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

Abstract

This fluorine-containing ether compound is represented by the following formula. R1-CH2-R2[-CH2-R3-CH2-R2]x-CH2-R4 (x is 1 or 2. R2 is a perfluoropolyether chain. R3 is represented by formula (2). R1 and R4 are terminal groups having 1-50 carbon atoms and having 1-4 polar groups. In formula (2), a1 and a2 are 0 to 5.b is 0 or 1. Y is an acyclic saturated hydrocarbon group having 2-8 carbon atoms.)

Description

[Technical Field]

[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. 2022-158422, filed on September 30, 2022, the contents of which are incorporated herein by reference. [Background technology]

[0002] In order to increase the recording density in magnetic recording and reproducing devices, development of magnetic recording media suitable for high recording densities is underway. Conventional magnetic recording media include those in which a recording layer is formed on a substrate and a protective layer made of carbon or the like is formed on the recording layer. The protective layer protects the information recorded on the recording layer and improves the sliding properties of the magnetic head. However, simply providing a protective layer on the recording layer does not provide sufficient durability for the magnetic recording medium. For this reason, a lubricating layer is generally formed by applying a lubricant to the surface of the protective layer.

[0003] As lubricants used in forming the lubricating layer of magnetic recording media, for example, those containing compounds having polar groups such as hydroxyl groups or amino groups at the end of a fluorine-based polymer having a repeating structure containing -CF2- have been proposed.

[0004] For example, Patent Documents 1 and 2 disclose fluorine-containing ether compounds having a skeleton in which two perfluoropolyether chains are linked via divalent linking groups in which methylene groups (-CH-) are linked to both ends of a glycerin structure (-O-CH-CH(OH)-CH-O-), and in which terminal groups that are organic groups having polar groups are linked to both ends via methylene groups.

[0005] Patent Documents 3 and 4 disclose fluorine-containing ether compounds having a skeleton containing a methylene group (-CH2-) and a group in which one hydrogen atom of the methylene group is substituted with a hydroxyl group (-CH(OH)-), in which two perfluoropolyether chains are linked via a divalent linking group having two hydroxyl groups, and in which terminal groups, which are organic groups having polar groups, are linked to both ends of the skeleton via the methylene groups.

[0006] Patent Document 5 discloses a fluorine-containing ether compound having a skeleton containing a methylene group (-CH2-) and a group in which one hydrogen atom of the methylene group is substituted with a hydroxyl group (-CH(OH)-), in which two or three perfluoropolyether chains are linked via a divalent linking group having two hydroxyl groups, and in which terminal groups that are organic groups having polar groups are linked to both ends of the skeleton via the methylene groups.

[0007] Patent Documents 6 and 7 disclose fluorine-containing ether compounds having a skeleton in which two perfluoropolyether chains are linked via a divalent linking group containing a benzene ring or an alicyclic structure, and in which terminal groups that are organic groups having polar groups are linked to both ends of the skeleton via methylene groups (-CH-).

[0008] Patent Document 8 discloses a fluorine-containing ether compound in which perfluoropolyether chains are bonded to both ends of a chain structure consisting of difluoromethylene groups (-CF2-) via linking groups containing at least one polar group, and a structural unit having a hydroxyl group is bonded to the end of the perfluoropolyether chain. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] US Patent No. 10540997 (B) [Patent Document 2] WO 2021 / 251335(A) [Patent Document 3] WO 2021 / 020066(A) [Patent Document 4] Japanese Patent No. 6804981 (B) [Patent Document 5] US Patent No. 10262685 (B) [Patent Document 6] WO 2021 / 065380(A) [Patent Document 7] WO 2022 / 113854(A) [Patent Document 8] WO 2018 / 159250(A) Summary of the Invention [Problem to be solved by the invention]

[0010] In recent years, in order to increase the capacity of magnetic recording media, there has been a demand for further reduction in magnetic spacing (the distance between the magnetic head and the magnetic layer of the magnetic recording medium), which has led to a demand for thinner lubricating layers in magnetic recording media. However, reducing the thickness of the lubricating layer generally tends to reduce the corrosion resistance of the magnetic recording medium. Furthermore, if the lubricating layer is made thinner, spin-off (a phenomenon in which the lubricant scatters or evaporates due to centrifugal force and heat generated by the rotation of the magnetic recording medium) occurs, and the lubricating layer cannot maintain a sufficient thickness to fulfill its function.

[0011] The present invention has been made in view of the above circumstances, and aims to provide a fluorine-containing ether compound that can form a lubricating layer that has excellent corrosion resistance and can suppress spin-off, 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 magnetic recording media which contains the fluorine-containing ether compound of the present invention and is capable of forming a lubricating layer which has good corrosion resistance and a high spin-off suppressing effect. Another object of the present invention is to provide a magnetic recording medium having a lubricating layer containing the fluorinated ether compound of the present invention, which has good corrosion resistance and a high spin-off suppressing effect. [Means for solving the problem]

[0012] The present invention includes the following aspects.

[0013] [1] A fluorine-containing ether compound represented by the following formula (1): R 1 -CH2-R 2 [-CH2-R 3 -CH2-R 2 ] x -CH2-R 4 (1) (In formula (1), x represents 1 or 2. R 2 is a perfluoropolyether chain. (x+1) R 2 may be the same in part or in whole, or may be different from each other. 3 is a divalent linking group represented by the following formula (2): When x is 2, two R 3 may be the same or different. 1 and R 4 R is a terminal group having 1 to 4 polar groups and 1 to 50 carbon atoms. 1 and R 4 may be the same or different.)

[0014] [ka] In formula (2), a1 and a2 represent integers of 0 to 5. a1 and a2 may be the same or different, and at least one of a1 and a2 is 1 or greater. b represents 0 or 1. Y represents an acyclic divalent saturated hydrocarbon group having 2 to 8 carbon atoms. The saturated hydrocarbon group is a partially fluorinated saturated hydrocarbon group that does not contain an ether oxygen atom between carbon atoms, or a non-fluorinated saturated hydrocarbon group that may contain an ether oxygen atom between carbon atoms and may have only one polar group. However, when the non-fluorinated saturated hydrocarbon group has the polar group, the polar group is bonded to a carbon atom other than the bonding terminal of Y. The oxygen atom at the left terminal of formula (2) is R in formula (1).1 The oxygen atom at the right end is bonded to the methylene group on the side of the 4 It bonds to the methylene group on the side.)

[0015] [2] The fluorine-containing ether compound according to [1], wherein the formula (2) is a linking group represented by any one of the following formulae (2-1) to (2-5):

[0016] [ka] In formula (2-1), a11 and a12 represent integers of 0 to 5. a11 and a12 may be the same or different. The total value of a11 and a12 is 1 to 6. c represents an integer of 2 to 8. c R a and R b Each independently represents a hydrogen atom or a methyl group. a R b The total number of carbon atoms contained in the R 1 The oxygen atom at the right end is bonded to the methylene group on the side of the 4 It bonds to the methylene group on the side.) In formula (2-2), a21 and a22 represent integers of 0 to 5. a21 and a22 may be the same or different. The sum of a21 and a22 is 1 to 6. d represents an integer of 2 to 4. d R c Each independently represents -CH2CH2-, -CH2CH2CH2-, -CH(CH3)CH2-, or -CH2CH(CH3)-. d R c The total number of carbon atoms contained in formula (2-2) is 4 to 8. The oxygen atom at the left end of formula (2-2) is R 1 The oxygen atom at the right end is bonded to the methylene group on the side of the 4 It bonds to the methylene group on the side.) In formula (2-3), a31 and a32 represent integers of 0 to 5. a31 and a32 may be the same or different. The sum of a31 and a32 is 1 to 6. e represents an integer of 1 to 6. The oxygen atom at the left terminal of formula (2-3) is R 1 The oxygen atom at the right end is bonded to the methylene group on the side of the 4 It bonds to the methylene group on the side.) In formula (2-4), a41 and a42 represent integers of 1 to 5. a41 and a42 may be the same or different. The total value of a41 and a42 is 2 to 6. f1 and f2 represent integers of 1 to 6. f1 and f2 may be the same or different, and the total value of f1 and f2 is 2 to 7. The oxygen atom at the left terminal of formula (2-4) is R 1 The oxygen atom at the right end is bonded to the methylene group on the side of the 4 It bonds to the methylene group on the side.) In formula (2-5), a51 and a52 represent integers of 0 to 5. a51 and a52 may be the same or different. The total value of a51 and a52 is 1 to 6. The oxygen atom at the left terminal of formula (2-5) is R 1 The oxygen atom at the right end is bonded to the methylene group on the side of the 4 It bonds to the methylene group on the side.)

[0017] [3] R in the formula (1) 1 and R 4 are each independently a terminal group represented by the following formula (3):

[0018] [ka] (In formula (3), l represents an integer of 1 to 3. l m's each independently represent an integer of 1 to 6. l n's each independently represent an integer of 1 to 6. In one repeating unit, at least one of m and n is 1. A represents an alkyl group which may have a polar group, an organic group containing a carbon-carbon unsaturated bond which may have a polar group, or a hydrogen atom.)

[0019] [4] R in the formula (1) 1 and R 4 are each independently a terminal group represented by the following formula (3-1) or (3-2):

[0020] [ka] (In formula (3-1), p represents an integer of 0 to 3, q ​​represents an integer of 0 to 2, and r represents an integer of 1 to 5. The total value of p and r is 1 to 5. B represents a polar group.) (In formula (3-2), s represents an integer of 0 to 2, and t represents an integer of 1 to 5.)

[0021] [5] R in the formula (1) 1 and R 4 The fluorine-containing ether compound according to any one of [1] to [4], wherein [6] R in the formula (1) 1 and the polar group R 4 The fluorine-containing ether compound according to any one of [1] to [5], wherein the total number of polar groups contained in the above is 2 to 6. [7] R in the formula (1) 1 and the polar group R 3 and the polar group R 4 The fluorine-containing ether compound according to any one of [1] to [6], wherein all of the polar groups are hydroxyl groups.

[0022] [8] (x+1) R in the formula (1) 2are each independently a perfluoropolyether chain represented by the following formula (4): -(CF2) w1 -O-(CF2O) w2 -(CF2CF2O) w3 -(CF2CF2CF2O) w4 -(CF2CF2CF2CF2O) w5 -(CF2) w6 - (4) (In formula (4), w2, w3, w4, and w5 represent average degrees of polymerization and each independently represent 0 to 20. However, w2, w3, w4, and w5 cannot all be 0 at the same time. w1 and w6 represent average values ​​representing the number of CF2 and each independently represent 1 to 3. There are no particular restrictions on the arrangement order of the repeating units (CF2O), (CF2CF2O), (CF2CF2CF2O), and (CF2CF2CF2CF2O) in formula (4).)

[0023] [9] (x+1) R in the formula (1) 2 are each independently any one selected from perfluoropolyether chains represented by the following formulae (4-1) to (4-4): -CF2-(OCF2CF2) h -(OCF2) i -OCF2- (4-1) (In formula (4-1), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20.) -CF2CF2-(OCF2CF2CF2) j -OCF2CF2- (4-2) (In formula (4-2), j represents the average degree of polymerization and represents 1 to 15.) -CF2CF2CF2-(OCF2CF2CF2CF2) k -OCF2CF2CF2- (4-3) (In formula (4-3), k represents the average degree of polymerization and represents 1 to 10.) -(CF2) w7 -O-(CF2CF2CF2O) w8 -(CF2CF2O)w9 -(CF2) w10 - (4-4) (In formula (4-4), w8 and w9 represent the average degree of polymerization, each independently representing 1 to 20. w7 and w10 are average values ​​representing the number of CF2, each independently representing 1 to 2.)

[0024]

[10] The fluorinated ether compound according to any one of [1] to [9], which has a number average molecular weight in the range of 500 to 10,000.

[11] A lubricant for magnetic recording media, comprising the fluorine-containing ether compound according to any one of [1] to

[10] .

[0025]

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

[10] .

[13] The magnetic recording medium according to

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

[0026] The fluorine-containing ether compound of the present invention is a compound represented by the above formula (1), and is suitable as a material for a lubricant for a magnetic recording medium. The lubricant for magnetic recording media of the present invention contains the fluorine-containing ether compound of the present invention, and therefore can form a lubricating layer that has good corrosion resistance and a high spin-off suppressing effect.

[0027] 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 corrosion resistance, a high spin-off suppression effect, and excellent reliability and durability. Furthermore, since the magnetic recording medium of the present invention has a lubricating layer with good corrosion resistance and suppressed spin-off, the thickness of the lubricating layer can be made thinner, and the flying height of the magnetic head can be further reduced. [Brief explanation of the drawings]

[0028] [Figure 1] 1 is a schematic cross-sectional view showing an embodiment of a magnetic recording medium of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0029] In order to solve the above problems, the present inventors have conducted extensive research as described below. Conventionally, fluorine-containing ether compounds having polar groups such as hydroxyl groups at the terminals and center of a chain structure have been preferably used as materials for lubricants for magnetic recording media (hereinafter sometimes abbreviated as "lubricants") that are applied to the surface of a protective layer. The polar groups in the fluorine-containing ether compounds bond with active sites on the protective layer, improving the adhesion of the lubricating layer to the protective layer.

[0030] However, when a thin lubricating layer is formed on a protective layer using a lubricant containing a conventional fluorine-containing ether compound, it has been difficult to achieve a lubricating layer that has good corrosion resistance and a high spin-off suppression effect, as will be shown below.

[0031] When a fluorine-containing ether compound in which a divalent linking group having a hydroxyl group is arranged between a plurality of perfluoropolyether chains is used, the sterically bulky perfluoropolyether chains arranged on both sides of the divalent linking group inhibit the adsorption of the hydroxyl group of the divalent linking group to the protective layer.When the divalent linking group arranged between the perfluoropolyether chains has only one hydroxyl group, the perfluoropolyether chain inhibits the adsorption of the hydroxyl group of the divalent linking group to the protective layer, and the divalent linking group may not be involved in the interaction with the active site on the protective layer.

[0032] Furthermore, in a fluorine-containing ether compound in which a divalent linking group having a rigid structure is arranged between multiple perfluoropolyether chains, even if the divalent linking group has multiple hydroxyl groups, the hydroxyl groups of the divalent linking group may not be able to participate in the interaction with the active site on the protective layer. This is because the divalent linking group having a rigid structure cannot move freely, and therefore, when the perfluoropolyether chains arranged on both sides of the divalent linking group undergo molecular motion, they may move in conjunction with the perfluoropolyether chains and separate from the protective layer.

[0033] Furthermore, even in a fluorine-containing ether compound in which a flexible divalent linking group having multiple hydroxyl groups is arranged between multiple perfluoropolyether chains, if the multiple hydroxyl groups of the divalent linking group are close to each other, the hydroxyl groups are likely to interact with each other within the molecule. As a result, the hydroxyl groups of the divalent linking group arranged between the perfluoropolyether chains are less likely to be involved in interactions with polar groups contained in other fluorine-containing ether compound molecules present in the lubricating layer.

[0034] In this way, in the fluorine-containing ether compound contained in the lubricant, <1> Interaction with active sites on the protective layer, or <2> If there is a polar group that is not involved in the interaction with the polar group contained in other fluorine-containing ether compounds that exist in the lubricating layer, the water that causes corrosion is easily taken in near this polar group.In addition, the adhesion between the lubricating layer and the protective layer is insufficient, and the lubricant in the lubricating layer is easily scattered or evaporated by the centrifugal force and heat generated by the rotation of the magnetic recording medium.Therefore, the polar group in the fluorine-containing ether compounds that are contained in the lubricating layer is easily dispersed or evaporated by the above-mentioned <1> or <2> If the lubricating layer is not easily involved in the interaction, the corrosion resistance and spin-off suppression effect of the lubricating layer will be poor.

[0035] Therefore, the present inventors have investigated the relationship between the polar group in the fluorine-containing ether compound contained in the lubricating layer and the above-mentioned <1> and <2> We conducted extensive research, focusing on the interaction between these two. As a result, they found that a fluorine-containing ether compound having a divalent linking group linking multiple perfluoropolyether chains via a methylene group (-CH2-) has a structure represented by formula (2) consisting of two specific unit structures and a specific linking structure disposed between them, and has terminal groups having polar groups at both ends of the molecule.

[0036] The two unit structures contained in the divalent linking group represented by formula (2) are each formed by bonding, from the terminal side of the divalent linking group, an ether oxygen atom (-O-), a methylene group (-CH2-), and a methylene group in which one hydrogen atom is substituted with a hydroxyl group (-CH(OH)-). The linking structure disposed between the two unit structures is formed by bonding an alkylene group having 1 to 6 carbon atoms to each unit structure, and a linking group containing an ether oxygen atom ("-O-(-YO-) in formula (2)") disposed therebetween. b -(b is 0 or 1)). At least one of the two alkylene groups in the linking structure has 2 to 6 carbon atoms. The linking group containing an ether oxygen atom has only an ether oxygen atom, or has an acyclic saturated hydrocarbon group having 2 to 8 carbon atoms (Y in formula (2)) positioned between two ether oxygen atoms. When the acyclic saturated hydrocarbon group is a non-fluorinated saturated hydrocarbon group, it may have only one polar group. The fluorine-containing ether compound having a divalent linking group represented by formula (2) has the following actions and functions (a) to (d):

[0037] (a) Each of the two unit structures has a polar hydroxyl group. Furthermore, if the linking group containing an ether oxygen atom in the linking structure between the two unit structures contains an acyclic, non-fluorinated saturated hydrocarbon group (Y in formula (2)), and the saturated hydrocarbon group has only one polar group, the linking group between the two unit structures also has one polar group. Therefore, the divalent linking group represented by formula (2) has two or three polar groups that can participate in interactions with active sites on the protective layer. Therefore, even if some of the polar groups contained in the divalent linking group represented by formula (2) are prevented from adsorbing to the protective layer by the sterically bulky perfluoropolyether chains located on both sides of the divalent linking group represented by formula (2), the divalent linking group represented by formula (2) can participate in interactions with active sites on the protective layer.

[0038] (b) In each unit structure, an ether oxygen atom that imparts flexibility, a methylene group that imparts rigidity, and a methylene group in which one hydrogen atom is substituted with a hydroxyl group are arranged in this order from the perfluoropolyether chain side. In addition, the linking structure arranged between two unit structures is two alkylene groups having 1 to 6 carbon atoms that impart rigidity, and a linking group containing an ether oxygen atom that imparts flexibility ("-O-(-YO-)" in formula (2)) arranged between them. b -(b is 0 or 1)), and at least one of the two alkylene groups has 2 to 6 carbon atoms. The linking group containing an ether oxygen atom is either an ether oxygen atom alone, which provides flexibility, or an acyclic saturated hydrocarbon group having 2 to 8 carbon atoms (Y in formula (2)) positioned between two ether oxygen atoms. Therefore, the divalent linking group represented by formula (2) has appropriate flexibility, and the movement of each unit structure is not hindered by the highly rigid structure in the divalent linking group represented by formula (2). As a result, the hydroxyl groups of each unit structure can move freely and independently, easily interacting with the active sites on the protective layer or with polar groups contained in other fluorine-containing ether compounds present in the lubricating layer.

[0039] (c) The hydroxyl groups of each unit structure are connected by a linking structure between two unit structures, which has two alkylene groups having 1 to 6 carbon atoms (at least one of the two alkylene groups has 2 to 6 carbon atoms), and a linking group containing an ether oxygen atom ("-O-(-YO-) in formula (2)) between them. b -(b is 0 or 1)" and are sufficiently separated. More specifically, when the linking group containing an ether oxygen atom is composed solely of ether oxygen atoms, there are at least six atoms between the hydroxyl groups of the two unit structures, including an alkylene group having 1 to 6 carbon atoms, an ether oxygen atom, and an alkylene group having 2 to 6 carbon atoms. Therefore, the hydroxyl groups of the two unit structures are unlikely to interact with each other.

[0040] Furthermore, when the linking group containing an ether oxygen atom has a non-cyclic saturated hydrocarbon group having 2 to 8 carbon atoms and no polar group disposed between the two ether oxygen atoms, two or more ether oxygen atoms that impart flexibility are present between the hydroxyl groups of the two unit structures. However, in this case, there are at least eight atoms between the hydroxyl groups of the two unit structures, including the alkylene group having 1 to 6 carbon atoms, the atoms in the linking group containing the ether oxygen atom, and the alkylene group having 2 to 6 carbon atoms. Moreover, the non-cyclic saturated hydrocarbon group having 2 to 8 carbon atoms and no polar group is suitably bulky and is disposed between the two ether oxygen atoms. For these reasons, even if two or more ether oxygen atoms are present between the two unit structures, the hydroxyl groups of the two unit structures are unlikely to interact with each other.

[0041] Furthermore, when the linking group containing an ether oxygen atom has an acyclic, non-fluorinated saturated hydrocarbon group having 2 to 8 carbon atoms disposed between two ether oxygen atoms, and the saturated hydrocarbon group has only one polar group, the polar group is bonded to a carbon atom other than the bond terminal of the saturated hydrocarbon group. In this case, the polar group in the linking group containing an ether oxygen atom and the hydroxyl group in at least one of the unit structures are sufficiently separated. Specifically, there are at least six atoms between the polar group in the linking group containing an ether oxygen atom and the hydroxyl group in at least one of the unit structures, including the alkylene group having 2 to 6 carbon atoms and the atoms in the linking group containing an ether oxygen atom. Therefore, the polar group in the linking group containing an ether oxygen atom and the hydroxyl group in at least one of the unit structures are unlikely to interact with each other. For these reasons, the hydroxyl groups contained in the divalent linking group represented by formula (2) are unlikely to interact with each other within the same fluorinated ether compound molecule.

[0042] (d) The linking structure disposed between the two unit structures has two alkylene groups each having 1 to 6 carbon atoms, and at least one of the two alkylene groups in the linking structure has 2 to 6 carbon atoms and imparts hydrophobicity. Therefore, the divalent linking group represented by formula (2) can suppress the absorption of water, which causes corrosion.

[0043] The fluorine-containing ether compound having a divalent linking group represented by formula (2) has the above actions and functions (a) to (c), and therefore, <1> and <2> It is presumed that the polar group contained in the divalent linking group represented by formula (2) and the above <1> The interaction between the polar group contained in the divalent linking group represented by formula (2) and the above contributes to improving the adhesion between the lubricating layer and the protective layer. <2> The interaction is an intermolecular interaction with other fluorine-containing ether compounds, and contributes to the formation of a dense film that is difficult to separate from the protective layer. Therefore, the lubricating layer containing the above fluorine-containing ether compound is dense and difficult to separate, has high adhesion to the protective layer, and is unlikely to cause spin-off. In addition, <1> and <2> The presence of polar groups that are not involved in the interaction makes it difficult for water to be taken up, resulting in good corrosion resistance. Furthermore, the fluorine-containing ether compound having a divalent linking group represented by formula (2) can provide the above action and function (d), and can therefore form a lubricating layer with good corrosion resistance.

[0044] Moreover, in the above-mentioned fluorine-containing ether compound, the perfluoropolyether chain is arranged between the terminal group having a polar group and the divalent linking group represented by formula (2).Therefore, the perfluoropolyether chain suppresses the intramolecular interaction between the polar group in the terminal group and the polar group in the divalent linking group, and the terminal group and the linking group can each independently interact with the protective layer.Therefore, two or three perfluoropolyether chains have terminal groups or linking groups at both ends that can interact with the protective layer.Therefore, the above-mentioned fluorine-containing ether compound can suppress the perfluoropolyether chain in the fluorine-containing ether compound from floating up and becoming bulky, and can form a thinner lubricating layer.In other words, the lubricating layer containing the above-mentioned fluorine-containing ether compound can maintain its function as a lubricating layer even when its thickness is reduced.

[0045] Furthermore, the present inventors have confirmed that by using a lubricant containing the above-mentioned fluorine-containing ether compound, it is possible to form a lubricating layer that has good corrosion resistance and a high spin-off suppression effect even when the thickness is thin, and have thus conceived the present invention.

[0046] The fluorine-containing ether compound, the lubricant for a magnetic recording medium, and the magnetic recording medium of the present invention will be described in detail below. However, the present invention is not limited to the following embodiments.

[0047] [Fluorine-containing ether compounds] The fluorine-containing ether compound of the present embodiment is represented by the following formula (1). R 1 -CH2-R 2 [-CH2-R 3 -CH2-R 2 ] x -CH2-R 4 (1) (In formula (1), x represents 1 or 2. R 2 is a perfluoropolyether chain. (x+1) R 2 may be the same in part or in whole, or may be different from each other. 3 is a divalent linking group represented by the following formula (2): When x is 2, two R 3 may be the same or different. 1 and R 4 R is a terminal group having 1 to 4 polar groups and 1 to 50 carbon atoms. 1 and R 4 may be the same or different.)

[0048] [ka] In formula (2), a1 and a2 represent integers of 0 to 5. a1 and a2 may be the same or different, and at least one of a1 and a2 is 1 or greater. b represents 0 or 1. Y represents an acyclic divalent saturated hydrocarbon group having 2 to 8 carbon atoms. The saturated hydrocarbon group is a partially fluorinated saturated hydrocarbon group that does not contain an ether oxygen atom between carbon atoms, or a non-fluorinated saturated hydrocarbon group that may contain an ether oxygen atom between carbon atoms and may have only one polar group. However, when the non-fluorinated saturated hydrocarbon group has the polar group, the polar group is bonded to a carbon atom other than the bonding terminal of Y. The oxygen atom at the left terminal of formula (2) is R in formula (1). 1 The oxygen atom at the right end is bonded to the methylene group on the side of the 4 It bonds to the methylene group on the side.)

[0049] The fluorine-containing ether compound of the present embodiment is, as represented by formula (1), 3 and a divalent linking group represented by R 2 The PFPE chain has a skeleton in which a perfluoropolyether chain (hereinafter sometimes referred to as a PFPE chain) represented by the formula: 1 The other end of the skeleton is connected via a methylene group to an end group represented by R 4 The terminal group shown in is attached.

[0050] In the fluorine-containing ether compound represented by formula (1), x is 1 or 2. In the fluorine-containing ether compound represented by formula (1), x is 1 or 2, so that R 2 The number of PFPE chains (x+1) represented by the formula (1) is 2 or 3. Therefore, in the fluorine-containing ether compound represented by the formula (1), unlike the compound having one PFPE chain, the number of adjacent R 2 Between them, there is a divalent linking group R represented by formula (2) 3are arranged. As a result, the fluorine-containing ether compound represented by formula (1) can form a lubricating layer that has excellent adhesion to the protective layer and is less likely to spin off, compared to, for example, a compound having one PFPE chain. Moreover, the fluorine-containing ether compound represented by formula (1) has molecules that are not too large and can move freely, compared to compounds having four or more PFPE chains. For this reason, the fluorine-containing ether compound represented by formula (1) can more easily wet and spread on the protective layer, compared to compounds having four or more PFPE chains, and can form a lubricating layer with a thin and uniform film thickness.

[0051] (R 3 a divalent linking group represented by In the fluorine-containing ether compound represented by formula (1), x R 3 is a divalent linking group represented by formula (2). The divalent linking group represented by formula (2) is composed of two unit structures and a linking structure disposed between them. The two unit structures contained in the divalent linking group represented by formula (2) are each formed by bonding, from the terminal side of the divalent linking group, an ether oxygen atom (-O-), a methylene group (-CH2-), and a methylene group in which one hydrogen atom is substituted with a hydroxyl group (-CH(OH)-). Therefore, R 3 is R 2 The ether oxygen atom in each unit structure provides the fluorine-containing ether compound represented by formula (1) with appropriate flexibility and increases the affinity between the hydroxyl group in each unit structure and the protective layer.

[0052] In the divalent linking group represented by formula (2), a1 and a2 represent integers of 0 to 5. a1 and a2 may be the same or different, and at least one of a1 and a2 is 1 or greater. Therefore, in the divalent linking group represented by formula (2), the linking structure disposed between two unit structures is an alkylene group having 1 to 6 carbon atoms (a1+1 in formula (2)) bonded to one unit structure, and a linking group containing an ether oxygen atom ("-O-(-YO-) in formula (2)"). b-(b is 0 or 1)") and an alkylene group having 1 to 6 carbon atoms (a2+1 in formula (2)) bonded to another unit structure, in this order, and at least one of the two alkylene groups has 2 to 6 carbon atoms.

[0053] In the divalent linking group represented by formula (2), the two alkylene groups in the linking structure disposed between the two unit structures each have one or more carbon atoms, and at least one of the alkylene groups has two or more carbon atoms (a1 and / or a2 in formula (2) is one or more). Therefore, the distance between the hydroxyl groups in the two unit structures is appropriate, allowing the hydroxyl groups in the two unit structures to move independently. Furthermore, alkylene groups having two to six carbon atoms have superior hydrophobicity compared to alkylene groups having one carbon atom. In the divalent linking group represented by formula (2), at least one of the two alkylene groups has two to six carbon atoms, which can prevent the generation of water that causes corrosion. In the divalent linking group represented by formula (2), it is preferable that both of the two alkylene groups have two or more carbon atoms (a1 and a2 in formula (2) are one or more). This is because the distance between the hydroxyl groups in each of the two unit structures becomes more appropriate, the hydrophobicity of the divalent linking group represented by formula (2) is further improved, and the corrosion resistance of the lubricating layer containing the fluorine-containing ether compound represented by formula (1) becomes better.

[0054] In the divalent linking group represented by formula (2), the two alkylene groups each have 6 or less carbon atoms (a1 and a2 in formula (2) are 5 or less), so that the linking structure arranged between the two unit structures is rigid, thereby preventing the movement of each unit structure from being hindered. Preferably, the two alkylene groups each have 4 or less carbon atoms (a1 and a2 in formula (2) are 3 or less).

[0055] In the divalent linking group represented by formula (2), b represents 0 or 1. That is, the linking group containing an ether oxygen atom ("-O-(-YO-) in formula (2))b -(b is 0 or 1)) is an ether oxygen atom (-O-) only (b=0 in formula (2)), or an acyclic saturated hydrocarbon group having 2 to 8 carbon atoms (Y in formula (2)) arranged between two ether oxygen atoms (b=1 in formula (2)). In the divalent linking group represented by formula (2), the distance between the hydroxyl groups in the unit structure is more likely to be appropriate, so the linking group containing an ether oxygen atom is preferably an acyclic saturated hydrocarbon group having 2 to 8 carbon atoms arranged between two ether oxygen atoms (b=1 in formula (2)). The acyclic saturated hydrocarbon group may be linear or branched. In the divalent linking group represented by formula (2), the linking group containing an ether oxygen atom possessed by the divalent linking group represented by formula (2) can be appropriately selected depending on the performance required of the lubricant containing the fluorine-containing ether compound, etc.

[0056] Since the number of carbon atoms in the acyclic saturated hydrocarbon group having 2 to 8 carbon atoms, which is Y in formula (2), is 2 or more, the distance between the hydroxyl groups in each of the two unit structures becomes appropriate when b in formula (2) is 1. The number of carbon atoms in the acyclic saturated hydrocarbon group, which is Y in formula (2), is preferably 3 or more, since this makes the distance between the hydroxyl groups in each unit structure more appropriate and further improves the corrosion resistance of the lubricant containing the fluorine-containing ether compound. Furthermore, when Y in formula (2) is an acyclic, non-fluorinated saturated hydrocarbon group, it may have only one polar group, provided that the polar group is bonded to a carbon atom other than the bond terminal of Y. In other words, the polar group is bonded to a carbon atom other than the terminal atoms of Y that are bonded to the oxygen atoms on both sides of Y in formula (2). Furthermore, since the number of carbon atoms of the non-cyclic saturated hydrocarbon group represented by Y in formula (2) is 8 or less, the movement of the two unit structures is prevented from being hindered due to the bulkiness of Y in formula (2).

[0057] Since Y in the divalent linking group represented by formula (2) is an acyclic saturated hydrocarbon group having 2 to 8 carbon atoms, the divalent linking group represented by formula (2) has high flexibility and is less likely to interfere with the movement of the unit structure, compared to, for example, a case where Y is a hydrocarbon group having an unsaturated bond. Since Y in the divalent linking group represented by formula (2) is an acyclic saturated hydrocarbon group having 2 to 8 carbon atoms, the fluidity of the divalent linking group represented by formula (2) is high and the movement of the unit structure is less likely to be hindered, compared to, for example, a case where Y is a hydrocarbon group having a cyclic structure.

[0058] When b is 1 in the divalent linking group represented by formula (2), the acyclic saturated hydrocarbon group having 2 to 8 carbon atoms (Y in formula (2)) contained therein is a partially fluorinated saturated hydrocarbon group or a non-fluorinated saturated hydrocarbon group. When Y in the divalent linking group represented by formula (2) is a partially fluorinated saturated hydrocarbon group, the hydrophilicity of the divalent linking group represented by formula (2) is reduced compared to when it is a non-fluorinated saturated hydrocarbon group. As a result, the induction of water, which causes corrosion, can be suppressed, resulting in a fluorine-containing ether compound that can form a lubricating layer with good corrosion resistance.

[0059] When Y in the divalent linking group represented by formula (2) is a partially fluorinated saturated hydrocarbon group, it does not contain an ether oxygen atom between carbon atoms for the following reasons: When the partially fluorinated saturated hydrocarbon group contains an ether oxygen atom between carbon atoms, the divalent linking group represented by formula (2) contains a PFPE chain, and the PFPE chain in the divalent linking group represented by formula (2) and R 2 This polar group is present between the PFPE chain in the divalent linking group represented by formula (2) and the PFPE chain represented by formula (3). 2 The PFPE chains represented by the formula (1) inhibit adsorption to the protective layer, making it difficult for the lubricating layer to interact with the active sites on the protective layer. As a result, the adhesion between the lubricating layer and the protective layer becomes insufficient.

[0060] When Y in the divalent linking group represented by formula (2) is a non-fluorinated saturated hydrocarbon group, it may contain an ether oxygen atom between carbon atoms or may have only one polar group, provided that the polar group is bonded to a carbon atom other than the bonding terminal of Y. When the saturated hydrocarbon group represented by Y in formula (2) is a non-fluorinated saturated hydrocarbon group containing an ether oxygen atom (-O-) between carbon atoms, Y has a more flexible structure. As a result, the hydroxyl groups in the two unit structures can move freely and independently, easily interacting with active sites on the protective layer or polar groups contained in other fluorinated ether compounds present in the lubricating layer.

[0061] When the saturated hydrocarbon group represented by Y in formula (2) is a non-fluorinated saturated hydrocarbon group having only one polar group, the polar group contained in Y in formula (2) and the hydroxyl group contained in each unit structure are arranged between a part of the saturated hydrocarbon group represented by Y in formula (2), an alkylene group having 1 to 6 carbon atoms (or an alkylene group having 2 to 6 carbon atoms), and an ether oxygen atom disposed between them. Therefore, the distance between the polar group contained in Y in formula (2) and the hydroxyl group contained in each unit structure is appropriate.

[0062] When the saturated hydrocarbon group represented by Y in formula (2) contains a polar group, the fluorine-containing ether compound can form a lubricating layer with even better adhesion between the lubricating layer and the protective layer. When the saturated hydrocarbon group represented by Y in formula (2) contains a polar group, the number of polar groups is only one. This prevents the fluorine-containing ether compound from becoming too hydrophilic and inducing water, which can cause corrosion.

[0063] Examples of polar groups that may be contained in the saturated hydrocarbon group represented by Y in formula (2) include a hydroxyl group (-OH), an amino group (-NH), a carboxyl group (-COOH), a formyl group (-(C=O)H), a carbonyl group (-CO-), a sulfo group (-SOH), a cyano group (-CN), and a group having an amide bond (-NR 7 COR 8 or -CONR9 R 10 ;R 7 , R 8 , R 9 and R 10 are each independently a hydrogen atom or an organic group. ) and the like. Among these, polar groups selected from the group consisting of hydroxyl groups, cyano groups, and groups having an amide bond are more preferred. This is because hydroxyl groups, cyano groups, and groups having an amide bond are chemically stable, and the lubricating layer containing a fluorine-containing ether compound having these polar groups does not deteriorate over the long term. In addition, hydroxyl groups, cyano groups, and groups having an amide bond are not too acidic, and therefore have little effect on corroding the substrate.

[0064] In the divalent linking group represented by formula (2), each of the two unit structures has one hydroxyl group. Furthermore, when the linking group containing an ether oxygen atom in the linking structure arranged between the two unit structures is a non-fluorinated acyclic saturated hydrocarbon group, the saturated hydrocarbon group may have one polar group. Therefore, the divalent linking group represented by formula (2) has two or three polar groups. Since the divalent linking group represented by formula (2) has two or more polar groups, sufficient interaction between the polar groups of the divalent linking group represented by formula (2) and the active sites on the protective layer is obtained. Therefore, the lubricating layer containing the fluorinated ether compound of this embodiment has high adhesion to the protective layer. Furthermore, since the divalent linking group represented by formula (2) contains three or fewer polar groups, the polarity of the fluorinated ether compound is too high, which causes aggregation and poor adhesion to the protective layer, thereby preventing spin-off.

[0065] The two or three polar groups in the divalent linking group represented by formula (2) easily interact with the active sites on the protective layer or with polar groups contained in other fluorine-containing ether compounds present in the lubricating layer. Furthermore, the divalent linking group represented by formula (2) has good hydrophobicity. For these reasons, the fluorine-containing ether compound represented by formula (1) can form a lubricating layer that has good adhesion between the lubricating layer and the protective layer, is less susceptible to spin-off, and has good corrosion resistance.

[0066] R 3 Formula (2) represented by the following formula (2-1) to (2-5) is preferably a linking group represented by any one of the following formulas (2-1) to (2-5).

[0067] [ka] In formula (2-1), a11 and a12 represent integers of 0 to 5. a11 and a12 may be the same or different. The total value of a11 and a12 is 1 to 6. c represents an integer of 2 to 8. c R a and R b Each independently represents a hydrogen atom or a methyl group. a R b The total number of carbon atoms contained in the R 1 The oxygen atom at the right end is bonded to the methylene group on the side of the 4 It bonds to the methylene group on the side.) In formula (2-2), a21 and a22 represent integers of 0 to 5. a21 and a22 may be the same or different. The sum of a21 and a22 is 1 to 6. d represents an integer of 2 to 4. d R c Each independently represents -CH2CH2-, -CH2CH2CH2-, -CH(CH3)CH2-, or -CH2CH(CH3)-. d R c The total number of carbon atoms contained in formula (2-2) is 4 to 8. The oxygen atom at the left end of formula (2-2) is R 1 The oxygen atom at the right end is bonded to the methylene group on the side of the 4 It bonds to the methylene group on the side.) In formula (2-3), a31 and a32 represent integers of 0 to 5. a31 and a32 may be the same or different. The sum of a31 and a32 is 1 to 6. e represents an integer of 1 to 6. The oxygen atom at the left terminal of formula (2-3) is R 1 The oxygen atom at the right end is bonded to the methylene group on the side of the 4 It bonds to the methylene group on the side.) In formula (2-4), a41 and a42 represent integers of 1 to 5. a41 and a42 may be the same or different. The total value of a41 and a42 is 2 to 6. f1 and f2 represent integers of 1 to 6. f1 and f2 may be the same or different, and the total value of f1 and f2 is 2 to 7. The oxygen atom at the left terminal of formula (2-4) is R 1 The oxygen atom at the right end is bonded to the methylene group on the side of the 4 It bonds to the methylene group on the side.) In formula (2-5), a51 and a52 represent integers of 0 to 5. a51 and a52 may be the same or different. The total value of a51 and a52 is 1 to 6. The oxygen atom at the left terminal of formula (2-5) is R 1 The oxygen atom at the right end is bonded to the methylene group on the side of the 4 It bonds to the methylene group on the side.)

[0068] The linking group represented by formula (2-1) is one in which b in formula (2) is 1, and Y in formula (2) is a non-fluorinated saturated hydrocarbon group that does not contain an ether oxygen atom between carbon atoms. In formula (2-1), c represents an integer of 2 to 8, and c (-CR a R b -) has a total of 2 to 8 carbon atoms.

[0069] c R in formula (2-1) a and R b Each independently represents a hydrogen atom or a methyl group. Therefore, the c (-CR a R bEach -) may be any of -CH2-, -CH(CH3)-, or -C(CH3)2-. When Y in formula (2) consists of only a plurality of -CH2-, it is easier to ensure the number of atoms between the hydroxyl groups in each of the two unit structures, and the distance between the two hydroxyl groups is more likely to be appropriate, compared to a branched Y with the same number of carbon atoms. Furthermore, when Y in formula (2) contains -CH(CH3)- and / or -C(CH3)2-, Y becomes appropriately bulky, and the interaction between the hydroxyl groups in each of the two unit structures can be effectively suppressed.

[0070] In the linking group represented by formula (2-1), since c is 2 or more, there are at least 9 atoms between the hydroxyl groups of the two unit structures, and the distance between the two hydroxyl groups is appropriate. Furthermore, since c is 2 or more, the hydrophobicity of the saturated hydrocarbon group is improved, and the corrosion resistance of the lubricating layer containing the fluorine-containing ether compound represented by formula (1) is improved. Also, c (-CR a R b The total number of carbon atoms contained in c (-CR a R b -) becomes more hydrophobic, and the lubricating layer containing the fluorine-containing ether compound represented by formula (1) becomes less likely to absorb water, which causes corrosion, resulting in better corrosion resistance. In addition, in the formula (2-1), c is 8 or less, and the number of carbon atoms contained in the saturated hydrocarbon group is c (-CR a R b Since the total number of carbon atoms contained in -) is 8 or less, the rigidity of the saturated hydrocarbon group can be prevented from interfering with the movement of the unit structure. c is preferably 4 or less.

[0071] In the linking group represented by formula (2-1), a11 and a12 represent integers of 0 to 5, and each is preferably an integer of 1 to 3. a11 and a12 may be the same or different. When a11 and a12 in formula (2-1) are the same, the fluorinated ether compound represented by formula (1) is easily produced, which is preferable. The total value of a11 and a12 is 1 to 6, and at least one of a11 and a12 is 1 or greater, similar to a1 and a2 in formula (2).

[0072] The linking group represented by formula (2-2) is one in which b in formula (2) is 1 and Y in formula (2) is a non-fluorinated saturated hydrocarbon group containing an ether oxygen atom between carbon atoms. d in formula (2-2) represents an integer of 2 to 4. d R c The total number of carbon atoms contained in is 4 to 8. c each independently represents -CH2CH2-, -CH2CH2CH2-, -CH(CH3)CH2- or -CH2CH(CH3)-, and is preferably -CH2CH2- or -CH2CH2CH2-, more preferably -CH2CH2-, since this provides flexibility for the unit structure to move freely.

[0073] In formula (2-2), d is 2 or more, and the number of carbon atoms contained in the saturated hydrocarbon group (d R c Since the total number of carbon atoms contained in R is 4 or more, the linking group represented by formula (2-2) is composed of an ether oxygen atom that provides flexibility and R c and a repeating structure (in formula (2-2), (-R c The fluorine-containing ether compound has a regular arrangement containing two or more -O-) groups. This makes it easier to obtain intermolecular interactions between the fluorine-containing ether compounds and interactions between the fluorine-containing ether compound and the protective layer, and the lubricating layer containing the fluorine-containing ether compound represented by formula (1) becomes denser and spin-off is suppressed.

[0074] In formula (2-2), d R cIn formula (2-2), d R c It is preferable that all of (-R c This is because the resulting molecule has a more regular arrangement of the hydroxy groups (—O—), making it easier to obtain intermolecular interactions.

[0075] In addition, d in formula (2-2) is 2 or more, and d R c Since the total number of carbon atoms contained in is 4 or more, there are at least 12 atoms between the hydroxyl groups of the two unit structures, and even if the saturated hydrocarbon group contains an ether oxygen atom between the carbon atoms, the distance between the two hydroxyl groups is appropriate. c Since the total number of carbon atoms in is 4 or more, there are d R c This improves the hydrophobicity of the linking group represented by formula (2-2), and improves the corrosion resistance of the lubricating layer containing the fluorine-containing ether compound represented by formula (1). c The total number of carbon atoms contained in may be 6 or more.

[0076] In formula (2-2), d is 4 or less, and the number of carbon atoms contained in the saturated hydrocarbon group (d R c Since the total number of carbon atoms contained in R is 8 or less, the rigidity of the saturated hydrocarbon group does not hinder the movement of the unit structure. d may be 3 or less. c The total number of carbon atoms contained in may be 6 or less.

[0077] In the linking group represented by formula (2-2), a21 and a22 represent integers of 0 to 5, and each is preferably an integer of 1 to 3. a21 and a22 may be the same or different. When a21 and a22 in formula (2-2) are the same, the fluorinated ether compound represented by formula (1) is easily produced, which is preferable. The total value of a21 and a22 is 1 to 6, and at least one of a21 and a22 is 1 or greater, similar to a1 and a2 in formula (2).

[0078] The linking group represented by formula (2-3) is a group in which b in formula (2) is 1, Y in formula (2) is a partially fluorinated saturated hydrocarbon group (-CH2-(CF2) in formula (2-3) e In formula (2-3), e represents an integer of 1 to 6. Therefore, the linking group represented by formula (2-3) contains a linear perfluoroalkyl chain having 1 to 6 carbon atoms, which reduces the affinity for water. When the linking group represented by formula (2-3) is present, the saturated hydrocarbon group containing a perfluoroalkyl chain (-CH2-(CF2) in formula (2-3)) contained between the two unit structures is e The -CH2-) reduces the polarity of the entire molecule and improves hydrophobicity, thereby reducing the affinity for water, which causes corrosion. As a result, the lubricating layer containing the fluorine-containing ether compound represented by formula (1) is prevented from taking in water, which causes corrosion, and has even better corrosion resistance.

[0079] In the linking group represented by formula (2-3), since e is 1 or more, there are at least 10 atoms between the hydroxyl groups of the two unit structures, and the distance between the two hydroxyl groups is appropriate. Furthermore, since e is 1 or more, the number of groups (-CF2-) in which hydrogen atoms of methylene groups are substituted with fluorine atoms is 1 or more, which reduces the affinity with water and reduces the affinity of the saturated hydrocarbon group (-CH2-(CF2) in formula (2-3)). e The hydrophobicity of the -CH2-) is improved. In formula (2-3), e is preferably 2 or more. In addition, since e in formula (2-3) is 6 or less, the rigidity of the saturated hydrocarbon group does not hinder the movement of the unit structure. In formula (2-3), e is preferably 4 or less.

[0080] In the linking group represented by formula (2-3), a31 and a32 represent integers of 0 to 5, and each is preferably an integer of 1 to 3. a31 and a32 may be the same or different. When a31 and a32 in formula (2-3) are the same, the fluorinated ether compound represented by formula (1) is easily produced, which is preferable. The total value of a31 and a32 is 1 to 6, and at least one of a31 and a32 is 1 or greater, similar to a1 and a2 in formula (2).

[0081] The linking group represented by formula (2-4) is a group in which b in formula (2) is 1, Y in formula (2) is a non-fluorinated saturated hydrocarbon group, and the saturated hydrocarbon group has only one polar group (-(CH2) in formula (2-4)). f1 -CH(OH)-(CH2) f2 -). The linking group represented by formula (2-4) has three hydroxyl groups, so that intermolecular interactions between the fluorine-containing ether compounds and interactions between the fluorine-containing ether compound and the protective layer are sufficiently obtained. Therefore, a lubricating layer containing a fluorine-containing ether compound having a linking group represented by formula (2-4) has high adhesion to the protective layer, is denser, and has reduced spin-off.

[0082] In formula (2-4), a41 and a42 each represent an integer of 1 to 5, preferably an integer of 1 to 3. a41 and a42 may be the same or different. When a41 and a42 in formula (2-4) are the same, the fluorinated ether compound represented by formula (1) is easily produced, which is preferable. The total value of a41 and a42 is 2 to 6.

[0083] In addition, f1 and f2 in formula (2-4) each represent an integer of 1 to 6, and are preferably integers of 1 to 3. f1 and f2 may be the same or different. The total value of f1 and f2 is 2 to 7.

[0084] In the linking group represented by formula (2-4), a41 and a42 are each 1 or more, and f1 and f2 are each 1 or more, so that the linking group is a saturated hydrocarbon group (-(CH2) in formula (2-4)). f1 -CH(OH)-(CH2) f2 The distance between the hydroxyl group in the linking group represented by formula (2-4) and the hydroxyl groups in each of the two unit structures is appropriate. That is, there are at least six atoms between the hydroxyl group in the saturated hydrocarbon group and the hydroxyl groups in each of the two unit structures. This prevents the hydroxyl groups in the linking group represented by formula (2-4) from aggregating within the molecule.

[0085] In the linking group represented by formula (2-4), a41 and a42 are each 5 or less, the sum of a41 and a42 is 6 or less, and f1 and f2 are each 6 or less, and the sum of f1 and f2 is 7 or less. Therefore, in the linking group represented by formula (2-4), the rigidity of the saturated hydrocarbon group is prevented from interfering with the movement of each unit structure.

[0086] The linking group represented by formula (2-5) is a linking group in which b in formula (2) is 0. In the linking group represented by formula (2-5), the two alkylene groups in the linking structure arranged between the two unit structures are bonded only via an ether oxygen atom that imparts flexibility, allowing the hydroxyl groups in the two unit structures to move freely. Furthermore, the linking group represented by formula (2-5) can suppress the bulkiness caused by Y in formula (2) compared to the linking group in formula (2) where b is 1. Therefore, a lubricating layer containing a fluorine-containing ether compound having a linking group represented by formula (2-5) can maintain good corrosion resistance and spin-off resistance even when made even thinner, which is preferable.

[0087] In the linking group represented by formula (2-5), a51 and a52 represent integers of 0 to 5, and each is preferably an integer of 0 to 3. a51 and a52 may be the same or different. When one of a51 and a52 is 0, the fluorinated ether compound represented by formula (1) is easily produced, which is preferable. The total value of a51 and a52 is 1 to 6, and at least one of a51 and a52 is 1 or more, similar to a1 and a2 in formula (2).

[0088] In the linking group represented by formula (2-5), the sum of a51 and a52 is 1 or more, so the hydrophobicity of the fluorine-containing ether compound is good, and a lubricating layer containing the same is less likely to absorb water, which causes corrosion, and has good corrosion resistance. Furthermore, the sum of a51 and a52 is 6 or less, so the linking group represented by formula (2-5) has appropriate flexibility, and a lubricating layer containing the same is denser and has good spin-off resistance. The sum of a51 and a52 is preferably 3 or less, so that the flexibility of the fluorine-containing ether compound is further improved and a lubricating layer with better spin-off resistance can be formed.

[0089] In the linking group represented by formula (2-5), there are at least six atoms between the hydroxyl groups contained in each of the two unit structures. Therefore, the distance between the two hydroxyl groups contained in the linking group represented by formula (2-5) is appropriate, and the two hydroxyl groups contained in the linking group represented by formula (2-5) can be prevented from aggregating within the molecule.

[0090] In formula (1), when x is 2, two R 3 may be the same or different. 3 When the two R's are the same, the fluorine-containing ether compound is more uniformly coated on the protective layer, and a lubricating layer with better adhesion can be formed. 3 "The two R 3 The atoms contained in are R located in the center of the chain structure of the molecule. 2 This means that the elements are arranged symmetrically with respect to each other.

[0091] (R 1 and R 4 (end group indicated by In the fluorine-containing ether compound represented by formula (1), R 1 and R 4 are terminal groups having 1 to 4 polar groups and having 1 to 50 carbon atoms. In this embodiment, R 1 and R 4 Since each of R is the above-mentioned terminal group, a lubricating layer containing a fluorine-containing ether compound represented by formula (1) has good corrosion resistance and a high spin-off suppressing effect. 1 and R 4 R can be appropriately selected depending on the performance required of the lubricant containing the fluorine-containing ether compound. 1 and R 4 may be the same or may be different from each other.

[0092] R 1 and R 4 Since the number of polar groups contained in each of R is one or more, when a lubricating layer is formed on a protective layer using a lubricant containing a fluorine-containing ether compound, a favorable interaction occurs between the lubricating layer and the protective layer. As a result, the lubricating layer has excellent adhesion to the protective layer and a high spin-off suppression effect. In addition, R 1 and R 4 The number of polar groups contained in each is four or less, so R 1 and R 4 The polar groups contained in R are unlikely to be uninvolved in interactions with the active sites on the protective layer or with polar groups contained in other fluorine-containing ether compounds present in the lubricating layer, and a lubricating layer with high corrosion resistance and spin-off suppression effects can be obtained. 1 and R 4 Since the number of polar groups contained in each of R is 4 or less, it is possible to prevent the polarity of the fluorine-containing ether compound in the lubricating layer containing the fluorine-containing ether compound from being too high, causing the fluorine-containing ether compound to aggregate and form clumps, which would result in the loss of smoothness of the lubricating layer. 1 and R 4The number of polar groups contained in each of R is preferably 3 or less, and most preferably 2, so that the resulting fluorine-containing ether compound can provide a lubricating layer with higher corrosion resistance and spin-off suppression effects. 1 and R 4 When the number of polar groups contained in each of R 1 and R 4 This effectively prevents the aggregation of polar groups in the terminal groups represented by R 1 and R 4 The polar groups contained in the fluorine-containing ether compound are less likely to be uninvolved in the interaction with the active sites on the protective layer or with the polar groups contained in other fluorine-containing ether compounds present in the lubricating layer. As a result, the presence of polar groups that are uninvolved in the interaction can prevent water, which causes corrosion, from being absorbed into the magnetic recording medium, resulting in a fluorine-containing ether compound that can form a lubricating layer with higher corrosion resistance and spin-off suppression effects.

[0093] R in Equation (1) 1 The polar groups contained in R 4 The total number of polar groups contained in R is preferably 2 to 6, more preferably 3 to 6, and most preferably 4 to 6. When the total number of polar groups is 2 or more, R 1 and R 4 The interaction between the polar groups and the protective layer is effectively achieved. As a result, the fluorine-containing ether compound can form a lubricating layer that has high adhesion to the protective layer. Therefore, a lubricating layer with better spin-off resistance can be obtained. Furthermore, if the total number of polar groups is 6 or less, the fluorine-containing ether compound's polarity is too high, which can prevent it from taking in water, which causes corrosion. Therefore, a lubricating layer with better corrosion resistance can be formed.

[0094] R 1 and R 4The polar groups contained in are hydroxyl group (-OH), amino group (-NH2), carboxyl group (-COOH), formyl group (-(C=O)H), carbonyl group (-CO-), sulfo group (-SO3H), cyano group (-CN), and group with an amide bond (-NR 7 COR 8 or -CONR 9 R 10 ;R 7 , R 8 , R 9 and R 10 are each independently a hydrogen atom or an organic group.) The group having an amide bond includes, as shown in the above formula, both a group bonded at a carbon atom constituting the amide bond (for example, a carboxamide group (-C(=O)NH2)) and a group bonded at a nitrogen atom constituting the amide bond (for example, an acetamide group (-NHC(=O)CH3)). In the group having an amide bond, the R 7 and R 8 may be bonded to each other to form a ring, and the R 9 and R 10 may be bonded to each other to form a ring. 7 , R 8 , R 9 and R 10 are preferably each independently selected from the group consisting of a hydrogen atom, a methyl group, an ethyl group, a propyl group, and a butyl group.

[0095] R 1 and R 4 Preferably, each independently contains at least one polar group selected from the group consisting of a hydroxyl group, a cyano group, and a group having an amide bond. This is because the hydroxyl group, the cyano group, and the group having an amide bond are chemically stable, and the lubricating layer containing the fluorine-containing ether compound having these polar groups will not deteriorate over the long term. In addition, the hydroxyl group, the cyano group, and the group having an amide bond are not too acidic, and therefore will not corrode the substrate.

[0096] R in Equation (1) 1 and R4 each preferably contains at least one hydroxyl group, and R 1 and the polar group R 4 It is more preferable that all of the polar groups of R are hydroxyl groups. In addition, since the state of coating of the fluorine-containing ether compound with the protective layer becomes more uniform, 1 and the polar group R 3 and the polar group R 4 It is more preferable that all of the polar groups contained in the compound are hydroxyl groups.

[0097] R 1 and R 4 The 1 to 4 polar groups each have may be the same in part or all, or may be different from each other. Also, R 1 The number of polar groups in R 4 The number of polar groups in R may be the same or different. 1 The number of polar groups in R 4 and the number of polar groups therein are preferably the same, since this results in a more uniform coating state of the fluorine-containing ether compound on the protective layer and allows the formation of a lubricating layer with better adhesion.

[0098] R 1 and R 4 The number of carbon atoms in the terminal group represented by R is 1 to 50, preferably 3 to 20, and more preferably 4 to 15. 1 and R 4 When the number of carbon atoms in the terminal group represented by R is 1 or more, the hydrophobicity of the terminal group can be ensured, so that the lubricating layer can be prevented from attracting water, which causes corrosion, and the lubricating layer has good corrosion resistance. 1 and R 4 When the number of carbon atoms in the terminal group represented by the formula (I) is 50 or less, the terminal group has a flexible structure, and the adhesion between the lubricating layer containing the fluorine-containing ether compound and the protective layer is good. As a result, a lubricating layer that can suppress spin-off can be obtained.

[0099] In the fluorine-containing ether compound represented by formula (1), R1 and R 4 are preferably each independently a terminal group represented by the following formula (3):

[0100] [ka] (In formula (3), l represents an integer of 1 to 3. l m's each independently represent an integer of 1 to 6. l n's each independently represent an integer of 1 to 6. In one repeating unit, at least one of m and n is 1. A represents an alkyl group which may have a polar group, an organic group containing a carbon-carbon unsaturated bond which may have a polar group, or a hydrogen atom.)

[0101] R 1 and R 4 is a terminal group represented by formula (3), R 1 and R 4 is R 2 It has an oxygen atom bonded to a methylene group (-CH2-) that is bonded to R 1 and R 4 is R 1 and R 4 Each of these has an oxygen atom at the end that bonds to the adjacent CH2. 1 and R 4 The oxygen atom located at the end of R forms an ether bond (-O-) with the atoms bonded on both sides of it. This ether bond provides the fluorine-containing ether compound represented by formula (1) with appropriate flexibility, and 1 and R 4 This increases the affinity between the polar group in the terminal group represented by formula (1) and the protective layer. As a result, the fluorine-containing ether compound represented by formula (1) can form a lubricating layer that has excellent adhesion to the protective layer.

[0102] In formula (3), l is an integer of 1 to 3, preferably an integer of 1 to 2, and most preferably 1. When l in formula (3) is 3 or less, the number of hydroxyl groups in the terminal groups represented by formula (3) is too large, which prevents water, which causes corrosion, from being attracted to the lubricating layer, and a lubricating layer with good corrosion resistance is obtained. When l in formula (3) is 2 or 3, 2 or 3 repeating units (-(CH2) m -CH(OH)-(CH2) n The combinations of m and n in —O—) may be different from one another, or some or all of them may be the same.

[0103] In formula (3), l m's each independently represent an integer of 1 to 6, and l n's each independently represent an integer of 1 to 6. One repeating unit (-(CH2) m -CH(OH)-(CH2) n In the formula (II), at least one of m and n is 1. This is because the mobility of the hydroxyl group in the repeating unit is not reduced by the 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.

[0104] In formula (3), A represents an alkyl group which may have a polar group, an organic group containing a carbon-carbon unsaturated bond which may have a polar group, or a hydrogen atom. When A in formula (3) is an alkyl group having no polar group, specific examples of A include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, and a hexyl group.

[0105] When A in formula (3) is an alkyl group having a polar group, the polar group is R 1 and R 4 The polar groups contained in the above-mentioned formula (1) are preferably those listed as preferred examples. Among the above-mentioned polar groups, polar groups selected from the group consisting of hydroxyl groups, cyano groups, and groups having an amide bond are more preferred. This is because hydroxyl groups, cyano groups, and groups having an amide bond are chemically stable, and the lubricating layer containing a fluorine-containing ether compound having these polar groups will not deteriorate over the long term. In addition, the acidity of hydroxyl groups, cyano groups, and groups having an amide bond is not too high, and they are less likely to corrode the substrate.

[0106] When A in formula (3) is an alkyl group having a polar group, examples of A include a 2-hydroxyethyl group, a 3-hydroxypropyl group, a 4-hydroxybutyl group, a 5-hydroxypentyl group, a 6-hydroxyhexyl group, a 2-aminoethyl group, a 3-aminopropyl group, a 2-carboxyethyl group, a 3-carboxypropyl group, a 2-carbonylethyl group, a 3-carbonylpropyl group, a 2-acetylethyl group, a 3-acetylpropyl group, a 2-sulfoethyl group, a 3-sulfopropyl group, a 2-cyanoethyl group, a 3-cyanopropyl group, a 4-cyanobutyl group, a 2-acetamidoethyl group, a 3-acetamidopropyl group, a 4-acetamidobutyl group, a 2-carboxamidoethyl group, a 3-carboxamidopropyl group, and a 4-carboxamidobutyl group.

[0107] Among the above alkyl groups having a polar group, any one of a 2-hydroxyethyl group, a 3-hydroxypropyl group, a 4-hydroxybutyl group, a 5-hydroxypentyl group, a 6-hydroxyhexyl group, a 2-cyanoethyl group, a 3-cyanopropyl group, a 2-acetamidoethyl group, a 2-carboxamidoethyl group, and a 3-carboxamidopropyl group is preferred, and any one of a 2-hydroxyethyl group, a 3-hydroxypropyl group, a 2-cyanoethyl group, a 3-cyanopropyl group, and a 2-acetamidoethyl group is more preferred.

[0108] When A in formula (3) is an organic group containing a carbon-carbon unsaturated bond, examples of A include an organic group containing at least one selected from an aromatic hydrocarbon, an unsaturated heterocycle, an alkenyl group, and an alkynyl group.

[0109] When A in formula (3) is an organic group containing a carbon-carbon unsaturated bond and having no polar group, A is preferably a phenyl group, a methoxyphenyl group, a fluorinated phenyl group, a naphthyl group, a phenethyl group, a methoxyphenethyl group, a fluorinated phenethyl group, a benzyl group, a methoxybenzyl group, a naphthylmethyl group, a methoxynaphthyl group, a pyrrolyl group, a pyrazolyl group, a methylpyrazolylmethyl group, an imidazolyl group, a furyl group, a furfuryl group, an oxazolyl group, an isoxazolyl group, a thienyl group, a thienylethyl group, a thiazolyl group, a methylthiazolylethyl group, an isothiazolyl group, Examples thereof include a pyridyl group, a pyrimidinyl group, a pyridazinyl group, a pyrazinyl group, an indolinyl group, a benzofuranyl group, a benzothienyl group, a benzimidazolyl group, a benzoxazolyl group, a benzothiazolyl group, a benzopyrazolyl group, a benzisoxazolyl group, a benzisothiazolyl group, a quinolyl group, an isoquinolyl group, a quinazolinyl group, a quinoxalinyl group, a phthalazinyl group, a cinnolinyl group, a vinyl group, an allyl group, a butenyl group, a propynyl group, a propargyl group, a butynyl group, a methylbutynyl group, a pentynyl group, a methylpentynyl group, and a hexynyl group.

[0110] Among the above organic groups containing a carbon-carbon unsaturated bond, any one of a phenyl group, a methoxyphenyl group, a naphthyl group, a phenethyl group, a methoxyphenethyl group, a fluorinated phenethyl group, a thienylethyl group, an allyl group, a butenyl group, and a propargyl group is preferred, and in particular, any one of a phenyl group, a methoxyphenyl group, an allyl group, and a butenyl group is more preferred.

[0111] When A in formula (3) is an organic group containing a carbon-carbon unsaturated bond having a polar group, the polar group can be R 1 and R 4The polar groups listed as preferred examples of the polar group contained in can be used. Among these polar groups, at least one selected from the group consisting of a cyano group and a group having an amide bond is more preferred. A cyano group and a group having an amide bond are preferred because they are chemically stable and do not deteriorate over the long term when the lubricating layer contains a fluorine-containing ether compound having these polar groups. In addition, a cyano group and a group having an amide bond are not too acidic and have almost no corrosive effect on the substrate.

[0112] When A in formula (3) is an organic group containing a carbon-carbon unsaturated bond having a polar group, examples of A include a cyanophenyl group, a carboxamidophenyl group, an acetamidophenyl group, a cyanonaphthyl group, a carboxamido naphthyl group, an acetamido naphthyl group, a cyanophenethyl group, a carboxamidophenethyl group, an acetamidophenethyl group, a cyanobenzyl group, a carboxamidobenzyl group, and an acetamidobenzyl group.

[0113] Among the above, any one of a cyanophenyl group, a carboxamidophenyl group, an acetamidophenyl group, a cyanobenzyl group, a carboxamidobenzyl group, and an acetamidobenzyl group is preferable, and any one of a cyanophenyl group, a carboxamidophenyl group, and an acetamidophenyl group is more preferable.

[0114] When A in formula (3) is a hydrogen atom, A forms a hydroxyl group together with the oxygen atom in formula (3). When A is a hydrogen atom, A in formula (3) binds to the repeating unit (-(CH2) m -CH(OH)-(CH2) n In —O—), n is preferably 2 or more, because this makes the distance between the terminal hydroxyl group formed by the oxygen atom and the hydrogen atom A in formula (3) and the hydroxyl group adjacent to the terminal hydroxyl group more appropriate.

[0115] Here, we will explain the bond between the terminal group represented by formula (3) and the active site on the protective layer. The functional groups (active sites) present in large numbers on the protective layer include locally charged sites and sites with widely distributed charges. The hydroxyl group contained in formula (3) and the R represented by formula (2) 3 The hydroxyl groups contained therein exhibit adsorption ability by interacting with locally charged sites on the protective layer via hydrogen bonds. On the other hand, aromatic hydrocarbons, unsaturated heterocycles, alkenyl groups, and alkynyl groups have delocalized charges. Therefore, when the terminal group A represented by formula (3) contains at least one selected from aromatic hydrocarbons, unsaturated heterocycles, alkenyl groups, and alkynyl groups, A exhibits adsorption ability by interacting with sites on the protective layer where the charge distribution is widespread.

[0116] Therefore, the hydroxyl group contained in formula (3) and the R 3 The hydroxyl group contained in the terminal group A of formula (3) and the organic group containing a carbon-carbon unsaturated bond when A is an organic group containing a carbon-carbon unsaturated bond can be adsorbed to different sites on the protective layer. 3 The hydroxyl group contained in the terminal group A of formula (3) and the organic group containing a carbon-carbon unsaturated bond when A is an organic group containing a carbon-carbon unsaturated bond can independently interact with the functional group (active site) on the protective layer. 1 and R 4 When at least one of the groups is a terminal group represented by formula (3), and A in formula (3) is an organic group containing a carbon-carbon unsaturated bond, the lubricating layer containing the fluorine-containing ether compound has excellent adhesion to the protective layer, can prevent water penetration, and has a high corrosion-inhibiting effect on the magnetic recording medium.

[0117] R 1 and R 4 are each independently a terminal group represented by formula (3-1) or (3-2).

[0118] [ka] (In formula (3-1), p represents an integer of 0 to 3, q ​​represents an integer of 0 to 2, and r represents an integer of 1 to 5. The total value of p and r is 1 to 5. B represents a polar group.) (In formula (3-2), s represents an integer of 0 to 2, and t represents an integer of 1 to 5.)

[0119] Each polar group contained in the terminal group represented by formula (3-1) and (3-2) is bonded to a different carbon atom. In formula (3-1) and (3-2), the carbon atoms bonded to the polar groups are bonded to each other via a linking group containing a carbon atom not bonded to a polar group. Therefore, R 1 and / or R 4 When is a terminal group represented by formula (3-1) or (3-2), in the fluorine-containing ether compound represented by formula (1), the polar group in formula (3-1) or (3-2) has a linking group containing a carbon atom to which the polar group is not bonded, so that both the terminal polar group and the hydroxyl group adjacent to the terminal polar group can be oriented so as to adhere to the protective layer. Therefore, it is presumed that a strong interaction with the protective layer can be obtained, and a lubricating layer that can suppress spin-off can be formed.

[0120] R 1 and / or R 4 is formula (3-1) or formula (3-2), for example, R 1 and / or R 4 Compared to the case where terminal groups are arranged in which the carbon atoms to which polar groups are bonded are directly bonded, the polar groups in the terminal groups are less likely to aggregate and more likely to interact with the protective layer. 1 and / or R 4 is formula (3-1) or formula (3-2), the terminal portions in the fluorinated ether compound are less likely to lift up and the adhesion to the protective layer is less likely to decrease, compared with the case where terminal groups are arranged in which the carbon atoms to which polar groups are bonded are directly bonded to each other.

[0121] In the terminal group represented by formula (3-1), the linking group between the carbon atom to which the terminal polar group B is bonded and the carbon atom to which the hydroxyl group adjacent to the terminal polar group B is bonded contains an oxygen atom forming an ether bond. In formula (3-1), p represents an integer of 0 to 3, q ​​represents an integer of 0 to 2, and r represents an integer of 1 to 5, with the sum of p and r being 1 to 5. Therefore, the linking group has a linear structure consisting of 3 to 7 atoms, including carbon atoms to which the polar group B and the hydroxyl group are not bonded.

[0122] In the terminal group represented by formula (3-1), the linking group contains an oxygen atom forming an ether bond and has a linear structure consisting of three or more atoms, including polar group B and a carbon atom not bonded to a hydroxyl group, so the distance between polar group B and the hydroxyl group adjacent to polar group B is appropriate. This prevents intramolecular interaction between polar group B and the hydroxyl group adjacent to polar group B, allowing both polar group B and the hydroxyl group adjacent to polar group B to adhere to the protective layer. Furthermore, because the linking group has a linear structure consisting of three or more atoms, even if the compound contains an oxygen atom forming an ether bond, it becomes a fluorine-containing ether compound with good hydrophobicity. Furthermore, because the linking group has a linear structure consisting of three or more atoms, even if the compound contains an oxygen atom forming an ether bond, molecular mobility is appropriate, intramolecular aggregation is unlikely to occur, and excellent adhesion to the protective layer is achieved.

[0123] In the terminal group represented by formula (3-1), the linking group contains an oxygen atom that forms an ether bond, and has a linear structure consisting of 7 or less atoms, including a polar group B and a carbon atom that is not bonded to a hydroxyl group. Therefore, the hydrophobicity of the linking group is not too high, which does not impair the adhesion between the lubricating layer containing the fluorine-containing ether compound and the protective layer. For these reasons, a fluorine-containing ether compound having a terminal group represented by formula (3-1), in which the linking group is a linear structure consisting of 3 to 7 atoms including a polar group B and a carbon atom that is not bonded to a hydroxyl group, has excellent adhesion to a protective layer, exhibits high corrosion resistance, and can form a lubricating layer that has a high spin-off suppression effect.

[0124] In formula (3-1), the sum of p and r is 1 to 5, preferably 1 to 3. In formula (3-1), the carbon atom contained in the linking group disposed between the carbon atoms bonded to the polar groups prevents the intramolecular interaction between adjacent polar groups from occurring in preference to the interaction between the polar groups and the protective layer, thereby improving the adhesion between the polar groups in formula (3-1) and the protective layer. On the other hand, if the number of carbon atoms contained in the linking group is too large, the flexibility of the terminal group represented by formula (3-1) decreases, making it difficult to uniformly coat the protective layer. In the terminal group represented by formula (3-1), the sum of p and r is 5 or less, so the alkylene chain in the main chain portion of formula (3-1) is not too long. Therefore, the long rigid alkylene chain reduces the flexibility of the terminal portion, weakening the interaction with the protective layer and preventing the terminal portion from lifting up. p is preferably 0 or 1, more preferably 0. r is preferably 1 or 2, more preferably 1.

[0125] In formula (3-1), B represents a polar group. 1 and R 4 The polar groups contained in the above-mentioned formula (1) are preferably those listed as preferred examples. Among the above-mentioned polar groups, polar groups selected from the group consisting of hydroxyl groups, cyano groups, and groups having an amide bond are more preferred. This is because hydroxyl groups, cyano groups, and groups having an amide bond are chemically stable, and the lubricating layer containing a fluorine-containing ether compound having these polar groups will not deteriorate over the long term. In addition, the acidity of hydroxyl groups, cyano groups, and groups having an amide bond is not too high, and they are less likely to corrode the substrate.

[0126] In formula (3-1), q represents an integer of 0 to 2. The number of polar groups in formula (3-1) is q+2. 1 and R 4 The number of polar groups contained in each of the formulas is preferably 3 or less, and most preferably 2. Therefore, q in formula (3-1) is preferably 0 or 1, and more preferably 0.

[0127] In the terminal group represented by formula (3-2), the linking group between the carbon atom to which the terminal hydroxyl group is bonded and the carbon atom to which the hydroxyl group adjacent to the terminal hydroxyl group is bonded does not contain an oxygen atom. This results in small intramolecular interactions, making intramolecular aggregation unlikely, resulting in excellent adhesion to the protective layer. In formula (3-2), t represents an integer of 1 to 5. Therefore, the linking group has a linear structure consisting of 1 to 5 atoms, including a carbon atom to which no hydroxyl group is bonded. Because the linking group contained in formula (3-2) has a linear structure consisting of one or more atoms, including a carbon atom to which no hydroxyl group is bonded, the distance between the terminal hydroxyl group and the hydroxyl group adjacent to the terminal hydroxyl group is appropriate, making intramolecular aggregation unlikely, and providing good hydrophobicity.

[0128] Furthermore, the linking group contained in formula (3-2) does not contain an oxygen atom forming an ether bond and has a linear structure consisting of five or fewer atoms including a carbon atom not bonded to a hydroxyl group. Therefore, the linking group is not so hydrophobic as to impair adhesion to the protective layer, and the linking group is not so bulky as to interfere with the movement of the hydroxyl group. Similarly to formula (3-1), if the linking group between the carbon atoms bonded to the polar groups in formula (3-2) contains too many carbon atoms, the flexibility of the terminal group represented by formula (3-2) decreases, making it difficult to uniformly coat the entire surface of the protective layer. In the terminal group represented by formula (3-2), t is 5 or less, so the alkylene chain in the main chain of formula (3-2) is not too long. Therefore, the long, rigid alkylene chain reduces the flexibility of the terminal portion, preventing a decrease in the interaction between the terminal hydroxyl group and the protective layer.

[0129] For these reasons, a lubricating layer containing a fluorine-containing ether compound in which the linking group has a linear structure consisting of 1 to 5 atoms including a carbon atom not bonded to a hydroxyl group and does not contain an oxygen atom forming an ether bond, has excellent adhesion to the protective layer, high corrosion resistance, and a high spin-off suppression effect. t is preferably 1 or 2, and more preferably 1.

[0130] In formula (3-2), s represents an integer of 0 to 2. The number of polar groups in formula (3-2) is s+2. 1 and R 4 The number of polar groups contained in each of the formulas is preferably 3 or less, and most preferably 2. Therefore, s in formula (3-2) is preferably 0 or 1, and more preferably 0.

[0131] When x in formula (1) is 2, the fluorine-containing ether compound contains R 3 There are two R 3 Each of these has two or three hydroxyl groups, so when x is 2, the ratio of R to the total number of polar groups in the fluorine-containing ether compound is 1 and R 4 The ratio of polar groups in the protective layer is reduced. Since the number of active sites in the protective layer is limited, R 1 and R 4 When the proportion of polar groups in the 1 and R 4 The interaction between the protective layer and the surface of the substrate is weakened. In the terminal groups represented by formulas (3-1) and (3-2), the carbon atoms bonded to the polar groups are bonded to each other via a linking group containing a carbon atom not bonded to a polar group, and therefore have a relatively strong interaction with the protective layer. For this reason, particularly when x in formula (1) is 2, R 1 and R 4 are preferably each independently a terminal group represented by formula (3-1) or (3-2).

[0132] (R 2 (PFPE chain shown as In the fluorine-containing ether compound represented by formula (1), R 2 is a perfluoropolyether chain. 2 When a lubricating layer is formed by applying a lubricant containing the fluorine-containing ether compound of this embodiment onto a protective layer, the PFPE chain represented by R not only covers the surface of the protective layer but also imparts lubricity to the lubricating layer, thereby reducing the frictional force between the magnetic head and the protective layer.2 The PFPE chain represented by the formula (I) is appropriately selected depending on the performance required of the lubricant containing the fluorine-containing ether compound.

[0133] (x+1) R 2 The (x+1) R may be partially or entirely the same, or may be different from each other. 2 It is preferable that all of the (x+1) R are the same. This is because the coating state of the fluorine-containing ether compound on the protective layer becomes more uniform, resulting in a lubricating layer with better adhesion. 2 Two or more of the R 2 are the same, (x+1) R 2 Among them, R 2 It means that two or more of the same R are included. 2 The term also includes those having the same repeating unit structure but different average degrees of polymerization.

[0134] R 2 Examples of the PFPE chain represented by the formula (1) include those made of a polymer or copolymer of perfluoroalkylene oxide. Examples of perfluoroalkylene oxide include perfluoromethylene oxide, perfluoroethylene oxide, perfluoro-n-propylene oxide, perfluoroisopropylene oxide, and perfluorobutylene oxide.

[0135] (x+1) R in Equation (1) 2 are each preferably independently a PFPE chain represented by the following formula (4) derived from a polymer or copolymer of perfluoroalkylene oxide. -(CF2) w1 -O-(CF2O) w2 -(CF2CF2O) w3 -(CF2CF2CF2O) w4 -(CF2CF2CF2CF2O) w5 -(CF2) w6 - (4) (In formula (4), w2, w3, w4, and w5 represent average degrees of polymerization and each independently represent 0 to 20. However, w2, w3, w4, and w5 cannot all be 0 at the same time. w1 and w6 represent average values ​​representing the number of CF2 and each independently represent 1 to 3. There are no particular restrictions on the arrangement order of the repeating units (CF2O), (CF2CF2O), (CF2CF2CF2O), and (CF2CF2CF2CF2O) in formula (4).)

[0136] In formula (4), w2, w3, w4, and w5 represent average degrees of polymerization, each independently representing 0 to 20, preferably 0 to 15, and more preferably 0 to 10. In formula (4), w1 and w6 are average values ​​indicating the number of CF2, and each independently represents 1 to 3. w1 and w6 are determined depending on the structure of the repeating unit arranged at the end of the chain structure in the PFPE chain represented by formula (4), etc. In formula (4), (CF2O), (CF2CF2O), (CF2CF2CF2O), and (CF2CF2CF2CF2O) are repeating units. There are no particular limitations on the arrangement order of the repeating units in formula (4). There are also no particular limitations on the number of types of repeating units in formula (4).

[0137] (x+1) R in Equation (1) 2 are preferably each independently any one selected from the PFPE chains represented by the following formulas (4-1) to (4-4). (x+1) R 2 are each one selected from the PFPE chains represented by formulas (4-1) to (4-4), a fluorine-containing ether compound can be obtained that provides a lubricating layer with good lubricity. 2When each of the R is any one selected from the PFPE chains represented by formulas (4-1) to (4-4), the ratio of the number of oxygen atoms (the number of ether bonds (-O-)) to the number of carbon atoms in the PFPE chain is appropriate. Therefore, the fluorine-containing ether compound has an appropriate hardness. Therefore, the fluorine-containing ether compound applied to the protective layer is less likely to aggregate on the protective layer, and a thinner lubricating layer can be formed with a sufficient coverage. In addition, (x+1) R 2 However, a lubricating layer containing a fluorine-containing ether compound that is any one selected from the PFPE chains represented by formulas (4-1) to (4-4) is more dense and can further suppress spin-off, which is preferable.

[0138] -CF2-(OCF2CF2) h -(OCF2) i -OCF2- (4-1) (In formula (4-1), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20.) -CF2CF2-(OCF2CF2CF2) j -OCF2CF2- (4-2) (In formula (4-2), j represents the average degree of polymerization and represents 1 to 15.) -CF2CF2CF2-(OCF2CF2CF2CF2) k -OCF2CF2CF2- (4-3) (In formula (4-3), k represents the average degree of polymerization and represents 1 to 10.) -(CF2) w7 -O-(CF2CF2CF2O) w8 -(CF2CF2O) w9 -(CF2) w10 - (4-4) (In formula (4-4), w8 and w9 represent the average degree of polymerization, each independently representing 1 to 20. w7 and w10 are average values ​​representing the number of CF2, each independently representing 1 to 2.)

[0139] In formula (4-1), the arrangement order of the repeating units (OCF2CF2) and (OCF2) is not particularly limited. In formula (4-1), the number h of (OCF2CF2) and the number i of (OCF2) may be the same or different. The PFPE chain represented by formula (4-1) may be a polymer of (OCF2CF2). In addition, the PFPE chain represented by formula (4-1) may be any of a random copolymer, a block copolymer, and an alternating copolymer composed of (OCF2CF2) and (OCF2).

[0140] In formulas (4-1) to (4-3), h, which indicates the average degree of polymerization, is 1 to 20, i, which is 0 to 20, j, which is 1 to 15, and k, which is 1 to 10, and therefore the fluorine-containing ether compound provides a lubricating layer with good lubricity. Furthermore, in formulas (4-1) to (4-3), h and i, which indicate the average degree of polymerization, are 20 or less, j is 15 or less, and k is 10 or less, and therefore the viscosity of the fluorine-containing ether compound does not become too high, and lubricants containing the fluorine-containing ether compound are easily applied, which is preferable. h, i, j, and k, which indicate the average degree of polymerization, are preferably 1 to 10, more preferably 1.5 to 8, and even more preferably 2 to 7, and therefore the fluorine-containing ether compound easily wets and spreads on the protective layer, and a lubricating layer with a uniform thickness is easily obtained.

[0141] In formula (4-4), the arrangement order of the repeating units (CFCFCFO) and (CFCFO) is not particularly limited. In formula (4-4), the number w8 of (CFCFCFO) and the number w9 of (CFCFO), which indicate the average degree of polymerization, may be the same or different. Formula (4-4) may include any of a random copolymer, a block copolymer, and an alternating copolymer composed of the monomer units (CFCFCFO) and (CFCFO).

[0142] In formula (4-4), 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 (4-4), w7 and w10 are average values ​​indicating the number of CF2, and each independently represents 1 to 2. w7 and w10 are determined depending on the structure of the repeating unit located at the end of the chain structure in the PFPE chain represented by formula (4-4), etc.

[0143] In the fluorine-containing ether compound represented by formula (1), when x is 1, two R 2 is the same, and R 1 and R 4 This is because the resulting fluorine-containing ether compound can be produced easily and efficiently. In the fluorine-containing ether compound represented by formula (1), when x is 2, two R 3 is the same, and R 1 Side R 2 and R 4 Side R 2 is the same, and R 1 and R 4 This is because the resulting fluorine-containing ether compound can be produced easily and efficiently.

[0144] Specifically, the fluorine-containing ether compound represented by formula (1) is preferably any one of the compounds represented by the following formulae (AA) to (AT), (BA) to (BR), (CA) to (CJ), (DA) to (DG), and (EA) to (EC). When the compound represented by formula (1) is any of the compounds represented by the following formulae (AA) to (AT), (BA) to (BR), (CA) to (CJ), (DA) to (DG), and (EA) to (EC), the raw materials are easily available, and even if the thickness is thin, a lubricating layer can be formed that has even better corrosion resistance and a high spin-off suppression effect.

[0145] In the compounds represented by the following formulae (AA) to (AT), (BA) to (BR), (CA) to (CJ), (DA) to (DG), and (EA) to (EC), Rf1, Rf2, and Rf3, which represent PFPE chains, respectively have the following structures. That is, in the compounds represented by the following formulae (AA) to (AT), (BC) to (BR), (CA) to (CJ), (DB) to (DG), and (EA) to (EC), Rf1 is a PFPE chain represented by the above formula (4-1). In the compounds represented by the following formulae (BA) and (DA), Rf2 is a PFPE chain represented by the above formula (4-2). In the compound represented by the following formula (BB), Rf3 is a PFPE chain represented by the above formula (4-3). In addition, h and i in Rf1, j in Rf2, and k in Rf3, which represent the PFPE chain in formulas (AA) to (AT), (BA) to (BR), (CA) to (CJ), (DA) to (DG), and (EA) to (EC), are values ​​that indicate the average degree of polymerization, and therefore are not necessarily integers.

[0146] [ka]

[0147] In the compounds represented by the following formulas (AA) to (AT), x in formula (1) is 1. 3 is a linking group represented by any one of the above formulas (2-1) to (2-5). 1 and R 4 is the terminal group represented by the above formula (3-1). 2 is the PFPE chain represented by the above formula (4-1).

[0148] In the compounds represented by the following formulas (BA) and (BB), x in formula (1) is 1. 3 is the linking group represented by the above formula (2-1). 1 and R 4 is the terminal group represented by the above formula (3-1). Formula (BA) is R 2 is the above formula (4-2), and formula (BB) is R 2 is the PFPE chain represented by the above formula (4-3).

[0149] In the compounds represented by the following formulas (BC) to (BR), x in formula (1) is 1. 3 is a linking group represented by the above formula (2-1). Formulas (BC), (BE), (BF), (BH) to (BJ), (BL), (BQ), and (BR) are R 1 and R 4 is the above formula (3-1). Formulas (BD), (BG), and (BK) are R 1 and R 4 is the above formula (3-2). Formulas (BM) to (BP) are R 1 and R 4 is a terminal group represented by formula (3) that does not fall under the above formulas (3-1) and (3-2). The compounds represented by formulas (BC) to (BR) are 2 is the PFPE chain represented by the above formula (4-1).

[0150] In the compounds represented by the following formulas (CA) to (CJ), x in formula (1) is 2. 3 is a linking group represented by any one of the above formulas (2-1) to (2-5). 1 and R 4 is the terminal group represented by the above formula (3-1). 2 is the PFPE chain represented by the above formula (4-1).

[0151] In the compound represented by the following formula (DA), x in formula (1) is 2. 3 is the linking group represented by the above formula (2-1). 1 and R 4 is the terminal group represented by the above formula (3-1). 2 is the PFPE chain represented by the above formula (4-2). In the compounds represented by the following formulas (DB) to (DG), x in formula (1) is 2. 3 is a linking group represented by the above formula (2-1). Formulas (DB), (DD) to (DF) are R 1 and R 4 is the above formula (3-1). Formula (DC) is R 1 and R 4 is the above formula (3-2). Formula (DG) is R 1 and R4 is a terminal group represented by formula (3) that does not fall under the above formulas (3-1) and (3-2). The compounds represented by formulas (DB) to (DG) are 2 is the PFPE chain represented by the above formula (4-1).

[0152] In the compound represented by the following formula (EA), x in formula (1) is 1. 3 is a linking group represented by the above formula (2-5). 1 and R 4 is the terminal group represented by the above formula (3-1). 2 is the PFPE chain represented by the above formula (4-1). In the compound represented by the following formula (EB), x in formula (1) is 1. 3 is a linking group represented by the above formula (2-5). 1 and R 4 is a terminal group represented by formula (3) that does not fall under the above formulas (3-1) and (3-2). 2 is the PFPE chain represented by the above formula (4-1). In the compound represented by the following formula (EC), x in formula (1) is 1. 3 is a linking group represented by the above formula (2-4). 1 and R 4 is a terminal group represented by formula (3) that does not fall under the above formulas (3-1) and (3-2). 2 is the PFPE chain represented by the above formula (4-1).

[0153] [ka] (In the two Rf1s in formula (AA), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20. The average degrees of polymerization in the two Rf1s may be the same or different.) (In the two Rf1s in formula (AB), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20. The average degrees of polymerization in the two Rf1s may be the same or different.) (In the two Rf1s in formula (AC), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20. The average degrees of polymerization in the two Rf1s may be the same or different.) (In the two Rf1s in formula (AD), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20. The average degrees of polymerization in the two Rf1s may be the same or different.)

[0154] [ka] (In the two Rf1s in formula (AE), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20. The average degrees of polymerization in the two Rf1s may be the same or different.) (In the two Rf1s in formula (AF), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20. The average degrees of polymerization in the two Rf1s may be the same or different.) (In the two Rf1s in formula (AG), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20. The average degrees of polymerization in the two Rf1s may be the same or different.) (In the two Rf1s in formula (AH), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20. The average degrees of polymerization in the two Rf1s may be the same or different.)

[0155] [ka] (In the two Rf1s in formula (AI), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20. The average degrees of polymerization in the two Rf1s may be the same or different.) (In the two Rf1s in formula (AJ), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20. The average degrees of polymerization in the two Rf1s may be the same or different.) (In the two Rf1s in formula (AK), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20. The average degrees of polymerization in the two Rf1s may be the same or different.) (In the two Rf1s in formula (AL), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20. The average degrees of polymerization in the two Rf1s may be the same or different.)

[0156] [ka] (In the two Rf1s in formula (AM), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20. The average degrees of polymerization in the two Rf1s may be the same or different.) (In the two Rf1s in formula (AN), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20. The average degrees of polymerization in the two Rf1s may be the same or different.) (In the two Rf1s in formula (AO), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20. The average degrees of polymerization in the two Rf1s may be the same or different.) (In the two Rf1s in formula (AP), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20. The average degrees of polymerization in the two Rf1s may be the same or different.)

[0157] [ka] (In the two Rf1s in formula (AQ), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20. The average degrees of polymerization in the two Rf1s may be the same or different.) (In the two Rf1s in formula (AR), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20. The average degrees of polymerization in the two Rf1s may be the same or different.) (In the two Rf1s in formula (AS), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20. The average degrees of polymerization in the two Rf1s may be the same or different.) (In the two Rf1s in formula (AT), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20. The average degrees of polymerization in the two Rf1s may be the same or different.)

[0158] [ka] (In the two Rf2s in formula (BA), j represents the average degree of polymerization and represents 1 to 15. The average degrees of polymerization in the two Rf2s may be the same or different.) (In the two Rf3s in formula (BB), k represents the average degree of polymerization and represents 1 to 10. The average degrees of polymerization in the two Rf3s may be the same or different.) (In the two Rf1s in formula (BC), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20. The average degrees of polymerization in the two Rf1s may be the same or different.) (In the two Rf1s in formula (BD), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20. The average degrees of polymerization in the two Rf1s may be the same or different.)

[0159] [ka] (In the two Rf1s in formula (BE), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20. The average degrees of polymerization in the two Rf1s may be the same or different.) (In the two Rf1s in formula (BF), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20. The average degrees of polymerization in the two Rf1s may be the same or different.) (In the two Rf1s in formula (BG), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20. The average degrees of polymerization in the two Rf1s may be the same or different.) (In the two Rf1s in formula (BH), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20. The average degrees of polymerization in the two Rf1s may be the same or different.)

[0160] [ka] (In the two Rf1s in formula (BI), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20. The average degrees of polymerization in the two Rf1s may be the same or different.) (In the two Rf1s in formula (BJ), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20. The average degrees of polymerization in the two Rf1s may be the same or different.) (In the two Rf1s in formula (BK), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20. The average degrees of polymerization in the two Rf1s may be the same or different.) (In the two Rf1s in formula (BL), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20. The average degrees of polymerization in the two Rf1s may be the same or different.)

[0161] [ka] (In the two Rf1s in formula (BM), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20. The average degrees of polymerization in the two Rf1s may be the same or different.) (In the two Rf1s in formula (BN), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20. The average degrees of polymerization in the two Rf1s may be the same or different.) (In the two Rf1s in formula (BO), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20. The average degrees of polymerization in the two Rf1s may be the same or different.)

[0162] [ka] (In the two Rf1s in formula (BP), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20. The average degrees of polymerization in the two Rf1s may be the same or different. Me represents a methyl group.) (In the two Rf1s in formula (BQ), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20. The average degrees of polymerization in the two Rf1s may be the same or different.) (In the two Rf1s in formula (BR), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20. The average degrees of polymerization in the two Rf1s may be the same or different.)

[0163] [ka] (In the three Rf1s in formula (CA), h and i represent an average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. Some or all of h and i in the three Rf1s may be the same, or may be different from each other.) (In the three Rf1s in formula (CB), h and i represent an average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. Some or all of h and i in the three Rf1s may be the same, or may be different from each other.) (In the three Rf1s in formula (CC), h and i represent an average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. Some or all of h and i in the three Rf1s may be the same, or may be different from each other.) (In the three Rf1s in formula (CD), h and i represent an average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. Some or all of h and i in the three Rf1s may be the same, or may be different from each other.)

[0164] [ka] (In the three Rf1s in formula (CE), h and i represent an average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. Some or all of h and i in the three Rf1s may be the same, or may be different from each other.) (In the three Rf1s in formula (CF), h and i represent an average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. Some or all of h and i in the three Rf1s may be the same, or may be different from each other.) (In the three Rf1s in formula (CG), h and i represent an average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. Some or all of h and i in the three Rf1s may be the same, or may be different from each other.)

[0165] [ka] (In the three Rf1s in formula (CH), h and i represent an average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. Some or all of h and i in the three Rf1s may be the same, or may be different from each other.) (In the three Rf1s in formula (CI), h and i represent an average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. Some or all of h and i in the three Rf1s may be the same, or may be different from each other.) (In the three Rf1s in formula (CJ), h and i represent an average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. Some or all of h and i in the three Rf1s may be the same, or may be different from each other.)

[0166] [ka] (In the three Rf2 in formula (DA), j represents the average degree of polymerization and represents 1 to 15. In the three Rf2, some or all of the average degrees of polymerization may be the same, or may be different from each other.) (In the three Rf1s in formula (DB), h and i represent an average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. Some or all of h and i in the three Rf1s may be the same, or may be different from each other.) (In the three Rf1s in formula (DC), h and i represent an average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. Some or all of h and i in the three Rf1s may be the same, or may be different from each other.) (In the three Rf1s in formula (DD), h and i represent an average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. Some or all of h and i in the three Rf1s may be the same, or may be different from each other.)

[0167] [ka] (In the three Rf1s in formula (DE), h and i represent an average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. Some or all of h and i in the three Rf1s may be the same, or may be different from each other.) (In the three Rf1s in formula (DF), h and i represent an average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. Some or all of h and i in the three Rf1s may be the same, or may be different from each other.) (In the three Rf1s in formula (DG), h and i represent an average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. Some or all of h and i in the three Rf1s may be the same, or may be different from each other.)

[0168] [ka] (In the two Rf1s in formula (EA), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20. The average degrees of polymerization in the two Rf1s may be the same or different.) (In the two Rf1s in formula (EB), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20. The average degrees of polymerization in the two Rf1s may be the same or different.) (In the two Rf1s in formula (EC), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20. The average degrees of polymerization in the two Rf1s may be the same or different.)

[0169] The fluorine-containing ether compound of this embodiment preferably has a number average molecular weight (Mn) in the range of 500 to 10,000, particularly preferably in the range of 1,000 to 5,000. When the number average molecular weight is 500 or more, a lubricating layer made of a 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 more preferably 1,000 or more. Furthermore, when the number average molecular weight is 10,000 or less, the viscosity of the fluorine-containing ether compound becomes appropriate, and by applying a lubricant containing this, a thin lubricating layer can be easily formed. The number average molecular weight of the fluorine-containing ether compound is preferably 5,000 or less, so that the viscosity becomes easy to handle when applied to a lubricant.

[0170] The number average molecular weight (Mn) of fluorine-containing ether compounds was measured using AVANCEIII400 manufactured by Bruker Biospin. 1 H-NMR and 19 These are values ​​measured by F-NMR. Specifically, 19 The number of repeating units of the PFPE chain is calculated from the integrated value measured by F-NMR to determine the number average molecular weight. For NMR (nuclear magnetic resonance) measurements, the sample is diluted in a hexafluorobenzene / d-acetone (4 / 1 v / v) solvent and measured. 19 The reference for F-NMR chemical shifts is the hexafluorobenzene peak at -164.7 ppm.1 The reference for H-NMR chemical shifts is the acetone peak at 2.2 ppm.

[0171] The fluorine-containing ether compound of this embodiment is preferably subjected to molecular weight fractionation by an appropriate method to make the molecular weight dispersity (ratio of weight average molecular weight (Mw) / number average molecular weight (Mn)) 1.3 or less. In this embodiment, the method for molecular weight fractionation is not particularly limited, but for example, molecular weight fractionation by silica gel column chromatography, gel permeation chromatography (GPC), or the like, molecular weight fractionation by supercritical extraction, or the like can be used.

[0172] "Manufacturing method" The method for producing the fluorinated ether compound of the present embodiment is not particularly limited, and the compound can be produced by a conventionally known production method. The fluorinated ether compound of the present embodiment can be produced, for example, by the production method shown below.

[0173] [First manufacturing method (x is 1)] (R 1 and R 4 and are the same, and the two R 2 are the same) R in Equation (1) 2 A fluorine-based compound is prepared in which a hydroxymethyl group (-CH2OH) is placed at each end of the perfluoropolyether chain corresponding to the above. Next, the hydroxyl group of the hydroxymethyl group located at one end of the fluorine-based compound and R 1 The group corresponding to (=R 4 (first reaction) with an epoxy compound having a group corresponding to R 2 At one end of the perfluoropolyether chain corresponding to 1 The group corresponding to (=R 4 An intermediate compound 1 having a group corresponding to

[0174] R in Equation (1) 1 The group corresponding to (=R4 Examples of epoxy compounds having a group corresponding to the following formula (5-1) include compounds represented by the following formulas (5-1) to (5-16). THP in the following formulas (5-1) to (5-13) represents a tetrahydropyranyl group. Me in the following formula (5-14) represents a methyl group.

[0175] [ka]

[0176] R in Equation (1) 1 The group corresponding to (=R 4 The epoxy compound having a group corresponding to R in formula (1) can be produced by the following method. 1 or R 4 The diol can be produced by a method in which a diol having a structure corresponding to a part of the terminal group represented by the formula (I) is prepared, one of the hydroxyl groups is protected by a known method, and then the diol is reacted with a halogen compound such as a bromine compound having an epoxy group or a chlorine compound having an epoxy group. For example, the compound of formula (5-2) can be produced by protecting one of the hydroxyl groups of 1,3-propanediol with dihydropyran (DHP) and reacting it with epibromohydrin, as shown in the following formula (6-1): THP in the following formula (6-1) represents a tetrahydropyranyl group.

[0177] [ka]

[0178] The epoxy compound may be produced by the following method: 2-(2-bromoethoxy)tetrahydro-2H-pyran and R 1 or R 4 The resulting compound is then reacted with m-chloroperbenzoic acid (mCPBA) to oxidize it. For example, the compound of formula (5-4) can be produced by reacting 2-(2-bromoethoxy)tetrahydro-2H-pyran with 3-buten-1-ol, followed by oxidation with m-chloroperbenzoic acid, as shown in formula (6-2) below: THP in formula (6-2) represents a tetrahydropyranyl group.

[0179] [ka]

[0180] The epoxy compound may be produced by the following method: 1 or R 4 An epoxy compound having a structure corresponding to a part of the terminal group represented by the formula (1) and having a hydroxyl group protected by a protecting group at one end is produced by a known method. 1 or R 4 The compound obtained by the addition reaction is then subjected to an addition reaction with an alcohol having an alkenyl group corresponding to part of the terminal group represented by the formula (I). The compound obtained is then oxidized by the action of m-chloroperbenzoic acid (mCPBA). Before the compound obtained by the addition reaction is oxidized by the action of m-chloroperbenzoic acid (mCPBA), the hydroxyl group generated by the addition reaction may be protected by a known method.

[0181] For example, the compound of formula (5-5) can be produced by the addition reaction of the epoxy compound of formula (5-1) with allyl alcohol, protecting the resulting hydroxyl group with dihydropyran (DHP) and oxidizing it with m-chloroperbenzoic acid (mCPBA), as shown in formula (6-3) below: THP in formula (6-3) represents a tetrahydropyranyl group.

[0182] [ka]

[0183] Thereafter, the hydroxyl group of the hydroxymethyl group located at one end of the intermediate compound 1 produced in the first reaction described above is reacted with the R 3 is reacted with a compound having two corresponding epoxy groups (second reaction). R in Equation (1) 3 As a compound having two epoxy groups corresponding to the above, for example, compounds represented by the following formulae (7-1) to (7-20) can be used: THP in the following formulae (7-15) to (7-17) represents a tetrahydropyranyl group.

[0184] [ka]

[0185] R in Equation (1) 3 A compound having two epoxy groups corresponding to R can be prepared using the method shown below. 3 and a dihalogen compound having a group corresponding to a part of the linking group represented by R 3 The dihalogen compound is reacted with the hydroxyl group of an alcohol having an alkenyl group corresponding to a portion of the linking group represented by the formula (1). At this time, the dihalogen compound is reacted with an alcohol having an alkenyl group in an amount twice the molar amount of the dihalogen compound. The resulting compound is then oxidized with m-chloroperbenzoic acid (mCPBA) to produce the compound.

[0186] For example, the compound represented by formula (7-1) can be produced by reacting 1,4-dibromobutane with twice the molar amount of 3-buten-1-ol, followed by oxidation with m-chloroperbenzoic acid, as shown in the following formula (8-1).

[0187] [ka]

[0188] R in Equation (1) 3A compound having two epoxy groups corresponding to R may be prepared by the following method. 3 and a hydroxyl group of a diol having a group corresponding to a part of a linking group represented by R 3 The diol is reacted with a halogen compound having an alkenyl group corresponding to a portion of the linking group represented by the formula: In this case, twice the molar amount of the halogen compound as the diol is reacted with the diol. The resulting compound is then oxidized with m-chloroperbenzoic acid (mCPBA) to produce the compound.

[0189] For example, the compound represented by formula (7-6) can be produced by reacting 2,2-dimethyl-1,3-propanediol with twice the molar amount of 5-bromo-1-pentene, followed by oxidation with m-chloroperbenzoic acid, as shown in formula (8-2) below.

[0190] [ka]

[0191] R in Equation (1) 3 A compound having two epoxy groups corresponding to R may be prepared by the following method. 3 and a halogen compound having an epoxy group corresponding to a part of the linking group represented by R 3 The halogen compound is subjected to an addition reaction with an alcohol having an alkenyl group corresponding to a portion of the linking group represented by the formula:

[0044] In this case, the alcohol having an alkenyl group is reacted with the halogen compound in an amount twice the molar amount of the halogen compound. The resulting compound is then oxidized with m-chloroperbenzoic acid (mCPBA), thereby producing the compound. Before the compound obtained by the addition reaction is oxidized with m-chloroperbenzoic acid (mCPBA), the hydroxyl group generated by the addition reaction may be protected by a known method.

[0192] For example, the compound of formula (7-15) can be produced by the addition reaction of epibromohydrin with twice the molar amount of 3-buten-1-ol, followed by protecting the hydroxyl group generated by the addition reaction with dihydropyran (DHP) and oxidizing it with m-chloroperbenzoic acid (mCPBA), as shown in formula (8-3) below: THP in formula (8-3) represents a tetrahydropyranyl group.

[0193] [ka]

[0194] After the second reaction, a deprotection reaction is carried out using a known method to obtain a compound represented by the formula (1) in which x is 1 and R 1 and R 4 and are the same, and the two R 2 can be prepared.

[0195] [Second manufacturing method (when x is 1)] (R 1 and R 4 and differ, and / or two R 2 are different) First, R 1 Side R 2 The hydroxyl group at one end of the perfluoropolyether chain of the fluorine-based compound, which has a hydroxymethyl group at each end, corresponds to R 1 An epoxy compound having a group corresponding to the formula (I) is reacted with the compound to obtain intermediate compound 1a (first reaction). Next, R 4 Side R 2 The hydroxyl group at one end of the perfluoropolyether chain of the fluorine-based compound, which has a hydroxymethyl group at each end, corresponds to R 4 An epoxy compound having a group corresponding to the formula (II) is reacted to obtain intermediate compound 1b (second reaction).

[0196] Next, the hydroxyl group at one end of the intermediate compound 1a is reacted with the R 3After reacting with a compound having an epoxy group and an alkenyl group corresponding to the above, the double bond of the resulting compound is oxidized to obtain intermediate compound 1-2 (third reaction). R in Equation (1) 3 As the compound having an epoxy group and an alkenyl group corresponding to the above, for example, compounds represented by the formulae (9-1) to (9-20) described below can be used.

[0197] Next, the hydroxyl group at one end of the intermediate compound 1b is reacted with the epoxy group of the intermediate compound 1-2 obtained in the third reaction (fourth reaction). After the above steps, a deprotection reaction is carried out using a known method to obtain a compound represented by the formula (1) where x is 1 and R 1 and R 4 and differ, and / or two R 2 can be prepared.

[0198] [Third manufacturing method (when x is 2)] (R 1 and R 4 are the same, and the two R 3 is the same, and R 1 Side R 2 and R 4 Side R 2 are the same) First, in the same manner as in the first manufacturing method, R 1 Side and R 4 Side R 2 At one end of the perfluoropolyether chain corresponding to 1 The group corresponding to (=R 4 (a group corresponding to the formula:) is obtained (first reaction).

[0199] Next, R in the center of the molecule in formula (1) 2 A fluorine-based compound having a hydroxymethyl group (-CHOH) at each end of a perfluoropolyether chain corresponding to formula (1) is prepared. Then, the hydroxyl groups of the hydroxymethyl groups at both ends of the fluorine-based compound are reacted with the R 3is reacted with a compound having an epoxy group and an alkenyl group corresponding to the above to obtain intermediate compound 2-1 (second reaction).

[0200] R in Equation (1) 3 Examples of compounds having an epoxy group and an alkenyl group corresponding to the above formulas include compounds represented by the following formulas (9-1) to (9-20): THP in the following formulas (9-15) to (9-17) represents a tetrahydropyranyl group.

[0201] [ka]

[0202] R in Equation (1) 3 The compound having an epoxy group and an alkenyl group corresponding to R 3 and a dihalogen compound having a group corresponding to a part of the linking group represented by R 3 The dihalogen compound is reacted with the hydroxyl group of an alcohol having an alkenyl group corresponding to part of the linking group represented by the formula: In this case, the dihalogen compound is reacted with an alcohol having an alkenyl group in an amount twice the molar amount of the dihalogen compound. Then, the resulting compound is reacted with m-chloroperbenzoic acid (mCPBA) to oxidize one of the alkenyl groups, which can be used to produce the compound.

[0203] For example, the compound represented by formula (9-1) can be produced by reacting 1,4-dibromobutane with twice the molar amount of 3-buten-1-ol, followed by oxidation with m-chloroperbenzoic acid, as shown in the following formula (10-1).

[0204] [ka]

[0205] R in Equation (1) 3The compound having an epoxy group and an alkenyl group corresponding to R may be prepared by the following method. 3 and a hydroxyl group of a diol having a group corresponding to a part of a linking group represented by R 3 The diol is reacted with a halogen compound having an alkenyl group corresponding to part of the linking group represented by the formula: In this case, twice the molar amount of the halogen compound as the diol is reacted with the diol. Then, the resulting compound is reacted with m-chloroperbenzoic acid (mCPBA) to oxidize one of the alkenyl groups, which can be used to produce the compound.

[0206] For example, the compound represented by formula (9-6) can be produced by reacting 2,2-dimethyl-1,3-propanediol with twice the molar amount of 5-bromo-1-pentene, followed by oxidation with m-chloroperbenzoic acid, as shown in formula (10-2) below.

[0207] [ka]

[0208] R in Equation (1) 3 The compound having an epoxy group and an alkenyl group corresponding to R may be prepared by the following method. 3 and a halogen compound having an epoxy group corresponding to a part of the linking group represented by R 3 The halogen compound is subjected to an addition reaction with an alcohol having an alkenyl group corresponding to part of the linking group represented by the formula:

[0033] . At this time, twice the molar amount of the alcohol having an alkenyl group as the halogen compound is reacted with the halogen compound. The resulting compound is then reacted with m-chloroperbenzoic acid (mCPBA) to oxidize one of the alkenyl groups, thereby producing the compound. Before the compound obtained by the addition reaction is reacted with m-chloroperbenzoic acid (mCPBA) to oxidize it, the hydroxyl group generated by the addition reaction may be protected by a known method.

[0209] For example, the compound of formula (9-15) can be produced by the addition reaction of epibromohydrin with twice the molar amount of 3-buten-1-ol, followed by protecting the resulting hydroxyl group with dihydropyran (DHP) and oxidizing it with m-chloroperbenzoic acid (mCPBA), as shown in formula (10-3) below. THP in formula (10-3) represents a tetrahydropyranyl group.

[0210] [ka]

[0211] Next, the intermediate compound 2-1 produced in the second reaction is oxidized by the action of m-chloroperbenzoic acid (mCPBA) (third reaction). This results in the formation of the R 2 At both ends of the perfluoropolyether chain corresponding to the two R 3 This gives an intermediate compound 3-1 having an epoxy group corresponding to the following: The third reaction may be carried out after the hydroxyl group of the intermediate compound 2-1 is appropriately protected by a known method.

[0212] Thereafter, the hydroxyl group of the hydroxymethyl group located at one end of the intermediate compound 1 is reacted with the epoxy groups located at both ends of the intermediate compound 3-1 (fourth reaction).

[0213] After the above steps, a deprotection reaction is carried out to obtain a compound represented by the formula (1) where x is 2 and R 1 and R 4 are the same, and the two R 3 is the same, and R 1 Side R 2 and R 4 Side R 2 can be prepared.

[0214] [4th manufacturing method (when x is 2)] (R 1 Side R 3 and R 4 Side R3 and are the same, and R 1 and R 4 and / or R 1 Side R 2 and R 4 Side R 2 are different) In the first reaction of the third production method, intermediate compound 1a and intermediate compound 1b are obtained in place of intermediate compound 1 in the second production method. Next, intermediate compound 3-1 is obtained in the same manner as in the second and third reactions of the third production method. Then, intermediate compound 1a and intermediate compound 1b are sequentially reacted with the epoxy groups located at both ends of intermediate compound 3-1, respectively.

[0215] After the above steps, a deprotection reaction is carried out to obtain a compound represented by the formula (1) where x is 2 and R 1 Side R 3 and R 4 Side R 3 and are the same, and R 1 and R 4 and / or R 1 Side R 2 and R 4 Side R 2 can be prepared.

[0216] [5th ​​manufacturing method (x is 2)] (R 1 Side R 3 and R 4 Side R 3 Unlike R 1 and R 4 and are the same, and R 1 Side R 2 and R 4 Side R 2 are the same) In the second reaction of the third production method, R 3 Instead of a compound having an epoxy group and an alkenyl group, R 1 Side R 3 and a compound having an epoxy group and an alkenyl group corresponding to R in formula (1). 4 Side R3 The fluorine-based compound is reacted with a compound having an epoxy group and an alkenyl group corresponding to the formula (I) to obtain intermediate compound 2-2. Then, the third and fourth reactions are carried out in the same manner as in the third production method, except that intermediate compound 2-2 is used instead of intermediate compound 2-1.

[0217] After the above steps, a deprotection reaction is carried out to obtain a compound represented by the formula (1) where x is 2 and R 1 Side R 3 and R 4 Side R 3 Unlike R 1 and R 4 and are the same, and R 1 Side R 2 and R 4 Side R 2 can be prepared. In the third to fifth production methods for producing a compound in which x is 2, R 2 The perfluoropolyether chain corresponding to the other R 2 It may be the same as or different from.

[0218] [Lubricants for magnetic recording media] The lubricant for a magnetic recording medium of this embodiment contains a fluorine-containing ether compound represented by the above formula (1). The lubricant of the present embodiment can be used by mixing, as needed, known materials used as lubricant materials, as long as the properties resulting from the inclusion of the fluorinated ether compound represented by the above formula (1) are not impaired.

[0219] Specific examples of known materials include FOMBLIN (registered trademark) ZDIAC, FOMBLIN ZDEAL, FOMBLIN AM-2001 (all manufactured by Solvay Solexis), Moresco A20H (manufactured by Moresco), etc. The known material to be mixed with the lubricant of the present embodiment preferably has a number average molecular weight of 1,000 to 10,000.

[0220] When the lubricant of the present embodiment contains a material other than the fluorinated ether compound represented by the above formula (1), the content of the fluorinated ether compound represented by the above formula (1) in the lubricant of the present embodiment is preferably 70 mass% or more, more preferably 90 mass% or more, and even more preferably 95 mass% or more.

[0221] The lubricant of this embodiment contains the fluorine-containing ether compound represented by the above formula (1), and therefore has excellent corrosion resistance and can form a lubricating layer that is highly effective in suppressing spin-off.

[0222] [Magnetic recording media] The magnetic recording medium of this embodiment has at least a magnetic layer, a protective layer, and a lubricating layer provided in this order on a substrate. In the magnetic recording medium of this embodiment, one or more underlayers may be provided between the substrate and the magnetic layer, as needed, and at least one of an adhesive layer and a soft magnetic layer may also be provided between the underlayer and the substrate.

[0223] FIG. 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 adhesive layer 12, a soft magnetic layer 13, a first underlayer 14, a second underlayer 15, a magnetic layer 16, a protective layer 17, and a lubricating layer 18 are sequentially provided on a substrate 11.

[0224] "substrate" The substrate 11 may be, for example, a non-magnetic substrate in which a film made of NiP or a NiP alloy is formed on a base made of a metal or alloy material such as Al or an Al alloy. The substrate 11 may be a non-magnetic substrate made of a non-metallic material such as glass, ceramics, silicon, silicon carbide, carbon, or resin, or may be a non-magnetic substrate having a NiP or NiP alloy film formed on a base made of any of these non-metallic materials.

[0225] "Adhesion layer" The adhesive layer 12 prevents the progress of corrosion of the substrate 11, which occurs when the substrate 11 and the soft magnetic layer 13 provided on the adhesive layer 12 are disposed in contact with each other. The material of the adhesive layer 12 can be appropriately selected from, for example, Cr, a Cr alloy, Ti, a Ti alloy, CrTi, NiAl, an AlRu alloy, etc. The adhesive layer 12 can be formed by, for example, a sputtering method.

[0226] "Soft magnetic layer" The soft magnetic layer 13 preferably has a structure in which a first soft magnetic film, an intermediate layer made of a Ru film, and a second soft magnetic film are laminated in this order. That is, the soft magnetic layer 13 preferably has a structure in which the intermediate layer made of a Ru film is sandwiched between two soft magnetic films, and the soft magnetic films above and below the intermediate layer are antiferro-coupling (AFC).

[0227] The first and second soft magnetic films may be made of a material such as a CoZrTa alloy or a CoFe alloy. It is preferable to add Zr, Ta, or Nb to the CoFe alloy used in the first and second soft magnetic films. This promotes the amorphization of the first and second soft magnetic films. As a result, it is possible to improve the orientation of the first underlayer (seed layer) and reduce the flying height of the magnetic head. The soft magnetic layer 13 can be formed by, for example, a sputtering method.

[0228] "First base layer" The first underlayer 14 is a layer that controls the orientation and crystal size of the second underlayer 15 and magnetic layer 16 that are provided thereon. The first underlayer 14 may be, for example, a Cr layer, a Ta layer, a Ru layer, or a CrMo alloy layer, a CoW alloy layer, a CrW alloy layer, a CrV alloy layer, or a CrTi alloy layer. The first underlayer 14 can be formed by, for example, a sputtering method.

[0229] "Second base layer" The second underlayer 15 is a layer that controls the orientation of the magnetic layer 16. The second underlayer 15 is preferably a layer made of Ru or a Ru alloy. The second underlayer 15 may be a single layer or may be composed of multiple layers. When the second underlayer 15 is composed of multiple layers, all of the layers may be composed of the same material, or at least one layer may be composed of a different material. The second underlayer 15 can be formed by, for example, a sputtering method.

[0230] "Magnetic layer" The magnetic layer 16 is a magnetic film whose easy axis of magnetization is oriented perpendicular or parallel to the substrate surface. The magnetic layer 16 contains Co and Pt. To improve the SNR characteristics, the magnetic layer 16 may contain oxides, Cr, B, Cu, Ta, Zr, or the like. Examples of oxides contained in the magnetic layer 16 include SiO2, SiO, Cr2O3, CoO, Ta2O3, and TiO2.

[0231] The magnetic layer 16 may be composed of a single layer, or may be composed of multiple magnetic layers made of materials with different compositions. For example, when the magnetic layer 16 is composed of three layers, namely, a first magnetic layer, a second magnetic layer, and a third magnetic layer, stacked in this order from bottom to top, the first magnetic layer preferably has a granular structure made of a material containing Co, Cr, and Pt and further containing an oxide. The oxide contained in the first magnetic layer is preferably an oxide of Cr, Si, Ta, Al, Ti, Mg, Co, or the like. Among these, TiO2, Cr2O3, SiO2, or the like is particularly suitable. The first magnetic layer is preferably made of a composite oxide containing two or more types of oxides. Among these, Cr2O3-SiO2, Cr2O3-TiO2, SiO2-TiO2, or the like is particularly suitable. In addition to Co, Cr, Pt, and an oxide, the first magnetic layer may contain one or more elements selected from B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb, Ru, and Re.

[0232] The second magnetic layer can be made of the same material as the first magnetic layer, and preferably has a granular structure. The third magnetic layer preferably has a non-granular structure made of a material containing Co, Cr, and Pt and not containing oxides, and may contain one or more elements selected from B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb, Ru, Re, and Mn in addition to Co, Cr, and Pt.

[0233] When magnetic layer 16 is formed of multiple magnetic layers, it is preferable to provide a non-magnetic layer between adjacent magnetic layers. When magnetic layer 16 is formed of three layers, namely, a first magnetic layer, a second magnetic layer, and a third magnetic layer, it is preferable to provide a non-magnetic layer between the first magnetic layer and the second magnetic layer and between the second magnetic layer and the third magnetic layer.

[0234] The non-magnetic layer provided between adjacent magnetic layers of the magnetic layer 16 can suitably be made of, for example, Ru, a Ru alloy, a CoCr alloy, or a CoCrX1 alloy (X1 represents one or more elements selected from Pt, Ta, Zr, Re, Ru, Cu, Nb, Ni, Mn, Ge, Si, O, N, W, Mo, Ti, V, and B).

[0235] The non-magnetic layer provided between adjacent magnetic layers of the magnetic layer 16 preferably uses an alloy material containing an oxide, metal nitride, or metal carbide. Specifically, oxides that can be used include, for example, SiO2, Al2O3, Ta2O5, Cr2O3, MgO, Y2O3, and TiO2. Metal nitrides that can be used include, for example, AlN, Si3N4, TaN, and CrN. Metal carbides that can be used include, for example, TaC, BC, and SiC. The non-magnetic layer can be formed by, for example, a sputtering method.

[0236] To achieve higher recording density, the magnetic layer 16 is preferably a magnetic layer for perpendicular magnetic recording, in which the axis of easy magnetization is oriented perpendicular to the substrate surface, but may also be a magnetic layer for longitudinal magnetic recording. The magnetic layer 16 may be formed by any conventionally known method such as vapor deposition, ion beam sputtering, magnetron sputtering, etc. The magnetic layer 16 is usually formed by sputtering.

[0237] "Protective layer" The protective layer 17 protects the magnetic layer 16. The protective layer 17 may be composed of one layer or multiple layers. A carbon-based protective layer is preferably used as the protective layer 17, and an amorphous carbon protective layer is particularly preferred. If the protective layer 17 is a carbon-based protective layer, the interaction with the polar groups (particularly hydroxyl groups) contained in the fluorine-containing ether compound in the lubricating layer 18 is further enhanced, which is preferable.

[0238] The adhesion between the carbon-based protective layer and the lubricating layer 18 can be controlled by using hydrogenated carbon and / or nitrogenated carbon for the carbon-based protective layer and adjusting the hydrogen and / or nitrogen content in the carbon-based protective layer. The hydrogen content in the carbon-based protective layer is preferably 3 atomic % to 20 atomic % when measured by hydrogen forward scattering (HFS). The nitrogen content in the carbon-based protective layer is preferably 4 atomic % to 15 atomic % when measured by X-ray photoelectron spectroscopy (XPS).

[0239] The hydrogen and / or nitrogen contained in the carbon-based protective layer does not need to be uniformly contained throughout the carbon-based protective layer. The carbon-based protective layer is preferably a compositionally graded layer, for example, in which nitrogen is contained on the lubricating layer 18 side of protective layer 17 and hydrogen is contained on the magnetic layer 16 side of protective layer 17. In this case, the adhesion between the magnetic layer 16 and lubricating layer 18 and the carbon-based protective layer is further improved.

[0240] The thickness of the protective layer 17 is preferably 1 nm to 7 nm. When the thickness of the protective layer 17 is 1 nm or more, sufficient performance as the protective layer 17 can be obtained. When the thickness of the protective layer 17 is 7 nm or less, it is preferable from the viewpoint of making the protective layer 17 thinner.

[0241] The protective layer 17 can be formed by sputtering using a target material containing carbon, chemical vapor deposition (CVD) using a hydrocarbon raw material such as ethylene or toluene, or ion beam deposition (IBD). When a carbon-based protective layer is formed as protective layer 17, it can be deposited by, for example, DC magnetron sputtering. In particular, when a carbon-based protective layer is formed as protective layer 17, it is preferable to deposit an amorphous carbon protective layer by plasma CVD. The amorphous carbon protective layer deposited by plasma CVD has a uniform surface with little roughness.

[0242] "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 / reproducing device that slides on the magnetic recording medium 10, thereby improving the durability of the magnetic recording medium 10. 1, the lubricating layer 18 is formed on and in contact with the protective layer 17. The lubricating layer 18 is formed by applying the magnetic recording medium lubricant of the above-described embodiment onto the protective layer 17. Therefore, the lubricating layer 18 contains the above-described fluorine-containing ether compound.

[0243] When the protective layer 17 disposed below the lubricating layer 18 is a carbon-based protective layer, the lubricating layer 18 bonds with the protective layer 17 with particularly high bonding strength. As a result, even if the thickness of the lubricating layer 18 is thin, it becomes easier to obtain a magnetic recording medium 10 in which the surface of the protective layer 17 is covered with a high coverage, and contamination of the surface of the magnetic recording medium 10 can be effectively prevented.

[0244] 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 an island or mesh-like structure. Therefore, the surface of the protective layer 17 can be covered with the lubricating layer 18 at a high coverage rate. Furthermore, by setting the average thickness of the lubricating layer 18 to 2.0 nm or less, the lubricating layer 18 can be made sufficiently thin, and the flying height of the magnetic head can be made sufficiently small.

[0245] "Method for forming lubricating layer" A method for forming the lubricating layer 18 includes, for example, preparing a magnetic recording medium in the middle of manufacturing in which all layers up to the protective layer 17 are formed on the substrate 11, applying a solution for forming a lubricating layer onto the protective layer 17, and drying the solution.

[0246] The lubricant layer forming solution can be obtained by dispersing and dissolving the lubricant for a magnetic recording medium according to the above embodiment in a solvent as needed, and adjusting the viscosity and concentration to suit the coating method. Examples of the solvent used in the lubricating layer-forming solution include fluorine-based solvents such as Vertrel (registered trademark) XF (trade name, manufactured by Mitsui DuPont Fluorochemicals Co., Ltd.).

[0247] The method for applying the lubricating layer-forming solution is not particularly limited, but examples thereof include spin coating, spraying, paper coating, and dipping. When using the dipping method, for example, the following method can be used. First, the substrate 11 on which each layer up to the protective layer 17 has been formed is immersed in a lubricant layer-forming solution placed in an immersion tank of a dip coating device. Next, the substrate 11 is lifted from the immersion tank at a predetermined speed. In this way, the lubricant layer-forming solution is applied to the surface of the substrate 11 above the protective layer 17. By using the dipping method, the lubricating layer forming solution can be applied uniformly to the surface of the protective layer 17, and the lubricating layer 18 can be formed on the protective layer 17 with a uniform thickness.

[0248] In this embodiment, it is preferable to perform a heat treatment on the substrate 11 on which the lubricating layer 18 is formed. By performing the heat treatment, the adhesion between the lubricating layer 18 and the protective layer 17 is improved, and the adhesive force between the lubricating layer 18 and the protective layer 17 is also improved. The heat treatment temperature is preferably 100°C to 180°C, and more preferably 100°C to 160°C. When 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 the heat treatment can be prevented. The heat treatment time can be adjusted appropriately depending on the heat treatment temperature, and is preferably 10 minutes to 120 minutes.

[0249] In this embodiment, in order to further improve the adhesive strength of the lubricating layer 18 to the protective layer 17, the lubricating layer 18 may be irradiated with ultraviolet (UV) rays before or after the heat treatment.

[0250] The magnetic recording medium 10 of this embodiment includes at least a magnetic layer 16, a protective layer 17, and a lubricating layer 18, which are sequentially formed on a substrate 11. In the magnetic recording medium 10 of this embodiment, a lubricating layer 18 containing the above-described fluorine-containing ether compound is formed on and in contact with the protective layer 17. Even with a thin film thickness, this lubricating layer 18 has good corrosion resistance and a high spin-off suppression effect. Therefore, the magnetic recording medium 10 of this embodiment has excellent reliability, particularly corrosion resistance and spin-off suppression, and durability. As a result, the magnetic recording medium 10 of this embodiment can contribute to reducing magnetic spacing, reduce the magnetic head flying height (e.g., 10 nm or less), and operate stably for long periods of time, even in harsh environments associated with diverse applications. Therefore, the magnetic recording medium 10 of this embodiment is particularly suitable as a magnetic disk to be installed in a magnetic disk device using the LUL (Load Unload) method. [Example]

[0251] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0252] [Example 1] The compound represented by the above formula (AA) was obtained by the method shown below. (First reaction) Place HOCH2CF2O (CF2CF2O) in a 100 mL recovery flask under a nitrogen gas atmosphere. h (CF2O) i 20 g of a compound (number average molecular weight 1000, molecular weight distribution 1.1) represented by CF2CH2OH (where h, representing the average degree of polymerization, is 4.5, and i, representing the average degree of polymerization, is 4.5), 4.14 g of a compound represented by the above formula (5-1), and 20 mL of t-butanol were charged and stirred at room temperature until homogeneous to form a mixture. 1.10 g of potassium tert-butoxide was added to this mixture, and the mixture was reacted by stirring at 70°C for 16 hours.

[0253] The compound represented by formula (5-1) was synthesized by protecting the hydroxyl group of ethylene glycol monoallyl ether with dihydropyran, followed by oxidation with m-chloroperbenzoic acid.

[0254] 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 over anhydrous sodium sulfate. After filtering off the desiccant, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 9.85 g of the compound represented by the following formula (11) as intermediate compound 1.

[0255] [ka] (Rf1 in formula (11) is a PFPE chain represented by the above formula (4-1). In Rf1, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5. THP represents a tetrahydropyranyl group.)

[0256] (Second reaction) Next, 9.61 g of the compound represented by formula (11), which is intermediate compound 1 obtained above, 0.79 g of the compound represented by formula (7-1), and 20 mL of t-butanol were charged into a 100 mL recovery flask under a nitrogen gas atmosphere, and the mixture was stirred at room temperature until it became homogeneous. 0.45 g of potassium tert-butoxide was added to the mixture, and the mixture was reacted by stirring at 70°C for 16 hours. The compound represented by formula (7-1) was synthesized by reacting 1,4-dibromobutane with twice the molar amount of 3-buten-1-ol, followed by oxidation with m-chloroperbenzoic acid (mCPBA).

[0257] After the reaction, the resulting reaction mixture was returned to room temperature, and 50 g of a 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. The reaction mixture was then transferred in small portions to a separatory funnel containing 100 mL of saturated aqueous sodium bicarbonate and extracted twice with 200 mL of ethyl acetate. The organic layer was washed sequentially with 100 mL of brine, 100 mL of saturated aqueous sodium bicarbonate, and 100 mL of brine, and then dehydrated using anhydrous sodium sulfate. After filtering off the desiccant, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 3.44 g of compound (AA). Rf1 in formula (AA) represents the PFPE chain represented by formula (4-1) above. For the two Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5.

[0258] The obtained compound (AA) 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-D6): δ[ppm]=1.65-1.85(8H), 3.40-3.85(38H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0259] [Example 2] The compound represented by the above formula (AB) was obtained by the method shown below. The same operations as in Example 1 were performed except that the compound represented by formula (7-2) was used instead of the compound represented by formula (7-1), to obtain 3.35 g of compound (AB) (Rf1 in formula (AB) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which represents the average degree of polymerization, is 4.5, and i, which represents the average degree of polymerization, is 4.5).

[0260] The compound represented by formula (7-2) was synthesized by reacting 1,4-dibromobutane with twice the molar amount of 5-hexen-1-ol, followed by oxidation with m-chloroperbenzoic acid (mCPBA).

[0261] The obtained compound (AB) 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-D6): δ[ppm]=1.65-1.85(16H), 3.40-3.85(38H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0262] [Example 3] The compound represented by the above formula (AC) was obtained by the method shown below. The same operations as in Example 1 were performed except that the compound represented by formula (7-3) was used instead of the compound represented by formula (7-1), to obtain 3.26 g of compound (AC) (Rf1 in formula (AC) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0263] The compound represented by formula (7-3) was synthesized by reacting 1,2-dibromoethane with twice the molar amount of 3-buten-1-ol, followed by oxidation with m-chloroperbenzoic acid (mCPBA).

[0264] The obtained compound (AC) 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-D6): δ[ppm]=1.65-1.85(4H), 3.40-3.85(38H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0265] [Example 4] The compound represented by the above formula (AD) was obtained by the method shown below. The same procedure as in Example 1 was performed, except that the compound represented by formula (7-4) was used instead of the compound represented by formula (7-1), to obtain 3.48 g of compound (AD) (Rf1 in formula (AD) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0266] The compound represented by formula (7-4) was synthesized by reacting 1,6-dibromohexane with twice the molar amount of 3-buten-1-ol, followed by oxidation with m-chloroperbenzoic acid (mCPBA).

[0267] 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-D6): δ[ppm]=1.65-1.85(12H), 3.40-3.85(38H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0268] [Example 5] The compound represented by the above formula (AE) was obtained by the method shown below. The same operation as in Example 1 was performed, except that the compound represented by formula (7-5) was used instead of the compound represented by formula (7-1), to obtain 3.52 g of compound (AE) (Rf1 in formula (AE) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which represents the average degree of polymerization, is 4.5, and i, which represents the average degree of polymerization, is 4.5).

[0269] The compound represented by formula (7-5) was synthesized by reacting 1,8-dibromooctane with twice the molar amount of 3-buten-1-ol, followed by oxidation with m-chloroperbenzoic acid (mCPBA).

[0270] The obtained compound (AE) 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-D6): δ[ppm]=1.65-1.85(16H), 3.40-3.85(38H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0271] [Example 6] The compound represented by the above formula (AF) was obtained by the method shown below. The same operation as in Example 1 was performed, except that the compound represented by formula (7-6) was used instead of the compound represented by formula (7-1), to obtain 3.36 g of compound (AF) (Rf1 in formula (AF) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which represents the average degree of polymerization, is 4.5, and i, which represents the average degree of polymerization, is 4.5).

[0272] The compound represented by formula (7-6) was synthesized by reacting 2,2-dimethyl-1,3-propanediol with twice the molar amount of 5-bromo-1-pentene, followed by oxidation with m-chloroperbenzoic acid (mCPBA).

[0273] The obtained compound (AF) 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-D6): δ[ppm]=0.90(6H), 1.65-1.85(4H), 3.40-3.85(38H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0274] [Example 7] The compound represented by the above formula (AG) was obtained by the method shown below. The same operations as in Example 1 were performed except that the compound represented by formula (7-7) was used instead of the compound represented by formula (7-1), to obtain 3.14 g of compound (AG) (Rf1 in formula (AG) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0275] The compound represented by formula (7-7) was synthesized by reacting 2,3-butanediol with twice the molar amount of 5-bromo-1-pentene, followed by oxidation with m-chloroperbenzoic acid (mCPBA).

[0276] The obtained compound (AG) 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-D6): δ[ppm]=1.15-1.20(6H), 1.65-1.85(4H), 3.40-3.85(36H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0277] [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 performed, except that the compound represented by formula (7-8) was used instead of the compound represented by formula (7-1), to obtain 3.41 g of compound (AH) (Rf1 in formula (AH) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0278] The compound represented by formula (7-8) was synthesized by brominating diethylene glycol with phosphorus tribromide (PBr3), reacting the compound with twice the molar amount of 3-buten-1-ol, and then oxidizing it with m-chloroperbenzoic acid (mCPBA).

[0279] The obtained compound (AH) 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-D6): δ[ppm]=1.65-1.85(4H), 3.40-3.85(42H), 3.85-4.10(8H) 19F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0280] [Example 9] The compound represented by the above formula (AI) was obtained by the method shown below. The same procedure as in Example 1 was performed, except that the compound represented by formula (7-9) was used instead of the compound represented by formula (7-1), to obtain 3.53 g of compound (AI) (Rf1 in formula (AI) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0281] The compound represented by formula (7-9) was synthesized by brominating tetraethylene glycol with phosphorus tribromide (PBr3), reacting the resulting compound with twice the molar amount of 3-buten-1-ol, and then oxidizing it with m-chloroperbenzoic acid (mCPBA).

[0282] The obtained compound (AI) 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-D6): δ[ppm]=1.65-1.85(4H), 3.40-3.85(50H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0283] [Example 10] The compound represented by the above formula (AJ) was obtained by the method shown below. The same procedure as in Example 1 was performed, except that the compound represented by formula (7-10) was used instead of the compound represented by formula (7-1), to obtain 3.32 g of compound (AJ) (Rf1 in formula (AJ) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0284] The compound represented by formula (7-10) was synthesized by brominating dipropylene glycol with phosphorus tribromide (PBr3), reacting the resulting compound with twice the molar amount of 3-buten-1-ol, and then oxidizing it with m-chloroperbenzoic acid (mCPBA).

[0285] The obtained compound (AJ) 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-D6): δ[ppm]=1.65-1.85(8H), 3.40-3.85(42H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0286] [Example 11] The compound represented by the above formula (AK) was obtained by the method shown below. The same operation as in Example 1 was performed, except that the compound represented by formula (7-11) was used instead of the compound represented by formula (7-1), to obtain 3.22 g of compound (AK) (Rf1 in formula (AK) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which represents the average degree of polymerization, is 4.5, and i, which represents the average degree of polymerization, is 4.5).

[0287] The compound represented by formula (7-11) was synthesized by brominating diethylene glycol with phosphorus tribromide (PBr3), reacting the resulting compound with twice the molar amount of 5-hexen-1-ol, and then oxidizing it with m-chloroperbenzoic acid (mCPBA).

[0288] The obtained compound (AK) 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-D6): δ[ppm]=1.65-1.85(12H), 3.40-3.85(42H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0289] [Example 12] The compound represented by the above formula (AL) was obtained by the method shown below. The same operation as in Example 1 was performed, except that the compound represented by formula (7-12) was used instead of the compound represented by formula (7-1), to obtain 3.53 g of compound (AL) (Rf1 in formula (AL) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which represents the average degree of polymerization, is 4.5, and i, which represents the average degree of polymerization, is 4.5).

[0290] The compound represented by formula (7-12) was synthesized by reacting 2,2,3,3-tetrafluoro-1,4-butanediol with twice the molar amount of 2-bromoethyloxirane.

[0291] The obtained compound (AL) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1H-NMR (acetone-D6): δ[ppm]=1.65-1.85(4H), 3.40-3.85(34H), 3.85-4.10(12H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F), -130.0(4F)

[0292] [Example 13] The compound represented by the above formula (AM) was obtained by the method shown below. The same operation as in Example 1 was performed, except that the compound represented by formula (7-13) was used instead of the compound represented by formula (7-1), to obtain 3.62 g of compound (AM) (Rf1 in formula (AM) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0293] The compound represented by formula (7-13) was synthesized by reacting 2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoro-1,8-octanediol with twice the molar amount of 2-bromoethyloxirane.

[0294] The obtained compound (AM) 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-D6): δ[ppm]=1.65-1.85(4H), 3.40-3.85(34H), 3.85-4.10(12H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F), -122.5~-124.5(8F), -128.5~130.0(4F)

[0295] [Example 14] The compound represented by the above formula (AN) was obtained by the method shown below. The same operation as in Example 1 was performed except that the compound represented by formula (7-14) was used instead of the compound represented by formula (7-1), to obtain 3.42 g of compound (AN) (Rf1 in formula (AN) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0296] The compound represented by formula (7-14) was synthesized by reacting 2,2,3,3-tetrafluoro-1,4-butanediol with twice the molar amount of 6-bromo-1-hexene, followed by oxidation with m-chloroperbenzoic acid (mCPBA).

[0297] The obtained compound (AN) 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-D6): δ[ppm]=1.65-1.85(12H), 3.40-3.85(34H), 3.85-4.10(12H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F), -130.0(4F)

[0298] [Example 15] The compound represented by the above formula (AO) was obtained by the method shown below. The same operation as in Example 1 was performed, except that the compound represented by formula (7-15) was used instead of the compound represented by formula (7-1), to obtain 2.89 g of compound (AO) (Rf1 in formula (AO) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which represents the average degree of polymerization, is 4.5, and i, which represents the average degree of polymerization, is 4.5).

[0299] The compound represented by formula (7-15) was synthesized by the addition reaction of epibromohydrin with twice the molar amount of 3-buten-1-ol, protecting the hydroxyl group generated by the addition reaction with dihydropyran, and then oxidizing it with m-chloroperbenzoic acid (mCPBA).

[0300] The obtained compound (AO) 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-D6): δ[ppm]=1.65-1.85(4H), 3.65-3.85(40H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0301] [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 performed, except that the compound represented by formula (7-16) was used instead of the compound represented by formula (7-1), to obtain 3.11 g of compound (AP) (Rf1 in formula (AP) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which represents the average degree of polymerization, is 4.5, and i, which represents the average degree of polymerization, is 4.5).

[0302] The compound represented by formula (7-16) was synthesized by reacting the compound obtained by oxidizing 8-bromo-1-octene with m-chloroperbenzoic acid (mCPBA) with twice the molar amount of 3-buten-1-ol, protecting the hydroxyl group generated by the reaction with dihydropyran, and further oxidizing it with m-chloroperbenzoic acid.

[0303] The obtained compound (AP) 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-D6): δ[ppm]=1.65-1.85(14H), 3.65-3.85(40H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0304] [Example 17] The compound represented by the above formula (AQ) was obtained by the method shown below. The same procedure as in Example 1 was performed, except that the compound represented by formula (7-17) was used instead of the compound represented by formula (7-1), to obtain 3.18 g of compound (AQ) (Rf1 in formula (AQ) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0305] The compound represented by formula (7-17) was synthesized by the addition reaction of epibromohydrin with twice the molar amount of 5-hexen-1-ol, protecting the hydroxyl group generated by the addition reaction with dihydropyran, and then oxidizing it with m-chloroperbenzoic acid (mCPBA).

[0306] The obtained compound (AQ) 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-D6): δ[ppm]=1.65-1.85(12H), 3.65-3.85(40H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0307] [Example 18] The compound represented by the above formula (AR) was obtained by the method shown below. The same operation as in Example 1 was performed except that the compound represented by formula (7-18) was used instead of the compound represented by formula (7-1), to obtain 2.95 g of compound (AR) (Rf1 in formula (AR) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which represents the average degree of polymerization, is 4.5, and i, which represents the average degree of polymerization, is 4.5).

[0308] The compound represented by formula (7-18) was synthesized by reacting epibromohydrin with an equimolar amount of 3-buten-1-ol, followed by oxidation with m-chloroperbenzoic acid (mCPBA).

[0309] The obtained compound (AR) 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-D6): δ[ppm]=1.65-1.85(2H), 3.65-3.85(34H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0310] [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 performed, except that the compound represented by formula (7-19) was used instead of the compound represented by formula (7-1), to obtain 3.08 g of compound (AS) (Rf1 in formula (AS) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which represents the average degree of polymerization, is 4.5, and i, which represents the average degree of polymerization, is 4.5).

[0311] The compound represented by formula (7-19) was synthesized by reacting epibromohydrin with an equimolar amount of 7-octen-1-ol, followed by oxidation with m-chloroperbenzoic acid (mCPBA).

[0312] The obtained compound (AS) 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-D6): δ[ppm]=1.65-1.85(10H), 3.65-3.85(34H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0313] [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 performed, except that the compound represented by formula (7-20) was used instead of the compound represented by formula (7-1), to obtain 3.02 g of compound (AT) (Rf1 in formula (AT) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which represents the average degree of polymerization, is 4.5, and i, which represents the average degree of polymerization, is 4.5).

[0314] The compound represented by formula (7-20) was synthesized by reacting 6-bromo-1-hexene with an equal molar amount of 5-hexen-1-ol, followed by oxidation with m-chloroperbenzoic acid (mCPBA).

[0315] The obtained compound (AT) 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-D6): δ[ppm]=1.65-1.85(12H), 3.65-3.85(34H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0316] [Example 21] The compound represented by the above formula (BA) was obtained by the method shown below. HOCH2CF2O(CF2CF2O) h (CF2O) i Instead of the compound represented by CF2CH2OH, HOCH2CF2CF2O(CF2CF2CF2O) j The same procedures as in Example 1 were performed except that a compound (number average molecular weight 1000, molecular weight distribution 1.1) represented by CF2CF2CH2OH (where j, representing the average degree of polymerization, is 4.5) was used, and 3.35 g of compound (BA) (Rf2 in formula (BA) is a PFPE chain represented by the above formula (4-2). In the two Rf2s, j, representing the average degree of polymerization, is 4.5) was obtained.

[0317] The resulting compound (BA) 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-D6): δ[ppm]=1.65-1.85(8H), 3.40-3.85(38H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(36F), -86.4(8F), -124.3(8F), -130.0~-129.0(18F)

[0318] [Example 22] The compound represented by the above formula (BB) was obtained by the method shown below. HOCH2CF2O(CF2CF2O) h (CF2O) i Instead of the compound represented by CF2CH2OH, HOCH2CF2CF2CF2O(CF2CF2CF2CF2O) kThe same procedures as in Example 1 were performed, except that a compound (number average molecular weight 1000, molecular weight distribution 1.1) represented by CF2CF2CF2CH2OH (where k, indicating the average degree of polymerization, is 3.0) was used, and 3.21 g of compound (BB) (Rf3 in formula (BB) is a PFPE chain represented by the above formula (4-3). In the two Rf3s, k, indicating the average degree of polymerization, is 3.0) was obtained.

[0319] The obtained compound (BB) 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-D6): δ[ppm]=1.65-1.85(8H), 3.40-3.85(38H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(32F), -122.5(8F), -126.0(24F), -129.0~-128.0(8F)

[0320] [Example 23] The compound represented by the above formula (BC) was obtained by the method shown below. The same operations as in Example 1 were performed except that the compound represented by formula (5-2) was used instead of the compound represented by formula (5-1), to obtain 3.39 g of compound (BC) (Rf1 in formula (BC) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0321] The compound represented by formula (5-2) was synthesized by protecting one hydroxyl group of 1,3-propanediol with dihydropyran, followed by the reaction with epibromohydrin.

[0322] The resulting compound (BC) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1H-NMR (acetone-D6): δ[ppm]=1.65-1.85(12H), 3.40-3.85(38H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0323] [Example 24] The compound represented by the above formula (BD) was obtained by the method shown below. The same operations as in Example 1 were performed except that the compound represented by formula (5-3) was used instead of the compound represented by formula (5-1), to obtain 3.12 g of compound (BD) (Rf1 in formula (BD) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0324] The compound represented by formula (5-3) was synthesized by protecting the hydroxyl group of 3-buten-1-ol with dihydropyran, followed by oxidation with m-chloroperbenzoic acid.

[0325] The obtained compound (BD) 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-D6): δ[ppm]=1.65-1.85(12H), 3.40-3.85(30H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0326] [Example 25] The compound represented by the above formula (BE) was obtained by the method shown below. The same operations as in Example 1 were performed, except that the compound represented by formula (5-4) was used instead of the compound represented by formula (5-1), to obtain 3.29 g of compound (BE) (Rf1 in formula (BE) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0327] The compound represented by formula (5-4) was synthesized by reacting 3-buten-1-ol with 2-(2-bromoethoxy)tetrahydro-2H-pyran, followed by oxidation with m-chloroperbenzoic acid.

[0328] The resulting compound (BE) 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-D6): δ[ppm]=1.65-1.85(12H), 3.40-3.85(38H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0329] [Example 26] The compound represented by the above formula (BF) was obtained by the method shown below. The same operation as in Example 1 was performed, except that the compound represented by formula (5-5) was used instead of the compound represented by formula (5-1), to obtain 3.54 g of compound (BF) (Rf1 in formula (BF) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which represents the average degree of polymerization, is 4.5, and i, which represents the average degree of polymerization, is 4.5).

[0330] The compound represented by formula (5-5) was synthesized by subjecting the compound represented by formula (5-1) to an addition reaction with allyl alcohol, protecting the hydroxyl group generated by the addition reaction with dihydropyran, and then oxidizing it with m-chloroperbenzoic acid.

[0331] The resulting compound (BF) 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-D6): δ[ppm]=1.65-1.85(8H), 3.40-3.85(50H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0332] [Example 27] The compound represented by the above formula (BG) was obtained by the method shown below. The same operations as in Example 1 were performed except that the compound represented by formula (5-6) was used instead of the compound represented by formula (5-1), to obtain 3.39 g of compound (BG) (Rf1 in formula (BG) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0333] The compound represented by formula (5-6) was synthesized by the addition reaction of the compound represented by formula (5-3) with allyl alcohol, protecting the hydroxyl group generated by the addition reaction with dihydropyran, and then oxidizing it with m-chloroperbenzoic acid.

[0334] The obtained compound (BG) 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-D6): δ[ppm]=1.65-1.85(12H), 3.40-3.85(42H), 3.85-4.10(8H) 19F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0335] [Example 28] The compound represented by the above formula (BH) was obtained by the method shown below. The same operation as in Example 1 was performed, except that the compound represented by formula (5-7) was used instead of the compound represented by formula (5-1), to obtain 3.52 g of compound (BH) (Rf1 in formula (BH) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0336] The compound represented by formula (5-7) was synthesized by subjecting the compound represented by formula (5-1) to an addition reaction with 3-buten-1-ol, protecting the hydroxyl group generated by the addition reaction with dihydropyran, and then oxidizing it with m-chloroperbenzoic acid.

[0337] The resulting compound (BH) 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-D6): δ[ppm]=1.65-1.85(12H), 3.40-3.85(50H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0338] [Example 29] The compound represented by the above formula (BI) was obtained by the method shown below. (First reaction) In the same manner as in the first reaction of Example 1, a compound represented by formula (11) was obtained as intermediate compound 1a.

[0339] (Second reaction) The same procedure as in the first reaction of Example 1 was carried out, except that the compound represented by formula (5-5) was used instead of the compound represented by formula (5-1), to obtain a compound represented by formula (12) as intermediate compound 1b.

[0340] [ka] (Rf1 in formula (12) is a PFPE chain represented by the above formula (4-1). In Rf1, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5. THP represents a tetrahydropyranyl group.)

[0341] (Third reaction) Next, 9.66 g of the compound represented by formula (11), which is the intermediate compound 1a obtained above, 0.69 g of the compound represented by formula (9-1), and 20 mL of t-butanol were charged into a 100 mL recovery flask under a nitrogen gas atmosphere, and the mixture was stirred at room temperature until it became homogeneous. 0.45 g of potassium tert-butoxide was added to the mixture, and the mixture was reacted by stirring at 70°C for 16 hours.

[0342] The compound represented by formula (9-1) was synthesized by reacting 1,4-dibromobutane with twice the molar amount of 3-buten-1-ol, followed by oxidation of one of the carbon-carbon double bonds with m-chloroperbenzoic acid (mCPBA).

[0343] The reaction mixture obtained above 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 over anhydrous sodium sulfate. After filtering off the desiccant, the filtrate was concentrated, and the residue was oxidized with m-chloroperbenzoic acid and then purified by silica gel column chromatography to obtain 7.32 g of the compound represented by the following formula (13) as intermediate compound 1-2.

[0344] [ka] (Rf1 in formula (13) is a PFPE chain represented by the above formula (4-1). In Rf1, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5. THP represents a tetrahydropyranyl group.)

[0345] (Fourth reaction) Next, 6.81 g of the compound represented by formula (12), which is intermediate compound 1b obtained above, 7.32 g of the compound represented by formula (13), which is intermediate compound 1-2 obtained above, and 20 mL of t-butanol were charged into a 100 mL recovery flask under a nitrogen gas atmosphere, and the mixture was stirred at room temperature until it became homogeneous. 0.45 g of potassium tert-butoxide was added to the mixture, and the mixture was reacted by stirring at 70°C for 16 hours.

[0346] After the reaction, the resulting reaction mixture was returned to room temperature, and 50 g of a 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. The reaction mixture was then transferred in small portions to a separatory funnel containing 100 mL of saturated aqueous sodium bicarbonate and extracted twice with 200 mL of ethyl acetate. The organic layer was washed sequentially with 100 mL of brine, 100 mL of saturated aqueous sodium bicarbonate, and 100 mL of brine, and then dehydrated using anhydrous sodium sulfate. After filtering off the desiccant, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 3.92 g of compound (BI). Rf1 in formula (BI) represents the PFPE chain represented by formula (4-1) above. For the two Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5.

[0347] The obtained compound (BI) 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-D6): δ[ppm]=1.65-1.85(8H), 3.40-3.85(44H), 3.85-4.10(8H) 19F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0348] [Example 30] The compound represented by the above formula (BJ) was obtained by the method shown below. The same procedure as in Example 1 was performed, except that the compound represented by formula (5-8) was used instead of the compound represented by formula (5-1), to obtain 3.53 g of compound (BJ) (Rf1 in formula (BJ) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0349] The compound represented by formula (5-8) was synthesized by protecting one of the hydroxyl groups of 1,6-hexanediol with dihydropyran, followed by the reaction with epibromohydrin.

[0350] The obtained compound (BJ) 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-D6): δ[ppm]=1.20-1.85(24H), 3.40-3.85(38H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0351] [Example 31] The compound represented by the above formula (BK) was obtained by the method shown below. The same operation as in Example 1 was performed, except that the compound represented by formula (5-9) was used instead of the compound represented by formula (5-1), to obtain 3.30 g of compound (BK) (Rf1 in formula (BK) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which represents the average degree of polymerization, is 4.5, and i, which represents the average degree of polymerization, is 4.5).

[0352] The compound represented by formula (5-9) was synthesized by protecting 7-octen-1-ol with dihydropyran, followed by oxidation with m-chloroperbenzoic acid.

[0353] The obtained compound (BK) 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-D6): δ[ppm]=1.20-1.85(24H), 3.40-3.85(30H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0354] [Example 32] The compound represented by the above formula (BL) was obtained by the method shown below. The same operation as in Example 1 was performed, except that the compound represented by formula (5-10) was used instead of the compound represented by formula (5-1), to obtain 2.95 g of compound (BL) (Rf1 in formula (BL) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0355] The compound represented by formula (5-10) was synthesized by reacting 2-(2-bromoethoxy)tetrahydro-2H-pyran with 5-hexen-1-ol, followed by oxidation with m-chloroperbenzoic acid.

[0356] The obtained compound (BL) 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-D6): δ[ppm]=1.20-1.85(20H), 3.40-3.85(38H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0357] [Example 33] The compound represented by the above formula (BM) was obtained by the method shown below. The same operations as in Example 1 were performed, except that the compound represented by formula (5-11) was used instead of the compound represented by formula (5-1), to obtain 3.01 g of compound (BM) (Rf1 in formula (BM) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0358] The compound represented by formula (5-11) was synthesized by protecting the hydroxyl group of allyl alcohol with dihydropyran, followed by oxidation with m-chloroperbenzoic acid.

[0359] The resulting compound (BM) 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-D6): δ[ppm]=1.65-1.85(8H), 3.40-3.85(30H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0360] [Example 34] The compound represented by the above formula (BN) was obtained by the method shown below. The same operation as in Example 1 was performed, except that the compound represented by formula (5-12) was used instead of the compound represented by formula (5-1), to obtain 3.08 g of compound (BN) (Rf1 in formula (BN) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which represents the average degree of polymerization, is 4.5, and i, which represents the average degree of polymerization, is 4.5).

[0361] The compound represented by formula (5-12) was synthesized by protecting the two hydroxyl groups of 1-allyloxy-2,3-propanediol with dihydropyran, followed by oxidation with m-chloroperbenzoic acid.

[0362] The resulting compound (BN) 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-D6): δ[ppm]=1.65-1.85(8H), 3.40-3.85(42H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0363] [Example 35] The compound represented by the above formula (BO) was obtained by the method shown below. The same operation as in Example 1 was performed, except that the compound represented by formula (5-13) was used instead of the compound represented by formula (5-1), to obtain 3.06 g of compound (BO) (Rf1 in formula (BO) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which represents the average degree of polymerization, is 4.5, and i, which represents the average degree of polymerization, is 4.5).

[0364] The compound represented by formula (5-13) was synthesized by the addition reaction of allyl alcohol with allyl glycidyl ether, protecting the hydroxyl group generated by the addition reaction with dihydropyran, and oxidizing one of the allyl groups with m-chloroperbenzoic acid.

[0365] The resulting compound (BO) 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-D6): δ[ppm]=1.65-1.85(8H), 3.40-3.85(44H), 3.85-4.10(8H), 5.40-6.10(6H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0366] [Example 36] The compound represented by the above formula (BP) was obtained by the method shown below. The same operation as in Example 1 was performed, except that the compound represented by formula (5-14) was used instead of the compound represented by formula (5-1), to obtain 3.28 g of compound (BP) (Rf1 in formula (BP) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0367] The compound represented by formula (5-14) was synthesized by reacting p-methoxyphenol with epibromohydrin.

[0368] The resulting compound (BP) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1H-NMR (acetone-D6): δ[ppm]=1.65-1.85(8H), 3.40-3.85(34H), 3.85-4.10(8H), 6.30-7.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0369] [Example 37] The compound represented by the above formula (BQ) was obtained by the method shown below. The same operation as in Example 1 was performed, except that the compound represented by formula (5-15) was used instead of the compound represented by formula (5-1), to obtain 3.15 g of compound (BQ) (Rf1 in formula (BQ) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0370] The compound represented by formula (5-15) was synthesized by reacting N-(2-hydroxyethyl)acetamide with epibromohydrin.

[0371] The obtained compound (BQ) 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-D6): δ[ppm]=1.65-1.85(8H), 1.90(6H), 3.40-3.85(36H), 3.85-4.10(8H), 6.30-6.50(2H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0372] [Example 38] The compound represented by the above formula (BR) was obtained by the method shown below. The same operation as in Example 1 was performed except that the compound represented by formula (5-16) was used instead of the compound represented by formula (5-1), to obtain 3.21 g of compound (BR) (Rf1 in formula (BR) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which represents the average degree of polymerization, is 4.5, and i, which represents the average degree of polymerization, is 4.5).

[0373] The compound represented by formula (5-16) was synthesized by reacting 2-cyanoethanol with epibromohydrin.

[0374] The resulting compound (BR) 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-D6): δ[ppm]=1.65-1.85(8H), 2.00-2.10(4H), 3.40-3.85(32H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0375] [Example 39] The compound represented by the above formula (CA) was obtained by the method shown below. The same operations as in Example 1 were performed, except that a compound represented by the following formula (14) was used instead of the compound represented by formula (7-1), to obtain 3.81 g of compound (CA) (Rf1 in formula (CA) is a PFPE chain represented by the above formula (4-1). In the three Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0376] [ka] (Rf1 in formula (14) is a PFPE chain represented by the above formula (4-1). In Rf1, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5.)

[0377] The compound represented by formula (14) is HOCH2CF2O(CF2CF2O) h (CF2O) i The compound (number average molecular weight: 1000, molecular weight distribution: 1.1) represented by CF2CH2OH (where h, representing the average degree of polymerization, is 4.5, and i, representing the average degree of polymerization, is 4.5) was reacted with the compound represented by formula (9-1), followed by oxidation with m-chloroperbenzoic acid to synthesize the compound.

[0378] The obtained compound (CA) 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-D6): δ[ppm]=1.65-1.85(16H), 3.40-3.85(54H), 3.85-4.10(12H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0379] [Example 40] The compound represented by the above formula (CB) was obtained by the method shown below. The same operation as in Example 39 was performed except that the compound represented by formula (9-2) was used instead of the compound represented by formula (9-1), to obtain 3.96 g of compound (CB) (Rf1 in formula (CB) is a PFPE chain represented by the above formula (4-1). In the three Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0380] The compound represented by formula (9-2) was synthesized by reacting 1,4-dibromobutane with twice the molar amount of 5-hexen-1-ol, followed by oxidation of one of the carbon-carbon double bonds with m-chloroperbenzoic acid (mCPBA).

[0381] The resulting compound (CB) 1H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.65-1.85(24H), 3.40-3.85(54H), 3.85-4.10(12H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0382] [Example 41] The compound represented by the above formula (CC) was obtained by the method shown below. The same operation as in Example 39 was performed except that the compound represented by formula (9-3) was used instead of the compound represented by formula (9-1), to obtain 3.64 g of compound (CC) (Rf1 in formula (CC) is a PFPE chain represented by the above formula (4-1). In the three Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0383] The compound represented by formula (9-3) was synthesized by reacting 1,2-dibromoethane with twice the molar amount of 3-buten-1-ol, followed by oxidation of one of the carbon-carbon double bonds with m-chloroperbenzoic acid (mCPBA).

[0384] The resulting compound (CC) 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-D6): δ[ppm]=1.65-1.85(8H), 3.40-3.85(54H), 3.85-4.10(12H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0385] [Example 42] The compound represented by the above formula (CD) was obtained by the method shown below. The same operation as in Example 39 was performed except that the compound represented by formula (9-5) was used instead of the compound represented by formula (9-1), to obtain 3.53 g of compound (CD) (Rf1 in formula (CD) is a PFPE chain represented by the above formula (4-1). In the three Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0386] The compound represented by formula (9-5) was synthesized by reacting 1,8-dibromooctane with twice the molar amount of 3-buten-1-ol, followed by oxidation of one of the carbon-carbon double bonds with m-chloroperbenzoic acid (mCPBA).

[0387] The resulting compound (CD) 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-D6): δ[ppm]=1.65-1.85(32H), 3.40-3.85(54H), 3.85-4.10(12H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0388] [Example 43] The compound represented by the above formula (CE) was obtained by the method shown below. The same operation as in Example 39 was performed except that the compound represented by formula (9-6) was used instead of the compound represented by formula (9-1), to obtain 3.67 g of compound (CE) (Rf1 in formula (CE) is a PFPE chain represented by the above formula (4-1). In the three Rf1s, h, which represents the average degree of polymerization, is 4.5, and i, which represents the average degree of polymerization, is 4.5).

[0389] The compound represented by formula (9-6) was synthesized by reacting 2,2-dimethyl-1,3-propanediol with twice the molar amount of 5-bromo-1-pentene, followed by oxidation of one of the carbon-carbon double bonds with m-chloroperbenzoic acid (mCPBA).

[0390] The obtained compound (CE) 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-D6): δ[ppm]=0.90(12H), 1.65-1.85(16H), 3.40-3.85(54H), 3.85-4.10(12H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0391] [Example 44] The compound represented by the above formula (CF) was obtained by the method shown below. The same operation as in Example 39 was performed except that the compound represented by formula (9-7) was used instead of the compound represented by formula (9-1), to obtain 3.85 g of compound (CF) (Rf1 in formula (CF) is a PFPE chain represented by the above formula (4-1). In the three Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0392] The compound represented by formula (9-7) was synthesized by reacting 2,3-butanediol with twice the molar amount of 5-bromo-1-pentene, followed by oxidation of one of the carbon-carbon double bonds with m-chloroperbenzoic acid (mCPBA).

[0393] The resulting compound (CF) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1H-NMR (acetone-D6): δ[ppm]=1.15-1.20(12H), 1.65-1.85(16H), 3.40-3.85(50H), 3.85-4.10(12H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0394] [Example 45] The compound represented by the above formula (CG) was obtained by the method shown below. The same operation as in Example 39 was performed except that the compound represented by formula (9-8) was used instead of the compound represented by formula (9-1), to obtain 4.03 g of compound (CG) (Rf1 in formula (CG) is a PFPE chain represented by the above formula (4-1). In the three Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0395] The compound represented by formula (9-8) was synthesized by brominating diethylene glycol with phosphorus tribromide (PBr3), reacting the compound with twice the molar amount of 3-buten-1-ol, and then oxidizing one of the carbon-carbon double bonds with m-chloroperbenzoic acid (mCPBA).

[0396] The obtained compound (CG) 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-D6): δ[ppm]=1.65-1.85(8H), 3.40-3.85(62H), 3.85-4.10(12H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0397] [Example 46] The compound represented by the above formula (CH) was obtained by the method shown below. The same operation as in Example 39 was performed except that the compound represented by formula (9-12) was used instead of the compound represented by formula (9-1), to obtain 4.24 g of compound (CH) (Rf1 in formula (CH) is a PFPE chain represented by the above formula (4-1). In the three Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0398] The compound represented by formula (9-12) was synthesized by reacting 2,2,3,3-tetrafluoro-1,4-butanediol with an equal molar amount of 1-bromo-4-pentene, followed by further reaction with an equal molar amount of 2-bromoethyloxirane.

[0399] The resulting compound (CH) 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-D6): δ[ppm]=1.65-1.85(12H), 3.40-3.85(46H), 3.85-4.10(20H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F), -130.0(8F)

[0400] [Example 47] The compound represented by the above formula (CI) was obtained by the method shown below. The same operation as in Example 39 was performed except that the compound represented by formula (9-15) was used instead of the compound represented by formula (9-1), to obtain 3.93 g of compound (CI) (Rf1 in formula (CI) is a PFPE chain represented by the above formula (4-1). In the three Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0401] The compound represented by formula (9-15) was synthesized by the addition reaction of epibromohydrin with twice the molar amount of 3-buten-1-ol, protecting the hydroxyl group generated by the addition reaction with dihydropyran, and then oxidizing one of the carbon-carbon double bonds with m-chloroperbenzoic acid (mCPBA).

[0402] The obtained compound (CI) 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-D6): δ[ppm]=1.65-1.85(8H), 3.40-3.85(58H), 3.85-4.10(12H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0403] [Example 48] The compound represented by the above formula (CJ) was obtained by the method shown below. The same operation as in Example 39 was performed except that the compound represented by formula (9-18) was used instead of the compound represented by formula (9-1), to obtain 3.93 g of compound (CJ) (Rf1 in formula (CJ) is a PFPE chain represented by the above formula (4-1). In the three Rf1s, h, which represents the average degree of polymerization, is 4.5, and i, which represents the average degree of polymerization, is 4.5).

[0404] The compound represented by formula (9-18) was synthesized by reacting 3-buten-1-ol with an equimolar amount of epibromohydrin.

[0405] The obtained compound (CJ) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1H-NMR (acetone-D6): δ[ppm]=1.65-1.85(4H), 3.40-3.85(46H), 3.85-4.10(12H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0406] [Example 49] The compound represented by the above formula (DA) was obtained by the method shown below. In the synthesis of the compound represented by formula (11) and the compound represented by formula (14), HOCH2CF2O(CF2CF2O) h (CF2O) i Instead of the compound represented by CF2CH2OH, HOCH2CF2CF2O(CF2CF2CF2O) j The same procedures as in Example 39 were performed except that a compound (number average molecular weight 1000, molecular weight distribution 1.1) represented by CF2CF2CH2OH (where j, indicating the average degree of polymerization, is 4.5) was used, and 3.86 g of compound (DA) (Rf2 in formula (DA) is a PFPE chain represented by the above formula (4-2). In the three Rf2s, j, indicating the average degree of polymerization, is 4.5) was obtained.

[0407] The obtained compound (DA) 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-D6): δ[ppm]=1.65-1.85(16H), 3.40-3.85(54H), 3.85-4.10(12H) 19 F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(54F), -86.4(12F), -124.3(12F), -130.0~-129.0(27F)

[0408] [Example 50] The compound represented by the above formula (DB) was obtained by the method shown below. The same procedure as in Example 39 was performed, except that the compound represented by formula (5-5) was used instead of the compound represented by formula (5-1), to obtain 4.01 g of compound (DB) (Rf1 in formula (DB) is a PFPE chain represented by the above formula (4-1). In the three Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0409] The obtained compound (DB) 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-D6): δ[ppm]=1.65-1.85(16H), 3.40-3.85(66H), 3.85-4.10(12H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0410] [Example 51] The compound represented by the above formula (DC) was obtained by the method shown below. The same operation as in Example 39 was performed except that the compound represented by formula (5-3) was used instead of the compound represented by formula (5-1), to obtain 3.64 g of compound (DC) (Rf1 in formula (DC) is a PFPE chain represented by the above formula (4-1). In the three Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0411] The obtained compound (DC) 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-D6): δ[ppm]=1.65-1.85(20H), 3.40-3.85(46H), 3.85-4.10(12H) 19F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0412] [Example 52] The compound represented by the above formula (DD) was obtained by the method shown below. The same operation as in Example 39 was performed except that the compound represented by formula (5-4) was used instead of the compound represented by formula (5-1), to obtain 3.87 g of compound (DD) (Rf1 in formula (DD) is a PFPE chain represented by the above formula (4-1). In the three Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0413] The obtained compound (DD) 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-D6): δ[ppm]=1.65-1.85(20H), 3.40-3.85(54H), 3.85-4.10(12H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0414] [Example 53] The compound represented by the above formula (DE) was obtained by the method shown below. The same operation as in Example 39 was performed except that the compound represented by formula (5-15) was used instead of the compound represented by formula (5-1), to obtain 3.95 g of compound (DE) (Rf1 in formula (DE) is a PFPE chain represented by the above formula (4-1). In the three Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0415] The resulting compound (DE) 1 H-NMR and 19F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.65-1.85(16H), 1.90(6H), 3.40-3.85(52H), 3.85-4.10(12H), 6.30-6.50(2H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0416] [Example 54] The compound represented by the above formula (DF) was obtained by the method shown below. The same operation as in Example 39 was performed except that the compound represented by formula (5-16) was used instead of the compound represented by formula (5-1), to obtain 3.72 g of compound (DF) (Rf1 in formula (DF) is a PFPE chain represented by the above formula (4-1). In the three Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0417] The obtained compound (DF) 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-D6): δ[ppm]=1.65-1.85(16H), 2.00-2.10(4H), 3.40-3.85(48H), 3.85-4.10(12H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0418] [Example 55] The compound represented by the above formula (DG) was obtained by the method shown below. The same procedure as in Example 39 was performed, except that the compound represented by formula (5-11) was used instead of the compound represented by formula (5-1), to obtain 3.51 g of compound (DG) (Rf1 in formula (DG) is a PFPE chain represented by the above formula (4-1). In the three Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0419] The resulting compound (DG) 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-D6): δ[ppm]=1.65-1.85(16H), 3.40-3.85(46H), 3.85-4.10(12H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0420] [Example 56] The compound represented by the above formula (EA) was obtained by the method shown below. The same procedure as in Example 1 was performed, except that the compound represented by formula (7-21) was used instead of the compound represented by formula (7-1), to obtain 2.82 g of compound (EA) (Rf1 in formula (EA) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which represents the average degree of polymerization, is 4.5, and i, which represents the average degree of polymerization, is 4.5).

[0421] [ka]

[0422] The compound represented by formula (7-21) was synthesized by reacting epibromohydrin with an equimolar amount of 5-hexen-1-ol, followed by oxidation with m-chloroperbenzoic acid (mCPBA).

[0423] The obtained compound (EA)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-D6): δ[ppm]=1.65-1.85(6H), 3.65-3.85(34H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0424] [Example 57] The compound represented by the above formula (EB) was obtained by the method shown below. The same operations as in Example 1 were performed, except that the compound represented by formula (7-21) was used instead of the compound represented by formula (7-1), and the compound represented by formula (5-11) was used instead of the compound represented by formula (5-1), to obtain 2.66 g of compound (EB) (Rf1 in formula (EB) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which represents the average degree of polymerization, is 4.5, and i, which represents the average degree of polymerization, is 4.5).

[0425] The obtained compound (EB) 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-D6): δ[ppm]=1.65-1.85(6H), 3.65-3.85(26H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0426] [Example 58] The compound represented by the above formula (EC) was obtained by the method shown below. The same operations as in Example 1 were performed, except that the compound represented by formula (7-1) was replaced with the compound represented by formula (7-15), and the compound represented by formula (5-11) was replaced with the compound represented by formula (5-1), to obtain 2.81 g of compound (EC) (Rf1 in formula (EC) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which represents the average degree of polymerization, is 4.5, and i, which represents the average degree of polymerization, is 4.5).

[0427] The obtained compound (EC) 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-D6): δ[ppm]=1.65-1.85(4H), 3.65-3.85(32H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0428] The thus obtained compounds (AA) to (AT), (BA) to (BR), (CA) to (CJ), (DA) to (DG), and (EA) to (EC) of Examples 1 to 58 were applied to the formula (1), and the value of x, R 1 , R 2 , R 3 , R 4 The structures are shown in Tables 1 to 3.

[0429] [Table 1]

[0430] [Table 2]

[0431] [Table 3]

[0432] [Comparative Example 1] The compound represented by the following formula (ZA) was synthesized by the method described in Patent Document 1.

[0433] [ka] (Rf1 in formula (ZA) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h representing the average degree of polymerization is 7.0, and i representing the average degree of polymerization is 0.)

[0434] Comparative Example 2 The compound represented by the following formula (ZB) was synthesized by the method described in Patent Document 2.

[0435] [ka] (Rf1 in formula (ZB) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5.)

[0436] Comparative Example 3 The compound represented by the following formula (ZC) was synthesized by the method described in Patent Document 3.

[0437] [ka] (Rf1 in formula (ZC) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5.)

[0438] Comparative Example 4 The compound represented by the following formula (ZD) was synthesized by the method described in Patent Document 4.

[0439] [ka] (Rf2 in formula (ZD) is a PFPE chain represented by the above formula (4-2). In the two Rf2s, j, which represents the average degree of polymerization, is 4.5.)

[0440] Comparative Example 5 The compound represented by the following formula (ZE) was synthesized by the method described in Patent Document 5.

[0441] [ka] (Rf1 in formula (ZE) is a PFPE chain represented by the above formula (4-1). In the three Rf1s, h representing the average degree of polymerization is 7.0, and i representing the average degree of polymerization is 0.)

[0442] Comparative Example 6 The compound represented by the following formula (ZF) was synthesized by the method described in Patent Document 6.

[0443] [ka] (Rf1 in formula (ZF) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5.)

[0444] Comparative Example 7 The compound represented by the following formula (ZG) was synthesized by the method described in Patent Document 7.

[0445] [ka] (Rf1 in formula (ZG) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5.)

[0446] [Comparative Example 8] The compound represented by the following formula (ZH) was synthesized by the method described in Patent Document 8.

[0447] [ka] (Rf1 in formula (ZH) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5.)

[0448] The number average molecular weights (Mn) of the compounds thus obtained in Examples 1 to 58 and Comparative Examples 1 to 8 were measured by the above-mentioned method. The results are shown in Tables 4 to 7.

[0449] Next, solutions for forming lubricating layers were prepared by the method described below using the compounds obtained in Examples 1 to 58 and Comparative Examples 1 to 8. Then, using the obtained solutions for forming lubricating layers, lubricating layers for magnetic recording media were formed by the method described below, thereby obtaining the magnetic recording media of Examples 1 to 58 and Comparative Examples 1 to 8.

[0450] "Lubricant layer forming solution" The compounds obtained in Examples 1 to 58 and Comparative Examples 1 to 8 were each dissolved in a fluorine-based solvent, Vertrel (registered trademark) XF (trade name, manufactured by Mitsui DuPont Fluorochemicals Co., Ltd.), and diluted with Vertrel XF so that the film thickness when applied to the protective layer would be 9.0 Å to 9.5 Å, to prepare a solution for forming a lubricating layer.

[0451] "Magnetic recording media" A magnetic recording medium was prepared by sequentially depositing an adhesive layer, a soft magnetic layer, a first underlayer, a second underlayer, a magnetic layer, and a protective layer on a substrate having a diameter of 65 mm. The protective layer was made of carbon. On the protective layer of a magnetic recording medium on which each layer up to the protective layer had been formed, the lubricating layer-forming solutions of Examples 1 to 58 and Comparative Examples 1 to 8 were applied by dipping under the conditions of an immersion speed of 10 mm / sec, an immersion time of 30 seconds, and a pull-up speed of 1.2 mm / sec. The magnetic recording medium coated with the lubricating layer-forming solution was then placed in a thermostatic chamber, and a heat treatment was performed at 120°C for 10 minutes to remove the solvent in 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.

[0452] (film thickness measurement) The thickness of the lubricating layer of each of the magnetic recording media thus obtained in Examples 1 to 58 and Comparative Examples 1 to 8 was measured using a Fourier transform infrared spectrophotometer (FT-IR, product name: Nicolet iS50, manufactured by Thermo Fisher Scientific). The results are shown in Tables 4 to 7.

[0453] Next, the following corrosion resistance test and spin-off characteristic test were carried out on the magnetic recording media of Examples 1 to 58 and Comparative Examples 1 to 8. The results are shown in Tables 4 to 7.

[0454] [Corrosion resistance test] The magnetic recording medium was exposed to conditions of a temperature of 85°C and a relative humidity of 90% for 48 hours. After that, the number of corrosion spots with a diameter of 5 μm or more that appeared on the surface of the magnetic recording medium was counted using an optical surface analyzer (Candela 7140, manufactured by KLA-Tencor Corporation) and evaluated based on the following criteria.

[0455] "Corrosion resistance evaluation criteria" A+: Fewer than 100 corrosion spots A: Number of corrosion spots: 100 or more, but less than 300 B: Number of corrosion spots: 300 or more, but less than 500 C: Number of corrosion spots: 500 or more but less than 1000 D: More than 1,000 corrosion spots

[0456] [Spin-off characteristic test] The magnetic recording medium was mounted on a spin stand and rotated at 10,000 rpm for 72 hours at 80°C. Before and after this operation, the thickness of the lubricating layer was measured using FT-IR at a position 20 mm radius from the center of the magnetic recording medium, and the reduction rate of the lubricating layer thickness before and after the test was calculated. The calculated reduction rate of the film thickness was used to evaluate the spin-off characteristics according to the following evaluation criteria.

[0457] "Evaluation criteria for spin-off characteristics" A+: Film thickness reduction rate less than 2% A: Film thickness reduction rate: 2% or more, less than 3% B: Film thickness reduction rate 3% or more, less than 5% C: Film thickness reduction rate 5% or more, less than 10% D: Film thickness reduction rate of 10% or more

[0458] [comprehensive evaluation] Based on the results of the corrosion resistance test and spin-off property test, a comprehensive evaluation was made based on the following criteria. "comprehensive evaluation" A: Both the corrosion resistance test and spin-off property test are A+ or A B: Either the corrosion resistance test rating or the spin-off characteristics test rating is B, and the other is A+, A, or B. C: Either the corrosion resistance test rating or the spin-off characteristics test rating is C, and the other is A+, A, B, or C. D: At least one of the evaluations of the corrosion resistance test and the spin-off characteristics test is D

[0459] [Table 4]

[0460] [Table 5]

[0461] [Table 6]

[0462] [Table 7]

[0463] As shown in Tables 4 to 6, the perfluoropolyether chain (R 2 ) between the R 3is a divalent linking group represented by any one of formulas (2-1) to (2-5), and the magnetic recording media of Examples 1 to 58, which used fluorine-containing ether compounds (AA) to (AT), (BA) to (BR), (CA) to (CJ), (DA) to (DG), and (EA) to (EC) satisfying formula (1), were all evaluated as A+, A, or B in the corrosion resistance test and spin-off property test, and the overall evaluation was A or B. This confirmed that the lubricating layers of the magnetic recording media of Examples 1 to 58 had good corrosion resistance and a high spin-off suppression effect.

[0464] Also, R 1 and R 4 is a terminal group represented by formula (3-1), p is 0, q is 0, r is 1, and R 2 Examples 1 to 20 and 39 to 48, which used compounds (AA) to (AT) and (CA) to (CJ), each of which is a perfluoropolyether chain represented by formula (4-1), were compared.

[0465] As a result, R 3 is a linking group represented by formula (2-1) or (2-3), and compounds (AA), (AB), (AD) to (AG), (AL) to (AN), (CA), (CB), (CD) to (CF), and (CH) in formula (2) each having 3 or more carbon atoms were used in Examples 1, 2, 4 to 7, 12 to 14, 39, 40, 42 to 44, and 46, which were evaluated as A+ in the corrosion resistance test and were good. Also, R 3 In Examples 8 to 11, 15 to 17, 45, and 47, which used compounds (AH) to (AK), (AO) to (AQ), (CG), and (CI), in which is a linking group represented by formula (2-2) or formula (2-4), the spin-off property test was evaluated as A+, which showed good results.

[0466] Also, R 3 The compounds (AR) to (AT) in which R is a linking group represented by formula (2-5) were used in Examples 18 to 20, and a comparison was made. 3 In Example 18, which used the compound (AR) with the fewest carbon atoms contained in R, the spin-off resistance test was evaluated as A+, showing good results.3 In Example 20, which used the compound (AT) with the largest number of carbon atoms, the corrosion resistance test was evaluated as A+, showing good results.

[0467] In contrast, as shown in Table 7, in Comparative Examples 1 to 8, which used compounds (ZA) to (ZH), all of the corrosion resistance tests and spin-off property tests were evaluated as either B, C, or D, and the overall evaluation was either C or D.

[0468] More specifically, the linking group between the perfluoropolyether chains contains only one hydroxyl group in the compound (ZA) used in Comparative Example 1 and the compound (ZB) used in Comparative Example 2. This is thought to be why sufficient interaction between the linking group between the perfluoropolyether chains and the protective layer is not achieved, causing the center part of the fluorine-containing ether compound to float up, making the fluorine-containing ether compound in the lubricating layer more likely to scatter, and resulting in a result of D in the spin-off property test.

[0469] In the compound (ZC) used in Comparative Example 3 and the compound (ZD) used in Comparative Example 4, the two hydroxyl groups contained in the linking group between the perfluoropolyether chains are bonded only via a rigid alkylene chain. This prevents the free movement of the hydroxyl groups contained in the linking group, making it difficult for the hydroxyl groups to participate in interactions with active sites on the protective layer or polar groups in other fluorine-containing ether compounds present in the lubricating layer, which is thought to be why the spin-off property test was evaluated as D.

[0470] In addition, in the compound (ZE) used in Comparative Example 5, the perfluoropolyether chains are connected by a flexible linking group having two hydroxyl groups. However, because the distance between the two hydroxyl groups of the linking group is short, the two hydroxyl groups of the linking group tend to interact with each other within the molecule. For this reason, the two hydroxyl groups of the linking group are less likely to be involved in interactions with polar groups contained in other fluorine-containing ether compound molecules present in the lubricating layer, making it easier for water, which causes corrosion, to be absorbed near the linking group, which is thought to be why the corrosion resistance test was rated D.

[0471] Furthermore, compound (ZF) used in Comparative Example 6 and compound (ZG) used in Comparative Example 7 have two or three hydroxyl groups in the linking group between the perfluoropolyether chains. However, in compounds (ZF) and (ZG), the linking group between the perfluoropolyether chains contains a rigid ring structure, which restricts the movement of the hydroxyl groups contained in the linking group. For this reason, it is believed that sufficient interaction between the hydroxyl groups contained in the linking group and the protective layer was not achieved, resulting in the results of C in the corrosion resistance test and spin-off property test.

[0472] In addition, in the compound (ZH) used in Comparative Example 8, the perfluoropolyether chains are bonded by a linking group having two hydroxyl groups, and a partially fluorinated saturated hydrocarbon group is located between the two hydroxyl groups. In Comparative Example 8, a partially fluorinated saturated hydrocarbon group is located between the two hydroxyl groups contained in the linking group between the perfluoropolyether chains, and therefore the evaluations in the corrosion resistance test and spin-off property test were higher than in Comparative Example 5, which used compound (ZE). However, in the compound (ZH) used in Comparative Example 8, both a1 and a2 in formula (2) are 0, so the hydrophobicity of the linking group between the perfluoropolyether chains is insufficient, which is thought to be why the result of the corrosion resistance test was C. [Industrial Applicability]

[0473] By using a lubricant for magnetic recording media containing the fluorine-containing ether compound of the present invention, it is possible to form a lubricating layer that has good corrosion resistance and a high spin-off suppressing effect even if it is thin. [Explanation of symbols]

[0474] 10 Magnetic recording media 11 Circuit Board 12 Adhesion layer 13 Soft magnetic layer 14 1st base layer 15 Second base layer 16 Magnetic layer 17 Protective layer 18 Lubricating layer

Claims

1. A fluorine-containing ether compound represented by the following formula (1) and having a number average molecular weight in the range of 500 to 10,000: 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 1 or 2. R ２ is a perfluoropolyether chain. (x+1) R ２ R are each independently a perfluoropolyether chain represented by the following formula (4): ３ is a divalent linking group represented by any one of the following formulas (2-1) to (2-5): ３ may be the same or different from each other. １ and R ４ is a terminal group having 1 to 4 polar groups and 1 to 50 carbon atoms. １ and R ４ may be the same or different. The polar group possessed by R 1 and R 4 is at least one selected from the group consisting of a hydroxyl group, a cyano group, and a group having an amide bond. 【Chemistry 1】 (In formula (2-1), a11 and a12 represent integers of 0 to 5. a11 and a12 may be the same or different. The total value of a11 and a12 is 1 to 6. c represents an integer of 2 to 8. c R a and R b each independently represent a hydrogen atom or a methyl group. The total number of carbon atoms contained in the c (-CR a R b -)s is 2 to 8. The oxygen atom at the left terminal of formula (2-1) is bonded to the methylene group on the R 1 side in formula (1), and the oxygen atom at the right terminal is bonded to the methylene group on the R 4 side in formula (1).) (In formula (2-2), a21 and a22 represent integers of 0 to 5. a21 and a22 may be the same or different. The total value of a21 and a22 is 1 to 6. d represents an integer of 2 to 4. d R c s each independently represent —CH 2 CH 2 —, —CH 2 CH 2 CH 2 —, —CH(CH 3 )CH 2 —, or —CH 2 CH(CH 3 )—. The total number of carbon atoms contained in the d R c s is 4 to 8. The oxygen atom at the left terminal of formula (2-2) is bonded to the methylene group on the R 1 side in formula (1), and the oxygen atom at the right terminal is bonded to the methylene group on the R 4 side in formula (1).) (In formula (2-3), a31 and a32 represent integers of 0 to 5. a31 and a32 may be the same or different. The total value of a31 and a32 is 1 to 6. e represents an integer of 1 to 6. The oxygen atom at the left end of formula (2-3) is bonded to the methylene group on the R 1 side in formula (1), and the oxygen atom at the right end is bonded to the methylene group on the R 4 side in formula (1).) (In formula (2-4), a41 and a42 represent integers of 1 to 5. a41 and a42 may be the same or different. The total value of a41 and a42 is 2 to 6. f1 and f2 represent integers of 1 to 6. f1 and f2 may be the same or different, and the total value of f1 and f2 is 2 to 7. The oxygen atom at the left end of formula (2-4) is bonded to the methylene group on the R 1 side in formula (1), and the oxygen atom at the right end is bonded to the methylene group on the R 4 side in formula (1).) (In formula (2-5), a51 and a52 represent integers of 0 to 5. a51 and a52 may be the same or different. The total value of a51 and a52 is 1 to 6. The oxygen atom at the left end of formula (2-5) is bonded to the methylene group on the R 1 side in formula (1), and the oxygen atom at the right end is bonded to the methylene group on the R 4 side in formula (1).) -(CF 2 ) w1 -O-(CF 2 O) w2 -(CF 2 CF 2 O) w3 - (CF 2 CF 2 CF 2 O) w4 - (CF 2 CF 2 CF 2 CF 2 O) w5 - (CF 2 ) w6 - (4) (In formula (4), w2, w3, w4, and w5 represent average degrees of polymerization and each independently represents 0 to 20. However, w2, w3, w4, and w5 cannot all be 0 at the same time. w1 and w6 represent average values ​​representing the number of CF 2 s and each independently represents 1 to 3. There are no particular restrictions on the arrangement order of the repeating units (CF 2 O), (CF 2 CF 2 O), (CF 2 CF 2 CF 2 O), and (CF 2 CF 2 CF 2 CF 2 O) in formula (4).)

2. R in the formula (1) １ and R ４ and each independently represent a terminal group represented by the following formula (3): 【Chemistry 2】 (In formula (3), l represents an integer of 1 to 3. l m's each independently represent an integer of 1 to 6. l n's each independently represent an integer of 1 to 6. In one repeating unit, at least one of m and n is 1. A represents an alkyl group which may have a polar group, an organic group containing a carbon-carbon unsaturated bond which may have a polar group, or a hydrogen atom.)

3. R in the formula (1) １ and R ４ are each independently a terminal group represented by the following formula (3-1) or (3-2): 【Transformation 3】 (In formula (3-1), p represents an integer of 0 to 3, q ​​represents an integer of 0 to 2, and r represents an integer of 1 to 5. The total value of p and r is 1 to 5. B represents a polar group.) (In formula (3-2), s represents an integer of 0 to 2, and t represents an integer of 1 to 5.)

4. R in the formula (1) １ and R ４ The fluorine-containing ether compound according to claim 1 or 2, wherein

5. R in the formula (1) １ and a polar group having R ４ 3. The fluorine-containing ether compound according to claim 1, wherein the total number of polar groups contained in the compound is 2 to 6.

6. R in the formula (1) １ and a polar group having R ３ and a polar group having R ４ 3. The fluorine-containing ether compound according to claim 1, wherein all of the polar groups of the formula (I) are hydroxyl groups.

7. (x+1) R in the formula (1) ２ are each independently any one selected from perfluoropolyether chains represented by the following formulas (4-1) to (4-4): -CF ２ -(OCF ２ CF ２ ) ｈ -(OCF ２ ) ｉ -OCF ２ - (4-1) (In formula (4-1), 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 ２ CF ２ - (4-2) (In formula (4-2), j represents the average degree of polymerization and represents 1 to 15.) -CF ２ CF ２ CF ２ -(OCF ２ CF ２ CF ２ CF ２ ) ｋ -OCF ２ CF ２ CF ２ - (4-3) (In formula (4-3), k represents the average degree of polymerization and represents 1 to 10.) -(CF ２ ) ｗ７ -O-(CF ２ CF ２ CF ２ O) ｗ８ -(CF ２ CF ２ O) ｗ９ -(CF ２ ) ｗ１０ - (4-4) (In formula (4-4), w8 and w9 represent the average degree of polymerization, each independently representing 1 to 20. w7 and w10 represent CF ２ is an average value representing the number of

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

9. A magnetic recording medium having at least a magnetic layer, a protective layer, and a lubricating layer sequentially provided on a substrate, 3. A magnetic recording medium, wherein the lubricating layer comprises the fluorine-containing ether compound according to claim 1.

10. 10. The magnetic recording medium according to claim 9, wherein the lubricating layer has an average film thickness of 0.5 nm to 2.0 nm.

Images