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

Abstract

Provided is a fluorine-containing ether compound represented by the following formula: R1–CH2–R2[–CH2–R3–CH2–R2]x–CH2–R4. (In the formula, x is 0-2. R2 represents a perfluoropolyether chain. R3 represents a divalent linking group having 1-4 polar groups. R1 and R4 each represent a terminal group having 1-4 polar groups and 1-50 carbon atoms. At least one of R1 and R4 is a group represented by formula (2). In formula (2), a is 0-2. b of a moieties and c of a moieties are 1-6. One of d and e is 0 and the other is 1-6. Ra, Rb, Rc, and Rd of a moieties each represent an alkyl group having 1-8 carbon atoms or a hydrogen atom.)

Description

Fluorine-containing ether compounds, lubricants for magnetic recording media, and magnetic recording media

[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 based on Japanese Patent Application No. 2024-221695, filed in Japan on December 18, 2024, the contents of which are incorporated herein by reference.

[0002] To improve the recording density of magnetic recording and playback devices, development of magnetic recording media suitable for high recording densities is underway. Conventionally, magnetic recording media have been formed by creating a recording layer on a substrate and then forming a protective layer made of carbon or the like on top of the recording layer. The protective layer protects the information recorded on the recording layer and also improves the sliding properties of the magnetic head. However, simply providing a protective layer on top of the recording layer does not provide sufficient durability for the magnetic recording media. For this reason, a lubricant is generally applied to the surface of the protective layer to form a lubricating layer.

[0003] Examples of lubricants used when forming the lubricating layer of a magnetic recording medium include -CF ２ A proposed solution involves incorporating a compound having a polar group such as a hydroxyl group or an amino group at the terminal end of a fluorine-based polymer having a repeating structure containing -.

[0004] For example, Patent Documents 1 and 2 describe a perfluoropolyether chain with methylene groups (-CH) at both ends. ２ Glycerin structure (-O-CH) via (-O-CH) ２ -CH(OH)-CH ２ -O-), a structure in which the glycerin structure is extended by a methylene group, glycerin structure (-O-CH ２ -CH(OH)-CH ２ A fluorine-containing ether compound is disclosed in which one of the following structures is bonded: a structure in which multiple -O-) groups are linked by sharing each other's oxygen atoms; a structure in which multiple glycerol structures with methylene groups are linked by sharing each other's oxygen atoms; or a structure in which a glycerol structure with methylene groups and a glycerol structure are linked by sharing each other's oxygen atoms.

[0005] Patent documents 3 to 6 disclose fluorine-containing ether compounds having a perfluoropolyether chain with polar terminal groups at both ends, and a substituent bonded to a carbon atom bonded to a hydroxyl group in one of the terminal groups.

[0006] Patent documents 7 and 8 describe a method where methylene groups (-CH) are attached to both ends. ２ A fluorine-containing ether compound is disclosed, having a skeleton in which two perfluoropolyether chains are linked via a divalent linking group having a polar group to which a fluorine-(-) is attached, and polar end groups are attached to both ends of the skeleton via a methylene group.

[0007] Japanese Patent No. 7337159 (B) International Publication No. 2024 / 225106 (A) International Publication No. 2019 / 049585 (A) International Publication No. 2019 / 054148 (A) International Publication No. 2021 / 054202 (A) Japanese Patent No. 5789710 (B) U.S. Patent No. 10540997 (B) International Publication No. 2024 / 071399 (A)

[0008] To increase the capacity of magnetic recording and playback devices, development of magnetic recording media suitable for high recording densities is progressing. In recent years, in order to improve the recording density of magnetic recording media, there has been a demand to further shorten the distance between the magnetic head and the magnetic layer of the magnetic recording media, thereby reducing magnetic spacing (levitation height). For this reason, there is a demand to make the thickness of the lubricating layer in the magnetic recording media even thinner.

[0009] However, generally, reducing the thickness of the lubricating layer tends to decrease the levitation stability and corrosion resistance of the magnetic recording medium. For these reasons, there has been a need for a lubricating layer that provides excellent levitation stability and corrosion resistance to magnetic recording media even when its thickness is reduced.

[0010] The present invention has been made in view of the above circumstances, and an object thereof is to provide a fluorine-containing ether compound that can form a lubricating layer capable of obtaining a magnetic recording medium having excellent floating stability and corrosion resistance, and that can be suitably used as a material for a lubricant for a magnetic recording medium. Another object of the present invention is to provide a lubricant for a magnetic recording medium that contains the fluorine-containing ether compound of the present invention and can form a lubricating layer capable of obtaining a magnetic recording medium having excellent floating stability and corrosion resistance. Another object of the present invention is to provide a magnetic recording medium having a lubricating layer containing the fluorine-containing ether compound of the present invention and having good floating stability and corrosion resistance.

[0011] The present invention includes the following aspects [1] to

[16] .

[0012] [1] A fluorine-containing ether compound represented by the following formula (1). R １ -CH ２ -R ２ [-CH ２ -R ３ -CH ２ -R ２ ｘ -CH ２ -R ４ (1) (In formula (1), x represents an integer of 0 to 2. R ２ is a perfluoropolyether chain. When x is 1 or 2, (x + 1) R ２ may be partially or entirely the same, or may be different from each other. R ３ is a divalent linking group having 1 to 4 polar groups. When x is 2, the two R ３ may be the same or different from each other. R １ and R ４ are each independently a terminal group having 1 to 4 polar groups and having 1 to 50 carbon atoms. At least one of R １ and R ４ is a terminal group represented by the following formula (2).)

[0013] (In formula (2), a represents an integer from 0 to 2. a b and a c each independently represent an integer from 1 to 6. However, in a single structural unit, at least one of b and c is 1. One of d and e is 0, and the other represents an integer from 1 to 6. Ra, Rb, Rc, and a Rd each independently represent an alkyl group having 1 to 8 carbon atoms or a hydrogen atom. However, when e is 0, at least one of Ra, Rb, Rc, and a Rd is an alkyl group having 1 to 8 carbon atoms, and when e is from 1 to 6, Rc is a hydrogen atom, and at least one of Ra, Rb, and a Rd is an alkyl group having 1 to 8 carbon atoms.)

[0014] [2] The fluorine-containing ether compound according to [1], wherein the terminal group represented by formula (2) is a terminal group represented by any of the following formulas (2-1) to (2-7).

[0015] (In equation (2-1), d1 represents an integer from 1 to 6. Ra １ Rb represents an alkyl group with 1 to 8 carbon atoms. １ (wherein b2, c2, and d2 each independently represent an integer from 1 to 6, provided that at least one of b2 and c2 is 1.) ２ Rb represents an alkyl group with 1 to 8 carbon atoms. ２ represents an alkyl group having 1 to 8 carbon atoms or a hydrogen atom. ) (In formula (2-3), d3 represents an integer from 1 to 6. Rc ３ Rc represents an alkyl group having 1 to 8 carbon atoms. ) (In formula (2-4), b4, c4, and d4 each independently represent an integer from 1 to 6, provided that at least one of b4 and c4 is 1. ４ Rd represents an alkyl group having 1 to 8 carbon atoms. ) (In formula (2-5), b5, c5, and d5 each independently represent an integer from 1 to 6, provided that at least one of b5 and c5 is 1. ５ represents an alkyl group having 1 to 8 carbon atoms. ) (In formula (2-6), b6, c6, and d6 each independently represent an integer from 1 to 6, provided that at least one of b6 and c6 is 1. Ra ６ and Rd ６Each of these independently represents an alkyl group having 1 to 8 carbon atoms, and Rb ６ (wherein b7, c7, and d7 represent an alkyl group having 1 to 8 carbon atoms or a hydrogen atom.) (In formula (2-7), b7, c7, and d7 each independently represent an integer from 1 to 6, provided that at least one of b7 and c7 is 1. Rc ７ and Rd ７ Each of these independently represents an alkyl group having 1 to 8 carbon atoms. ) (In formula (2-8), b8, c8, and e8 each independently represent an integer from 1 to 6, where at least one of b8 and c8 is 1. Rd ８ (This represents an alkyl group with 1 to 8 carbon atoms.)

[0016] [3] R in formula (1) １ and R ４ The fluorine-containing ether compound according to [1] or [2], wherein both of the terminal groups are independently represented by formula (2). [4] R in formula (1) １ and R ４ The fluorine-containing ether compound described in [3] is the same as the one described above.

[0017] [5] R in formula (1) １ and R ４ A fluorine-containing ether compound according to [1] or [2], wherein only one of the terminal groups is represented by formula (2) and the other is represented by formula (3) below. -O-[M] ｍ - [N] ｎ - [P] ｐ- [Q] (3) (In formula (3), m represents an integer from 0 to 3, and n and p each independently represent 0 or 1. Each of the m [M] is independently a divalent linking group represented by the following formula (3M). The n [N] are divalent linking groups represented by the following formula (3N). The p [P] are divalent linking groups represented by the following formula (3P). [Q] is a polar group, a halogeno group, a monovalent aliphatic organic group having 1 to 30 carbon atoms containing at least one ether oxygen atom, an alkyl group having 1 to 30 carbon atoms, an alkenyl group having 2 to 30 carbon atoms, an alkynyl group having 2 to 30 carbon atoms, an organic group having 6 to 30 carbon atoms containing an aromatic ring, or a hydrogen atom. In formula (3), the order of the m [M], n [N], and p [P] may be changed. However, the total number of polar groups included in formula (3) is 1 to 4, and [P] and [Q] do not directly bond.)

[0018] (In equation (3M), m1 and m2 each independently represent integers from 1 to 6, where at least one of m1 and m2 is 1. Equation (3M) is R on the left side.) ２ It is coupled to the side.) (Equation (3N) is R on the left side.) ２ (It is joined to the side.) (In equation (3P), p1 represents an integer from 0 to 6. In equation (3P), each of the p1 Rp is independently -CH ２ -, -CF ２ -, -CH(CH ３ )-,-C(CH ３ ) ２ It represents either -. In equation (3P), the left side is R ２ (It will be joined to the side.)

[0019] [6] The fluorine-containing ether compound according to [5], wherein [Q] in formula (3) is a monovalent aliphatic organic group having 1 to 30 carbon atoms, comprising at least one of a polar group, a halogeno group, and an ether oxygen atom, and the polar group is at least one selected from the group consisting of a hydroxyl group, a cyano group, a carboxamide group, and an acetamide group.

[0020] [7] The fluorine-containing ether compound according to [5], wherein the terminal group represented by formula (3) is a terminal group represented by any of the following formulas (3-1) to (3-10).

[0021] (In equation (3-1), m01 represents an integer from 1 to 2. Each of the m01 m11 and m21 independently represents an integer from 1 to 6. However, within a single structural unit, at least one of m11 and m21 is 1. q1 represents an integer from 1 to 6. X ３１ q3 represents one of the following: a hydroxyl group, a cyano group, an acetamide group, or a carboxamide group.) (In formula (3-2), m02 represents an integer from 1 to 2. The two m02s m12 and m22 each independently represent an integer from 1 to 6. However, in one structural unit, at least one of m12 and m22 is 1.) (In formula (3-3), m03 represents an integer from 1 to 2. The three m03s m13 and m23 each independently represent an integer from 1 to 6. However, in one structural unit, at least one of m13 and m23 is 1. q3 represents an integer from 0 to 6. X ３３ (where m24 represents an integer from 1 to 6, and q4 represents an integer from 0 to 6.) ３４ (where q5 represents one of the following groups: methyl group, vinyl group, ethynyl group, phenyl group, methoxyphenyl group, cyanophenyl group, carboxamidephenyl group, acetaminophenyl group, trifluoromethyl group, or pentafluoroethyl group.) (In formula (3-5), q5 represents an integer from 1 to 6. X ３５ (where q6 represents one of the following: a hydroxyl group, a cyano group, an acetamide group, or a carboxamide group.) (In formula (3-6), q6 represents an integer from 0 to 6. X ３６ (where p17 represents one of the following: methyl group, vinyl group, ethynyl group, phenyl group, methoxyphenyl group, trifluoromethyl group, or pentafluoroethyl group.) (In formula (3-7), p17 represents an integer from 1 to 6. There are p17 Rp ａ , Rp ｂ Each of these independently represents either a hydrogen atom or a methyl group. (In formula (3-8), p18 represents an integer from 1 to 6.)

[0022] [8] x in formula (1) is 1 or 2, and x R ３A fluorine-containing ether compound according to any of [1] to [7], wherein each of the following is an independent divalent linking group represented by formula (4): -O-[S] ｓ - [T] ｔ - [U] ｕ - (4) (In formula (4), s represents an integer from 0 to 3, and t and u each independently represent 0 or 1. However, s and t cannot be 0 at the same time. Each of the s [S] is independently a divalent linking group represented by the following formula (4S). [T] is a divalent linking group represented by the following formula (4T). [U] is a divalent linking group represented by the following formula (4U). In formula (4), the order of the s [S], t [T], and u [U] may be changed. However, the total number of polar groups included in formula (4) is between 1 and 4.)

[0023] (In formula (4S), s1 and s2 each independently represent integers from 1 to 6, except that at least one of s1 and s2 is 1. The left side of formula (4S) is bonded to the oxygen atom side in formula (4).) (In formula (4T), t1 represents an integer from 0 to 4. The left side of formula (4T) is bonded to the oxygen atom side in formula (4).) (In formula (4U), u1 represents an integer from 0 to 6. Each of the u1 Ru in formula (4U) independently represents -CH ２ -, -CF ２ -, -CH(CH ３ )-,-C(CH ３ ) ２ This represents either of the following. In formula (4U), the left side is bonded to the oxygen atom in formula (4).

[0024] [9] The fluorine-containing ether compound according to [8], wherein the divalent linking group represented by formula (4) is a divalent linking group represented by any of the following formulas (4-1) to (4-9).

[0025] (In formula (4-1), s11 represents an integer from 1 to 6, and s21 represents an integer from 1 to 6. However, at least one of s11 and s21 is 1.) (In formula (4-2), s02 represents an integer from 2 to 3.) (In formula (4-3), t13 represents an integer from 0 to 4.) (In formula (4-4), s14 represents an integer from 1 to 6.) (In formula (4-5), s15 represents an integer from 1 to 6, and s25 represents an integer from 1 to 6.) (In formula (4-6), s16 represents an integer from 1 to 6, and s26 represents an integer from 1 to 6. However, at least one of s16 and s26 is 2 or more.) (In formula (4-7), s17 represents an integer from 1 to 6, and s27 represents an integer from 1 to 6. However, at least one of s17 and s27 is 2 or more.) (In formula (4-8), u18 represents an integer from 0 to 6. u18 Ru ａ , Ru ｂ each independently represents a hydrogen atom or a methyl group.) (In formula (4-9), u19 represents an integer from 1 to 6.)

[0026]

[10] The (x + 1) R ２ in the above formula (1) are each independently a perfluoropolyether chain represented by the following formula (5), the fluorine-containing ether compound according to any one of [1] to [9]. -(CF ２ )-O-(CF ｗ１ O) ２ -(CF ｗ２ CF ２ O) ２ -(CF ｗ３ CF ２ CF ２ O) ２ -(CF ｗ４ CF ２ CF ２ CF ２ O) ２ -(CF ｗ５ CF ２ ) ｗ６ - (5) (In formula (5), 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. (CF ２ O), (CF２ CF ２ O), (CF ２ CF ２ CF ２ O), (CF ２ CF ２ CF ２ CF ２ The sequence order of O) has no particular limitation.)

[0027]

[11] The perfluoropolyether chain represented by the formula (5) is any one selected from the perfluoropolyether chains represented by the following formulas (5-1) to (5-4). The fluorine-containing ether compound according to

[10] . -CF ２ -(OCF ２ CF ２ ) ｈ -(OCF ２ ) ｉ -OCF ２ - (5-1) (In the formula (5-1), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20.) -CF ２ CF ２ -(OCF ２ CF ２ CF ２ ) ｊ -OCF​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​- (5-4) (In formula (5-4), w8 and w9 represent the average degree of polymerization and each independently represents 1 to 20. w7 and w10 are CF ２ This represents the average number of units, each independently representing 1 to 2.

[0028]

[12] A fluorine-containing ether compound according to any one of [1] to

[11] , wherein the number average molecular weight is in the range of 500 to 10000.

[0029]

[13] A compound represented by any of the following formulas (AA) to (CE), and Rf in the compounds represented by the following formulas (AA) to (AZ), (BD) to (BG), and (CA) to (CE). ２ , Rf in the compounds represented by the following formulas (BA) and (BB) １ , Rf in the compound represented by the following formula (BC) ３ The fluorine-containing ether compounds described in any of [1] to

[12] are perfluoropolyether chains represented by the following formulas.

[0030] (Rf in equation (AA)) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. ) (Rf in equation (AB) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. ) (Rf in equation (AC) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. ) (Rf in equation (AD) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. ) (Rf in equation (AE) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. ) (Rf in equation (AF) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. ) (Rf in formula (AG) ２ In this case, j represents the average degree of polymerization and is expressed as 1 to 15.

[0031] (Rf in equation (AH)) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. ) (Rf in equation (AI) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. ) (Rf in equation (AJ) ２In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. ) (Rf in equation (AK) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. ) (Rf in equation (AL) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. ) (Rf in equation (AM) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. ) (Rf in equation (AN) ２ In this case, j represents the average degree of polymerization and is expressed as 1 to 15.

[0032] (Rf in equation (AO)) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. ) (Rf in equation (AP) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. ) (Rf in equation (AQ) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. (Rf in equation (AR)) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. (Rf in equation (AS)) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. ) (Rf in equation (AT) ２ In this case, j represents the average degree of polymerization and is expressed as 1 to 15.

[0033] (Rf in equation (AU)) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. ) (Rf in equation (AV) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. ) (Rf in equation (AW) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. (Rf in equation (AX)) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. ) (Rf in equation (AY) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. ) (Rf in equation (AZ) ２ In this case, j represents the average degree of polymerization and is expressed as 1 to 15.

[0034] (Rf in formula (BA)) １ In this equation, h and i represent the average degree of polymerization, where h is 1 to 20 and i is 0 to 20.) (Rf in equation (BB)１ In this equation, h and i represent the average degree of polymerization, where h is 1 to 20 and i is 0 to 20. ) (Rf in equation (BC) ３ In this equation, k represents the average degree of polymerization and is expressed as 1 to 10. ) (Rf in formula (BD) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. ) (Rf in equation (BE) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. ) (Rf in formula (BF) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. ) (Rf in formula (BG) ２ In this case, j represents the average degree of polymerization and is expressed as 1 to 15.

[0035] (The two Rf in equation (CA) ２ In this, j represents the average degree of polymerization and is expressed as 1 to 15. Two Rf ２ The values ​​of j in this equation may be the same or different.) (The two Rf in equation (CB) ２ In this, j represents the average degree of polymerization and is expressed as 1 to 15. Two Rf ２ In this equation, j may be the same or different.) (The two Rf in equation (CC) ２ In this, j represents the average degree of polymerization and is expressed as 1 to 15. Two Rf ２ In this equation, j may be the same or different. ) (The two Rf in equation (CD) ２ In this, j represents the average degree of polymerization and is expressed as 1 to 15. Two Rf ２ In this equation, j may be the same or different.) (The three Rf in equation (CE) ２ In this, j represents the average degree of polymerization and is expressed as 1 to 15. Three Rf ２ In this case, j may be different in each instance, or some or all of them may be the same.

[0036]

[0037]

[14] A lubricant for a magnetic recording medium comprising a fluorine-containing ether compound as described in any of [1] to

[13] .

[15] 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 comprises a fluorine-containing ether compound as described in any of [1] to

[13] .

[16] The magnetic recording medium according to

[15] , wherein the average film thickness of the lubricating layer is 0.5 nm to 2.0 nm.

[0038] The fluorine-containing ether compound of the present invention is a compound represented by the above formula (1), and is therefore suitable as a material for a lubricant for magnetic recording media. Because the lubricant for magnetic recording media of the present invention contains the fluorine-containing ether compound of the present invention, it can form a lubricating layer that provides a magnetic recording media with good floating stability and corrosion resistance.

[0039] 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 levitation stability and corrosion resistance, and is highly reliable and durable. Furthermore, because the magnetic recording medium of the present invention has a lubricating layer that provides a magnetic recording medium with good levitation stability and corrosion resistance, the thickness of the lubricating layer can be reduced. Therefore, the magnetic recording medium of the present invention can contribute to reducing magnetic spacing and further reduce the amount of levitation of the magnetic head.

[0040] This is a schematic cross-sectional view showing one embodiment of the magnetic recording medium of the present invention.

[0041] To solve the above problems, the present inventors have diligently investigated the following. Conventionally, fluorine-containing ether compounds having terminal groups containing polar groups such as hydroxyl groups have been preferably used as materials for lubricants for magnetic recording media applied to the surface of protective layers (hereinafter sometimes abbreviated as "lubricant").

[0042] However, when a thin lubricating layer is formed on a protective layer using conventional fluorine-containing ether compounds having terminal groups containing polar groups, it has been difficult to achieve a magnetic recording medium with good buoyancy stability and corrosion resistance, as described below. Specifically, the polar groups in the fluorine-containing ether compound bind to active sites on the protective layer, improving the adhesion of the lubricating layer to the protective layer. If the adhesion of the lubricating layer to the protective layer is insufficient, the coating of the lubricating layer on the protective layer becomes inadequate, and the smoothness of the surface of the magnetic recording medium is lost. As a result, the magnetic head is more likely to collide with protrusions on the surface of the magnetic recording medium, and sufficient buoyancy stability cannot be obtained. In addition, if the coating of the lubricating layer on the protective layer is insufficient, water can penetrate from the outside into the parts not covered by the lubricating layer, making the magnetic recording medium susceptible to corrosion. Therefore, the corrosion resistance of the magnetic recording medium becomes poor.

[0043] A common method for improving the adhesion of the lubricating layer to the protective layer is to increase the number of polar groups in the fluorine-containing ether compound contained in the lubricating layer. However, if there are too many polar groups in the fluorine-containing ether compound, many polar groups that do not interact with the protective layer will be generated in the lubricating layer. As a result, these polar groups that do not interact with the protective layer in the lubricating layer will aggregate and form clumps, making it easier for the magnetic head to collide with these clumps. Consequently, the levitation stability of the magnetic recording medium will decrease.

[0044] Furthermore, polar groups in fluorine-containing ether compounds have a strong interaction with water. Therefore, if a fluorine-containing ether compound contains many highly hydrophilic polar groups, the lubricating layer formed by the fluorine-containing ether compound itself becomes more susceptible to absorbing water. As a result, the lubricating layer itself can induce corrosion of the magnetic recording medium, preventing the acquisition of a magnetic recording medium with sufficient corrosion resistance.

[0045] As described above, simply increasing the number of polar groups in the fluorine-containing ether compound in the lubricating layer to improve its adhesion to the protective layer is insufficient to form a lubricating layer that provides sufficient buoyancy stability and corrosion resistance for magnetic recording media. Therefore, in order to realize a lubricating layer that provides good buoyancy stability and corrosion resistance for magnetic recording media, it is necessary to devise a structure for the fluorine-containing ether compound containing polar groups so as to prevent aggregation of polar groups within the lubricating layer and to suppress the absorption of water by the polar groups themselves.

[0046] Therefore, the inventors focused on the structure of fluorine-containing ether compounds, the interactions between polar groups contained in fluorine-containing ether compounds, and the hydrophilicity of the polar groups themselves, and conducted thorough investigations. As a result, they concluded that a fluorine-containing ether compound should have terminal groups with polar groups at both ends, and at least one of the terminal groups has a structure in which an alkyl group with 1 to 8 carbon atoms is bonded to at least one of the carbon atoms to which a hydroxyl group (-OH) is bonded, selected from the following structures (1) to (5).

[0047] (1) Glycerin structure [G1] (-O-CH ２ -CH(OH)-CH ２ -O- or -O-CH(CH ２ -OH)-CH ２ -O-). (2) -CH in the glycerin structure [G1] ２ - A carbon-extended glycerin structure [G2] formed by extending the carbon-extended glycerin structure with a methylene group. (3) A structure in which two or three of the above glycerin structures [G1] are linked together by sharing each other's oxygen atoms. (4) A structure in which two or three of the above carbon-extended glycerin structures [G2] are linked together by sharing each other's oxygen atoms. (5) A structure in which one or two of the above glycerin structures [G1] and one or two of the above carbon-extended glycerin structures [G2] are linked together by sharing each other's oxygen atoms, and the total number of the above glycerin structures [G1] and above carbon-extended glycerin structures [G2] is two or three.

[0048] In a lubricating layer containing such a fluorine-containing ether compound, as shown below, aggregation of polar groups contained in the fluorine-containing ether compound can be suppressed, water can be prevented from being absorbed due to excessive hydrophilicity of the hydroxyl groups, and a sufficient number of hydroxyl groups can interact with the protective layer can be secured.

[0049] More specifically, the hydroxyl groups bonded to the alkyl groups in the above-mentioned fluorine-containing ether compounds are less likely to interact with other polar groups due to steric hindrance caused by the alkyl groups. Therefore, the aggregation and formation of clumps of polar groups in the fluorine-containing ether compounds can be suppressed. As a result, magnetic recording media having a lubricating layer containing the above-mentioned fluorine-containing ether compounds exhibit good levitation stability.

[0050] Furthermore, the hydroxyl groups bonded to the alkyl group-containing carbon atoms in the above-mentioned fluorine-containing ether compounds have reduced polarity and hydrophilicity due to the presence of a hydrophobic part consisting of an alkyl group nearby. Therefore, hydroxyl groups bonded to alkyl group-containing carbon atoms interact less with water than hydroxyl groups not bonded to alkyl group-containing carbon atoms. Consequently, the lubricating layer containing the above-mentioned fluorine-containing ether compounds suppresses water uptake. As a result, the impact of water uptake in the lubricating layer on corrosion of the magnetic recording medium is reduced, and a magnetic recording medium with good corrosion resistance is obtained.

[0051] Furthermore, the alkyl group introduced to the carbon atom to which the hydroxyl group is bonded in the above-mentioned fluorine-containing ether compound has a relatively high degree of freedom of motion. Therefore, the effect of the alkyl group introduced to the carbon atom to which the hydroxyl group is bonded on inhibiting the motion of the hydroxyl group located nearby and suppressing interaction with the protective layer is small. Moreover, the hydroxyl group in the above-mentioned fluorine-containing ether compound has a high degree of conformational freedom in the above-mentioned glycerin structure [G1] or in the above-mentioned glycerin structure [G1] -CH ２- is a hydroxyl group in a carbon-extended glycerin structure [G2] formed by extending the carbon atom with a methylene group. Therefore, the hydroxyl group bonded to the alkyl group-introduced carbon atom can interact sufficiently with the protective layer. Consequently, the lubricating layer containing the above-mentioned fluorine-containing ether compound can suppress the number of polar groups in the fluorine-containing ether compound while ensuring a sufficient number of hydroxyl groups that can interact with the protective layer. As a result, sufficient adhesion to the protective layer can be ensured, and a lubricating layer can be formed that provides a magnetic recording medium with good floating stability and corrosion resistance.

[0052] From the above, a lubricating layer containing a fluorine-containing ether compound having terminal groups with polar groups at both ends, and having a structure in which at least one of the terminal groups has an alkyl group with 1 to 8 carbon atoms bonded to at least one of the carbon atoms to which a hydroxyl group (-OH) included in any of the structures selected from (1) to (5) above is bonded, exhibits sufficient adhesion to the protective layer, suppresses aggregation of polar groups, and inhibits water uptake by the polar groups. This makes it possible to realize a lubricating layer that yields a magnetic recording medium with good buoyancy stability and corrosion resistance.

[0053] Furthermore, the inventors of the present invention have confirmed that by using a lubricant containing a fluorine-containing ether compound represented by formula (1), it is possible to form a lubricating layer that provides a magnetic recording medium with good buoyancy stability and corrosion resistance even when the thickness is reduced, and thus conceived the present invention.

[0054] The fluorine-containing ether compounds, lubricants for magnetic recording media, and magnetic recording media of the present invention will be described in detail below. However, the present invention is not limited to the embodiments shown below. Note that the term "polar group" in this specification does not include halogen groups (-F, -Cl, -Br, etc.) and ether bonds (-O-).

[0055] [Fluorine-containing ether compound] The fluorine-containing ether compound of this embodiment is represented by the following formula (1). R １ -CH ２ -R ２ [-CH ２ -R ３ -CH ２ -R ２ ] ｘ -CH２ -R ４ (1) (In equation (1), x represents an integer from 0 to 2. R ２ This is a perfluoropolyether chain. If x is 1 or 2, there are (x+1) R ２ They may be partially or entirely the same, or they may be different. ３ This is a divalent linking group having 1 to 4 polar groups. When x is 2, there are two R ３ They may be the same, or they may be different. １ and R ４ Each of these is an independent terminal group having 1 to 4 polar groups and 1 to 50 carbon atoms. １ and R ４ At least one of them is a terminal group represented by the following formula (2).

[0056] (In formula (2), a represents an integer from 0 to 2. a b and a c each independently represent an integer from 1 to 6. However, in a single structural unit, at least one of b and c is 1. One of d and e is 0, and the other represents an integer from 1 to 6. Ra, Rb, Rc, and a Rd each independently represent an alkyl group having 1 to 8 carbon atoms or a hydrogen atom. However, when e is 0, at least one of Ra, Rb, Rc, and a Rd is an alkyl group having 1 to 8 carbon atoms, and when e is from 1 to 6, Rc is a hydrogen atom, and at least one of Ra, Rb, and a Rd is an alkyl group having 1 to 8 carbon atoms.)

[0057] The fluorine-containing ether compound of this embodiment is as shown in formula (1), when x is 0, R ２ At one end of the perfluoropolyether chain represented by (hereinafter sometimes referred to as the PFPE chain), there is a methylene group, R １ The terminal group indicated by is attached, R ２ The other end of the PFPE chain shown by has a methylene group, R ４ The terminal group indicated by is attached. Also, if x is 1 or 2, R ３ The divalent linking group shown and R ２The skeleton has two or three perfluoropolyether chains, represented by , alternately linked via methylene groups. At one end of the skeleton, via a methylene group, R １ The terminal group indicated by is attached, and at the other end of the skeleton, via a methylene group, R ４ The terminal group indicated by is attached.

[0058] In the fluorine-containing ether compound represented by formula (1), R ２ The number of PFPE chains (x+1) shown is 1 to 3. When x is 1 or 2, in the fluorine-containing ether compound represented by formula (1), adjacent R ２ In between, there is a divalent linking group R which has 1 to 4 polar groups. ３ It is positioned there.

[0059] The fluorine-containing ether compound represented by formula (1) exhibits suppression of excessive molecular size compared to compounds with four or more PFPE chains. Therefore, compared to compounds with four or more PFPE chains, the fluorine-containing ether compound represented by formula (1) spreads more easily on the protective layer, forming a lubricating layer with a thin and uniform film thickness. Because a lubricating layer with a more uniform film thickness can be formed, x is preferably 0 or 1, and more preferably 0.

[0060] (R １ and R ４ (Terminal group shown by) R １ and R ４ Each of these is an independent terminal group having 1 to 4 polar groups and 1 to 50 carbon atoms. １ and R ４ At least one of them is a terminal group represented by formula (2) above. The fluorine-containing ether compound represented by formula (1) is R １ and R ４ It is preferable that both of these are terminal groups represented by formula (2), independently of each other. This is because it is easier to obtain a lubricating layer that can form a magnetic recording medium with better levitation stability and corrosion resistance.

[0061] R １ and R ４Of these, the number of polar groups in the terminal groups that do not correspond to formula (2) is 1 to 4. Furthermore, the number of polar groups (hydroxyl groups) in the terminal groups represented by formula (2) is 2 or more. Therefore, when a lubricating layer is formed on a protective layer using a lubricant containing a fluorine-containing ether compound, a suitable interaction occurs between the lubricating layer and the protective layer. R １ and R ４ The number of polar groups contained in each is preferably two or more. １ and R ４ When each polar group contained in the compound has two or more, it becomes easier to secure a sufficient number of polar groups that can participate in interactions with the protective layer and intermolecular interactions. As a result, the fluorine-containing ether compound can form a lubricating layer that exhibits even better adhesion to the protective layer and good levitation stability, resulting in a magnetic recording medium.

[0062] R １ and R ４ The number of polar groups contained in each is four or less. Therefore, in a lubricating layer containing a fluorine-containing ether compound, it is possible to suppress the aggregation and formation of clumps of the fluorine-containing ether compound due to excessive polarity, which would otherwise lead to a loss of smoothness in the lubricating layer. Also, R １ and R ４ If the number of polar groups contained in each compound is four or less, the hydrophilicity of the fluorine-containing ether compound is too high, preventing water from being absorbed into the magnetic recording medium. This results in a fluorine-containing ether compound that can form a lubricating layer, thus providing a highly corrosion-resistant magnetic recording medium. １ and R ４ Preferably, the number of polar groups contained in each is three or less.

[0063] R in equation (1) １ and R ４ The total number of polar groups is 3 or more, preferably 6 or less, and more preferably 4 to 6. Since the total number of polar groups is 3 or more, R １ and R ４The interaction between the polar groups and the protective layer is effectively achieved. As a result, a fluorine-containing ether compound is formed that can create a lubricating layer with high adhesion to the protective layer, and a lubricating layer can be formed that provides a magnetic recording medium with excellent buoyancy stability. Furthermore, if the total number of the above polar groups is six or less, the hydrophilicity of the fluorine-containing ether compound becomes too high, preventing water from being incorporated into the lubricating layer. Therefore, a lubricating layer can be formed that provides a magnetic recording medium with superior corrosion resistance.

[0064] R １ and R ４ The types of polar groups that each possess may be partially or entirely the same, or they may be different. Also, R １ The number of polar groups it possesses, and R ４ The number of polar groups in each of them may be the same or may be different. １ The number of polar groups it possesses, and R ４ The number of polar groups present is preferably the same, as this results in a more uniform coating state on the protective layer of the fluorine-containing ether compound, and allows for the formation of a lubricating layer with better adhesion.

[0065] R １ and R ４ Of these, the polar groups included in terminal groups that do not correspond to formula (2) are hydroxyl group (-OH), carboxyl group (-COOH), formyl group (-(C=O)H), and carbonyl group (-(C=O)R). ７ ;R ７ ( is an organic group.) (-SO ３ H), cyano group (-CN), and group having an amide bond (-NR ８ COR ９ or -CONR １０ R １１ ;R ８ , R ９ , R １０ and R １１ Each is independently a hydrogen atom or an organic group. (-NR) １２ R １３ ;R １２ and R １３Each of these is independently a hydrogen atom or an organic group. Preferably, it is at least one polar group selected from the group consisting of ).

[0066] Groups having an amide bond in a terminal group that does not fall under formula (2) include groups that bond to the carbon atom constituting the amide bond, as shown in the above formula (for example, a carboxamide group (-C(=O)NH) ２ )) and a group that bonds to the nitrogen atom constituting the amide bond (for example, an acetamide group (-NHC(=O)CH ３ )) includes both. In a group having an amide bond, the R in the above formula ８ and R ９ The and may be joined together to form a ring, and the R １０ and R １１ The R in the group having an amide bond may bond with each other to form a ring. ８ , R ９ , R １０ and R １１ Preferably, each of these is independently selected from the group consisting of a hydrogen atom, a methyl group, an ethyl group, a propyl group, and a butyl group.

[0067] R １ and R ４ Of these, the polar group included in the terminal group that does not correspond to formula (2) is preferably at least one polar group selected from the group consisting of hydroxyl group, cyano group, carboxamide group, and acetamide group. The reason is that hydroxyl group, cyano group, carboxamide group, and acetamide group are all chemically stable. Therefore, the lubricating layer containing the fluorine-containing ether compound having these polar groups will not deteriorate over time. In addition, hydroxyl group, cyano group, carboxamide group, and acetamide group are not too acidic and are less likely to corrode the substrate.

[0068] Among these polar groups, the hydroxyl group is the most preferred polar group to be included in terminal groups that do not correspond to formula (2). This is because when the polar group included in terminal groups that do not correspond to formula (2) is a hydroxyl group, the coating state of the protective layer of the fluorine-containing ether compound becomes more uniform.

[0069] R １ and R ４ Even if only one of them is a terminal group represented by formula (2), R １ and R ４ Even if both are terminal groups represented by formula (2), R １ The polar group that R ４ It is preferable that all polar groups present are hydroxyl groups. １ and R ４ This is because if all of the polar groups present are hydroxyl groups, the coating of the protective layer of the fluorine-containing ether compound becomes more uniform.

[0070] The fluorine-containing ether compound represented by formula (1) is R １ and R ４ Since each of the terminal groups represented by has one or more carbon atoms, the hydrophobicity of the terminal groups is increased. Therefore, it is possible to prevent water from being attracted to the lubricating layer, and a lubricating layer with good corrosion resistance can be formed. １ and R ４ The number of carbon atoms in each terminal group represented by is preferably 3 or more, and more preferably 4 or more.

[0071] R １ and R ４ Since the number of carbon atoms in each of the terminal groups represented by is 50 or less, the terminal groups have a flexible structure, resulting in good adhesion between the lubricating layer containing the fluorine-containing ether compound and the protective layer. As a result, a lubricating layer can be formed that yields a magnetic recording medium with good levitation stability. １ and R ４ The number of carbon atoms in each terminal group represented by is preferably 20 or less, and more preferably 15 or less.

[0072] (Terminal group represented by formula (2)) R １ and R ４ At least one of them is a terminal group represented by formula (2) above. The terminal group represented by formula (2) is R ２ The methylene group (-CH) is bonded to it. ２ It has an oxygen atom (ether oxygen atom) bonded to it (-). ２The oxygen atom bonded to the methylene group forms an ether bond (-O-) with the atoms bonded on either side of it. This ether bond imparts appropriate flexibility to the fluorine-containing ether compound represented by formula (1) and increases the affinity between the polar group of the terminal group represented by formula (2) and the protective layer. As a result, the fluorine-containing ether compound represented by formula (1) can form a lubricating layer with excellent adhesion to the protective layer.

[0073] The terminal group represented by formula (2) has (a + 2), i.e., 2 to 4 hydroxyl groups. Since the terminal group represented by formula (2) contains two or more polar groups, it is easier to ensure a sufficient number of polar groups that can participate in interactions with the protective layer and intermolecular interactions. As a result, the fluorine-containing ether compound can form a lubricating layer that provides even better adhesion to the protective layer and good buoyancy stability for magnetic recording media. Furthermore, since the terminal group represented by formula (2) contains four or fewer polar groups, it is possible to prevent the hydrophilicity of the fluorine-containing ether compound from becoming too high, which would allow water to be incorporated into the magnetic recording media through the lubricating layer. This results in a fluorine-containing ether compound that can form a lubricating layer that provides a magnetic recording media with high corrosion resistance. Preferably, the number of hydroxyl groups in the terminal group represented by formula (2) is 2 to 3. That is, a is preferably 0 or 1.

[0074] Furthermore, because the terminal group represented by formula (2) consists entirely of hydroxyl groups, the coating state on the protective layer of the fluorine-containing ether compound represented by formula (1) becomes more uniform.

[0075] The terminal group represented by formula (2) has a structure in which at least one of the carbon atoms to which a hydroxyl group (-OH) in any of the structures selected from (1) to (5) below is bonded is an alkyl group having 1 to 8 carbon atoms.

[0076] (1) Glycerin structure [G1] (-O-CH ２ -CH(OH)-CH ２ -O- or -O-CH(CH ２ -OH)-CH ２ -O-). (2) -CH in the glycerin structure [G1] ２- A carbon-extended glycerin structure [G2] formed by extending the carbon-extended glycerin structure with a methylene group. (3) A structure in which two or three of the above glycerin structures [G1] are linked together by sharing each other's oxygen atoms. (4) A structure in which two or three of the above carbon-extended glycerin structures [G2] are linked together by sharing each other's oxygen atoms. (5) A structure in which one or two of the above glycerin structures [G1] and one or two of the above carbon-extended glycerin structures [G2] are linked together by sharing each other's oxygen atoms, and the total number of the above glycerin structures [G1] and above carbon-extended glycerin structures [G2] is two or three.

[0077] The glycerin structure [G1] and the extended glycerin structure [G2] described above have appropriate rigidity. Therefore, the hydroxyl groups contained in the terminal group represented by formula (2) have suppressed interaction with water. Furthermore, the ether bonds of the glycerin structure [G1] and the extended glycerin structure [G2] impart appropriate mobility to the terminal group represented by formula (2). Therefore, the hydroxyl groups contained in the terminal group represented by formula (2) are more likely to participate in interaction with the protective layer. As a result, the fluorine-containing ether compound of this embodiment can form a lubricating layer that yields a magnetic recording medium with excellent floating stability and corrosion resistance.

[0078] When a in formula (2) is 2, the two structural units (-(CH ２ ) ｂ -CRd(OH)-(CH ２ ) ｃ The combinations of b and c in (-O-) may be different, or some or all of them may be the same. In formula (2), a b and a c each independently represent an integer from 1 to 6. In formula (2), one structural unit (-(CH) ２ ) ｂ -CRd(OH)-(CH ２ ) ｃIn -O-, at least one of b and c is 1. This prevents an excessive number of carbon atoms in the alkylene group between the carbon atom to which the hydroxyl group is bonded and the ether oxygen atom. This suppresses a decrease in the mobility of the hydroxyl group in the structural unit. In a single structural unit, it is preferable that both the values ​​of b and c are 1. If one of b and c is 1 and the other is not 1, the value of the other is preferably 2 to 4, and most preferably 2.

[0079] In equation (2), one of d and e is 0, and the other is an integer from 1 to 6. When d in equation (2) is an integer from 1 to 6 and e is 0, R ２ The methylene group (-CH) is bonded to it. ２ -) the oxygen atom bonded to the structural unit in formula (2) (-(CH) ２ ) ｃ The oxygen atom bonded to (-) is shared by one of the three oxygen atoms located at one end of the glycerin structure [G1] or the extended glycerin structure [G2] located at the very end. When e is 0 in formula (2), d is preferably 1 to 4, more preferably 1 to 2, and most preferably 1.

[0080] Furthermore, when d in equation (2) is 0 and e is an integer from 1 to 6, R ２ The methylene group (-CH) is bonded to it. ２ -) The oxygen atom bonded to the structural unit (-(CH) in formula (2) ２ ) ｃ The oxygen atom bonded to (-) is shared by the central oxygen atom among the three oxygen atoms of the glycerin structure [G1] or the extended glycerin structure [G2] located at the very end. When d in formula (2) is 0, e is preferably 1 to 4, more preferably 1 to 2, and most preferably 1.

[0081] In formula (2), Ra, Rb, Rc, and a Rd each independently represent an alkyl group having 1 to 8 carbon atoms or a hydrogen atom. However, when e is 0, at least one of Ra, Rb, Rc, and a Rd is an alkyl group having 1 to 8 carbon atoms. Also, when e is 1 to 6, Rc is a hydrogen atom, and at least one of Ra, Rb, and a Rd is an alkyl group having 1 to 8 carbon atoms.

[0082] Among Ra, Rb, Rc, and a Rd, the alkyl group has one or more carbon atoms, so the hydrophilicity of the hydroxyl group adjacent to the carbon atom into which the alkyl group is introduced is reduced. Furthermore, since the alkyl group has eight or fewer carbon atoms, the movement of the hydroxyl group adjacent to the carbon atom into which the alkyl group is introduced is sufficiently suppressed from being hindered by the introduced alkyl group. The alkyl group has 1 to 6 carbon atoms, more preferably 1 to 3, and most preferably 1.

[0083] The alkyl group described above may be linear, branched, or cyclic. The alkyl group is preferably linear or branched, and more preferably linear. This is because the movement of hydroxyl groups located near the alkyl group is less hindered by the alkyl group.

[0084] The alkyl group is preferably selected from methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, pentyl, cyclopentyl, hexyl, and cyclohexyl groups, more preferably selected from methyl, ethyl, propyl, and isopropyl groups, and most preferably a methyl group.

[0085] In formula (2), of Ra, Rb, Rc, and a Rd, the number of alkyl groups having 1 to 8 carbon atoms is preferably one or two, and most preferably one. In this case, the influence of the alkyl group on the hydroxyl group adjacent to the carbon atom into which the alkyl group is introduced is greatly reduced. As a result, the adhesion of the lubricating layer to the protective layer is further improved.

[0086] When Ra in formula (2) is an alkyl group having 1 to 8 carbon atoms and Rb is a hydrogen atom, the terminal group represented by formula (2) has a structure in which an alkyl group having 1 to 8 carbon atoms represented by Ra is introduced to the carbon atom bonded to the hydroxyl group located at the very end of the fluorine-containing ether compound. When Rb is a hydrogen atom, the movement of the hydroxyl group bonded to the carbon atom into which Ra is introduced is hardly hindered by the introduction of Ra, and the lubricant can adhere sufficiently to the protective layer, which is preferable. Moreover, the alkyl group substituted on the carbon atom adjacent to the terminal hydroxyl group suppresses the interaction between hydroxyl groups, making it less likely for polar groups to aggregate and form clumps. For this reason, when only Ra is an alkyl group having 1 to 8 carbon atoms and Rb is a hydrogen atom among Ra, Rb, Rc, and a Rd in formula (2), a lubricating layer can be formed that yields a magnetic recording medium with higher levitation stability. This effect is particularly pronounced when Ra is a methyl group.

[0087] Furthermore, when Ra and Rb are both alkyl groups having 1 to 8 carbon atoms, the terminal group represented by formula (2) has a structure in which two alkyl groups having 1 to 8 carbon atoms, represented by Ra and Rb, are introduced to the carbon atom bonded to the hydroxyl group located at the very end of the fluorine-containing ether compound. When Ra and Rb are both alkyl groups having 1 to 8 carbon atoms, the hydroxyl group adjacent to the carbon atom into which Ra and Rb are introduced becomes a tertiary hydroxyl group. Tertiary hydroxyl groups have significantly lower hydrophilicity compared to primary or secondary hydroxyl groups. Therefore, a lubricating layer can be formed that yields a magnetic recording medium with high corrosion resistance.

[0088] When Ra and Rb are both alkyl groups having 1 to 8 carbon atoms, Ra and Rb may be the same or different. When Ra and Rb are both alkyl groups having 1 to 8 carbon atoms, it is preferable that Ra and Rb are the same, as this facilitates the production of fluorine-containing ether compounds, and most preferably that both Ra and Rb are methyl groups. Furthermore, Ra and Rb may be bonded to each other to form a ring.

[0089] When all or any of Rc and a Rd are alkyl groups having 1 to 8 carbon atoms, the terminal group represented by formula (2) has a structure in which an alkyl group having 1 to 8 carbon atoms, represented by Rc and / or Rd, is introduced to the carbon atom bonded to the hydroxyl group located inside the terminal group. In this case, the hydroxyl group adjacent to the carbon atom to which the alkyl group is introduced becomes a tertiary hydroxyl group, resulting in a fluorine-containing ether compound with low hydrophilicity. Therefore, a lubricating layer can be formed that yields a magnetic recording medium with high corrosion resistance.

[0090] The terminal group represented by formula (2) is preferably a terminal group represented by any of the following formulas (2-1) to (2-8).

[0091] (In equation (2-1), d1 represents an integer from 1 to 6. Ra １ Rb represents an alkyl group with 1 to 8 carbon atoms. １ (wherein b2, c2, and d2 each independently represent an integer from 1 to 6, provided that at least one of b2 and c2 is 1.) ２ Rb represents an alkyl group with 1 to 8 carbon atoms. ２ represents an alkyl group having 1 to 8 carbon atoms or a hydrogen atom. ) (In formula (2-3), d3 represents an integer from 1 to 6. Rc ３ Rc represents an alkyl group having 1 to 8 carbon atoms. ) (In formula (2-4), b4, c4, and d4 each independently represent an integer from 1 to 6, provided that at least one of b4 and c4 is 1. ４ Rd represents an alkyl group having 1 to 8 carbon atoms. ) (In formula (2-5), b5, c5, and d5 each independently represent an integer from 1 to 6, provided that at least one of b5 and c5 is 1. ５ represents an alkyl group having 1 to 8 carbon atoms. ) (In formula (2-6), b6, c6, and d6 each independently represent an integer from 1 to 6, provided that at least one of b6 and c6 is 1. Ra ６ and Rd ６ Each of these independently represents an alkyl group having 1 to 8 carbon atoms, and Rb ６(wherein b7, c7, and d7 represent an alkyl group having 1 to 8 carbon atoms or a hydrogen atom.) (In formula (2-7), b7, c7, and d7 each independently represent an integer from 1 to 6, provided that at least one of b7 and c7 is 1. Rc ７ and Rd ７ Each of these independently represents an alkyl group having 1 to 8 carbon atoms. ) (In formula (2-8), b8, c8, and e8 each independently represent an integer from 1 to 6, where at least one of b8 and c8 is 1. Rd ８ (This represents an alkyl group with 1 to 8 carbon atoms.)

[0092] The terminal groups represented by formulas (2-1) and (2-3) are terminal groups in formula (2) where a is 0. These terminal groups have two hydroxyl groups. Therefore, a sufficient number of hydroxyl groups can be secured to interact with the protective layer, and a lubricating layer can be formed that yields a magnetic recording medium with good buoyancy stability. Furthermore, fluorine-containing ether compounds having terminal groups represented by formulas (2-1) and (2-3) can more effectively prevent water from being incorporated into the lubricating layer due to excessive hydrophilicity. Thus, fluorine-containing ether compounds having terminal groups represented by formulas (2-1) and (2-3) can form a lubricating layer that yields a magnetic recording medium with high corrosion resistance. It is preferable that d1 in formula (2-1) and d3 in formula (2-3) are 1, as this facilitates the production of the fluorine-containing ether compound.

[0093] The terminal groups represented by formulas (2-2) and (2-4) to (2-8) are terminal groups in formula (2) where a is 1. These terminal groups have three hydroxyl groups. Therefore, a sufficient number of hydroxyl groups can be ensured to interact with the protective layer. Moreover, it prevents the aggregation of polar groups that do not interact with the protective layer due to an excessive number of polar groups. Consequently, fluorine-containing ether compounds having these terminal groups can form a lubricating layer that yields magnetic recording media with even better buoyancy stability.

[0094] In formula (2-2), b2 is preferably 1. In formula (2-4), b4 is preferably 1. In formula (2-5), b5 is preferably 1. This is because it facilitates the production of fluorine-containing ether compounds. In addition, in formula (2-2), c2 and d2 are preferably 1 to 4, and more preferably 1 to 2. This is to suppress the decrease in the mobility of the hydroxyl group in formula (2) due to too many carbon atoms in the alkylene group.

[0095] The terminal groups represented by formulas (2-1), (2-2), and (2-6) are terminal groups in which Ra in formula (2) is an alkyl group having 1 to 8 carbon atoms. That is, they have a structure in which at least one alkyl group having 1 to 8 carbon atoms is introduced to the carbon atom bonded to the hydroxyl group located at the very end of the fluorine-containing ether compound. In this case, the hydroxyl group located at the very end, which has the highest mobility, has its interaction with other polar groups suppressed by steric hindrance from the alkyl group having 1 to 8 carbon atoms. Therefore, it is possible to more effectively prevent the polar groups contained in the fluorine-containing ether compound from aggregating and forming clumps, and to form a lubricating layer that yields a magnetic recording medium with even better levitation stability.

[0096] In equations (2-1), (2-2), and (2-6), Rb １ , Rb ２ , Rb ６ When is a hydrogen atom, Ra is the same as described above for the case where Ra in the terminal group represented by formula (2) is an alkyl group having 1 to 8 carbon atoms and Rb is a hydrogen atom. １ Ra ２ Ra ６ The movement of the hydroxyl group located at the very end of the fluorine-containing ether compound, which is bonded to the introduced carbon atom, is Ra １ Ra ２ Ra ６The presence of this compound has virtually no hindering effect. Therefore, it is preferable to have a fluorine-containing ether compound that can form a lubricating layer that adheres sufficiently to the protective layer.

[0097] Furthermore, in equations (2-1), (2-2), and (2-6), Rb １ , Rb ２ , Rb ６ When is an alkyl group having 1 to 8 carbon atoms, the hydroxyl group bonded to the carbon atom into which the two alkyl groups are introduced becomes a tertiary hydroxyl group with low hydrophilicity, similar to the explanation given above for the case where Ra and Rb in the terminal group represented by formula (2) are alkyl groups having 1 to 8 carbon atoms. Therefore, it becomes a fluorine-containing ether compound that can form a lubricating layer that yields a magnetic recording medium with higher corrosion resistance.

[0098] The terminal groups represented by formulas (2-3) to (2-8) are terminal groups in formula (2) where Rc and / or Rd are alkyl groups having 1 to 8 carbon atoms. That is, the terminal groups of the fluorine-containing ether compound have a structure in which an alkyl group having 1 to 8 carbon atoms is introduced to the carbon atom to which the hydroxyl group located inside is bonded. In this case, the hydroxyl group adjacent to the carbon atom to which the alkyl group is introduced becomes a tertiary hydroxyl group, and the hydrophilicity of the fluorine-containing ether compound is significantly reduced. Therefore, it is preferable to form a lubricating layer that yields a magnetic recording medium with excellent corrosion resistance.

[0099] The terminal group represented by formula (2) is preferably one of the following: (2-1A) to (2-1J), (2-2A) to (2-2M), (2-3A) to (2-3F), (2-4A) to (2-4G), (2-5A) to (2-5G), (2-6A) to (2-6D), (2-7A) to (2-7B), or (2-8A) to (2-8B).

[0100] The terminal groups shown in formulas (2-1A) to (2-1J) below are specific examples of the terminal group shown in formula (2-1). The terminal groups shown in formulas (2-2A) to (2-2M) below are specific examples of the terminal group shown in formula (2-2). The terminal groups shown in formulas (2-3A) to (2-3F) below are specific examples of the terminal group shown in formula (2-3). The terminal groups shown in formulas (2-4A) to (2-4G) below are specific examples of the terminal group shown in formula (2-4). The terminal groups shown in formulas (2-5A) to (2-5G) below are specific examples of the terminal group shown in formula (2-5). The terminal groups shown in formulas (2-6A) to (2-6D) below are specific examples of the terminal group shown in formula (2-6). The terminal groups shown in formulas (2-7A) to (2-7B) below are specific examples of the terminal groups shown in formula (2-7). The terminal groups shown in formulas (2-8A) to (2-8B) below are specific examples of the terminal groups shown in formula (2-8).

[0101]

[0102]

[0103]

[0104]

[0105] In the fluorine-containing ether compound represented by formula (1), R １ and R ４ This means they may be the same or they may be different. １ and R ４ It is preferable that the same. In this case, fluorine-containing ether compounds can be easily and efficiently produced. Note that "R １ and R ４ "The same as R" means １ Atoms and R contained in ４ The atoms contained in and in formula (1) -CH ２ -R ２ [-CH ２ -R ３ -CH ２ -R ２ ] ｘ -CH ２ This means that it is arranged symmetrically with respect to the - sign.

[0106] In the fluorine-containing ether compound represented by formula (1), R １ and R ４ If they are different, R １ and R ４ Each of these may be a terminal group represented independently by formula (2), or R １ and R ４ One of the terminal groups may be represented by formula (2), while the other is a terminal group that does not correspond to formula (2). The terminal group that does not correspond to formula (2) may be any terminal group having 1 to 4 polar groups and 1 to 50 carbon atoms, as described above.

[0107] (Terminal group represented by formula (3)) R １ and R ４ If only one of them is a terminal group represented by formula (2) and the other is a terminal group that does not correspond to formula (2), it is preferable that the terminal group that does not correspond to formula (2) is a terminal group represented by the following formula (3).

[0108] -O-[M] ｍ - [N] ｎ - [P] ｐ - [Q] (3) (In formula (3), m represents an integer from 0 to 3, and n and p each independently represent 0 or 1. Each of the m [M] is independently a divalent linking group represented by the following formula (3M). The n [N] are divalent linking groups represented by the following formula (3N). The p [P] are divalent linking groups represented by the following formula (3P). [Q] is a polar group, a halogeno group, a monovalent aliphatic organic group having 1 to 30 carbon atoms containing at least one ether oxygen atom, an alkyl group having 1 to 30 carbon atoms, an alkenyl group having 2 to 30 carbon atoms, an alkynyl group having 2 to 30 carbon atoms, an organic group having 6 to 30 carbon atoms containing an aromatic ring, or a hydrogen atom. In formula (3), the order of the m [M], n [N], and p [P] may be changed. However, the total number of polar groups included in formula (3) is 1 to 4, and [P] and [Q] do not directly bond.)

[0109] (In equation (3M), m1 and m2 each independently represent integers from 1 to 6, where at least one of m1 and m2 is 1. Equation (3M) is R on the left side.) ２It is coupled to the side.) (Equation (3N) is R on the left side.) ２ (It is joined to the side.) (In equation (3P), p1 represents an integer from 0 to 6. In equation (3P), each of the p1 Rp is independently -CH ２ -, -CF ２ -, -CH(CH ３ )-,-C(CH ３ ) ２ It represents either -. In equation (3P), the left side is R ２ (It will be joined to the side.)

[0110] The terminal group represented by formula (3) is R ２ The methylene group (-CH) is bonded to it. ２ It has an oxygen atom (ether oxygen atom) bonded to it. The terminal group R represented by formula (3) ２ The oxygen atom positioned at the end of the side forms an ether bond (-O-) with the carbon atoms bonded on either side of it. This ether bond imparts appropriate flexibility to the fluorine-containing ether compound represented by formula (1) and increases the affinity between the polar group of the terminal group represented by formula (3) and the protective layer. As a result, the fluorine-containing ether compound represented by formula (1) can form a lubricating layer with excellent adhesion to the protective layer.

[0111] The terminal group represented by formula (3) has 1 to 4 polar groups. Therefore, when m in formula (3) is 3, n is 0. Also, when n in formula (3) is 1, m is 0 to 2. Since the terminal group represented by formula (3) contains one or more polar groups, it is easier to secure a number of polar groups that can participate in interactions with the protective layer and intermolecular interactions. As a result, the fluorine-containing ether compound can form a lubricating layer with even better adhesion to the protective layer and good floating stability. Furthermore, since the terminal group represented by formula (3) contains 4 or fewer polar groups, it is possible to prevent the hydrophilicity of the fluorine-containing ether compound from becoming too high and water from being incorporated into the magnetic recording medium, resulting in a fluorine-containing ether compound that can form a lubricating layer with high corrosion resistance. Preferably, the number of polar groups in the terminal group represented by formula (3) is 2 to 3.

[0112] When the terminal group represented by formula (3) contains the structure of formula (3M), that is, when m in formula (3) is 1 or more, formula (3) is a glycerol structure (-O-CH ２ -CH(OH)-CH ２ The structure has a -O-) and / or a glycerin structure with an extended carbon chain of methylene groups. The glycerin structure and the structure with an extended carbon chain of glycerin have moderate rigidity, which can suppress the interaction of the hydroxyl group contained in the terminal group represented by formula (3) with water. In addition, the ether bond of the glycerin structure and the structure with an extended carbon chain of glycerin imparts moderate mobility to the terminal group represented by formula (3). For this reason, the hydroxyl group contained in the terminal group represented by formula (3) is likely to be involved in interaction with the protective layer. As a result, a lubricating layer can be formed that yields a magnetic recording medium with excellent floating stability and corrosion resistance. For the above reasons, it is preferable that the terminal group represented by formula (3) contains the structure of formula (3M) above.

[0113] If m in formula (3) is 2 or 3, then 2 or 3 structural units [M] (-(CH ２ ) ｍ１ -CH(OH)-(CH ２ ) ｍ２ The combinations of m1 and m2 in (-O-) may be different, or some or all of them may be the same. In formula (3), the m m1s each independently represent an integer from 1 to 6, and the m m2s each independently represent an integer from 1 to 6. In formula (3), one structural unit [M](-(CH ２ ) ｍ１ -CH(OH)-(CH ２ ) ｍ２ In -O-), at least one of m1 and m2 is 1. In this case, it is possible to suppress the decrease in the mobility of the hydroxyl group in the structural unit [M] due to too many carbon atoms in the alkylene group between the carbon atom to which the hydroxyl group is bonded and the ether oxygen atom. It is preferable that both the value of m1 and m2 is 1. Also, if one of m1 and m2 is 1 and the other is 2 to 6, it is preferable that the value of the other is 2 to 4, and most preferably 2.

[0114] When the terminal group represented by formula (3) contains the structure of formula (3N), that is, when n in formula (3) is 1, the terminal group represented by formula (3) is an erythritol structure (-O-CH ２ -CH(OH)-CH(OH)-CH ２ It has -O-). The two hydroxyl groups in the erythritol structure are close together, so steric and electrostatic repulsion between the hydroxyl groups is likely to occur. Also, in the erythritol structure, the carbon atom to which the hydroxyl group is bonded is bonded to the carbon atom to which the hydroxyl group is bonded, so free rotation is easily suppressed. For these reasons, the two hydroxyl groups contained in the erythritol structure are in opposite conformations with respect to the carbon chain in the erythritol structure. As a result, the dipole moments generated by the two hydroxyl groups contained in the erythritol structure cancel each other out, and the surface free energy of the entire fluorine-containing ether compound molecule decreases. Therefore, water is less likely to be incorporated into the lubricating layer containing it, and a lubricating layer can be formed that yields a magnetic recording medium with superior corrosion resistance. For these reasons, it is preferable that the terminal group represented by formula (3) contains the structure of formula (3N) above.

[0115] When the terminal group represented by formula (3) includes the structure of formula (3P), that is, when p in formula (3) is 1, the terminal group represented by formula (3) has a unit that does not contain a polar group sandwiched between two ether oxygen atoms. The unit that does not contain a polar group sandwiched between two ether oxygen atoms reduces the polarity of the entire fluorine-containing ether compound molecule and improves hydrophobicity. Therefore, a lubricating layer that is even less susceptible to water absorption can be formed, and a magnetic recording medium with excellent corrosion resistance can be obtained. For the above reasons, it is preferable that the terminal group represented by formula (3) includes the structure of formula (3P).

[0116] In equation (3P), each of the p Rp independently represents -CH ２ -, -CF ２ -, -CH(CH ３ )-,-C(CH ３ ) ２ Represents either -. Rp is -CH ２ - or -CF ２When Rp is -CH(CH ３ ) - or - C (CH ３ ) ２ When this is the case, the polarity of the terminal group represented by formula (3) can be effectively reduced. This makes it more difficult for water to be incorporated into the lubricating layer, which is preferable.

[0117] Since the value of p1 in formula (3P) is between 0 and 6, it is possible to suppress the problem of the terminal group represented by formula (3) becoming too bulky and reducing the mobility of the polar group included in formula (3). The value of p1 in formula (3P) is preferably between 0 and 4, and more preferably between 0 and 2. When p1 in formula (3P) is between 2 and 6, the Rp values ​​of each p1 may be different, some or all may be the same, and it is preferable that they are all the same, because a uniform lubricating layer can be formed.

[0118] In order to impart the above-mentioned effects to the fluorine-containing ether compound, it is preferable that the terminal group represented by formula (3) contains one or more of the structures represented by formulas (3M), (3N), and (3P). On the other hand, in order to facilitate the production of the fluorine-containing ether compound, it is preferable that the terminal group represented by formula (3) contains up to two of the structures represented by formulas (3M), (3N), and (3P). The values ​​of m, n, and p in formula (3) can be appropriately determined within the range in which the terminal group represented by formula (3) has 1 to 4 polar groups. It is preferable that one or two of m, n, and p in the terminal group represented by formula (3) are 1 or more, and the other one or two are 0.

[0119] In formula (3), [Q] is a polar group, a halogeno group, a monovalent aliphatic organic group having 1 to 30 carbon atoms containing at least one ether oxygen atom, an alkyl group having 1 to 30 carbon atoms, an alkenyl group having 2 to 30 carbon atoms, an alkynyl group having 2 to 30 carbon atoms, an organic group having 6 to 30 carbon atoms containing an aromatic ring, or a hydrogen atom.

[0120] Since the number of carbon atoms in [Q] in formula (3) is 1 or more (2 or more if it is an alkenyl group or alkynyl group), the terminal group represented by formula (3) is highly hydrophobic. Therefore, it is possible to prevent water from being attracted to the lubricating layer, resulting in a fluorine-containing ether compound that can form a lubricating layer that yields a magnetic recording medium with good corrosion resistance. Furthermore, since the number of carbon atoms in [Q] in formula (3) is 30 or less, the terminal group represented by formula (3) has a flexible structure, resulting in good adhesion between the lubricating layer containing the fluorine-containing ether compound and the protective layer. As a result, it is possible to form a lubricating layer that yields a magnetic recording medium with good levitation stability. The number of carbon atoms in [Q] in formula (3) is preferably 1 to 15 (2 to 15 if it is an alkenyl group or alkynyl group), and more preferably 2 to 10.

[0121] In formula (3), [Q] is a monovalent aliphatic organic group having 1 to 30 carbon atoms, which contains at least one of a polar group, a halogeno group, and an ether oxygen atom. In this case, the number of carbon atoms is preferably 1 to 5, more preferably 1 to 4, and even more preferably 1 to 3. The number of carbon atoms in the polar group is included in the number of carbon atoms in the aliphatic organic group. Furthermore, the aliphatic organic group does not contain an aromatic ring.

[0122] In formula (3), if [Q] is a monovalent aliphatic organic group having 1 to 30 carbon atoms containing at least one of a polar group, a halogeno group, or an ether oxygen atom, the polar group is preferably at least one polar group selected from the group consisting of a hydroxyl group, a cyano group, a carboxamide group, and an acetamide group, and most preferably all of them are hydroxyl groups.

[0123] In formula (3), when [Q] is a monovalent aliphatic organic group having 1 to 30 carbon atoms containing at least one of a polar group, a halogeno group, or an ether oxygen atom, the halogeno group is preferably a fluorine atom or a chlorine atom, and most preferably a fluorine atom. This is because it can more effectively reduce the surface free energy of the fluorine-containing ether compound, making it more difficult for water to be incorporated into the lubricating layer.

[0124] If [Q] in formula (3) is a monovalent aliphatic organic group having 1 to 30 carbon atoms that contains at least one polar group, a halogeno group, or an ether oxygen atom, then R ２ The terminal end has a methylene group (CH) with 1 to 6 carbon atoms. ２ Preferably, the aliphatic organic group is one in which a ) is positioned, and specifically, examples include hydroxymethyl group, hydroxyethyl group, hydroxypropyl group, hydroxyethoxyethyl group, cyanomethyl group, cyanoethyl group, cyanopropyl group, cyanoethoxyethyl group, carboxamidemethyl group, carboxamideethyl group, carboxamidepropyl group, carboxamideethoxyethyl group, acetamidomethyl group, acetamidoethyl group, acetamidopropyl group, acetamidoethoxyethyl group, trifluoromethyl group, trifluoroethyl group, pentafluoropropyl group, pentafluoroethyl group, trifluoromethoxyethyl group, methoxyethyl group, methoxypropyl group, allyloxyethyl group, etc.

[0125] In formula (3), if [Q] is an alkyl group having 1 to 30 carbon atoms, the alkyl group may be linear or branched. The number of carbon atoms is preferably 1 to 15, and more preferably 1 to 5. Specifically, examples include methyl groups, ethyl groups, propyl groups, etc.

[0126] When [Q] in formula (3) is an alkenyl group having 2 to 30 carbon atoms, the alkenyl group may be linear or branched. The number of carbon atoms is preferably 2 to 15, and more preferably 2 to 5. When [Q] in formula (3) is an alkenyl group having 2 to 30 carbon atoms, it is preferable that the carbon-carbon double bond contained in the alkenyl group is located at the very end of [Q], and R ２ A methylene group (CH₃) with 0 to 6 carbon atoms is located at the terminal end. ２ It is preferable that the alkenyl group has a carbon atom positioned thereon.Specific examples of alkenyl groups having 2 to 30 carbon atoms include vinyl group, allyl group, 1-propenyl group, butenyl group, etc.

[0127] When [Q] in formula (3) is an alkynyl group having 2 to 30 carbon atoms, the alkynyl group may be linear or branched. The number of carbon atoms is preferably 2 to 15, and more preferably 2 to 5. When [Q] in formula (3) is an alkynyl group having 2 to 30 carbon atoms, it is preferable that the carbon-carbon triple bond contained in the alkynyl group is located at the very end of [Q], and R ２ A methylene group (CH₃) with 0 to 6 carbon atoms is located at the terminal end. ２ It is preferable that the alkynyl group has a carbon atom positioned thereon.Specific examples of alkynyl groups having 2 to 30 carbon atoms include ethynyl groups and propargyl groups.

[0128] In formula (3), if [Q] is an organic group having 6 to 30 carbon atoms that includes an aromatic ring, the organic group having 6 to 30 carbon atoms that includes an aromatic ring may have one or more substituents. Examples of substituents include alkyl groups, alkoxy groups, cyano groups, carboxamide groups, acetamide groups, and halogeno groups.

[0129] In formula (3), if [Q] is an organic group having 6 to 30 carbon atoms and containing an aromatic ring, specific examples include phenyl group, tolyl group, ethylphenyl group, xylyl group, mesityl group, benzyl group, phenethyl group, methoxyphenyl group, ethoxyphenyl group, allyloxyphenyl group, dimethoxyphenyl group, cyanophenyl group, carboxamidephenyl group, acetaminophenyl group, acetamidophenyl group, fluorophenyl group, pentafluorophenyl group, trifluoromethylphenyl group, chlorophenyl group, etc.

[0130] If [Q] is an organic group with 6 to 30 carbon atoms that contains an aromatic ring, then R ２ It is preferable that an aromatic ring is located at the terminal end of the side. Also, if [Q] is an organic group having 6 to 30 carbon atoms that includes an aromatic ring, then the R of the organic group containing the aromatic ring is ２ At the end of the side, there is a methylene group (CH) with 1 to 6 carbon atoms. ２ It is also preferable that the organic group is to which the ) is bonded.

[0131] When [Q] in formula (3) is a hydrogen atom, it bonds with an adjacent oxygen atom to form a hydroxyl group. This hydroxyl group is located at the very end of the fluorine-containing ether compound and readily interacts with the protective layer. As a result, good adhesion is achieved between the lubricating layer containing the fluorine-containing ether compound and the protective layer. Consequently, a lubricating layer can be formed that provides a magnetic recording medium with good levitation stability.

[0132] The terminal group represented by formula (3) is preferably, specifically, a terminal group represented by any of the following formulas (3-1) to (3-10). This is because the production of fluorine-containing ether compounds is easier when the terminal group represented by formula (3) is a terminal group represented by any of the following formulas (3-1) to (3-10). Among these terminal groups, the terminal group represented by formula (3) is preferably a terminal group represented by any of the following formulas (3-1), (3-2), (3-4), or (3-7).

[0133] (In equation (3-1), m01 represents an integer from 1 to 2. Each of the m01 m11 and m21 independently represents an integer from 1 to 6. However, within a single structural unit, at least one of m11 and m21 is 1. q1 represents an integer from 1 to 6. X ３１ q3 represents one of the following: a hydroxyl group, a cyano group, an acetamide group, or a carboxamide group.) (In formula (3-2), m02 represents an integer from 1 to 2. The two m02s m12 and m22 each independently represent an integer from 1 to 6. However, in one structural unit, at least one of m12 and m22 is 1.) (In formula (3-3), m03 represents an integer from 1 to 2. The three m03s m13 and m23 each independently represent an integer from 1 to 6. However, in one structural unit, at least one of m13 and m23 is 1. q3 represents an integer from 0 to 6. X ３３ (where m24 represents an integer from 1 to 6, and q4 represents an integer from 0 to 6.) ３４(where q5 represents one of the following groups: methyl group, vinyl group, ethynyl group, phenyl group, methoxyphenyl group, cyanophenyl group, carboxamidephenyl group, acetaminophenyl group, trifluoromethyl group, or pentafluoroethyl group.) (In formula (3-5), q5 represents an integer from 1 to 6. X ３５ (where q6 represents one of the following: a hydroxyl group, a cyano group, an acetamide group, or a carboxamide group.) (In formula (3-6), q6 represents an integer from 0 to 6. X ３６ (where p17 represents one of the following: methyl group, vinyl group, ethynyl group, phenyl group, methoxyphenyl group, trifluoromethyl group, or pentafluoroethyl group.) (In formula (3-7), p17 represents an integer from 1 to 6. There are p17 Rp ａ , Rp ｂ Each of these independently represents either a hydrogen atom or a methyl group. (In formula (3-8), p18 represents an integer from 1 to 6.)

[0134] (R ３ (Divalent linking group shown by) When x in the fluorine-containing ether compound represented by formula (1) is 1 or 2, the fluorine-containing ether compound has x R ３ It includes R. ３ It is positioned between adjacent PFPE chains via a methylene group. ３ This is a divalent linking group having one to four polar groups, which adheres fluorine-containing ether compounds to the protective layer.

[0135] In equation (1), when x is 2, the two R ３ They may be the same, or they may be different, but it is preferable that they be the same. ３ If the two R's are the same, the coating state on the protective layer of the fluorine-containing ether compound becomes more uniform, and a lubricating layer with better adhesion can be formed. ３ If the same properties are met, fluorine-containing ether compounds can be easily and efficiently manufactured.

[0136] In this specification, when x is 2, "two R ３ "They are the same" means that two R's ３ The atoms contained in are R located at the center of the molecular chain structure. ２ This means that they are arranged symmetrically.

[0137] x R values ​​in equation (1) ３ Each contains one or more polar groups. Therefore, when a lubricating layer is formed on a protective layer using a lubricant containing a fluorine-containing ether compound in which x is 1 or 2, x R ３ A suitable interaction occurs between the protective layer and the fluorine-containing ether compound. Therefore, compared to the fluorine-containing ether compound where x is 1 or 2, the fluorine-containing ether compound where x is 0 can form a lubricating layer that exhibits superior adhesion to the protective layer and high levitation stability, resulting in a magnetic recording medium.

[0138] Also, x R ３ Since each contains four or fewer polar groups, the polarity of the fluorine-containing ether compound with x = 1 or 2 becomes too high, preventing water from being incorporated into the magnetic recording medium. As a result, a fluorine-containing ether compound is obtained that can form a lubricating layer, resulting in a magnetic recording medium with high corrosion resistance. x R ３ The number of polar groups contained is preferably three or less.

[0139] x R ３ The polar groups included in each are the R mentioned above. １ and R ４ Among these, those listed as polar groups included in terminal groups that do not fall under formula (2) can be used. x R ３ The polar groups contained are the R mentioned above. １ and R ４ Of these, for the same reasons as the polar groups included in terminal groups that do not fall under formula (2), it is preferable that each is independently at least one polar group selected from the group consisting of a hydroxyl group, a cyano group, a carboxamide group, and an acetamide group, and more preferably a hydroxyl group.

[0140] x R values ​​in equation (1) ３ The one to four polar groups that each of them possesses may be some or all the same, or they may be different. x R in formula (1) ３ Each preferably contains at least one hydroxyl group, and x R ３It is more preferable that all of the polar groups present are hydroxyl groups, because this results in a more uniform coating state on the protective layer of the fluorine-containing ether compound.

[0141] x R values ​​in equation (1) ３ Each of these is preferably a linking group having 1 to 50 carbon atoms, more preferably a linking group having 3 to 50 carbon atoms, even more preferably a linking group having 3 to 20 carbon atoms, and most preferably a linking group having 4 to 15 carbon atoms. ３ Since the number of carbon atoms in the linking group represented by is 1 or more, the hydrophilicity of the linking group can be reduced. Therefore, R ３ The polar group in the linking group represented by can prevent water from being attracted to the lubricating layer, thereby forming a lubricating layer with good chemical resistance. This makes it possible to form a magnetic recording medium with good corrosion resistance. ３ Since the number of carbon atoms in the linking group represented by is 50 or less, the linking group has a flexible structure, resulting in good adhesion between the lubricating layer containing the fluorine-containing ether compound and the protective layer. As a result, a lubricating layer can be formed that yields a magnetic recording medium with good levitation stability.

[0142] x R values ​​in equation (1) ３ It is preferable that each of these is a divalent linking group with oxygen atoms located at both ends. In this case, R ３ The oxygen atoms positioned at both ends of the divalent linking group shown are R ３ methylene groups (-CH) are located on both sides. ２ -) and an ether bond (-O-) are formed. These ether bonds impart appropriate flexibility to the fluorine-containing ether compound represented by formula (1), R ３ This increases the affinity between the polar group of the divalent linking group shown and the protective layer.

[0143] x R values ​​in equation (1) ３ Preferably, each of these is a divalent linking group represented independently by the following formula (4): -O-[S] ｓ - [T] ｔ - [U] ｕ- (4) (In formula (4), s represents an integer from 0 to 3, and t and u each independently represent 0 or 1. However, s and t cannot be 0 at the same time. Each of the s [S] is independently a divalent linking group represented by the following formula (4S). [T] is a divalent linking group represented by the following formula (4T). [U] is a divalent linking group represented by the following formula (4U). In formula (4), the order of the s [S], t [T], and u [U] may be changed. However, the total number of polar groups included in formula (4) is between 1 and 4.)

[0144] (In formula (4S), s1 and s2 each independently represent integers from 1 to 6, except that at least one of s1 and s2 is 1. The left side of formula (4S) is bonded to the oxygen atom side in formula (4).) (In formula (4T), t1 represents an integer from 0 to 4. The left side of formula (4T) is bonded to the oxygen atom side in formula (4).) (In formula (4U), u1 represents an integer from 0 to 6. Each of the u1 Ru in formula (4U) independently represents -CH ２ -, -CF ２ -, -CH(CH ３ )-,-C(CH ３ ) ２ This represents either of the following. In formula (4U), the left side is bonded to the oxygen atom in formula (4).

[0145] The divalent linking group represented by formula (4) is R ２ The methylene group (-CH) is bonded to it. ２ It has oxygen atoms (ether oxygen atoms) bonded to the (-) at both ends. The oxygen atoms positioned at both ends of the divalent linking group represented by formula (4) form ether bonds (-O-) with the atoms bonded on both sides. This ether bond imparts appropriate flexibility to the fluorine-containing ether compound represented by formula (1) and increases the affinity between the polar group of the divalent linking group represented by formula (4) and the protective layer. As a result, when x in the fluorine-containing ether compound represented by formula (1) is 1 or 2, a lubricating layer with excellent adhesion to the protective layer can be formed.

[0146] Formula (4) represents a divalent linking group having 1 to 4 hydroxyl groups. Since the divalent linking group represented by formula (4) contains one or more hydroxyl groups, it is easier to secure a number of polar groups that can participate in interactions with the protective layer and intermolecular interactions. As a result, it becomes a fluorine-containing ether compound that can form a lubricating layer that provides a magnetic recording medium with even better adhesion to the protective layer and good buoyancy stability. Furthermore, since the divalent linking group represented by formula (4) contains four or fewer hydroxyl groups, it is possible to prevent the hydrophilicity of the fluorine-containing ether compound from becoming too high and water from being incorporated into the magnetic recording medium. Therefore, it becomes a fluorine-containing ether compound that can form a lubricating layer that provides a magnetic recording medium with high corrosion resistance. Preferably, the number of hydroxyl groups in the divalent linking group represented by formula (4) is 2 to 3.

[0147] When the divalent linking group represented by formula (4) contains the structure of formula (4S), that is, when s in formula (4) is 1 or more, formula (4) is a glycerol structure (-O-CH ２ -CH(OH)-CH ２ The structure has a -O-) and / or a glycerin structure with an extended carbon chain of methylene groups. The glycerin structure and the structure with an extended carbon chain of glycerin have appropriate rigidity, so that the hydroxyl groups contained in the divalent linking group represented by formula (4) can be suppressed from interacting with water. In addition, the ether bond of the glycerin structure and / or the structure with an extended carbon chain of glycerin imparts appropriate mobility to the divalent linking group represented by formula (4). For this reason, the hydroxyl groups contained in the divalent linking group represented by formula (4) are more likely to interact with the protective layer. As a result, a lubricating layer can be formed that provides a magnetic recording medium with excellent floating stability and corrosion resistance. For the above reasons, it is preferable that the divalent linking group represented by formula (4) includes the structure of formula (4S).

[0148] If s in formula (4) is 2 or 3, then 2 or 3 structural units [4S] (-(CH ２ ) ｓ１ -CH(OH)-(CH ２ ) ｓ２The combinations of s1 and s2 in (-O-) may be different, or some or all of them may be the same. In formula (4), each of the s s1 independently represents an integer from 1 to 6, and each of the s s2 independently represents an integer from 1 to 6. In formula (4), one structural unit [4S] (-(CH ２ ) ｓ１ -CH(OH)-(CH ２ ) ｓ２ In -O-), at least one of s1 and s2 is 1. In this case, it is possible to suppress the decrease in the mobility of the hydroxyl group in the structural unit [4S] due to too many carbon atoms in the alkylene group between the carbon atom to which the hydroxyl group is bonded and the ether oxygen atom. It is preferable that the values ​​of s1 and s2 in one structural unit [4S] are both 1. Also, if one of s1 and s2 is 1 and the other is 2 to 6, the value is preferably 2 to 4, and most preferably 2.

[0149] When the divalent linking group represented by formula (4) contains the structure of formula (4T), that is, when t in formula (4) is 1, then formula (4) is an erythritol structure (-O-CH ２ -CH(OH)-CH(OH)-CH ２ The structure has a -O-) or an erythritol structure with an extended carbon chain formed by a methylene group. The erythritol structure and the structure with an extended carbon chain formed by the erythritol structure have moderate rigidity. Therefore, the hydroxyl group contained in the divalent linking group represented by formula (4) can be suppressed from interacting with water. In addition, the ether bond of the erythritol structure and the structure with an extended carbon chain formed by the erythritol structure imparts moderate mobility to the divalent linking group represented by formula (4). Therefore, the hydroxyl group contained in the divalent linking group represented by formula (4) is more likely to participate in interaction with the protective layer. As a result, a lubricating layer can be formed that yields a magnetic recording medium with excellent floating stability and corrosion resistance.

[0150] Furthermore, the value of t1 in formula (4T) is between 0 and 4. This prevents the structural unit [4T] from becoming too bulky and reducing the mobility of the hydroxyl group within the structural unit [4T]. For these reasons, it is preferable that the divalent linking group represented by formula (4) includes the structure of formula (4T).

[0151] When the divalent linking group represented by formula (4) includes the structure of formula (4U), that is, when u in formula (4) is 1, the divalent linking group represented by formula (4) has a unit that does not contain a polar group sandwiched between two ether oxygen atoms. The unit that does not contain a polar group sandwiched between two ether oxygen atoms reduces the polarity of the entire fluorine-containing ether compound molecule and improves hydrophobicity. Therefore, a lubricating layer that is even less susceptible to water absorption can be formed, and a magnetic recording medium with excellent corrosion resistance can be obtained. For the above reasons, it is preferable that the divalent linking group represented by formula (4) includes the structure of formula (4U).

[0152] In equation (4U), each of the u Ru values ​​is independently -CH ２ -, -CF ２ -, -CH(CH ３ )-,-C(CH ３ ) ２ Represents either -. Ru is -CH ２ - or -CF ２ When Rp is -CH(CH ３ ) - or - C (CH ３ ) ２ When this is the case, the polarity of the divalent linking group represented by formula (4) can be effectively reduced. As a result, a lubricating layer that is even less susceptible to water absorption can be formed, and a magnetic recording medium with excellent corrosion resistance can be obtained.

[0153] Since the value of u1 in formula (4U) is between 0 and 6, it is possible to suppress the decrease in the mobility of the hydroxyl group of the divalent linking group represented by formula (4) due to the divalent linking group representing formula (4) becoming too bulky. The value of u1 in formula (4U) is preferably between 0 and 4, and more preferably between 0 and 2. When u1 in formula (4U) is between 2 and 6, it is preferable that all the Ru values ​​of u1 are the same, because a uniform lubricating layer can be formed.

[0154] To impart the above-mentioned effects to the fluorine-containing ether compound, the divalent linking group represented by formula (4) includes the structure represented by formula (4S) or formula (4T). On the other hand, to facilitate the production of the fluorine-containing ether compound, it is preferable that the divalent linking group represented by formula (4) includes up to two of the structures represented by formulas (4S), (4T), and (4U). The values ​​of s, t, and u in formula (4) can be appropriately determined within a range where s and t are not simultaneously 0, and the divalent linking group represented by formula (4) has 1 to 4 polar groups. In the divalent linking group represented by formula (4), it is preferable that s and t are not simultaneously 0, and one or two of s, t, and u are 1 or more, while the other one or two are 0.

[0155] The divalent linking group represented by formula (4) is preferably a divalent linking group represented by any of the following formulas (4-1) to (4-9). This is because the production of fluorine-containing ether compounds is easier if the divalent linking group represented by formula (4) is a divalent linking group represented by any of the following formulas (4-1) to (4-9). Among these divalent linking groups, a divalent linking group represented by any of the following formulas (4-1), (4-3), (4-5), or (4-7) is preferred.

[0156] (In equation (4-1), s11 represents an integer from 1 to 6, and s21 represents an integer from 1 to 6, provided that at least one of s11 and s21 is 1.) (In equation (4-2), s02 represents an integer from 2 to 3.) (In equation (4-3), t13 represents an integer from 0 to 4.) (In equation (4-4), s14 represents an integer from 1 to 6.) (In equation (4-5), s15 represents an integer from 1 to 6, and s25 represents an integer from 1 to 6.) (In equation (4-6), s16 represents an integer from 1 to 6, and s26 represents an integer from 1 to 6, provided that at least one of s16 and s26 is 2 or greater.) (In equation (4-7), s17 represents an integer from 1 to 6, and s27 represents an integer from 1 to 6, provided that at least one of s17 and s27 is 2 or greater.) (In equation (4-8), u18 represents an integer from 0 to 6. u18 Ru ａ Ru ｂ Each of these independently represents either a hydrogen atom or a methyl group. (In formula (4-9), u19 represents an integer from 1 to 6.)

[0157] (R ２ In a fluorine-containing ether compound represented by formula (1), R ２ This is a perfluoropolyether chain (PFPE chain). ２ The PFPE chain shown in this embodiment, when a lubricant containing the fluorine-containing ether compound of this embodiment is applied to the protective layer to form a lubricating layer, covers 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 shown is appropriately selected according to the performance requirements of the lubricant containing the fluorine-containing ether compound.

[0158] R ２ Examples of PFPE chains represented by include those consisting of polymers or copolymers of perfluoroalkylene oxides. Examples of perfluoroalkylene oxides include perfluoromethylene oxide, perfluoroethylene oxide, perfluoro-n-propylene oxide, perfluoroisopropylene oxide, and perfluorobutylene oxide.

[0159] If x in equation (1) is 1 or 2, then there are (x+1) R ２ R in equation (1) may be partially or entirely the same, or they may be different. ２ Preferably, each of these is independently a PFPE chain represented by the following formula (5), which is derived, for example, from a polymer or copolymer of perfluoroalkylene oxide.

[0160] - (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 - (CF２ ) ｗ６ - (5) (In equation (5), w2, w3, w4, and w5 represent the average degree of polymerization and each independently represents 0 to 20. However, it is not possible for all of w2, w3, w4, and w5 to be 0 at the same time. w1 and w6 are CF ２ It is an average value representing the number of such units, each independently representing 1 to 3. It is the structural unit in equation (5) (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 order of the elements in (O).

[0161] In formula (5), w2, w3, w4, and w5 represent the average degree of polymerization, each independently representing 0 to 20, preferably 0 to 15, and more preferably 0 to 10. In formula (5), w1 and w6 are CF ２ This is an average value indicating the number of such units, each independently representing 1 to 3. w1 and w6 are determined according to the structure of the structural units located at the ends of the chain structure in the PFPE chain represented by formula (5). (CF 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 structural unit. There are no particular restrictions on the order in which the structural units are arranged in formula (5). Also, there are no particular restrictions on the number of types of structural units in formula (5).

[0162] The perfluoropolyether chain represented by formula (5) is preferably one selected from the PFPE chains represented by the following formulas (5-1) to (5-4). -CF ２ - (OCF ２ CF ２ ) ｈ - (OCF ２ )ｉ -OCF ２ - (5-1) (In formula (5-1), h and i represent the average degree of polymerization, where h is 1 to 20 and i is 0 to 20.) -CF ２ CF ２ - (OCF ２ CF ２ CF ２ ) ｊ -OCF ２ CF ２ - (5-2) (In formula (5-2), j represents the average degree of polymerization and is expressed as 1 to 15.) -CF ２ CF ２ CF ２ - (OCF ２ CF ２ CF ２ CF ２ ) ｋ -OCF ２ CF ２ CF ２ - (5-3) (In formula (5-3), k represents the average degree of polymerization and is expressed as 1 to 10.) - (CF ２ ) ｗ７ -O-(CF ２ CF ２ CF ２ O) ｗ８ - (CF ２ CF ２ O) ｗ９ - (CF ２ ) ｗ１０ - (5-4) (In formula (5-4), w8 and w9 represent the average degree of polymerization and each independently represents 1 to 20. w7 and w10 are CF ２ This represents the average number of units, each independently representing 1 to 2.

[0163] When the PFPE chain represented by formula (5) is selected from any one of the PFPE chains represented by formulas (5-1) to (5-4), a fluorine-containing ether compound is obtained that yields a lubricating layer with good lubricity. Furthermore, the PFPE chains represented by formulas (5-1) to (5-4) have an appropriate ratio of oxygen atoms (ether bond (-O-) number) to carbon atoms. As a result, a fluorine-containing ether compound with appropriate hardness is obtained. Therefore, the fluorine-containing ether compound applied on the protective layer is less likely to aggregate on the protective layer, and a thinner lubricating layer can be formed with sufficient coverage. Moreover, the lubricating layer becomes denser, which further improves the levitation stability and corrosion resistance of the magnetic recording medium, and is therefore preferable.

[0164] In equation (5-1), the structural unit is (OCF ２ CF ２ ) and (OCF ２ There are no particular restrictions on the order of arrangement of ). In equation (5-1), (OCF ２ CF ２ ) number h and (OCF ２ The number i in ) may be the same or different. The PFPE chain represented by formula (5-1) is (OCF ２ CF ２ ) may be a polymer of ). Also, the PFPE chain represented by formula (5-1) is (OCF ２ CF ２ ) and (OCF ２ ) may be any of the following: a random copolymer, a block copolymer, or an alternating copolymer.

[0165] In formulas (5-1) to (5-3), the average degree of polymerization is 1 to 20 for h, 0 to 20 for i, 1 to 15 for j, and 1 to 10 for k, resulting in a fluorine-containing ether compound that yields a lubricating layer with good lubricity. Furthermore, in formulas (5-1) to (5-3), the average degrees of polymerization are 20 or less for h and i, 15 or less for j, and 10 or less for k, so the viscosity of the fluorine-containing ether compound does not become too high, making it easy to apply lubricants containing it, which is preferable. In order to obtain a fluorine-containing ether compound that spreads easily on the protective layer and yields a lubricating layer with a uniform film thickness, it is preferable that h, i, j, and k are each independently 1 to 10, more preferably 1.5 to 8, and even more preferably 2 to 7.

[0166] In equation (5-4), the structural unit is (CF ２ CF ２ CF ２ O) and (CF ２ CF ２ There are no particular restrictions on the order of arrangement with O). In formula (5-4), w8 and w9, which indicate the average degree of polymerization, may be the same or different. Formula (5-4) is a monomer unit (CF ２ CF ２ CF ２ O) and (CF ２ CF ２ It may also contain any of the following: a random copolymer, a block copolymer, or an alternating copolymer consisting of O).

[0167] In formula (5-4), w8 and w9, which represent the average degree of polymerization, are each independently 1 to 20, preferably 1 to 15, and more preferably 1 to 10. In formula (5-4), w7 and w10 are CF ２ These are average values ​​indicating the number of such units, each independently representing 1 to 2. w7 and w10 are determined according to the structure of the structural units located at the ends of the chain structure in the PFPE chain represented by formula (5-4).

[0168] The fluorine-containing ether compound represented by formula (1) is preferably one of the compounds represented by the following formulas (AA) to (AZ), (BA) to (BG), or (CA) to (CE). When the compound represented by formula (1) is one of the compounds represented by the following formulas (AA) to (AZ), (BA) to (BG), or (CA) to (CE), the raw materials are readily available, and a lubricating layer can be formed that provides a magnetic recording medium with even better buoyancy stability and corrosion resistance, even with a thin thickness.

[0169] In the compounds represented by the following formulas (AA) to (AZ), (BA) to (BG), and (CA) to (CE), Rf represents the PFPE chain. １ , Rf ２ , Rf ３ The structures are as follows. That is, in the compounds represented by the following formulas (BA) and (BB), Rf １ This is a PFPE chain represented by the above formula (5-1). In the compounds represented by the following formulas (AA) to (AZ), (BD) to (BG), and (CA) to (CE), Rf ２ This is a PFPE chain represented by the above formula (5-2). In the compound represented by the following formula (BC), Rf ３ This is the PFPE chain represented by the above formula (5-3). Note that Rf represents the PFPE chain in formulas (AA) to (AZ), (BA) to (BG), and (CA) to (CE). １ h and i, Rf ２ j, Rf ３ In this case, k is a value that indicates the average degree of polymerization, and therefore is not necessarily an integer.

[0170]

[0171] Compounds represented by the following formulas (AA) to (AZ) and (BA) to (BG) have x = 0 in formula (1). Compounds represented by the following formulas (AA) to (AW), (AZ), and (BA) to (BC) have R １ and R ４ The compounds represented by formulas (AA) to (AZ) and (BA) to (BC) are R １ and R ４ However, it is a terminal group represented by any of the above formulas (2-1) to (2-8).

[0172] Compounds represented by the following formulas (BD) to (BG) are R １ and R ４ The two are different, with one being a terminal group represented by formula (2-1) or (2-2) above, and the other being a terminal group represented by any of formulas (3-1) to (3-10) above.

[0173] The compounds represented by the following formulas (CA) to (CD) are those in which x in formula (1) is 2, and R １ and R ４ The compounds represented by formulas (CA) to (CD) are R １ and R ４ The terminal group is represented by the above formula (2-1) or (2-2). The compound represented by formula (CA) is R ３ The linking group represented by the above formula (4-7), the compound represented by formula (CB), is R ３ The linking group is represented by the above formula (4-3), and the compound represented by formula (CC) is R ３ The linking group is represented by the above formula (4-5), and the compound represented by formula (CD) is R ３ This is the linking group represented by the above formula (4-1).

[0174] The compound represented by the following formula (CE) is one in which x in formula (1) is 3. １ and R ４ These are the same and are terminal groups represented by the above formula (2-1). Two R ３ This is the linking group represented by the above formula (4-1).

[0175] (Rf in equation (AA)) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. ) (Rf in equation (AB) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. ) (Rf in equation (AC) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. ) (Rf in equation (AD) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. ) (Rf in equation (AE) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. ) (Rf in equation (AF) ２In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. ) (Rf in formula (AG) ２ In this case, j represents the average degree of polymerization and is expressed as 1 to 15.

[0176] (Rf in equation (AH)) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. ) (Rf in equation (AI) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. ) (Rf in equation (AJ) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. ) (Rf in equation (AK) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. ) (Rf in equation (AL) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. ) (Rf in equation (AM) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. ) (Rf in equation (AN) ２ In this case, j represents the average degree of polymerization and is expressed as 1 to 15.

[0177] (Rf in equation (AO)) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. ) (Rf in equation (AP) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. ) (Rf in equation (AQ) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. (Rf in equation (AR)) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. (Rf in equation (AS)) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. ) (Rf in equation (AT) ２ In this case, j represents the average degree of polymerization and is expressed as 1 to 15.

[0178] (Rf in equation (AU)) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. ) (Rf in equation (AV) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. ) (Rf in equation (AW) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. (Rf in equation (AX)) ２In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. ) (Rf in equation (AY) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. ) (Rf in equation (AZ) ２ In this case, j represents the average degree of polymerization and is expressed as 1 to 15.

[0179] (Rf in formula (BA)) １ In this equation, h and i represent the average degree of polymerization, where h is 1 to 20 and i is 0 to 20.) (Rf in equation (BB) １ In this equation, h and i represent the average degree of polymerization, where h is 1 to 20 and i is 0 to 20. ) (Rf in equation (BC) ３ In this equation, k represents the average degree of polymerization and is expressed as 1 to 10. ) (Rf in formula (BD) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. ) (Rf in equation (BE) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. ) (Rf in formula (BF) ２ In this equation, j represents the average degree of polymerization and is expressed as 1 to 15. ) (Rf in formula (BG) ２ In this case, j represents the average degree of polymerization and is expressed as 1 to 15.

[0180] (The two Rf in equation (CA) ２ In this, j represents the average degree of polymerization and is expressed as 1 to 15. Two Rf ２ The values ​​of j in this equation may be the same or different.) (The two Rf in equation (CB) ２ In this, j represents the average degree of polymerization and is expressed as 1 to 15. Two Rf ２ In this equation, j may be the same or different.) (The two Rf in equation (CC) ２ In this, j represents the average degree of polymerization and is expressed as 1 to 15. Two Rf ２ In this equation, j may be the same or different. ) (The two Rf in equation (CD) ２ In this, j represents the average degree of polymerization and is expressed as 1 to 15. Two Rf ２ In this equation, j may be the same or different.) (The three Rf in equation (CE) ２In this, j represents the average degree of polymerization and is expressed as 1 to 15. Three Rf ２ In this case, j may be different in each instance, or some or all of them may be the same.

[0181] The fluorine-containing ether compound of this embodiment preferably has a number average molecular weight (Mn) in the range of 500 to 10000, more preferably in the range of 700 to 5000, and particularly preferably in the range of 900 to 2500. When the number average molecular weight is 500 or more, the lubricating layer made of the lubricant containing the fluorine-containing ether compound of this embodiment will have excellent heat resistance. The number average molecular weight of the fluorine-containing ether compound is preferably 700 or more, and particularly preferably 900 or more. Furthermore, when the number average molecular weight is 10000 or less, the viscosity of the fluorine-containing ether compound becomes appropriate, and a thin lubricating layer can be easily formed by applying a lubricant containing it. The number average molecular weight of the fluorine-containing ether compound is preferably 5000 or less, and particularly preferably 2500 or less, as this results in a viscosity that is easy to handle when applied to a lubricant.

[0182] The number-average molecular weight (Mn) of fluorine-containing ether compounds was determined using the AVANCEIII400 from Bruker BioSpin. １ H-NMR and １９ These are values ​​measured by F-NMR. Specifically, １９ The number of structural units in the PFPE chain is calculated from the integral values ​​measured by F-NMR, and the number-average molecular weight of the PFPE chain is determined. The number-average molecular weight (Mn) of the fluorine-containing ether compound is calculated by adding the molecular weight of the non-PFPE chain portion to the obtained number-average molecular weight of the PFPE chain. In NMR (nuclear magnetic resonance) measurements, the sample is diluted in hexafluorobenzene / d-acetone (4 / 1v / v) solvent before measurement. １９ The standard for F-NMR chemical shift is a peak of hexafluorobenzene at -164.7 ppm. １ The standard for the H-NMR chemical shift is a peak of 2.2 ppm for acetone.

[0183] In this embodiment, it is preferable to fractionate the fluorine-containing ether compound by a suitable molecular weight method to achieve a molecular weight dispersion (weight-average molecular weight (Mw) / number-average molecular weight (Mn) ratio) of 1.3 or less. In this embodiment, there are no particular limitations on the molecular weight fractionation method, but for example, molecular weight fractionation by silica gel column chromatography, gel permeation chromatography (GPC), or molecular weight fractionation by supercritical fluid extraction can be used.

[0184] "Manufacturing Method" The manufacturing method for the fluorine-containing ether compound of this embodiment is not particularly limited and can be manufactured using conventionally known manufacturing methods. The fluorine-containing ether compound of this embodiment can be manufactured, for example, using the method shown below.

[0185] [First manufacturing method (where x is 0, R １ and R ４ (If the two are the same) In equation (1), x is 0 and R １ and R ４ To produce a compound that is the same as, first, R in formula (1) ２ The perfluoropolyether chain corresponding to each has a hydroxymethyl group (-CH) at both ends. ２ Prepare a fluorine-based compound with an OH group.

[0186] Next, the hydroxyl groups of the hydroxymethyl groups located at both ends of the fluorine compound, and R in formula (1) １ The corresponding base (=R) ４ The epoxy group of an epoxy compound having a corresponding group is reacted with the epoxy group of the epoxy compound. This results in R ２ R at both ends of the corresponding perfluoropolyether chain １ The corresponding base (=R) ４ A compound having the corresponding group is obtained. The ratio of the reaction substrates is preferably such that the hydroxyl group and epoxy group react equimolarly, but the ratio can be finely adjusted according to the characteristics of the reaction substrates.

[0187] R in equation (1) １ The corresponding base (=R) ４An epoxy compound having the corresponding group is an epoxy compound corresponding to the terminal group represented by formula (2). Examples of epoxy compounds corresponding to the terminal group represented by formula (2) include the compounds represented by the following formulas (6-1) to (6-24). In the compounds represented by formulas (6-1) to (6-24), THP represents a tetrahydropyranyl group.

[0188]

[0189]

[0190] Fluorine compounds and R in formula (1) １ (=R ４ When reacting an epoxy compound having a group corresponding to ) with the fluorine compound, the hydroxyl group of the epoxy compound may be protected with an appropriate protecting group before reacting with the fluorine compound.

[0191] Epoxy compounds can be produced, for example, by reacting an alcohol compound in which the hydroxyl groups not involved in the reaction may be appropriately protected with a halogen compound having an epoxy group. Specifically, for example, the epoxy compound represented by formula (6-7) can be produced by the method shown in formula (7-1) below. That is, it can be produced by reacting an alcohol compound represented by formula (7-3) in which the hydroxyl groups not involved in the reaction are appropriately protected with an epibromohydrin represented by formula (8-1). In the compound represented by formula (7-1), THP represents a tetrahydropyranyl group.

[0192]

[0193] Furthermore, epoxy compounds may also be produced by oxidizing a vinyl group of a compound having a vinyl group located at its terminus and a hydroxyl group which may be appropriately protected, by reacting it with m-chloroperbenzoic acid (mCPBA). Specifically, for example, the epoxy compound represented by formula (6-1) can be produced by the method shown in formula (7-2) below. That is, it can be produced by reacting a vinyl group of a compound represented by formula (7-4), which has a vinyl group located at its terminus and a hydroxyl group which is appropriately protected, with m-chloroperbenzoic acid (mCPBA). In the compound represented by formula (7-2), THP represents a tetrahydropyranyl group.

[0194]

[0195] R in equation (1) １ (=R ４ An epoxy compound having the corresponding group may be purchased commercially and used. By performing the above steps, x in formula (1) is 0 and R １ and R ４ A compound identical to the one described is obtained.

[0196] [Second manufacturing method (where x is 0, R １ and R ４ (If the above are different) In equation (1), x is 0 and R １ and R ４ To produce a compound different from the first, first, as in the first production method, R in formula (1) ２ The perfluoropolyether chain corresponding to each has a hydroxymethyl group (-CH) at both ends. ２ Prepare a fluorine-based compound with an OH group.

[0197] Next, the hydroxyl group of the hydroxymethyl group located at one end of the fluorine compound, and R in formula (1) １ The epoxy group of an epoxy compound having the corresponding group is reacted with it. This results in R ２ At one end of the corresponding perfluoropolyether chain, R １Intermediate compound 1 having the corresponding group is obtained (first reaction). The ratio of reaction substrates is preferably such that 1 / 2 mole of hydroxyl groups and 1 mole of epoxy groups react, but the ratio can be finely adjusted according to the characteristics of the reaction substrates.

[0198] Next, the above intermediate compound 1 and R in formula (1) ４ The epoxy compound having the corresponding group is reacted with it (second reaction). １ and R ４ If the two are different, and one is a terminal group represented by formula (2) and the other is a terminal group that does not correspond to formula (2), then as the epoxy compound corresponding to the terminal group represented by formula (2), the compounds represented by formulas (6-1) to (6-24) described above can be used. Furthermore, as the epoxy compound corresponding to the terminal group that does not correspond to formula (2), for example, the epoxy compounds represented by the following formulas (6-25) to (6-28) can be used. In the compounds represented by formulas (6-26) to (6-28), THP represents a tetrahydropyranyl group.

[0199]

[0200] By performing the above steps, x in equation (1) is 0, and R １ and R ４ Different compounds are obtained.

[0201] [Third manufacturing method (where x is 1, R １ and R ４ and are the same, and the two R ２ (If the same) R in equation (1) ２ The perfluoropolyether chain corresponding to each has a hydroxymethyl group (-CH) at both ends. ２ Prepare a fluorine-based compound with an OH group.

[0202] Next, the hydroxyl group of the hydroxymethyl group located at one end of the fluorine compound, and R in formula (1) １ The corresponding base (=R) ４ The epoxy compound having the corresponding group is reacted with the epoxy compound. This produces R ２ At one end of the corresponding perfluoropolyether chain, R１ The corresponding base (=R) ４ Intermediate compound 1 having a group corresponding to (first reaction) is obtained. When reacting the above fluorine compound with the above epoxy compound, the hydroxyl group of the epoxy compound may be protected with an appropriate protecting group before reacting with the above fluorine compound.

[0203] Subsequently, the hydroxyl group of the hydroxymethyl group located at one end of the intermediate compound 1 produced in the first reaction described above, and R in formula (1) ３ A compound having an epoxy group at one end of the corresponding portion and a halogen atom bonded to the other end, or R in formula (1) ３ The compound having epoxy groups at both ends of the corresponding portion is reacted with it (second reaction).

[0204] R in equation (1) ３ As a compound having an epoxy group at one end of the corresponding portion and a halogen atom bonded to the other end, for example, epibromohydrin represented by the following formula (8-1) can be used. ３ As compounds having epoxy groups at both ends of the corresponding portion, for example, compounds represented by the following formulas (8-2) to (8-5) can be used. In the compounds represented by the following formulas (8-2) and (8-4), THP represents a tetrahydropyranyl group.

[0205]

[0206] R ３ A compound having epoxy groups at both ends of the corresponding portion can be produced, for example, by the method shown below. That is, R ３ It can be produced by reacting a diol corresponding to a part of the linking group represented by with twice the molar amount of epibromohydrin. Specifically, for example, when producing the compound represented by formula (8-5), it can be produced by reacting 2,2,3,3-tetrafluoro-1,4-butanediol represented by formula (9-3) with twice the molar amount of epibromohydrin represented by formula (8-1), as shown in formula (9-1) below.

[0207]

[0208] R ３ A compound having epoxy groups at both ends of the corresponding portion may be produced by the following method: R ３ A halogen compound having an epoxy group corresponding to a part of the linking group represented by R ３ An addition reaction is carried out with an alcohol having an alkenyl group corresponding to a portion of the linking group represented by . In this case, twice the molar amount of the alcohol having an alkenyl group as the halogen compound is reacted with the halogen compound. Subsequently, the resulting compound can be produced by oxidizing it with m-chloroperbenzoic acid (mCPBA). Before oxidizing the compound obtained by the addition reaction with m-chloroperbenzoic acid (mCPBA), the hydroxyl groups generated by the addition reaction may be protected by known methods.

[0209] Specifically, for example, the compound represented by formula (8-2) can be produced using the method shown in formula (9-2) below. First, an addition reaction is carried out between epibromohydrin represented by formula (8-1) and 3-buten-1-ol represented by formula (9-4) in an amount twice the molar amount of the epibromohydrin. Subsequently, the hydroxyl group produced by the addition reaction is protected with dihydropyran (DHP) and oxidized by reaction with m-chloroperbenzoic acid (mCPBA). In formula (9-2) below, THP represents a tetrahydropyranyl group.

[0210]

[0211] If the compound obtained after the second reaction described above has a hydroxyl group protected with a protecting group, a deprotection reaction is carried out using a known method. By performing the above steps, x in formula (1) is 1, and R １ and R ４ and are the same, and the two R ２ It is possible to produce fluorine-containing ether compounds that are the same.

[0212] [Fourth manufacturing method (where x is 1, R １ and R ４ and / or two R ２ (If different) First, R １ R on the side２ A fluorine-based compound in which hydroxymethyl groups are positioned at both ends of the corresponding perfluoropolyether chain, and R １ An epoxy compound having the corresponding group is reacted to obtain intermediate compound 1a (first reaction).

[0213] Next, R ４ R on the side ２ A fluorine-based compound in which hydroxymethyl groups are positioned at both ends of the corresponding perfluoropolyether chain, and R ４ An epoxy compound having the corresponding group is reacted to obtain intermediate compound 1b (second reaction). In the fourth production method, R １ and R ４ These are the same (that is, R １ and R ４ When producing a fluorine-containing ether compound (where R is the same terminal group represented by formula (2)), ４ As an epoxy compound having a corresponding group, R is an epoxy compound corresponding to the terminal group represented by formula (2). １ The same epoxy compound that has the corresponding group is used.

[0214] In the fourth manufacturing method, R １ and R ４ Unlike, R １ and R ４ When producing a fluorine-containing ether compound in which all of the terminal groups are represented by formula (2), R ４ As an epoxy compound having a corresponding group, for example, an epoxy compound corresponding to the terminal group represented by formula (2) above, R １ A different compound is used from the epoxy compound having the corresponding group.

[0215] Furthermore, in the fourth manufacturing method, R １ and R ４ Unlike, R １ is a terminal group represented by formula (2), and R ４ (R) is a terminal group that does not correspond to formula (2). １ and R ４When producing a fluorine-containing ether compound (where only one of the terminal groups is represented by formula (2)), R ４ As an epoxy compound having the corresponding group, an epoxy compound corresponding to a terminal group that does not fall under formula (2) above is used.

[0216] Next, the intermediate compound 1a obtained in the first reaction and the above-mentioned R ３ A compound having an epoxy group at one end of the corresponding portion and a halogen atom bonded to the other end, or R ３ The compound having epoxy groups at both ends of the corresponding portion is reacted with it. This results in R １ R on the side ２ At one end of the corresponding perfluoropolyether chain, R １ It has a corresponding group, and at the other end, R ３ An intermediate compound 2a having the corresponding epoxy group is produced (third reaction).

[0217] Furthermore, in the third reaction, R ３ A compound having an epoxy group at one end of the corresponding portion and a halogen atom bonded to the other end, or R ３ Instead of a compound having epoxy groups at both ends of the corresponding portion, R in formula (1) ３ A compound having an epoxy group at one end of the corresponding portion and an alkenyl group at the other end may be used, and the double bond of the resulting compound may be oxidized to produce an intermediate compound 2a having an epoxy group.

[0218] Next, the intermediate compound 1b obtained in the second reaction is reacted with the intermediate compound 2a obtained in the third reaction (fourth reaction). If the compound obtained after the fourth reaction has a hydroxyl group protected with a protecting group, a deprotection reaction is carried out using a known method. By performing the above steps, x in formula (1) is 1, and R １ and R ４ and / or two R ２ This allows for the production of different fluorine-containing ether compounds.

[0219] [Fifth manufacturing method (where x is 2, R １ and R ４The two R's are the same. ３ The same, R １ R on the side ２ and R ４ R on the side ２ (If the same) R in equation (1) １ R on the side ２ (=R ４ R on the side ２ ) has hydroxymethyl groups (-CH) at both ends of the perfluoropolyether chain corresponding to ). ２ Prepare a fluorine-based compound with an OH group.

[0220] Next, the hydroxyl group of the hydroxymethyl group located at one end of the fluorine compound, and R in formula (1) １ The corresponding base (=R) ４ The epoxy compound having the corresponding group is reacted with the epoxy compound. This produces R １ R on the side ２ (=R ４ R on the side ２ At one end of the perfluoropolyether chain corresponding to ), １ The corresponding base (=R) ４ Intermediate compound 1 having a corresponding group is obtained (first reaction).

[0221] Next, R in the center of the molecule in equation (1) ２ The perfluoropolyether chain corresponding to each has a hydroxymethyl group (-CH) at both ends. ２ Prepare a fluorine-based compound in which OH) is positioned. Next, the hydroxyl groups of the hydroxymethyl groups positioned at both ends of the fluorine-based compound and the R mentioned above. ３ A compound having an epoxy group at one end of the corresponding portion and a halogen atom bonded to the other end, or R ３ The compound having epoxy groups at both ends of the corresponding portion is reacted with it. This causes the R in the center of the molecule to react. ２ At both ends of the corresponding perfluoropolyether chain, R ３ An intermediate compound 3a having the corresponding epoxy group is obtained (second reaction).

[0222] Furthermore, in the second reaction, R ３A compound having an epoxy group at one end of the corresponding portion and a halogen atom bonded to the other end, or R ３ Instead of a compound having epoxy groups at both ends of the corresponding portion, R in formula (1) ３ A compound having an epoxy group at one end of the corresponding portion and an alkenyl group at the other end may be used, and the double bond of the resulting compound may be oxidized to produce an intermediate compound 3a having epoxy groups at both ends.

[0223] Subsequently, the hydroxyl group of the hydroxymethyl group located at one end of the intermediate compound 1 obtained in the first reaction is reacted with the epoxy groups located at both ends of the intermediate compound 3a (third reaction). If the compound obtained after the third reaction has a hydroxyl group protected with a protecting group, a deprotection reaction is carried out using a known method. By performing the above steps, x in formula (1) is 2, and R １ and R ４ The two R's are the same. ３ The same, R １ R on the side ２ and R ４ R on the side ２ It is possible to produce fluorine-containing ether compounds that are the same.

[0224] [Sixth manufacturing method (where x is 2, R １ R on the side ３ and R ４ R on the side ３ and are the same, R １ and R ４ These are different, and / or, R １ R on the side ２ and R ４ R on the side ２ (If different) In the first reaction of the fifth manufacturing method, instead of producing intermediate compound 1, the first and second reactions of the fourth manufacturing method are carried out to produce intermediate compound 1a and intermediate compound 1b. Then, intermediate compound 3a is obtained in the same manner as the second reaction of the fifth manufacturing method. Then, intermediate compound 1a and intermediate compound 1b are sequentially reacted with the epoxy groups located at both ends of intermediate compound 3a, respectively.

[0225] If the compound obtained after the above steps has a hydroxyl group protected with a protecting group, a deprotection reaction is carried out using a known method. By performing the above steps, x in formula (1) is 2, and R １ R on the side ３ and R ４ R on the side ３ and are the same, R １ and R ４ These are different, and / or, R １ R on the side ２ and R ４ R on the side ２ This allows for the production of different fluorine-containing ether compounds.

[0226] [Seventh manufacturing method (where x is 2, R １ R on the side ３ and R ４ R on the side ３ Unlike, R １ and R ４ and are the same, R １ R on the side ２ and R ４ R on the side ２ (If the same) In the second reaction of the fifth manufacturing method, the R in the center of the molecule in formula (1) ２ The perfluoropolyether chain corresponding to each has a hydroxymethyl group (-CH) at both ends. ２ A fluorine-based compound in which an OH group is positioned, and the above-mentioned R ３ A compound having an epoxy group at one end of the corresponding portion and a halogen atom bonded to the other end, or R ３ Selected from compounds having epoxy groups at both ends of the corresponding portion, R １ R on the side ３ It is reacted with one of the compounds having the corresponding part.

[0227] Then, the obtained compound and the above-mentioned R ３ A compound having an epoxy group at one end of the corresponding portion and a halogen atom bonded to the other end, or R ３ Selected from compounds having epoxy groups at both ends of the corresponding portion, R ４ R on the side ３The intermediate compound 3b is obtained by reacting it with one of the compounds having the corresponding portion. Then, the third reaction is carried out in the same manner as in the fifth manufacturing method, except that intermediate compound 3b is used instead of intermediate compound 3a.

[0228] If the compound obtained after the third reaction described above has a hydroxyl group protected with a protecting group, a deprotection reaction is carried out using a known method. By performing the above steps, x in formula (1) is 2, and R １ R on the side ３ and R ４ R on the side ３ Unlike, R １ and R ４ and are the same, R １ R on the side ２ and R ４ R on the side ２ It is possible to produce fluorine-containing ether compounds that are the same.

[0229] In equation (1), x is 2, and R is in the center of the numerator. ２ The corresponding perfluoropolyether chain is R １ R on the side ２ and / or R ４ R on the side ２ The fluorine-containing ether compounds that are the same as, and the different fluorine-containing ether compounds, are used in the fifth to seventh manufacturing methods described above, with the R at the center of the molecule. ２ It can be produced by appropriately selecting the type of fluorine-based compound having a corresponding perfluoropolyether chain.

[0230] Therefore, in the fifth to seventh manufacturing methods for producing a fluorine-containing ether compound in formula (1) where x is 2, the central R of the molecule is used. ２ Fluorine-based compounds having a perfluoropolyether chain corresponding to other R ２ The fluorinated compound having the corresponding perfluoropolyether chain may be the same as or different from the fluorinated compound.

[0231] [Lubricant for Magnetic Recording Media] The lubricant for magnetic recording media of this embodiment contains a fluorine-containing ether compound represented by formula (1) above. The lubricant of this embodiment can be mixed with known materials used as lubricant materials as needed, as long as the properties caused by the inclusion of the fluorine-containing ether compound represented by formula (1) above are not impaired.

[0232] Specific examples of known materials include, for example, FOMBLIN® ZDIAC, FOMBLIN ZDEAL, FOMBLIN AM-2001 (all manufactured by Solvay Solexis), and Moresco A20H (manufactured by Moresco). The known materials used in combination with the lubricant of this embodiment preferably have a number average molecular weight of 1,000 to 10,000.

[0233] If the lubricant of this embodiment contains other materials of the fluorine-containing ether compound represented by formula (1) above, it is preferable that the content of the fluorine-containing ether compound represented by formula (1) in the lubricant of this embodiment be 70% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

[0234] The lubricant of this embodiment contains a fluorine-containing ether compound represented by the above formula (1), and can form a lubricating layer that provides a magnetic recording medium with excellent buoyancy stability and corrosion resistance.

[0235] [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 underlay layers may be provided between the substrate and the magnetic layer as needed. In addition, at least one of an adhesive layer and a soft magnetic layer may be provided between the underlay layer and the substrate.

[0236] Figure 1 is a schematic cross-sectional view showing one embodiment of the magnetic recording medium of the present invention. The magnetic recording medium 10 of this embodiment has a structure in which an adhesion layer 12, a soft magnetic layer 13, a first underlayment 14, a second underlayment 15, a magnetic layer 16, a protective layer 17, and a lubricating layer 18 are sequentially provided on a substrate 11. For details of the substrate 11, adhesion layer 12, soft magnetic layer 13, first underlayment 14, second underlayment 15, magnetic layer 16, and protective layer 17, please refer to paragraphs

[0224] to

[0249] of Patent Document 8.

[0237] "Lubricating layer" The lubricating layer 18 prevents contamination of the magnetic recording medium 10. The lubricating layer 18 also reduces the frictional force of the magnetic head of the magnetic recording and playback device sliding on the magnetic recording medium 10, thereby improving the durability of the magnetic recording medium 10. As shown in Figure 1, the lubricating layer 18 is formed in contact with the protective layer 17. The lubricating layer 18 is formed by applying the lubricant for magnetic recording media of the above embodiment onto the protective layer 17. Therefore, the lubricating layer 18 contains the above-mentioned fluorine-containing ether compound.

[0238] When the protective layer 17 located beneath the lubricating layer 18 is a carbon-based protective layer, the lubricating layer 18 is bonded to the protective layer 17 with particularly high bonding force. 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 rate, and contamination of the surface of the magnetic recording medium 10 can be effectively prevented.

[0239] 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 1.2 nm (12 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 islands or a mesh-like structure. Therefore, the surface of the protective layer 17 can be covered with the lubricating layer 18 with a high coverage rate. Furthermore, by making the average thickness of the lubricating layer 18 2.0 nm or less, the lubricating layer 18 can be sufficiently thinned, and the amount of levitation of the magnetic head can be sufficiently reduced.

[0240] "Method for forming a lubricating layer" As a method for forming the lubricating layer 18, for example, a magnetic recording medium in the process of being manufactured is prepared in which each layer up to the protective layer 17 is formed on the substrate 11, a lubricating layer forming solution is applied to the protective layer 17, and then dried.

[0241] The lubricating layer-forming solution is obtained by dispersing and dissolving the lubricant for magnetic recording media of the above embodiment in a solvent as needed, and adjusting the viscosity and concentration to suit the application method. Examples of solvents used in the lubricating layer-forming solution include fluorine-based solvents such as Bartrell® XF (trade name, manufactured by Mitsui DuPont Fluorochemicals) and Asahi Clean® AE-3000 (trade name, manufactured by AGC).

[0242] The method for applying the lubricating layer-forming solution is not particularly limited, but examples include the spin coating method, spray method, paper coating method, and dip method. When using the dip method, for example, the method shown below can be used. First, the substrate 11, on which each layer up to the protective layer 17 has been formed, is immersed in the lubricating layer-forming solution placed in the immersion tank of the dip coating apparatus. Next, the substrate 11 is pulled out of the immersion tank at a predetermined speed. This coats the surface of the protective layer 17 of the substrate 11 with the lubricating layer-forming solution. By using the dip method, the lubricating layer-forming solution can be uniformly applied to the surface of the protective layer 17, and a lubricating layer 18 can be formed on the protective layer 17 with a uniform film thickness.

[0243] In this embodiment, it is preferable to heat-treat the substrate 11 on which the lubricating layer 18 is formed. By heat-treating, the adhesion between the lubricating layer 18 and the protective layer 17 is improved, and the adhesion between the lubricating layer 18 and the protective layer 17 is improved. The heat treatment temperature is preferably 100°C to 180°C, and more preferably 100°C to 160°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 can be sufficiently obtained. Furthermore, by setting the heat treatment temperature to 180°C or lower, thermal decomposition of the lubricating layer 18 due to heat treatment can be prevented. The heat treatment time can be appropriately adjusted according to the heat treatment temperature, and is preferably 10 minutes to 120 minutes.

[0244] In this embodiment, in order to further improve the adhesion of the lubricating layer 18 to the protective layer 17, the lubricating layer 18 may be irradiated with ultraviolet (UV) light before or after heat treatment.

[0245] 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 provided on a substrate 11. In the magnetic recording medium 10 of this embodiment, the lubricating layer 18 containing the above-mentioned fluorine-containing ether compound is formed in contact with the protective layer 17. Even with a thin film thickness, this lubricating layer 18 can form a magnetic recording medium 10 that provides good levitation stability and corrosion resistance. Therefore, the magnetic recording medium 10 of this embodiment is excellent in reliability and durability. As a result, the magnetic recording medium 10 of this embodiment can contribute to reducing magnetic spacing, allowing for a low magnetic head levitation amount (for example, 10 nm or less), and can operate stably over a long period of time even in harsh environments associated with the diversification of applications. Therefore, the magnetic recording medium 10 of this embodiment is particularly suitable as a magnetic disk mounted in a LUL (Load Unload) type magnetic disk drive.

[0246] The present invention will be described in more detail below with reference to examples and comparative examples. However, the present invention is not limited to the following examples.

[0247] [Example 1] The compound represented by the above formula (AA) was obtained by the following method. Under a nitrogen gas atmosphere, HOCH4 was added to a 100 mL round-bottom flask. ２ CF ２ CF ２ O(CF) ２ CF ２ CF ２ O) ｊ CF ２ CF ２ CH ２ 5 g (5.3 mmol) of the compound represented by OH (where j, representing the average degree of polymerization, is 4.5) (number average molecular weight 950, molecular weight distribution 1.1), 1.8 g (10.5 mmol) of the compound represented by the above formula (6-1), and 5 mL of t-butanol were charged together and stirred at room temperature until homogeneous to form a mixture. 0.23 g of potassium tert-butoxide was added to this mixture and the mixture was stirred at 70°C for 16 hours to allow it to react.

[0248] The compound represented by formula (6-1) was synthesized by the following method. First, the hydroxyl group of 1-buten-3-ol was protected with dihydropyran (DHP). Subsequently, the carbon-carbon double bond was oxidized with m-chloroperbenzoic acid (mCPBA) to form an epoxy ring.

[0249] The reaction mixture obtained after the reaction was allowed to return to room temperature, and 10 g of 10% hydrogen chloride / methanol solution (hydrogen chloride-methanol reagent (5-10%) manufactured by Tokyo Chemical Industry Co., Ltd.) was added and stirred at room temperature for 4 hours. Then, the reaction mixture was gradually transferred to a separatory funnel containing 25 mL of saturated sodium bicarbonate solution and extracted twice with 50 mL of ethyl acetate. The organic layer was washed in the following order: 25 mL of saline solution, 25 mL of saturated sodium bicarbonate solution, and 25 mL of saline solution, and dehydrated with anhydrous sodium sulfate. After filtering off the drying agent, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain compound (AA) (Rf in formula (AA)). ２ This is the PFPE chain represented by the above formula (5-2). Rf ２ In this case, j, which indicates the average degree of polymerization, represents 4.5. 3.51 g of ( ) was obtained.

[0250] The obtained compound (AA) １ H-NMR and １９ F-NMR measurements were performed, and the structure was identified based on the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 0.80-1.20 (6H), 3.40-3.85 (12H), 3.85-4.10 (4H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (18F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (9F)

[0251] [Example 2] The compound represented by formula (AB) above was obtained by the method shown below. The same procedure as in Example 1 was carried out, except that the compound represented by formula (6-2) was used instead of the compound represented by formula (6-1), and compound (AB) (Rf in formula (AB)) was obtained. ２ This is the PFPE chain represented by the above formula (5-2). Rf ２In this case, j, which indicates the average degree of polymerization, represents 4.5. 3.73 g of ( ) was obtained.

[0252] The compound represented by formula (6-2) was synthesized by the following method. First, the hydroxyl group of 1-hexen-3-ol was protected with dihydropyran (DHP). Subsequently, the carbon-carbon double bond was oxidized with m-chloroperbenzoic acid (mCPBA) to form an epoxy ring.

[0253] The obtained compound (AB) １ H-NMR and １９ F-NMR measurements were performed, and the structure was identified based on the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 0.80-1.20 (6H), 1.40-1.80 (8H), 3.40-3.85 (12H), 3.85-4.10 (4H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (18F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (9F)

[0254] [Example 3] The compound represented by formula (AC) above was obtained by the method shown below. The same procedure as in Example 1 was carried out, except that the compound represented by formula (6-3) was used instead of the compound represented by formula (6-1), and compound (AC) (Rf in formula (AC)) was obtained. ２ This is the PFPE chain represented by the above formula (5-2). Rf ２ In this case, j, which indicates the average degree of polymerization, represents 4.5. 3.77 g of ( ) was obtained.

[0255] The compound represented by formula (6-3) was synthesized by the following method. First, isobutyroaldehyde and vinylmagnesium bromomid were reacted. Subsequently, the hydroxyl group produced by the above reaction was protected with dihydropyran (DHP). Finally, the carbon-carbon double bond was oxidized with m-chloroperbenzoic acid (mCPBA) to form an epoxy ring.

[0256] The obtained compound (AC) １ H-NMR and １９F-NMR measurement was carried out, and the structure was identified based on the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 0.80 - 1.20 (12H), 1.40 - 1.80 (2H), 3.40 - 3.85 (12H), 3.85 - 4.10 (4H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (18F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (9F)

[0257] [Example 4] The compound represented by the above formula (AD) was obtained by the method shown below. The same operations as in Example 1 were carried out except that the compound represented by the formula (6-4) was used instead of the compound represented by the formula (6-1). Compound (AD) (Rf ２ in the formula (AD) is the PFPE chain represented by the above formula (5-2). In Rf ２ , j representing the average degree of polymerization represents 4.5.) was obtained in an amount of 3.61 g.

[0258] The compound represented by the formula (6-4) was synthesized by the method shown below. First, the hydroxyl group of 2-methyl-3-buten-1-ol was protected using dihydropyran (DHP). Subsequently, the carbon-carbon double bond was oxidized using m-chloroperbenzoic acid (mCPBA) to form an epoxy ring.

[0259] For the obtained compound (AD), １ H-NMR and １９ F-NMR measurements were carried out, and the structure was identified based on the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 0.80 - 1.20 (12H), 3.40 - 3.85 (10H), 3.85 - 4.10 (4H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (18F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (9F)

[0260] [Example 5] The compound represented by the above formula (AE) was obtained by the method shown below. The same operations as in Example 1 were carried out except that the compound represented by formula (6-5) was used instead of the compound represented by formula (6-1). Compound (AE) (Rf in formula (AE) ２ is the PFPE chain represented by the above formula (5-2). Rf ２ In, j representing the average degree of polymerization represents 4.5.) 3.86 g was obtained.

[0261] The compound represented by formula (6-5) was synthesized by the method shown below. First, the compound represented by formula (6-1) was reacted with allyl alcohol. Subsequently, the resulting hydroxyl group was protected using dihydropyran (DHP). Finally, the carbon-carbon double bond was oxidized using m-chloroperbenzoic acid (mCPBA) to form an epoxy ring.

[0262] For the obtained compound (AE), １ 1H-NMR and １９ 19F-NMR measurements were performed, and the structure was identified based on the following results. １ 1H-NMR (acetone-d ６ ): δ [ppm] = 0.80 - 1.20 (6H), 3.40 - 3.85 (24H), 3.85 - 4.10 (4H) １９ 19F-NMR (acetone-d ６ ): δ [ppm] = -84.0 to -83.0 (18F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (9F)

[0263] [Example 6] The compound represented by the above formula (AF) was obtained by the method shown below. The same operations as in Example 1 were carried out except that the compound represented by formula (6-6) was used instead of the compound represented by formula (6-1). Compound (AF) (Rf in formula (AF) ２ is the PFPE chain represented by the above formula (5-2). Rf ２ In, j representing the average degree of polymerization represents 4.5.) 3.74 g was obtained.

[0264] The compound represented by formula (6-6) was synthesized by the following method. First, the compound represented by formula (6-1) was reacted with 3-buten-1-ol. Subsequently, the resulting hydroxyl group was protected with dihydropyran (DHP). Finally, the carbon-carbon double bond was oxidized with m-chloroperbenzoic acid (mCPBA) to form an epoxy ring.

[0265] The obtained compound (AF) １ H-NMR and １９ F-NMR measurements were performed, and the structure was identified based on the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 0.80-1.20 (6H), 1.40-1.80 (4H), 3.40-3.85 (24H), 3.85-4.10 (4H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (18F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (9F)

[0266] [Example 7] The compound represented by formula (AG) above was obtained by the method shown below. The same procedure as in Example 1 was carried out, except that the compound represented by formula (6-7) was used instead of the compound represented by formula (6-1), and compound (AG) (Rf in formula (AG)) was obtained. ２ This is the PFPE chain represented by the above formula (5-2). Rf ２ In this case, j, which indicates the average degree of polymerization, represents 4.5. 3.55 g of ( ) was obtained.

[0267] The compound represented by formula (6-7) was synthesized by the following method. First, 3-pentenoic acid was reduced with lithium aluminum hydride, and the resulting hydroxyl group was benzyl protected with benzyl bromide. The olefin moiety of the resulting product was oxidized with m-chloroperbenzoic acid (mCPBA) to form an epoxy ring. The epoxy ring of the resulting epoxide was opened with dilute sulfuric acid, and the resulting hydroxyl group was protected with dihydropyran (DHP). Subsequently, the benzyl group was deprotected with palladium carbon, and the resulting hydroxyl group was reacted with an equimolar amount of epibromohydrin.

[0268] The obtained compound (AG) １ H-NMR and １９ F-NMR measurements were performed, and the structure was identified based on the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 0.80-1.20 (6H), 1.40-1.80 (4H), 3.40-3.85 (24H), 3.85-4.10 (4H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (18F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (9F)

[0269] [Example 8] The compound represented by the above formula (AH) was obtained by the method shown below. The same procedure as in Example 1 was carried out, except that the compound represented by formula (6-8) was used instead of the compound represented by formula (6-1), and compound (AH) (Rf in formula (AH)) was obtained. ２ This is the PFPE chain represented by the above formula (5-2). Rf ２ In this case, j, which indicates the average degree of polymerization, represents 4.5. 3.41 g of ( ) was obtained.

[0270] The compound represented by formula (6-8) was synthesized by the following method. First, the compound represented by formula (6-2) was reacted with allyl alcohol. Next, the resulting hydroxyl group was protected with dihydropyran (DHP). Finally, the carbon-carbon double bond was oxidized with m-chloroperbenzoic acid (mCPBA) to form an epoxy ring.

[0271] The obtained compound (AH) １ H-NMR and １９ F-NMR measurements were performed, and the structure was identified based on the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 0.80-1.20 (6H), 1.40-1.80 (8H), 3.40-3.85 (24H), 3.85-4.10 (4H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (18F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (9F)

[0272] [Example 9] The compound represented by formula (AI) above was obtained by the method shown below. The same procedure as in Example 1 was carried out, except that the compound represented by formula (6-9) was used instead of the compound represented by formula (6-1), and the compound (AI) (Rf in formula (AI)) was obtained. ２ This is the PFPE chain represented by the above formula (5-2). Rf ２ In this case, j, which indicates the average degree of polymerization, represents 4.5. 3.65 g of ( ) was obtained.

[0273] The compound represented by formula (6-9) was synthesized by the following method. First, the compound represented by formula (6-3) was reacted with allyl alcohol. Next, the resulting hydroxyl group was protected with dihydropyran (DHP). Finally, the carbon-carbon double bond was oxidized with m-chloroperbenzoic acid (mCPBA) to form an epoxy ring.

[0274] The obtained compound (AI) １ H-NMR and １９ F-NMR measurements were performed, and the structure was identified based on the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 0.80-1.20 (12H), 1.40-1.80 (2H), 3.40-3.85 (24H), 3.85-4.10 (4H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (18F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (9F)

[0275] [Example 10] The compound represented by formula (AJ) above was obtained by the method shown below. The same procedure as in Example 1 was carried out, except that the compound represented by formula (6-10) was used instead of the compound represented by formula (6-1), and compound (AJ) (Rf in formula (AJ)) was obtained. ２ This is the PFPE chain represented by the above formula (5-2). Rf ２ In this case, j, which indicates the average degree of polymerization, represents 4.5. 3.48 g of ( ) was obtained.

[0276] The compound represented by formula (6-10) was synthesized by the following method. First, the compound represented by formula (6-4) was reacted with allyl alcohol. Subsequently, the resulting hydroxyl group was protected with dihydropyran (DHP). Finally, the carbon-carbon double bond was oxidized with m-chloroperbenzoic acid (mCPBA) to form an epoxy ring.

[0277] The obtained compound (AJ) １ H-NMR and １９ F-NMR measurements were performed, and the structure was identified based on the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 0.80-1.20 (12H), 3.40-3.85 (22H), 3.85-4.10 (4H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (18F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (9F)

[0278] [Example 11] The compound represented by the above formula (AK) was obtained by the method shown below. The same procedure as in Example 1 was carried out, except that the compound represented by formula (6-11) was used instead of the compound represented by formula (6-1), and the compound (AK) (Rf in formula (AK)) was obtained. ２ This is the PFPE chain represented by the above formula (5-2). Rf ２ In this case, j, which indicates the average degree of polymerization, represents 4.5. 3.48 g of ( ) was obtained.

[0279] The compound represented by formula (6-11) was synthesized by the following method. First, the compound represented by formula (6-2) was reacted with 3-buten-1-ol. Subsequently, the resulting hydroxyl group was protected with dihydropyran (DHP). Finally, the carbon-carbon double bond was oxidized with m-chloroperbenzoic acid (mCPBA) to form an epoxy ring.

[0280] The obtained compound (AK) １ H-NMR and １９ F-NMR measurements were performed, and the structure was identified based on the following results. １ H-NMR (acetone-D ６): δ [ppm] = 0.80-1.20 (6H), 1.40-1.80 (12H), 3.40-3.85 (24H), 3.85-4.10 (4H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (18F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (9F)

[0281] [Example 12] The compound represented by formula (AL) above was obtained by the method shown below. The same procedure as in Example 1 was carried out, except that the compound represented by formula (6-12) was used instead of the compound represented by formula (6-1), and the compound (AL) (Rf in formula (AL)) was obtained. ２ This is the PFPE chain represented by the above formula (5-2). Rf ２ In this case, j, which indicates the average degree of polymerization, represents 4.5. 3.63 g of ( ) was obtained.

[0282] The compound represented by formula (6-12) was synthesized by the following method. First, the compound represented by formula (6-3) was reacted with 3-buten-1-ol. Subsequently, the resulting hydroxyl group was protected with dihydropyran (DHP). Finally, the carbon-carbon double bond was oxidized with m-chloroperbenzoic acid (mCPBA) to form an epoxy ring.

[0283] The obtained compound (AL) １ H-NMR and １９ F-NMR measurements were performed, and the structure was identified based on the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 0.80-1.20 (12H), 1.40-1.80 (6H), 3.40-3.85 (24H), 3.85-4.10 (4H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (18F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (9F)

[0284] [Example 13] The compound represented by the above formula (AM) was obtained by the method shown below. Except for using the compound represented by formula (6-13) instead of the compound represented by formula (6-1), the same operations as in Example 1 were carried out, and compound (AM) (Rf in formula (AM) ２ is the PFPE chain represented by the above formula (5-2). Rf ２ In, j indicating the average degree of polymerization represents 4.5.) 3.72 g was obtained.

[0285] The compound represented by formula (6-13) was synthesized by the method shown below. First, the compound represented by formula (6-4) was reacted with 3-buten-1-ol. Subsequently, the resulting hydroxyl group was protected using dihydropyran (DHP). Finally, the carbon-carbon double bond was oxidized using m-chloroperbenzoic acid (mCPBA) to form an epoxy ring.

[0286] For the obtained compound (AM), １ 1H-NMR and １９ 19F-NMR measurements were performed, and the structure was identified based on the following results. １ 1H-NMR (acetone-d ６ ): δ [ppm] = 0.80 - 1.20 (12H), 1.40 - 1.80 (4H), 3.40 - 3.85 (22H), 3.85 - 4.10 (4H) １９ 19F-NMR (acetone-d ６ ): δ [ppm] = -84.0 to -83.0 (18F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (9F)

[0287] [Example 14] The compound represented by the above formula (AN) was obtained by the method shown below. Except for using the compound represented by formula (6-14) instead of the compound represented by formula (6-1), the same operations as in Example 1 were carried out, and compound (AN) (Rf in formula (AN) ２ is the PFPE chain represented by the above formula (5-2). Rf ２ In, j indicating the average degree of polymerization represents 4.5.) 3.37 g was obtained. <0The compound represented by formula (6-14) was synthesized by the following method. First, the hydroxyl group of β-methallyl alcohol was protected with dihydropyran (DHP). Subsequently, the carbon-carbon double bond was oxidized with m-chloroperbenzoic acid (mCPBA) to form an epoxy ring.

[0289] The obtained compound (AN) １ H-NMR and １９ F-NMR measurements were performed, and the structure was identified based on the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 0.80-1.20 (6H), 3.40-3.85 (12H), 3.85-4.10 (4H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (18F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (9F)

[0290] [Example 15] The compound represented by the above formula (AO) was obtained by the method shown below. The same procedure as in Example 1 was carried out, except that the compound represented by formula (6-15) was used instead of the compound represented by formula (6-1), and the compound (AO) (Rf in formula (AO)) was obtained. ２ This is the PFPE chain represented by the above formula (5-2). Rf ２ In this case, j, which indicates the average degree of polymerization, represents 4.5. 3.62 g of ( ) was obtained.

[0291] The compound represented by formula (6-15) was synthesized by the following method. First, the compound represented by formula (6-14) was reacted with allyl alcohol. Subsequently, the resulting hydroxyl group was protected with dihydropyran (DHP). Finally, the carbon-carbon double bond was oxidized with m-chloroperbenzoic acid (mCPBA) to form an epoxy ring.

[0292] The obtained compound (AO) １ H-NMR and １９ F-NMR measurements were performed, and the structure was identified based on the following results. １ H-NMR (acetone-D ６): δ [ppm] = 0.80-1.20 (6H), 3.40-3.85 (24H), 3.85-4.10 (4H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (18F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (9F)

[0293] [Example 16] The compound represented by the above formula (AP) was obtained by the method shown below. The same procedure as in Example 1 was carried out, except that the compound represented by formula (6-16) was used instead of the compound represented by formula (6-1), and the compound (AP) (Rf in formula (AP)) was obtained. ２ This is the PFPE chain represented by the above formula (5-2). Rf ２ In this case, j, which indicates the average degree of polymerization, represents 4.5. 3.59 g of ( ) was obtained.

[0294] The compound represented by formula (6-16) was synthesized by the following method. First, the compound represented by formula (6-14) was reacted with 3-buten-1-ol. Subsequently, the resulting hydroxyl group was protected with dihydropyran (DHP). Finally, the carbon-carbon double bond was oxidized with m-chloroperbenzoic acid (mCPBA) to form an epoxy ring.

[0295] The obtained compound (AP) １ H-NMR and １９ F-NMR measurements were performed, and the structure was identified based on the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 0.80-1.20 (6H), 1.40-1.80 (4H), 3.40-3.85 (24H), 3.85-4.10 (4H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (18F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (9F)

[0296] [Example 17] The compound represented by formula (AQ) was obtained by the following method. The same procedure as in Example 1 was carried out, except that the compound represented by formula (6-17) was used instead of the compound represented by formula (6-1), and compound (AQ) (Rf in formula (AQ)) was obtained. ２ This is the PFPE chain represented by the above formula (5-2). Rf ２ In this case, j, which indicates the average degree of polymerization, represents 4.5. 3.42 g of ( ) was obtained.

[0297] The compound represented by formula (6-17) was synthesized by the following method. First, 2-allyloxytetrahydropyran was oxidized with m-chloroperbenzoic acid (mCPBA). Next, the resulting epoxide was reacted with β-methallyl alcohol, and the resulting hydroxyl group was protected with dihydropyran (DHP). Finally, the carbon-carbon double bond was oxidized with m-chloroperbenzoic acid (mCPBA) to form an epoxy ring.

[0298] The obtained compound (AQ) １ H-NMR and １９ F-NMR measurements were performed, and the structure was identified based on the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 0.80-1.20 (6H), 3.40-3.85 (24H), 3.85-4.10 (4H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (18F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (9F)

[0299] [Example 18] The compound represented by the above formula (AR) was obtained by the method shown below. The same procedure as in Example 1 was carried out, except that the compound represented by formula (6-18) was used instead of the compound represented by formula (6-1), and the compound (AR) (Rf in formula (AR)) was obtained. ２ This is the PFPE chain represented by the above formula (5-2). Rf ２ In this case, j, which indicates the average degree of polymerization, represents 4.5. 3.36 g of ( ) was obtained.

[0300] The compound represented by formula (6-18) was synthesized by the following method. First, 2-allyloxytetrahydropyran was oxidized with m-chloroperbenzoic acid (mCPBA). Next, the resulting epoxide was reacted with 3-methyl-3-buten-1-ol, and the resulting hydroxyl group was protected with dihydropyran (DHP). Finally, the carbon-carbon double bond was oxidized with m-chloroperbenzoic acid (mCPBA) to form an epoxy ring.

[0301] The obtained compound (AR) １ H-NMR and １９ F-NMR measurements were performed, and the structure was identified based on the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 0.80-1.20 (6H), 1.40-1.80 (4H), 3.40-3.85 (24H), 3.85-4.10 (4H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (18F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (9F)

[0302] [Example 19] The compound represented by the above formula (AS) was obtained by the method shown below. The same procedure as in Example 1 was carried out, except that the compound represented by formula (6-19) was used instead of the compound represented by formula (6-1), and compound (AS) (Rf in formula (AS)) was obtained. ２ This is the PFPE chain represented by the above formula (5-2). Rf ２ In this case, j, which indicates the average degree of polymerization, represents 4.5. 3.71 g of ( ) was obtained.

[0303] The compound represented by formula (6-19) was synthesized by the following method. First, the compound represented by formula (6-1) was reacted with β-methallyl alcohol. Subsequently, the resulting hydroxyl group was protected with dihydropyran (DHP). Finally, the carbon-carbon double bond was oxidized with m-chloroperbenzoic acid (mCPBA) to form an epoxy ring.

[0304] The obtained compound (AS) １ H-NMR and １９F-NMR measurements were performed, and the structure was identified based on the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 0.80-1.20 (12H), 3.40-3.85 (22H), 3.85-4.10 (4H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (18F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (9F)

[0305] [Example 20] The compound represented by the above formula (AT) was obtained by the method shown below. The same procedure as in Example 1 was carried out, except that the compound represented by formula (6-20) was used instead of the compound represented by formula (6-1), and the compound (AT) (Rf in formula (AT)) was obtained. ２ This is the PFPE chain represented by the above formula (5-2). Rf ２ In this case, j, which indicates the average degree of polymerization, represents 4.5. 3.53 g of ( ) was obtained.

[0306] The compound represented by formula (6-20) was synthesized by the following method. First, the compound represented by formula (6-4) was reacted with β-methallyl alcohol. Subsequently, the resulting hydroxyl group was protected with dihydropyran (DHP). Finally, the carbon-carbon double bond was oxidized with m-chloroperbenzoic acid (mCPBA) to form an epoxy ring.

[0307] The obtained compound (AT) １ H-NMR and １９ F-NMR measurements were performed, and the structure was identified based on the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 0.80-1.20 (18H), 3.40-3.85 (20H), 3.85-4.10 (4H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (18F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (9F)

[0308] [Example 21] The compound represented by the above formula (AU) was obtained by the method shown below. The same procedure as in Example 1 was carried out, except that the compound represented by formula (6-21) was used instead of the compound represented by formula (6-1), and the compound (AU) (Rf in formula (AU)) was obtained. ２ This is the PFPE chain represented by the above formula (5-2). Rf ２ In this case, j, which indicates the average degree of polymerization, represents 4.5. 3.40 g of ( ) was obtained.

[0309] The compound represented by formula (6-21) was synthesized by the following method. First, the compound represented by formula (6-1) was reacted with 3-methyl-3-buten-1-ol. Subsequently, the resulting hydroxyl group was protected with dihydropyran (DHP). Finally, the carbon-carbon double bond was oxidized with m-chloroperbenzoic acid (mCPBA) to form an epoxy ring.

[0310] The obtained compound (AU) １ H-NMR and １９ F-NMR measurements were performed, and the structure was identified based on the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 0.80-1.20 (18H), 1.40-1.80 (4H), 3.40-3.85 (20H), 3.85-4.10 (4H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (18F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (9F)

[0311] [Example 22] The compound represented by formula (AV) above was obtained by the method shown below. The same procedure as in Example 1 was carried out, except that the compound represented by formula (6-22) was used instead of the compound represented by formula (6-1), and compound (AV) (Rf in formula (AV)) was obtained. ２ This is the PFPE chain represented by the above formula (5-2). Rf ２ In this case, j, which indicates the average degree of polymerization, represents 4.5. 3.74 g of ( ) was obtained.

[0312] The compound represented by formula (6-22) was synthesized by the following method. First, the compound represented by formula (6-14) was reacted with β-methallyl alcohol. Subsequently, the resulting hydroxyl group was protected with dihydropyran (DHP). Finally, the carbon-carbon double bond was oxidized with m-chloroperbenzoic acid (mCPBA) to form an epoxy ring.

[0313] The obtained compound (AV) １ H-NMR and １９ F-NMR measurements were performed, and the structure was identified based on the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 0.80-1.20 (12H), 3.40-3.85 (22H), 3.85-4.10 (4H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (18F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (9F)

[0314] [Example 23] The compound represented by formula (AW) above was obtained by the method shown below. The same procedure as in Example 1 was carried out, except that the compound represented by formula (6-23) was used instead of the compound represented by formula (6-1), and compound (AW) (Rf in formula (AW)) was obtained. ２ This is the PFPE chain represented by the above formula (5-2). Rf ２ In this case, j, which indicates the average degree of polymerization, represents 4.5. 3.56 g of ( ) was obtained.

[0315] The compound represented by formula (6-23) was synthesized by the following method. First, the compound represented by formula (6-14) was reacted with 3-methyl-3-buten-1-ol. Subsequently, the resulting hydroxyl group was protected with dihydropyran (DHP). Finally, the carbon-carbon double bond was oxidized with m-chloroperbenzoic acid (mCPBA) to form an epoxy ring.

[0316] The obtained compound (AW) １ H-NMR and １９ F-NMR measurements were performed, and the structure was identified based on the following results. １ H-NMR (acetone-D６ ): δ [ppm] = 0.80-1.20 (12H), 1.40-1.80 (4H), 3.40-3.85 (22H), 3.85-4.10 (4H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (18F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (9F)

[0317] [Example 24] The compound represented by the above formula (AX) was obtained by the following method. (First reaction) Under a nitrogen gas atmosphere, HOCH4 was added to a 100 mL round-bottom flask. ２ CF ２ CF ２ O(CF) ２ CF ２ CF ２ O) ｊ CF ２ CF ２ CH ２ 10 g (10.5 mmol) of the compound represented by OH (where j, representing the average degree of polymerization in the formula, is 4.5) (number average molecular weight 950, molecular weight distribution 1.1), 1.8 g (10.5 mmol) of the compound represented by the above formula (6-1), and 10 mL of t-butanol were charged together and stirred at room temperature until homogeneous to form a mixture. 1.30 g of potassium tert-butoxide was added to this mixture and the mixture was stirred at 70°C for 16 hours to allow it to react.

[0318] The reaction product obtained after the reaction was cooled to 25°C, transferred to a separatory funnel containing 100 mL of water, and extracted three times with 100 mL of ethyl acetate. The organic layer was washed with water and dehydrated with anhydrous sodium sulfate. After filtering off the drying agent, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 5.88 g of the compound represented by the following formula (10-1) as intermediate compound 1.

[0319] (Rf in equation (10-1)) ２ This is the PFPE chain represented by the above formula (5-2). Rf ２ In this case, j, which indicates the average degree of polymerization, represents 4.5.

[0320] (Second reaction) Next, under a nitrogen gas atmosphere, 5.88 g (5.2 mmol) of the compound represented by formula (10-1), which is intermediate compound 1 obtained above, 1.81 g (5.5 mmol) of the compound represented by formula (6-5), and 20 mL of t-butanol were charged into a 100 mL round-bottom flask and stirred at room temperature until homogeneous to form a mixture. 0.65 g of potassium tert-butoxide was added to this mixture and the mixture was stirred at 70°C for 16 hours to allow it to react.

[0321] The reaction mixture obtained after the reaction was allowed to return to room temperature, and 50 g of 10% hydrogen chloride / methanol solution (hydrogen chloride-methanol reagent (5-10%) manufactured by Tokyo Chemical Industry Co., Ltd.) was added and stirred at room temperature for 4 hours. Then, the reaction mixture was gradually transferred to a separatory funnel containing 100 mL of saturated sodium bicarbonate solution and extracted twice with 200 mL of ethyl acetate. The organic layer was washed in the following order: 100 mL of saline solution, 100 mL of saturated sodium bicarbonate solution, and 100 mL of saline solution, and dehydrated with anhydrous sodium sulfate. After filtering off the drying agent, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain compound (AX) (Rf in formula (AX)). ２ This is the PFPE chain represented by the above formula (5-2). Rf ２ In this case, j, which indicates the average degree of polymerization, represents 4.5. 3.87 g of ( ) was obtained.

[0322] The obtained compound (AX) １ H-NMR and １９ F-NMR measurements were performed, and the structure was identified based on the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 0.80-1.20 (6H), 3.40-3.85 (18H), 3.85-4.10 (4H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (18F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (9F)

[0323] [Example 25] The compound represented by formula (AY) above was obtained by the method shown below. The same procedure as in Example 24 was performed, except that the compound represented by formula (6-14) was used instead of the compound represented by formula (6-1), and the compound represented by formula (6-22) was used instead of the compound represented by formula (6-5), and compound (AY) (Rf in formula (AY)) was obtained. ２ This is the PFPE chain represented by the above formula (5-2). Rf ２ In this case, j, which indicates the average degree of polymerization, represents 4.5. 3.81 g of ( ) was obtained.

[0324] The obtained compound (AY) １ H-NMR and １９ F-NMR measurements were performed, and the structure was identified based on the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 0.80-1.20 (9H), 3.40-3.85 (17H), 3.85-4.10 (4H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (18F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (9F)

[0325] [Example 26] The compound represented by formula (AZ) above was obtained by the method shown below. The same procedure as in Example 1 was carried out, except that the compound represented by formula (6-24) was used instead of the compound represented by formula (6-1), and the compound (AZ) (Rf in formula (AZ)) was obtained. ２ This is the PFPE chain represented by the above formula (5-2). Rf ２ In this case, j, which indicates the average degree of polymerization, represents 4.5. 3.37 g of ( ) was obtained.

[0326] The compound represented by formula (6-24) was synthesized by the following method. First, the hydroxyl group of dihydroxyacetone was protected with dihydropyran (DHP). Next, the ketone was reduced with sodium borohydride, and the resulting hydroxyl group was reacted with 3-bromo-2-methyl-1-propene. Finally, the carbon-carbon double bond was oxidized with m-chloroperbenzoic acid (mCPBA) to form an epoxy ring.

[0327] The obtained compound (AZ) １ H-NMR and １９ F-NMR measurements were performed, and the structure was identified based on the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 0.80-1.20 (6H), 3.40-3.85 (24H), 3.85-4.10 (4H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (18F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (9F)

[0328] [Example 27] The compound represented by the above formula (BA) was obtained by the method shown below. HOCH ２ CF ２ CF ２ O(CF) ２ CF ２ CF ２ O) ｊ CF ２ CF ２ CH ２ Instead of OH, use HOCH ２ CF ２ O(CF) ２ CF ２ O) ｈ (CF ２ O) ｉ CF ２ CH ２ The same procedure as in Example 1 was carried out, except that a compound represented by OH (where h, which indicates the average degree of polymerization in the formula, is 7.0 and i is 0) (number average molecular weight 1000, molecular weight distribution 1.1) was used, and the compound (BA) (where Rf in formula (BA)) was obtained. １ This is the PFPE chain represented by the above formula (5-1). Rf １ In this case, h, which represents the average degree of polymerization, is 7.0, and i, which represents the average degree of polymerization, is 0. 3.63 g of ( ) was obtained.

[0329] The obtained compound (BA) １ H-NMR and １９ F-NMR measurements were performed, and the structure was identified based on the following results. １ H-NMR (acetone-D ６): δ [ppm] = 0.80-1.20 (6H), 3.40-3.85 (12H), 3.85-4.10 (4H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -80.5 (4F), -91.0 to -88.5 (28F)

[0330] [Example 28] The compound represented by the above formula (BB) was obtained by the method shown below. HOCH ２ CF ２ CF ２ O(CF) ２ CF ２ CF ２ O) ｊ CF ２ CF ２ CH ２ Instead of OH, use HOCH ２ CF ２ O(CF) ２ CF ２ O) ｈ (CF ２ O) ｉ CF ２ CH ２ Using a compound represented by OH (where h, which indicates the average degree of polymerization in the formula, is 4.5 and i, is 4.5) (number average molecular weight 1000, molecular weight distribution 1.1), the same procedure as in Example 1 was carried out, except that the compound represented by formula (6-6) was used instead of the compound represented by formula (6-1), and the compound (BB) (Rf in formula (BB)) was used. １ This is the PFPE chain represented by the above formula (5-1). Rf １ In this case, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, also represents 4.5. 3.82 g of ( ) was obtained.

[0331] The obtained compound (BB) １ H-NMR and １９ F-NMR measurements were performed, and the structure was identified based on the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 0.80-1.20 (6H), 3.40-3.85 (24H), 3.85-4.10 (4H) １９ F-NMR (acetone-D ６): δ [ppm] = -55.5 to -51.5 (9F), -78.5 (2F), -80.5 (2F), -91.0 to -88.5 (18F)

[0332] [Example 29] The compound represented by the above formula (BC) was obtained by the method shown below. HOCH ２ CF ２ CF ２ O(CF) ２ CF ２ CF ２ O) ｊ CF ２ CF ２ CH ２ Instead of OH, use HOCH ２ CF ２ CF ２ CF ２ O(CF) ２ CF ２ CF ２ CF ２ O) ｋ CF ２ CF ２ CF ２ CH ２ Using a compound represented by OH (where k, which indicates the average degree of polymerization in the formula, is 3.0) (number average molecular weight 1000, molecular weight distribution 1.1), the same procedure as in Example 1 was carried out, except that the compound represented by formula (6-17) was used instead of the compound represented by formula (6-1), and the compound (BC) (where Rf in formula (BC)) was used. ３ This is the PFPE chain represented by the above formula (5-3). Rf ３ In this case, k, which indicates the average degree of polymerization, represents 3.0. 3.64 g of ( ) was obtained.

[0333] The obtained compound (BC) １ H-NMR and １９ F-NMR measurements were performed, and the structure was identified based on the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 0.80-1.20 (6H), 3.40-3.85 (24H), 3.85-4.10 (4H) １９ F-NMR (acetone-D ６): δ [ppm] = -84.0 to -83.0 (16F), -122.5 (4F), -126.0 (12F), -129.0 to -128.0 (4F)

[0334] [Example 30] The compound represented by formula (BD) above was obtained by the method shown below. The same procedure as in Example 24 was performed, except that the compound represented by formula (6-5) was used instead of the compound represented by formula (6-1), and the compound represented by formula (6-25) was used instead of the compound represented by formula (6-5), and compound (BD) (Rf in formula (BD)) was obtained. ２ This is the PFPE chain represented by the above formula (5-2). Rf ２ In this case, j, which indicates the average degree of polymerization, represents 4.5. 3.75 g of ( ) was obtained.

[0335] The obtained compound (BD) １ H-NMR and １９ F-NMR measurements were performed, and the structure was identified based on the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 0.80-1.20 (3H), 1.80-2.10 (3H), 3.40-3.85 (22H), 3.85-4.10 (4H), 6.30-6.80 (1H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (18F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (9F)

[0336] [Example 31] The compound represented by formula (BE) above was obtained by the method shown below. The same procedure as in Example 24 was carried out, except that the compound represented by formula (6-26) was used instead of the compound represented by formula (6-5), and the compound (BE) (Rf in formula (BE)) was obtained. ２ This is the PFPE chain represented by the above formula (5-2). Rf ２ In this case, j, which indicates the average degree of polymerization, represents 4.5. 3.48 g of ( ) was obtained.

[0337] The obtained compound (BE) １ H-NMR and １９ F-NMR measurements were performed, and the structure was identified based on the following results. １H-NMR (acetone-D ６ ): δ [ppm] = 0.80-1.20 (3H), 3.40-3.85 (19H), 3.85-4.10 (4H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (18F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (9F)

[0338] [Example 32] The compound represented by formula (BF) above was obtained by the method shown below. The same procedure as in Example 24 was carried out except that the compound represented by formula (6-27) was used instead of the compound represented by formula (6-5), and the compound (BF) (Rf in formula (BF)) was obtained. ２ This is the PFPE chain represented by the above formula (5-2). Rf ２ In this case, j, which indicates the average degree of polymerization, represents 4.5. 3.52 g of ( ) was obtained.

[0339] The obtained compound (BF) １ H-NMR and １９ F-NMR measurements were performed, and the structure was identified based on the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 0.80-1.20 (3H), 1.40-1.80 (2H), 2.10-2.30 (2H), 3.40-3.85 (22H), 3.85-4.10 (4H), 5.20-5.40 (1H), 5.80-6.10 (1H), 6.20-6.40 (1H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (18F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (9F)

[0340] [Example 33] The compound represented by formula (BG) above was obtained by the method shown below. The same procedure as in Example 24 was carried out except that the compound represented by formula (6-28) was used instead of the compound represented by formula (6-5), and the compound (BF) (Rf in formula (BF)) was obtained. ２ This is the PFPE chain represented by the above formula (5-2). Rf ２In this case, j, which indicates the average degree of polymerization, represents 4.5. 3.63 g of ( ) was obtained.

[0341] The obtained compound (BG) １ H-NMR and １９ F-NMR measurements were performed, and the structure was identified based on the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 0.80-1.20 (3H), 1.40-1.80 (2H), 3.40-3.85 (21H), 3.85-4.10 (4H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (18F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (9F)

[0342] [Example 34] The compound represented by the above formula (CA) was obtained by the method shown below. First, the same procedure as the first reaction in Example 24 was carried out to obtain 5.74 g of the compound represented by the above formula (10-1) as intermediate compound 1.

[0343] Next, under a nitrogen gas atmosphere, 5.74 g (5.1 mmol) of the compound represented by formula (10-1), which is intermediate compound 1 obtained above, 0.35 g (2.4 mmol) of the compound represented by formula (8-2), and 10 mL of t-butanol were charged into a 100 mL round-bottom flask and stirred at room temperature until homogeneous. 0.64 g of potassium tert-butoxide was added to this homogeneous solution and the mixture was stirred at 70°C for 23 hours to allow the reaction to proceed.

[0344] The compound represented by formula (8-2) was synthesized by the following method. First, epibromohydrin represented by formula (8-1) was added to 3-buten-1-ol in an amount twice its molar proportion. Subsequently, the resulting hydroxyl group was protected with dihydropyran (DHP). Finally, the carbon-carbon double bond was oxidized with m-chloroperbenzoic acid (mCPBA) to form an epoxy ring.

[0345] The reaction mixture obtained after the reaction was allowed to return to room temperature, and 10 g of 10% hydrogen chloride / methanol solution (hydrogen chloride-methanol reagent (5-10%) manufactured by Tokyo Chemical Industry Co., Ltd.) was added and stirred at room temperature for 4 hours. Then, the reaction mixture was gradually transferred to a separatory funnel containing 25 mL of saturated sodium bicarbonate solution and extracted twice with 50 mL of ethyl acetate. The organic layer was washed in the following order: 25 mL of saline solution, 25 mL of saturated sodium bicarbonate solution, and 25 mL of saline solution, and dehydrated with anhydrous sodium sulfate. After filtering off the drying agent, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain compound (CA) (the two Rf in formula (CA)). ２ This is a PFPE chain represented by the above formula (5-2). Two Rf ２ In this case, j, which indicates the average degree of polymerization, represents 4.5. 3.23 g of ( ) was obtained.

[0346] The obtained compound (CA) １ H-NMR and １９ F-NMR measurements were performed, and the structure was identified based on the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 0.80-1.20 (6H), 1.40-1.80 (4H), 3.40-3.85 (30H), 3.85-4.10 (8H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (36F), -86.4 (8F), -124.3 (8F), -130.0 to -129.0 (18F)

[0347] [Example 35] The compound represented by formula (CB) above was obtained by the method shown below. The same procedure as in Example 34 was carried out, except that the compound represented by formula (8-3) was used instead of the compound represented by formula (8-2), and compound (CB) (the two Rf in formula (CB)) ２ This is a PFPE chain represented by the above formula (5-2). Two Rf ２ In this case, j, which indicates the average degree of polymerization, represents 4.5. 3.42 g of ( ) was obtained.

[0348] The obtained compound (CB) １ H-NMR and １９ F-NMR measurements were performed, and the structure was identified based on the following results. １H-NMR (acetone-D ６ ): δ [ppm] = 0.80-1.20 (6H), 1.40-1.80 (8H), 3.40-3.85 (20H), 3.85-4.10 (8H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (36F), -86.4 (8F), -124.3 (8F), -130.0 to -129.0 (18F)

[0349] [Example 36] The compound represented by the above formula (CC) was obtained by the method shown below. The same procedure as in Example 34 was carried out, except that the compound represented by formula (8-4) was used instead of the compound represented by formula (8-2), and compound (CC) (the two Rf in formula (CC)) ２ This is a PFPE chain represented by the above formula (5-2). Two Rf ２ In this case, j, which indicates the average degree of polymerization, represents 4.5. 3.76 g of ( ) was obtained.

[0350] The compound represented by formula (8-4) was synthesized by the following method. First, 1,2:3,4-diepoxybutane was added to 3-buten-1-ol in an amount twice its molar proportion. Subsequently, the resulting hydroxyl group was protected with dihydropyran (DHP). Finally, the carbon-carbon double bond was oxidized with m-chloroperbenzoic acid (mCPBA) to form an epoxy ring.

[0351] The obtained compound (CC) １ H-NMR and １９ F-NMR measurements were performed, and the structure was identified based on the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 0.80-1.20 (6H), 1.40-1.80 (4H), 3.40-3.85 (32H), 3.85-4.10 (8H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (36F), -86.4 (8F), -124.3 (8F), -130.0 to -129.0 (18F)

[0352] [Example 37] The compound represented by formula (CD) above was obtained by the method shown below. The procedure was the same as in Example 34, except that the compound represented by formula (6-5) was used instead of the compound represented by formula (6-1), and the epibromohydrin represented by formula (8-1) was used instead of the compound represented by formula (8-2). Compound (CD) (the two Rf in formula (CD)) ２ This is a PFPE chain represented by the above formula (5-2). Two Rf ２ In this case, j, which indicates the average degree of polymerization, represents 4.5. 3.21 g of ( ) was obtained.

[0353] The obtained compound (CD) １ H-NMR and １９ F-NMR measurements were performed, and the structure was identified based on the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 0.80-1.20 (6H), 3.40-3.85 (30H), 3.85-4.10 (8H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (36F), -86.4 (8F), -124.3 (8F), -130.0 to -129.0 (18F)

[0354] When the compounds of Examples 1 to 37 obtained in this way are substituted into formula (1), x and R １ , R ２ , R ３ , R ４ The structure is shown in Tables 1 to 3.

[0355]

[0356]

[0357]

[0358] [Comparative Example 1] A compound represented by the following formula (ZA) was obtained by the method described in Patent Document 1.

[0359] (Rf in equation (ZA)) ２ This is the PFPE chain represented by the above formula (5-2). Rf ２In this case, j, which indicates the average degree of polymerization, represents 4.5.

[0360] [Comparative Example 2] A compound represented by the following formula (ZB) was obtained by the method described in Patent Document 2.

[0361] (Rf in equation (ZB)) １ This is the PFPE chain represented by the above formula (5-1). Rf １ In this case, h, which represents the average degree of polymerization, is 4.5, and i, which also represents the average degree of polymerization, is 4.5.

[0362] [Comparative Example 3] A compound represented by the following formula (ZC) was obtained by the method described in Patent Document 3.

[0363] (Rf in equation (ZC)) １ This is the PFPE chain represented by the above formula (5-1). Rf １ In this case, h, which represents the average degree of polymerization, is 4.5, and i, which also represents the average degree of polymerization, is 4.5.

[0364] [Comparative Example 4] A compound represented by the following formula (ZD) was obtained by the method described in Patent Document 4.

[0365] (Rf in equation (ZD)) １ This is the PFPE chain represented by the above formula (5-1). Rf １ In this case, h, which represents the average degree of polymerization, is 4.5, and i, which also represents the average degree of polymerization, is 4.5.

[0366] [Comparative Example 5] A compound represented by the following formula (ZE) was obtained by the method described in Patent Document 5.

[0367] (Rf in equation (ZE)) １ This is the PFPE chain represented by the above formula (5-1). Rf １ In this case, h, which represents the average degree of polymerization, is 4.5, and i, which also represents the average degree of polymerization, is 4.5.

[0368] [Comparative Example 6] The compound described in Patent Document 6, represented by the following formula (ZF), was obtained by the method shown below. The same procedure as in Example 24 was carried out, except that 1,2-butylene oxide was used instead of the compound represented by formula (6-1) and glycidol was used instead of the compound represented by formula (6-5), and the compound (ZF) (Rf in formula (ZF)) was obtained. ２ This is the PFPE chain represented by the above formula (5-2). Rf ２ In this case, j, which indicates the average degree of polymerization, represents 4.5. 3.12 g of ( ) was obtained.

[0369] (Rf in equation (ZF)) ２ This is the PFPE chain represented by the above formula (5-2). Rf ２ In this case, j, which indicates the average degree of polymerization, represents 4.5.

[0370] The obtained compound (ZF) １ H-NMR and １９ F-NMR measurements were performed, and the structure was identified based on the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 0.80-1.20 (3H), 1.40-1.80 (3H), 3.40-3.85 (11H), 3.85-4.10 (4H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (18F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (9F)

[0371] [Comparative Example 7] A compound represented by the following formula (ZG) was obtained by the method described in Patent Document 7.

[0372] (The two Rf in equation (ZG) １ This is a PFPE chain represented by the above formula (5-1). Two Rf １ In this case, h, which represents the average degree of polymerization, is 4.5, and i, which also represents the average degree of polymerization, is 4.5.

[0373] [Comparative Example 8] A compound represented by the following formula (ZH) was obtained by the method described in Patent Document 8.

[0374] (The two Rf in equation (ZH) １ This is a PFPE chain represented by the above formula (5-1). Two Rf １ In this case, h, which represents the average degree of polymerization, is 4.5, and i, which also represents the average degree of polymerization, is 4.5.

[0375] The number-average molecular weight (Mn) of the compounds obtained in Examples 1 to 37 and Comparative Examples 1 to 8 was measured using the method described above. The results are shown in Tables 4 and 5.

[0376]

[0377]

[0378] Next, lubricating layer-forming solutions were prepared using the compounds obtained in Examples 1 to 37 and Comparative Examples 1 to 8 by the method described below. Then, using the obtained lubricating layer-forming solutions, a lubricating layer was formed on a magnetic recording medium by the method described below, and the magnetic recording media of Examples 1 to 37 and Comparative Examples 1 to 8 were obtained.

[0379] "Solution for Lubrication Layer Formation" The compounds obtained in Examples 1 to 37 and Comparative Examples 1 to 8 were each dissolved in Bartrell® XF (trade name, manufactured by Mitsui DuPont Fluorochemicals), a fluorine-based solvent, and diluted with Bartrell XF so that the film thickness when applied to the protective layer was 9.0 Å to 9.5 Å, to prepare the solution for lubrication layer formation.

[0380] A magnetic recording medium was prepared by sequentially forming an adhesive layer, a soft magnetic layer, a first underlayer, a second underlayer, a magnetic layer, and a protective layer on a substrate with a diameter of 65 mm. The protective layer was made of carbon. The lubricating layer-forming solutions of Examples 1 to 37 and Comparative Examples 1 to 8 were applied to the protective layer of the magnetic recording medium, where each layer up to the protective layer had been formed, by the dipping method. The dipping method was performed under the following conditions: dipping speed of 10 mm / sec, dipping time of 30 sec, and withdrawal speed of 1.2 mm / sec.

[0381] Subsequently, the magnetic recording medium coated with the lubricating layer-forming solution was placed in a constant temperature bath, and a heat treatment was performed at 120°C for 10 minutes to remove the solvent from the lubricating layer-forming solution and improve the adhesion between the protective layer and the lubricating layer, thereby forming a lubricating layer on the protective layer and obtaining a magnetic recording medium.

[0382] [Film Thickness Measurement] The film thickness of the lubricating layer in the magnetic recording media of Examples 1 to 37 and Comparative Examples 1 to 8 obtained in this manner was measured using a Fourier transform infrared spectrophotometer (FT-IR, trade name: Nicolet iS50, manufactured by Thermo Fisher Scientific). The results are shown in Tables 4 and 5.

[0383] Next, the magnetic recording media of Examples 1 to 37 and Comparative Examples 1 to 8 were subjected to the following buoyancy stability tests and corrosion resistance tests. (Buoyancy Stability Test) The glide tests and credence measurements described below were performed, and buoyancy stability was evaluated based on the following evaluation criteria. The results are shown in Tables 4 and 5.

[0384] "Glide Test" The glide test inspects whether there are any protrusions on the surface of a magnetic recording medium. In other words, when recording and playback are performed on a magnetic recording medium using a magnetic head, if there are protrusions on the surface of the magnetic recording medium that are taller than the levitation amount (the distance between the magnetic recording medium and the magnetic head), the magnetic head may collide with the protrusion, causing damage to the magnetic head or defects in the magnetic recording medium. In the glide test, 50 magnetic recording media are inspected for the presence of protrusions taller than the levitation amount on their surfaces.

[0385] Specifically, the distance between the inspection magnetic head and the magnetic recording medium was set to 0.25 microinches. The inspection magnetic head was moved over the magnetic recording medium, and if a signal was output from the inspection magnetic head due to collision with a protrusion on the surface of the magnetic recording medium, that magnetic recording medium was judged to be defective; otherwise, it was judged to be acceptable. The evaluation was then performed using the number of magnetic recording mediums judged to be acceptable out of 50.

[0386] "Credence Measurement" When performing the glide test described above, noise may temporarily increase, and even at the same location on the magnetic recording medium, signals caused by collisions with surface protrusions may be detected or not detected in multiple measurements. This phenomenon is called credence. Credence is not detected as a protrusion in the glide test and is not used to determine whether the glide test is successful or not. However, a temporary increase in noise in the glide test generally indicates non-uniformity of the lubricant layer or the presence of relatively soft foreign matter. For this reason, the average credence value was calculated by performing a glide test on the magnetic recording medium and dividing the total number of times credence was detected by the number of magnetic recording media subjected to the glide test (50 sheets), and this was used as an indicator of the smoothness and cleanliness of the lubricant layer.

[0387] "Evaluation Criteria" A+: 45 or more successful glide tests and average credence less than 0.5 A: 45 or more successful glide tests and average credence between 0.5 and 1.0 B: 45 or more successful glide tests and average credence between 1.0 and 5.0 C: 45 or more successful glide tests and average credence of 5.0 or higher D: Less than 45 successful glide tests

[0388] (Corrosion Resistance Test) Magnetic recording media were exposed to conditions of 85°C and 90% relative humidity for 48 hours. Subsequently, the number of corrosion spots with a diameter of 5 μm or more that formed on the surface of the magnetic recording media was counted using an optical surface analyzer (Candela 7140, manufactured by KLA-Tencor Co., Ltd.) and evaluated based on the following evaluation criteria. The results are shown in Tables 4 and 5.

[0389] "Evaluation Criteria" A+: Less than 30 corrosion spots A: 30 or more, less than 100 corrosion spots B: 100 or more, less than 300 corrosion spots C: 300 or more, less than 1000 corrosion spots D: 1000 or more corrosion spots

[0390] (Overall Evaluation) Based on the results of the buoyancy stability test and corrosion resistance test, an overall evaluation was conducted according to the following criteria: "Overall Evaluation" A: Both the buoyancy stability test evaluation and the corrosion resistance test evaluation are A+ or A B: One of the buoyancy stability test evaluation and the corrosion resistance test evaluation is B, and the other is A+, A, or B C: One of the buoyancy stability test evaluation and the corrosion resistance test evaluation is C, and the other is A+, A, B, or C D: At least one of the buoyancy stability test evaluation and the corrosion resistance test evaluation is D

[0391] As shown in Table 4, R is located at the end of the skeleton containing the perfluoropolyether chain. １ and R ４ Of these, the magnetic recording media of Examples 1 to 37, which used fluorine-containing ether compounds satisfying formula (1) in which at least one of the terminal groups is represented by formula (2), all received an evaluation of A+, A, or B in the levitation stability test and corrosion resistance test, and an overall evaluation of A or B. From this, it was confirmed that by providing a lubricating layer using the compounds of Examples 1 to 37, magnetic recording media with good levitation stability and corrosion resistance can be obtained.

[0392] In particular, R １ and R ４ These are all terminal groups represented by the above formula (2-1) or (2-2), and Ra １ / Ra ２ is a methyl group, Rb １ / Rb ２ Magnetic recording media using compounds (AA), (AE) to (AG), (AX), (BA), (BB), and (CA) to (CD), all of which are hydrogen atoms, all achieved an A+ rating in levitation stability tests. This is presumed to be because these compounds have a sufficient number of hydroxyl groups that can interact with the protective layer, resulting in high adhesion to the protective layer. Furthermore, the methyl groups substituted on carbon atoms adjacent to the terminal hydroxyl groups suppress the interaction between hydroxyl groups, making it less likely for polar groups to aggregate and form clumps.

[0393] Also, R １ and R ４ These are all terminal groups represented by the above formula (2-1) or (2-2), and Ra １ / Ra ２ and Rb １ / Rb ２ Magnetic recording media using compounds (AD), (AJ), and (AM), all of which are methyl groups, all received an A+ rating in corrosion resistance tests. １ and R ４ Magnetic recording media using compounds (AN) to (AR), (AT) to (AW), (AY), (AZ), and (BC), all of which have terminal groups represented by the above formulas (2-3) to (2-8), also all showed an A+ result in corrosion resistance tests. The reason for this is presumed to be that these compounds have a sufficient number of hydroxyl groups that can interact with the protective layer, exhibit high adhesion to the protective layer, and the hydroxyl groups adjacent to the alkyl group-introduced carbon atoms are tertiary hydroxyl groups with low hydrophilicity.

[0394] In contrast, as shown in Table 5, the magnetic recording media of Comparative Examples 1 to 8, which used compounds (ZA) to (ZE), all received evaluations of B, C, or D in the levitation stability test and corrosion resistance test, and the overall evaluation was C or D.

[0395] More specifically, the hydroxyl groups of compounds (ZA), (ZB), (ZG), and (ZH) used in the magnetic recording media of Comparative Examples 1, 2, 7, and 8 have a glycerin structure (-O-CH ２ -CH(OH)-CH ２ The hydroxyl groups are bonded to carbon atoms in the glycerin structure (-O-) or the structure in which the glycerin structure is extended with methylene groups. However, the carbon atoms to which the hydroxyl groups of compounds (ZA), (ZB), (ZG), and (ZH) are bonded are not substituents bonded to atoms other than those forming the glycerin structure or the structure in which the glycerin structure is extended with methylene groups. Therefore, the hydroxyl groups in compounds (ZA), (ZB), (ZG), and (ZH) have almost no steric hindrance, and interactions between hydroxyl groups occur easily. As a result, it is presumed that in the lubricating layer formed using compounds (ZA), (ZB), (ZG), and (ZH), polar groups that do not interact with the protective layer aggregate and form clumps, making it easier for the magnetic head to collide. For this reason, it is presumed that the results of the levitation stability test for the magnetic recording media of Comparative Examples 1, 2, 7, and 8 all resulted in C.

[0396] Furthermore, in Comparative Examples 1 and 7, compounds (ZA) and (ZG) consisting solely of glycerin structures without extended end groups and linking groups were used. Therefore, it is believed that the high polarity of the lubricating layer made it easier for the lubricating layer itself to absorb water, thus inducing corrosion of the magnetic recording medium. This is presumed to be the reason why Comparative Examples 1 and 7 received a D rating in the corrosion resistance test.

[0397] Furthermore, the compounds (ZC) to (ZF) used in the magnetic recording media of Comparative Examples 3 to 6 have a structure in which substituents other than those forming a glycerin structure or a structure in which a glycerin structure is extended by a methylene group are bonded to the carbon atom to which the hydroxyl group of the terminal group is bonded. However, the carbon atom to which the hydroxyl group of the terminal group is bonded has a glycerin structure (-O-CH ２ -CH(OH)-CH ２ It is not in the -O-) structure, or in a structure in which the glycerin structure is extended with methylene groups. Therefore, it is thought that the hydroxyl groups contained in compounds (ZC) to (ZF) could not adequately interact with the protective layer, resulting in insufficient adhesion to the protective layer and inadequate coverage of the protective layer by the lubricating layer.

[0398] Therefore, it is presumed that in the magnetic recording media of Comparative Examples 3 to 6, the surface smoothness was lost, and sufficient buoyancy stability could not be obtained, resulting in all buoyancy stability test results being D. Furthermore, if the lubricating layer does not adequately cover the protective layer, water can easily penetrate from the outside into the parts not covered by the lubricating layer, making the magnetic recording media susceptible to corrosion. Therefore, it is presumed that in the magnetic recording media of Comparative Examples 3 to 6, the corrosion resistance was insufficient, resulting in corrosion resistance test results of C or D.

[0399] In addition, compounds (ZC) and (ZD) have substituents bonded to the carbon atom to which the hydroxyl group of the terminal group is attached that contain ether bonds. In particular, compound (ZC), in which the glycerin structure contained in the terminal group is not an extended carbon structure, has excessive polarity, making the lubricating layer itself prone to absorbing water. As a result, it is presumed that the magnetic recording medium in Comparative Example 3, which used compound (ZC), was prone to corrosion, and that the corrosion resistance test result was D.

[0400] By using the lubricant for magnetic recording media containing the fluorine-containing ether compound of the present invention, it is possible to form a lubricating layer that provides a magnetic recording media with good levitation stability and corrosion resistance, even when the layer is thin.

[0401] 10 Magnetic recording medium 11 Substrate 12 Adhesion layer 13 Soft magnetic layer 14 First underlayer 15 Second underlayer 16 Magnetic layer 17 Protective layer 18 Lubricating layer

Claims

A fluorine-containing ether compound represented by the following formula (1). R １ -CH ２ -R ２ [-CH ２ -R ３ -CH ２ -R ２ ] ｘ -CH ２ -R ４ (1) (In equation (1), x represents an integer from 0 to 2. R ２ This is a perfluoropolyether chain. If x is 1 or 2, there are (x+1) R ２ They may be partially or entirely the same, or they may be different. ３ This is a divalent linking group having 1 to 4 polar groups. When x is 2, there are two R ３ They may be the same, or they may be different. １ and R ４ Each of these is an independent terminal group having 1 to 4 polar groups and 1 to 50 carbon atoms. １ and R ４ At least one of them is a terminal group represented by the following formula (2). (In formula (2), a represents an integer from 0 to 2. a b and a c each independently represent an integer from 1 to 6. However, in a single structural unit, at least one of b and c is 1. One of d and e is 0, and the other represents an integer from 1 to 6. Ra, Rb, Rc, and a Rd each independently represent an alkyl group having 1 to 8 carbon atoms or a hydrogen atom. However, when e is 0, at least one of Ra, Rb, Rc, and a Rd is an alkyl group having 1 to 8 carbon atoms, and when e is from 1 to 6, Rc is a hydrogen atom, and at least one of Ra, Rb, and a Rd is an alkyl group having 1 to 8 carbon atoms.) 　 The fluorine-containing ether compound according to claim 1, wherein the terminal group represented by formula (2) is a terminal group represented by any of the following formulas (2-1) to (2-7). (In equation (2-1), d1 represents an integer from 1 to 6. Ra １ Rb represents an alkyl group with 1 to 8 carbon atoms. １ (This represents an alkyl group with 1 to 8 carbon atoms or a hydrogen atom.) (In equation (2-2), b2, c2, and d2 each independently represent integers from 1 to 6, where at least one of b2 and c2 is 1. Ra ２ Rb represents an alkyl group with 1 to 8 carbon atoms. ２ (This represents an alkyl group with 1 to 8 carbon atoms or a hydrogen atom.) (In equation (2-3), d3 represents an integer from 1 to 6. Rc ３ (This represents an alkyl group with 1 to 8 carbon atoms.) (In equation (2-4), b4, c4, and d4 each independently represent integers from 1 to 6, where at least one of b4 and c4 is 1. Rc ４ (This represents an alkyl group with 1 to 8 carbon atoms.) (In equation (2-5), b5, c5, and d5 each independently represent integers from 1 to 6, where at least one of b5 and c5 is 1. Rd ５ (This represents an alkyl group with 1 to 8 carbon atoms.) (In equation (2-6), b6, c6, and d6 each independently represent an integer from 1 to 6, where at least one of b6 and c6 is 1. Ra ６ and Rd ６ Each of these independently represents an alkyl group having 1 to 8 carbon atoms, and Rb ６ (This represents an alkyl group with 1 to 8 carbon atoms or a hydrogen atom.) (In equation (2-7), b7, c7, and d7 each independently represent integers from 1 to 6, where at least one of b7 and c7 is 1. Rc ７ and Rd ７ Each of these independently represents an alkyl group having 1 to 8 carbon atoms. (In equation (2-8), b8, c8, and e8 each independently represent integers from 1 to 6, where at least one of b8 and c8 is 1. Rd ８ (This represents an alkyl group with 1 to 8 carbon atoms.) 　 R in formula (1) １ and R ４ The fluorine-containing ether compound according to claim 1 or claim 2, wherein both of them are independently terminal groups represented by formula (2). 　 R in formula (1) １ and R ４ The fluorine-containing ether compound according to claim 3, wherein the same 　 R in formula (1) １ and R ４ Only one of them is the terminal group represented by formula (2), The fluorine-containing ether compound according to claim 1 or claim 2, wherein the other end group is represented by the following formula (3). -O-[M] ｍ -[N] ｎ -[P] ｐ -[Q] (3) (In formula (3), m represents an integer from 0 to 3, and n and p each independently represent 0 or 1. Each of the m [M] is independently a divalent linking group represented by the following formula (3M). The n [N] are divalent linking groups represented by the following formula (3N). The p [P] are divalent linking groups represented by the following formula (3P). [Q] is a polar group, a halogeno group, a monovalent aliphatic organic group having 1 to 30 carbon atoms containing at least one ether oxygen atom, an alkyl group having 1 to 30 carbon atoms, an alkenyl group having 2 to 30 carbon atoms, an alkynyl group having 2 to 30 carbon atoms, an organic group having 6 to 30 carbon atoms containing an aromatic ring, or a hydrogen atom. In formula (3), the order of the m [M], n [N], and p [P] may be changed. However, the total number of polar groups included in formula (3) is 1 to 4, and [P] and [Q] do not directly bond.) (In equation (3M), m1 and m2 each independently represent integers from 1 to 6, where at least one of m1 and m2 is 1. Equation (3M) is R on the left side.) ２ (It will be joined to the side.) (In equation (3N), the left side is R) ２ (It will be joined to the side.) (In equation (3P), p1 represents an integer from 0 to 6. Each of the p1 Rp in equation (3P) is independently -CH) ２ -, -CF ２ -, -CH(CH ３ )-,-C(CH ３ ) ２ It represents one of the following. Equation (3P) has R on the left. ２ (It will be joined to the side.) 　 The fluorine-containing ether compound according to claim 5, wherein [Q] in formula (3) is a monovalent aliphatic organic group having 1 to 30 carbon atoms, comprising at least one of a polar group, a halogeno group, and an ether oxygen atom, and the polar group is at least one selected from the group consisting of a hydroxyl group, a cyano group, a carboxamide group, and an acetamide group. 　 The fluorine-containing ether compound according to claim 5, wherein the terminal group represented by formula (3) is a terminal group represented by any of the following formulas (3-1) to (3-10). (In equation (3-1), m01 represents an integer from 1 to 2. Each of the m01 m11 and m21 independently represents an integer from 1 to 6. However, within a single structural unit, at least one of m11 and m21 is 1. q1 represents an integer from 1 to 6. X ３１ (This represents one of the following: a hydroxyl group, a cyano group, an acetamide group, or a carboxamide group.) (In equation (3-2), m02 represents an integer between 1 and 2. The two m02s m12 and m22 each independently represent an integer between 1 and 6. However, within a single structural unit, at least one of m12 and m22 is 1.) (In equation (3-3), m03 represents an integer from 1 to 2. The three m03 m13 and m23 each independently represent an integer from 1 to 6. However, within a single structural unit, at least one of m13 and m23 is 1. q3 represents an integer from 0 to 6. X ３３ (This represents one of the following groups: methyl group, vinyl group, ethynyl group, phenyl group, methoxyphenyl group, cyanophenyl group, carboxamidephenyl group, acetaminophenyl group, trifluoromethyl group, or pentafluoroethyl group.) (In equation (3-4), m24 represents an integer from 1 to 6. q4 represents an integer from 0 to 6. X ３４ (This represents one of the following groups: methyl group, vinyl group, ethynyl group, phenyl group, methoxyphenyl group, cyanophenyl group, carboxamidephenyl group, acetaminophenyl group, trifluoromethyl group, or pentafluoroethyl group.) (In equation (3-5), q5 represents an integer from 1 to 6. X ３５ (This represents one of the following: a hydroxyl group, a cyano group, an acetamide group, or a carboxamide group.) (In equation (3-6), q6 represents an integer from 0 to 6. X ３６ (This represents one of the following groups: methyl group, vinyl group, ethynyl group, phenyl group, methoxyphenyl group, trifluoromethyl group, or pentafluoroethyl group.) (In equation (3-7), p17 represents an integer from 1 to 6. p17 Rp ａ , Rp ｂ Each of these independently represents either a hydrogen atom or a methyl group. (In equation (3-8), p18 represents an integer from 1 to 6.) 　 In equation (1) above, x is 1 or 2, and x R ３ The fluorine-containing ether compound according to claim 1 or claim 2, wherein each of them is independently a divalent linking group represented by the following formula (4). -O-[S] ｓ -[T] ｔ -[U] ｕ -(4) (In equation (4), s represents an integer from 0 to 3, and t and u each independently represent 0 or 1. However, s and t cannot be 0 at the same time. Each of the s [S] is independently a divalent linking group represented by the following equation (4S). [T] is a divalent linking group represented by the following equation (4T). [U] is a divalent linking group represented by the following equation (4U). In equation (4), the order of the s [S], t [T], and u [U] may be changed. However, the total number of polar groups included in equation (4) is between 1 and 4.) (In formula (4S), s1 and s2 each independently represent integers from 1 to 6, where at least one of s1 and s2 is 1. In formula (4S), the left side is bonded to the oxygen atom side in formula (4).) (In equation (4T), t1 represents an integer between 0 and 4. In equation (4T), the left side is bonded to the oxygen atom in equation (4).) (In equation (4U), u1 represents an integer from 0 to 6. Each of the u1 Ru in equation (4U) is independently -CH) ２ -, -CF ２ -, -CH(CH ３ )-,-C(CH ３ ) ２ This represents either of the following. In formula (4U), the left side is bonded to the oxygen atom in formula (4). The fluorine-containing ether compound according to claim 8, wherein the divalent linking group represented by formula (4) is a divalent linking group represented by any of the following formulas (4-1) to (4-9). (In equation (4-1), s11 represents an integer from 1 to 6, and s21 represents an integer from 1 to 6, provided that at least one of s11 and s21 is 1.) (In equation (4-2), s02 represents an integer between 2 and 3.) (In equation (4-3), t13 represents an integer between 0 and 4.) (In equation (4-4), s14 represents an integer from 1 to 6.) (In equation (4-5), s15 represents an integer from 1 to 6, and s25 represents an integer from 1 to 6.) (In equation (4-6), s16 represents an integer from 1 to 6, and s26 represents an integer from 1 to 6, provided that at least one of s16 and s26 is 2 or greater.) (In equation (4-7), s17 represents an integer between 1 and 6, and s27 represents an integer between 1 and 6, provided that at least one of s17 and s27 is 2 or greater.) (In equation (4-8), u18 represents an integer from 0 to 6. u18 Ru ａ Ru ｂ Each of these independently represents either a hydrogen atom or a methyl group. (In equation (4-9), u19 represents an integer from 1 to 6.) 　 The (x+1) Rs in equation (1) above ２ The fluorine-containing ether compound according to claim 1 or claim 2, wherein each is independently a perfluoropolyether chain represented by the following formula (5). -(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 - (5) (In formula (5), w2, w3, w4, and w5 represent the average degree of polymerization and each independently represents 0 to 20. However, all of w2, w3, w4, and w5 do not simultaneously become 0. w1 and w6 are average values representing the number of ２ CF ２ O), (CF ２ CF ２ O), (CF ２ CF ２ CF ２ O), (CF ２ CF ２ CF ２ CF ２ O) has no particular limitation in the sequence order.) 　 The fluorine-containing ether compound according to claim 10, wherein the perfluoropolyether chain represented by formula (5) is one selected from the perfluoropolyether chains represented by the following formulas (5-1) to (5-4). -CF ２ -(OCF ２ CF ２ ) ｈ -(OCF ２ ) ｉ -OCF ２ - (5-1) (In formula (5-1), h and i represent the average degree of polymerization, where h is between 1 and 20, and i is between 0 and 20.) -CF ２ CF ２ -(OCF ２ CF ２ CF ２ ) ｊ -OCF ２ CF ２ - (5-2) (In formula (5-2), j represents the average degree of polymerization and is expressed as 1 to 15.) -CF ２ CF ２ CF ２ -(OCF ２ CF ２ CF ２ CF ２ ) ｋ -OCF ２ CF ２ CF ２ - (5-3) (In formula (5-3), k represents the average degree of polymerization and is expressed as 1 to 10.) -(CF ２ ) ｗ７ -O-(CF ２ CF ２ CF ２ O) ｗ８ -(CF ２ CF ２ O) ｗ９ -(CF ２ ) ｗ１０ - (5-4) (In formula (5-4), w8 and w9 represent the average degree of polymerization and each independently represents 1 to 20. w7 and w10 are CF ２ This represents the average number of units, each independently representing 1 to 2. A fluorine-containing ether compound according to claim 1 or claim 2, wherein the number-average molecular weight is in the range of 500 to 10,000. 　 A compound represented by one of the following formulas (AA) to (CE): Rf in compounds represented by the following formulas (AA) to (AZ), (BD) to (BG), and (CA) to (CE) ２ , Rf in the compounds represented by the following formulas (BA) and (BB) １ , Rf in the compound represented by the following formula (BC) ３ The fluorine-containing ether compound according to claim 1, wherein each of the following is a perfluoropolyether chain represented by the following formula. (Rf in equation (AA)) ２ In this case, j represents the average degree of polymerization and is expressed as 1 to 15. (Rf in equation (AB)) ２ In this case, j represents the average degree of polymerization and is expressed as 1 to 15. (Rf in equation (AC)) ２ In this case, j represents the average degree of polymerization and is expressed as 1 to 15. (Rf in equation (AD)) ２ In this case, j represents the average degree of polymerization and is expressed as 1 to 15. (Rf in equation (AE)) ２ In this case, j represents the average degree of polymerization and is expressed as 1 to 15. (Rf in equation (AF)) ２ In this case, j represents the average degree of polymerization and is expressed as 1 to 15. (Rf in equation (AG)) ２ In this case, j represents the average degree of polymerization and is expressed as 1 to 15. (Rf in equation (AH)) ２ In this case, j represents the average degree of polymerization and is expressed as 1 to 15. (Rf in equation (AI)) ２ In this case, j represents the average degree of polymerization and is expressed as 1 to 15. (Rf in formula (AJ)) ２ In this case, j represents the average degree of polymerization and is expressed as 1 to 15. (Rf in equation (AK)) ２ In this case, j represents the average degree of polymerization and is expressed as 1 to 15. (Rf in equation (AL)) ２ In this case, j represents the average degree of polymerization and is expressed as 1 to 15. (Rf in equation (AM)) ２ In this case, j represents the average degree of polymerization and is expressed as 1 to 15. (Rf in equation (AN)) ２ In this case, j represents the average degree of polymerization and is expressed as 1 to 15. (Rf in equation (AO)) ２ In this case, j represents the average degree of polymerization and is expressed as 1 to 15. (Rf in equation (AP)) ２ In this case, j represents the average degree of polymerization and is expressed as 1 to 15. (Rf in equation (AQ)) ２ In this case, j represents the average degree of polymerization and is expressed as 1 to 15. (Rf in equation (AR)) ２ In this case, j represents the average degree of polymerization and is expressed as 1 to 15. (Rf in equation (AS)) ２ In this case, j represents the average degree of polymerization and is expressed as 1 to 15. (Rf in equation (AT)) ２ In this case, j represents the average degree of polymerization and is expressed as 1 to 15. (Rf in equation (AU)) ２ In this case, j represents the average degree of polymerization and is expressed as 1 to 15. (Rf in equation (AV)) ２ In this case, j represents the average degree of polymerization and is expressed as 1 to 15. (Rf in equation (AW)) ２ In this case, j represents the average degree of polymerization and is expressed as 1 to 15. (Rf in equation (AX)) ２ In this case, j represents the average degree of polymerization and is expressed as 1 to 15. (Rf in equation (AY)) ２ In this case, j represents the average degree of polymerization and is expressed as 1 to 15. (Rf in equation (AZ)) ２ In this case, j represents the average degree of polymerization and is expressed as 1 to 15. (Rf in formula (BA)) １ In this diagram, h and i represent the average degree of polymerization, where h ranges from 1 to 20 and i ranges from 0 to 20. (Rf in equation (BB)) １ In this diagram, h and i represent the average degree of polymerization, where h ranges from 1 to 20 and i ranges from 0 to 20. (Rf in equation (BC)) ３ In this case, k represents the average degree of polymerization and is expressed as a value between 1 and 10. (Rf in equation (BD)) ２ In this case, j represents the average degree of polymerization and is expressed as 1 to 15. (Rf in equation (BE)) ２ In this case, j represents the average degree of polymerization and is expressed as 1 to 15. (Rf in equation (BF)) ２ In this case, j represents the average degree of polymerization and is expressed as 1 to 15. (Rf in formula (BG)) ２ In this case, j represents the average degree of polymerization and is expressed as 1 to 15. (The two Rf in equation (CA) ２ In this, j represents the average degree of polymerization and is expressed as 1 to 15. Two Rf ２ In this case, j may be the same or different. (The two Rf in equation (CB) ２ In this, j represents the average degree of polymerization and is expressed as 1 to 15. Two Rf ２ In this case, j may be the same or different. (The two Rf in equation (CC) ２ In this, j represents the average degree of polymerization and is expressed as 1 to 15. Two Rf ２ In this case, j may be the same or different. (The two Rf in equation (CD) ２ In this, j represents the average degree of polymerization and is expressed as 1 to 15. Two Rf ２ In this case, j may be the same or different. (The three Rf in equation (CE) ２ In this, j represents the average degree of polymerization and is expressed as 1 to 15. Three Rf ２ In this case, j may be different in each instance, or some or all of them may be the same. 　 A lubricant for magnetic recording media comprising the fluorine-containing ether compound according to claim 1 or claim 2. 　 A magnetic recording medium having at least a magnetic layer, a protective layer, and a lubricating layer sequentially provided on a substrate, The lubricating layer comprises a fluorine-containing ether compound according to claim 1 or claim 2, wherein the magnetic recording medium is a magnetic recording medium. 　 The magnetic recording medium according to claim 15, wherein the average thickness of the lubricating layer is 0.5 nm to 2.0 nm.

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