulfate. After filtering off the desiccant, the filtrate was concentrated, and the residue was purified by silica gel column chromatography. By performing the above steps, compound (2A) (the two Rf １ In this example, i, which indicates the average degree of polymerization, is 3.0, and j, which indicates the average degree of polymerization, is 3.0. 5.0 g of a polymer (number average molecular weight 1618) was obtained.

[0303] 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] = 3.50 to 4.45 (18H), 6.00 to 7.50 (4H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -55.6 to -51.5 (12F), -77.5 (4F), -80.5 (4F), -91.2 to -88.4 (24F)

[0304] [Example 22] In the first reaction of the above-mentioned Example 21, HOCH ２ CF ２ O (CF ２ CF ２ O) i (CF ２ O) j CF ２ CH ２ OH (where i representing the average degree of polymerization is 3.0, and j representing the average degree of polymerization is 3.0), ２ CF ２ O (CF ２ CF ２ O) i (CF ２ O) j CF ２ CH ２ The same procedure as in Example 21 was carried out to obtain compound (2B) (two Rf １ In this formula, i representing the average degree of polymerization is 5.0, and j representing the average degree of polymerization is 0. 5.2 g of a polymer (number average molecular weight 1714) was obtained.

[0305] 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] = 2.50 to 2.95 (6H), 3.50 to 4.45 (18H), 6.00 to 7.50 (2H) １９ F-NMR (acetone-D ６): δ [ppm] = -78.6 (4F), -81.3 (4F), -91.0 to -88.1 (40F)

[0306] [Example 23] In the first reaction of the above-mentioned Example 21, HOCH ２ CF ２ O (CF ２ CF ２ O) i (CF ２ O) j CF ２ CH ２ OH (where i representing the average degree of polymerization is 3.0, and j representing the average degree of polymerization is 3.0), ２ CF ２ CF ２ O (CF ２ CF ２ CF ２ O) ｋ CF ２ CF ２ CH ２ The same procedure as in Example 21 was carried out, except that 5.0 g of a compound (number average molecular weight: 776, molecular weight distribution: 1.1) represented by the formula OH (where k, representing the average degree of polymerization, is 3.0) was used, and 1.1 g of 3-bromo-propionamide (molecular weight: 152, 7.1 mmol) was used instead of 2-bromoacetamide, to obtain compound (2C) (two Rf ２ In this case, k, which indicates the average degree of polymerization, is 3.0. 5.2 g of a polymer (number average molecular weight 1750) was obtained.

[0307] 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] = 1.90 to 2.30 (4H), 3.50 to 4.45 (18H), 6.00 to 7.50 (4H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.3 to -82.8 (24F), -86.4 (8F), -124.0 (8F), -130.0 to -128.2 (12F)

[0308] Example 24 The same procedure as in Example 22 was carried out, except that 1.2 g of N-(2-bromoethyl)acetamide (molecular weight 166, 7.3 mmol) was used instead of 2-bromo-N-methylacetamide in the first reaction of the above-mentioned Example 22, to obtain compound (2D) (two Rf １ In this formula, i representing the average degree of polymerization is 5.0, and j representing the average degree of polymerization is 0. 5.1 g of a polymer (number average molecular weight 1742) was obtained.

[0309] 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] = 1.90 to 2.30 (6H), 3.30 to 4.45 (22H), 6.00 to 7.50 (2H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.3 to -82.8 (24F), -86.4 (8F), -124.0 (8F), -130.0 to -128.2 (12F)

[0310] Example 25 The same procedure as in Example 23 was carried out, except that 2.1 g (molecular weight 301, 7.1 mmol) of compound (1M-1) represented by formula (22) was used instead of 3-bromo-propionamide in the first reaction of the above-mentioned Example 23, to obtain compound (2E) (two Rf ２ In this case, k, which indicates the average degree of polymerization, is 3.0. 5.3 g of a polymer (number average molecular weight: 1866) was obtained.

[0311] 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] = 1.90 to 2.30 (6H), 3.30 to 4.55 (30H), 6.00 to 7.50 (2H) １９ F-NMR (acetone-D ６): δ [ppm] = -84.3 to -82.8 (24F), -86.4 (8F), -124.0 (8F), -130.0 to -128.2 (12F)

[0312] The compounds (1A) to (1T) and (2A) to (2E) of Examples 1 to 25 thus obtained were applied to the formula (1), and the values ​​of n and R １ , R ２ , R ３ , R ４ The structures of the compounds are shown in Tables 1 to 5.

[0313]

[0314]

[0315]

[0316]

[0317]

[0318] Comparative Example 1 Compound (3A) represented by the following formula (26) was synthesized by the method described in Patent Document 1.

[0319] (In formula (26), i, which indicates the average degree of polymerization, represents 4.5, and j represents 4.5.)

[0320] Comparative Example 2 Compound (3B) represented by the following formula (27) was synthesized by the method described in Patent Document 2.

[0321] (In formula (27), i, which indicates the average degree of polymerization, represents 6.2, and j represents 6.2.)

[0322] [Comparative Example 3] Compound (3C) represented by the following formula (28) was synthesized with reference to the method described in Patent Document 3. More specifically, compound (3C) was produced with reference to the method described in Example 1 of Patent Document 3, except that 2-(2-aminoethoxy)ethanol was used instead of 3-amino-1,2-propanediol in Example 1 of Patent Document 3.

[0323] (In formula (28), i, which indicates the average degree of polymerization, represents 4.5, and j represents 4.5.)

[0324] Comparative Example 4 Compound (3D) represented by the following formula (29) was synthesized by the method described in Patent Document 4.

[0325] (Rf in formula (29) １ In the formula, i, which indicates the average degree of polymerization, is 3.2, and j is 3.2.

[0326] Comparative Example 5 Compound (3E) represented by the following formula (30) was synthesized by the method described in Patent Document 4.

[0327] (Rf in formula (30) １ In the formula, i, which indicates the average degree of polymerization, represents 3.2, and j represents 3.2.

[0328] Comparative Example 6 Compound (3F) represented by the following formula (31) was synthesized by the following method.

[0329] (Rf in formula (31) ２ In this case, k, which indicates the average degree of polymerization, is 4.0.

[0330] That is, under a nitrogen atmosphere, HOCH ２ CF ２ CF ２ O (CF ２ CF ２ CF ２ O) ｋ CF ２ CF ２ CH ２ A fluorine-based compound represented by the formula OH (where k, which indicates the average degree of polymerization, is 4.0), 1,7-octadiepoxide, and t-butanol were charged and stirred at room temperature until homogeneous. Potassium tert-butoxide was further added to this homogeneous solution, and the mixture was stirred at 70°C for 16 hours to react. At this time, the reaction ratio of the fluorine-based compound to 1,7-octadiepoxide was approximately 1:2 (molar ratio). As a result, Rf ２ A first intermediate compound having a secondary hydroxyl group and an epoxy group at both ends was obtained.

[0331] Next, the same procedure as in the production of the first intermediate compound was carried out, except that 4-methoxyphenyl glycidyl ether was used instead of 1,7-octadiepoxide in the production of the first intermediate compound, and the reaction ratio of the fluorine-based compound to 4-methoxyphenyl glycidyl ether was set to about 1:1 (molar ratio). ２ Finally, the first intermediate compound and the second intermediate compound were reacted in t-butanol using potassium tert-butoxide to synthesize compound (3F).

[0332] The number average molecular weights (Mn) of the compounds of Examples 1 to 25 and Comparative Examples 1 to 6 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, and the results are shown in Tables 6 and 7. 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, differences in the operations used to synthesize the compounds, and the like.

[0333]

[0334]

[0335] Next, solutions for forming lubricating layers were prepared by the method described below using the compounds obtained in Examples 1 to 25 and Comparative Examples 1 to 6. 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 25 and Comparative Examples 1 to 6.

[0336] "Lubricant Layer-Forming Solution" Each of the fluorine-containing ether compounds obtained in Examples 1 to 25 and Comparative Examples 1 to 6 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.

[0337] "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 25 and Comparative Examples 1 to 6 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.

[0338] "Film Thickness Measurement" For the lubricating layers of the magnetic recording media of Examples 1 to 25 and Comparative Examples 1 to 6 obtained in this manner, the peak heights of the C-F vibrational stretching 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. The results are shown in Tables 6 and 7.

[0339] "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).

[0340] 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.

[0341] Next, the magnetic recording media of Examples 1 to 25 and Comparative Examples 1 to 6 were subjected to and evaluated for wear resistance, pickup characteristics, and chemical resistance by the following methods. The results are shown in Tables 6 and 7.

[0342] "Wear Resistance Test" Using a pin-on-disk friction and wear tester, a 2 mm diameter alumina ball as a contact was slid on the lubricating layer of the magnetic recording medium at a load of 40 gf and a sliding speed of 0.25 m / sec, and the friction coefficient of the surface of the lubricating layer was measured. The sliding time until the friction coefficient of the surface of the lubricating layer suddenly increased was then measured. The sliding time until the friction coefficient suddenly increased was measured four times for the lubricating layer of each magnetic recording medium, and the average value (time) was used as an index of the wear resistance of the lubricant coating.

[0343] (Evaluation Criteria for Wear Resistance) The evaluation of wear resistance based on the sliding time until the coefficient of friction suddenly increases was as follows: A (Excellent): 670 seconds or more B (Good): 570 seconds or more, less than 670 seconds C (Fair): 450 seconds or more, less than 570 seconds D (Fail): Less than 450 seconds

[0344] The time until the coefficient of friction increases sharply can be used as an indicator of the wear resistance of the lubricating layer for the following reason: The lubricating layer of a magnetic recording medium wears out as the magnetic recording medium is used, and when the lubricating layer is worn away, the contact and protective layer come into direct contact, causing a sharp increase in the coefficient of friction. The time until the coefficient of friction increases sharply is thought to be correlated with friction testing.

[0345] "Pickup characteristic test" The magnetic recording medium and magnetic head were mounted on a spin stand, and rotation was performed at room temperature under reduced pressure (approximately 250 torr), and the magnetic head was floated at a fixed point for 10 minutes. Thereafter, the surface of the magnetic head facing the magnetic recording medium was 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.

[0346] (Evaluation criteria for pickup characteristics) A (Excellent): Signal strength less than 150 (very little adhesion amount) B (Good): Signal strength 150 or more but less than 280 (little adhesion amount) C (Acceptable): Signal strength 280 or more but less than 1000 (lots of adhesion amount) D (Unacceptable): Signal strength 1000 or more (very little adhesion amount)

[0347] Chemical Resistance Test: Contamination of magnetic recording media by environmental substances that generate contaminants in a high-temperature environment was investigated using the following method: Si ions were used as the environmental substances, and the amount of Si adsorption was measured as the amount of contaminants that contaminate the magnetic recording media generated by the environmental substances.

[0348] Specifically, the magnetic recording medium to be evaluated was kept in a high-temperature environment of 85°C and 0% humidity in the presence of siloxane-based Si rubber for 240 hours. Next, the amount of Si adsorption present on the surface of the magnetic recording medium was analyzed and measured using secondary ion mass spectrometry (SIMS), and the degree of contamination by Si ions was evaluated as the amount of Si adsorption. The evaluation of the amount of Si adsorption was performed using a numerical value when the result of Comparative Example 3 was set to 1.00, and was evaluated as follows.

[0349] (Chemical substance resistance evaluation criteria) A (Excellent): Less than 0.60 B (Good): 0.60 or more, less than 0.75 C (Fair): 0.75 or more, less than 1.00 D (Fail): 1.00 or more

[0350] "Overall Evaluation" An overall evaluation was made based on the results of the abrasion resistance test, the pick-up property test, and the chemical resistance test, according to the following evaluation criteria. The results are shown in Tables 6 and 7.

[0351] (Evaluation criteria for overall evaluation) A: The abrasion resistance test, pick-up property test, and chemical resistance test all received an A. B: The abrasion resistance test, pick-up property test, and chemical resistance test all received an A or B, with one or more of them receiving a B. C: One or more of the abrasion resistance test, pick-up property test, and chemical resistance test received a C, and no D was received. D: One or more of the abrasion resistance test, pick-up property test, and chemical resistance test received a D.

[0352] As shown in Table 6, the magnetic recording media of Examples 1 to 25 were all rated A or B in the wear resistance test, pickup characteristic test, and chemical resistance test, and the overall evaluation result was A or B. This confirms that the magnetic recording media of Examples 1 to 25 have excellent wear resistance, a high pickup suppression effect, and high chemical resistance.

[0353] In contrast, as shown in Table 7, the magnetic recording media of Comparative Examples 1 to 6, which had lubricating layers formed using any of compounds (3A) to (3F), were all evaluated as B, C, or D in the wear resistance test, pickup characteristic test, and chemical resistance test, with at least one test item evaluated as C or D, and were inferior to the magnetic recording media of Examples 1 to 25. This is presumably because the magnetic recording media of Comparative Examples 1 to 6 did not form lubricating layers using the fluorine-containing ether compound represented by formula (1).

[0354] More specifically, the magnetic recording media of Comparative Examples 1 to 3 each have a lubricating layer formed using compounds (3A) to (3C), each of which has one perfluoropolyether chain and an amide bond moiety in at least one of its terminal groups.

[0355] In compounds (3A) and (3B), a divalent linking group containing a secondary hydroxyl group is located between the perfluoropolyether chain and the amide bond site. The secondary hydroxyl group contained in this linking group increases the surface free energy of the entire compound, which is presumably why the evaluation of chemical resistance in Comparative Examples 1 and 2 was inferior to that in Examples 1 to 25. In particular, the lubricating layer of Comparative Example 1 formed using compound (3A) was inferior to that in Examples 1 to 25 in terms of pickup resistance and chemical resistance. Furthermore, in compound (3B), the divalent linking group has an aromatic ring, and the aromatic ring and the amide bond site are directly bonded to form a highly planar terminal group. Therefore, the adhesion of the amide bond site and the aromatic ring to the protective layer was too strong, which is presumably why the lubricating layer of Comparative Example 2 formed using compound (3B) lost lubricity and had insufficient wear resistance.

[0356] In the compound (3C), -CF forming a perfluoropolyether chain ２ The carbon atom of - and the carbon atom of the amide bond site (C(=O)N) are directly bonded without a linking group. Therefore, the bulkiness of the perfluoropolyether chain inhibits the bonding of the amide bond site to the active site on the protective layer. Furthermore, since the amide group, which is difficult to rotate freely, is directly bonded to the perfluoropolyether chain, the mobility (degree of freedom) of the amide bond site is considered to be low. For this reason, it is presumed that the lubricating layer of Comparative Example 3 containing compound (3C) had insufficient adhesion to the protective layer, and was insufficient in wear resistance, pick-up resistance, and chemical resistance.

[0357] The magnetic recording media of Comparative Examples 4 to 6 each have a lubricating layer formed using compounds (3D) to (3F). Compounds (3D) and (3E) have a skeleton in which two or three perfluoropolyether chains are bonded via a linking group containing a secondary hydroxyl group. Compounds (3D) and (3E) have an amide bond moiety as a polar group at the end of this skeleton, and a divalent linking group containing a secondary hydroxyl group is located between the perfluoropolyether chain and the amide bond moiety. In the lubricating layers of Comparative Examples 4 and 5 formed using compounds (3D) and (3E), the secondary hydroxyl groups contained in the divalent linking group have too strong an adsorption to the protective layer, presumably impairing lubricity and resulting in insufficient wear resistance. Furthermore, the secondary hydroxyl groups contained in the divalent linking group presumably cause the surface free energy of the entire compound to be too high, resulting in the lubricating layers of Comparative Examples 4 and 5 having inferior chemical resistance and pick-up resistance evaluations compared to Examples 1 to 25.

[0358] Compound (3F) has a skeleton in which three perfluoropolyether chains are bonded via a linking group containing a secondary hydroxyl group.Compound (3F) does not have an amide bond site at both ends of this skeleton, but has an aromatic ring, and a divalent linking group containing a secondary hydroxyl group is arranged between the perfluoropolyether chain and the aromatic ring.Therefore, it is estimated that the lubricating layer of Comparative Example 6 formed using compound (3F) has insufficient adsorption with the active site on the protective layer, and the evaluation results of wear resistance, pick-up resistance and chemical resistance are inferior to those of Examples 1 to 25.

[0359] 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 excellent chemical resistance, good wear resistance, and a high pick-up suppression effect, even if it is thin.

[0360] 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 -R ３ -CH ２ -R ２ ) ｎ -CH ２ -O-R ４ (1) (In formula (1), R １ is represented by the following formula (2-1) or formula (2-2). R ２ is a perfluoropolyether chain. R ４ is an organic group having 1 to 50 carbon atoms and at least one polar group. R ３ is a divalent linking group having at least one hydroxyl group. n is an integer of 0 to 2. When n is 1 or 2, a plurality of R ２ may be partly or entirely the same or different from each other. When n is 2, the two 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 12 carbon atoms that does not contain a polar group and may contain an ether oxygen atom. Y １ and Z １ are each independently an organic group having 1 to 30 carbon atoms that 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.) (In formula (2-2), X ２ is a divalent linking group having 1 to 12 carbon atoms that does not contain a polar group and may contain an ether oxygen atom. Y ２ is an organic group having 1 to 30 carbon atoms that 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 30 carbon atoms that 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.) 2. X in the formula (2-1) １ and X in the formula (2-2) ２ are each independently represented by the following formula (3), the fluorine-containing ether compound according to claim 1. (In formula (3), p is an integer of 2 to 4, q is an integer of 0 to 2, and r is an integer of 1 to 4. When q is 2, the two p's may be the same or different. The left end in formula (3) is the side bonded to the oxygen atom of -R ２ -CH ２ -O-, and the right end is the side bonded to the carbonyl carbon atom or nitrogen atom constituting the amide bond.) 3. Y in the formula (2-1) １ and Z １ at least one of which is a hydrogen atom, and Y in the formula (2-2) ２ is a hydrogen atom. The fluorine-containing ether compound according to claim 1 or claim 2 4. R in the formula (1) ３ The fluorine-containing ether compound according to claim 1 or 2, wherein R is a divalent linking group represented by the following formula (4). (In the formula (4), s is an integer of 1 to 3, and t is an integer of 1 to 3. The oxygen atom at the left end in the formula (4) is bonded to -CH １ - on the R ２ side, and the oxygen atom at the right end is bonded to -CH ４ - on the R ２ side.) 5. R in the formula (1) ４ is not a group represented by the formula (2-1) or the formula (2-2), and at least one of the polar groups contained in R ４ is a hydroxyl group. The fluorine-containing ether compound according to claim 1 or claim 2 6. R in the formula (1) ４ The fluorine-containing ether compound according to claim 5, wherein R contains two or three polar groups, and at least one of the polar groups is a secondary hydroxyl group.

7. R in the formula (1) ４ is any group represented by the following formula (5-1) to formula (5-3), the fluorine-containing ether compound according to claim 5. (In formula (5-1), a is an integer of 1 to 2, and b is an integer of 0 to 3. Q １ is an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, an alkynyl group, or a polar group. When a is 1, Q １ is a polar group. When Q １ is an aromatic hydrocarbon group or an unsaturated heterocyclic group, the atoms constituting the ring structure in Q １ are bonded to the methylene group adjacent to Q １ . When Q １ is an alkenyl group or an alkynyl group, the carbon atom constituting the unsaturated bond in Q １ is bonded to the methylene group adjacent to Q １ .) (In formula (5-2), c is an integer of 1 to 3, d is an integer of 0 to 1, and e is an integer of 0 to 3. Q ２ is an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, an alkynyl group, or a polar group. When d is 0, Q ２ is a polar group. When Q ２ is an aromatic hydrocarbon group or an unsaturated heterocyclic group, the atoms constituting the ring structure in Q ２ are bonded to the methylene group adjacent to Q ２ . When Q ２ is an alkenyl group or an alkynyl group, the carbon atom constituting the unsaturated bond in Q ２ is bonded to the methylene group adjacent to Q ２ .) (In formula (5-3), f is an integer of 1 to 3, g is an integer of 0 or 1, and h is an integer of 0 to 3. Q ３ is an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, an alkynyl group, or a polar group. When g is 0, Q ３ is a polar group. When Q ３ is an aromatic hydrocarbon group or an unsaturated heterocyclic group, the atoms constituting the ring structure in Q ３ are bonded to the methylene group adjacent to Q ３ .) (When Q ３ When Q is an alkenyl group or an alkynyl group, the carbon atom constituting the unsaturated bond in Q ３ is bonded to the methylene group adjacent to Q ３ .) 8. R in the formula (1) ４ The fluorine-containing ether compound according to claim 1 or 2, wherein R is represented by the formula (2-1) or (2-2).

9. R in the formula (1) １ and R ４ are the same, and the fluorine-containing ether compound according to claim 8.

10. R in the formula (1) ２ is, independently of each other, a perfluoropolyether chain represented by the following formula (6), the fluorine-containing ether compound according to claim 1 or claim 2. —(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 — (6) (In the formula (6), w2, w3, w4, w5 represent the average degree of polymerization and each independently represents 0 to 20. However, all of w2, w3, w4, w5 do not become 0 at the same time. w1, 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 (6) have no particular limitation on the sequence order.) 11. R in the formula (1) ２ is any one selected from perfluoropolyether chains represented by the following formulas (6-1) to (6-4). The fluorine-containing ether compound according to claim 1 or claim 2. -CF ２ -(OCF ２ CF ２ ) ｗ７ -(OCF ２ ) ｗ８ -OCF ２ - (6-1) (In the formula (6-1), 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 - (6-2) (In the formula (6-2), 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 - (6-3) (In the formula (6-3), 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 - (6-4) (In the formula (6-4), 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.) 12. The fluorine-containing ether compound according to claim 1 or 2, wherein n is 0 in the formula (1).

13. The fluorine-containing ether compound according to claim 1 or 2, wherein n is 1 in the formula (1).

14. The fluorine-containing ether compound according to claim 1 or 2, wherein n is 2 in the formula (1).

15. The fluorine-containing ether compound represented by the formula (1) is any compound represented by the following formulas (1A) to (1T) and (2A) to (2E), and the fluorine-containing ether compound according to claim 1. (In the formula (1A), Rf １ where i and j represent the average degree of polymerization, i represents 1 to 20, and j represents 0 to 20.) (In the formula (1B), Rf １ where i and j represent the average degree of polymerization, i represents 1 to 20, and j represents 0 to 20.) (In the formula (1C), Rf １ where i and j represent the average degree of polymerization, i represents 1 to 20, and j represents 0 to 20.) (In the formula (1D), Rf １ where i and j represent the average degree of polymerization, i represents 1 to 20, and j represents 0 to 20.) (In the formula (1E), Rf ２ where k represents the average degree of polymerization and represents 1 to 15.) (In the formula (1F), Rf ２ where k represents the average degree of polymerization and represents 1 to 15.) (In the formula (1G), Rf ２ where k represents the average degree of polymerization and represents 1 to 15.) (In the formula (1H), Rf ２ where k represents the average degree of polymerization and represents 1 to 15.) (In the formula (1I), Rf ２ where k represents the average degree of polymerization and represents 1 to 15.) (In the formula (1J), Rf ２ where k represents the average degree of polymerization and represents 1 to 15.) (In the formula (1K), Rf １ where i and j represent the average degree of polymerization, i represents 1 to 20, and j represents 0 to 20.) (In the formula (1L), Rf １ where i and j represent the average degree of polymerization, i represents 1 to 20, and j represents 0 to 20.) (In the formula (1M), Rf １ where i and j represent the average degree of polymerization, i represents 1 to 20, and j represents 0 to 20.) (In the formula (1N), Rf １ where i and j represent the average degree of polymerization, i represents 1 to 20, and j represents 0 to 20.) (In the formula (1O), Rf ２ where k represents the average degree of polymerization and represents 1 to 15.) (Rf in formula (1P) ２ In the formula (1Q), k represents the average degree of polymerization and is from 1 to 15. ２ In the formula (1R), k represents an average degree of polymerization and is from 1 to 15. ２ In the formula (1S), k represents the average degree of polymerization and is from 1 to 15. ２ In the formula (1T), k represents the average degree of polymerization and is from 1 to 15. ２ In the formula, k represents the average degree of polymerization and is a number ranging from 1 to 15. (Two Rf in formula (2A) １ In the formula, i and j each represent an average degree of polymerization, where i is an integer of 1 to 20, and j is an integer of 0 to 20. １ In the formula (2B), the average degrees of polymerization may be the same or different. １ In the formula, i and j each represent an average degree of polymerization, where i is an integer of 1 to 20, and j is an integer of 0 to 20. １ In the formula (2C), the average degrees of polymerization may be the same or different. ２ In the formula, k represents the average degree of polymerization and represents 1 to 15. ２ In the formula (2D), the average degrees of polymerization may be the same or different. １ In the formula, i and j each represent an average degree of polymerization, where i is an integer of 1 to 20, and j is an integer of 0 to 20. １ In the formula (2E), the average degrees of polymerization may be the same or different. ２ In the formula, k represents the average degree of polymerization and represents 1 to 15. ２ The average degrees of polymerization may be the same or different.

16. The fluorine-containing ether compound according to claim 1 or 2, wherein the number average molecular weight is in the range of 500 to 10,000.

17. A lubricant for a magnetic recording medium, comprising the fluorine-containing ether compound according to claim 1 or 2.

18. 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 claim 1 or 2.

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

Images