Fluorinated ether compound, lubricant for magnetic recording medium, and magnetic recording medium

Abstract

Provided is a fluorinated ether compound represented by the following formula: R1-CH2-R2[-CH2-R3-CH2-R2]x-CH2-R4 (wherein x is 0-2, R2 is a perfluoropolyether chain, R3 is a divalent linking group having 1-4 polar groups, R1 and R4 are each a terminal group having 1-4 polar groups and 1-50 carbon atoms, and R1 and / or R4 is formula (2) (where a is 0-2, b is 1-6, and A is a hydrogen atom or an organic group having 1-30 carbon atoms and optionally containing at least one selected from among a polar group, a halogeno group, and an etheric oxygen atom)).

Description

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

[0001] The present invention relates to a fluorine-containing ether compound, a lubricant for a magnetic recording medium, and a magnetic recording medium. This application claims priority to Japanese Patent Application No. 2023-200893, filed on November 28, 2023, the contents of which are incorporated herein by reference.

[0002] In order to improve the recording density of magnetic recording and reproducing devices, development of magnetic recording media suitable for high recording densities is progressing. 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 ensure sufficient durability of the magnetic recording medium. For this reason, a lubricant is generally applied to the surface of the protective layer to form a lubricating layer.

[0003] Examples of lubricants used in forming the lubricating layer of a magnetic recording medium include -CF ２ It has been proposed to use a fluorine-based polymer having a repeating structure containing -, which contains a compound having a polar group such as a hydroxyl group or an amino group at the end thereof.

[0004] For example, Patent Documents 1 and 2 disclose a method for producing a perfluoropolyether having methylene groups (-CH) at both ends of the perfluoropolyether chain. ２ A glycerin structure (—O—CH ２ -CH(OH)-CH ２ The document discloses a fluorine-containing ether compound in which a terminal group, which is an organic group having a polar group, is bonded in this order.

[0005] Patent Document 3 describes a method for producing a perfluoropolyether polymer having an ether bond (—O—) and a methylene group (—CH ) between a perfluoropolyether chain and both terminal groups. ２ The present invention discloses a fluorine-containing ether compound having a linking group having a structure combining a methylene group (-CH(OH)-) in which one hydrogen atom is substituted with a hydroxyl group (-CH(OH)-).

[0006] Patent Document 4 describes a glycerin structure (—O—CH ２-CH(OH)-CH ２ -O-) at both ends ２ Disclosed is a fluorine-containing ether compound having a skeleton in which two perfluoropolyether chains are linked via a divalent linking group to which a hydroxyl group (-) is bonded, and in which terminal groups having polar groups are linked to both ends of the skeleton via methylene groups.

[0007] International Publication No. 2021 / 090940 (A) Japanese Patent No. 6804893 (B) International Publication No. 2019 / 054148 (A) U.S. Patent No. 10,540,997 (B)

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

[0009] However, reducing the thickness of the lubricating layer generally tends to reduce the chemical resistance of the magnetic recording medium. Furthermore, reducing the thickness of the lubricating layer can cause spin-off, which can prevent the lubricating layer from maintaining a sufficient thickness to fulfill its function. Spin-off is a phenomenon in which the lubricant scatters or evaporates due to centrifugal force and heat generated by the rotation of the magnetic recording medium. For these reasons, there has been a demand for a lubricating layer that has excellent chemical resistance and can suppress spin-off even when the lubricating layer is thin.

[0010] The present invention has been made in view of the above circumstances, and aims to provide a fluorine-containing ether compound that can form a lubricating layer that has excellent chemical resistance and can suppress spin-off, and can be suitably used as a material for a lubricant for a magnetic recording medium. Another object of the present invention is to provide a lubricant for a magnetic recording medium that contains the fluorine-containing ether compound of the present invention and can form a lubricating layer that has good chemical resistance and can suppress spin-off. Another object of the present invention is to provide a magnetic recording medium that has a lubricating layer that contains the fluorine-containing ether compound of the present invention, has good chemical resistance, and suppresses spin-off.

[0011] The present invention includes the following aspects.

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

[0013] (In formula (2), a represents an integer of 0 to 2, and b represents an integer of 1 to 6. A represents an organic group having 1 to 30 carbon atoms which may contain at least one of a polar group, a halogeno group, and an ether oxygen atom, or a hydrogen atom. However, the total number of polar groups contained in formula (2) is 2 to 4. When a is 2, the two b's may be the same or different.)

[0014] [2] The fluorine-containing ether compound according to [1], wherein the terminal group represented by the formula (2) is any one of the following formulae (2-1) to (2-6):

[0015] (In formula (2-1), c represents an integer of 1 to 6. X represents a hydroxyl group, an acetamide group, a carboxamide group, or a cyano group.) (In formula (2-2), a1 represents 0 or 1. b1 represents an integer of 1 to 6. d represents an integer of 1 to 4.) (In formula (2-3), a2 represents 0 or 1. b2 represents an integer of 1 to 6. e represents an integer of 0 to 7.) (In formula (2-4), a3 represents 0 or 1. b3 represents an integer of 1 to 6. f represents an integer of 0 to 6.) (In formula (2-6), f2 represents an integer of 1 to 6.)

[0016] [3] R in the formula (1) １ and R ４ [4] The fluorine-containing ether compound according to [1] or [2], wherein R in formula (1) is a terminal group represented by the formula (2). １ and R ４ The fluorine-containing ether compound according to [3], wherein

[0017] [5] R in the formula (1) １ and R ４ The fluorine-containing ether compound according to [1] or [2], wherein only one of the following is an end group represented by formula (2), and the other is an end group represented by formula (3):

[0018] (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. B represents an alkyl group which may have only one polar group, an organic group containing a carbon-carbon unsaturated bond which may have only one polar group, or a hydrogen atom.)

[0019] [6] R in the formula (1) １ and R ４ and the other is an end group represented by any one of the following formulas (3-1) to (3-3):

[0020] (In formula (3-1), p represents 0 or 1. q1, q2, q3, and q4 each independently represent an integer of 1 to 6. When p is 0, the total value of q1 and q4 is 2 to 10. When p is 1, the total value of q1, q2, q3, and q4 is 4 to 10. When p is 1, at least one of q2 and q3 is 1. D represents a polar group, a vinyl group, an ethynyl group, or an aryl group which may have a substituent. However, when D is the aryl group which may have a substituent, the number of polar groups contained in D is 0 or 1.) (In formula (3-2), r represents 0 or 1. s1, s2, and s3 each independently represent an integer of 1 to 6. When r is 1, the total value of s1, s2, and s3 is 3 to 8. When r is 1, at least one of s2 and s3 is 1.) (In formula (3-3), t represents 1 or 2. Each of the five E's independently represents a polar group, an alkoxy group having 1 to 8 carbon atoms, a halogeno group, or a hydrogen atom. However, when the five E's include a polar group, the total number of polar groups among the five E's is 1.)

[0021] [7] R in the formula (1) １ and R ４ The fluorine-containing ether compound according to [1] or [2], wherein only one of the following is an end group represented by formula (2), and the other is an end group represented by the following formula (3-4) or (3-5):

[0022] (In formula (3-4), g1 represents an integer of 1 to 6. g1 R ａ and R ｂ each independently represents a hydrogen atom or a methyl group.) (In formula (3-5), g2 represents an integer of 1 to 6.)

[0023] [8] In the formula (1), x is 1 or 2, and x R ３ are each independently a divalent linking group having 3 to 50 carbon atoms, having 1 to 3 hydroxyl groups and oxygen atoms at both ends bonding to adjacent methylene groups.

[0024] [9] In the formula (1), x is 1 or 2, and x R ３are each independently any one selected from linking groups represented by the following formulas (4-1) to (4-6):

[0025] (In formula (4-1), u1 represents an integer of 0 to 6, and u2 represents an integer of 0 to 6, provided that at least one of u1 and u2 is 0. The oxygen atom at the left end of formula (4-1) is R １ The oxygen atom at the right end is bonded to the methylene group at the side of the ４ (In formula (4-2), v represents an integer of 1 to 2. The oxygen atom at the left end of formula (4-2) is bonded to the methylene group on the R １ The oxygen atom at the right end is bonded to the methylene group at the side of the ４ (In formula (4-3), w represents an integer of 0 to 6. The oxygen atom at the left end of formula (4-3) is bonded to the methylene group on the R １ The oxygen atom at the right end is bonded to the methylene group at the side of the ４ (In formula (4-4), x1 represents an integer of 0 to 5, and x2 represents an integer of 0 to 5, provided that at least one of x1 and x2 is an integer of 1 to 5. The oxygen atom at the left end of formula (4-4) is bonded to the methylene group of R in formula (1). １ The oxygen atom at the right end is bonded to the methylene group at the side of the ４ (In formula (4-5), y1 represents an integer of 1 to 5, and y2 represents an integer of 1 to 5. The oxygen atom at the left end of formula (4-5) is bonded to the methylene group at the R １ The oxygen atom at the right end is bonded to the methylene group at the side of the ４ In formula (4-6), z represents an integer of 1 to 6. ｃ and R ｄ each independently represents a hydrogen atom, a fluorine atom, or a methyl group. The oxygen atom at the left terminal of formula (4-6) is R １ The oxygen atom at the right end is bonded to the methylene group at the side of the ４ It bonds to the methylene group on the side.)

[0026]

[10] (x+1) R in the formula (1) ２ are each independently a perfluoropolyether chain represented by the following formula (5): -(CF ２ ) ｗ１ -O-(CF ２ O) ｗ２ -(CF ２ CF ２ O) ｗ３ -(CF ２ CF ２ CF ２ O) ｗ４ -(CF ２ CF ２ CF ２ CF ２ O) ｗ５ -(CF ２ ) ｗ６ - (5) (In formula (5), w2, w3, w4, and w5 represent the average degree of polymerization, and each independently represents 0 to 20. However, w2, w3, w4, and w5 cannot all be 0 at the same time. w1 and w6 are CF ２ is an average value representing the number of repeating units in formula (5), each of which independently represents 1 to 3. ２ O), (CF ２ CF ２ O), (CF ２ CF ２ CF ２ O), (CF ２ CF ２ CF ２ CF ２ There are no particular restrictions on the arrangement order of O).

[0027]

[11] (x+1) R in the formula (1) ２ are each independently any one selected from perfluoropolyether chains represented by the following formulas (5-1) to (5-4): ２ -(OCF ２ CF ２ ) ｈ -(OCF ２ ) ｉ -OCF ２- (5-1) (In formula (5-1), h and i represent the average degree of polymerization, 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 - (5-2) (In formula (5-2), 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 - (5-3) (In formula (5-3), 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 - (5-4) (In formula (5-4), 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

[0028]

[12] The fluorine-containing ether compound according to [1], wherein the fluorine-containing ether compound represented by formula (1) is any one of the following formulae (AA), (AB), (AI), (AJ), (AN) to (AQ), (AS), (AW), (BA) to (BM), (CA) and (DA). (Rf in formula (AA) １ In the formula (AB), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. ２ In the formula (AI), j represents the average degree of polymerization, and represents 1 to 15. １In the formula (AJ), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. ２ In the formula (AN), j represents the average degree of polymerization, and represents 1 to 15. １ In the formula, h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. (Rf in formula (AO) ２ In the formula (AP), j represents the average degree of polymerization, and represents 1 to 15. １ In the formula (AQ), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. ２ In the formula (AS), j represents the average degree of polymerization, which is 1 to 15. ２ In the formula (AW), j represents the average degree of polymerization, and represents 1 to 15. ２ In the formula, j represents the average degree of polymerization and is a number ranging from 1 to 15. (Rf in formula (BA) １ In the formula (BB), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. ２ In the formula (BC), j represents the average degree of polymerization, and represents 1 to 15. ２ In the formula (BD), j represents the average degree of polymerization, which is 1 to 15. ２ In the formula (BE), j represents the average degree of polymerization, and represents 1 to 15. １ In the formula (BF), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. ２ In the formula, j represents the average degree of polymerization and is a number ranging from 1 to 15. (Rf in formula (BG) ２ In the formula (BH), j represents the average degree of polymerization, and represents 1 to 15. ２ In the formula (BI), j represents the average degree of polymerization, and represents 1 to 15. ２ In the formula (BJ), j represents the average degree of polymerization, and represents 1 to 15. ２ In the formula (BK), j represents the average degree of polymerization, which is 1 to 15. ２In the formula (BL), j represents the average degree of polymerization, which is 1 to 15. ２ In the formula (BM), j represents the average degree of polymerization, and represents 1 to 15. ２ In the formula, j represents the average degree of polymerization and is a number ranging from 1 to 15. (Two Rf in formula (CA) １ In the formula, h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. １ In the formula (DA), h and i may be the same or different. ２ In the formula, j represents the average degree of polymerization and is a number ranging from 1 to 15.

[0029]

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

[12] , which has a number average molecular weight in the range of 500 to 10,000.

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

[13] .

[0030]

[15] A magnetic recording medium comprising a substrate on which at least a magnetic layer, a protective layer, and a lubricating layer are sequentially formed, wherein the lubricating layer contains the fluorine-containing ether compound according to any one of [1] to

[13] .

[16] The magnetic recording medium according to

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

[0031] The fluorine-containing ether compound of the present invention is a compound represented by the above formula (1), and is therefore suitable as a material for a lubricant for a magnetic recording medium. Because the lubricant for a magnetic recording medium of the present invention contains the fluorine-containing ether compound of the present invention, it is possible to form a lubricating layer that has good chemical resistance and can suppress spin-off.

[0032] The magnetic recording medium of the present invention has a lubricating layer containing the fluorine-containing ether compound of the present invention.Therefore, the magnetic recording medium of the present invention has good chemical resistance, can suppress spin-off, and is excellent in reliability and durability.In addition, since the magnetic recording medium of the present invention has a lubricating layer that has good chemical resistance and can suppress spin-off, the thickness of the lubricating layer can be made thinner, which can contribute to reducing magnetic spacing and further reduce the flying height of the magnetic head.

[0033] 1 is a schematic cross-sectional view showing an embodiment of a magnetic recording medium of the present invention.

[0034] The present inventors have conducted extensive research to solve the above problems, as described below. Conventionally, fluorine-containing ether compounds having a terminal group containing a polar group such as a hydroxyl group have been preferably used as materials for lubricants for magnetic recording media (hereinafter sometimes abbreviated as "lubricants") that are applied to the surface of protective layers.

[0035] However, when a thin lubricating layer is formed on a protective layer using a conventional fluorine-containing ether compound having a terminal group containing a polar group, it is difficult to realize a lubricating layer that has good chemical resistance and can suppress spin-off, as shown below. That is, the polar group in the fluorine-containing ether compound bonds with the active site on the protective layer, improving the adhesion of the lubricating layer to the protective layer. If the adhesion of the lubricating layer to the protective layer is insufficient, the lubricating layer will not cover the protective layer properly, chemical contaminants will be easily incorporated into the protective layer, and sufficient chemical resistance will not be obtained.

[0036] In addition, the polar groups in the fluorine-containing ether compound not only bond with the active sites on the protective layer and participate in the interaction with the protective layer, but also participate in intramolecular and intermolecular interactions. If the polar groups participating in the intermolecular interactions between fluorine-containing ether compounds are insufficient, the fluorine-containing ether compound in the lubricating layer will easily scatter as the magnetic recording medium rotates, making spin-off more likely to occur.

[0037] Therefore, the fluorine-containing ether compound must contain a sufficient number of polar groups that interact with the protective layer and that interact with molecules in order to form a lubricating layer that has good chemical resistance and is spin-off-suppressed. However, if the number of polar groups in the fluorine-containing ether compound is increased, the polar groups will be more likely to induce chemical contaminants, making it impossible to obtain sufficient chemical resistance.

[0038] Therefore, the present inventors have conducted extensive research focusing on the strength of polar groups contained in fluorinated ether compounds and the interaction of polar groups. As a result, they have found that in fluorinated ether compounds containing a specific number of polar groups, at least some of the polar groups are erythritol structures (—O—CH ) located at one or both ends of a skeleton containing a perfluoropolyether chain. ２ -CH(OH)-CH(OH)-CH ２ In this case, as shown below, it is possible to ensure the number of hydroxyl groups that can interact with the protective layer and the number of hydroxyl groups that can participate in intermolecular interactions while suppressing an increase in surface free energy due to the hydroxyl groups contained in the erythritol structure.

[0039] That is, the erythritol structure (—O—CH ２ -CH(OH)-CH(OH)-CH ２ The internal 1,2-diol structure (—CH ２ -CH(OH)-CH(OH)-CH ２ -), carbon atoms bonded to hydroxyl groups are bonded to each other. Therefore, the distance between the hydroxyl groups is short, and steric and electrostatic repulsion between the hydroxyl groups is likely to occur. Furthermore, in the erythritol structure, the carbon atom bonded to a hydroxyl group is bonded to the carbon atom bonded to a hydroxyl group, and therefore free rotation is likely to be suppressed. For these reasons, the two hydroxyl groups contained in the erythritol structure are in an opposite conformation with respect to the carbon chain in the erythritol structure. As a result, the dipole moments generated by the two hydroxyl groups contained in the erythritol structure cancel each other out, and the surface free energy of the entire fluorine-containing ether compound molecule is reduced.

[0040] Furthermore, the distance between active sites on the protective layer is sufficiently greater than the distance between hydroxyl groups contained in the erythritol structure. Moreover, as described above, the two hydroxyl groups contained in the erythritol structure are in opposite conformations with respect to the carbon chain in the erythritol structure. Therefore, the two hydroxyl groups contained in the erythritol structure are not simultaneously in a direction approaching the protective layer. Therefore, of the two hydroxyl groups, only one hydroxyl group can interact with the active site on the protective layer, and the other hydroxyl group can participate in intermolecular interactions between fluorine-containing ether compounds.

[0041] In the past, the structures of fluorine-containing ether compounds used in lubricants have been designed so that as many polar groups as possible in the compound are positioned so as to facilitate interaction with active sites on the protective layer in order to improve adhesion to the protective layer. For this reason, structures such as erythritol, in which carbon atoms to which hydroxyl groups are bonded are bonded, resulting in adjacent hydroxyl groups being oriented in opposite directions on the protective layer, have tended to be avoided.

[0042] However, the present inventors deliberately changed some of the polar groups in the fluorinated ether compound to hydroxyl groups of an erythritol structure, thereby ensuring the number of polar groups that can participate in intermolecular interactions between fluorinated ether compounds, and then considered that the number of polar groups that can interact with active sites on the protective layer could be adjusted as necessary within a range that could suppress an increase in surface free energy caused by an excessive number of polar groups.

[0043] Furthermore, the present inventors have conducted extensive research into a fluorine-containing ether compound having an end group containing an erythritol structure at at least one end of a skeleton containing a perfluoropolyether chain, in order to improve the chemical resistance of a lubricating layer containing this compound and to suppress spin-off.

[0044] As a result, the terminal groups arranged at the ends of the skeletons containing perfluoropolyether chains (and, when there are a plurality of perfluoropolyether chains, the linking groups arranged between the perfluoropolyether chains) each have a predetermined number of polar groups, and an erythritol structure (—O—CH ) is formed at at least one end of the skeletons containing perfluoropolyether chains. ２ -CH(OH)-CH(OH)-CH ２ The present inventors have found that a fluorine-containing ether compound represented by formula (1) having a terminal group represented by formula (2) containing —O— can be used.

[0045] In the fluorine-containing ether compound represented by formula (1), due to the synergistic effects of <1> to <3> shown below, hydroxyl groups that are not involved in interactions with the protective layer or intramolecular interactions are generated, and polar groups that can be involved in intermolecular interactions are easily formed. Therefore, it is presumed that a lubricating layer containing the fluorine-containing ether compound represented by formula (1) is less likely to scatter as the magnetic recording medium rotates, and spin-off can be suppressed.

[0046] Furthermore, in the fluorine-containing ether compound represented by formula (1), the synergistic effects of <1> to <3> shown below suppress the interaction between polar groups within the molecule, and hydroxyl groups that can participate in intermolecular interactions are easily formed. Therefore, even if the number of polar groups contained in the compound is small, a sufficient number of polar groups that can participate in interactions with the protective layer and intermolecular interactions can be ensured. Therefore, the increase in surface free energy caused by increasing the number of polar groups contained in the fluorine-containing ether compound can be suppressed. As a result, it is presumed that the lubricating layer containing the fluorine-containing ether compound represented by formula (1) can prevent the incorporation of chemical contaminants due to the polar groups in the fluorine-containing ether compound inducing chemical contaminants, and has low interaction with chemical contaminants and excellent chemical resistance.

[0047] <1> The two hydroxyl groups in the erythritol structure are in the opposite conformation relative to the carbon chain in the erythritol structure, and therefore only one of the two hydroxyl groups can interact with the active site on the protective layer. This makes it easy to ensure the number of hydroxyl groups that can interact with the protective layer and the number of hydroxyl groups that are not involved in the interaction with the protective layer but are involved in intermolecular interactions, and also makes it possible to suppress an increase in surface free energy caused by increasing the number of polar groups in the compound, compared to compounds that do not contain an erythritol structure.

[0048] <2> The erythritol structure, whose bulkiness restricts its movement, imparts appropriate rigidity to the fluorinated ether compound molecule, thereby restricting the interaction between polar groups within the molecule and making the polar groups in the compound more likely to participate in intermolecular interactions between fluorinated ether compounds.

[0049] <3> In the terminal group represented by formula (2), oxygen atoms are located at both ends of the erythritol structure. Because these oxygen atoms rotate freely and easily, the internal 1,2-diol structure contained in the terminal group represented by formula (2) can move independently. Therefore, the internal 1,2-diol structure of the erythritol structure in the compound is unlikely to be inhibited from participating in intermolecular interactions.

[0050] On the other hand, for example, if the mobility of the fluorine-containing ether compound is too high, the polar groups contained in the fluorine-containing ether compound are likely to form intramolecular interactions.Therefore, the polar groups are less likely to participate in intermolecular interactions.In addition, if all of the multiple polar groups contained in the fluorine-containing ether compound are arranged with a sufficient distance between adjacent polar groups, all of the polar groups are likely to participate in interactions with the protective layer, and the interactions between the fluorine-containing ether compounds due to the polar groups cannot be sufficiently obtained.

[0051] Furthermore, the present inventors have confirmed that by using a lubricant containing a fluorinated ether compound represented by formula (1), it is possible to form a lubricating layer that has good chemical resistance and can suppress spin-off even when the thickness is reduced, and have arrived at the present invention.

[0052] The fluorine-containing ether compound, lubricant for magnetic recording media, and magnetic recording media of the present invention are described in detail below. It should be noted that the present invention is not limited to the following embodiments. Note that the term "polar group" in this specification does not include halogeno groups (such as -F, -Cl, and -Br) or ether bonds (-O-).

[0053] [Fluorine-containing ether compound] The fluorine-containing ether compound of the present embodiment is represented by the following formula (1): １ -CH ２ -R ２ [-CH ２ -R ３ -CH ２ -R ２ ] ｘ -CH ２ -R ４ (1) (In formula (1), x represents an integer of 0 to 2. R ２ is a perfluoropolyether chain. When x is 1 or 2, (x+1) R ２ may be the same in part or in whole, or may be different from each other. ３ is a divalent linking group having 1 to 4 polar groups. When x is 2, two R ３ may be the same or different from each other. １ and R ４ are each independently a terminal group having 1 to 4 polar groups and 1 to 50 carbon atoms. １ and R ４ At least one of the groups is a terminal group represented by the following formula (2):

[0054] (In formula (2), a represents an integer of 0 to 2, and b represents an integer of 1 to 6. A represents an organic group having 1 to 30 carbon atoms which may contain at least one of a polar group, a halogeno group, and an ether oxygen atom, or a hydrogen atom. However, the total number of polar groups contained in formula (2) is 2 to 4. When a is 2, the two b's may be the same or different.)

[0055] As shown in formula (1), when x is 0, the fluorine-containing ether compound of the present embodiment is２ At one end of the perfluoropolyether chain (hereinafter sometimes referred to as PFPE chain) represented by １ and the other end is connected via a methylene group to a terminal group represented by R ４ When x is 1 or 2, R ３ and a divalent linking group represented by R ２ and two or three perfluoropolyether chains represented by the formula (I) are alternately linked via methylene groups to form a skeleton. １ and 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.

[0056] In the fluorine-containing ether compound represented by formula (1), R ２ The number of PFPE chains (x+1) represented by the formula (1) is 1 to 3. When x is 1 or 2, in the fluorine-containing ether compound represented by the formula (1), adjacent R ２ Between them, there is a divalent linking group R ３ are placed.

[0057] The fluorine-containing ether compound represented by formula (1) is prevented from becoming too large in molecule compared with the compound having 4 or more PFPE chains.Therefore, the fluorine-containing ether compound represented by formula (1) is more likely to wet and spread on the protective layer compared with the compound having 4 or more PFPE chains, and can form a thin, uniformly thick lubricating layer.In order to form a more uniform lubricating layer, x is preferably 0 or 1, and more preferably 0.

[0058] (R １ and R ４ Terminal group represented by R １ and R ４ are each independently a terminal group having 1 to 4 polar groups and 1 to 50 carbon atoms. １ and R ４ At least one of the groups is a terminal group represented by the above formula (2).

[0059] R１ and R ４ is a terminal group that does not fall under formula (2), R １ and R ４ Among these, the number of polar groups contained in the terminal groups that do not fall under formula (2) is one or more. Also, the number of polar groups contained in the terminal groups represented by formula (2) is two or more. Therefore, 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. R １ and R ４ The number of polar groups contained in each of R is preferably two or more. １ and R ４ When the number of polar groups contained in each of is two or more, it becomes easier to ensure the number of polar groups that can participate in the interaction with the protective layer and the interaction between molecules, resulting in a fluorine-containing ether compound that can form a lubricating layer that has even better adhesion to the protective layer and can suppress spin-off.

[0060] R １ and R ４ The number of polar groups contained in each of R is 4 or less. Therefore, in the lubricating layer containing the fluorine-containing ether compound, the polarity of the fluorine-containing ether compound is too high, and the fluorine-containing ether compound aggregates to form lumps, which can prevent the smoothness of the lubricating layer from being lost. １ and R ３ When the number of polar groups contained in each of R is four or less, the surface free energy of the fluorine-containing ether compound becomes too high, which can prevent chemical contaminants from being incorporated into the magnetic recording medium, and the fluorine-containing ether compound can form a lubricating layer with high chemical resistance. １ and R ４ The number of polar groups contained in each of the formulas is preferably 3 or less.

[0061] R in formula (1) １ and R ４ The total number of polar groups contained in is preferably 3 or more and 6 or less, and more preferably 4 to 6. Since the total number of polar groups is 3 or more, R １ and R ４The interaction between the polar groups and the protective layer is effectively obtained. As a result, a fluorine-containing ether compound can be obtained that can form a lubricating layer with high adhesion to the protective layer, and a lubricating layer with excellent chemical resistance and spin-off resistance can be obtained. Furthermore, if the total number of polar groups is 6 or less, the surface free energy of the fluorine-containing ether compound is too high, which can prevent chemical contaminants from being incorporated into the lubricating layer. Therefore, a lubricating layer with better chemical resistance can be formed.

[0062] R １ and R ４ The polar groups contained in each of R may be the same in part or in whole, or may be different from each other. 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.

[0063] R １ and R ４ The polar groups contained in the hydroxyl group (-OH), carboxyl group (-COOH), formyl group (-(C=O)H), carbonyl group (-(C=O)R ７ ;R ７ is an organic group, a sulfo group (-SO ３ H), a cyano group (—CN), and a group having an amide bond (—NR ８ COR ９ or -CONR １０ R １１ ;R ８ , R ９ , R １０ and R １１ are each independently a hydrogen atom or an organic group.), an amino group (—NR １２ R １３ ;R １２ and R １３are each independently a hydrogen atom or an organic group.) The group having an amide bond is preferably a group bonded at a carbon atom constituting the amide bond as shown in the above formula (for example, a carboxamide group (-C(=O)NH ２ )) and a group bonding at a nitrogen atom constituting an amide bond (for example, an acetamide group (—NHC(═O)CH ３ In the group having an amide bond, the R ８ and R ９ may be bonded to each other to form a ring, １０ and R １１ may be bonded to each other to form a ring. ８ , R ９ , R １０ and R １１ 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.

[0064] 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.

[0065] R １ and R ４ When one of R is an end group that does not fall under the formula (2), the end group that does not fall under the formula (2) preferably contains at least one hydroxyl group, because this results in a more uniform coating state of the fluorine-containing ether compound on the protective layer. １ and R ４ Even if only one of the terminal groups is represented by formula (2), R １ and R ４ Even when both of R are terminal groups represented by formula (2), １and a polar group having R ４ It is preferable that all of the polar groups in R are hydroxyl groups. １ and R ４ When all of the polar groups of are hydroxyl groups, the fluorine-containing ether compound can be more uniformly coated on the protective layer.

[0066] R １ and R ４ is a terminal group that does not fall under formula (2), R １ and R ４ The number of carbon atoms contained in the terminal group not corresponding to formula (2) is 1 or more. The terminal group represented by formula (2) has an erythritol structure (—O—CH ２ -CH(OH)-CH(OH)-CH ２ The fluorine-containing ether compound represented by formula (1) contains at least 4 or more carbon atoms having R １ and R ４ Since the number of carbon atoms in the terminal group represented by R is 1 or more, the surface free energy of the terminal group can be maintained low. This makes it possible to prevent chemical contaminants from being attracted to the lubricating layer, and to form a lubricating layer with good chemical resistance. １ and R ４ is a terminal group that does not fall under formula (2), R １ and R ４ Among these, the number of carbon atoms contained in the terminal group not corresponding to formula (2) is preferably 3 or more, and more preferably 4 or more.

[0067] R １ and R ４ is a terminal group that does not fall under formula (2), R １ and R ４ The number of carbon atoms contained in the terminal group not corresponding to formula (2) is 50 or less. The terminal group represented by formula (2) has a glycerin structure (—O—CH ２ -CH(OH)-CH ２R has a total of 50 or less carbon atoms, and R has a structure in which a glycerin structure is amplified by (b-1) methylene groups and has 16 or less carbon atoms, an erythritol structure having 4 carbon atoms, and A has 30 or less carbon atoms. １ and R ４ Since the number of carbon atoms in each of the terminal groups represented by the formula (I) is 50 or less, the terminal groups have 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, it is possible to form a lubricating layer that can suppress spin-off. １ and R ４ The number of carbon atoms in each of the terminal groups represented by the following formulas is preferably 20 or less, and more preferably 15 or less.

[0068] (Terminal group represented by formula (2)) R １ and R ４ At least one of the terminal groups represented by the formula (2) is a terminal group represented by the formula (2). ２ A methylene group (-CH ２ -) (ether oxygen atom). ２ The oxygen atom bonded to the methylene group bonded to formula (1) forms an ether bond (—O—) with the atoms bonded to both sides of it. This ether bond imparts appropriate flexibility to the fluorine-containing ether compound represented by formula (1) and increases the affinity between the polar group of the terminal group represented by formula (2) and the protective layer. As a result, the fluorine-containing ether compound represented by formula (1) can form a lubricating layer that has excellent adhesion to the protective layer.

[0069] The terminal group represented by formula (2) has an erythritol structure (—O—CH ２ -CH(OH)-CH(OH)-CH ２ Therefore, a lubricating layer containing the fluorine-containing ether compound represented by formula (1) has good chemical resistance and can suppress spin-off.

[0070] In formula (2), A is an organic group having 1 to 30 carbon atoms which may contain at least one of a polar group, a halogeno group, and an ether oxygen atom, or a hydrogen atom.

[0071] The terminal group represented by formula (2) has a hydrogen atom or an organic group represented by A having 1 to 30 carbon atoms. When A is an organic group having 1 to 30 carbon atoms, A has 1 or more carbon atoms, so that the compound is appropriately rigid, and intramolecular interactions of polar groups contained in the fluorinated ether compound are suppressed. Furthermore, since A has 30 or less carbon atoms, it is possible to prevent the terminal group represented by formula (2) from becoming too bulky, which would hinder the movement of polar groups contained in the fluorinated ether compound and inhibit the interaction between the polar groups and the protective layer. When A is an organic group having 1 to 30 carbon atoms, A preferably has 1 to 15 carbon atoms, and more preferably has 2 to 10 carbon atoms.

[0072] In formula (2), when A is an organic group having 1 to 30 carbon atoms and a is 0, A may contain one or two polar groups. Also, when A is an organic group having 1 to 30 carbon atoms and a is 1, A may contain one polar group. Also, when A is an organic group having 1 to 30 carbon atoms and a is 2, A does not contain a polar group. When A contains one or two polar groups, the adhesion of the lubricating layer containing the fluorinated ether compound represented by formula (1) to the protective layer is improved, and a sufficient coating state can be obtained even if the thickness is reduced. Also, when A contains a polar group, the number of polar groups is preferably one. In this case, the surface free energy of the fluorinated ether compound represented by formula (1) becomes too high, which can prevent chemical substances from being induced from the environment.

[0073] When A in formula (2) is an organic group having 1 to 30 carbon atoms and containing a polar group, the polar group is preferably a polar group selected from the group consisting of a hydroxyl group, a cyano group, and a group having an amide bond, as described above.

[0074] In formula (2), when A is an organic group having 1 to 30 carbon atoms, A may contain an ether oxygen atom. In this case, the ether oxygen atom imparts appropriate flexibility to the fluorinated ether compound represented by formula (1) and increases the affinity between the polar group and the protective layer. When A contains an ether oxygen atom, the number of ether oxygen atoms is preferably 1 or 2. In this case, the fluorinated ether compound represented by formula (1) can be prevented from becoming too flexible due to the ether oxygen atom contained in A, thereby preventing intramolecular interactions from occurring.

[0075] In formula (2), when A is an organic group having 1 to 30 carbon atoms, A may have a halogeno group. In this case, the surface free energy of A in formula (2) is lower than when A is an organic group not having a halogeno group. As a result, the resulting fluorine-containing ether compound can better suppress the induction of chemical substances from the environment and can form a lubricating layer with good chemical substance resistance.

[0076] When A contains a halogeno group, the halogeno group is preferably a fluoro group (-F) or a chloro group (-Cl), and more preferably a fluoro group, because this has a significant effect of lowering the surface free energy of A.

[0077] In formula (2), when A is an organic group having 1 to 30 carbon atoms, A is preferably an acyclic organic group. When A is an acyclic organic group, it is not too bulky compared to when A is an organic group having a cyclic structure. Therefore, the organic group represented by A can prevent the movement of the polar group contained in the fluorinated ether compound from being hindered, and the interaction between the polar group and the protective layer can be prevented from being inhibited. The acyclic organic group may be linear or branched.

[0078] In formula (2), a is an integer of 0 to 2. That is, the terminal group represented by formula (2) is an internal 1,2-diol structure (—CH ) contained in the erythritol structure. ２ -CH(OH)-CH(OH)-CH ２ -) and R ２ adjacent to the methylene group (-CH ２ Between the glycerin structure (—O—CH２ -CH(OH)-CH ２ -O-) and / or a structure in which the glycerin structure is increased by (b-1) methylene groups.

[0079] Since the glycerin structure and the structure obtained by increasing the carbon content of the glycerin structure have appropriate rigidity, when a is 1 or 2, the terminal group represented by formula (2) can be prevented from forming an intramolecular interaction. Furthermore, the ether bond in the glycerin structure and the structure obtained by increasing the carbon content of the glycerin structure imparts appropriate mobility to the terminal group represented by formula (2), so that the hydroxyl group of the erythritol structure is more likely to participate in the intermolecular interaction. Therefore, the polar group in the fluorine-containing ether compound represented by formula (1) can more easily form an intermolecular interaction. As a result, the lubricating layer containing the fluorine-containing ether compound represented by formula (1) is less likely to scatter due to the rotation of the magnetic recording medium, and has even better spin-off resistance.

[0080] In formula (2), b is an integer of 1 to 6, and preferably an integer of 1 to 4. When a is 2, each of [—CH ２ -CH(OH)-(CH ２ ) ｂ The b's contained in the group --O-- may be the same or different.

[0081] The terminal group represented by formula (2) is preferably any one of the following formulae (2-1) to (2-5).

[0082] (In formula (2-1), c represents an integer of 1 to 6. X represents a hydroxyl group, an acetamide group, a carboxamide group, or a cyano group.) (In formula (2-2), a1 represents 0 or 1. b1 represents an integer of 1 to 6. d represents an integer of 1 to 4.) (In formula (2-3), a2 represents 0 or 1. b2 represents an integer of 1 to 6. e represents an integer of 0 to 7.) (In formula (2-4), a3 represents 0 or 1. b3 represents an integer of 1 to 6. f represents an integer of 0 to 6.) (In formula (2-6), f2 represents an integer of 1 to 6.)

[0083] The terminal group represented by formula (2-1) is a group in which a in formula (2) is 0 and A is -(CH２ ) ｃ It corresponds to a structure where c is an integer of 1 to 6. X is any one of a hydroxyl group, an acetamide group, a carboxamide group, and a cyano group.

[0084] The terminal group represented by formula (2-1) has a polar group represented by X at the terminal side of the molecule in addition to the hydroxyl group of the erythritol structure. The polar group represented by X is flexible and therefore likely to be involved in both interactions with the protective layer and intermolecular interactions. As a result, a sufficient number of polar groups involved in interactions between the fluorinated ether compound and the protective layer and intermolecular interactions between fluorinated ether compounds can be ensured, and a lubricating layer with excellent spin-off resistance can be formed.

[0085] In the terminal group represented by formula (2-1), X is a hydroxyl group, an acetamide group, a carboxamide group, or a cyano group, and therefore the fluorine-containing ether compound is capable of forming a lubricating layer that has stronger interaction with the protective layer. X is preferably a hydroxyl group, 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.

[0086] Since c in formula (2-1) is 1 or more, the terminal group represented by formula (2-1) has sufficient rigidity. Furthermore, since c is 6 or less, the terminal group represented by formula (2-1) does not become too bulky due to an excessively large c. Therefore, the movement of the hydroxyl group contained in the erythritol structure in the terminal group represented by formula (2-1) is prevented by the c methylene groups, and the interaction with the protective layer and the intermolecular interaction between the fluorinated ether compounds are prevented from being hindered. c is preferably 1 to 4, and more preferably 2 to 3.

[0087] a1 in formula (2-2), a2 in formula (2-3), and a3 in formula (2-4) correspond to a in formula (2) and represent 0 or 1. Furthermore, b1 in formula (2-2), b2 in formula (2-3), and b3 in formula (2-4) correspond to b in formula (2) and represent an integer from 1 to 6.

[0088] a1 in formula (2-2), a2 in formula (2-3), and a3 in formula (2-4) are 0 or 1. Therefore, the number of hydroxyl groups possessed by the terminal groups represented by formulas (2-2), (2-3), and (2-4) is 2 or 3. Therefore, all of the fluorine-containing ether compounds having terminal groups represented by formulas (2-2), (2-3), and (2-4) can form a lubricating layer with high chemical resistance that is less likely to incorporate chemical contaminants into the magnetic recording medium, without the surface free energy becoming too high due to the large number of polar groups in the compound.

[0089] The terminal groups represented by formulas (2-2), (2-3), and (2-4) have sufficient rigidity because a1, a2, and a3 are 1 or greater. Furthermore, because b1, b2, and b3 are 6 or less, the terminal groups represented by formulas (2-2), (2-3), and (2-4) do not become too bulky due to excessively large values ​​of b1, b2, and b3. Therefore, the movement of the hydroxyl groups in the terminal groups represented by formulas (2-2), (2-3), and (2-4) is hindered by the methylene groups b1, b2, and b3, which can prevent the interaction with the protective layer and the intermolecular interaction between the fluorinated ether compounds from being hindered. Each of b1, b2, and b3 is preferably 1 to 4, and more preferably 1 to 2.

[0090] -(CH ２ ) ｄ -CH=CH ２ corresponds to A in formula (2). In formula (2-2), d represents an integer of 1 to 4. The terminal group represented by formula (2-2) has a vinyl group at the terminal side of the molecule. Because the vinyl group is rigid, it is possible to prevent the hydroxyl group located near the vinyl group from incorporating chemical contaminants, resulting in a fluorine-containing ether compound that can form a lubricating layer with high chemical resistance.

[0091] Since d in formula (2-2) is 1 or more, the terminal group represented by formula (2-2) has sufficient rigidity. Furthermore, since d is 4 or less, the terminal group represented by formula (2-2) does not become too bulky due to an excessively large d. Therefore, the movement of the hydroxyl group in the terminal group represented by formula (2-2) is prevented by the d methylene groups bonded to the rigid vinyl group, and the interaction with the protective layer and the intermolecular interaction between the fluorinated ether compounds are prevented from being hindered. d is preferably 1 to 4, and more preferably 1 to 2.

[0092] -(CH ２ ) ｅ -CH ３ corresponds to A in formula (2). In formula (2-3), e represents an integer of 0 to 7. The terminal group represented by formula (2-3) has a saturated hydrocarbon group at the terminal side of the molecule. The oxygen atom adjacent to the saturated hydrocarbon group in formula (2-3) (the oxygen atom in the erythritol structure) forms an ether bond with the atoms bonded to both sides of it. Because this ether bond is flexible, the hydroxyl group in the erythritol structure is considered to be easily involved in intermolecular interactions. As a result, a sufficient number of polar groups involved in intermolecular interactions between fluorine-containing ether compounds can be ensured, and a lubricating layer with excellent spin-off resistance can be formed.

[0093] The terminal group represented by formula (2-3) has sufficient rigidity even when e is 0. When e is 1 or more, it has even better rigidity. Furthermore, since e is 7 or less, the terminal group represented by formula (2-3) does not become too bulky due to e being too large. Therefore, the movement of the hydroxyl group in the terminal group represented by formula (2-3) is hindered by the e methylene groups, and the interaction with the protective layer and the intermolecular interaction between the fluorinated ether compounds are prevented from being hindered. e is preferably 0 to 4, and more preferably 0 to 2.

[0094] -CH in formula (2-4) ２ -(CF ２ ) ｆ -CF ３corresponds to A in formula (2). In formula (2-4), f represents an integer of 0 to 6. The terminal group represented by formula (2-4) has a fluorinated saturated hydrocarbon group at the terminal side of the molecule. The fluorinated saturated hydrocarbon group reduces the surface free energy of the fluorinated ether compound. For this reason, a fluorinated ether compound having a terminal group represented by formula (2-4) can form a lubricating layer that is highly resistant to chemical substances and that is less likely to incorporate chemical contaminants into magnetic recording media.

[0095] The terminal group represented by formula (2-4) has sufficient rigidity even when f is 0. When f is 1 or more, it has better rigidity. In addition, since f is 6 or less, the terminal group represented by formula (2-4) does not become too bulky due to too large f. Therefore, the movement of the hydroxyl group in the terminal group represented by formula (2-4) is controlled by f -CF ２ The number f is preferably 0 to 4, and more preferably 0 to 2.

[0096] The terminal group represented by formula (2-5) corresponds to a structure in which a in formula (2) is 0 and A is a hydrogen atom (the hydrogen atom bonds with an adjacent oxygen atom to form a hydroxyl group). The terminal group represented by formula (2-5) has a hydroxyl group at the extreme end in addition to the two hydroxyl groups in the internal 1,2-diol structure contained in the erythritol structure. In other words, the terminal group represented by formula (2-5) has a 1,2,3-triol structure.

[0097] The 1,2,3-triol structure is difficult to form intramolecular interactions because its motion is controlled by steric repulsion. Therefore, the hydroxyl group in the terminal group represented by formula (2-5) is involved in both the interaction with the protective layer and the intermolecular interaction. As a result, the fluorine-containing ether compound having the terminal group represented by formula (2-5) has a sufficient number of polar groups involved in the interaction with the protective layer and the intermolecular interaction between fluorine-containing ether compounds, and can form a lubricating layer with excellent spin-off resistance.

[0098] The terminal group represented by formula (2-6) is a group in which a in formula (2) is 0 and A is -(CH ２ ) ｆ２ -CH(OH)CH ２ OH. f2 represents an integer of 1 to 6. The terminal group represented by formula (2-6) has two hydroxyl groups at the terminal side of the molecule in addition to the hydroxyl group of the erythritol structure. These hydroxyl groups are flexible and therefore easily involved in both interactions with the protective layer and intermolecular interactions. As a result, a sufficient number of polar groups involved in the interaction between the fluorinated ether compound and the protective layer, and intermolecular interactions between fluorinated ether compounds, can be ensured, allowing the formation of a lubricating layer with excellent spin-off resistance. Furthermore, since these hydroxyl groups have a 1,2-diol structure, like the hydroxyl groups of the erythritol structure, all hydroxyl groups can interact evenly. As a result, the coating state of the fluorinated ether compound on the protective layer becomes more uniform, allowing the formation of a lubricating layer with better adhesion. Since f2 in formula (2-6) is 1 or more, the terminal group represented by formula (2-6) has sufficient rigidity. Furthermore, since f2 is 6 or less, the terminal group represented by formula (2-6) does not become too bulky due to an excessively large f2. Therefore, the movement of the hydroxyl group contained in the erythritol structure in the terminal group represented by formula (2-1) is hindered by f2 methylene groups, which can prevent the interaction with the protective layer and the intermolecular interaction between the fluorinated ether compounds from being inhibited. f2 is preferably 1 to 4, more preferably 1 or 2, and most preferably 1.

[0099] In the fluorine-containing ether compound represented by formula (1), R １ and R ４ may be the same or different. １ and R ４ In this case, the fluorine-containing ether compound can be produced easily and efficiently. １ and R ４ "The same" means that R １ Atoms contained in and R ４ and the atoms contained in -CH ２ -R２ [-CH ２ -R ３ -CH ２ -R ２ ] ｘ -CH ２ - means that they are arranged symmetrically with respect to each other.

[0100] In the fluorine-containing ether compound represented by formula (1), R １ and R ４ If different from １ and R ４ may each independently be a terminal group represented by formula (2), or R １ and R ４ Only one of the terminal groups may be an end group represented by formula (2), and the other may be an end group that does not fall under formula (2). The end group that does not fall under formula (2) may be, as described above, an end group having 1 to 4 polar groups and 1 to 50 carbon atoms.

[0101] (Terminal group represented by formula (3)) R １ and R ４ When only one of the above is an end group represented by formula (2) and the other is an end group not corresponding to formula (2), the end group not corresponding to formula (2) is preferably represented by the following formula (3):

[0102] (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. B represents an alkyl group which may have only one polar group, an organic group containing a carbon-carbon unsaturated bond which may have only one polar group, or a hydrogen atom.)

[0103] The terminal group represented by formula (3) is R ２ A methylene group (-CH ２The oxygen atom located at the end of the terminal group represented by formula (3) forms an ether bond (-O-) with atoms bonded to both sides of it. This ether bond imparts appropriate flexibility to the fluorine-containing ether compound represented by formula (1) and increases the affinity between the polar group of the terminal group represented by formula (3) and the protective layer. As a result, the fluorine-containing ether compound represented by formula (1) can form a lubricating layer that has excellent adhesion to the protective layer.

[0104] In formula (3), l is an integer of 1 to 3, preferably an integer of 1 or 2, and more 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 chemical substances in the environment from being attracted to the lubricating layer, and a lubricating layer with good chemical substance resistance can be obtained.

[0105] When l in formula (3) is 2 or 3, two or three repeating units (-(CH ２ ) ｍ -CH(OH)-(CH ２ ) ｎ The combinations of m and n in the formula (3) may be different from each other, or some or all of them may be the same. In the formula (3), l m's each independently represent an integer of 1 to 6. In the formula (3), l n's each independently represent an integer of 1 to 6. In the formula (3), one repeating unit (-(CH ２ ) ｍ -CH(OH)-(CH ２ ) ｎ In the formula (I), at least one of m and n is 1. In this case, it is possible to prevent the mobility of the hydroxyl group in the repeating unit from decreasing due to the alkylene group having too many carbon atoms between the carbon atom to which the hydroxyl group is bonded and the ether oxygen atom.

[0106] In formula (3), B represents an alkyl group which may have only one polar group, an organic group containing a carbon-carbon unsaturated bond which may have only one polar group, or a hydrogen atom. When B in formula (3) is an alkyl group which does not have a polar group, examples of B include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, and a hexyl group.

[0107] When B in formula (3) is an alkyl group having a polar group, the polar group is R １ and R ４ Of the above polar groups, a polar group selected from the group consisting of a hydroxyl group, a cyano group, and a group having an amide bond is more preferred.

[0108] When B in formula (3) is an alkyl group having a polar group, examples of B 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 1-carboxymethyl group, a 2-carboxyethyl group, a 3-carboxypropyl group, a 1-carbonylmethyl group, a 2-carbonylethyl group, a 3-carbonylpropyl group, a 1-acetylmethyl group, a 2-acetylethyl group, a 3-acetylpropyl group, a 2-sulfoethyl group, a 3-sulfopropyl group, a 1-cyanomethyl 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 1-carboxamidomethyl group, a 2-carboxamidoethyl group, a 3-carboxamidopropyl group, and a 4-carboxamidobutyl group.

[0109] 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 1-cyanomethyl group, a 2-cyanoethyl group, a 3-cyanopropyl group, a 2-acetamidoethyl group, a 1-carboxamidomethyl 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, a 2-acetamidoethyl group, and a 1-carboxamidomethyl group is more preferred.

[0110] When B in formula (3) is an organic group containing a carbon-carbon unsaturated bond which may have only one polar group, examples of B include an organic group containing at least one selected from an aromatic hydrocarbon, an unsaturated heterocycle, an alkenyl group, and an alkynyl group.

[0111] When B in formula (3) is an organic group containing a carbon-carbon unsaturated bond which may have only one polar group, B is preferably a phenyl group, a methoxyphenyl group, a fluorinated phenyl group, an acetamidophenyl group, a carboxamidophenyl group, a cyanophenyl 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 methyl Examples thereof include an ethyl thiazolylethyl group, an isothiazolyl group, 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.

[0112] Among the organic groups containing a carbon-carbon unsaturated bond which may have only one polar group, any of a phenyl group, a methoxyphenyl group, an acetamidophenyl group, a carboxamidophenyl group, a cyanophenyl 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 any of a phenyl group, a methoxyphenyl group, a carboxamidophenyl group, an allyl group, and a butenyl group is more preferred. In this case, the terminal group represented by formula (3) has sufficient rigidity and is not too bulky, and the movement of the hydroxyl group in formula (3) is prevented from being hindered, thereby preventing the interaction with the protective layer from being inhibited.

[0113] When B in formula (3) is a hydrogen atom, B forms a hydroxyl group together with the oxygen atom in formula (3).

[0114] The terminal group represented by formula (3) is more preferably represented by any one of the following formulas (3-1) to (3-3).

[0115] (In formula (3-1), p represents 0 or 1. q1, q2, q3, and q4 each independently represent an integer of 1 to 6. When p is 0, the total value of q1 and q4 is 2 to 10. When p is 1, the total value of q1, q2, q3, and q4 is 4 to 10. When p is 1, at least one of q2 and q3 is 1. D represents a polar group, a vinyl group, an ethynyl group, or an aryl group which may have a substituent. However, when D is the aryl group which may have a substituent, the number of polar groups contained in D is 0 or 1.) (In formula (3-2), r represents 0 or 1. s1, s2, and s3 each independently represent an integer of 1 to 6. When r is 1, the total value of s1, s2, and s3 is 3 to 8. When r is 1, at least one of s2 and s3 is 1.) (In formula (3-3), t represents 1 or 2. Each of the five E's independently represents a polar group, an alkoxy group having 1 to 8 carbon atoms, a halogeno group, or a hydrogen atom. However, when the five E's include a polar group, the total number of polar groups among the five E's is 1.)

[0116] The terminal group represented by formula (3-1) has one or two glycerin structures (—O—CH２ -CH(OH)-CH ２ -O-) and / or a structure in which a glycerin structure is carbon-rich with a methylene group is linked, and D is bonded to the end of the structure via at least one methylene group. The glycerin structure and a structure in which a glycerin structure is carbon-rich have appropriate rigidity, and therefore, the hydroxyl group contained in the terminal group represented by formula (3-1) can be prevented from forming an intramolecular interaction. Furthermore, the ether bond possessed by the glycerin structure and a structure in which a glycerin structure is carbon-rich imparts appropriate mobility to the terminal group represented by formula (3-1). Therefore, the hydroxyl group contained in the terminal group represented by formula (3-1) is likely to be involved in an interaction with the protective layer or an intermolecular interaction between fluorine-containing ether compounds. As a result, a lubricating layer with excellent chemical resistance and spin-off resistance can be formed.

[0117] In formula (3-1), D represents a polar group, a vinyl group, an ethynyl group, or an aryl group which may have a substituent. When D is a polar group, D is R １ and R ４ Among the above polar groups, a polar group selected from the group consisting of a hydroxyl group, a cyano group, and a group having an amide bond is more preferred. When D is an aryl group which may have a substituent, it is preferably an aryl group which may have a substituent that is included in the organic group which can be used when B in the above formula (3) is an organic group containing a carbon-carbon unsaturated bond which may have only one polar group.

[0118] In the terminal group represented by formula (3-1), the total value of q1 and q4 when p is 0, and the total value of q1, q2, q3, and q4 when p is 1, is 10 or less, so the alkylene chain in the main chain portion is not too long. Therefore, the long rigid alkylene chain arranged in the main chain portion of the terminal group represented by formula (3-1) reduces the flexibility of the terminal portion of the fluorine-containing ether compound, weakens the interaction between the hydroxyl group contained in the terminal group represented by formula (3-1) and the protective layer, and prevents the terminal portion from lifting off the protective layer. Therefore, it is possible to prevent the terminal group represented by formula (3-1) from containing too many carbon atoms, making it difficult for the lubricating layer containing the fluorine-containing ether compound to uniformly cover the entire surface of the protective layer.

[0119] In the terminal group represented by formula (3-1), when p is 0, the total value of q1 and q4 is 2 or more, and when p is 1, the total value of q1, q2, q3, and q4 is 4 or more, so that the number of carbon atoms in the main chain portion of formula (3-1) is not too small. Therefore, it is possible to prevent the polarity of the terminal group represented by formula (3-1) from being too high, and to prevent the fluorine-containing ether compound from aggregating.

[0120] q1, q2, q3, and q4 each represent an integer of 1 to 6, preferably 1 to 3, and more preferably 1 or 2. At least one of q1, q2, q3, and q4 is preferably 2 or greater.

[0121] The terminal group represented by formula (3-2) is a glycerin structure (—O—CH ２ -CH(OH)-CH ２-O-) and / or a structure in which a glycerin structure is carbon-rich with a methylene group is linked, and a hydroxyl group is bonded to the terminal. The glycerin structure and a structure in which a glycerin structure is carbon-rich have appropriate rigidity, and therefore, the hydroxyl group contained in the terminal group represented by formula (3-2) can be prevented from forming an intramolecular interaction. Furthermore, the ether bond in the glycerin structure and a structure in which a glycerin structure is carbon-rich imparts appropriate mobility to the terminal group represented by formula (3-2). Therefore, the hydroxyl group contained in the terminal group represented by formula (3-2) is likely to be involved in an interaction with the protective layer or an intermolecular interaction between fluorine-containing ether compounds. As a result, a lubricating layer with excellent chemical resistance and spin-off resistance can be formed.

[0122] In the terminal group represented by formula (3-2), when r is 0, s1 is 6 or less, and when r is 1, the total value of s1, s2, and s3 is 8 or less, so the alkylene chain in the main chain portion is not too long. Therefore, the long rigid alkylene chain arranged in the main chain portion of the terminal group represented by formula (3-2) reduces the flexibility of the terminal portion of the fluorinated ether compound, weakening the interaction between the hydroxyl group contained in the terminal group represented by formula (3-2) and the protective layer, preventing the terminal portion from lifting up. Therefore, it is possible to prevent the terminal group represented by formula (3-2) from containing too many carbon atoms, which makes it difficult for the lubricating layer containing the fluorinated ether compound to uniformly cover the entire surface of the protective layer.

[0123] In the terminal group represented by formula (3-2), when r is 0 (when there are two hydroxyl groups), s1 is 1 or more, and when r is 1 (when there are three hydroxyl groups), the total value of s1, s2, and s3 is 3 or more, so that the number of carbon atoms in the main chain portion of formula (3-2) is not too small. Therefore, it is possible to prevent the polarity of the terminal group represented by formula (3-2) from being too high, and to prevent the fluorine-containing ether compound from aggregating.

[0124] Each of s1, s2, and s3 is an integer of 1 to 6, preferably 1 to 3, and more preferably 1 or 2. At least one of s1, s2, and s3 is preferably 2 or greater.

[0125] The terminal group represented by formula (3-3) is a glycerin structure (—O—CH ２ -CH(OH)-CH ２ The glycerin structure has an aryl group at the end of the -O-) or at the end of two linked glycerin structures. The glycerin structure has appropriate rigidity. Therefore, the hydroxyl group contained in the terminal group represented by formula (3-3) can be prevented from forming intramolecular interactions. In addition, the ether bond in the glycerin structure imparts appropriate mobility to the terminal group represented by formula (3-3). Therefore, the hydroxyl group contained in the terminal group represented by formula (3-3) is likely to be involved in interactions with the protective layer or in intermolecular interactions between fluorine-containing ether compounds. As a result, a lubricating layer with excellent chemical resistance and spin-off resistance can be formed.

[0126] In the terminal group represented by formula (3-3), five E's each independently represent a polar group, an alkoxy group having 1 to 8 carbon atoms, a halogeno group, or a hydrogen atom. When a polar group is included in the five E's, the total number of polar groups among the five E's is 1.

[0127] In the terminal group represented by formula (3-3), when the five E's contain polar groups, the polar groups are bonded to a rigid benzene ring that is difficult to freely rotate. Therefore, the hydroxyl group contained in the glycerin structure in formula (3-3) and the polar group contained in E's are suppressed from forming intramolecular interactions. Therefore, when the five E's contain polar groups, the fluorine-containing ether compound having the terminal group represented by formula (3-3) has a large number of polar groups that can participate in intermolecular interactions. As a result, the lubricating layer containing the fluorine-containing ether compound having the terminal group represented by formula (3-3) has a high spin-off suppression effect.

[0128] In the terminal group represented by formula (3-3), when none of the five E's contains a polar group, the surface free energy of the fluorinated ether compound is lower than when one of the five E's is a polar group. As a result, a lubricating layer containing a fluorinated ether compound having an terminal group represented by formula (3-3) can suppress the induction of chemical substances from the environment, and has higher chemical substance resistance.

[0129] In the terminal group represented by formula (3-3), when E is a polar group, E is R １ and R ４ Among the above polar groups, E is more preferably a polar group selected from the group consisting of a cyano group and a group having an amide bond, and is preferably a cyano group, an acetamide group (—NHC(═O)CH ３ ) or a carboxamide group (—C(═O)NH ２ ) is more preferable. When the polar group is a cyano group, an acetamide group, or a carboxamide group, the resulting fluorine-containing ether compound can form a lubricating layer with stronger interaction with the protective layer. In addition, since the acidity of a cyano group, an acetamide group, or a carboxamide group is not too high, a fluorine-containing ether compound having these groups hardly corrodes the substrate. When E is not a polar group, it is preferable that each E is independently a methoxy group, a fluoro group, or a hydrogen atom.

[0130] When one of the five E's in formula (3-3) is a polar group, the four E's other than the polar group may be partially or completely the same, or may be different from each other. When a polar group is included in the five E's, it is preferable that the four E's other than the polar group are all the same. When one of the five E's is a polar group, the position of the polar group may be any position of the five E's. When no polar group is included in the five E's in formula (3-3), the five E's may be partially or completely the same, or may be different from each other.

[0131] (Terminal group not corresponding to formula (3)) R １ and R ４ When only one of the above is an end group represented by formula (2) and the other is an end group not corresponding to formula (2), the end group not corresponding to formula (2) may be an end group not corresponding to formula (3). Examples of the end group not corresponding to formula (3) include end groups represented by the following formula (3-4) or (3-5).

[0132] (In formula (3-4), g1 represents an integer of 1 to 6. g1 R ａ and Rｂ each independently represents a hydrogen atom or a methyl group.) (In formula (3-5), g2 represents an integer of 1 to 6.)

[0133] g1 -CR in the terminal group represented by formula (3-4) ａ R ｂ - is -CH ２ -, -CH(CH ３ ) -, -C(CH ３ ) ２ - may be either.

[0134] In the terminal group represented by formula (3-4), R ａ and R ｂ is a hydrogen atom, R ａ and / or R ｂ is a methyl group, the terminal group does not become too bulky. Therefore, the movement of the hydroxyl group possessed by the terminal group is hindered, and the interaction of the hydroxyl group with the protective layer is prevented from being inhibited. As a result, when one of the two hydroxyl groups forming the terminal 1,2-diol structure interacts with the protective layer, the other hydroxyl group can more easily form an intermolecular interaction with a polar group in another fluorine-containing ether compound. As a result, a lubricating layer containing the fluorine-containing ether compound represented by formula (1) is less likely to scatter the fluorine-containing ether compound as the magnetic recording medium rotates, and has even better spin-off resistance.

[0135] In the terminal group represented by formula (3-4), the organic group located between the two glycerin structures is —CH(CH ３ )- and / or -C(CH ３ ) ２ When the compound contains -, the organic group becomes moderately rigid, and the intramolecular interaction between the hydroxyl groups of the terminal groups can be effectively suppressed. Therefore, the polar groups in the fluorine-containing ether compound represented by formula (1) can more easily form intermolecular interactions. As a result, the lubricating layer containing the fluorine-containing ether compound represented by formula (1) is less likely to scatter the fluorine-containing ether compound as the magnetic recording medium rotates, and has even better spin-off resistance.

[0136] Since g1 in formula (3-4) is 1 or more, the terminal group represented by formula (3-4) has appropriate rigidity. Furthermore, since g1 is 6 or less, the terminal group represented by formula (3-4) does not become too bulky, and the movement of the hydroxyl group of the terminal group is hindered, thereby preventing the interaction with the protective layer from being inhibited. g1 is preferably 1 to 4, and more preferably 1 to 2.

[0137] The terminal group represented by formula (3-5) is a group in which the organic group between the two glycerin structures is —CH ２ -(CF ２ ) ｇ２ -CH ２ -. g2 represents an integer of 1 to 6. The terminal group represented by formula (3-5) contains a linear perfluoroalkylene chain having 1 to 6 carbon atoms, which reduces affinity with chemical substances in the environment. As a result, a lubricating layer containing the fluorine-containing ether compound represented by formula (1) has good chemical substance resistance.

[0138] Since g2 in formula (3-5) is 1 or more, the terminal group represented by formula (3-5) becomes appropriately rigid, and intramolecular interactions can be suppressed. Furthermore, since g2 is 6 or less, the terminal group represented by formula (3-5) does not become too bulky, and it is possible to suppress the movement of the hydroxyl group being hindered and the inhibition of interaction with the protective layer. In formula (3-5), g2 is preferably 1 to 4, and more preferably 2 to 4.

[0139] (R ３ When x in the fluorine-containing ether compound represented by formula (1) is 1 or 2, the fluorine-containing ether compound has x R ３ Contains: ３ are arranged between adjacent PFPE chains via a methylene group. ３ is a divalent linking group having 1 to 4 polar groups, which allows the fluorine-containing ether compound to adhere to the protective layer.

[0140] In formula (1), when x is 2, two R ３ may be the same or different, and are preferably the same. ３When the two R ３ When the above formula (I) is the same as that of the formula (I), the fluorinated ether compound can be produced easily and efficiently.

[0141] In this specification, when x is 2, "two R 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.

[0142] x R in formula (1) ３ Each of R ３ Therefore, a fluorinated ether compound in which x is 1 or 2 has superior adhesion to the protective layer compared to a fluorinated ether compound in which x is 0, and can form a lubricating layer that has a high spin-off suppressing effect.

[0143] Also, R ３ Since the number of polar groups contained in R is 4 or less, the polarity of the fluorine-containing ether compound in which x is 1 or 2 becomes too high, which can prevent chemical substances from being taken up into the magnetic recording medium from the environment. As a result, the fluorine-containing ether compound can form a lubricating layer with high chemical resistance. ３ The number of polar groups contained in is preferably 3 or less.

[0144] R ３ The polar groups contained in the hydroxyl group (-OH), carboxyl group (-COOH), formyl group (-(C=O)H), carbonyl group (-(C=O)R ７ ;R ７ is an organic group, a sulfo group (-SO ３ H), a cyano group (—CN), and a group having an amide bond (—NR ８ COR ９ or -CONR １０ R １１ ;R ８ , R９ , R １０ and R １１ are each independently a hydrogen atom or an organic group.), an amino group (—NR １２ R １３ ;R １２ and R １３ are each independently a hydrogen atom or an organic group.

[0145] The group having an amide bond includes a group bonded at a carbon atom constituting the amide bond as shown in the above formula (for example, a carboxamide group (—C(═O)NH ２ )) and a group bonding at a nitrogen atom constituting an amide bond (for example, an acetamide group (—NHC(═O)CH ３ In the group having an amide bond, the R ８ and R ９ may be bonded to each other to form a ring, １０ and R １１ may be bonded to each other to form a ring. ８ , R ９ , R １０ and R １１ 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.

[0146] R ３ 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.

[0147] x R in formula (1) ３ The x polar groups in the formula (1) may be the same or different from each other. ３Each of the x R preferably contains at least one hydroxyl group. ３ It is more preferable that all of the polar groups of the protective layer are hydroxyl groups, since this results in a more uniform coating state of the fluorine-containing ether compound on the protective layer.

[0148] x R in formula (1) ３ are each preferably a linking group having 1 to 50 carbon atoms, more preferably a linking group having 3 to 50 carbon atoms, even more preferably a linking group having 3 to 20 carbon atoms, and most preferably a linking group having 4 to 15 carbon atoms. ３ When the number of carbon atoms in the linking group represented by R is 1 or more, the rigidity of the linking group can be ensured. ３ The polar group in the linking group represented by R can prevent chemical substances in the environment from being attracted to the lubricating layer, and a lubricating layer with good chemical substance resistance can be formed. ３ When the number of carbon atoms in the linking group represented by the formula (I) is 50 or less, the linking group has a flexible structure, and the adhesion between the lubricating layer containing the fluorine-containing ether compound and the protective layer is improved. As a result, a lubricating layer capable of suppressing spin-off can be obtained.

[0149] x R in formula (1) ３ is preferably a divalent linking group having oxygen atoms at both ends. ３ The oxygen atoms located at both ends of the divalent linking group represented by R ３ methylene groups (-CH ２ These ether bonds impart appropriate flexibility to the fluorine-containing ether compound represented by formula (1), and R ３ This increases the affinity between the polar group of the divalent linking group represented by the formula (I) and the protective layer.

[0150] x R in formula (1) ３ are each independently a divalent linking group having 3 to 50 carbon atoms, having 1 to 3 hydroxyl groups and oxygen atoms at both ends bonding to adjacent methylene groups. ３are each independently any one selected from the linking groups represented by the following formulas (4-1) to (4-6).

[0151] (In formula (4-1), u1 represents an integer of 0 to 6, and u2 represents an integer of 0 to 6, provided that at least one of u1 and u2 is 0. The oxygen atom at the left end of formula (4-1) is R １ The oxygen atom at the right end is bonded to the methylene group at the side of the ４ (In formula (4-2), v represents an integer of 1 to 2. The oxygen atom at the left end of formula (4-2) is bonded to the methylene group on the R １ The oxygen atom at the right end is bonded to the methylene group at the side of the ４ (In formula (4-3), w represents an integer of 0 to 6. The oxygen atom at the left end of formula (4-3) is bonded to the methylene group on the R １ The oxygen atom at the right end is bonded to the methylene group at the side of the ４ (In formula (4-4), x1 represents an integer of 0 to 5, and x2 represents an integer of 0 to 5, provided that at least one of x1 and x2 is an integer of 1 to 5. The oxygen atom at the left end of formula (4-4) is bonded to the methylene group of R in formula (1). １ The oxygen atom at the right end is bonded to the methylene group at the side of the ４ (In formula (4-5), y1 represents an integer of 1 to 5, and y2 represents an integer of 1 to 5. The oxygen atom at the left end of formula (4-5) is bonded to the methylene group at the R １ The oxygen atom at the right end is bonded to the methylene group at the side of the ４ In formula (4-6), z represents an integer of 1 to 6. ｃ and R ｄ each independently represents a hydrogen atom, a fluorine atom, or a methyl group. The oxygen atom at the left terminal of formula (4-6) is R １ The oxygen atom at the right end is bonded to the methylene group at the side of the ４ It bonds to the methylene group on the side.)

[0152] The linking group represented by formula (4-1) is a glycerin structure (—O—CH ２ -CH(OH)-CH ２ -O-), or a structure in which one to six methylene groups are added to a glycerin structure. The linking group represented by formula (4-1) contains only one hydroxyl group, and the polarity of the linking group is maintained low. As a result, it is possible to effectively prevent the intrusion of chemical substances in the environment, and form a lubricating layer with high chemical resistance.

[0153] In formula (4-1), since at least one of u1 and u2 is 0, the fluorine-containing ether compound having this linking group has excellent flexibility, and the state of coating of the fluorine-containing ether compound on the protective layer becomes more uniform. When only one of u1 and u2 is 0, the value of the non-zero one of u1 and u2 is 1 to 6, preferably 1 to 4, and more preferably 1 to 3. This is because the linking group does not become too rigid, and a lubricating layer having better adhesion and excellent spin-off resistance can be formed.

[0154] In addition, in formula (4-1), when only one of u1 and u2 is 0, there are u1 or u2 carbon atoms that are not bonded to either a polar group or an ether oxygen atom between the carbon atom bonded to the secondary hydroxyl group and the ether oxygen atoms that form the ether bonds at both ends. Therefore, excellent rigidity is achieved due to the methylene groups u1 or u2, and R ３ The polar group in the linking group represented by the formula (I) can prevent chemical substances in the environment from being attracted to the lubricating layer, and the resulting fluorine-containing ether compound can form a lubricating layer with even better chemical substance resistance.

[0155] The linking group represented by formula (4-2) has a glycerin structure (—O—CH ２ -CH(OH)-CH ２It has a structure in which 2 to 3 -O-) are linked together. The glycerin structure imparts flexibility to the linking group, so the linking group represented by formula (4-2) is extremely flexible. As a result, a fluorine-containing ether compound having this linking group has better adhesion and can form a lubricating layer with better spin-off resistance. In formula (4-2), v represents an integer of 1 to 2, preferably 1. Since v is 2 or less, the polarity of the fluorine-containing ether compound represented by formula (1) is kept low, and a lubricating layer with better chemical resistance can be formed.

[0156] The linking group represented by formula (4-3) has a structure in which carbon atoms bonded to hydroxyl groups are bonded directly to each other, or a structure in which carbon atoms are bonded via an alkylene group having 1 to 6 carbon atoms and not including an ether bond. Therefore, the linking group represented by formula (4-3) maintains low polarity compared to, for example, a linking group having a structure in which carbon atoms bonded to hydroxyl groups are bonded via an oxygen atom forming an ether bond and an alkylene group. As a result, the intrusion of chemical substances in the environment can be effectively inhibited, and a lubricating layer with high chemical resistance can be formed.

[0157] In formula (4-3), w represents an integer of 0 to 6. When w is 6 or less, the linking group represented by formula (4-3) does not become too rigid, resulting in a fluorine-containing ether compound that can form a lubricating layer having better adhesion and excellent spin-off resistance. It is preferable that w is 4 or less.

[0158] Furthermore, in formula (4-3), when w is 1 or greater, there are w carbon atoms between the two carbon atoms bonded to secondary hydroxyl groups that are not bonded to either a polar group or an ether oxygen atom. This results in a fluorine-containing ether compound that has excellent rigidity due to the w methylene groups and can form a lubricating layer with even better chemical resistance. When w is 1 or greater, it is preferable that w be 2 to 4.

[0159] The linking group represented by formula (4-4) has a structure in which carbon atoms bonded to hydroxyl groups are bonded via a linear linking chain of four or more atoms, including an oxygen atom forming an ether bond.The fluorine-containing ether compound having the linking group represented by formula (4-4) has a sufficient distance between the two hydroxyl groups in formula (4-4), so that the intramolecular interaction of the hydroxyl groups is suppressed, and a lubricating layer having good adsorption ability to the protective layer can be formed.Therefore, the lubricating layer containing the fluorine-containing ether compound having this linking group has better adhesion and is even more excellent in spin-off resistance.

[0160] In formula (4-4), x1 and x2 each independently represent an integer of 0 to 5, and at least one of x1 and x2 is an integer of 1 to 5. Since the total value of x1 and x2 in the linking group represented by formula (4-4) is 1 or more, the fluorine-containing ether compound becomes moderately rigid, and a lubricating layer containing the fluorine-containing ether compound is less likely to absorb chemicals in the environment and has good chemical resistance. It is preferable that x1 and x2 each independently represent an integer of 3 or less. This is because the linking group does not become too rigid, and a lubricating layer having better adhesion and excellent spin-off resistance can be formed. It is also preferable that the total value of x1 and x2 is 4 or less. In order to impart moderate flexibility to the linking group represented by formula (4-4), it is preferable that one of x1 and x2 is 0.

[0161] The linking group represented by formula (4-5) has three hydroxyl groups, and has a structure in which the carbon atoms bonded to adjacent hydroxyl groups are bonded via a linear linking chain of four or more atoms, each containing an oxygen atom forming an ether bond. Fluorine-containing ether compounds having a linking group represented by formula (4-5) have three hydroxyl groups, so that interactions between the hydroxyl groups and the protective layer are easily formed, and a lubricating layer with good adhesion to the protective layer can be formed. Furthermore, fluorine-containing ether compounds having a linking group represented by formula (4-5) have sufficient distance between adjacent hydroxyl groups of the three hydroxyl groups in formula (4-5), so that intramolecular interactions between the hydroxyl groups are suppressed, and a lubricating layer with good adsorption ability to the protective layer can be formed. Therefore, a lubricating layer containing a fluorine-containing ether compound having this linking group has better adhesion and is even more excellent in spin-off resistance.

[0162] In formula (4-5), y1 and y2 each independently represent an integer of 1 to 5. In the linking group represented by formula (4-5), y1 and y2 are both 1 or greater, so that the fluorine-containing ether compound becomes moderately rigid, and a lubricating layer containing this compound is less likely to absorb chemical substances in the environment and has good chemical resistance. In order to impart moderate flexibility to the linking group represented by formula (4-5), y1 and y2 are each preferably independently 1 to 3, and most preferably both are 1. Furthermore, it is preferable that y1 and y2 are the same, so that the coating state of the fluorine-containing ether compound on the protective layer becomes more uniform.

[0163] The linking group represented by formula (4-6) has a structure in which carbon atoms bonded to hydroxyl groups are bonded to each other via a linking chain of 7 or more atoms containing two ether bonds. In the linking group represented by formula (4-6), the distance between the two hydroxyl groups is sufficiently maintained, so that intramolecular interactions are suppressed. Therefore, the linking group represented by formula (4-6) has good adsorption ability to the protective layer. As a result, a fluorine-containing ether compound having a linking group represented by formula (4-6) can form a lubricating layer with better adhesion and excellent spin-off resistance.

[0164] In formula (4-6), z represents an integer of 1 to 6. In order to impart appropriate flexibility to the linking group represented by formula (4-6), z is preferably 4 or less. In addition, in order to impart sufficient rigidity to the linking group represented by formula (4-6), z is preferably 2 or more. ｃ and R ｄ each independently represents a hydrogen atom, a fluorine atom, or a methyl group. For ease of production, z (-CR ｃ R ｄ -) are -CH ２ -, -CH(CH ３ ) -, -C(CH ３ ) ２ -, -CF ２ - is preferable.

[0165] z (-CR ｃ R ｄ -) is one or more -CH ２ When it is only -, for example, -CH(CH ３ )- and / or -C(CH ３ ) ２ In comparison with the case where the linking group represented by formula (4-6) contains z (-CR ｃ R ｄ At least a portion of the -CH(CH ３ )- and / or -C(CH ３ ) ２ If - is included, z (-CR ｃ R ｄ -) are all -CH ２ In comparison with the case where z (-CR ｃ R ｄ -) is one or more -CF ２ When the linking group represented by formula (4-6) contains -, the surface free energy of the linking group is reduced, making it more difficult for chemical substances in the environment to be absorbed, which is preferable.

[0166] (R ２In 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 the formula (R) coats the surface of the protective layer and imparts lubricity to the lubricating layer, thereby reducing the frictional force between the magnetic head and the protective layer. ２ The PFPE chain represented by the formula (I) is appropriately selected depending on the performance required of the lubricant containing the fluorine-containing ether compound.

[0167] 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.

[0168] When x in formula (1) is 1 or 2, (x+1) R ２ may be the same in part or in whole, or may be different from each other. ２ are each independently preferably a PFPE chain represented by the following formula (5) derived from a polymer or copolymer of perfluoroalkylene oxide: -(CF ２ ) ｗ１ -O-(CF ２ O) ｗ２ -(CF ２ CF ２ O) ｗ３ -(CF ２ CF ２ CF ２ O) ｗ４ -(CF ２ CF ２ CF ２ CF ２ O) ｗ５ -(CF ２ ) ｗ６- (5) (In formula (5), w2, w3, w4, and w5 represent the average degree of polymerization, and each independently represents 0 to 20. However, w2, w3, w4, and w5 cannot all be 0 at the same time. w1 and w6 are CF ２ is an average value representing the number of repeating units in formula (5), each of which independently represents 1 to 3. ２ O), (CF ２ CF ２ O), (CF ２ CF ２ CF ２ O), (CF ２ CF ２ CF ２ CF ２ There are no particular restrictions on the arrangement order of O).

[0169] In formula (5), 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 (5), w1 and w6 represent CF ２ The values ​​of w1 and w6 are determined depending on the structure of the repeating units located at the ends of the chain structure in the PFPE chain represented by formula (5). ２ O), (CF ２ CF ２ O), (CF ２ CF ２ CF ２ O), (CF ２ CF ２ CF ２ CF ２ O) is a repeating unit. There is no particular limitation on the arrangement order of the repeating units in formula (5). There is also no particular limitation on the number of types of repeating units in formula (5).

[0170] R in formula (1) ２ are each independently any one selected from the PFPE chains represented by the following formulas (5-1) to (5-4): ２ -(OCF ２ CF ２ ) ｈ -(OCF ２ ) ｉ-OCF ２ - (5-1) (In formula (5-1), h and i represent the average degree of polymerization, 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 - (5-2) (In formula (5-2), 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 - (5-3) (In formula (5-3), 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 - (5-4) (In formula (5-4), 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

[0171] R ２ When R is any one selected from the PFPE chains represented by formulas (5-1) to (5-4), the resulting fluorine-containing ether compound can provide a lubricating layer with good lubricity. ２is any one selected from the PFPE chains represented by formulas (5-1) to (5-4), 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 on 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, R ２ A lubricating layer containing a fluorine-containing ether compound in which R is any one selected from the PFPE chains represented by formulas (5-1) to (5-4) is more dense and can further suppress spin-off, and is therefore preferred.

[0172] In formula (5-1), the repeating unit (OCF ２ CF ２ ) and (OCF ２ In formula (5-1), there is no particular limitation on the arrangement order of (OCF ２ CF ２ ) and the number h (OCF ２ The number i of (OCF ２ CF ２ The PFPE chain represented by formula (5-1) may be a polymer of (OCF ２ CF ２ ) and (OCF ２ ) may be any of a random copolymer, a block copolymer, and an alternating copolymer.

[0173] In formulas (5-1) to (5-3), 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, so that the fluorine-containing ether compound can provide a lubricating layer with good lubricity. Furthermore, in formulas (5-1) to (5-3), 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, so that the viscosity of the fluorine-containing ether compound does not become too high, and a lubricant containing the fluorine-containing ether compound is easily applied, which is preferable. 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, so that the fluorine-containing ether compound can easily wet and spread on the protective layer and provide a lubricating layer with a uniform thickness.

[0174] In formula (5-4), the repeating unit (CF ２ CF ２ CF ２ O) and (CF ２ CF ２ In formula (5-4), the order of the groups (CF) representing the average degree of polymerization is not particularly limited. ２ CF ２ CF ２ O) number w8 and (CF ２ CF ２ The number w9 of monomer units (CF ２ CF ２ CF ２ O) and (CF ２ CF ２ O) may be a random copolymer, a block copolymer, or an alternating copolymer.

[0175] In formula (5-4), w8 and w9, which represent the average degree of polymerization, are each independently 1 to 20, preferably 1 to 15, and more preferably 1 to 10. w7 and w10 in formula (5-4) are each independently 1 to 20, more preferably 1 to 15, and even more preferably 1 to 10. ２ 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 (5-4), etc.

[0176] Specifically, the fluorine-containing ether compound represented by formula (1) is preferably any one of the compounds represented by the following formulae (AA) to (AX), (BA) to (BP), (CA) to (CM), and (DA). When the compound represented by formula (1) is any one of the compounds represented by the following formulae (AA) to (AX), (BA) to (BP), (CA) to (CM), and (DA), the raw materials are easily available, and a lubricating layer that has better chemical resistance and can suppress spin-off can be formed even if the thickness is thin.

[0177] In the compounds represented by the following formulae (AA) to (AX), (BA) to (BP), (CA) to (CM), and (DA), Rf representing a PFPE chain １ , Rf ２ , Rf ３ are the following structures. That is, in the compounds represented by the following formulae (AA), (AD) to (AI), (AK) to (AN), (AP), (AR), (AX), (BA), (BE), (BN) to (BP), (CA) to (CI), (CL), and (CM), Rf １ is a PFPE chain represented by the above formula (5-1). In the compounds represented by the following formulae (AB), (AJ), (AO), (AQ), (AS) to (AW), (BB) to (BD), (BF) to (BM), (CJ), and (DA), Rf ２ is a PFPE chain represented by the above formula (5-2). In the compounds represented by the following formulas (AC) and (CK), Rf ３ is a PFPE chain represented by the above formula (5-3). Rf １ h and i in Rf ２ j and Rf in ３ Since k in the above formula is a value indicating the average degree of polymerization, it is not necessarily an integer.

[0178]

[0179] In the compounds represented by the following formulas (AA) to (BM) and (DA), x in formula (1) is 0. In the compounds represented by formulas (AA) to (AX), R １ and R ４The compounds represented by formulas (AA) to (AH) are １ and R ４ is the terminal group represented by the above formula (2-1). The compounds represented by the following formulae (AI) to (AM) are １ and R ４ is the terminal group represented by the above formula (2-2).

[0180] The compounds represented by the following formulas (AN) to (AR) are R １ and R ４ is the terminal group represented by the above formula (2-3). The compounds represented by the following formulas (AS) to (AV) are １ and R ４ is the terminal group represented by the above formula (2-4). The compound represented by the following formula (AW) is １ and R ４ is the terminal group represented by the above formula (2-5). The compound represented by the following formula (AX) is １ and R ４ is the terminal group represented by the above formula (2), and A is an organic group having 3 carbon atoms and containing one ether oxygen atom.

[0181] The compounds represented by the following formulas (BA) to (BC) are R １ and R ４ are different from one another and are terminal groups represented by any one of the above formulas (2-1) to (2-3). The compounds represented by the following formulas (BD) to (BL) can be １ and R ４ are different, one is a terminal group represented by any one of the above formulas (2-1) to (2-2), and the other is a terminal group represented by any one of the above formulas (3-1) to (3-2). １ and R ４ are different, one is a terminal group represented by the above formula (2-2), and the other is a terminal group represented by the above formula (3-4).

[0182] The compounds represented by the following formulas (BN) and (BO) are R １ and R ４are different, one is an end group represented by the above formula (2-1), and the other is an end group represented by the above formula (3-3). The compound represented by formula (BN) is a compound in which one of the five E's in formula (3-3) is a carboxamide group (-C(=O)NH ２ In the compound represented by formula (BO), one of the five E's in formula (3-3) is a methoxy group. In the compound represented by formula (BP) below, １ and R ４ One is a terminal group represented by the above formula (2-1), and the other is a terminal group represented by the above formula (3-5), which contains a perfluoroalkylene chain having 2 carbon atoms.

[0183] The compounds represented by the following formulas (CA) to (CK) are compounds in which x in formula (1) is 1 and R １ and R ４ The compounds represented by formulas (CA) to (CE) are １ and R ４ is a terminal group represented by any one of the above formulas (2-1) to (2-5). ３ is a linking group represented by the above formula (4-1). The compounds represented by the following formulae (CF) to (CI) can be １ and R ４ is the terminal group represented by the above formula (2-1). ３ is a linking group represented by any one of the above formulas (4-2) to (4-5).

[0184] The compounds represented by the following formulas (CJ) and (CK) are １ and R ４ is the terminal group represented by the above formula (2-1). ３ is a linking group represented by the above formula (4-1). In the compound represented by the following formula (CL), x in formula (1) is 2. R １ and R ４ are the same and are the terminal groups represented by the above formula (2-1). ３ is a linking group represented by the above formula (4-1). In the compound represented by the following formula (CM), x in formula (1) is 1. R １ and R ４ are the same and are the terminal groups represented by the above formula (2-1). ３is the linking group represented by the above formula (4-6).

[0185] In the compound represented by the following formula (DA), x in formula (1) is 0. １ and R ４ are different, one is a terminal group represented by the above formula (2-6), and the other is a terminal group represented by the above formula (3-2).

[0186] (Rf in formula (AA) １ In the formula (AB), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. ２ In the formula (AC), j represents the average degree of polymerization, and represents 1 to 15. ３ In the formula (AD), k represents the average degree of polymerization and represents 1 to 10. １ In the formula (AE), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. １ In the formula, h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20.

[0187] (Rf in formula (AF) １ In the formula (AG), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. １ In the formula (AH), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. １ In the formula (AI), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. １ In the formula (AJ), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. ２ In the formula, j represents the average degree of polymerization and is a number ranging from 1 to 15.

[0188] (Rf in formula (AK) １ In the formula (AL), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. １In the formula (AM), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. １ In the formula (AN), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. １ In the formula (AO), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. ２ In the formula, j represents the average degree of polymerization and is a number ranging from 1 to 15.

[0189] (Rf in formula (AP) １ In the formula (AQ), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. ２ In the formula (AR), j represents the average degree of polymerization, and represents 1 to 15. １ In the formula (AS), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. ２ In the formula (AT), j represents the average degree of polymerization, and represents 1 to 15. ２ In the formula, j represents the average degree of polymerization and is a number ranging from 1 to 15.

[0190] (Rf in formula (AU) ２ In the formula (AV), j represents the average degree of polymerization, and represents 1 to 15. ２ In the formula (AW), j represents the average degree of polymerization, and represents 1 to 15. ２ In the formula (AX), j represents the average degree of polymerization, which is 1 to 15. １ In the formula, h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20.

[0191] (Rf in formula (BA) １ In the formula (BB), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. ２ In the formula (BC), j represents the average degree of polymerization, and represents 1 to 15. ２ In the formula (BD), j represents the average degree of polymerization, which is 1 to 15. ２In the formula (BE), j represents the average degree of polymerization, and represents 1 to 15. １ In the formula (BF), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. ２ In the formula, j represents the average degree of polymerization and is a number ranging from 1 to 15.

[0192] (Rf in formula (BG) ２ In the formula (BH), j represents the average degree of polymerization, and represents 1 to 15. ２ In the formula (BI), j represents the average degree of polymerization, and represents 1 to 15. ２ In the formula (BJ), j represents the average degree of polymerization, and represents 1 to 15. ２ In the formula (BK), j represents the average degree of polymerization, which is 1 to 15. ２ In the formula (BL), j represents the average degree of polymerization, which is 1 to 15. ２ In the formula (BM), j represents the average degree of polymerization, and represents 1 to 15. ２ In the formula, j represents the average degree of polymerization and is a number ranging from 1 to 15.

[0193] (Rf in formula (BN) １ In the formula (BO), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. １ In the formula (BP), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. １ In the formula, h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20.

[0194] (Two Rf in formula (CA) １ In the formula, h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. １ In the formula (CB), h and i may be the same or different. １ In the formula, h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. １In the formula (CC), h and i may be the same or different. １ In the formula, h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. １ In the formula (CD), h and i may be the same or different. １ In the formula, h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. １ In the formula (CE), h and i may be the same or different. １ In the formula, h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. １ In the formula, h and i may be the same or different.

[0195] (Two Rf in formula (CF) １ In the formula, h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. １ In the formula (CG), h and i may be the same or different. １ In the formula, h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. １ In the formula (CH), h and i may be the same or different. １ In the formula, h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. １ In the formula (CI), h and i may be the same or different. １ In the formula, h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. １ In the formula, h and i may be the same or different.

[0196] (Two Rf in formula (CJ) ２ In the formula, j represents the average degree of polymerization, which is 1 to 15. ２In the formula (CK), j may be the same or different. ３ In the formula, k represents the average degree of polymerization and represents 1 to 10. ３ In formula (CL), k may be the same or different. １ In the formula, h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. １ In the formula (CM), h and i may be different from each other, or some or all of them may be the same. １ In the formula, h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. １ In the formula, h and i may be the same or different.

[0197] (DA) (Rf in formula (DA) ２ In the formula, j represents the average degree of polymerization and is a number ranging from 1 to 15.

[0198] 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.

[0199] The number average molecular weight (Mn) of the fluorine-containing ether compound was measured by AVANCEIII400 manufactured by Bruker Biospin. １ H-NMR and １９ This is a value measured by F-NMR. １９The number of repeating units of the PFPE chain is calculated from the integrated value measured by F-NMR to determine the number average molecular weight. In the NMR (nuclear magnetic resonance) measurement, 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.

[0200] The fluorine-containing ether compound of this embodiment is preferably subjected to molecular weight fractionation by an appropriate method to make the molecular weight dispersity (ratio of weight average molecular weight (Mw) / number average molecular weight (Mn)) 1.3 or less. In this embodiment, the method for molecular weight fractionation is not particularly limited, and for example, molecular weight fractionation by silica gel column chromatography, gel permeation chromatography (GPC), or the like, molecular weight fractionation by supercritical extraction, or the like can be used.

[0201] "Production Method" The production method of the fluorinated ether compound of this embodiment is not particularly limited, and the compound can be produced using a conventionally known production method. The fluorinated ether compound of this embodiment can be produced, for example, using the production method shown below.

[0202] [First Production Method (x is 0, R １ and R ４ In formula (1), x is 0, and R １ and R ４ To prepare a compound in which R ２ At both ends of the perfluoropolyether chain corresponding to ２ A fluorine-based compound in which a hydroxyl group (OH) is arranged is prepared.

[0203] Next, the hydroxyl groups of the hydroxymethyl groups located at both ends of the fluorine-based compound and the R １ A group corresponding to (=R ４ The epoxy group of the epoxy compound having the group corresponding to R ２At both ends of the perfluoropolyether chain corresponding to １ A group corresponding to (=R ４ A compound having a group corresponding to

[0204] R in formula (1) １ A group corresponding to (=R ４ The epoxy compound having the terminal group represented by formula (6-1), (6-2), (6-4) to (6-7), and (6-17) can be used. In formulas (6-1), (6-2), (6-4) to (6-7), and (6-17), THP represents a tetrahydropyranyl group.

[0205]

[0206] A fluorine-based compound and R in formula (1) １ (=R ４ When reacting with an epoxy compound having a group corresponding to the above group, the hydroxyl group of the epoxy compound may be protected with an appropriate protecting group before reacting with the fluorine-based compound.

[0207] The epoxy compound can be produced, for example, by reacting an alcohol compound in which a hydroxyl group not participating in the reaction may be appropriately protected with a halogen compound having an epoxy group. Specifically, for example, the epoxy compound represented by formula (6-3) can be produced by reacting an alcohol compound in which a hydroxyl group not participating in the reaction may be appropriately protected with epibromohydrin represented by formula (8-1), as shown in the following formula (7-1).

[0208]

[0209] Alternatively, the epoxy compound may be produced, for example, by a method in which the vinyl group of a compound having a terminal vinyl group and an optionally appropriately protected hydroxyl group is reacted with m-chloroperbenzoic acid (mCPBA) to oxidize the vinyl group. Specifically, for example, the epoxy compound represented by formula (6-4) can be produced by a method in which the vinyl group of a compound having a terminal vinyl group and an optionally appropriately protected hydroxyl group is reacted with m-chloroperbenzoic acid (mCPBA), as shown in the following formula (7-2). In formula (7-2), THP represents a tetrahydropyranyl group.

[0210]

[0211] R in formula (1) １ (=R ４ The epoxy compound having a group corresponding to formula (1), x=0 and R １ and R ４ A compound in which

[0212] [Second Production Method (x is 0 and R １ and R ４ In formula (1), x is 0, and R １ and R ４ In order to produce a compound different from R in formula (1), first, as in the first production method, ２ At both ends of the perfluoropolyether chain corresponding to ２ A fluorine-based compound in which a hydroxyl group (OH) is arranged is prepared.

[0213] Next, the hydroxyl group of the hydroxymethyl group located at one end of the fluorine-based compound and the R １ The epoxy group of an epoxy compound having a group corresponding to R ２ At one end of the perfluoropolyether chain corresponding to １ (First reaction) is then performed to obtain an intermediate compound 1 having a group corresponding to R in formula (1). ４(second reaction)

[0214] R １ and R ４ and (6-15) are different, one of which is an end group represented by formula (2) and the other is an end group not corresponding to formula (2), the epoxy compound corresponding to the end group represented by formula (2) can be the compounds represented by the above formulas (6-1) to (6-7) and (6-17). Furthermore, the epoxy compound corresponding to the end group not corresponding to formula (2) can be, for example, the epoxy compounds represented by the following formulas (6-8) to (6-16). In formulas (6-8), (6-10), (6-14) and (6-15), THP represents a tetrahydropyranyl group.

[0215]

[0216] By carrying out the above steps, a compound represented by the formula (1) in which x is 0 and R １ and R ４ A compound different from the above is obtained.

[0217] [Third Production Method (x is 1 and R １ and R ４ are the same, and the two R ２ are the same)] R in formula (1) ２ At both ends of the perfluoropolyether chain corresponding to ２ A fluorine-based compound in which a hydroxyl group (OH) is arranged is prepared.

[0218] Next, the hydroxyl group of the hydroxymethyl group located at one end of the fluorine-based compound and the R １ A group corresponding to (=R ４ The epoxy compound having the group corresponding to R ２ At one end of the perfluoropolyether chain corresponding to １ A group corresponding to (=R ４ An intermediate compound 1 having a group corresponding to

[0219] When the fluorine-based compound is reacted with the epoxy compound, the hydroxyl group of the epoxy compound may be protected with an appropriate protecting group before the reaction with the fluorine-based compound.

[0220] 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 and a halogen atom bonded to the other end of the moiety corresponding to R ３ and a compound having epoxy groups at both ends of the moiety corresponding to (second reaction).

[0221] R in formula (1) ３ As a compound having an epoxy group at one end of a moiety corresponding to the formula (1) and a halogen atom bonded to the other end, for example, compounds represented by the following formulas (8-1) and (8-2) can be used. ３ Examples of compounds having epoxy groups at both ends of a moiety corresponding to the above include compounds represented by the following formulas (8-4) to (8-11): THP in the following formula (8-7) represents a tetrahydropyranyl group.

[0222]

[0223] The compound having epoxy groups at both ends can be produced, for example, by the following method. ３ With a twice-fold molar amount of epibromohydrin, a diol corresponding to a part of the linking group represented by formula (8-8) can be produced by reacting 1,4-butanediol with a twice-fold molar amount of epibromohydrin represented by formula (8-1), as shown in formula (9-1) below.

[0224]

[0225] The compound having epoxy groups at both ends may be produced by the following method. ３ and a halogen compound having an epoxy group corresponding to a part of the linking group represented by R３ and an alcohol having an alkenyl group corresponding to a portion of the linking group represented by the formula (I). At this time, 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 reacted with m-chloroperbenzoic acid (mCPBA) to oxidize it, 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.

[0226] For example, the compound represented by formula (8-7) can be produced by an addition reaction of epibromohydrin represented by formula (8-1) 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 (9-2) below. THP in formula (9-2) below represents a tetrahydropyranyl group.

[0227]

[0228] When the compound obtained after the second reaction has a hydroxyl group protected with a protecting group, a deprotection reaction is carried out using a known method. By carrying out the above steps, a compound in which x in formula (1) is 1 and R １ and R ４ are the same, and the two R ２ It is possible to produce a fluorine-containing ether compound having the same

[0229] [Fourth Production Method (where x is 1 and R １ and R ４ and / or two R ２ are different)] First, R １ Side R ２ A hydroxyl group at one end of a perfluoropolyether chain of a fluorine-based compound having a hydroxymethyl group at each end of the chain, and a １ An intermediate compound 1a is obtained by reacting an epoxy compound having a group corresponding to the following (first reaction).

[0230] Next, R４ Side R ２ A hydroxyl group at one end of a perfluoropolyether chain of a fluorine-based compound having a hydroxymethyl group at each end of the chain, and a ４ In the fourth production method, an epoxy compound having a group corresponding to R １ and R ４ and are the same (i.e., R １ and R ４ are the same terminal groups represented by formula (2), ４ As an epoxy compound having a group corresponding to the terminal group represented by formula (2), R １ The same compound as the epoxy compound having a group corresponding to the formula:

[0231] In the fourth manufacturing method, R １ and R ４ Unlike R １ and R ４ In the case of producing a fluorine-containing ether compound in which all of R ４ As an epoxy compound having a group corresponding to the above formula (2), for example, an epoxy compound corresponding to the terminal group represented by R １ Compounds other than epoxy compounds having groups corresponding to

[0232] In the fourth manufacturing method, R １ and R ４ Unlike R １ is a terminal group represented by formula (2), and R ４ is a terminal group that does not correspond to formula (2) (R １ and R ４ In the case of producing a fluorine-containing ether compound in which only one of R ４ As the epoxy compound having a group corresponding to the formula (1), an epoxy compound corresponding to the terminal group not corresponding to the formula (2) is used.

[0233] Next, the intermediate compound 1a obtained in the first reaction and the above-mentioned R ３a compound having an epoxy group at one end of a moiety corresponding to R and a halogen atom bonded to the other end, ３ The compound having epoxy groups at both ends of the portion corresponding to R １ Side R ２ At one end of the perfluoropolyether chain corresponding to １ and at the other end R ３ An intermediate compound 2a having an epoxy group corresponding to the following formula (third reaction) is prepared.

[0234] In the third reaction, R ３ a compound having an epoxy group at one end of a moiety corresponding to R and a halogen atom bonded to the other end, ３ In place of a compound having epoxy groups at both ends of a portion corresponding to R ３ and an alkenyl group bonded to the other end of the moiety corresponding to the compound (1), and oxidizing the double bond of the resulting compound to produce intermediate compound 2a having an epoxy group. Subsequently, intermediate compound 1b obtained in the second reaction is reacted with intermediate compound 2a obtained in the third reaction (fourth reaction).

[0235] When the compound obtained after the fourth reaction has a hydroxyl group protected with a protecting group, a deprotection reaction is carried out using a known method. By carrying out the above steps, a compound represented by the formula (1) in which x is 1 and R １ and R ４ and / or two R ２ It is possible to produce fluorine-containing ether compounds having different

[0236] [Fifth Production Method (where x is 2 and R １ and R ４ are the same, and the two R ３ are the same, and R １ Side R ２ and R ４ Side R ２ are the same)] R in formula (1) １ Side R ２ (=R ４ Side R ２) at both ends of the perfluoropolyether chain corresponding to ２ A fluorine-based compound in which a hydroxyl group (OH) is arranged is prepared.

[0237] Next, the hydroxyl group of the hydroxymethyl group located at one end of the fluorine-based compound and the R １ A group corresponding to (=R ４ The epoxy compound having the group corresponding to R １ Side R ２ (=R ４ Side R ２ ) at one end of the perfluoropolyether chain corresponding to １ A group corresponding to (=R ４ An intermediate compound 1 having a group corresponding to

[0238] Next, R at the center of the molecule in formula (1) ２ At both ends of the perfluoropolyether chain corresponding to ２ Then, a fluorine-based compound having the hydroxyl groups of the hydroxymethyl groups located at both ends of the fluorine-based compound and the R ３ a compound having an epoxy group at one end of a moiety corresponding to R and a halogen atom bonded to the other end, ３ This allows the R ２ R is attached to both ends of the perfluoropolyether chain corresponding to ３ An intermediate compound 3a having an epoxy group corresponding to the formula (second reaction) is obtained.

[0239] In the second reaction, R ３ a compound having an epoxy group at one end of a moiety corresponding to R and a halogen atom bonded to the other end, ３ In place of a compound having epoxy groups at both ends of a portion corresponding to R ３and an alkenyl group bonded to the other end of the compound, and the double bond of the resulting compound is oxidized to produce intermediate compound 3a having epoxy groups at both ends. Thereafter, the hydroxyl group of the hydroxymethyl group at one end of intermediate compound 1 obtained in the first reaction is reacted with the epoxy groups at both ends of intermediate compound 3a (third reaction).

[0240] When the compound obtained after the third reaction has a hydroxyl group protected with a protecting group, a deprotection reaction is carried out using a known method. By carrying out the above steps, a compound represented by the formula (1) in which x is 2 and R １ and R ４ are the same, and the two R ３ are the same, and R １ Side R ２ and R ４ Side R ２ It is possible to produce a fluorine-containing ether compound having the same

[0241] [Sixth Production Method (where x is 2 and R １ Side R ３ and R ４ Side R ３ and R １ and R ４ and / or R １ Side R ２ and R ４ Side R ２ In the first reaction of the fifth production method, instead of producing intermediate compound 1, intermediate compound 1a and intermediate compound 1b are produced by carrying out the first and second reactions of the fourth production method. Then, intermediate compound 3a is obtained in the same manner as in the second reaction of the fifth production method. Then, intermediate compound 1a and intermediate compound 1b are sequentially reacted with the epoxy groups located at both ends of intermediate compound 3a, respectively.

[0242] When the compound obtained after the above steps has a hydroxyl group protected with a protecting group, a deprotection reaction is carried out using a known method. By carrying out the above steps, a compound represented by the formula (1) in which x is 2 and R １ Side R ３and R ４ Side R ３ and R １ and R ４ and / or R １ Side R ２ and R ４ Side R ２ It is possible to produce fluorine-containing ether compounds having different

[0243] [Seventh Production Method (where x is 2 and R １ Side R ３ and R ４ Side R ３ Unlike R １ and R ４ and R １ Side R ２ and R ４ Side R ２ In the second reaction of the fifth production method, R ２ At both ends of the perfluoropolyether chain corresponding to ２ fluorine-based compound in which the R ３ a compound having an epoxy group at one end of a moiety corresponding to R and a halogen atom bonded to the other end, ３ R is selected from compounds having epoxy groups at both ends of a moiety corresponding to １ Side R ３ The compound is reacted with any one of the compounds having a moiety corresponding to

[0244] The resulting compound and the above-mentioned R ３ a compound having an epoxy group at one end of a moiety corresponding to R and a halogen atom bonded to the other end, ３ R is selected from compounds having epoxy groups at both ends of a moiety corresponding to ４ Side R ３ to obtain intermediate compound 3b. Thereafter, the third reaction is carried out in the same manner as in the fifth production method, except that intermediate compound 3b is used instead of intermediate compound 3a.

[0245] When the compound obtained after the third reaction has a hydroxyl group protected with a protecting group, a deprotection reaction is carried out using a known method. By carrying out the above steps, a compound represented by the formula (1) in which x is 2 and R １ Side R ３ and R ４ Side R ３ Unlike R １ and R ４ and R １ Side R ２ and R ４ Side R ２ It is possible to produce a fluorine-containing ether compound having the same

[0246] In formula (1), x is 2, and R ２ The perfluoropolyether chain corresponding to R １ Side R ２ and / or R ４ Side R ２ and different fluorine-containing ether compounds are those having the same R at the center of the molecule as used in the fifth to seventh production methods described above. ２ The polyfluoroethylene copolymer can be produced by appropriately selecting the type of fluorine-based compound having a perfluoropolyether chain corresponding to the above formula.

[0247] Therefore, in the fifth to seventh production methods for producing a fluorinated ether compound in which x is 2 in the formula (1), R ２ The fluorine-based compound having a perfluoropolyether chain corresponding to the other R ２ The compound may be the same as or different from the corresponding fluorine-based compound having a perfluoropolyether chain.

[0248] [Lubricant for magnetic recording media] The lubricant for magnetic recording media of this embodiment contains a fluorine-containing ether compound represented by the above formula (1). The lubricant of this embodiment can be used by mixing, as needed, with known materials used as lubricant materials, as long as the properties resulting from the inclusion of the fluorine-containing ether compound represented by the above formula (1) are not impaired.

[0249] Specific examples of known materials include FOMBLIN (registered trademark) ZDIAC, FOMBLIN ZDEAL, FOMBLIN AM-2001 (all manufactured by Solvay Solexis), Moresco A20H (manufactured by Moresco), etc. The known material to be mixed with the lubricant of this embodiment preferably has a number average molecular weight of 1,000 to 10,000.

[0250] 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% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

[0251] The lubricant of this embodiment contains the fluorine-containing ether compound represented by the above formula (1), and therefore can form a lubricating layer that has excellent chemical resistance and can suppress spin-off.

[0252] [Magnetic Recording Medium] The magnetic recording medium of this embodiment has at least a magnetic layer, a protective layer, and a lubricating layer sequentially provided on a substrate. In the magnetic recording medium of this embodiment, one or more underlayers can be provided between the substrate and the magnetic layer as needed. In addition, at least one of an adhesive layer and a soft magnetic layer can be provided between the underlayer and the substrate.

[0253] 1 is a schematic cross-sectional view showing one embodiment of a magnetic recording medium of the present invention. The magnetic recording medium 10 of this embodiment has a structure in which an adhesive layer 12, a soft magnetic layer 13, a first underlayer 14, a second underlayer 15, a magnetic layer 16, a protective layer 17, and a lubricating layer 18 are sequentially provided on a substrate 11.

[0254] "Substrate" The substrate 11 may be, for example, a non-magnetic substrate in which a film made of NiP or a NiP alloy is formed on a base made of a metal or alloy material such as Al or an Al alloy. Alternatively, the substrate 11 may be a non-magnetic substrate made of a non-metallic material such as glass, ceramics, silicon, silicon carbide, carbon, or resin, or a non-magnetic substrate in which a film of NiP or a NiP alloy is formed on a base made of such a non-metallic material.

[0255] "Adhesion Layer" The adhesion layer 12 prevents the progress of corrosion of the substrate 11, which occurs when the substrate 11 and the soft magnetic layer 13 provided on the adhesion layer 12 are disposed in contact with each other. The material of the adhesion layer 12 can be appropriately selected from, for example, Cr, Cr alloy, Ti, Ti alloy, CrTi, NiAl, AlRu alloy, etc. The adhesion layer 12 can be formed by, for example, a sputtering method.

[0256] "Soft Magnetic Layer" The soft magnetic layer 13 preferably has a structure in which a first soft magnetic film, an intermediate layer made of a Ru film, and a second soft magnetic film are laminated in this order. That is, the soft magnetic layer 13 preferably has a structure in which the intermediate layer made of a Ru film is sandwiched between two soft magnetic films, and the soft magnetic films above and below the intermediate layer are anti-ferro-coupling (AFC).

[0257] Examples of materials for the first and second soft magnetic films include CoZrTa alloys and CoFe alloys. It is preferable to add Zr, Ta, or Nb to the CoFe alloy used for the first and second soft magnetic films. This promotes the amorphization of the first and second soft magnetic films. As a result, it is possible to improve the orientation of the first underlayer (seed layer) and reduce the flying height of the magnetic head. The soft magnetic layer 13 can be formed, for example, by sputtering.

[0258] "First Underlayer" The first underlayer 14 is a layer that controls the orientation and crystal size of the second underlayer 15 and magnetic layer 16 that are provided thereon. Examples of the first underlayer 14 include a Cr layer, a Ta layer, a Ru layer, or a CrMo alloy layer, a CoW alloy layer, a CrW alloy layer, a CrV alloy layer, and a CrTi alloy layer. The first underlayer 14 can be formed by, for example, a sputtering method.

[0259] "Second Underlayer" The second underlayer 15 is a layer that controls the orientation of the magnetic layer 16 so that it is favorable. The second underlayer 15 is preferably a layer made of Ru or a Ru alloy. The second underlayer 15 may be a layer consisting of a single layer, or may be made of multiple layers. When the second underlayer 15 consists of multiple layers, all of the layers may be made of the same material, or at least one layer may be made of a different material. The second underlayer 15 can be formed, for example, by a sputtering method.

[0260] "Magnetic Layer" The magnetic layer 16 is made of a magnetic film whose axis of easy magnetization is oriented perpendicular or horizontal to the substrate surface. The magnetic layer 16 is a layer containing Co and Pt. To improve the SNR characteristics, the magnetic layer 16 may be a layer containing oxides, Cr, B, Cu, Ta, Zr, etc. Examples of oxides contained in the magnetic layer 16 include SiO ２ , SiO, Cr ２ O ３ , CoO, Ta ２ O ３ , TiO ２ etc.

[0261] The magnetic layer 16 may be composed of a single layer, or may be composed of multiple magnetic layers made of materials with different compositions. For example, when the magnetic layer 16 is composed of three layers, a first magnetic layer, a second magnetic layer, and a third magnetic layer stacked in this order from the bottom, the first magnetic layer preferably has a granular structure made of a material containing Co, Cr, and Pt and further containing an oxide. As the oxide contained in the first magnetic layer, it is preferable to use an oxide of, for example, Cr, Si, Ta, Al, Ti, Mg, Co, or the like. Among them, TiO is particularly preferable. ２ , Cr ２ O３ , SiO ２ The first magnetic layer is preferably made of a composite oxide containing two or more kinds of oxides. ２ O ３ -SiO ２ , Cr ２ O ３ -TiO ２ , SiO ２ -TiO ２ The first magnetic layer may contain, in addition to Co, Cr, Pt, and oxides, one or more elements selected from B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb, Ru, and Re.

[0262] The second magnetic layer can be made of the same material as the first magnetic layer. The second magnetic layer preferably has a granular structure. The third magnetic layer preferably has a non-granular structure made of a material containing Co, Cr, and Pt and not containing oxides. In addition to Co, Cr, and Pt, the third magnetic layer can contain one or more elements selected from B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb, Ru, Re, and Mn.

[0263] When the magnetic layer 16 is formed of multiple magnetic layers, it is preferable to provide a non-magnetic layer between adjacent magnetic layers. When the magnetic layer 16 is formed of three layers, namely, a first magnetic layer, a second magnetic layer, and a third magnetic layer, it is preferable to provide a non-magnetic layer between the first magnetic layer and the second magnetic layer and between the second magnetic layer and the third magnetic layer.

[0264] The non-magnetic layer provided between adjacent magnetic layers of the magnetic layer 16 can be suitably made of, for example, Ru, a Ru alloy, a CoCr alloy, or a CoCrX1 alloy (X1 represents one or more elements selected from Pt, Ta, Zr, Re, Ru, Cu, Nb, Ni, Mn, Ge, Si, O, N, W, Mo, Ti, V, and B).

[0265] The non-magnetic layer provided between adjacent magnetic layers of the magnetic layer 16 is preferably made of an alloy material containing an oxide, a metal nitride, or a metal carbide. Specifically, the oxide may be, for example, SiO ２ , Al２ O ３ , Ta ２ O ５ , Cr ２ O ３ , MgO, Y ２ O ３ , TiO ２ Examples of metal nitrides that can be used include AlN and Si. ３ N ４ , TaN, CrN, etc. can be used as the metal carbide. TaC, BC, SiC, etc. can be used as the metal carbide. The non-magnetic layer can be formed by, for example, sputtering.

[0266] To achieve higher recording density, the magnetic layer 16 is preferably a magnetic layer for perpendicular magnetic recording, in which the axis of easy magnetization is oriented perpendicular to the substrate surface. The magnetic layer 16 may also be a magnetic layer for in-plane magnetic recording. The magnetic layer 16 may be formed by any conventionally known method, such as vapor deposition, ion beam sputtering, or magnetron sputtering. The magnetic layer 16 is usually formed by sputtering.

[0267] "Protective Layer" The protective layer 17 protects the magnetic layer 16. The protective layer 17 may be composed of a single 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.

[0268] The adhesion between the carbon-based protective layer and the lubricating layer 18 can be controlled by using hydrogenated carbon and / or nitrogenated carbon for the carbon-based protective layer and adjusting the hydrogen and / or nitrogen contents in the carbon-based protective layer. The hydrogen content in the carbon-based protective layer is preferably 3 atomic % to 20 atomic % as measured by hydrogen forward scattering (HFS). The nitrogen content in the carbon-based protective layer is preferably 4 atomic % to 15 atomic % as measured by X-ray photoelectron spectroscopy (XPS).

[0269] The hydrogen and / or nitrogen contained in the carbon-based protective layer does not need to be uniformly contained throughout the carbon-based protective layer. The carbon-based protective layer is preferably a compositionally graded layer, for example, in which nitrogen is contained on the lubricating layer 18 side of the protective layer 17 and hydrogen is contained on the magnetic layer 16 side of the protective layer 17. In this case, the adhesion between the magnetic layer 16 and the lubricating layer 18 and the carbon-based protective layer is further improved.

[0270] 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.

[0271] The protective layer 17 can be formed by sputtering using a target material containing carbon, chemical vapor deposition (CVD) using a hydrocarbon raw material such as ethylene or toluene, ion beam deposition (IBD), or the like. When a carbon-based protective layer is formed as the protective layer 17, it can be formed by DC magnetron sputtering, for example. In particular, when a carbon-based protective layer is formed as the protective layer 17, it is preferable to form an amorphous carbon protective layer by plasma CVD. An amorphous carbon protective layer formed by plasma CVD has a uniform surface with little roughness.

[0272] "Lubricant Layer" The lubricant layer 18 prevents contamination of the magnetic recording medium 10. The lubricant layer 18 also reduces the frictional force of the magnetic head of the magnetic recording and reproducing device sliding on the magnetic recording medium 10, thereby improving the durability of the magnetic recording medium 10. As shown in FIG. 1 , the lubricant layer 18 is formed on and in contact with the protective layer 17. The lubricant layer 18 is formed by applying the magnetic recording medium lubricant of the above-mentioned embodiment onto the protective layer 17. Therefore, the lubricant layer 18 contains the above-mentioned fluorine-containing ether compound.

[0273] 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.

[0274] 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. This allows the lubricating layer 18 to cover the surface of the protective layer 17 with a high coverage. Furthermore, by setting the average thickness of the lubricating layer 18 to 2.0 nm or less, the lubricating layer 18 can be made sufficiently thin, and the flying height of the magnetic head can be sufficiently reduced.

[0275] "Method for forming lubricating layer" As a method for forming the lubricating layer 18, for example, a method is given in which a magnetic recording medium in the middle of manufacture in which each layer up to the protective layer 17 is formed on the substrate 11, and a solution for forming a lubricating layer is applied to the protective layer 17 and dried.

[0276] The lubricant layer-forming solution can be obtained by dispersing and dissolving the magnetic recording medium lubricant of the above-described embodiment in a solvent as needed, and adjusting the viscosity and concentration to suit the coating method. Examples of solvents used in the lubricant layer-forming solution include fluorine-based solvents such as Vertrel (registered trademark) XF (trade name, manufactured by DuPont-Mitsui Fluorochemicals Co., Ltd.) and Asahiklin (registered trademark) AE-3000 (trade name, manufactured by AGC).

[0277] The method for applying the lubricant layer-forming solution is not particularly limited, and examples thereof include spin coating, spraying, paper coating, and dipping. When using the dipping method, the following method can be used, for example. First, the substrate 11 on which each layer up to the protective layer 17 has been formed is immersed in the lubricant layer-forming solution placed in the immersion tank of a dip coating device. Next, the substrate 11 is pulled out of the immersion tank at a predetermined speed. In this way, the lubricant layer-forming solution is applied to the surface of the protective layer 17 of the substrate 11. By using the dipping method, the lubricant layer-forming solution can be applied uniformly to the surface of the protective layer 17, and the lubricant layer 18 can be formed on the protective layer 17 with a uniform film thickness.

[0278] In this embodiment, it is preferable to subject the substrate 11 on which the lubricating layer 18 is formed to a heat treatment. By subjecting the substrate 11 to a heat treatment, the adhesion between the lubricating layer 18 and the protective layer 17 is improved, and the adhesive strength 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. A heat treatment temperature of 100°C or higher sufficiently improves the adhesion between the lubricating layer 18 and the protective layer 17. 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.

[0279] In this embodiment, in order to further improve the adhesion of the lubricating layer 18 to the protective layer 17, the lubricating layer 18 may be irradiated with ultraviolet (UV) rays before or after the heat treatment.

[0280] The magnetic recording medium 10 of this embodiment has at least a magnetic layer 16, a protective layer 17, and a lubricating layer 18 sequentially formed on a substrate 11. In the magnetic recording medium 10 of this embodiment, a lubricating layer 18 containing the above-mentioned fluorine-containing ether compound is formed on and in contact with the protective layer 17. This lubricating layer 18 has good chemical resistance and can suppress spin-off, even when thin. Therefore, the magnetic recording medium 10 of this embodiment has excellent reliability 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 LUL (Load Unload) type magnetic disk device.

[0281] 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.

[0282] [Example 1] The compound represented by the above formula (AA) was obtained by the following method. ２ CF ２O (CF ２ CF ２ O) ｈ (CF ２ O) ｉ CF ２ CH ２ 5 g of a compound (number average molecular weight: 750, molecular weight distribution: 1.1) represented by formula (6-1), 4.2 g of the compound represented by formula (6-1), and 5 mL of t-butanol were charged and stirred at room temperature until homogenous to obtain a mixture. 0.23 g of potassium tert-butoxide was added to this mixture, and the mixture was reacted at 70°C for 16 hours with stirring.

[0283] The compound represented by formula (6-1) was synthesized by the following method. First, the primary hydroxyl groups of 3-butene-1,2-diol were protected using tert-butyldimethylchlorosilane (TBS-Cl), and then the secondary hydroxyl groups were protected using dihydropyran (DHP). Then, the tert-butyldimethylsilyl (TBS) groups were deprotected, and the resulting primary hydroxyl groups were reacted with 2-(2-bromoethoxy)tetrahydro-2H-pyran. Finally, the vinyl groups were oxidized using m-chloroperbenzoic acid (mCPBA).

[0284] After the reaction, the reaction solution obtained was returned to room temperature, and 10 g of a 10% hydrogen chloride-methanol solution (hydrogen chloride-methanol reagent (5-10%), manufactured by Tokyo Chemical Industry Co., Ltd.) was added, followed by stirring at room temperature for 4 hours. Thereafter, the reaction solution was transferred little by little to a separatory funnel containing 25 mL of saturated aqueous sodium bicarbonate, and extracted twice with 50 mL of ethyl acetate. The organic layer was washed with 25 mL of brine, 25 mL of saturated aqueous sodium bicarbonate, and 25 mL of brine in that order, and dehydrated with anhydrous sodium sulfate. After filtering off the desiccant, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain compound (AA) (Rf １ is the PFPE chain represented by the above formula (5-1). １ In this example, h representing the average degree of polymerization is 5.0, and i representing the average degree of polymerization is 0.

[0285] The obtained compound (AA) １ H-NMR and １９F-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 3.40-3.85 (26H), 3.85-4.10 (4H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -80.5 (4F), -91.0 to -88.5 (20F)

[0286] [Example 2] The compound represented by the above formula (AB) was obtained by the following method. ２ CF ２ O (CF ２ CF ２ O) ｈ (CF ２ O) ｉ CF ２ CH ２ Instead of the compound represented by OH, ２ CF ２ CF ２ O (CF ２ CF ２ CF ２ O) ｊ CF ２ CF ２ CH ２ The same procedure as in Example 1 was carried out to obtain compound (AB) (Rf in formula (AB)), except that a compound (number average molecular weight: 950, molecular weight distribution: 1.1) represented by the formula OH (where j, representing the average degree of polymerization, is 4.0) was used. ２ is the PFPE chain represented by the above formula (5-2). ２ In this formula, j, which indicates the average degree of polymerization, is 4.0.

[0287] The obtained compound (AB) １ H-NMR and １９ F-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 3.40-3.85 (26H), 3.85-4.10 (4H) １９ F-NMR (acetone-D ６): δ [ppm] = -84.0 to -83.0 (16F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (8F)

[0288] [Example 3] A compound represented by the above formula (AI) was obtained by the method shown below. Compound (AI) (Rf in formula (AI)) was obtained by the same procedure as in Example 1, except that a compound represented by formula (6-2) was used instead of a compound represented by formula (6-1). １ is the PFPE chain represented by the above formula (5-1). １ In this example, h representing the average degree of polymerization is 5.0, and i representing the average degree of polymerization is 0.

[0289] The compound represented by formula (6-2) was synthesized by the following method. First, 1,3-butadiene diepoxide was reacted with twice the molar amount of 3-buten-1-ol. Next, the two resulting hydroxyl groups were protected using DHP. Finally, one of the two vinyl groups was oxidized using mCPBA.

[0290] The obtained compound (AI) １ H-NMR and １９ F-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 1.65-1.80 (4H), 2.10-2.30 (4H), 3.40-3.85 (32H), 3.85-4.10 (4H), 4.80-5.10 (4H), 5.80-5.90 (2H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -80.5 (4F), -91.0 to -88.5 (20F)

[0291] [Example 4] The compound represented by the above formula (AJ) was obtained by the following method. The compound represented by formula (6-2) was used instead of the compound represented by formula (6-1), and HOCH ２ CF ２ O (CF ２ CF ２ O) ｈ (CF ２ O) ｉ CF２ CH ２ Instead of the compound represented by OH, ２ CF ２ CF ２ O (CF ２ CF ２ CF ２ O) ｊ CF ２ CF ２ CH ２ The same procedure as in Example 1 was carried out to obtain compound (AJ) (Rf in formula (AJ)) except that a compound (number average molecular weight: 950, molecular weight distribution: 1.1) represented by the formula OH (where j, representing the average degree of polymerization, is 4.0) was used. ２ is the PFPE chain represented by the above formula (5-2). ２ In this formula, j, which indicates the average degree of polymerization, is 4.0.

[0292] The obtained compound (AJ) １ H-NMR and １９ F-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 1.65-1.80 (4H), 2.10-2.30 (4H), 3.40-3.85 (32H), 3.85-4.10 (4H), 4.80-5.10 (4H), 5.80-5.90 (2H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (16F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (8F)

[0293] [Example 5] A compound represented by the above formula (AN) was obtained by the method shown below. The same procedure as in Example 1 was carried out, except that a compound represented by formula (6-3) was used instead of a compound represented by formula (6-1), to obtain compound (AN) (Rf １ is the PFPE chain represented by the above formula (5-1). １ In this example, h representing the average degree of polymerization is 5.0, and i representing the average degree of polymerization is 0.

[0294] The compound represented by formula (6-3) was synthesized by reacting the two hydroxyl groups of (+)-2,3-O-isopropylidene-L-threitol with methyl iodide and epibromohydrin in this order.

[0295] The obtained compound (AN) １ H-NMR and １９ F-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 3.40-3.85 (34H), 3.85-4.10 (4H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -80.5 (4F), -91.0 to -88.5 (20F)

[0296] [Example 6] The compound represented by the above formula (AO) was obtained by the following method. The compound represented by formula (6-3) was used instead of the compound represented by formula (6-1), and HOCH ２ CF ２ O (CF ２ CF ２ O) ｈ (CF ２ O) ｉ CF ２ CH ２ Instead of the compound represented by OH, ２ CF ２ CF ２ O (CF ２ CF ２ CF ２ O) ｊ CF ２ CF ２ CH ２ The same procedure as in Example 1 was carried out to obtain compound (AO) (Rf in formula (AO)) except that a compound (number average molecular weight: 950, molecular weight distribution: 1.1) represented by the formula OH (where j, representing the average degree of polymerization, is 4.0) was used. ２ is the PFPE chain represented by the above formula (5-2). ２ In this formula, j, which indicates the average degree of polymerization, is 4.0.

[0297] The obtained compound (AO) １ H-NMR and１９ F-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 3.40-3.85 (34H), 3.85-4.10 (4H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (16F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (8F)

[0298] [Example 7] A compound represented by the above formula (AP) was obtained by the method shown below. Compound (AP) (Rf in formula (AP)) was obtained by the same procedure as in Example 1, except that a compound represented by formula (6-4) was used instead of a compound represented by formula (6-1). １ is the PFPE chain represented by the above formula (5-1). １ In this example, h representing the average degree of polymerization is 5.0, and i representing the average degree of polymerization is 0.

[0299] The compound represented by formula (6-4) was synthesized by the following method. First, one of the epoxy groups of 1,3-butadiene diepoxide was reacted with an equimolar amount of 3-buten-1-ol. Then, the other epoxy group of 1,3-butadiene diepoxide was reacted with an equimolar amount of methanol. Next, the two hydroxyl groups generated by the reaction were protected using DHP. Finally, the vinyl group was oxidized using mCPBA.

[0300] The obtained compound (AP) １ H-NMR and １９ F-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 1.65-1.80 (4H), 3.40-3.85 (34H), 3.85-4.10 (4H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -80.5 (4F), -91.0 to -88.5 (20F)

[0301] [Example 8] The compound represented by the above formula (AQ) was obtained by the following method. The compound represented by formula (6-5) was used instead of the compound represented by formula (6-1), and HOCH ２ CF ２ O (CF ２ CF ２ O) ｈ (CF ２ O) ｉ CF ２ CH ２ Instead of the compound represented by OH, ２ CF ２ CF ２ O (CF ２ CF ２ CF ２ O) ｊ CF ２ CF ２ CH ２ The same procedure as in Example 1 was carried out to obtain compound (AQ) (Rf in formula (AQ)) except that a compound (number average molecular weight: 950, molecular weight distribution: 1.1) represented by the formula OH (where j, representing the average degree of polymerization, is 4.0) was used. ２ is the PFPE chain represented by the above formula (5-2). ２ In this formula, j, which indicates the average degree of polymerization, is 4.0.

[0302] The compound represented by formula (6-5) was synthesized by the following method. First, the primary hydroxyl groups of 3-butene-1,2-diol were protected using TBS-Cl, and then the secondary hydroxyl groups were protected using DHP. The TBS groups were then deprotected, and the resulting primary hydroxyl groups were reacted with methyl iodide. Finally, the vinyl groups were oxidized using mCPBA.

[0303] The obtained compound (AQ) １ H-NMR and １９ F-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 3.40-3.85 (22H), 3.85-4.10 (4H) １９ F-NMR (acetone-D ６): δ [ppm] = -84.0 to -83.0 (16F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (8F)

[0304] [Example 9] The compound represented by the above formula (AS) was obtained by the following method. The compound represented by formula (6-6) was used instead of the compound represented by formula (6-1), and HOCH ２ CF ２ O (CF ２ CF ２ O) ｈ (CF ２ O) ｉ CF ２ CH ２ Instead of the compound represented by OH, ２ CF ２ CF ２ O (CF ２ CF ２ CF ２ O) ｊ CF ２ CF ２ CH ２ The same procedure as in Example 1 was carried out to obtain compound (AS) (Rf ２ is the PFPE chain represented by the above formula (5-2). ２ In this formula, j, which indicates the average degree of polymerization, is 4.0.

[0305] The compound represented by formula (6-6) was synthesized by the following method. First, one of the epoxy groups of 1,3-butadiene diepoxide was reacted with an equimolar amount of 3-buten-1-ol. Next, the other epoxy group of 1,3-butadiene diepoxide was reacted with an equimolar amount of 2,2,3,3,3-pentafluoropropanol. Next, the two resulting hydroxyl groups were protected using DHP. Finally, the vinyl group was oxidized using mCPBA.

[0306] The obtained compound (AS) １ H-NMR and １９ F-NMR measurement was carried out, and the structure was identified from the following results. １H-NMR (acetone-D ６ ): δ [ppm] = 1.65-1.80 (4H), 3.40-3.85 (28H), 3.85-4.10 (8H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (22F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (12F)

[0307] [Example 10] The compound represented by the above formula (AW) was obtained by the following method. The compound represented by formula (6-7) was used instead of the compound represented by formula (6-1), and HOCH ２ CF ２ O (CF ２ CF ２ O) ｈ (CF ２ O) ｉ CF ２ CH ２ Instead of the compound represented by OH, ２ CF ２ CF ２ O (CF ２ CF ２ CF ２ O) ｊ CF ２ CF ２ CH ２ The same procedure as in Example 1 was carried out to obtain compound (AW) (Rf in formula (AW)) except that a compound (number average molecular weight: 950, molecular weight distribution: 1.1) represented by the formula OH (where j, representing the average degree of polymerization, is 4.0) was used. ２ is the PFPE chain represented by the above formula (5-2). ２ In this formula, j, which indicates the average degree of polymerization, is 4.0.

[0308] The compound represented by formula (6-7) was synthesized by protecting the two hydroxyl groups of 3-butene-1,2-diol with DHP, and then oxidizing the vinyl group with mCPBA.

[0309] The obtained compound (AW) １ H-NMR and １９ F-NMR measurement was carried out, and the structure was identified from the following results.１ H-NMR (acetone-D ６ ): δ [ppm] = 3.40-3.85 (18H), 3.85-4.10 (4H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (16F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (8F)

[0310] [Example 11] The compound represented by the above formula (BA) was obtained by the following method. (First Reaction) HOCH ２ CF ２ O (CF ２ CF ２ O) ｈ (CF ２ O) ｉ CF ２ CH ２ 12 g of a compound (number average molecular weight: 750, molecular weight distribution: 1.1) represented by formula (6-2), 5.1 g of the compound represented by formula (6-2), and 12 mL of t-butanol were charged and stirred at room temperature until homogenous to obtain a mixture. 0.65 g of potassium tert-butoxide was added to this mixture, and the mixture was reacted at 70°C for 16 hours with stirring.

[0311] 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 7.0 g of a compound represented by the following formula (10-1) as intermediate compound 1.

[0312] (Rf in formula (10-1) １ is the PFPE chain represented by the above formula (5-1). １ In the formula, h, which indicates the average degree of polymerization, is 5.0, and i, which indicates the average degree of polymerization, is 0. THP represents a tetrahydropyranyl group.

[0313] (Second Reaction) Subsequently, under a nitrogen gas atmosphere, 7.0 g of the compound represented by formula (10-1), which is intermediate compound 1 obtained above, 2.70 g of the compound represented by formula (6-1), and 20 mL of t-butanol were placed in a 100 mL recovery flask and stirred at room temperature until a homogeneous mixture was obtained. 3.3 g of potassium tert-butoxide was added to this mixture, and the mixture was allowed to react with stirring at 70°C for 16 hours.

[0314] After the reaction, the reaction solution obtained 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, followed by stirring at room temperature for 4 hours. Thereafter, the reaction solution was transferred little by little 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 with 100 mL of brine, 100 mL of saturated aqueous sodium bicarbonate, and 100 mL of brine in that order, and dehydrated with anhydrous sodium sulfate. After filtering off the desiccant, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain compound (BA) (Rf １ is the PFPE chain represented by the above formula (5-1). １ In this example, h representing the average degree of polymerization is 5.0, and i representing the average degree of polymerization is 0.

[0315] The obtained compound (BA) １ H-NMR and １９ F-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 1.65-1.80 (2H), 2.10-2.30 (2H), 3.40-3.85 (29H), 3.85-4.10 (4H), 4.80-5.10 (2H), 5.80-5.90 (1H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -80.5 (4F), -91.0 to -88.5 (20F)

[0316] [Example 12] The compound represented by the above formula (BB) was obtained by the method shown below. ２ CF ２ O (CF ２ CF ２O) ｈ (CF ２ O) ｉ CF ２ CH ２ Instead of the compound represented by OH, ２ CF ２ CF ２ O (CF ２ CF ２ CF ２ O) ｊ CF ２ CF ２ CH ２ The same procedure as in Example 11 was carried out to obtain compound (BB) (Rf in formula (BB)) except that a compound (number average molecular weight: 950, molecular weight distribution: 1.1) represented by the formula OH (where j, representing the average degree of polymerization, is 4.0) was used. ２ is the PFPE chain represented by the above formula (5-2). ２ In this formula, j, which indicates the average degree of polymerization, is 4.0.

[0317] The obtained compound (BB) １ H-NMR and １９ F-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 1.65-1.80 (2H), 2.10-2.30 (2H), 3.40-3.85 (29H), 3.85-4.10 (4H), 4.80-5.10 (2H), 5.80-5.90 (1H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (16F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (8F)

[0318] [Example 13] The compound represented by the above formula (BC) was obtained by the following method. Using the compound represented by formula (6-4) instead of the compound represented by formula (6-1), ２ CF ２ O (CF ２ CF ２ O) ｈ (CF ２ O) ｉ CF ２ CH２ Instead of the compound represented by OH, ２ CF ２ CF ２ O (CF ２ CF ２ CF ２ O) ｊ CF ２ CF ２ CH ２ The same procedure as in Example 11 was carried out to obtain compound (BC) (Rf in formula (BC)), except that a compound (number average molecular weight: 950, molecular weight distribution: 1.1) represented by the formula OH (where j, representing the average degree of polymerization, is 4.0) was used. ２ is the PFPE chain represented by the above formula (5-2). ２ In this formula, j, which indicates the average degree of polymerization, is 4.0.

[0319] The obtained compound (BC) １ H-NMR and １９ F-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 1.65-1.80 (2H), 2.10-2.30 (2H), 3.40-3.85 (31H), 3.85-4.10 (4H), 4.80-5.10 (2H), 5.80-5.90 (1H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (16F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (8F)

[0320] [Example 14] The compound represented by the above formula (BD) was obtained by the following method. The compound represented by formula (6-8) was used instead of the compound represented by formula (6-2), and HOCH ２ CF ２ O (CF ２ CF ２ O) ｈ (CF ２ O) ｉ CF ２ CH ２ Instead of the compound represented by OH, ２ CF ２ CF２ O (CF ２ CF ２ CF ２ O) ｊ CF ２ CF ２ CH ２ The same procedure as in Example 11 was carried out to obtain compound (BD) (Rf ２ is the PFPE chain represented by the above formula (5-2). ２ In this formula, j, which indicates the average degree of polymerization, is 4.0.

[0321] The compound represented by formula (6-8) was synthesized by protecting the hydroxyl group of ethylene glycol monoallyl ether with DHP, and then oxidizing the vinyl group with mCPBA.

[0322] The obtained compound (BD) １ H-NMR and １９ F-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 3.40-3.85 (24H), 3.85-4.10 (4H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (16F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (8F)

[0323] [Example 15] A compound represented by the above formula (BE) was obtained by the method shown below. Compound (BE) (Rf in formula (BE)) was obtained by the same procedure as in Example 11, except that a compound represented by formula (6-9) was used instead of a compound represented by formula (6-2). １ is the PFPE chain represented by the above formula (5-1). １ In this example, h representing the average degree of polymerization is 5.0, and i representing the average degree of polymerization is 0.

[0324] The compound represented by formula (6-9) was synthesized by reacting a compound obtained by brominating the hydroxyl group of solketal (2,2-dimethyl-1,3-dioxolane-4-methanol) with 3-buten-1-ol, and then oxidizing the vinyl group of the resulting compound with mCPBA.

[0325] The obtained compound (BE) １ H-NMR and １９ F-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 1.65-1.85 (2H), 3.40-3.85 (29H), 3.85-4.10 (4H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -80.5 (4F), -91.0 to -88.5 (20F)

[0326] [Example 16] The compound represented by the above formula (BF) was obtained by the following method. The compound represented by formula (6-10) was used instead of the compound represented by formula (6-1), and HOCH ２ CF ２ O (CF ２ CF ２ O) ｈ (CF ２ O) ｉ CF ２ CH ２ Instead of the compound represented by OH, ２ CF ２ CF ２ O (CF ２ CF ２ CF ２ O) ｊ CF ２ CF ２ CH ２ The same procedure as in Example 11 was carried out to obtain compound (BF) (Rf in formula (BF)) (number average molecular weight: 950, molecular weight distribution: 1.1), except that a compound represented by the formula (BF) (where j, representing the average degree of polymerization, is 4.0) was used. ２ is the PFPE chain represented by the above formula (5-2). ２ In this formula, j, which indicates the average degree of polymerization, is 4.0.

[0327] The compound represented by formula (6-10) was synthesized by reacting 3-buten-1-ol with the compound represented by formula (6-8), protecting the resulting hydroxyl group with DHP, and then oxidizing the vinyl group with mCPBA.

[0328] The obtained compound (BF) １ H-NMR and １９ F-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 1.65-1.80 (4H), 2.10-2.30 (2H), 3.40-3.85 (33H), 3.85-4.10 (4H), 4.80-5.10 (2H), 5.80-5.90 (1H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (16F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (8F)

[0329] [Example 17] The compound represented by the above formula (BG) was obtained by the following method. The compound represented by formula (6-9) was used instead of the compound represented by formula (6-1), and HOCH ２ CF ２ O (CF ２ CF ２ O) ｈ (CF ２ O) ｉ CF ２ CH ２ Instead of the compound represented by OH, ２ CF ２ CF ２ O (CF ２ CF ２ CF ２ O) ｊ CF ２ CF ２ CH ２ The same procedure as in Example 11 was carried out to obtain compound (BG) (Rf in formula (BG)) except that a compound (number average molecular weight: 950, molecular weight distribution: 1.1) represented by the formula OH (where j, representing the average degree of polymerization, is 4.0) was used. ２is the PFPE chain represented by the above formula (5-2). ２ In this formula, j, which indicates the average degree of polymerization, is 4.0.

[0330] The obtained compound (BG) １ H-NMR and １９ F-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 1.65-1.80 (4H), 2.10-2.30 (2H), 3.40-3.85 (29H), 3.85-4.10 (4H), 4.80-5.10 (2H), 5.80-5.90 (1H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (16F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (8F)

[0331] [Example 18] The compound represented by the above formula (BH) was obtained by the following method. Using the compound represented by formula (6-11) instead of the compound represented by formula (6-1), ２ CF ２ O (CF ２ CF ２ O) ｈ (CF ２ O) ｉ CF ２ CH ２ Instead of the compound represented by OH, ２ CF ２ CF ２ O (CF ２ CF ２ CF ２ O) ｊ CF ２ CF ２ CH ２ The same procedure as in Example 11 was carried out to obtain a compound (BH) (Rf in formula (BH)) (number average molecular weight: 950, molecular weight distribution: 1.1) represented by the formula OH (where j, representing the average degree of polymerization, is 4.0). ２ is the PFPE chain represented by the above formula (5-2). ２In this formula, j, which indicates the average degree of polymerization, is 4.0.

[0332] The compound represented by formula (6-11) was synthesized by reacting a compound obtained by brominating the hydroxyl group of solketal with 5-hexen-1-ol, and then oxidizing the vinyl group of the resulting compound with mCPBA.

[0333] The obtained compound (BH) １ H-NMR and １９ F-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 1.45-1.85 (8H), 2.10-2.30 (2H), 3.40-3.85 (29H), 3.85-4.10 (4H), 4.80-5.10 (2H), 5.80-5.90 (1H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (16F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (8F)

[0334] [Example 19] The compound represented by the above formula (BI) was obtained by the following method. The compound represented by formula (6-12) was used instead of the compound represented by formula (6-1), and HOCH ２ CF ２ O (CF ２ CF ２ O) ｈ (CF ２ O) ｉ CF ２ CH ２ Instead of the compound represented by OH, ２ CF ２ CF ２ O (CF ２ CF ２ CF ２ O) ｊ CF ２ CF ２ CH ２The same procedure as in Example 11 was carried out, except that a compound (number average molecular weight: 950, molecular weight distribution: 1.1) represented by the formula (BI) was used. ２ is the PFPE chain represented by the above formula (5-2). ２ In this formula, j, which indicates the average degree of polymerization, is 4.0.

[0335] The compound represented by formula (6-12) was synthesized by protecting the 1,2-diol moiety of 1,2,4-butanetriol with acetone, and then reacting the hydroxyl group at the 4-position with epibromohydrin.

[0336] The obtained compound (BI) １ H-NMR and １９ F-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 1.45-1.85 (8H), 2.10-2.30 (2H), 3.40-3.85 (29H), 3.85-4.10 (4H), 4.80-5.10 (2H), 5.80-5.90 (1H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (16F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (8F)

[0337] [Example 20] The compound represented by the above formula (BJ) was obtained by the following method. Using the compound represented by formula (6-13) instead of the compound represented by formula (6-1), ２ CF ２ O (CF ２ CF ２ O) ｈ (CF ２ O) ｉ CF ２ CH ２ Instead of the compound represented by OH, ２ CF ２ CF ２ O (CF ２ CF ２ CF ２ O)ｊ CF ２ CF ２ CH ２ The same procedure as in Example 11 was carried out to obtain compound (BJ) (Rf in formula (BJ)) except that a compound (number average molecular weight: 950, molecular weight distribution: 1.1) represented by the formula OH (where j, representing the average degree of polymerization, is 4.0) was used. ２ is the PFPE chain represented by the above formula (5-2). ２ In this formula, j, which indicates the average degree of polymerization, is 4.0.

[0338] The compound represented by formula (6-13) was synthesized by the following method. After protecting the 1,2-diol moiety of 1,2,4-butanetriol with acetone, the hydroxyl group at the 4-position was brominated and reacted with 3-buten-1-ol to obtain the compound. The vinyl group of the obtained compound was then oxidized with mCPBA to synthesize the compound.

[0339] The obtained compound (BJ) １ H-NMR and １９ F-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 1.65-1.80 (6H), 2.10-2.30 (2H), 3.40-3.85 (29H), 3.85-4.10 (4H), 4.80-5.10 (2H), 5.80-5.90 (1H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (16F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (8F)

[0340] [Example 21] The compound represented by the above formula (BK) was obtained by the following method. The compound represented by formula (6-14) was used instead of the compound represented by formula (6-1), and HOCH ２ CF ２ O (CF ２ CF ２ O) ｈ (CF ２ O) ｉ CF ２ CH ２Instead of the compound represented by OH, ２ CF ２ CF ２ O (CF ２ CF ２ CF ２ O) ｊ CF ２ CF ２ CH ２ The same procedure as in Example 11 was carried out to obtain compound (BK) (Rf in formula (BK)) except that a compound (number average molecular weight: 950, molecular weight distribution: 1.1) represented by the formula OH (where j, representing the average degree of polymerization, is 4.0) was used. ２ is the PFPE chain represented by the above formula (5-2). ２ In this formula, j, which indicates the average degree of polymerization, is 4.0.

[0341] The compound represented by formula (6-14) was synthesized by protecting the two hydroxyl groups of 3-allyloxy-1,2-propanediol with dihydropyran, and then oxidizing the vinyl group with mCPBA.

[0342] The obtained compound (BK) １ H-NMR and １９ F-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 1.65-1.80 (2H), 2.10-2.30 (2H), 3.40-3.85 (29H), 3.85-4.10 (4H), 4.80-5.10 (2H), 5.80-5.90 (1H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (16F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (8F)

[0343] [Example 22] The compound represented by the above formula (BL) was obtained by the following method. Instead of the compound represented by formula (6-1), the compound represented by formula (6-15) was used, and HOCH ２ CF ２ O (CF ２ CF ２ O) ｈ (CF２ O) ｉ CF ２ CH ２ Instead of the compound represented by OH, ２ CF ２ CF ２ O (CF ２ CF ２ CF ２ O) ｊ CF ２ CF ２ CH ２ The same procedure as in Example 11 was carried out to obtain compound (BL) (Rf in formula (BL)) except that a compound (number average molecular weight: 950, molecular weight distribution: 1.1) represented by the formula OH (where j, representing the average degree of polymerization, is 4.0) was used. ２ is the PFPE chain represented by the above formula (5-2). ２ In this formula, j, which indicates the average degree of polymerization, is 4.0.

[0344] The compound represented by formula (6-15) was synthesized by oxidizing the vinyl group of 2-allyloxytetrahydropyran with mCPBA.

[0345] The obtained compound (BL) １ H-NMR and １９ F-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 1.65-1.80 (2H), 2.10-2.30 (2H), 3.40-3.85 (23H), 3.85-4.10 (4H), 4.80-5.10 (2H), 5.80-5.90 (1H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (16F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (8F)

[0346] [Example 23] The compound represented by the above formula (BM) was obtained by the following method. The compound represented by formula (6-16) was used instead of the compound represented by formula (6-1), and HOCH ２ CF ２ O (CF ２ CF２ O) ｈ (CF ２ O) ｉ CF ２ CH ２ Instead of the compound represented by OH, ２ CF ２ CF ２ O (CF ２ CF ２ CF ２ O) ｊ CF ２ CF ２ CH ２ The same procedure as in Example 11 was carried out to obtain compound (BM) (Rf ２ is the PFPE chain represented by the above formula (5-2). ２ In this formula, j, which indicates the average degree of polymerization, is 4.0.

[0347] The compound represented by formula (6-16) was synthesized by reacting one hydroxyl group of 1,3-propanediol with a compound obtained by brominating the hydroxyl group of solketal, and then reacting the other hydroxyl group of 1,3-propanediol with epibromohydrin.

[0348] The obtained compound (BM) １ H-NMR and １９ F-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 1.65-1.80 (4H), 2.10-2.30 (2H), 3.40-3.85 (33H), 3.85-4.10 (4H), 4.80-5.10 (2H), 5.80-5.90 (1H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (16F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (8F)

[0349] [Example 24] A compound represented by the above formula (CA) was obtained by the method shown below. First, the same operation as in the first reaction of Example 11 was carried out, except that a compound represented by formula (6-1) was used instead of the compound represented by formula (6-2), to obtain 6.7 g of a compound represented by the following formula (10-2) as intermediate compound 1.

[0350] (Rf in formula (10-2) １ is the PFPE chain represented by the above formula (5-1). １ In the formula, h, which indicates the average degree of polymerization, is 5.0, and i, which indicates the average degree of polymerization, is 0. THP represents a tetrahydropyranyl group.

[0351] Next, 6.7 g of the compound represented by formula (10-2), which is intermediate compound 1 obtained above, 0.55 g of epibromohydrin represented by formula (8-1), and 10 mL of t-butanol were placed in a 100 mL recovery flask under a nitrogen gas atmosphere and stirred at room temperature until the mixture became homogeneous. 0.72 g of potassium tert-butoxide was added to this homogeneous solution, and the mixture was allowed to react with stirring at 70°C for 23 hours.

[0352] After the reaction, the reaction solution obtained was returned to room temperature, and 10 g of a 10% hydrogen chloride-methanol solution (hydrogen chloride-methanol reagent (5-10%), manufactured by Tokyo Chemical Industry Co., Ltd.) was added, followed by stirring at room temperature for 4 hours. Thereafter, the reaction solution was transferred little by little to a separatory funnel containing 25 mL of saturated aqueous sodium bicarbonate, and extracted twice with 50 mL of ethyl acetate. The organic layer was washed with 25 mL of brine, 25 mL of saturated aqueous sodium bicarbonate, and 25 mL of brine in that order, and dehydrated with anhydrous sodium sulfate. After filtering off the desiccant, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain compound (CA) (the two Rf １ is a PFPE chain represented by the above formula (5-1). １ In this example, h representing the average degree of polymerization is 5.0, and i representing the average degree of polymerization is 0.

[0353] The obtained compound (CA) １ H-NMR and １９ F-NMR measurement was carried out, and the structure was identified from the following results. １H-NMR (acetone-D ６ ): δ [ppm] = 3.40-3.85 (32H), 3.85-4.10 (8H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -80.5 (8F), -91.0 to -88.5 (40F)

[0354] The compounds of Examples 1 to 24 thus obtained are respectively applied to formula (1) to determine x and R １ , R ２ , R ３ , R ４ The structure is shown in Table 1.

[0355] [Example 25] A compound represented by the above formula (DA) was obtained by the method shown below. Compound (DA) (Rf ２ is the PFPE chain represented by the above formula (5-2). ２ In the formula (6-17), j, which indicates the average degree of polymerization, is 4.0. 3.12 g of solketal was obtained. The compound represented by formula (6-17) was synthesized by the following method. First, p-toluenesulfonic acid chloride was allowed to act on the hydroxyl group of solketal to obtain a compound in which the hydroxyl group of solketal was tosylated. Next, the primary hydroxyl group of 3-butene-1,2-diol was protected using tert-butyldimethylchlorosilane (TBS-Cl), and then the secondary hydroxyl group was protected using dihydropyran (DHP). Thereafter, the primary hydroxyl group generated by deprotecting the tert-butyldimethylsilyl (TBS) group was reacted with the compound in which the hydroxyl group of solketal was tosylated. Finally, the vinyl group was oxidized using m-chloroperbenzoic acid (mCPBA). The resulting compound (DA) １ H-NMR and １９ F-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 3.40-3.85 (22H), 3.85-4.10 (4H) １９ F-NMR (acetone-D ６): δ [ppm] = -84.0 to -83.0 (16F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (8F)

[0356]

[0357] Comparative Example 1 A compound represented by the following formula (ZA) was synthesized by the method described in Patent Document 1.

[0358] (Rf in formula (ZA) ２ is the PFPE chain represented by the above formula (5-2). ２ In this case, j, which indicates the average degree of polymerization, is 4.5.

[0359] Comparative Example 2 A compound represented by the following formula (ZB) was synthesized by the method described in Patent Document 2.

[0360] (Rf in formula (ZB) ２ is the PFPE chain represented by the above formula (5-2). ２ In this case, j, which indicates the average degree of polymerization, is 4.5.

[0361] Comparative Example 3 A compound represented by the following formula (ZC) was synthesized by the method described in Patent Document 3.

[0362] (Rf in formula (ZC) １ is the PFPE chain represented by the above formula (5-1). １ In the formula, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5.

[0363] Comparative Example 4 A compound represented by the following formula (ZD) was synthesized by the following method.

[0364] (Rf in formula (ZD) ２ is the PFPE chain represented by the above formula (5-2). ２ In this case, j, which indicates the average degree of polymerization, is 4.5.

[0365] Instead of the compound represented by formula (6-1), a compound represented by formula (6-14) was used, and instead of the compound represented by formula (6-2), a compound represented by formula (6-15) was used. ２ CF ２ O (CF ２ CF ２ O) ｈ (CF ２ O) ｉ CF ２ CH ２ Instead of the compound represented by OH, ２ CF ２ CF ２ O (CF ２ CF ２ CF ２ O) ｊ CF ２ CF ２ CH ２ The same operation as in Example 11 was performed except that a compound represented by the formula OH (where j, which represents the average degree of polymerization, is 4.5) (number average molecular weight: 950, molecular weight distribution: 1.1) was used, thereby obtaining 2.81 g of compound (ZD).

[0366] The obtained compound (ZD) １ H-NMR and １９ F-NMR measurement was carried out, and the structure was identified from the following results. １ H-NMR (acetone-D ６ ): δ [ppm] = 3.40-3.85 (20H), 3.85-4.10 (4H) １９ F-NMR (acetone-D ６ ): δ [ppm] = -84.0 to -83.0 (18F), -86.4 (4F), -124.3 (4F), -130.0 to -129.0 (9F)

[0367] Comparative Example 5 A compound represented by the following formula (ZA) was synthesized by the method described in Patent Document 4.

[0368] (Two Rf in formula (ZE) １ is a PFPE chain represented by the above formula (5-1). １ In the formula, h representing the average degree of polymerization is 7.0, and i representing the average degree of polymerization is 0.

[0369] The number average molecular weights (Mn) of the compounds thus obtained in Examples 1 to 24 and Comparative Examples 1 to 5 were measured by the above-mentioned method. The results are shown in Table 2.

[0370] Next, solutions for forming lubricating layers were prepared by the method described below using the compounds obtained in Examples 1 to 24 and Comparative Examples 1 to 5. Then, using the obtained solutions for forming lubricating layers, lubricating layers for magnetic recording media were formed by the method described below, thereby obtaining the magnetic recording media of Examples 1 to 24 and Comparative Examples 1 to 5.

[0371] "Lubricant Layer-Forming Solution" The compounds obtained in Examples 1 to 24 and Comparative Examples 1 to 5 were each dissolved in a fluorine-based solvent, Vertrel (registered trademark) XF (trade name, manufactured by DuPont-Mitsui Fluorochemicals Co., Ltd.), and diluted with Vertrel XF so that the film thickness when applied to the protective layer would be 8.0 Å to 8.5 Å, to prepare a lubricant layer-forming solution.

[0372] "Magnetic Recording Medium" A magnetic recording medium was prepared by sequentially providing an adhesive layer, a soft magnetic layer, a first underlayer, a second underlayer, a magnetic layer, and a protective layer on a substrate with a diameter of 65 mm. The protective layer was made of carbon. The lubricant layer-forming solutions of Examples 1 to 24 and Comparative Examples 1 to 5 were applied by dipping onto the protective layer of the magnetic recording medium, on which each layer up to the protective layer had been formed. The dipping was performed under the following conditions: an immersion speed of 10 mm / sec, an immersion time of 30 seconds, and a pull-up speed of 1.2 mm / sec.

[0373] 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.

[0374] [Film Thickness Measurement] The film thickness of the lubricating layer of each of the magnetic recording media thus obtained in Examples 1 to 24 and Comparative Examples 1 to 5 was measured using a Fourier transform infrared spectrophotometer (FT-IR, product name: Nicolet iS50, manufactured by Thermo Fisher Scientific). The results are shown in Table 2.

[0375] Next, the following chemical resistance tests and spin-off characteristic tests were carried out on the magnetic recording media of Examples 1 to 25 and Comparative Examples 1 to 5. The results are shown in Table 2.

[0376] [Chemical substance resistance test] Contamination of magnetic recording media by environmental substances that generate contaminants in a high-temperature environment was investigated using the following method: Si ions were used as the environmental substances, and the amount of Si adsorption was measured as the amount of contaminants that contaminate the magnetic recording media generated by the environmental substances.

[0377] Specifically, the magnetic recording medium to be evaluated was stored for 240 hours in a high-temperature environment of 85°C and 0% humidity in the presence of siloxane-based Si rubber. The amount of Si adsorption present on the surface of the magnetic recording medium was then analyzed and measured using secondary ion mass spectrometry (SIMS), and the degree of contamination by Si ions was evaluated as the amount of Si adsorption. The amount of Si adsorption was evaluated based on the following criteria, with the result of the amount of Si adsorption in Comparative Example 4 set at 1.00. The results are shown in Table 2.

[0378] "Chemical substance resistance evaluation criteria" A+: Si adsorption amount less than 0.60 A: Si adsorption amount 0.60 or more and less than 0.70 B: Si adsorption amount 0.70 or more and less than 0.90 C: Si adsorption amount 0.90 or more and less than 1.10 D: Si adsorption amount 1.10 or more

[0379] [Spin-off property test] A magnetic recording medium was mounted on a spin stand and rotated at a rotation speed of 10,000 rpm in an environment of 80°C for 72 hours. Before and after this operation, the film thickness of the lubricating layer at a position 20 mm radius from the center of the magnetic recording medium was measured using FT-IR, and the film thickness reduction rate of the lubricating layer before and after the test was calculated. The spin-off property was evaluated using the calculated film thickness reduction rate according to the evaluation criteria shown below.

[0380] "Evaluation criteria for spin-off characteristics" A+: Film thickness reduction rate less than 2% A: Film thickness reduction rate 2% or more but less than 3% B: Film thickness reduction rate 3% or more but less than 5% C: Film thickness reduction rate 5% or more but less than 10% D: Film thickness reduction rate 10% or more

[0381] [Overall Evaluation] From the results of the chemical resistance test and the spin-off property test, an overall evaluation was made based on the following criteria.

[0382] "Overall evaluation criteria" A: Both the evaluation of the chemical resistance test and the evaluation of the spin-off characteristics test are A+ or A. B: One of the evaluation of the chemical resistance test and the evaluation of the spin-off characteristics test is B, and the other is A+, A, or B. C: One of the evaluation of the chemical resistance test and the evaluation of the spin-off characteristics test is C, and the other is A+, A, B, or C. D: At least one of the evaluation of the chemical resistance test and the evaluation of the spin-off characteristics test is D.

[0383]

[0384] As shown in Table 2, R １ and R ４ The magnetic recording media of Examples 1 to 25, which used fluorine-containing ether compounds satisfying formula (1), in which at least one of the terminal groups is represented by formula (2), all received evaluations of A+, A, or B in the chemical resistance test and spin-off property test, and received an overall evaluation of A or B. This confirms that the lubricating layers of the magnetic recording media of Examples 1 to 25 have good chemical resistance and can suppress spin-off.

[0385] In contrast, as shown in Table 2, the magnetic recording media of Comparative Examples 1 to 5, which used compounds (ZA) to (ZE) that did not contain an erythritol structure, were all rated B, C, or D in the chemical resistance test and the spin-off characteristics test, and the overall rating was C or D.

[0386] More specifically, the hydroxyl groups contained in the compounds (ZA) to (ZC) used in Comparative Examples 1 to 3 all make a large contribution to increasing the polarity of the entire molecule, thereby increasing the surface free energy of the fluorinated ether compound. Furthermore, the hydroxyl groups contained in the compounds (ZA) to (ZC) do not have a structure in which adjacent hydroxyl groups are oriented in opposite directions on the protective layer, but all have an arrangement that makes them more likely to interact with active sites on the protective layer, making them more likely to participate in interactions with the protective layer but less likely to participate in intermolecular interactions.

[0387] Compound (ZA) contains six hydroxyl groups but does not contain the hydroxyl group of an erythritol structure. For this reason, it is believed that the large number of hydroxyl groups makes the surface free energy of the fluorine-containing ether compound too high, making the lubricating layer using the fluorine-containing ether compound more susceptible to absorbing chemical substances from the environment, resulting in a result of D in the chemical resistance test.

[0388] Furthermore, compounds (ZB) and (ZC) each contain four hydroxyl groups, but do not contain a hydroxyl group of an erythritol structure. Therefore, it is believed that the hydroxyl groups contained in compounds (ZB) and (ZC) are both likely to be involved in interactions with the protective layer, and that the hydroxyl groups involved in intermolecular interactions are insufficient, resulting in a result of D in the spin-off property test.

[0389] In addition, the compound (ZD) used in Comparative Example 4 and the compound (ZE) used in Comparative Example 5 each have a 1,2-diol structure (—O—CH ２ -CH(OH)-CH ２ OH) is arranged. In a fluorine-containing ether compound having a 1,2-diol structure arranged at the terminal, the two hydroxyl groups in the 1,2-diol structure are each able to move sufficiently compared to the hydroxyl groups in the erythritol structure, and therefore the surface free energy is less likely to decrease. For this reason, it is believed that a lubricating layer using a fluorine-containing ether compound is more likely to absorb chemicals from the environment, and that this is why the results of the chemical resistance test were C. In addition, because the terminal groups of compounds (ZD) and (ZE) are highly flexible, the hydroxyl groups contained in the compounds are more likely to form intramolecular interactions. As a result, there is a shortage of hydroxyl groups involved in intermolecular interactions, and it is believed that this is why the results of the spin-off property test were C.

[0390] 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 chemical resistance and can suppress spin-off even if it is thin.

[0391] REFERENCE SIGNS LIST 10 magnetic recording medium 11 substrate 12 adhesive layer 13 soft magnetic layer 14 first underlayer 15 second underlayer 16 magnetic layer 17 protective layer 18 lubricating layer

Claims

1. A fluorine-containing ether compound represented by the following formula (1): １ -CH ２ -R ２ [-CH ２ -R ３ -CH ２ -R ２ ] ｘ -CH ２ -R ４ (1) (In formula (1), x represents an integer of 0 to 2. R ２ is a perfluoropolyether chain. When x is 1 or 2, (x+1) R ２ may be the same in part or in whole, or may be different from each other. ３ is a divalent linking group having 1 to 4 polar groups. When x is 2, two R ３ may be the same or different. １ and R ４ R is each independently a terminal group having 1 to 4 polar groups and 1 to 50 carbon atoms. １ and R ４ At least one of the above is a terminal group represented by the following formula (2): (In formula (2), a represents an integer of 0 to 2, and b represents an integer of 1 to 6. A represents an organic group having 1 to 30 carbon atoms which may contain at least one of a polar group, a halogeno group, and an ether oxygen atom, or a hydrogen atom. However, the total number of polar groups contained in formula (2) is 2 to 4. When a is 2, the two b's may be the same or different.) 2. The fluorine-containing ether compound according to claim 1, wherein the terminal group represented by the formula (2) is any one of the following formulae (2-1) to (2-6): (In formula (2-1), c represents an integer of 1 to 6. X represents any one of a hydroxyl group, an acetamide group, a carboxamide group, or a cyano group.) (In formula (2-2), a1 represents 0 or 1. b1 represents an integer of 1 to 6. d represents an integer of 1 to 4.) (In formula (2-3), a2 represents 0 or 1. b2 represents an integer of 1 to 6. e represents an integer of 0 to 7.) (In formula (2-4), a3 represents 0 or 1. b3 represents an integer of 1 to 6. f represents an integer of 0 to 6.) (In formula (2-6), f2 represents an integer of 1 to 6.) 3. R ​​in the above formula (1) １ and R ４ The fluorine-containing ether compound according to claim 1 or 2, wherein each of the following is independently a terminal group represented by formula (2):

4. R in the above formula (1) １ and R ４ The fluorine-containing ether compound according to claim 3 , wherein 5. R in the above formula (1) １ and R ４ The fluorine-containing ether compound according to claim 1 or 2, wherein only one of the above is an end group represented by formula (2), and the other is an end group represented by the following formula (3): (In formula (3), l represents an integer of 1 to 3. l's m each independently represents an integer of 1 to 6. l's n each independently represents an integer of 1 to 6. In one repeating unit, at least one of m and n is 1. B represents an alkyl group which may have only one polar group, an organic group containing a carbon-carbon unsaturated bond which may have only one polar group, or a hydrogen atom.) 6. R in the above formula (1) １ and R ４ The fluorine-containing ether compound according to claim 1 or claim 2, wherein only one of the terminal groups is represented by formula (2), and the other is represented by any one of the following formulas (3-1) to (3-3): (In formula (3-1), p represents 0 or 1. q1, q2, q3, and q4 each independently represent an integer of 1 to 6. When p is 0, the total value of q1 and q4 is 2 to 10. When p is 1, the total value of q1, q2, q3, and q4 is 4 to 10. When p is 1, at least one of q2 and q3 is 1. D represents a polar group, a vinyl group, an ethynyl group, or an aryl group which may have a substituent. However, when D is the aryl group which may have a substituent, the number of polar groups contained in D is 0 or 1.) (In formula (3-2), r represents 0 or 1. s1, s2, and s3 each independently represent an integer of 1 to 6. When r is 1, the total value of s1, s2, and s3 is 3 to 8. When r is 1, at least one of s2 and s3 is 1.) (In formula (3-3), t represents 1 or 2. Each of the five E's independently represents a polar group, an alkoxy group having 1 to 8 carbon atoms, a halogeno group, or a hydrogen atom. However, when the five E's include a polar group, the total number of polar groups among the five E's is 1.) 7. R in the above formula (1) １ and R ４ The fluorine-containing ether compound according to claim 1 or claim 2, wherein only one of the above is an end group represented by formula (2), and the other is an end group represented by the following formula (3-4) or (3-5): (In formula (3-4), g1 represents an integer of 1 to 6. g1 R ａ and R ｂ each independently represents a hydrogen atom or a methyl group.) (In formula (3-5), g2 represents an integer of 1 to 6.) 8. In the formula (1), x is 1 or 2, and x R ３ each independently represents a divalent linking group having 3 to 50 carbon atoms which has 1 to 3 hydroxyl groups and oxygen atoms at both ends bonding to adjacent methylene groups.

9. In the formula (1), x is 1 or 2, and x R ３ are each independently any one selected from the linking groups represented by the following formulas (4-1) to (4-6): In formula (4-1), u1 represents an integer of 0 to 6, and u2 represents an integer of 0 to 6, provided that at least one of u1 and u2 is 0. The oxygen atom at the left terminal of formula (4-1) is R １ The oxygen atom at the right end is bonded to the methylene group on the side of the ４ (In formula (4-2), v represents an integer of 1 to 2. The oxygen atom at the left terminal of formula (4-2) is bonded to the methylene group on the R １ The oxygen atom at the right end is bonded to the methylene group on the side of the ４ (In formula (4-3), w represents an integer of 0 to 6. The oxygen atom at the left terminal of formula (4-3) is bonded to the methylene group on the R １ The oxygen atom at the right end is bonded to the methylene group on the side of the ４ (In formula (4-4), x1 represents an integer of 0 to 5, and x2 represents an integer of 0 to 5, provided that at least one of x1 and x2 is an integer of 1 to 5. The oxygen atom at the left terminal of formula (4-4) is bonded to the methylene group of R １ The oxygen atom at the right end is bonded to the methylene group on the side of the ４ (In formula (4-5), y1 represents an integer of 1 to 5, and y2 represents an integer of 1 to 5. The oxygen atom at the left terminal of formula (4-5) is bonded to the methylene group on the R １ The oxygen atom at the right end is bonded to the methylene group on the side of the ４ In formula (4-6), z represents an integer of 1 to 6. ｃ and R ｄ Each independently represents a hydrogen atom, a fluorine atom, or a methyl group. The oxygen atom at the left terminal of formula (4-6) 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 10. (x+1) R in the formula (1) ２ are each independently a perfluoropolyether chain represented by the following formula (5): -(CF ２ ) ｗ１ -O-(CF ２ O) ｗ２ -(CF ２ CF ２ O) ｗ３ -(CF ２ CF ２ CF ２ O) ｗ４ -(CF ２ CF ２ CF ２ CF ２ O) ｗ５ -(CF ２ ) ｗ６ In formula (5), w2, w3, w4, and w5 each independently represent an average degree of polymerization, and each independently represent a value of 0 to 20. However, w2, w3, w4, and w5 cannot all be 0 at the same time. w1 and w6 are each independently a value of 0 to 20. ２ is an average value representing the number of repeating units in formula (5), each of which independently represents 1 to 3. ２ O), (CF ２ CF ２ O), (CF ２ CF ２ CF ２ O), (CF ２ CF ２ CF ２ CF ２ There is no particular restriction on the order of arrangement of O).

11. (x+1) R in the formula (1) ２ are each independently any one selected from the perfluoropolyether chains represented by the following formulas (5-1) to (5-4): ２ - (OCF ２ CF ２ ) ｈ - (OCF ２ ) ｉ - OCF ２ - (5-1) (In formula (5-1), h and i represent the average degree of polymerization, 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 - (5-2) (In formula (5-2), j represents an average degree of polymerization and is 1 to 15.) -CF ２ CF ２ CF ２ - (OCF ２ CF ２ CF ２ CF ２ ) ｋ - OCF ２ CF ２ CF ２ (In formula (5-3), k represents the average degree of polymerization and is 1 to 10.) -(CF ２ ) ｗ７ -O-(CF ２ CF ２ CF ２ O) ｗ８ -(CF ２ CF ２ O) ｗ９ -(CF ２ ) ｗ１０ In formula (5-4), 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, each independently representing 1 to 2.) 12. The fluorine-containing ether compound according to claim 1, wherein the fluorine-containing ether compound represented by formula (1) is any one of the fluorine-containing ether compounds represented by the following formulae (AA), (AB), (AI), (AJ), (AN) to (AQ), (AS), (AW), (BA) to (BM), (CA) and (DA). (Rf in formula (AA) １ In the formula (AB), h and i each represent an average degree of polymerization, h is 1 to 20, and i is 0 to 20. ２ In the formula (AI), j represents an average degree of polymerization and is from 1 to 15. １ In the formula (AJ), h and i each represent an average degree of polymerization, h is 1 to 20, and i is 0 to 20. ２ In the formula (AN), j represents an average degree of polymerization and is from 1 to 15. １ In the formula, h and i each represent an average degree of polymerization, h represents 1 to 20, and i represents 0 to 20. (Rf in formula (AO) ２ In the formula (AP), j represents an average degree of polymerization and is from 1 to 15. １ In the formula (AQ), h and i each represent an average degree of polymerization, h is 1 to 20, and i is 0 to 20. ２ In the formula (AS), j represents an average degree of polymerization and is from 1 to 15. ２ In the formula (AW), j represents an average degree of polymerization and is from 1 to 15. ２ In the formula, j represents the average degree of polymerization and is a number ranging from 1 to 15. (Rf in formula (BA) １ In the formula (BB), h and i each represent an average degree of polymerization, h is 1 to 20, and i is 0 to 20. ２ In the formula (BC), j represents an average degree of polymerization and represents 1 to 15. ２ In the formula (BD), j represents an average degree of polymerization and represents 1 to 15. ２ In the formula (BE), j represents an average degree of polymerization and is from 1 to 15. １ In the formula (BF), h and i each represent an average degree of polymerization, h is 1 to 20, and i is 0 to 20. ２ In the formula, j represents the average degree of polymerization and is a number ranging from 1 to 15. (Rf in formula (BG) ２ In the formula (BH), j represents an average degree of polymerization and is from 1 to 15. ２ In the formula (BI), j represents an average degree of polymerization and is from 1 to 15. ２ In the formula (BJ), j represents an average degree of polymerization and represents 1 to 15. ２ In the formula (BK), j represents an average degree of polymerization and is from 1 to 15. ２ In the formula (BL), j represents an average degree of polymerization and is from 1 to 15. ２ In the formula (BM), j represents an average degree of polymerization and is from 1 to 15. ２ In the formula, j represents the average degree of polymerization and is a number ranging from 1 to 15. (Two Rf in formula (CA) １ In the formula, h and i each represent an average degree of polymerization, h being 1 to 20, and i being 0 to 20. １ In formula (DA), h and i may be the same or different. ２ In the formula, j represents the average degree of polymerization and is a number ranging from 1 to 15.

13. The fluorine-containing ether compound according to claim 1 or 2, which has a number average molecular weight in the range of 500 to 10,000.

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

15. A magnetic recording medium comprising at least a magnetic layer, a protective layer, and a lubricating layer provided in that order on a substrate, the lubricating layer comprising the fluorine-containing ether compound according to claim 1 or 2.

16. The magnetic recording medium according to claim 15, wherein the average thickness of the lubricating layer is 0.5 nm to 2.0 nm.

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