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

Abstract

This fluorine-containing ether compound is represented by the following formula. R1-CH2-R2[-CH2-R3-CH2-R2]x-CH2-R4 (x represents an integer of 1 or 2, R2 represents a perfluoropolyether chain, at least one of the x-number of R3 is represented by formula (2-1) or (2-2), and R1 and R4 are each a terminal group which has 2-4 polar groups, in which the number of carbon atoms located at the shortest distance for carbon atoms bound to adjacent ones of the polar groups is 1-9, and which has an oxygen atom to be bound to a methylene group that is bound to R2.)

Description

[Technical Field]

[0001] The present invention relates to a fluorine-containing ether compound, a lubricant for a magnetic recording medium, and a magnetic recording medium. This application claims priority based on Japanese Patent Application No. 2022-122139, filed on July 29, 2022, the contents of which are incorporated herein by reference. [Background technology]

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

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

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

[0005] Furthermore, Patent Documents 3 to 5 disclose fluorine-containing ether compounds having a skeleton containing a methylene group (-CH2-) and a group in which one hydrogen atom of the methylene group is substituted with a hydroxyl group (-CH(OH)-), in which two perfluoropolyether chains are linked via a divalent linking group having two hydroxyl groups, and in which terminal groups that are organic groups having polar groups are linked to both ends of the skeleton via the methylene groups.

[0006] Patent Document 6 discloses a fluorine-containing ether compound having a skeleton containing a methylene group (-CH2-) and a group in which one hydrogen atom of the methylene group is substituted with a hydroxyl group (-CH(OH)-), in which two or three perfluoropolyether chains are linked via a divalent linking group having two hydroxyl groups, and in which terminal groups that are organic groups having polar groups are linked to both ends of the skeleton via the methylene groups.

[0007] Furthermore, Patent Documents 7 and 8 disclose fluorine-containing ether compounds which have a skeleton containing a methylene group (-CH-) and a group in which one hydrogen atom of the methylene group is substituted with a hydroxyl group (-CH(OH)-), and in which three perfluoropolyether chains are linked via a divalent linking group having one hydroxyl group, and on both sides of the skeleton are linked via methylene groups terminal groups which are organic groups having a hydroxyl group or a polar group. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] U.S. Patent No. 10,540,997 [Patent Document 2] International Publication No. 2021 / 251335 [Patent Document 3] International Publication No. 2021 / 020066 [Patent Document 4] Patent No. 6804981 [Patent Document 5] Patent No. 5743438 [Patent Document 6] U.S. Patent No. 10,262,685 [Patent Document 7] International Publication No. 2018 / 116742 [Patent Document 8] International Publication No. 2017 / 145995 Summary of the Invention [Problem to be solved by the invention]

[0009] In magnetic recording and reproducing devices, there is a demand for an even smaller flying height of the magnetic head. However, generally, when the flying height of the magnetic head is reduced, the magnetic head and the substrate are more likely to collide with each other. That is, the flying stability of the magnetic head tends to decrease. Furthermore, when the flying height of the magnetic head is reduced, pickup may occur in which the fluorine-containing ether compound in the lubricating layer adheres to the magnetic head.

[0010] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a fluorine-containing ether compound which can form a lubricating layer that has excellent floating stability and can suppress pickup, and which can be suitably used as a material for a lubricant for a magnetic recording medium. Another object of the present invention is to provide a lubricant for magnetic recording media which contains the fluorine-containing ether compound of the present invention and is capable of forming a lubricating layer having good flying stability and a high pick-up suppression effect. Another object of the present invention is to provide a magnetic recording medium having a lubricating layer containing the fluorinated ether compound of the present invention, which has good flying stability for a magnetic head and a high pick-up suppression effect. [Means for solving the problem]

[0011] The present invention includes the following aspects. A first aspect of the present invention provides the following fluorine-containing ether compound:

[0012] [1] A fluorine-containing ether compound represented by the following formula (1): R1 -CH2-R 2 [-CH2-R 3 -CH2-R 2 ] x -CH2-R 4 (1) (In formula (1), x represents an integer of 1 to 2; R 2 is a perfluoropolyether chain; (x+1) R 2 may be the same in part or in whole, or may be different from each other; R 3 is a divalent linking group having a hydroxyl group; x R 3 At least one of the R 3 may be the same or different; R 1 and R 4 is a terminal group having 2 to 4 polar groups, and the number of carbon atoms in the shortest distance between carbon atoms bonding to adjacent polar groups is 1 to 9; R 2 is a terminal group having an oxygen atom bonded to a methylene group bonded to R 1 and R 4 may be the same or different.)

[0013] [ka] (In formula (2-2), l represents an integer of 1 to 2.)

[0014] The fluorine-containing ether compound of the first aspect of the present invention preferably has the characteristics described in the following [2] to [9]. It is also preferable to arbitrarily combine two or more of the characteristics described in the following [2] to [9]. [2] R in the formula (1) 1 and R 4 each independently contain at least one polar group selected from the group consisting of a hydroxyl group, a cyano group, and a group having an amide bond. [3] R in the formula (1) 1 and R4 are each independently a terminal group represented by any one of the following formulas (3-1) to (3-4):

[0015] [ka] (In formula (3-1), p represents an integer of 0 to 3, r represents an integer of 1 to 5, and the total value of p and r is 1 to 5; q represents an integer of 0 to 2; and A represents a polar group.) (In formula (3-2), s represents an integer of 0 to 2, and t represents an integer of 1 to 5.) (In formula (3-3), u represents an integer of 2 to 4; Y represents a linear alkylene group which may have ether oxygen or a single bond; when Y is the alkylene group, the total number of carbon atoms and oxygen atoms contained in Y is 1 to 5.) (In formula (3-4), v represents an integer of 1 to 3; B represents a polar group in which a hydrogen atom at any position on the benzene ring is substituted.)

[0016] [4] R in the formula (1) 1 and the polar group R 4 The fluorine-containing ether compound according to any one of [1] to [3], wherein the total number of polar groups contained in the above is 4 to 6. [5] R in the formula (1) 1 and R 4 The fluorine-containing ether compound according to any one of [1] to [4], wherein [6] x R in the formula (1) 3 At least one of the fluorine-containing ether compounds is represented by the formula (2-1) above, and is the fluorine-containing ether compound according to any one of [1] to [5].

[0017] [7] (x+1) R in the formula (1) 2 are each independently a perfluoropolyether chain represented by the following formula (4): -(CF2) w1 -O-(CF2O) w2 -(CF2CF2O) w3-(CF2CF2CF2O) w4 -(CF2CF2CF2CF2O) w5 -(CF2) w6 - (4) (In formula (4), w2, w3, w4, and w5 represent the average degree of polymerization and each independently represent 0 to 20; provided that w2, w3, w4, and w5 cannot all be 0 at the same time; w1 and w6 represent the average value representing the number of CF2 and each independently represent 1 to 3; there are no particular limitations on the arrangement order of the repeating units (CF2O), (CF2CF2O), (CF2CF2CF2O), and (CF2CF2CF2CF2O) in formula (4).)

[0018] [8] (x+1) R in the formula (1) 2 are each independently any one selected from perfluoropolyether chains represented by the following formulae (4-1) to (4-4): -CF2-(OCF2CF2) h -(OCF2) i -OCF2- (4-1) (In formula (4-1), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20.) -CF2CF2-(OCF2CF2CF2) j -OCF2CF2- (4-2) (In formula (4-2), j represents the average degree of polymerization and represents 1 to 15.) -CF2CF2CF2-(OCF2CF2CF2CF2) k -OCF2CF2CF2- (4-3) (In formula (4-3), k represents the average degree of polymerization and represents 1 to 10.) -(CF2) w7 -O-(CF2CF2CF2O) w8 -(CF2CF2O) w9 -(CF2) w10 - (4-4) (In formula (4-4), w8 and w9 represent the average degree of polymerization, each independently representing 1 to 20; w7 and w10 represent the average number of CF2, each independently representing 1 to 2.)

[0019] [9] The fluorinated ether compound according to any one of [1] to [8], which has a number average molecular weight in the range of 500 to 10,000. A second aspect of the present invention provides the following lubricant for a magnetic recording medium.

[10] A lubricant for magnetic recording media, comprising the fluorine-containing ether compound according to any one of [1] to [9].

[0020] A third aspect of the present invention provides the following magnetic recording medium.

[11] A magnetic recording medium having at least a magnetic layer, a protective layer, and a lubricating layer sequentially provided on a substrate, A magnetic recording medium, wherein the lubricating layer contains the fluorine-containing ether compound according to any one of [1] to [9]. The magnetic recording medium according to the third aspect of the present invention preferably has the characteristics described in

[12] below.

[12] The magnetic recording medium according to

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

[0021] The fluorine-containing ether compound of the present invention is a compound represented by the above formula (1), and is suitable as a material for a lubricant for a magnetic recording medium. The lubricant for magnetic recording media of the present invention contains the fluorine-containing ether compound of the present invention, and therefore can form a lubricating layer that has good flying stability and a high pick-up suppressing effect.

[0022] 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 floating stability of the magnetic head, a high pick-up suppression effect, and excellent reliability and durability.In addition, the magnetic recording medium of the present invention has good floating stability of the magnetic head and a lubricating layer that can suppress pick-up, so the floating amount of the magnetic head can be further reduced. [Brief explanation of the drawings]

[0023] [Figure 1]1 is a schematic cross-sectional view showing an embodiment of a magnetic recording medium of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0024] In order to solve the above problems, the present inventors have conducted extensive research as described below. Conventionally, as a material for a lubricant for magnetic recording media (hereinafter sometimes abbreviated as "lubricant") to be applied to the surface of a protective layer, a fluorine-containing ether compound having a chain structure containing multiple perfluoropolyether chains and having adsorption sites with polar groups located at the ends of the chain structure and between the perfluoropolyether chains has been preferably used. The adsorption sites in the fluorine-containing ether compound bond with active sites on the protective layer, improving the adhesion of the lubricating layer to the protective layer.

[0025] However, when a thin lubricating layer is formed on a protective layer using a conventional lubricant, it is difficult to achieve a lubricating layer that provides good flying stability for the magnetic head and is less susceptible to pickup, as will be described below. That is, the vicinity of the adsorption site in the fluorine-containing ether compound contained in the lubricating layer that does not interact with the active site on the protective layer floats up and forms agglomerates, reducing the smoothness of the lubricating layer. The agglomerates formed by the floating fluorine-containing ether compound in the lubricating layer collide with the magnetic head, causing a reduction in flying stability.

[0026] Furthermore, the fluorine-containing ether compound contained in the lubricating layer has adsorption sites that do not interact with the active sites on the protective layer, and these adsorption sites are adsorbed to the magnetic head that flies nearby.The fluorine-containing ether compound is then picked up and adhered to the magnetic head starting from the adsorption sites adsorbed to the magnetic head, causing pickup.

[0027] Therefore, the present inventors focused on the adsorption sites of the fluorine-containing ether compound contained in the lubricating layer that can interact with the active sites on the protective layer, and conducted extensive research as described below in order to realize a fluorine-containing ether compound that is less likely to produce adsorption sites in the lubricating layer that are not involved in the interaction with the active sites on the protective layer. The present inventors first investigated the arrangement of a plurality of adsorption sites capable of interacting with the active sites on the protective layer of the fluorine-containing ether compound, and the strength of the interaction of each adsorption site with the active sites on the protective layer.

[0028] As a result, it was found that it is necessary to arrange an adsorption site (hereinafter sometimes referred to as "terminal adsorption site") at each end of a chain structure containing multiple perfluoropolyether chains, and to arrange an adsorption site (hereinafter sometimes referred to as "central adsorption site") between at least one adjacent perfluoropolyether chain, so that the balance between the strength of the interaction between the terminal adsorption site and the active site on the protective layer and the strength of the interaction between the central adsorption site and the active site on the protective layer is appropriate, and the terminal adsorption site and the central adsorption site can interact with the active site on the protective layer with sufficient strength.

[0029] That is, if the interaction between the terminal adsorption site and the active site on the protective layer is too strong compared to the interaction between the central adsorption site and the active site on the protective layer, there will be insufficient active sites on the protective layer with which the central adsorption site can interact, resulting in a central adsorption site that is not involved in the interaction with the active site on the protective layer. As a result, the area near the central adsorption site will float and form a mass, reducing the smoothness of the lubricating layer and decreasing the flying stability. Furthermore, if the interaction between the central adsorption site and the active site on the protective layer is too strong compared to the interaction between the terminal adsorption site and the active site on the protective layer, there will be insufficient active sites on the protective layer with which the terminal adsorption site can interact, resulting in a terminal adsorption site that is not involved in the interaction with the active site on the protective layer. In this case, the area near the terminal adsorption site will float and adsorb to the magnetic head flying near the terminal adsorption site on the lubricating layer, causing pickup.

[0030] Therefore, the inventors have conducted extensive research into the structures of terminal adsorption sites and central adsorption sites that can interact with the active sites on the protective layer with sufficient strength, and that have an appropriate balance between the strength of the interaction between the terminal adsorption sites and the active sites on the protective layer and the strength of the interaction between the central adsorption sites and the active sites on the protective layer. As a result, it was found that a fluorine-containing ether compound having, as a terminal adsorption site, a terminal group having 2 to 4 polar groups, where the number of carbon atoms along the shortest distance between carbon atoms to which adjacent polar groups are bonded is 1 to 9, and an oxygen atom bonded to a methylene group bonded to a perfluoropolyether chain, and a divalent linking group represented by formula (2-1) or (2-2) as a central adsorption site, is sufficient.

[0031] The divalent linking group represented by formula (2-1) or (2-2) is a highly flexible divalent linking group having two or three hydroxyl groups. More specifically, since the perfluoropolyether chain has a sterically bulky skeleton, the hydroxyl groups of the divalent linking groups arranged between adjacent perfluoropolyether chains are likely to be inhibited from adsorbing to the protective layer by the perfluoropolyether chains arranged on both sides of the divalent linking group.

[0032] For example, when a divalent linking group having only one hydroxyl group is arranged as the central adsorption site instead of the divalent linking group represented by formula (2-1) or (2-2), the perfluoropolyether chains arranged on both sides of the divalent linking group may inhibit the adsorption of the hydroxyl group to the protective layer, and the divalent linking group may not be able to participate in the interaction with the active site on the protective layer.

[0033] Furthermore, when a divalent linking group having a rigid structure is arranged as the central adsorption site, even if the divalent linking group has multiple hydroxyl groups, it may not be able to participate in the interaction with the active site on the protective layer. This is because the divalent linking group having a rigid structure cannot move freely, and when the perfluoropolyether chains arranged on both sides of the divalent linking group undergo molecular movement, it may move in conjunction with the perfluoropolyether chains and move away from the protective layer.

[0034] Furthermore, when a divalent linking group having a chain structure with less than six atoms is arranged as the central adsorption site, the distance between adjacent perfluoropolyether chains becomes short, which makes it more likely that the adsorption of the hydroxyl groups of the divalent linking group to the protective layer is inhibited by the perfluoropolyether chain, making it even more difficult for the hydroxyl groups of the divalent linking group to be adsorbed to the protective layer.

[0035] In contrast, in the above-mentioned fluorine-containing ether compound, a divalent linking group represented by formula (2-1) or (2-2) is arranged as a central adsorption site between at least one of adjacent perfluoropolyether chains. The divalent linking group represented by formula (2-1) or (2-2) has two or three hydroxyl groups and has six or more atoms forming a chain structure. Moreover, the divalent linking group represented by formula (2-1) or (2-2) has three or four carbon atoms arranged between oxygen atoms forming ether bonds in the chain structure, and both ends are bonded to the perfluoropolyether chain via methylene groups by ether bonds. Therefore, it has moderate flexibility.

[0036] Therefore, in the above-mentioned fluorine-containing ether compound, the divalent linking group represented by formula (2-1) or (2-2) arranged as the central adsorption site ensures sufficient distance between adjacent perfluoropolyether chains, so that the adsorption of the hydroxyl groups of the divalent linking group to the protective layer is less likely to be hindered by the perfluoropolyether chain. Furthermore, even if the adsorption of one hydroxyl group of the divalent linking group to the protective layer is hindered by the bulkiness of the perfluoropolyether chains arranged on both sides of the divalent linking group represented by formula (2-1) or (2-2), the other one or two hydroxyl groups can be adsorbed onto the protective layer. Moreover, because the divalent linking group represented by formula (2-1) or (2-2) has sufficient flexibility, even if the perfluoropolyether chains arranged on both sides of the divalent linking group undergo molecular motion, they can move freely and independently without interlocking with the perfluoropolyether chain. Therefore, the interaction between the divalent linking group represented by formula (2-1) or (2-2) and the active site on the protective layer is less affected by the molecular motion of the perfluoropolyether chains located on both sides of the divalent linking group. Therefore, the divalent linking group represented by formula (2-1) or (2-2), which is the central adsorption site, is more likely to be involved in the interaction with the active site on the protective layer.

[0037] However, even in a fluorine-containing ether compound in which a divalent linking group represented by formula (2-1) or (2-2) is arranged as a central adsorption site between at least one of adjacent perfluoropolyether chains, in a fluorine-containing ether compound in which terminal groups each having 2 to 4 polar groups are bonded to both ends of a chain structure containing multiple perfluoropolyether chains, the number of carbon atoms along the shortest distance between carbon atoms to which adjacent polar groups are bonded is 1 to 9, and the terminal groups are not terminal groups having an oxygen atom bonded to a methylene group bonded to the perfluoropolyether chain, the terminal groups may not be able to participate in the interaction with the active sites on the protective layer.

[0038] This is presumably because the number of active sites on the protective layer that can interact with the fluorinated ether compound is limited. That is, since a divalent linking group represented by formula (2-1) or (2-2), which can strongly interact with the active sites on the protective layer, is arranged as the central adsorption site, the central adsorption site tends to interact with the active sites on the protective layer preferentially over the terminal groups. As a result, it is presumed that the terminal groups, which have weaker adsorption power with the active sites on the protective layer than the central adsorption site, are less likely to participate in the interaction with the active sites on the protective layer.

[0039] In contrast, in a fluorine-containing ether compound in which the above-mentioned terminal groups are arranged as terminal adsorption sites and a divalent linking group represented by formula (2-1) or (2-2) is arranged as a central adsorption site, the terminal adsorption site has two to four polar groups, the distance between adjacent polar groups is appropriate, and the terminal group forms an ether bond with a methylene group bonded to the perfluoropolyether chain. Therefore, the two to four polar groups contained in the terminal adsorption sites are less affected by the interaction between adjacent polar groups and can fully exert their adsorptive power to the protective layer. Therefore, even if a divalent linking group represented by formula (2-1) or (2-2) is arranged as the central adsorption site, the terminal adsorption site can interact with the active site on the protective layer.

[0040] Therefore, in a lubricating layer containing a fluorine-containing ether compound in which the terminal adsorption sites are terminal groups having 2 to 4 polar groups, the number of carbon atoms in the shortest distance between the carbon atoms to which adjacent polar groups are bonded is 1 to 9, and the terminal groups have an oxygen atom bonded to a methylene group bonded to a perfluoropolyether chain, and the central adsorption site is a divalent linking group represented by formula (2-1) or (2-2), the balance between the strength of the interaction between the terminal adsorption site and the active site on the protective layer and the strength of the interaction between the central adsorption site and the active site on the protective layer is appropriate, and adsorption sites that are not involved in the interaction with the active site on the protective layer are unlikely to occur in the fluorine-containing ether compound. As a result, <1> ~ <3> It is estimated that the following effects can be obtained.

[0041] <1> This can prevent a decrease in the smoothness of the lubricating layer caused by a portion of the fluorine-containing ether compound floating up and forming agglomerates, and can form a lubricating layer that provides good flying stability. <2> The adsorption sites in the fluorine-containing ether compound that are not involved in the interaction with the active sites on the protective layer can be prevented from being adsorbed to the magnetic head flying near the adsorption sites, thereby forming a lubricating layer that is less likely to cause pickup originating from the adsorption sites adsorbed to the magnetic head.

[0042] <3> The central adsorption site and the terminal adsorption site of the fluorine-containing ether compound interact with the active sites on the protective layer, thereby obtaining a good adsorption force to the protective layer. Therefore, even if an adsorption site not involved in the interaction with the active sites on the protective layer is adsorbed to the magnetic head, the fluorine-containing ether compound is unlikely to be picked up by the magnetic head from the adsorption site adsorbed to the magnetic head, thereby suppressing pickup.

[0043] Furthermore, the present inventors have confirmed that by using a lubricant containing the above-mentioned fluorine-containing ether compound, a lubricating layer having good flying stability and a high pick-up suppression effect can be formed, and have arrived at the present invention.

[0044] Preferred examples of the fluorine-containing ether compound, lubricant for magnetic recording media, and magnetic recording media of the present invention will be described in detail below. Note that the present invention is not limited to the following embodiments. The present invention allows addition, omission, substitution, and modification of the number, amount, position, ratio, material, configuration, etc., within the scope of the present invention.

[0045] [Fluorine-containing ether compounds] The fluorine-containing ether compound of the present embodiment is represented by the following formula (1). R 1 -CH2-R 2 [-CH2-R 3 -CH2-R 2 ] x -CH2-R 4 (1) (In formula (1), x represents an integer of 1 to 2; R2 is a perfluoropolyether chain; (x+1) R 2 may be the same in part or in whole, or may be different from each other; R 3 is a divalent linking group having a hydroxyl group; x R 3 At least one of the R 3 may be the same or different; R 1 and R 4 is a terminal group having 2 to 4 polar groups, and the number of carbon atoms in the shortest distance between carbon atoms bonding to adjacent polar groups is 1 to 9; R 2 is a terminal group having an oxygen atom bonded to a methylene group bonded to R 1 and R 4 may be the same or different.)

[0046] [ka] (In formula (2-2), l represents an integer of 1 to 2.)

[0047] The fluorine-containing ether compound of the present embodiment is, as represented by formula (1), 3 and a divalent linking group represented by R 2 The PFPE chain has a skeleton in which the PFPE chain is connected to the R 1 The other end of the skeleton is connected via a methylene group to an end group represented by R 4 The terminal group shown in is attached.

[0048] In the fluorine-containing ether compound represented by formula (1), x represents an integer of 1 to 2. In the fluorine-containing ether compound represented by formula (1), x represents an integer of 1 to 2, and therefore, R 2 The number of PFPE chains (x+1) represented by R is 2 or 3. 2Unlike the compound with one PFPE chain, 2 R in between 3 A divalent linking group having a hydroxyl group represented by the formula: 2 In comparison with a compound having one PFPE chain, a lubricating layer having excellent adhesion to the protective layer can be obtained. 2 Compared with compounds having four or more PFPE chains, the molecules are not too large and can move freely. Therefore, it is easy to wet and spread on the protective layer, and it is easy to obtain a lubricating layer with a uniform thickness. In addition, since x is an integer of 1 to 2, R 2 R placed between 3 The number of -R in Eq. (1) is 1 or 2. 2 [-CH2-R 3 -CH2-R 2 ] x The number of hydroxyl groups in - tends to be appropriate, making it easier to obtain a lubricating layer with good adhesion to the protective layer. Furthermore, the fluorine-containing ether compound represented by formula (1) can prevent interactions between polar groups in the molecule, and the polar groups in the fluorine-containing ether compound are less likely to aggregate together, compared to when x is 3 or more, for example. Therefore, a lubricating layer with good flying stability and a high pick-up suppression effect can be formed.

[0049] (R 3 a divalent linking group represented by In the fluorine-containing ether compound represented by formula (1), x R 3 are each independently a divalent linking group having a hydroxyl group. In the fluorine-containing ether compound represented by formula (1), R 3 Since the compound has a hydroxyl group, when a lubricating layer is formed on a protective layer using a lubricant containing the compound, a favorable interaction occurs between the lubricating layer and the protective layer.

[0050] In the fluorine-containing ether compound represented by formula (1), x R 3 At least one of the groups is a divalent linking group represented by formula (2-1) or (2-2). That is, when x is 1, R 3is a linking group represented by formula (2-1) or (2-2). When x is 2, two R 3 One or both of the R 3 is a divalent linking group represented by formula (2-1) or (2-2).

[0051] The divalent linking groups represented by formulas (2-1) and (2-2) each have oxygen atoms at both ends of a chain structure, and are connected to R 3 The divalent linking group represented by formula (2-1) has four carbon atoms between the oxygen atoms forming the ether bond in the chain structure, while the divalent linking group represented by formula (2-2) has three carbon atoms between adjacent oxygen atoms forming the ether bond in the chain structure. The oxygen atoms in the chain structure of the divalent linking groups represented by formulas (2-1) and (2-2) form ether bonds, imparting appropriate flexibility to the fluorine-containing ether compound represented by formula (1) and increasing the affinity between the hydroxyl groups of the divalent linking groups represented by formulas (2-1) and (2-2) and the protective layer. Furthermore, because the divalent linking groups represented by formulas (2-1) and (2-2) have sufficient flexibility, they can move freely and independently without interlocking with the perfluoropolyether chains even when the perfluoropolyether chains on either side undergo molecular motion. Therefore, the divalent linking group represented by formula (2-1) or (2-2) is less susceptible to the molecular motion of the perfluoropolyether chains bonded to both sides of it via methylene groups, and is more likely to interact with the active sites on the protective layer.

[0052] The divalent linking groups represented by formula (2-1) and (2-2) each have a chain structure with 6 or more atoms. Specifically, the divalent linking group represented by formula (2-1) has a chain structure with 6 atoms. The number of atoms forming the chain structure of the divalent linking group represented by formula (2-2) is 9 when l is 1, and 13 when l is 2. Therefore, in the above-mentioned fluorine-containing ether compound, the divalent linking group represented by formula (2-1) or (2-2) ensures a sufficient distance between adjacent perfluoropolyether chains, and the adsorption of the hydroxyl groups of the divalent linking group to the protective layer is less likely to be inhibited by the perfluoropolyether chain.

[0053] The divalent linking group represented by formula (2-1) has two hydroxyl groups. The divalent linking group represented by formula (2-2) has two or three hydroxyl groups. Since the divalent linking group represented by formula (2-1) or (2-2) has two or more hydroxyl groups, the lubricating layer containing the fluorine-containing ether compound has good adhesion (adhesion) to the protective layer. That is, even if one hydroxyl group in formula (2-1) or (2-2) is prevented from adsorbing to the protective layer due to the bulkiness of the adjacent perfluoropolyether chains, the other one or two hydroxyl groups can be adsorbed onto the protective layer. Moreover, since the number of hydroxyl groups in the divalent linking group is three or less, in a magnetic recording medium having a lubricating layer containing a fluorine-containing ether compound, R 1 and R 4 This can prevent the occurrence of adsorption sites that are not involved in the interaction with the active sites on the protective layer due to a lack of active sites on the protective layer that can interact with the terminal groups represented by the formula (I). Therefore, it is possible to prevent pickup caused by the vicinity of the adsorption sites that are not involved in the interaction with the active sites on the protective layer floating up and adhering to the magnetic head flying above the lubricating layer. The number of hydroxyl groups in the divalent linking group is preferably two, as this can more effectively prevent pickup.

[0054] In the divalent linking group represented by formula (2-1), the carbon atoms to which the two hydroxyl groups in formula (2-1) are bonded are directly bonded. Therefore, the two hydroxyl groups in formula (2-1) can move more flexibly than, for example, when the carbon atoms to which the hydroxyl groups are bonded are bonded via a rigid alkylene chain consisting of multiple methylene groups. Therefore, even if the perfluoropolyether chains arranged on both sides undergo molecular motion, the two hydroxyl groups in the divalent linking group represented by formula (2-1) can move freely and independently, and the interaction between the hydroxyl groups in the divalent linking group and the protective layer is easily maintained.

[0055] Furthermore, in the divalent linking group represented by formula (2-1), the two hydroxyl groups are close to each other, so the orientation of the two hydroxyl groups in the same direction relative to the alkylene chain containing the carbon atom to which these hydroxyl groups are bonded is restricted. In other words, the two hydroxyl groups contained in the divalent linking group represented by formula (2-1) tend to be oriented in different directions relative to the alkylene chain containing the carbon atom to which these hydroxyl groups are bonded. Therefore, the dipoles induced by the two hydroxyl groups are roughly opposite in direction. This reduces the sum of the dipole moments in the divalent linking group represented by formula (2-1), thereby reducing the surface free energy of the fluorine-containing ether compound. As a result, a lubricating layer containing a fluorine-containing ether compound is less likely to absorb chemical pollutants in the environment and has excellent chemical resistance, making it preferable.

[0056] The divalent linking group represented by formula (2-2) includes a structure in which two to three glycerin structures (-O-CH2-CH(OH)-CH2-) are linked together. Because glycerin structures are flexible, the structure represented by formula (2-2) in which two to three of these are linked together is extremely flexible, allowing the hydroxyl groups to move flexibly. Therefore, even when the perfluoropolyether chains arranged on both sides undergo molecular motion, the two to three hydroxyl groups in the divalent linking group represented by formula (2-2) can move independently and freely, making it easy to maintain the interaction between the hydroxyl groups in the divalent linking group and the protective layer.

[0057] In formula (2-2), l represents an integer of 1 to 2. When l is 1, the number of hydroxyl groups in the divalent linking group represented by formula (2-2) is 2. Therefore, the central portion (-R 2 [-CH2-R 3 -CH2-R 2 ] x The interaction between the terminal part (R 1 -CH2- and -CH2-R 4 Therefore, the occurrence of pick-up due to the lifting of the terminal portion of the fluorine-containing ether compound can be further suppressed, and the fluorine-containing ether compound can form a lubricating layer.

[0058] When l in formula (2-2) is 2, the number of hydroxyl groups in the divalent linking group represented by formula (2-2) is 3. Therefore, the central portion (-R 2 [-CH2-R 3 -CH2-R 2 ] x As a result, the central portion of the compound represented by formula (1) is prevented from separating from the protective layer and floating up, maintaining the smoothness of the lubricating layer and improving flying stability.

[0059] In the fluorine-containing ether compound represented by formula (1), x is 2 and two R 3 When only one of the R groups is a divalent linking group represented by formula (2-1) or (2-2), the R group that is not a divalent linking group represented by formula (2-1) or (2-2) 3 is a divalent linking group having a hydroxyl group. R that is not a divalent linking group represented by formula (2-1) or (2-2) 3 has oxygen atoms at both ends and is connected to R 3 It is preferable that the R that is not the divalent linking group represented by formula (2-1) or (2-2) is bonded to a methylene group bonded to a divalent linking group represented by formula (2-3). 3The number of hydroxyl groups that R has can be, for example, 1 to 3, and is preferably 1 or 2. The R that is not a divalent linking group represented by formula (2-1) or (2-2) 3 Examples of such structures include a glycerin structure (-O-CH2-CH(OH)-CH2-O-).

[0060] In formula (1), x is 2 and two R 3 are both divalent linking groups represented by formula (2-1) or (2-2), two R 3 may be the same or different. 3 When the two R are the same, the coating state of the fluorine-containing ether compound on the protective layer becomes more uniform, and a lubricating layer with better adhesion can be formed. 3 is the same, the fluorine-containing ether compound can be easily produced, which is preferable.

[0061] (R 1 and R 4 (end group indicated by In the fluorine-containing ether compound represented by formula (1), R 1 and R 4 is a terminal group having 2 to 4 polar groups, and the number of carbon atoms in the shortest distance between carbon atoms bonding to adjacent polar groups is 1 to 9; R 2 It is a terminal group having an oxygen atom bonded to a methylene group (-CH2-) which is bonded to In this embodiment, R 1 and R 4 are the above-mentioned terminal groups, a lubricating layer containing a fluorine-containing ether compound represented by formula (1) has good flying stability and a high pick-up suppressing effect.

[0062] More specifically, R 1 and R 4Since the number of polar groups contained in each of R is two or more, when a lubricating layer is formed on a protective layer using a lubricant containing a fluorine-containing ether compound, a favorable interaction occurs between the lubricating layer and the protective layer. As a result, the lubricating layer has excellent adhesion to the protective layer and a high pick-up suppression effect. In addition, R 1 and R 4 Since the number of polar groups contained in each of R is 4 or less, it is possible to prevent the polarity of the fluorine-containing ether compound in the lubricating layer containing the fluorine-containing ether compound from being too high, causing the fluorine-containing ether compound to aggregate and form clumps, which would result in the loss of smoothness of the lubricating layer. 1 and R 4 The number of polar groups contained in each of R is preferably 3 or less, and most preferably 2, in order to make the fluorine-containing ether compound less susceptible to aggregation. 1 and R 4 When the number of polar groups contained in each of R 1 and R 4 As a result, aggregation of polar groups contained in the terminal groups of R can be effectively suppressed. 1 and R 4 This can prevent the particles from floating up and forming lumps, and the resulting fluorine-containing ether compound can form a lubricating layer with good flying stability.

[0063] R 1 and R 4 may be the same or different. 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.

[0064] R in Equation (1) 1 and the polar group R 4The total number of polar groups contained in the aryl group is 4 to 8, preferably 4 to 6, more preferably 4 or 5, and most preferably 4. When the total number of the polar groups is 4 or more, R 1 and R 4 This strengthens the interaction between the polar group of the protective layer and the R 1 and R 4 The terminal group consisting of the compound is separated from the protective layer, and the fluorine-containing ether compound is prevented from migrating from this portion to the magnetic head. Therefore, the fluorine-containing ether compound provides a lubricating layer with a high pick-up suppression effect.

[0065] In addition, when the total number of the polar groups is 6 or less, the polar groups that are not involved in the bond between the lubricating layer and the active sites on the protective layer are less likely to be generated.Therefore, the polar groups that are not involved in the bond between the lubricating layer and the active sites on the protective layer aggregate to form protrusions, which can prevent collisions with the magnetic head.Therefore, it is possible to form a lubricating layer with better flying stability, which is preferable.

[0066] Also, R 1 and R 4 In R, the number of carbon atoms in the shortest distance between carbon atoms bonded to adjacent polar groups is 1 to 9. 1 and R 4 Each polar group in R is bonded to a different carbon atom, and the carbon atoms bonded to the polar groups are bonded to each other via a linking group containing 1 to 9 carbon atoms not bonded to a polar group. 1 and R 4 The terminal polar group and the polar group adjacent to the terminal polar group can be oriented in such a way that they can adhere to the protective layer by the linking group containing a carbon atom to which the polar group is not bonded. 1 and R 4 It is presumed that the terminal groups shown by the formula (I) are unlikely to float up and form lumps, resulting in excellent floating stability. R 1and R 4 In the formula (I), an atom other than carbon atoms may be present between the carbon atoms to which adjacent polar groups are bonded. Examples of the atom other than carbon atoms include an oxygen atom and a nitrogen atom.

[0067] Also, R 1 and R 4 is R 2 It is a terminal group having an oxygen atom bonded to a methylene group (-CH2-) that is bonded to R 1 and R 4 is R 1 and R 4 Each of these has an oxygen atom at the end that bonds to the adjacent CH2. 1 and R 4 The oxygen atom located at the end of R forms an ether bond (-O-) with the atoms bonded on both sides of it. This ether bond provides the fluorine-containing ether compound represented by formula (1) with appropriate flexibility, and 1 and R 4 This increases the affinity between the polar group in the terminal group represented by formula (1) and the protective layer. As a result, the fluorine-containing ether compound represented by formula (1) can form a lubricating layer that has excellent adhesion to the protective layer.

[0068] R 1 and R 4 The polar groups contained in the hydroxyl group (-OH), amino group (-NH2), carboxyl group (-COOH), formyl group (-(C=O)H), carbonyl group (-CO-), sulfo group (-SO3H), cyano group (-CN), and groups with an amide bond (-NR 7 COR 8 or -CONR 9 R 10 ;R 7 , R 8 , R 9 and R 10 are each independently a hydrogen atom or an organic group. In the group having an amide bond, the R 7 and R 8 may be bonded to each other to form a ring, and the R 9 and R10 may be bonded to each other to form a ring. 7 , R 8 , R 9 and R 10 are preferably each independently selected from the group consisting of a hydrogen atom, a methyl group, an ethyl group, a propyl group, and a butyl group. As a group having an amide bond, an acetamide group (-NHC(=O)CH3) or a carboxamide group (-C(=O)NH2) is preferred. R 1 and R 4 The 2 to 4 polar groups each have may be partly or entirely the same, or may be different from each other.

[0069] R 1 and R 4 Preferably, R 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. 1 and R 4 More preferably, each of the groups contains at least one hydroxyl group as a polar group. R 1 and R 4 The two to four polar groups each have are preferably polar groups selected from the group consisting of a hydroxyl group, a cyano group, and a group having an amide bond.

[0070] In the fluorine-containing ether compound represented by formula (1), R 1 and R 4 are preferably each independently a terminal group represented by any one of formulas (3-1) to (3-4).

[0071] [ka] (In formula (3-1), p represents an integer of 0 to 3, r represents an integer of 1 to 5, and the total value of p and r is 1 to 5; q represents an integer of 0 to 2; and A represents a polar group.) (In formula (3-2), s represents an integer of 0 to 2, and t represents an integer of 1 to 5.) (In formula (3-3), u represents an integer of 2 to 4; Y represents a linear alkylene group which may have ether oxygen or a single bond; when Y is the alkylene group, the total number of carbon atoms and oxygen atoms contained in Y is 1 to 5.) (In formula (3-4), v represents an integer of 1 to 3; B represents a polar group in which a hydrogen atom at any position on the benzene ring is substituted.)

[0072] R 1 and R 4 is a terminal group represented by any one of formulas (3-1) to (3-4), R 1 and the polar group R 4 The total number of polar groups (R 1 and / or R 4 is the formula (3-1), the number of hydroxyl groups and polar groups A, and R 1 and / or R 4 The number of hydroxyl groups when R is formula (3-2) or formula (3-3) 1 and / or R 4 When the formula (3-4) is a group, the total number of hydroxyl groups and polar groups B is 4 to 8, preferably 4 to 6, more preferably 4 or 5, and most preferably 4.

[0073] In the terminal group represented by formula (3-1), the linking group between the carbon atom to which the polar group A located at the terminal is bonded and the carbon atom to which the hydroxyl group adjacent to the polar group A located at the terminal is bonded contains an oxygen atom forming an ether bond. In formula (3-1), p represents an integer of 0 to 3, r represents an integer of 1 to 5, and the sum of p and r is 1 to 5. Therefore, the linking group has a linear structure consisting of 3 to 7 atoms, including carbon atoms to which the polar group A and the hydroxyl group are not bonded.

[0074] In the terminal group represented by formula (3-1), the linking group contains an oxygen atom forming an ether bond and has a linear structure consisting of three or more atoms, including a carbon atom not bonded to the polar group A and a hydroxyl group, so the distance between the polar group A and the hydroxyl group adjacent to the polar group A is appropriate. This prevents the polar group A from interacting with the hydroxyl group adjacent to the polar group A within the molecule, allowing both the polar group A and the hydroxyl group adjacent to the polar group A to adhere to the protective layer. Furthermore, because the linking group has a linear structure consisting of three or more atoms, molecular mobility is appropriate and intramolecular aggregation is unlikely to occur.

[0075] Furthermore, since the linking group contains an oxygen atom that forms an ether bond and has a linear structure consisting of seven or fewer atoms, including the polar group A and a carbon atom that is not bonded to a hydroxyl group, the linking group does not become too hydrophobic and interfere with adhesion to the protective layer. For these reasons, a lubricating layer containing a fluorine-containing ether compound in which the linking group has a linear structure consisting of 3 to 7 atoms, including a polar group A and a carbon atom that is not bonded to a hydroxyl group, has excellent adhesion to the protective layer, provides excellent flying stability, and has a high pick-up suppression effect.

[0076] In formula (3-1), the total value of p and r is 1 to 5, and preferably 1 to 3. 1 and R 4 In the formula, the carbon atom contained in the linking group arranged between the carbon atoms bonded to the polar groups prevents the intramolecular interaction between adjacent polar groups from occurring in preference to the interaction between the polar groups and the protective layer, and R 1 and R 4 On the other hand, if the number of carbon atoms in the linking group is too large, R 1 and R 4 In the terminal group represented by formula (3-1), the total value of p and r is 5 or less, so that R 1 and R 4The alkylene chain in the main chain portion of the polymer is not too long. Therefore, the long rigid alkylene chain reduces the flexibility of the terminal portion, weakening the interaction with the protective layer and preventing the terminal portion from lifting up. p is preferably 0 or 1, and more preferably 0. r is preferably 1 or 2, and more preferably 1.

[0077] In formula (3-1), A represents a polar group. A is a hydroxyl group (-OH), an amino group (-NH), a carboxyl group (-COOH), a formyl group (-(C=O)H), a carbonyl group (-CO-), a sulfo group (-SOH), a cyano group (-CN), or a group having an amide bond (-NR 7 COR 8 or -CONR 9 R 10 ;R 7 , R 8 , R 9 and R 10 are each independently a hydrogen atom or an organic group.) As the group having an amide bond, R 1 and R 4 Examples of the polar group include groups having an amide bond as exemplified in the description of the polar group of (1), and an acetamide group (-NHC(=O)CH3) or a carboxamide group (-C(=O)NH2) is particularly preferred. This is because the resulting fluorine-containing ether compound can form a stronger lubricating layer through interaction with the protective layer.

[0078] Among these polar groups, A is more preferably a polar group selected from the group consisting of a hydroxyl group, a cyano group, and a group having an amide bond, and even more preferably a hydroxyl group, an acetamide group, or a carboxamide group. When A in formula (3-1) is a hydroxyl group, all of the polar groups in formula (3-1) are hydroxyl groups. 1 and R 4 When all of the polar groups of R are hydroxyl groups, the fluorine-containing ether compound is more uniformly coated on the protective layer, and a lubricating layer with better adhesion can be formed. 1 and R 4When one of the formulas is (3-1) and A is a hydroxyl group, R 1 and R 4 The other of the above is preferably any one of formula (3-1), formula (3-2) and formula (3-3) in which A is a hydroxyl group. When A in formula (3-1) is an acetamide group or a carboxamide group, the resulting fluorine-containing ether compound can form a lubricating layer that has stronger interaction with the protective layer.

[0079] In formula (3-1), q represents an integer of 0 to 2. The number of polar groups in formula (3-1) is q+2. 1 and R 4 The number of polar groups contained in each of the formulas is preferably 3 or less, and most preferably 2. Therefore, q in formula (3-1) is preferably 0 or 1, and more preferably 0.

[0080] In the terminal group represented by formula (3-2), the linking group between the carbon atom to which the terminal hydroxyl group is bonded and the carbon atom to which the hydroxyl group adjacent to the terminal hydroxyl group is bonded does not contain an oxygen atom. In formula (3-2), t represents an integer of 1 to 5. Therefore, the linking group has a linear structure consisting of 1 to 5 atoms, including a carbon atom to which no hydroxyl group is bonded. Because the linking group contained in formula (3-2) has a linear structure consisting of one or more atoms, including a carbon atom to which no hydroxyl group is bonded, the distance between the terminal hydroxyl group and the hydroxyl group adjacent to the terminal hydroxyl group is appropriate. Therefore, intramolecular interaction between the terminal hydroxyl group and the hydroxyl group adjacent to the terminal hydroxyl group can be suppressed, making intramolecular aggregation less likely to occur.

[0081] Also, as mentioned above, R 1 and R 4 In the above formula, if the number of carbon atoms contained in the linking group located between the carbon atoms bonded to the polar groups is too large, R 1 and R 4 In the case of the terminal group represented by formula (3-2), t is 5 or less, so that R 1and R 4 The alkylene chain in the main chain portion of the polymer is not too long. Therefore, the long rigid alkylene chain reduces the flexibility of the terminal portion, weakening the interaction with the protective layer and preventing the terminal portion from lifting up. t is preferably 4 or less, more preferably 1 or 2, and even more preferably 1.

[0082] Furthermore, since the linking group does not contain an oxygen atom forming an ether bond and has a linear structure consisting of five or less atoms including a carbon atom not bonded to a hydroxyl group, the linking group does not become too hydrophobic and does not impair adhesion to the protective layer. For these reasons, a lubricating layer containing a fluorine-containing ether compound in which the linking group does not contain an oxygen atom forming an ether bond and has a linear structure consisting of 1 to 5 atoms including a carbon atom not bonded to a hydroxyl group has excellent adhesion to the protective layer, provides excellent flying stability, and has a high pick-up suppression effect.

[0083] In formula (3-2), s represents an integer of 0 to 2. The number of polar groups in formula (3-2) is s+2. 1 and R 4 The number of polar groups contained in each of the formulas is preferably 3 or less, and most preferably 2. Therefore, s in formula (3-2) is preferably 0 or 1, and more preferably 0.

[0084] The terminal group represented by formula (3-3) has no secondary hydroxyl groups but two primary hydroxyl groups. 1 and / or R 4 When the hydroxyl group contained in R is a primary hydroxyl group, it is more likely to interact with the active site on the protective layer than when it is a secondary hydroxyl group. The terminal group represented by formula (3-3) does not have a secondary hydroxyl group, but has only two primary hydroxyl groups that are likely to interact with the active site on the protective layer. For this reason, R 1 and / or R 4When is a terminal group represented by formula (3-3), the resulting fluorine-containing ether compound is capable of forming a lubricating layer that has good adhesion to the protective layer.

[0085] Furthermore, in the terminal group represented by formula (3-3), the linking group between the carbon atoms to which two primary hydroxyl groups are bonded contains a carbon atom to which no hydroxyl group is bonded and an oxygen atom forming an ether bond. In formula (3-3), u represents an integer of 2 to 4. Y represents a linear alkylene group which may have ether oxygen, or a single bond. When Y is the alkylene group, the total number of carbon atoms and oxygen atoms contained in Y is 1 to 5. Therefore, the linking group has a structure consisting of 3 to 10 atoms, including a carbon atom to which no hydroxyl group is bonded and an oxygen atom forming an ether bond.

[0086] In the terminal group represented by formula (3-3), the linking group contains an oxygen atom forming an ether bond, and has a structure consisting of three or more atoms including a carbon atom not bonded to a hydroxyl group, so the distance between the two primary hydroxyl groups is appropriate. This ensures appropriate molecular mobility and reduces intramolecular aggregation. This results in a fluorine-containing ether compound that can form a lubricating layer with good adhesion to the protective layer.

[0087] Furthermore, in the terminal group represented by formula (3-3), the linking group contains an oxygen atom forming an ether bond and has a structure consisting of 10 or less atoms including a carbon atom not bonded to a hydroxyl group, so that the linking group does not have such high hydrophobicity that it interferes with adhesion to the protective layer. Therefore, a lubricating layer containing a fluorine-containing ether compound in which the linking group contains an oxygen atom forming an ether bond and has a structure consisting of 3 to 10 atoms including a carbon atom not bonded to a hydroxyl group has excellent adhesion to the protective layer, excellent flying stability, and a high pick-up suppression effect.

[0088] In addition, since u in formula (3-3) is 2 or more, -O-(CH2) u The primary hydroxyl group contained in —OH (hereinafter sometimes referred to as the “side chain portion”) and R1 and R 4 and R bonded via a methylene group 2 The distance between the PFPE chain represented by formula (3-3) and the bulky moiety, such as the tertiary carbon to which the side chain portion of formula (3-3) is bonded, is sufficiently large. Therefore, the primary hydroxyl group contained in the side chain portion of formula (3-3) can easily move freely. Furthermore, since u is 4 or less, the flexibility of the side chain portion of formula (3-3) is maintained. This results in a fluorine-containing ether compound that has excellent adhesion to the protective layer, exhibits high flying stability, and can form a lubricating layer with a high pickup suppression effect.

[0089] Also, as mentioned above, R 1 and R 4 In the above formula, if the number of carbon atoms contained in the linking group located between the carbon atoms bonded to the polar groups is too large, R 1 and R 4 The flexibility of the terminal group represented by the formula (I) may decrease, making it difficult to uniformly cover the entire surface of the protective layer. For this reason, u is preferably 2 or 3, and more preferably 2.

[0090] In addition, in formula (3-3), the primary hydroxyl group contained in -Y-CH2-OH is bonded via -Y-CH2- to the carbon atom to which the side chain portion of formula (3-3) is bonded. Therefore, the primary hydroxyl group contained in -Y-CH2-OH is more easily mobile than when the hydroxyl group is directly bonded to the carbon atom, and is more likely to interact with the active site on the protective layer.

[0091] Since the primary hydroxyl group contained in -Y-CH2-OH in formula (3-3) is more likely to be involved in the interaction with the active site on the protective layer, it is preferable that Y in formula (3-3) is not a single bond but a straight-chain alkylene group which may have an ether oxygen. In this case, the primary hydroxyl group contained in -Y-CH2-OH and R 1 and R 4 and R bonded via a methylene group 2This is because the distance between the PFPE chain represented by the formula (3-1) and the bulky moiety such as the tertiary carbon to which the side chain portion of formula (3-3) is bonded increases, allowing the primary hydroxyl group contained in -Y-CH2-OH to move more freely.

[0092] In formula (3-3), when Y is a linear alkylene group optionally containing ether oxygen, the total number of carbon atoms and oxygen atoms contained in Y is 1 to 5. In the terminal group represented by formula (3-3), the total number of carbon atoms and oxygen atoms contained in Y is 5 or less, so the alkylene chain in the main chain portion in formula (3-3) is not too long. Therefore, the long rigid alkylene chain reduces the flexibility of the terminal portion, weakening the interaction with the protective layer and preventing the terminal portion from lifting up. The total number of carbon atoms and oxygen atoms contained in Y is preferably 1 to 4, more preferably 1 to 3. The number of carbon atoms contained in Y is preferably 1 to 3, more preferably 1 to 2.

[0093] When Y in formula (3-3) is a linear alkylene group which may have an ether oxygen, specific examples of Y include -CH2-, -CH2CH2-, -CH2CH2CH2-, -CH2OCH2-, -CH2OCH2CH2-, -CH2OCH2CH2CH2-, -CH2CH2OCH2-, and the like.

[0094] In the terminal group represented by formula (3-4), the linking group between the carbon atom to which polar group B is bonded and the carbon atom to which a hydroxyl group adjacent to polar group B is bonded contains an oxygen atom forming an ether bond. The linking group has a structure consisting of 3 to 5 atoms, including a carbon atom to which polar group B and a hydroxyl group are not bonded. The number of atoms in the linking group refers to the number of atoms in the shortest distance between the carbon atom to which polar group B is bonded and the carbon atom to which a hydroxyl group adjacent to polar group B is bonded.

[0095] In the terminal group represented by formula (3-4), the linking group contains an oxygen atom forming an ether bond, and has a structure consisting of three or more atoms including a carbon atom not bonded to polar group B and a hydroxyl group. Therefore, the distance between polar group B and the hydroxyl group adjacent to polar group B is appropriate. In addition, the benzene ring is rigid, making free rotation difficult. Therefore, interaction between polar group B substituted on the benzene ring and the hydroxyl group adjacent to polar group B can be suppressed.

[0096] When v in formula (3-4) is 2 or more, -(CH2CH(OH)CHO) v The linking group between carbon atoms to which adjacent hydroxyl groups are bonded in - contains an oxygen atom forming an ether bond and has a linear structure consisting of three atoms including polar group B and a carbon atom to which no hydroxyl group is bonded. Because the linking group has a linear structure consisting of three atoms including polar group B and a carbon atom to which no hydroxyl group is bonded, the distance between adjacent hydroxyl groups is appropriate. This makes it possible to suppress interactions between hydroxyl groups within the molecule.

[0097] For these reasons, the fluorine-containing ether compound having the terminal group represented by formula (3-4) can suppress the interaction between polar groups in the molecule. Therefore, the lubricating layer containing the fluorine-containing ether compound having the terminal group represented by formula (3-4) has excellent adhesion to the protective layer, excellent flying stability, and a high pick-up suppression effect.

[0098] In formula (3-4), B represents a polar group substituted at any position on the benzene ring. B can be a hydroxyl group (-OH), an amino group (-NH), a carboxyl group (-COOH), a formyl group (-(C=O)H), a carbonyl group (-CO-), a sulfo group (-SOH), a cyano group (-CN), or a group having an amide bond (-NR 7 COR 8 or -CONR 9 R 10 ;R 7 , R 8 , R 9 and R 10are each independently a hydrogen atom or an organic group.) As the group having an amide bond, R 1 and R 4 Examples of the polar group include groups having an amide bond as exemplified in the description of the polar group of (1), and an acetamide group (-NHC(=O)CH3) or a carboxamide group (-C(=O)NH2) is particularly preferred. This is because the resulting fluorine-containing ether compound can form a stronger lubricating layer through interaction with the protective layer. Among these polar groups, B is more preferably a polar group selected from the group consisting of a cyano group and a group having an amide bond, and even more preferably a cyano group, an acetamide group or a carboxamide group.

[0099] In formula (3-4), v represents an integer of 1 to 3. The number of polar groups in formula (3-4) is v+1. 1 and R 4 The number of polar groups contained in each of the formulas is preferably 3 or less, and most preferably 2. Therefore, v in formula (3-4) is preferably 1 or 2, and more preferably 1.

[0100] R 1 and R 4 may be the same or different. 1 and R 4 When the ratio is the same, the fluorine-containing ether compound is more uniformly coated on the protective layer, and a lubricating layer having better adhesion can be formed.

[0101] (R 2 (PFPE chain shown as In the fluorine-containing ether compound represented by formula (1), R 2 is a perfluoropolyether chain. 2 When a lubricating layer is formed by applying a lubricant containing the fluorine-containing ether compound of this embodiment onto a protective layer, the PFPE chain represented by R not only covers the surface of the protective layer but also imparts lubricity to the lubricating layer, thereby reducing the frictional force between the magnetic head and the protective layer.2 The PFPE chain represented by the formula (I) is appropriately selected depending on the performance required of the lubricant containing the fluorine-containing ether compound.

[0102] (x+1) R 2 The (x+1) R may be the same in part or in whole, or may be different from each other. 2 It is preferable that all of the (x+1) R are the same. This is because the coating state of the fluorine-containing ether compound on the protective layer becomes more uniform, resulting in a lubricating layer with better adhesion. 2 Two or more of the R 2 are the same, (x+1) R 2 Among them, R 2 It means that two or more of the same R are included. 2 The term also includes those having the same repeating unit structure but different average degrees of polymerization.

[0103] 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.

[0104] (x+1) R in Equation (1) 2 are each preferably independently a PFPE chain represented by the following formula (4) derived from a polymer or copolymer of perfluoroalkylene oxide. -(CF2) w1 -O-(CF2O) w2 -(CF2CF2O) w3 -(CF2CF2CF2O) w4 -(CF2CF2CF2CF2O) w5 -(CF2) w6- (4) (In formula (4), w2, w3, w4, and w5 represent the average degree of polymerization and each independently represent 0 to 20; provided that w2, w3, w4, and w5 cannot all be 0 at the same time; w1 and w6 represent the average value representing the number of CF2 and each independently represent 1 to 3; there are no particular limitations on the arrangement order of the repeating units (CF2O), (CF2CF2O), (CF2CF2CF2O), and (CF2CF2CF2CF2O) in formula (4).)

[0105] In formula (4), w2, w3, w4, and w5 represent average degrees of polymerization, each independently representing 0 to 20, preferably 0 to 15, and more preferably 0 to 10. They may also be 1 to 8, 2 to 6, or 3 to 5. In formula (4), w1 and w6 are average values ​​indicating the number of CF2, and each independently represents 1 to 3. w1 and w6 are determined depending on the structure of the repeating unit arranged at the end of the chain structure in the PFPE chain represented by formula (4), etc. In formula (4), (CF2O), (CF2CF2O), (CF2CF2CF2O), and (CF2CF2CF2CF2O) are repeating units. There are no particular limitations on the arrangement order of the repeating units in formula (4). There are also no particular limitations on the number of types of repeating units in formula (4).

[0106] (x+1) R in Equation (1) 2 are preferably each independently any one selected from the PFPE chains represented by the following formulas (4-1) to (4-4). (x+1) R 2 are each one selected from the PFPE chains represented by formulas (4-1) to (4-4), a fluorine-containing ether compound can be obtained that provides a lubricating layer with good lubricity. 2are any one selected from the PFPE chains represented by formulas (4-1) to (4-4), the ratio of the number of oxygen atoms (the number of ether bonds (-O-)) to the number of carbon atoms in the PFPE chain is appropriate. This results in a fluorine-containing ether compound with appropriate hardness. Therefore, the fluorine-containing ether compound applied to the protective layer is less likely to aggregate on the protective layer, allowing for the formation of a thinner lubricating layer with sufficient coverage. Furthermore, the fluorine-containing ether compound has appropriate flexibility, allowing for the formation of a lubricating layer with better flying stability.

[0107] -CF2-(OCF2CF2) h -(OCF2) i -OCF2- (4-1) (In formula (4-1), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20.) -CF2CF2-(OCF2CF2CF2) j -OCF2CF2- (4-2) (In formula (4-2), j represents the average degree of polymerization and represents 1 to 15.) -CF2CF2CF2-(OCF2CF2CF2CF2) k -OCF2CF2CF2- (4-3) (In formula (4-3), k represents the average degree of polymerization and represents 1 to 10.) -(CF2) w7 -O-(CF2CF2CF2O) w8 -(CF2CF2O) w9 -(CF2) w10 - (4-4) (In formula (4-4), w8 and w9 represent the average degree of polymerization, each independently representing 1 to 20; w7 and w10 represent the average number of CF2, each independently representing 1 to 2.)

[0108] In formula (4-1), the arrangement order of the repeating units (OCF2CF2) and (OCF2) is not particularly limited. In formula (4-1), the number h of (OCF2CF2) and the number i of (OCF2) may be the same or different. The PFPE chain represented by formula (4-1) may be a polymer of (OCF2CF2). In addition, the PFPE chain represented by formula (4-1) may be any of a random copolymer, a block copolymer, and an alternating copolymer composed of (OCF2CF2) and (OCF2).

[0109] In formulas (4-1) to (4-3), h, which indicates the average degree of polymerization, is 1 to 20, i, which is 0 to 20, j, which is 1 to 15, and k, which is 1 to 10, and therefore the fluorine-containing ether compound provides a lubricating layer with good lubricity. Furthermore, in formulas (4-1) to (4-3), h and i, which indicate the average degree of polymerization, are 20 or less, j is 15 or less, and k is 10 or less, and therefore the viscosity of the fluorine-containing ether compound does not become too high, and lubricants containing the fluorine-containing ether compound are easily applied, which is preferable. h, i, j, and k, which indicate the average degree of polymerization, are preferably 1 to 10, more preferably 1.5 to 8, and even more preferably 2 to 7, and therefore the fluorine-containing ether compound easily wets and spreads on the protective layer, and a lubricating layer with a uniform thickness is easily obtained.

[0110] In formula (4-4), the arrangement order of the repeating units (CFCFCFO) and (CFCFO) is not particularly limited. In formula (4-4), the number w8 of (CFCFCFO) and the number w9 of (CFCFO), which indicate the average degree of polymerization, may be the same or different. Formula (4-4) may include any of a random copolymer, a block copolymer, and an alternating copolymer composed of the monomer units (CFCFCFO) and (CFCFO).

[0111] In formula (4-4), w8 and w9, which represent the average degree of polymerization, are each independently 1 to 20, preferably 1 to 15, and more preferably 1 to 10. In formula (4-4), w7 and w10 are average values ​​indicating the number of CF2, and each independently represents 1 to 2. w7 and w10 are determined depending on the structure of the repeating unit located at the end of the chain structure in the PFPE chain represented by formula (4-4), etc.

[0112] In the fluorine-containing ether compound represented by formula (1), (x+1) R 2 is the same as x and R 3 is the same, and R 1 and R 4 This is because the resulting fluorine-containing ether compound can be produced easily and efficiently.

[0113] Specifically, the fluorine-containing ether compound represented by formula (1) is preferably any one of the compounds represented by the following formulae (AA) to (AV) and (BA) to (BK). When the compound represented by formula (1) is any of the compounds represented by the following formulae (AA) to (AV) and (BA) to (BK), the raw materials are easily available, and even if the thickness is thin, it is possible to form a lubricating layer that has better floating stability and a high pick-up suppression effect for magnetic recording media.

[0114] In the compounds represented by the following formulae (AA) to (AV) and (BA) to (BK), Rf1, Rf2, and Rf3, which represent PFPE chains, each have the following structure. That is, in the compounds represented by the following formulae (AA) to (AP), (AS) to (AV), (BA) to (BI), and (BK), Rf1 is a PFPE chain represented by the above formula (4-1). In the compounds represented by the following formulae (AQ) and (BJ), Rf2 is a PFPE chain represented by the above formula (4-2). In the compound represented by the following formula (AR), Rf3 is a PFPE chain represented by the above formula (4-3). Note that h and i in Rf1, j in Rf2, and k in Rf3, which represent PFPE chains in the formulae (AA) to (AV), and (BA) to (BK), are values ​​that indicate the average degree of polymerization, and are not necessarily integers.

[0115] [ka]

[0116] In the compounds represented by the following formulae (AA) to (AV) and (BA) to (BK), at least one R 3 is a linking group represented by the above formula (2-1) or (2-2). In the compounds represented by the following formulae (AA) to (AV) and (BA) to (BK), R 1 and R 4 are terminal groups represented by any one of the above formulas (3-1) to (3-4). The compounds represented by the following formulas (AA) to (AV) and (BA) to (BK) are all compounds having (x+1) R 2 is the same.

[0117] In the compounds represented by the following formulas (AA) to (AM), x in formula (1) is 1. 1 and R 4 is the terminal group represented by the above formula (3-1) or (3-2). 3 is the linking group represented by the above formula (2-1). 2 is the PFPE chain represented by the above formula (4-1). In the compounds represented by the following formulas (AN) to (AP), x in formula (1) is 1. 1 and R 4 is the terminal group represented by the above formula (3-1). 3 is the linking group represented by the above formula (2-2). 2 is the PFPE chain represented by the above formula (4-1).

[0118] In the compounds represented by the following formulas (AQ) and (AR), x in formula (1) is 1. 1 and R 4 is the terminal group represented by the above formula (3-1). 3 is a linking group represented by the above formula (2-1). The compound represented by formula (AQ) is 2 is the PFPE chain represented by the above formula (4-2). The compound represented by formula (AR) is2 is the PFPE chain represented by the above formula (4-3).

[0119] In the compounds represented by the following formulas (AS) and (AT), x in formula (1) is 1. 1 and R 4 is the terminal group represented by the above formula (3-3). 3 is the linking group represented by the above formula (2-1). 2 is the PFPE chain represented by the above formula (4-1). In the compounds represented by the following formulas (AU) and (AV), x in formula (1) is 1. 1 and R 4 is the terminal group represented by the above formula (3-4). 3 is the linking group represented by the above formula (2-1). 2 is the PFPE chain represented by the above formula (4-1).

[0120] In the compounds represented by the following formulas (BA) to (BF), x in formula (1) is 2. 1 and R 4 is the terminal group represented by the above formula (3-1) or (3-2). 3 is the linking group represented by the above formula (2-1). 2 is the PFPE chain represented by the above formula (4-1). In the compounds represented by the following formulas (BG) and (BH), x in formula (1) is 2. 1 and R 4 is the terminal group represented by the above formula (3-1). 3 is the linking group represented by the above formula (2-2). 2 is the PFPE chain represented by the above formula (4-1).

[0121] In the compound represented by the following formula (BI), x in formula (1) is 2. 1 and R 4 is the terminal group represented by the above formula (3-1). 3 One of the R groups is a linking group represented by the above formula (2-1), and the other is a glycerin structure (-O-CH-CH(OH)-CH-O-).2 is the PFPE chain represented by the above formula (4-1). In the compound represented by the following formula (BJ), x in formula (1) is 2. 1 and R 4 is the terminal group represented by the above formula (3-1). 3 is the linking group represented by the above formula (2-1). 2 is the PFPE chain represented by the above formula (4-2). In the compound represented by the following formula (BK), x in formula (1) is 2. 1 and R 4 is the terminal group represented by the above formula (3-1). 3 is the linking group represented by the above formula (2-2). 2 is the PFPE chain represented by the above formula (4-1).

[0122] [ka] (In the two Rf1s in formula (AA), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20; the average degrees of polymerization in the two Rf1s may be the same or different.) (In the two Rf1s in formula (AB), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20; the average degrees of polymerization in the two Rf1s may be the same or different.) (In the two Rf1s in formula (AC), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20; the average degrees of polymerization in the two Rf1s may be the same or different.) (In the two Rf1s in formula (AD), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20; the average degrees of polymerization in the two Rf1s may be the same or different.)

[0123] [ka] (In the two Rf1s in formula (AE), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20; the average degrees of polymerization in the two Rf1s may be the same or different.) (In the two Rf1s in formula (AF), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20; the average degrees of polymerization in the two Rf1s may be the same or different.) (In the two Rf1s in formula (AG), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20; the average degrees of polymerization in the two Rf1s may be the same or different.)

[0124] [ka] (In the two Rf1s in formula (AH), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20; the average degrees of polymerization in the two Rf1s may be the same or different.) (In the two Rf1s in formula (AI), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20; the average degrees of polymerization in the two Rf1s may be the same or different.) (In the two Rf1s in formula (AJ), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20; the average degrees of polymerization in the two Rf1s may be the same or different.)

[0125] [ka] (In the two Rf1s in formula (AK), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20; the average degrees of polymerization in the two Rf1s may be the same or different.) (In the two Rf1s in formula (AL), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20; the average degrees of polymerization in the two Rf1s may be the same or different.) (In the two Rf1s in formula (AM), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20; the average degrees of polymerization in the two Rf1s may be the same or different.)

[0126] [ka] (In the two Rf1s in formula (AN), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20; the average degrees of polymerization in the two Rf1s may be the same or different.) (In the two Rf1s in formula (AO), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20; the average degrees of polymerization in the two Rf1s may be the same or different.) (In the two Rf1s in formula (AP), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20; the average degrees of polymerization in the two Rf1s may be the same or different.)

[0127] [ka] (In the two Rf2 in formula (AQ), j represents the average degree of polymerization and represents 1 to 15; the average degrees of polymerization in the two Rf2 may be the same or different.) (In the two Rf3s in formula (AR), k represents the average degree of polymerization and represents 1 to 10; the average degrees of polymerization in the two Rf3s may be the same or different.) (In the two Rf1s in formula (AS), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20; the average degrees of polymerization in the two Rf1s may be the same or different.) (In the two Rf1s in formula (AT), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20; the average degrees of polymerization in the two Rf1s may be the same or different.)

[0128] [ka] (In the two Rf1s in formula (AU), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20; the average degrees of polymerization in the two Rf1s may be the same or different.) (In the two Rf1s in formula (AV), h and i represent the average degree of polymerization, where h represents 1 to 20 and i represents 0 to 20; the average degrees of polymerization in the two Rf1s may be the same or different.)

[0129] [ka] (In the three Rf1s in formula (BA), h and i represent an average degree of polymerization, h represents 1 to 20, and i represents 0 to 20; h and i in the three Rf1s may be different from each other, or some or all of them may be the same.) (In the three Rf1s in formula (BB), h and i represent an average degree of polymerization, h represents 1 to 20, and i represents 0 to 20; h and i in the three Rf1s may be different from each other, or some or all of them may be the same.) (In the three Rf1s in formula (BC), h and i represent an average degree of polymerization, h represents 1 to 20, and i represents 0 to 20; h and i in the three Rf1s may be different from each other, or some or all of them may be the same.)

[0130] [ka] (In the three Rf1s in formula (BD), h and i represent an average degree of polymerization, h represents 1 to 20, and i represents 0 to 20; h and i in the three Rf1s may be different from each other, or some or all of them may be the same.) (In the three Rf1s in formula (BE), h and i represent an average degree of polymerization, h represents 1 to 20, and i represents 0 to 20; h and i in the three Rf1s may be different from each other, or some or all of them may be the same.) (In the three Rf1s in formula (BF), h and i represent an average degree of polymerization, h represents 1 to 20, and i represents 0 to 20; h and i in the three Rf1s may be different from each other, or some or all of them may be the same.)

[0131] [ka] (In the three Rf1s in formula (BG), h and i represent an average degree of polymerization, h represents 1 to 20, and i represents 0 to 20; h and i in the three Rf1s may be different from each other, or some or all of them may be the same.) (In the three Rf1s in formula (BH), h and i represent an average degree of polymerization, h represents 1 to 20, and i represents 0 to 20; h and i in the three Rf1s may be different from each other, or some or all of them may be the same.) (In the three Rf1s in formula (BI), h and i represent an average degree of polymerization, h represents 1 to 20, and i represents 0 to 20; h and i in the three Rf1s may be different from each other, or some or all of them may be the same.) (In the three Rf2 in formula (BJ), j represents the average degree of polymerization and represents 1 to 15; j in the three Rf2 may be different from each other, or some or all of them may be the same.) (In the three Rf1s in formula (BK), h and i represent an average degree of polymerization, h represents 1 to 20, and i represents 0 to 20; h and i in the three Rf1s may be different from each other, or some or all of them may be the same.)

[0132] The number average molecular weight (Mn) of the fluorinated ether compound of this embodiment is preferably in the range of 500 to 10,000, and particularly preferably in the range of 1,000 to 5,000. It may be 2,000 to 4,500, 2,500 to 4,000, or 3,000 to 3,500. When the number average molecular weight is 500 or more, a lubricating layer formed from a lubricant containing the fluorinated ether compound of this embodiment will have excellent heat resistance. The number average molecular weight of the fluorinated 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 fluorinated 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 fluorinated ether compound is preferably 5,000 or less, since this results in a manageable viscosity when applied to a lubricant.

[0133] The number average molecular weight (Mn) of fluorine-containing ether compounds was measured using AVANCEIII400 manufactured by Bruker Biospin. 1 H-NMR and 19 These are values ​​measured by F-NMR. Specifically, 19 The number of repeating units of the PFPE chain is calculated from the integrated value measured by F-NMR to determine the number average molecular weight. For NMR (nuclear magnetic resonance) measurements, the sample is diluted in a hexafluorobenzene / d-acetone (4 / 1 v / v) solvent and measured. 19 The reference for F-NMR chemical shifts is the hexafluorobenzene peak at -164.7 ppm. 1 The reference for H-NMR chemical shifts is the acetone peak at 2.2 ppm.

[0134] The fluorine-containing ether compound of this embodiment is preferably subjected to molecular weight fractionation by an appropriate method to make the molecular weight dispersity (ratio of weight average molecular weight (Mw) / number average molecular weight (Mn)) 1.3 or less. In this embodiment, the method for molecular weight fractionation is not particularly limited, but for example, molecular weight fractionation by silica gel column chromatography, gel permeation chromatography (GPC), or the like, molecular weight fractionation by supercritical extraction, or the like can be used.

[0135] [Manufacturing method] The method for producing the fluorinated ether compound of the present embodiment is not particularly limited, and the compound can be produced by a conventionally known production method. The fluorinated ether compound of the present embodiment can be produced, for example, by the production method shown below.

[0136] [First manufacturing method (x is 1)] (R 1 and R 4 is a terminal group represented by formula (3-1), (3-2) or (3-4), and R 1 and R 4 and are the same, and the two R 2 are the same) R in Equation (1) 2 A fluorine-based compound is prepared in which a hydroxymethyl group (-CH2OH) is placed at each end of the perfluoropolyether chain corresponding to the above.

[0137] Next, the hydroxyl group of the hydroxymethyl group located at one end of the fluorine-based compound and the R 1 The group corresponding to (=R 4 (first reaction) with an epoxy compound having a group corresponding to R 2 At one end of the perfluoropolyether chain corresponding to 1 The group corresponding to (=R 4 An intermediate compound 1-1 having a group corresponding to

[0138] R in Equation (1) 1 The group corresponding to (=R 4As the epoxy compound having a group corresponding to the following, for example, compounds represented by the following formulas (5-1) to (5-14) can be used: THP in the following formulas (5-1) to (5-14) represents a tetrahydropyranyl group.

[0139] [ka]

[0140] R in Equation (1) 1 The group corresponding to (=R 4 An epoxy compound having a group corresponding to R in formula (1) can be produced, for example, by the method shown below. 1 (or R 4 The compound can be produced by reacting an alcohol having a structure (R in formula (6-1)) corresponding to a portion of the terminal group represented by formula (6-1), with a halogen compound such as a bromine compound or a chlorine compound having an epoxy group (formula (6-1) is when the halogen compound is a bromine compound). The number of methylene groups (a1 in formula (6-1)) contained in the halogen compound having an epoxy group is 1 to 4 and can be determined appropriately depending on the structure of the terminal group of the compound to be synthesized.

[0141] [ka] (In formula (6-1), R is R in formula (1) 1 (or R 4 a1 represents an integer of 1 to 4.)

[0142] The epoxy compound may be produced by the following method: That is, as shown in the following formula (6-2), R 1 (or R 4The alcohol having a structure (R in formula (6-2)) corresponding to a portion of the terminal group represented by (6-2)) is reacted with a halogen compound such as a bromine compound or a chlorine compound having an alkenyl group (in formula (6-2) the halogen compound is a bromine compound). The resulting compound is then oxidized with m-chloroperbenzoic acid (mCPBA). The number of methylene groups contained in the halogen compound having an alkenyl group (a2 in formula (6-2)) is 1 to 4 and can be determined appropriately depending on the structure of the terminal group of the compound to be synthesized.

[0143] [ka] (In formula (6-2), R is R in formula (1) 1 (or R 4 a2 represents an integer of 1 to 4.

[0144] The epoxy compound may be produced by the following method: That is, as shown in the following formula (6-3), R 1 (or R 4 The compound having an alkenyl group and an epoxy group is subjected to an addition reaction of an alcohol having a structure (R in formula (6-3)) corresponding to a portion of the terminal group represented by formula (6-3) with a compound having an alkenyl group and an epoxy group. The compound obtained by the addition reaction is then oxidized by reacting with m-chloroperbenzoic acid (mCPBA). Before the compound obtained by the addition reaction is oxidized by reacting with m-chloroperbenzoic acid (mCPBA), the hydroxyl group generated by the addition reaction may be protected by a known method. The number of methylene groups (a3 in formula (6-3)) contained in the compound having an alkenyl group and an epoxy group is 1 to 4 and can be determined appropriately depending on the structure of the terminal group of the compound to be synthesized.

[0145] [ka] (In formula (6-3), R is R in formula (1) 1 (or R 4a3 represents an integer of 1 to 4.

[0146] Thereafter, the hydroxyl group at one end of the intermediate compound 1-1 produced in the first reaction described above is reacted with the R 3 is reacted with a compound having two corresponding epoxy groups (second reaction). R in Equation (1) 3 As a compound having two epoxy groups corresponding to the above, for example, compounds represented by the following formulas (7-1) to (7-3) can be used: THP in the following formula (7-3) represents a tetrahydropyranyl group.

[0147] [ka]

[0148] R in Equation (1) 3 When a compound represented by formula (7-2) is used as a compound having two epoxy groups corresponding to the above, it can be produced, for example, by the following method: That is, as shown in the following formula (8-1), it can be produced by a method in which the alkenyl group of a compound (allyl glycidyl ether) having an alkenyl group and an epoxy group is oxidized by the action of m-chloroperbenzoic acid (mCPBA).

[0149] [ka]

[0150] When a compound represented by formula (7-3) is used as the epoxy compound, it can be produced, for example, by the following method. That is, as shown in formula (8-2) below, a halogen compound such as a bromine compound or a chlorine compound having an epoxy group (formula (8-2) is when the halogen compound is a bromine compound) is reacted with an alcohol having an alkenyl group (allyl alcohol). The secondary hydroxyl group of the compound produced after the reaction is then protected with dihydropyran, and the alkenyl group is oxidized by the action of m-chloroperbenzoic acid (mCPBA). THP in formula (8-2) represents a tetrahydropyranyl group.

[0151] [ka]

[0152] The compound represented by formula (7-3) may be produced, for example, by the method shown below. That is, as shown in the following formula (8-3), it can be produced by a method of reacting a compound having two hydroxyl groups with a halogen compound such as a bromine compound or a chlorine compound having an epoxy group (in formula (8-3), the halogen compound is a bromine compound). THP in formula (8-3) represents a tetrahydropyranyl group.

[0153] [ka]

[0154] R in Equation (1) 3 As the compound having two epoxy groups corresponding to the above, a commercially available product may be used. After the above steps, a deprotection reaction is carried out using a known method to obtain a compound represented by the formula (1) where x is 1 and R 1 and R 4 is a terminal group represented by formula (3-1), (3-2) or (3-4), and R 1 and R 4 and are the same, and the two R 2 can be prepared.

[0155] [Second manufacturing method (when x is 1)] (R 1 and R 4 is a terminal group represented by formula (3-3), and R 1 and R 4 and are the same, and the two R 2 are the same) R in Equation (1) 2 A fluorine-based compound having a hydroxymethyl group at each end of a perfluoropolyether chain corresponding to formula (3-3) is prepared. Next, the hydroxyl group of the hydroxymethyl group at one end of the fluorine-based compound is reacted with an epoxy compound having a structure corresponding to the chain portion (main chain portion) containing the terminal group Y represented by formula (3-3) (first reaction). This results in R 2 An intermediate compound 1-2 is obtained, which has, at one end of the perfluoropolyether chain corresponding to the formula (3-3), a group corresponding to the chain portion (main chain portion) containing Y of the terminal group represented by formula (3-3) and a secondary hydroxyl group forming the side chain portion of the terminal group represented by formula (3-3).

[0156] The terminal group (=R 1 and R 4 As the epoxy compound having a structure corresponding to the chain portion (main chain portion) containing Y of the formula (a group corresponding to the formula (5-1)), for example, the compounds represented by the above formulas (5-1) to (5-4) and (5-9), and the compound represented by the formula (17) described below can be used.

[0157] Next, the hydroxyl group at one end of the intermediate compound 1-2 and the R 3 is reacted with a compound having a leaving group and a protected hydroxyl group corresponding to the above to obtain intermediate compound 1-3 (second reaction). R 3Examples of compounds having a leaving group and a protected hydroxyl group corresponding to the above include a compound represented by the formula (14) described below, a compound represented by the following formula (31), and a compound represented by the following formula (32). In formulas (31) and (32), THP represents a tetrahydropyranyl group, and Ts represents a tosyl group (p-toluenesulfonyl group).

[0158] [ka]

[0159] Next, the secondary hydroxyl group forming the side chain portion of the terminal group represented by formula (3-3) of intermediate compound 1-3 is reacted with -(CH2) u A halogen compound having a protected hydroxyl group corresponding to —OH is reacted (third reaction). -(CH2) in the side chain portion of the terminal group represented by formula (3-3) u Examples of halogen compounds having a protected hydroxyl group corresponding to —OH include a compound represented by the formula (16) described below, a compound represented by the following formula (33), and a compound represented by the following formula (34). THP in formulas (33) and (34) represents a tetrahydropyranyl group.

[0160] [ka]

[0161] After the above steps, a deprotection reaction is carried out using a known method to obtain a compound represented by the formula (1) where x is 1 and R 1 and R 4 is a terminal group represented by formula (3-3), and R 1 and R 4 and are the same, and the two R 2 can be prepared.

[0162] [Third manufacturing method (when x is 1)] (R 1 and R4 is a terminal group represented by formula (3-1), (3-2) or (3-4), and R 1 and R 4 and differ, and / or two R 2 are different) First, R 1 Side R 2 The hydroxyl group at one end of the perfluoropolyether chain of the fluorine-based compound, which has a hydroxymethyl group at each end, corresponds to R 1 An epoxy compound having a group corresponding to the formula (I) is reacted with the compound to obtain intermediate compound 1a (first reaction). Next, R 4 Side R 2 The hydroxyl group at one end of the perfluoropolyether chain of the fluorine-based compound, which has a hydroxymethyl group at each end, corresponds to R 4 An epoxy compound having a group corresponding to the formula (II) is reacted to obtain intermediate compound 1b (second reaction).

[0163] Next, the hydroxyl group at one end of the intermediate compound 1a is reacted with the R 3 After reacting with a compound having an epoxy group and an alkenyl group corresponding to the above, the double bond of the purified compound is oxidized to obtain intermediate compound 1-4 (third reaction). R in Equation (1) 3 As the compound having an epoxy group and an alkenyl group corresponding to the above, for example, compounds represented by formulas (9-1) to (9-3) described below can be used.

[0164] Next, the hydroxyl group at one end of the intermediate compound 1b is reacted with the epoxy group of the intermediate compound 1-4 obtained in the third reaction (fourth reaction). After the above steps, a deprotection reaction is carried out using a known method to obtain a compound represented by the formula (1) where x is 1 and R 1 and R 4 is a terminal group represented by formula (3-1), (3-2) or (3-4), and R 1 and R 4 and differ, and / or two R 2can be prepared.

[0165] [4th manufacturing method (when x is 1)] (R 1 and R 4 is a terminal group represented by formula (3-3), and R 1 and R 4 (if different from First, R 1 Side R 2 The hydroxyl group at one end of the perfluoropolyether chain of the fluorine-based compound, which has a hydroxymethyl group at each end, corresponds to R 1 The intermediate compound 1-2a is obtained by reacting the compound represented by formula (3-3) with an epoxy compound having a structure corresponding to the chain portion (main chain portion) containing the terminal group Y (first reaction).

[0166] Next, R 4 Side R 2 The hydroxyl group at one end of the perfluoropolyether chain of the fluorine-based compound, which has a hydroxymethyl group at each end, corresponds to R 4 The intermediate compound 1-2b is obtained by reacting the compound represented by formula (3-3) with an epoxy compound having a structure corresponding to the chain portion (main chain portion) containing the terminal group Y (second reaction).

[0167] Next, the hydroxyl group at one end of the intermediate compound 1-2a is reacted with the R 3 The intermediate compound 1-3a is obtained by reacting the compound having a leaving group and a protected hydroxyl group corresponding to the formula (III). Next, the hydroxyl group at one end of the intermediate compound 1-2b is reacted with the leaving group of the intermediate compound 1-3a obtained in the third reaction to obtain the intermediate compound 1-3b (fourth reaction).

[0168] Next, the secondary hydroxyl group forming the side chain portion of the terminal group represented by formula (3-3) of the intermediate compound 1-3b is reacted with R 1 -(CH2) in the side chain portion of the terminal group represented by formula (3-3) uA halogen compound having a protected hydroxyl group corresponding to —OH is reacted to obtain intermediate compound 1-5 (fifth reaction).

[0169] Next, the secondary hydroxyl group forming the side chain portion of the terminal group represented by formula (3-3) of the intermediate compound 1-5 is reacted with R 4 -(CH2) in the side chain portion of the terminal group represented by formula (3-3) u A halogen compound having a protected hydroxyl group corresponding to —OH is reacted (sixth reaction). After the above steps, a deprotection reaction is carried out using a known method to obtain a compound represented by the formula (1) where x is 1 and R 1 and R 4 is a terminal group represented by formula (3-3), and R 1 and R 4 It is possible to prepare compounds that are different from the above.

[0170] [5th ​​manufacturing method (when x is 1)] (R 1 is a terminal group represented by formula (3-3), and R 4 is a terminal group represented by formula (3-1), (3-2) or (3-4) First, the intermediate compound 1-3a is obtained in the same manner as in the fourth production method (first reaction). Next, the intermediate compound 1b is obtained in the same manner as in the third production method (second reaction). Next, the hydroxyl group at one end of intermediate compound 1b is reacted with the leaving group of intermediate compound 1-3a obtained in the first reaction to obtain intermediate compound 1-6 (third reaction).

[0171] Next, the secondary hydroxyl group forming the side chain portion of the terminal group represented by formula (3-3) of the intermediate compound 1-6 is reacted with R 1 -(CH2) in the side chain portion of the terminal group represented by formula (3-3) u A halogen compound having a protected hydroxyl group corresponding to —OH is reacted (fourth reaction).

[0172] After the above steps, a deprotection reaction is carried out using a known method to obtain a compound represented by the formula (1) where x is 1 and R 1 is a terminal group represented by formula (3-3), and R 4 is a terminal group represented by formula (3-1), (3-2) or (3-4).

[0173] [6th manufacturing method (when x is 2)] (R 1 and R 4 is a terminal group represented by formula (3-1), (3-2) or (3-4), and R 1 and R 4 are the same, and two R 3 is the same, and R 1 Side R 2 and R 4 Side R 2 are the same) First, in the same manner as in the first manufacturing method, R 1 Side and R 4 Side R 2 At one end of the perfluoropolyether chain corresponding to 1 The group corresponding to (=R 4 An intermediate compound 1-1 having a group corresponding to (a group corresponding to) is prepared (first reaction).

[0174] Next, R in the center of the molecule in formula (1) 2 A fluorine-based compound having a hydroxymethyl group (-CHOH) at each end of a perfluoropolyether chain corresponding to formula (1) is prepared. Then, the hydroxyl groups of the hydroxymethyl groups at both ends of the fluorine-based compound are reacted with the R 3 (second reaction) with a compound having an epoxy group and an alkenyl group corresponding to the formula:

[0175] R in Equation (1) 3 Examples of compounds having an epoxy group and an alkenyl group corresponding to the above formula (9-1) include compounds represented by the following formulas (9-1) to (9-3): THP in the following formula (9-3) represents a tetrahydropyranyl group.

[0176] [ka]

[0177] When a compound represented by formula (9-3) is used as the epoxy compound, it can be produced, for example, by the method shown below. That is, as shown in the following formula (10-1), a halogen compound such as a bromine compound or a chlorine compound having an epoxy group (formula (10-1) is when the halogen compound is a bromine compound) is reacted with an alcohol having an alkenyl group (allyl alcohol). Then, the secondary hydroxyl group of the compound produced after the reaction is protected with dihydropyran, and then only one of the alkenyl groups is oxidized by the action of m-chloroperbenzoic acid (mCPBA). In the following formula (10-1), THP represents a tetrahydropyranyl group.

[0178] [ka]

[0179] The compound represented by formula (9-3) may be produced, for example, by the following method. That is, as shown in the following formula (10-2), a compound having two hydroxyl groups is reacted with a halogen compound such as a bromine compound or a chlorine compound having an alkenyl group (in formula (10-2), the halogen compound is a bromine compound), to introduce a substituent having an alkenyl group into one of the hydroxyl groups, and then the compound is reacted with a halogen compound such as a bromine compound or a chlorine compound having an epoxy group (in formula (10-2), the halogen compound is a bromine compound). THP in the following formula (10-2) represents a tetrahydropyranyl group.

[0180] [ka]

[0181] Next, the compound produced after the second reaction is reacted with m-chloroperbenzoic acid (mCPBA) to oxidize the alkenyl group (third reaction). This oxidizes the R at the center of the molecule in formula (1). 2 At both ends of the perfluoropolyether chain corresponding to the two R 3 The third reaction may be carried out after the hydroxyl group of the compound produced after the second reaction is appropriately protected by a known method.

[0182] Thereafter, the hydroxyl group of the hydroxymethyl group located at one end of the intermediate compound 1-1 is reacted with the epoxy groups located at both ends of the intermediate compound 2-1 (fourth reaction). After the above steps, a deprotection reaction is carried out using a known method to obtain a compound represented by the formula (1) where x is 2 and R 1 and R 4 is a terminal group represented by formula (3-1), (3-2) or (3-4), and R 1 and R 4 are the same, and two R 3 is the same, and R 1 Side R 2 and R 4 Side R 2 can be prepared.

[0183] [7th manufacturing method (when x is 2)] (R 1 and R 4 is a terminal group represented by formula (3-3), and R 1 and R 4 and are the same, and the two R 3 is the same, and R 1 Side R 2 and R 4 Side R 2 are the same) First, in the same manner as in the second manufacturing method, R 1 Side and R 4 Side R 2An intermediate compound 1-2 is produced (first reaction), which has, at one end of the perfluoropolyether chain corresponding to the formula (3-3), a group corresponding to the chain portion (main chain portion) containing Y of the terminal group represented by formula (3-3) and a secondary hydroxyl group forming a side chain portion of the terminal group represented by formula (3-3).

[0184] Next, R in the center of the molecule in formula (1) 2 A fluorine-based compound having a hydroxymethyl group (-CHOH) at each end of a perfluoropolyether chain corresponding to formula (1) is prepared. Then, the hydroxyl groups of the hydroxymethyl groups at both ends of the fluorine-based compound are reacted with the R 3 (second reaction) with a compound having a leaving group and a protected hydroxyl group corresponding to the formula (1). 2 At both ends of the perfluoropolyether chain corresponding to the two R 3 The intermediate compound 2-2 having a structure and leaving group corresponding to the formula:

[0185] Thereafter, the hydroxyl group of the hydroxymethyl group located at one end of the intermediate compound 1-2 is reacted with the intermediate compound 2-2 to obtain the intermediate compound 2-3 (third reaction). Next, the secondary hydroxyl group forming the side chain portion of the terminal group represented by formula (3-3) of intermediate compound 2-3 is reacted with -(CH2) u A halogen compound having a protected hydroxyl group corresponding to —OH is reacted (fourth reaction).

[0186] After the above steps, a deprotection reaction is carried out using a known method to obtain a compound represented by the formula (1) where x is 2 and R 1 and R 4 is a terminal group represented by formula (3-3), and R 1 and R 4 and are the same, and the two R 3 is the same, and R 1 Side R 2 and R 4 Side R 2 can be prepared.

[0187] [8th manufacturing method (when x is 2)] (Two R 3 is the same, and R 1 and R 4 is a terminal group represented by formula (3-1), (3-2) or (3-4), and R 1 and R 4 and / or R 1 Side R 2 and R 4 Side R 2 are different) First, in the same manner as in the third manufacturing method, R 1 Side R 2 At one end of the perfluoropolyether chain corresponding to 1 In addition, in the same manner as in the third production method, an intermediate compound 1a having a group corresponding to R 4 Side R 2 At one end of the perfluoropolyether chain corresponding to 4 An intermediate compound 1b having a group corresponding to the following is prepared (second reaction).

[0188] Next, in the same manner as in the sixth production method, R at the center of the molecule in formula (1) 2 At both ends of the perfluoropolyether chain corresponding to the two R 3 An intermediate compound 2-1 having an epoxy group corresponding to the formula (third reaction) is prepared.

[0189] Then, the hydroxyl group of the hydroxymethyl group located at one end of the intermediate compound 1a is reacted with the epoxy group located at one end of the intermediate compound 2-1 to obtain the intermediate compound 2-4 (fourth reaction). Next, the hydroxyl group of the hydroxymethyl group located at one end of the intermediate compound 1b is reacted with the epoxy group of the intermediate compound 2-4 obtained in the fourth reaction (fifth reaction).

[0190] After the above steps, a deprotection reaction is carried out using a known method to obtain a compound represented by the formula (1) where x is 2 and two R3 is the same, and R 1 and R 4 is a terminal group represented by formula (3-1), (3-2) or (3-4), and R 1 and R 4 and / or R 1 Side R 2 and R 4 Side R 2 can be prepared.

[0191] [9th manufacturing method (when x is 2)] (R 1 and R 4 is a terminal group represented by formula (3-3), and R 1 and R 4 (if different from First, in the same manner as in the fourth manufacturing method, R 1 Side R 2 At one end of the perfluoropolyether chain corresponding to 1 An intermediate compound 1-2a having a structure corresponding to a chain portion (main chain portion) containing a terminal group Y represented by formula (3-3) is produced (first reaction). In addition, in the same manner as in the fourth manufacturing method, R 4 Side R 2 At one end of the perfluoropolyether chain corresponding to 4 An intermediate compound 1-2b having a structure corresponding to the chain portion (main chain portion) containing the terminal group Y, represented by formula (3-3), is produced (second reaction).

[0192] Next, in the same manner as in the seventh production method, R at the center of the molecule in formula (1) 2 At both ends of the perfluoropolyether chain corresponding to the two R 3 An intermediate compound 2-2 having a structure and a leaving group corresponding to the above is obtained (third reaction).

[0193] Then, the hydroxyl group of the hydroxymethyl group located at one end of intermediate compound 1-2a is reacted with the leaving group located at one end of intermediate compound 2-2 to obtain intermediate compound 2-5 (fourth reaction). Next, the hydroxyl group of the hydroxymethyl group located at one end of intermediate compound 1-2b is reacted with the leaving group of intermediate compound 2-5 obtained in the fourth reaction to obtain intermediate compound 2-6 (fifth reaction).

[0194] Next, the secondary hydroxyl group forming the side chain portion of the terminal group represented by formula (3-3) of the intermediate compound 2-6 is reacted with R 1 -(CH2) in the side chain portion of the terminal group represented by formula (3-3) u A halogen compound having a protected hydroxyl group corresponding to —OH is reacted to give intermediate compound 2-7 (sixth reaction). Next, the secondary hydroxyl group forming the side chain portion of the terminal group represented by formula (3-3) of the intermediate compound 2-7 is reacted with R 4 -(CH2) in the side chain portion of the terminal group represented by formula (3-3) u A halogen compound having a protected hydroxyl group corresponding to —OH is reacted (seventh reaction).

[0195] After the above steps, a deprotection reaction is carried out using a known method to obtain a compound represented by the formula (1) where x is 2 and R 1 and R 4 is a terminal group represented by formula (3-3), and R 1 and R 4 It is possible to prepare compounds that are different from the above.

[0196] [10th manufacturing method (when x is 2)] (R 1 is a terminal group represented by formula (3-3), and R 4 is a terminal group represented by formula (3-1), (3-2) or (3-4) First, the intermediate compound 2-5 is obtained in the same manner as in the ninth production method (first reaction).

[0197] In addition, in the same manner as in the third manufacturing method, R 4 Side R 2 At one end of the perfluoropolyether chain corresponding to 4 An intermediate compound 1b having a group corresponding to the following is prepared (second reaction). Thereafter, the hydroxyl group of the hydroxymethyl group located at one end of the intermediate compound 1b is reacted with the leaving group of the intermediate compound 2-5 to obtain the intermediate compound 2-8 (third reaction).

[0198] Next, the secondary hydroxyl group forming the side chain portion of the terminal group represented by formula (3-3) of the intermediate compound 2-8 is reacted with R 1 -(CH2) in the side chain portion of the terminal group represented by formula (3-3) u A halogen compound having a protected hydroxyl group corresponding to —OH is reacted (fourth reaction).

[0199] After the above steps, a deprotection reaction is carried out using a known method to obtain a compound represented by the formula (1) where x is 2 and R 1 is a terminal group represented by formula (3-3), and R 4 is a terminal group represented by formula (3-1), (3-2) or (3-4).

[0200] [11th manufacturing method (when x is 2)] (Two R 3 are different, at least one of which is a divalent linking group represented by formula (2-1) or (2-2), and R 1 and R 4 is a terminal group represented by formula (3-1), (3-2) or (3-4) Intermediate compound 2-9 can be produced by the method shown below, and the compound can be produced by the sixth production method using intermediate compound 2-9 instead of intermediate compound 2-1.

[0201] That is, R at the center of the molecule in formula (1) 2 A fluorine-based compound having a hydroxymethyl group (-CHOH) at each end of a perfluoropolyether chain corresponding to the formula (1) is prepared. Next, the hydroxyl group of the hydroxymethyl group at one end of the fluorine-based compound is reacted with one of the R 3 Then, the resulting compound is reacted with a compound having an epoxy group and an alkenyl group corresponding to the other R in formula (1). 3The compound having an epoxy group and an alkenyl group is reacted with the corresponding compound.

[0202] The resulting compound is then treated with m-chloroperbenzoic acid (mCPBA) to oxidize the alkenyl group. This oxidizes the R at the center of the molecule in formula (1). 2 At one end of the perfluoropolyether chain corresponding to one of the R 3 and at the other end thereof, an epoxy group corresponding to the other R in formula (1) 3 The intermediate compound 2-9 having an epoxy group corresponding to the formula:

[0203] (Two R 3 are different, at least one of which is a divalent linking group represented by formula (2-1) or (2-2), and R 1 and R 4 is a terminal group represented by formula (3-3) Intermediate compound 2-10 can be produced by the method shown below, and the compound can be produced by the seventh production method using intermediate compound 2-10 instead of intermediate compound 2-2.

[0204] That is, R at the center of the molecule in formula (1) 2 A fluorine-based compound having a hydroxymethyl group (-CHOH) at each end of a perfluoropolyether chain corresponding to the formula (1) is prepared. Next, the hydroxyl group of the hydroxymethyl group at one end of the fluorine-based compound is reacted with one of the R 3 Then, the resulting compound is reacted with the other R in formula (1) 3 The compound is reacted with a compound having a leaving group and a protected hydroxyl group, which corresponds to the following formula:

[0205] This results in the R in the center of the molecule in formula (1). 2 At one end of the perfluoropolyether chain corresponding to one of the R 3 and a leaving group corresponding to the other R in formula (1) at the other end.3 The intermediate compound 2-10 is obtained, which has a structure and leaving group corresponding to:

[0206] [Lubricants for magnetic recording media] The lubricant for a magnetic recording medium of this embodiment contains a fluorine-containing ether compound represented by the above formula (1). The lubricant of the present embodiment can be used by mixing, as needed, known materials used as lubricant materials, as long as the properties resulting from the inclusion of the fluorinated ether compound represented by the above formula (1) are not impaired.

[0207] 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), and the like. 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.

[0208] 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 50 mass% or more, more preferably 70 mass% or more, and even more preferably 90 mass% or more.

[0209] 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 flying stability and a high pick-up suppressing effect.

[0210] [Magnetic recording media] The magnetic recording medium of this embodiment has at least a magnetic layer, a protective layer, and a lubricating layer provided in this order on a substrate. In the magnetic recording medium of this embodiment, one or more underlayers may be provided between the substrate and the magnetic layer, as needed, and at least one of an adhesive layer and a soft magnetic layer may also be provided between the underlayer and the substrate.

[0211] FIG. 1 is a schematic cross-sectional view showing one embodiment of the magnetic recording medium of the present invention. The magnetic recording medium 10 of this embodiment has a structure in which an adhesive layer 12, a soft magnetic layer 13, a first underlayer 14, a second underlayer 15, a magnetic layer 16, a protective layer 17, and a lubricating layer 18 are sequentially provided on a substrate 11.

[0212] "substrate" The substrate 11 may be, for example, a non-magnetic substrate in which a film made of NiP or a NiP alloy is formed on a base made of a metal or alloy material such as Al or an Al alloy. The substrate 11 may be a non-magnetic substrate made of a non-metallic material such as glass, ceramics, silicon, silicon carbide, carbon, or resin, or may be a non-magnetic substrate having a NiP or NiP alloy film formed on a base made of any of these non-metallic materials.

[0213] "Adhesion layer" The adhesive layer 12 prevents the progress of corrosion of the substrate 11, which occurs when the substrate 11 and the soft magnetic layer 13 provided on the adhesive layer 12 are disposed in contact with each other. The material of the adhesive layer 12 can be appropriately selected from, for example, Cr, a Cr alloy, Ti, a Ti alloy, CrTi, NiAl, an AlRu alloy, etc. The adhesive layer 12 can be formed by, for example, a sputtering method.

[0214] "Soft magnetic layer" The soft magnetic layer 13 preferably has a structure in which a first soft magnetic film, an intermediate layer made of a Ru film, and a second soft magnetic film are laminated in this order. That is, the soft magnetic layer 13 preferably has a structure in which the intermediate layer made of a Ru film is sandwiched between two soft magnetic films, and the soft magnetic films above and below the intermediate layer are antiferro-coupling (AFC).

[0215] The first and second soft magnetic films may be made of a material such as a CoZrTa alloy or a CoFe alloy. It is preferable to add Zr, Ta, or Nb to the CoFe alloy used in the first and second soft magnetic films. This promotes the amorphization of the first and second soft magnetic films. As a result, it is possible to improve the orientation of the first underlayer (seed layer) and reduce the flying height of the magnetic head. The soft magnetic layer 13 can be formed by, for example, a sputtering method.

[0216] "First base layer" The first underlayer 14 is a layer that controls the orientation and crystal size of the second underlayer 15 and magnetic layer 16 that are provided thereon. The first underlayer 14 may be, for example, a Cr layer, a Ta layer, a Ru layer, or a CrMo alloy layer, a CoW alloy layer, a CrW alloy layer, a CrV alloy layer, or a CrTi alloy layer. The first underlayer 14 can be formed by, for example, a sputtering method.

[0217] "Second base layer" The second underlayer 15 is a layer that controls the orientation of the magnetic layer 16. The second underlayer 15 is preferably a layer made of Ru or a Ru alloy. The second underlayer 15 may be a single layer or may be composed of multiple layers. When the second underlayer 15 is composed of multiple layers, all of the layers may be composed of the same material, or at least one layer may be composed of a different material. The second underlayer 15 can be formed by, for example, a sputtering method.

[0218] "Magnetic layer" The magnetic layer 16 is a magnetic film whose easy axis of magnetization is oriented perpendicular or parallel to the substrate surface. The magnetic layer 16 contains Co and Pt. To improve the SNR characteristics, the magnetic layer 16 may contain oxides, Cr, B, Cu, Ta, Zr, or the like. The oxides contained in the magnetic layer 16 include SiO2, SiO, Cr2O3, CoO, Ta2O3, and TiO2.

[0219] The magnetic layer 16 may be composed of a single layer, or may be composed of multiple magnetic layers made of materials with different compositions. For example, when the magnetic layer 16 is composed of three layers, namely, a first magnetic layer, a second magnetic layer, and a third magnetic layer stacked in this order from 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. The oxide contained in the first magnetic layer is preferably an oxide of Cr, Si, Ta, Al, Ti, Mg, Co, or the like. Among these, TiO2, Cr2O3, SiO2, and the like are particularly suitable. Furthermore, the first magnetic layer is preferably made of a composite oxide containing two or more types of oxides. Among these, Cr2O3-SiO2, Cr2O3-TiO2, SiO2-TiO2, and the like are particularly suitable.

[0220] The first magnetic layer may contain one or more elements selected from B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb, Ru, and Re in addition to Co, Cr, Pt, and oxides. The second magnetic layer can be made of the same material as the first magnetic layer, and preferably has a granular structure.

[0221] The third magnetic layer preferably has a non-granular structure made of a material containing Co, Cr, and Pt and not containing oxides, and may contain one or more elements selected from B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb, Ru, Re, and Mn in addition to Co, Cr, and Pt.

[0222] When magnetic layer 16 is formed of multiple magnetic layers, it is preferable to provide a non-magnetic layer between adjacent magnetic layers. When magnetic layer 16 is formed of three layers, namely, a first magnetic layer, a second magnetic layer, and a third magnetic layer, it is preferable to provide a non-magnetic layer between the first magnetic layer and the second magnetic layer and between the second magnetic layer and the third magnetic layer.

[0223] The non-magnetic layer provided between adjacent magnetic layers of the magnetic layer 16 can suitably be made of, for example, Ru, a Ru alloy, a CoCr alloy, or a CoCrX1 alloy (X1 represents one or more elements selected from Pt, Ta, Zr, Re, Ru, Cu, Nb, Ni, Mn, Ge, Si, O, N, W, Mo, Ti, V, and B).

[0224] The non-magnetic layer provided between adjacent magnetic layers of the magnetic layer 16 preferably uses an alloy material containing an oxide, metal nitride, or metal carbide. Specifically, oxides that can be used include, for example, SiO2, Al2O3, Ta2O5, Cr2O3, MgO, Y2O3, and TiO2. Metal nitrides that can be used include, for example, AlN, Si3N4, TaN, and CrN. Metal carbides that can be used include, for example, TaC, BC, and SiC. The non-magnetic layer can be formed by, for example, a sputtering method.

[0225] To achieve higher recording density, the magnetic layer 16 is preferably a magnetic layer for perpendicular magnetic recording, in which the axis of easy magnetization is oriented perpendicular to the substrate surface, but may also be a magnetic layer for longitudinal magnetic recording. The magnetic layer 16 may be formed by any conventionally known method such as vapor deposition, ion beam sputtering, magnetron sputtering, etc. The magnetic layer 16 is usually formed by sputtering.

[0226] "Protective layer" The protective layer 17 protects the magnetic layer 16. The protective layer 17 may be composed of one layer or multiple layers. A carbon-based protective layer is preferably used as the protective layer 17, and an amorphous carbon protective layer is particularly preferred. If the protective layer 17 is a carbon-based protective layer, the interaction with the polar groups (particularly hydroxyl groups) contained in the fluorine-containing ether compound in the lubricating layer 18 is further enhanced, which is preferable.

[0227] The adhesion between the carbon-based protective layer and the lubricating layer 18 can be controlled by using hydrogenated carbon and / or nitrogenated carbon for the carbon-based protective layer and adjusting the hydrogen and / or nitrogen content in the carbon-based protective layer. The hydrogen content in the carbon-based protective layer is preferably 3 atomic % to 20 atomic % when measured by hydrogen forward scattering (HFS). The nitrogen content in the carbon-based protective layer is preferably 4 atomic % to 15 atomic % when measured by X-ray photoelectron spectroscopy (XPS).

[0228] The hydrogen and / or nitrogen contained in the carbon-based protective layer does not need to be uniformly contained throughout the carbon-based protective layer. The carbon-based protective layer is preferably a compositionally graded layer, for example, in which nitrogen is contained on the lubricating layer 18 side of protective layer 17 and hydrogen is contained on the magnetic layer 16 side of protective layer 17. In this case, the adhesion between the magnetic layer 16 and lubricating layer 18 and the carbon-based protective layer is further improved.

[0229] 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.

[0230] The protective layer 17 can be formed by sputtering using a target material containing carbon, chemical vapor deposition (CVD) using a hydrocarbon raw material such as ethylene or toluene, or ion beam deposition (IBD). When a carbon-based protective layer is formed as protective layer 17, it can be deposited by, for example, DC magnetron sputtering. In particular, when a carbon-based protective layer is formed as protective layer 17, it is preferable to deposit an amorphous carbon protective layer by plasma CVD. The amorphous carbon protective layer deposited by plasma CVD has a uniform surface with little roughness.

[0231] "Lubricant layer" The lubricating layer 18 prevents contamination of the magnetic recording medium 10. The lubricating layer 18 also reduces the frictional force of the magnetic head of the magnetic recording / reproducing device that slides on the magnetic recording medium 10, thereby improving the durability of the magnetic recording medium 10. 1, the lubricating layer 18 is formed on and in contact with the protective layer 17. The lubricating layer 18 is formed by applying the magnetic recording medium lubricant of the above-described embodiment onto the protective layer 17. Therefore, the lubricating layer 18 contains the above-described fluorine-containing ether compound.

[0232] 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.

[0233] The average thickness of the lubricating layer 18 is preferably 0.5 nm (5 Å) to 2.0 nm (20 Å), and more preferably 0.5 nm (5 Å) to 1.2 nm (12 Å). When the average thickness of the lubricating layer 18 is 0.5 nm or more, the lubricating layer 18 is formed with a uniform thickness without forming an island or mesh-like structure. Therefore, the surface of the protective layer 17 can be covered with the lubricating layer 18 at a high coverage rate. Furthermore, by setting the average thickness of the lubricating layer 18 to 2.0 nm or less, the lubricating layer 18 can be made sufficiently thin, and the flying height of the magnetic head can be made sufficiently small.

[0234] "Method for forming lubricating layer" A method for forming the lubricating layer 18 includes, for example, preparing a magnetic recording medium in the middle of manufacturing in which the layers up to the protective layer 17 are formed on the substrate 11, applying a solution for forming the lubricating layer onto the protective layer 17, and drying the solution.

[0235] The lubricant layer forming solution can be obtained by dispersing and dissolving the lubricant for a magnetic recording medium according to the above embodiment in a solvent as needed, and adjusting the viscosity and concentration to suit the coating method. Examples of the solvent used in the lubricating layer-forming solution include fluorine-based solvents such as Vertrel (registered trademark) XF (trade name, manufactured by Mitsui DuPont Fluorochemicals Co., Ltd.).

[0236] The method for applying the lubricating layer-forming solution is not particularly limited, but examples thereof include spin coating, spraying, paper coating, and dipping. When using the dipping method, for example, the following method can be used. First, the substrate 11 on which each layer up to the protective layer 17 has been formed is immersed in a lubricant layer-forming solution placed in an immersion tank of a dip coating device. Next, the substrate 11 is lifted from the immersion tank at a predetermined speed. In this way, the lubricant layer-forming solution is applied to the surface of the substrate 11 above the protective layer 17. By using the dipping method, the lubricating layer forming solution can be applied uniformly to the surface of the protective layer 17, and the lubricating layer 18 can be formed on the protective layer 17 with a uniform thickness.

[0237] In this embodiment, it is preferable to perform a heat treatment on the substrate 11 on which the lubricating layer 18 is formed. By performing the heat treatment, the adhesion between the lubricating layer 18 and the protective layer 17 is improved, and the adhesive force between the lubricating layer 18 and the protective layer 17 is also improved. The heat treatment temperature is preferably 100°C to 180°C, and more preferably 100°C to 160°C. When the heat treatment temperature is 100°C or higher, the effect of improving the adhesion between the lubricating layer 18 and the protective layer 17 can be sufficiently obtained. Furthermore, by setting the heat treatment temperature to 180°C or lower, thermal decomposition of the lubricating layer 18 due to the heat treatment can be prevented. The heat treatment time can be adjusted appropriately depending on the heat treatment temperature, and is preferably 10 minutes to 120 minutes.

[0238] In this embodiment, in order to further improve the adhesive strength of the lubricating layer 18 to the protective layer 17, the lubricating layer 18 may be irradiated with ultraviolet (UV) rays before or after the heat treatment.

[0239] 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 floating stability and a high pickup suppression effect. 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 achieve a low magnetic head floating height (e.g., 10 nm or less) and operates stably for a long period of time, even in harsh environments associated with diverse applications. Therefore, the magnetic recording medium 10 of this embodiment is particularly suitable as a magnetic disk to be installed in a magnetic disk device using the LUL (Load Unload) method. [Example]

[0240] 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. [Example 1] The compound represented by the above formula (AA) was obtained by the method shown below. (First reaction) Place HOCH2CF2O (CF2CF2O) in a 100 mL recovery flask under a nitrogen gas atmosphere. h (CF2O) i 20 g of a compound (number average molecular weight 1000, molecular weight distribution 1.1) represented by CF2CH2OH (where h, representing the average degree of polymerization, is 4.5, and i, representing the average degree of polymerization, is 4.5), 4.12 g of a compound represented by the above formula (5-1), and 20 mL of t-butanol were charged and stirred at room temperature until homogeneous to form a mixture. 1.12 g of potassium tert-butoxide was added to this mixture, and the mixture was reacted by stirring at 70°C for 16 hours.

[0241] The compound represented by formula (5-1) was synthesized by protecting the hydroxyl group of ethylene glycol monoallyl ether with dihydropyran, followed by oxidation with m-chloroperbenzoic acid.

[0242] The reaction product obtained after the reaction was cooled to 25°C, transferred to a separatory funnel containing 100 mL of water, and extracted three times with 100 mL of ethyl acetate. The organic layer was washed with water and dehydrated over anhydrous sodium sulfate. After filtering off the desiccant, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 9.61 g of the compound represented by the following formula (11) as intermediate compound 1-1.

[0243] [ka] (Rf1 in formula (11) is a PFPE chain represented by the above formula (4-1); in Rf1, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5; THP represents a tetrahydropyranyl group.)

[0244] (Second reaction) Next, 9.61 g of the compound represented by formula (11), which is intermediate compound 1-1 obtained above, 0.34 g of the compound represented by formula (7-1), and 20 mL of t-butanol were charged into a 100 mL recovery flask under a nitrogen gas atmosphere, and the mixture was stirred at room temperature until it became homogeneous. 0.45 g of potassium tert-butoxide was added to the mixture, and the mixture was reacted by stirring at 70°C for 16 hours.

[0245] After the reaction, the resulting reaction mixture was cooled to room temperature, and 50 g of a 10% hydrogen chloride-methanol solution (hydrogen chloride-methanol reagent (5-10%), manufactured by Tokyo Chemical Industry Co., Ltd.) was added and stirred at room temperature for 4 hours. The reaction mixture was then transferred in small portions to a separatory funnel containing 100 mL of saturated aqueous sodium bicarbonate and extracted twice with 200 mL of ethyl acetate. The organic layer was washed sequentially with 100 mL of brine, 100 mL of saturated aqueous sodium bicarbonate, and 100 mL of brine, and then dehydrated 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 2.81 g of compound (AA). (Rf1 in formula (AA) represents the PFPE chain represented by formula (4-1) above. In the two Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5.)

[0246] The obtained compound (AA) 1 H-NMR measurement and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=3.40-3.85(30H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0247] [Example 2] The compound represented by the above formula (AB) was obtained by the method shown below. The same operation as in Example 1 was performed, except that the compound represented by formula (5-2) was used instead of the compound represented by formula (5-1), to obtain 2.92 g of compound (AB) (Rf1 in formula (AB) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which represents the average degree of polymerization, is 4.5, and i, which represents the average degree of polymerization, is 4.5).

[0248] The compound represented by formula (5-2) was synthesized by protecting one hydroxyl group of 1,3-propanediol with dihydropyran, followed by reaction with epibromohydrin.

[0249] The obtained compound (AB) 1 H-NMR measurement and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.65-1.85(4H), 3.40-3.85(30H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0250] [Example 3] The compound represented by the above formula (AC) was obtained by the method shown below. The same operation as in Example 1 was performed, except that the compound represented by formula (5-3) was used instead of the compound represented by formula (5-1), to obtain 2.54 g of compound (AC) (Rf1 in formula (AC) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which represents the average degree of polymerization, is 4.5, and i, which represents the average degree of polymerization, is 4.5).

[0251] The compound represented by formula (5-3) was synthesized by protecting the hydroxyl group of 3-buten-1-ol with dihydropyran, followed by oxidation with m-chloroperbenzoic acid.

[0252] The obtained compound (AC) 1 H-NMR measurement and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.65-1.85(4H), 3.40-3.85(22H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0253] [Example 4] The compound represented by the above formula (AD) was obtained by the method shown below. The same operations as in Example 1 were performed, except that the compound represented by formula (5-4) was used instead of the compound represented by formula (5-1), to obtain 2.54 g of compound (AD) (Rf1 in formula (AD) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0254] The compound represented by formula (5-4) was synthesized by reacting the hydroxyl group of 3-buten-1-ol with 2-(2-bromoethoxy)tetrahydro-2H-pyran, followed by oxidation with m-chloroperbenzoic acid.

[0255] The obtained compound (AD) 1 H-NMR measurement and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.65-1.85(4H), 3.40-3.85(30H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0256] [Example 5] The compound represented by the above formula (AE) was obtained by the method shown below. The same operation as in Example 1 was performed, except that the compound represented by formula (5-5) was used instead of the compound represented by formula (5-1), to obtain 2.84 g of compound (AE) (Rf1 in formula (AE) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which represents the average degree of polymerization, is 4.5, and i, which represents the average degree of polymerization, is 4.5).

[0257] The compound represented by formula (5-5) was synthesized by subjecting the compound represented by formula (5-1) to an addition reaction with allyl alcohol, protecting the hydroxyl group of the resulting compound with dihydropyran, and then oxidizing it with m-chloroperbenzoic acid.

[0258] The obtained compound (AE) 1 H-NMR measurement and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=3.40-3.85(42H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0259] [Example 6] The compound represented by the above formula (AF) was obtained by the method shown below. The same operation as in Example 1 was performed, except that the compound represented by formula (5-6) was used instead of the compound represented by formula (5-1), to obtain 2.84 g of compound (AF) (Rf1 in formula (AF) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which represents the average degree of polymerization, is 4.5, and i, which represents the average degree of polymerization, is 4.5).

[0260] The compound represented by formula (5-6) was synthesized by subjecting the compound represented by formula (5-3) to an addition reaction with allyl alcohol, protecting the hydroxyl group of the resulting compound with dihydropyran, and then oxidizing it with m-chloroperbenzoic acid.

[0261] The obtained compound (AF) 1 H-NMR measurement and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.65-1.85(4H), 3.40-3.85(34H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0262] [Example 7] The compound represented by the above formula (AG) was obtained by the method shown below. The same procedure as in Example 1 was performed, except that the compound represented by formula (5-7) was used instead of the compound represented by formula (5-1), to obtain 2.84 g of compound (AG) (Rf1 in formula (AG) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0263] The compound of formula (5-7) was synthesized by subjecting the compound of formula (5-1) to an addition reaction with 3-buten-1-ol, protecting the hydroxyl group of the resulting compound with dihydropyran, and then oxidizing it with m-chloroperbenzoic acid.

[0264] The obtained compound (AG) 1 H-NMR measurement and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.65-1.85(4H), 3.40-3.85(42H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0265] [Example 8] The compound represented by the above formula (AH) was obtained by the method shown below. (First reaction) In the same manner as in the first reaction of Example 1, a compound represented by formula (11) was obtained as intermediate compound 1a.

[0266] (Second reaction) The same procedure as in the first reaction of Example 1 was carried out, except that the compound represented by formula (5-5) was used instead of the compound represented by formula (5-1), to obtain a compound represented by formula (12) as intermediate compound 1b.

[0267] [ka] (Rf1 in formula (12) is a PFPE chain represented by the above formula (4-1); in Rf1, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5; THP represents a tetrahydropyranyl group.)

[0268] (Third reaction) Next, 9.66 g of the compound represented by formula (11), which is the intermediate compound 1a obtained above, 0.69 g of the compound represented by formula (9-1), and 20 mL of t-butanol were charged into a 100 mL recovery flask under a nitrogen gas atmosphere, and the mixture was stirred at room temperature until it became homogeneous. 0.45 g of potassium tert-butoxide was added to the mixture, and the mixture was reacted by stirring at 70°C for 16 hours.

[0269] 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 oxidized with m-chloroperbenzoic acid and then purified by silica gel column chromatography to obtain 6.48 g of the compound represented by the following formula (13) as intermediate compound 1-4.

[0270] [ka] (Rf1 in formula (13) is a PFPE chain represented by the above formula (4-1); in Rf1, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5; THP represents a tetrahydropyranyl group.)

[0271] (Fourth reaction) Next, 7.21 g of the compound represented by formula (12), which is intermediate compound 1b obtained above, 6.48 g of the compound represented by formula (13), which is intermediate compound 1-4 obtained above, and 20 mL of t-butanol were charged into a 100 mL recovery flask under a nitrogen gas atmosphere, and the mixture was stirred at room temperature until it became homogeneous. 0.45 g of potassium tert-butoxide was added to the mixture, and the mixture was reacted by stirring at 70°C for 16 hours.

[0272] After the reaction, the resulting reaction mixture was returned to room temperature, and 50 g of a 10% hydrogen chloride-methanol solution (hydrogen chloride-methanol reagent (5-10%), manufactured by Tokyo Chemical Industry Co., Ltd.) was added and stirred at room temperature for 4 hours. The reaction mixture was then transferred in small portions to a separatory funnel containing 100 mL of saturated aqueous sodium bicarbonate and extracted twice with 200 mL of ethyl acetate. The organic layer was washed sequentially with 100 mL of brine, 100 mL of saturated aqueous sodium bicarbonate, and 100 mL of brine, and then dehydrated over anhydrous sodium sulfate. After filtering off the desiccant, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 4.34 g of compound (AH). (Rf1 in formula (AH) represents the PFPE chain represented by formula (4-1) above. In the two Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5.)

[0273] The obtained compound (AH) 1 H-NMR measurement and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=3.40-3.85(36H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0274] [Example 9] The compound represented by the above formula (AI) was obtained by the method shown below. The same operation as in Example 1 was performed, except that the compound represented by formula (5-8) was used instead of the compound represented by formula (5-1), to obtain 3.06 g of compound (AI) (Rf1 in formula (AI) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0275] The compound represented by formula (5-8) was synthesized by protecting one hydroxyl group of 1,6-hexanediol with dihydropyran, followed by reaction with epibromohydrin.

[0276] The obtained compound (AI) 1 H-NMR measurement and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.25-1.85(16H), 3.40-3.85(30H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0277] [Example 10] The compound represented by the above formula (AJ) was obtained by the method shown below. The same procedure as in Example 1 was performed, except that the compound represented by formula (5-9) was used instead of the compound represented by formula (5-1), to obtain 2.81 g of compound (AJ) (Rf1 in formula (AJ) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which represents the average degree of polymerization, is 4.5, and i, which represents the average degree of polymerization, is 4.5).

[0278] The compound represented by formula (5-9) was synthesized by protecting the hydroxyl group of 7-octen-1-ol with dihydropyran, followed by oxidation with m-chloroperbenzoic acid.

[0279] The obtained compound (AJ) 1 H-NMR measurement and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.25-1.85(16H), 3.40-3.85(22H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0280] [Example 11] The compound represented by the above formula (AK) was obtained by the method shown below. The same operation as in Example 1 was performed, except that the compound represented by formula (5-10) was used instead of the compound represented by formula (5-1), to obtain 2.61 g of compound (AK) (Rf1 in formula (AK) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which represents the average degree of polymerization, is 4.5, and i, which represents the average degree of polymerization, is 4.5).

[0281] The compound represented by formula (5-10) was synthesized by protecting the hydroxyl group of 2-bromoethanol with dihydropyran, reacting it with 5-hexen-1-ol, and then oxidizing it with m-chloroperbenzoic acid.

[0282] The obtained compound (AK) 1 H-NMR measurement and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.25-1.85(12H), 3.40-3.85(30H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0283] [Example 12] The compound represented by the above formula (AL) was obtained by the method shown below. The same operation as in Example 1 was performed, except that the compound represented by formula (5-11) was used instead of the compound represented by formula (5-1), to obtain 2.42 g of compound (AL) (Rf1 in formula (AL) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which represents the average degree of polymerization, is 4.5, and i, which represents the average degree of polymerization, is 4.5).

[0284] The compound represented by formula (5-11) was synthesized by reacting N-(2-hydroxyethyl)acetamide with epibromohydrin.

[0285] The obtained compound (AL) 1 H-NMR measurement and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.90-2.05(6H), 3.40-3.85(28H), 3.85-4.10(8H), 6.30-6.50(2H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0286] [Example 13] The compound represented by the above formula (AM) was obtained by the method shown below. The same operation as in Example 1 was performed, except that the compound represented by formula (5-12) was used instead of the compound represented by formula (5-1), to obtain 2.65 g of compound (AM) (Rf1 in formula (AM) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which represents the average degree of polymerization, is 4.5, and i, which represents the average degree of polymerization, is 4.5).

[0287] The compound represented by formula (5-12) was synthesized by reacting 2-cyanoethanol with epibromohydrin.

[0288] The obtained compound (AM) 1 H-NMR measurement and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=2.00~2.10(4H), 3.40-3.85(24H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0289] [Example 14] The compound represented by the above formula (AN) was obtained by the method shown below. The same operation as in Example 1 was performed, except that the compound represented by formula (7-2) was used instead of the compound represented by formula (7-1), to obtain 2.41 g of compound (AN) (Rf1 in formula (AN) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which represents the average degree of polymerization, is 4.5, and i, which represents the average degree of polymerization, is 4.5).

[0290] The compound represented by formula (7-2) was synthesized by oxidizing allyl glycidyl ether with m-chloroperbenzoic acid.

[0291] The obtained compound (AN) 1 H-NMR measurement and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=3.40-3.85(34H), 3.85-4.10(8H) 19F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0292] [Example 15] The compound represented by the above formula (AO) was obtained by the method shown below. The same operations as in Example 1 were performed, except that the compound represented by formula (5-5) was used instead of the compound represented by formula (5-1), and the compound represented by formula (7-2) was used instead of the compound represented by formula (7-1), to obtain 2.41 g of compound (AO) (Rf1 in formula (AO) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which represents the average degree of polymerization, is 4.5, and i, which represents the average degree of polymerization, is 4.5).

[0293] The resulting compound (AO) 1 H-NMR measurement and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=3.40-3.85(46H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0294] [Example 16] The compound represented by the above formula (AP) was obtained by the method shown below. The same operation as in Example 1 was performed, except that the compound represented by formula (7-3) was used instead of the compound represented by formula (7-1), to obtain 2.56 g of compound (AP) (Rf1 in formula (AP) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0295] The compound represented by formula (7-3) was synthesized by reacting one molecule of epibromohydrin with two molecules of allyl alcohol, protecting the secondary hydroxyl group of the compound produced after the reaction with dihydropyran, and then oxidizing it with m-chloroperbenzoic acid.

[0296] The obtained compound (AP) 1 H-NMR measurement and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=3.40-3.85(40H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0297] [Example 17] The compound represented by the above formula (AQ) was obtained by the method shown below. HOCH2CF2O(CF2CF2O) h (CF2O) i Instead of the compound represented by CF2CH2OH, HOCH2CF2CF2O(CF2CF2CF2O) j The same procedures as in Example 1 were carried out except that a compound (number average molecular weight 1000, molecular weight distribution 1.1) represented by CF2CF2CH2OH (where j, representing the average degree of polymerization, is 4.5) was used, and 2.74 g of compound (AQ) (Rf2 in formula (AQ) is a PFPE chain represented by the above formula (4-2). In Rf2, j, representing the average degree of polymerization, is 4.5) was obtained.

[0298] The obtained compound (AQ) 1 H-NMR measurement and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=3.40-3.85(30H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(36F), -86.4(8F), -124.3(8F), -130.0~-129.0(18F)

[0299] [Example 18] The compound represented by the above formula (AR) was obtained by the method shown below. HOCH2CF2O(CF2CF2O) h (CF2O) i Instead of the compound represented by CF2CH2OH, HOCH2CF2CF2CF2O(CF2CF2CF2CF2O) k The same operations as in Example 1 were performed except that a compound (number average molecular weight 1000, molecular weight distribution 1.1) represented by CF2CF2CF2CH2OH (where k, indicating the average degree of polymerization, is 3.0) was used, and 2.67 g of compound (AR) (Rf3 in formula (AR) is a PFPE chain represented by the above formula (4-3). In Rf3, k, indicating the average degree of polymerization, is 3.0) was obtained.

[0300] The obtained compound (AR) 1 H-NMR measurement and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=3.40-3.85(30H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(32F), -122.5(8F), -126.0(24F), -129.0~-128.0(8F)

[0301] [Example 19] The compound represented by the above formula (AS) was obtained by the method shown below. (First reaction) In the same manner as in the first reaction of Example 1, a compound represented by formula (11) was obtained as intermediate compound 1-2.

[0302] (Second reaction) Next, 9.25 g of the compound represented by formula (11), which is intermediate compound 1-2 obtained above, 2.15 g of the compound represented by formula (14) below, and 20 mL of dimethylformamide were charged into a 100 mL recovery flask under a nitrogen gas atmosphere, and the mixture was stirred at room temperature until it became homogeneous. 2.88 g of cesium carbonate was added to the mixture, and the mixture was reacted by stirring at 70°C for 16 hours.

[0303] [ka] (In formula (14), Ts represents a tosyl group (p-toluenesulfonyl group).)

[0304] 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 oxidized with m-chloroperbenzoic acid and then purified by silica gel column chromatography to obtain 7.22 g of the compound represented by the following formula (15) as intermediate compound 1-3.

[0305] [ka] (Rf1 in formula (15) is a PFPE chain represented by the above formula (4-1); in Rf1, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5; THP represents a tetrahydropyranyl group.)

[0306] (Third reaction) Next, 7.21 g of the compound represented by formula (15), which is intermediate compound 1-3 obtained above, 1.51 g of the compound represented by formula (16) below, and 20 mL of dimethylformamide were charged into a 100 mL recovery flask under a nitrogen gas atmosphere, and the mixture was stirred at room temperature until it became homogeneous. 0.45 g of sodium hydride was added to the mixture, and the mixture was reacted by stirring at 40°C for 16 hours.

[0307] [ka] (In formula (16), THP represents a tetrahydropyranyl group.)

[0308] After the reaction, the resulting reaction mixture was returned to room temperature, and 50 g of a 10% hydrogen chloride-methanol solution (hydrogen chloride-methanol reagent (5-10%), Tokyo Chemical Industry Co., Ltd.) was added and stirred at room temperature for 4 hours. The reaction mixture was then transferred in small portions to a separatory funnel containing 100 mL of saturated aqueous sodium bicarbonate and extracted twice with 200 mL of ethyl acetate. The organic layer was washed sequentially with 100 mL of brine, 100 mL of saturated aqueous sodium bicarbonate, and 100 mL of brine, and then dehydrated 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 3.51 g of compound (AS). Rf1 in formula (AS) represents the PFPE chain represented by formula (4-1) above. For the two Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5.

[0309] The obtained compound (AS) 1 H-NMR measurement and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=3.40-3.85(38H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0310] [Example 20] The compound represented by the above formula (AT) was obtained by the method shown below. The same operations as in Example 19 were performed, except that in the first reaction of Example 19, intermediate compound 1-2 was synthesized using a compound represented by the following formula (17) instead of the compound represented by formula (5-1), to obtain 3.28 g of compound (AT) (Rf1 in formula (AT) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which represents the average degree of polymerization, is 4.5, and i, which represents the average degree of polymerization, is 4.5).

[0311] [ka] (In formula (17), THP represents a tetrahydropyranyl group.)

[0312] The compound represented by formula (17) was synthesized by protecting the hydroxyl group of allyl alcohol with dihydropyran, followed by oxidation with m-chloroperbenzoic acid.

[0313] The obtained compound (AT) 1 H-NMR measurement and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=3.40-3.85(30H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0314] [Example 21] The compound represented by the above formula (AU) was obtained by the method shown below. The same procedure as in Example 1 was performed, except that a compound represented by formula (5-13) was used instead of the compound represented by formula (5-1) in Example 1, to obtain 2.04 g of compound (AU) (Rf1 in formula (AU) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which represents the average degree of polymerization, is 4.5, and i, which represents the average degree of polymerization, is 4.5).

[0315] The compound represented by formula (5-13) was synthesized by reacting salicylamide with epibromohydrin.

[0316] The obtained compound (AU) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=3.40-3.85(20H), 3.85-4.10(8H), 6.70-8.20(12H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0317] [Example 22] The compound represented by the above formula (AV) was obtained by the method shown below. The same procedure as in Example 1 was performed, except that the compound represented by formula (5-14) was used instead of the compound represented by formula (5-1) in Example 1, to obtain 2.21 g of compound (AV) (Rf1 in formula (AV) is a PFPE chain represented by the above formula (4-1). In the two Rf1s, h, which represents the average degree of polymerization, is 4.5, and i, which represents the average degree of polymerization, is 4.5).

[0318] The compound represented by formula (5-14) was synthesized by reacting 3-cyanophenol with epibromohydrin.

[0319] The resulting compound (AV) 1 H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=3.40-3.85(20H), 3.85-4.10(8H), 7.20-7.60(8H) 19F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0320] [Example 23] The compound represented by the above formula (BA) was obtained by the method shown below. The same operations as in Example 1 were performed, except that a compound represented by the following formula (18) was used instead of the compound represented by formula (7-1), to obtain 3.61 g of compound (BA) (Rf1 in formula (BA) is a PFPE chain represented by the above formula (4-1). In the three Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0321] [ka] (Rf1 in formula (18) is a PFPE chain represented by the above formula (4-1); in Rf1, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5.)

[0322] The compound represented by formula (18) is HOCH2CF2O(CF2CF2O) h (CF2O) i The compound (number average molecular weight: 1000, molecular weight distribution: 1.1) represented by CF2CH2OH (where h, representing the average degree of polymerization, is 4.5, and i, representing the average degree of polymerization, is 4.5) was reacted with the compound represented by formula (9-1), followed by oxidation with m-chloroperbenzoic acid to synthesize the compound.

[0323] The resulting compound (BA) 1 H-NMR measurement and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=3.40-3.85(38H), 3.85-4.10(12H) 19F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0324] [Example 24] The compound represented by the above formula (BB) was obtained by the method shown below. The same operation as in Example 23 was performed except that the compound represented by formula (5-5) was used instead of the compound represented by formula (5-1), to obtain 3.76 g of compound (BB) (Rf1 in formula (BB) is a PFPE chain represented by the above formula (4-1). In the three Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0325] The obtained compound (BB) 1 H-NMR measurement and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=3.40-3.85(50H), 3.85-4.10(12H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0326] [Example 25] The compound represented by the above formula (BC) was obtained by the method shown below. The same operation as in Example 23 was performed except that the compound represented by formula (5-3) was used instead of the compound represented by formula (5-1), to obtain 3.43 g of compound (BC) (Rf1 in formula (BC) is a PFPE chain represented by the above formula (4-1). In the three Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0327] The resulting compound (BC) 1 H-NMR measurement and 19F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.65-1.85(4H), 3.40-3.85(30H), 3.85-4.10(12H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0328] [Example 26] The compound represented by the above formula (BD) was obtained by the method shown below. The same operation as in Example 23 was performed except that the compound represented by formula (5-4) was used instead of the compound represented by formula (5-1), to obtain 3.43 g of compound (BD) (Rf1 in formula (BD) is a PFPE chain represented by the above formula (4-1). In the three Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0329] The obtained compound (BD) 1 H-NMR measurement and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.65-1.85(4H), 3.40-3.85(42H), 3.85-4.10(12H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0330] [Example 27] The compound represented by the above formula (BE) was obtained by the method shown below. The same operation as in Example 23 was performed except that the compound represented by formula (5-11) was used instead of the compound represented by formula (5-1), to obtain 3.56 g of compound (BE) (Rf1 in formula (BE) is a PFPE chain represented by the above formula (4-1). In the three Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0331] The resulting compound (BE) 1 H-NMR measurement and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.90-2.05(6H), 3.40-3.85(36H), 3.85-4.10(12H), 6.30-6.50(2H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0332] [Example 28] The compound represented by the above formula (BF) was obtained by the method shown below. The same operation as in Example 23 was performed except that the compound represented by formula (5-12) was used instead of the compound represented by formula (5-1), to obtain 3.82 g of compound (BF) (Rf1 in formula (BF) is a PFPE chain represented by the above formula (4-1). In the three Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0333] The resulting compound (BF) 1 H-NMR measurement and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=2.00~2.10(4H), 3.40-3.85(32H), 3.85-4.10(12H) 19F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0334] [Example 29] The compound represented by the above formula (BG) was obtained by the method shown below. The same operations as in Example 23 were performed except that the compound represented by formula (9-2) was used instead of the compound represented by formula (9-1), to obtain 3.06 g of compound (BG) (Rf1 in formula (BG) is a PFPE chain represented by the above formula (4-1). In the three Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0335] The obtained compound (BG) 1 H-NMR measurement and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=3.40-3.85(46H), 3.85-4.10(12H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0336] [Example 30] The compound represented by the above formula (BH) was obtained by the method shown below. The same operations as in Example 23 were performed except that the compound represented by formula (9-3) was used instead of the compound represented by formula (9-1), to obtain 3.14 g of compound (BH) (Rf1 in formula (BH) is a PFPE chain represented by the above formula (4-1). In the three Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0337] The compound represented by formula (9-3) was synthesized by reacting one molecule of epibromohydrin with two molecules of allyl alcohol, protecting the secondary hydroxyl group of the resulting compound with dihydropyran, and oxidizing one of the carbon-carbon double bonds with m-chloroperbenzoic acid.

[0338] The resulting compound (BH) 1 H-NMR measurement and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=3.40-3.85(58H), 3.85-4.10(12H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0339] [Example 31] The compound represented by the above formula (BI) was obtained by the method shown below. The same procedure as in Example 23 was performed, except that a compound represented by the following formula (19) was used instead of the compound represented by formula (18), to obtain 3.24 g of compound (BI) (Rf1 in formula (BI) is a PFPE chain represented by the above formula (4-1). In the three Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0340] [ka] (Rf1 in formula (19) is a PFPE chain represented by the above formula (4-1); in Rf1, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5.)

[0341] The compound represented by formula (19) was prepared by the following method: HOCH2CF2O(CF2CF2O) h (CF2O) iA compound (number average molecular weight 1000, molecular weight distribution 1.1) represented by CF2CH2OH (where h, indicating the average degree of polymerization, is 4.5, and i, indicating the average degree of polymerization, is 4.5) was reacted with 1,3-butadiene monoepoxide. The resulting compound was then reacted with epibromohydrin. The resulting compound was then treated with m-chloroperbenzoic acid to oxidize the carbon-carbon double bond, thereby synthesizing the compound.

[0342] The obtained compound (BI) 1 H-NMR measurement and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=3.40-3.85(36H), 3.85-4.10(12H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0343] [Example 32] The compound represented by the above formula (BJ) was obtained by the method shown below. HOCH2CF2O(CF2CF2O) h (CF2O) i Instead of the compound represented by CF2CH2OH, HOCH2CF2CF2O(CF2CF2CF2O) j The same procedures as in Example 23 were performed except that a compound (number average molecular weight 1000, molecular weight distribution 1.1) represented by CF2CF2CH2OH (where j, representing the average degree of polymerization, is 4.5) was used, and 2.74 g of compound (BJ) (Rf2 in formula (BJ) is a PFPE chain represented by the above formula (4-2). In the three Rf2s, j, representing the average degree of polymerization, is 4.5) was obtained.

[0344] The obtained compound (BJ) 1 H-NMR measurement and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1H-NMR (acetone-D6): δ[ppm]=3.40-3.85(38H), 3.85-4.10(12H) 19 F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(54F), -86.4(12F), -124.3(12F), -130.0~-129.0(27F)

[0345] [Example 33] The compound represented by the above formula (BK) was obtained by the method shown below. The same procedure as in Example 29 was performed, except that the compound represented by formula (5-12) was used instead of the compound represented by formula (5-1), to obtain 3.21 g of compound (BK) (Rf1 in formula (BK) is a PFPE chain represented by the above formula (4-1). In the three Rf1s, h, which indicates the average degree of polymerization, is 4.5, and i, which indicates the average degree of polymerization, is 4.5).

[0346] The obtained compound (BK) 1 H-NMR measurement and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=2.00~2.10(4H), 3.40-3.85(40H), 3.85-4.10(12H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0347] The compounds (AA) to (AV) and (BA) to (BK) of Examples 1 to 33 thus obtained are respectively substituted into the formula (1), and the value of x, R 1 , R 2 , R 3 , R 4 The structures of the compounds are shown in Table 1. All compounds except for compound (AH) are R 1 and R 4 The structure is the same.

[0348] [Table 1]

[0349] [Comparative Example 1] The compound represented by the following formula (ZA) was synthesized by the method described in Patent Document 1.

[0350] [ka] (Rf1 in formula (ZA) is a PFPE chain represented by the above formula (4-1); in the two Rf1s, h representing the average degree of polymerization is 7.0, and i representing the average degree of polymerization is 0.)

[0351] Comparative Example 2 The compound represented by the following formula (ZB) was synthesized by the method described in Patent Document 2.

[0352] [ka] (Rf1 in formula (ZB) is a PFPE chain represented by the above formula (4-1); in the two Rf1s, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5.)

[0353] Comparative Example 3 The compound represented by the following formula (ZC) was synthesized by the method described in Patent Document 3.

[0354] [ka] (Rf1 in formula (ZC) is a PFPE chain represented by the above formula (4-1); in the two Rf1s, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5.)

[0355] Comparative Example 4 The compound represented by the following formula (ZD) was synthesized by the method described in Patent Document 4.

[0356] [ka] (Rf2 in formula (ZD) is a PFPE chain represented by the above formula (4-2); in the two Rf2s, j representing the average degree of polymerization is 4.5.)

[0357] Comparative Example 5 The compound represented by the following formula (ZE) was synthesized by the method described in Patent Document 5.

[0358] [ka] (Rf1 in formula (ZE) is a PFPE chain represented by the above formula (4-1); in the two Rf1s, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5.)

[0359] Comparative Example 6 The compound represented by the following formula (ZF) was synthesized by the method shown below.

[0360] [ka] (Rf1 in formula (ZF) is a PFPE chain represented by the above formula (4-1); in the two Rf1s, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5.)

[0361] The same operations as in Example 1 were performed, except that the compound represented by formula (5-1) was replaced with the compound represented by formula (17) above, and the compound represented by formula (7-2) was replaced with the compound represented by formula (7-1), to obtain 2.21 g of compound (ZF) (Rf1 in formula (ZF) is a PFPE chain represented by formula (4-1) above. In the two Rf1s, h, which represents the average degree of polymerization, is 4.5, and i, which represents the average degree of polymerization, is 4.5).

[0362] The resulting compound (ZF) 1H-NMR and 19 F-NMR measurements were carried out and the structure was identified based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=3.40-3.85(26H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0363] Comparative Example 7 The compound represented by the following formula (ZG) was synthesized by the method described in Patent Document 6.

[0364] [ka] (Rf1 in formula (ZG) is a PFPE chain represented by the above formula (4-1); in the three Rf1s, h representing the average degree of polymerization is 7.0, and i representing the average degree of polymerization is 0.)

[0365] [Comparative Example 8] The compound represented by the following formula (ZH) was synthesized by the method described in Patent Document 7.

[0366] [ka] (Rf1 in formula (ZH) is a PFPE chain represented by the above formula (4-1); in the two Rf1s, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5.)

[0367] Comparative Example 9 The compound represented by the following formula (ZI) was synthesized by the method described in Patent Document 8.

[0368] [ka] (Rf1 in formula (ZI) is a PFPE chain represented by the above formula (4-1); in the three Rf1s, h representing the average degree of polymerization is 4.5, and i representing the average degree of polymerization is 4.5.)

[0369] The number average molecular weights (Mn) of the compounds thus obtained in Examples 1 to 33 and Comparative Examples 1 to 9 were measured by the above-mentioned method. The results are shown in Tables 2 and 3.

[0370] Next, solutions for forming lubricating layers were prepared by the method described below using the compounds obtained in Examples 1 to 33 and Comparative Examples 1 to 9. 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 33 and Comparative Examples 1 to 9.

[0371] "Lubricant layer forming solution" The compounds obtained in Examples 1 to 33 and Comparative Examples 1 to 9 were each dissolved in a fluorine-based solvent, Vertrel (registered trademark) XF (trade name, manufactured by Mitsui DuPont Fluorochemicals Co., Ltd.), and diluted with Vertrel XF so that the film thickness when applied to the protective layer would be 9.0 Å to 9.5 Å, to prepare a solution for forming a lubricating layer.

[0372] "Magnetic recording media" A magnetic recording medium was prepared by sequentially depositing an adhesive layer, a soft magnetic layer, a first underlayer, a second underlayer, a magnetic layer, and a protective layer on a substrate having a diameter of 65 mm. The protective layer was made of carbon. On the protective layer of a magnetic recording medium on which each layer up to the protective layer had been formed, the lubricating layer-forming solutions of Examples 1 to 33 and Comparative Examples 1 to 9 were applied by dipping under the conditions of an immersion speed of 10 mm / sec, an immersion time of 30 seconds, and a pull-up speed of 1.2 mm / sec. The magnetic recording medium coated with the lubricating layer-forming solution was then placed in a thermostatic chamber, and a heat treatment was performed at 120°C for 10 minutes to remove the solvent in the lubricating layer-forming solution and improve the adhesion between the protective layer and the lubricating layer, thereby forming a lubricating layer on the protective layer and obtaining a magnetic recording medium.

[0373] (film thickness measurement) The thickness of the lubricating layer of each of the magnetic recording media thus obtained in Examples 1 to 33 and Comparative Examples 1 to 9 was measured using a Fourier transform infrared spectrophotometer (FT-IR, product name: Nicolet iS50, manufactured by Thermo Fisher Scientific). The results are shown in Tables 2 and 3.

[0374] Next, the magnetic recording media of Examples 1 to 33 and Comparative Examples 1 to 9 were subjected to the following flying stability test and pickup characteristic test.

[0375] [Floating stability test] The following glide tests and credence measurements were carried out, and the flying stability was evaluated based on the following evaluation criteria. The results are shown in Tables 2 and 3.

[0376] "Glide Test" The glide test checks for protrusions on the surface of magnetic recording media. That is, when using a magnetic head to record or reproduce data on a magnetic recording medium, if there are protrusions on the surface of the magnetic recording medium that are higher than the flying height (the distance between the magnetic recording medium and the magnetic head), the magnetic head may collide with the protrusions, causing damage to the magnetic head or defects in the magnetic recording medium. In the glide test, 50 magnetic recording media are inspected for the presence of protrusions on the surface that are higher than the flying height.

[0377] Specifically, the distance between the testing magnetic head and the magnetic recording medium was set to 0.25 microinches, and the testing magnetic head was moved over the magnetic recording medium. If the testing magnetic head output a signal due to a collision with a protrusion on the surface of the magnetic recording medium, the magnetic recording medium was judged to be defective, and all other magnetic recording media were judged to be pass. Then, the number of magnetic recording media judged to be pass out of the 50 magnetic recording media was used for evaluation.

[0378] "Credence measurement" During the glide test, noise temporarily increases, and even at the same location on the magnetic recording medium, signals resulting from collisions with surface protrusions may or may not be detected during multiple measurements. This phenomenon is called creedence. Creedence is not detected as a protrusion in the glide test and is not used to determine whether the glide test passed or failed. However, a temporary increase in noise during the glide test generally indicates unevenness in the lubricant layer or the presence of relatively soft foreign matter. For this reason, the glide test was performed on magnetic recording media, and the average greedence value was calculated by dividing the total number of creedence events detected by the number of magnetic recording media (50) tested. This value was used as an index of the smoothness and cleanliness of the lubricant layer.

[0379] "Evaluation Criteria" A+: 45 or more glide test passes and average credence less than 0.5 A: Glide test pass count is 45 or more and credence average is 0.5 or more but less than 1.0 B: Glide test pass count is 45 or more and credence average is 1.0 or more but less than 5.0 C: 45 or more glide test passes and average credence of 5.0 or more D: Less than 45 sheets passed the glide test

[0380] [Pickup characteristic test] The magnetic recording medium and magnetic head were mounted on a spin stand and rotated under reduced pressure (approximately 250 torr) at room temperature, allowing the magnetic head to float at a fixed point for 10 minutes. The surface of the magnetic head facing the magnetic recording medium was then analyzed using an ESCA (Electron Spectroscopy for Chemical Analysis) analyzer. The intensity of the fluorine-derived peak (signal intensity (au)) obtained by the analysis using the ESCA analyzer indicates the amount of lubricant attached to the magnetic head. The obtained signal intensity was used to evaluate the pickup characteristics according to the following evaluation criteria.

[0381] "Evaluation Criteria" A+: Signal strength less than 120 (almost no adhesion) A: Signal strength 120 or more but less than 180 (very little adhesion) B: Signal strength 180 or more but less than 300 (low adhesion amount) C: Signal strength 300 or more but less than 1000 (high adhesion) D: Signal strength 1000 or more (very high adhesion)

[0382] [comprehensive evaluation] Based on the results of the flying stability test and the pickup characteristic test, a comprehensive evaluation was made based on the following criteria. "comprehensive evaluation" A: Both the flying stability test and the pickup characteristics test were evaluated as A+ or A. B: Either the flying stability test or the pickup characteristics test was rated B, and the other was rated A+, A, or B. C: Either the flying stability test or the pickup characteristics test was rated C, and the other was rated A+, A, B, or C. D: At least one of the evaluations of the flying stability test and the pickup characteristics test is D

[0383] [Table 2]

[0384] [Table 3]

[0385] As shown in Table 2, R 1 and R 4 is a terminal group represented by any one of formulas (3-1) to (3-4), and R 3The magnetic recording media of Examples 1 to 33, which used compounds (AA) to (AV) and (BA) to (BK) represented by formula (1), in which at least one of the groups is a divalent linking group represented by formula (2-1) or (2-2), were evaluated as A+, A, or B in the flying stability test and the pickup characteristic test, and all were evaluated as A or B overall. This confirmed that the lubricating layers of the magnetic recording media of Examples 1 to 33 had good flying stability and a high pickup suppression effect.

[0386] The magnetic recording media of Examples 1 to 4, 12 to 14, 17 to 23, 25 to 29, 32, and 33, which used compounds (AA) to (AD), (AL) to (AN), (AQ) to (AV), (BA), (BC) to (BG), (BJ), and (BK), were rated A+ or A in the flying stability test and the pickup characteristic test, and the overall rating was A. Compounds (AA)-(AD), (AL)-(AN), (AQ)-(AT), (BA), (BC)-(BG), (BJ), and (BK) are x R 3 The number of hydroxyl groups contained in each is two, and R 1 and R 4 The number of polar groups contained in each is two, and R 1 and R 4 are each represented by one of formulas (3-1) to (3-3), and R 1 and R 4 The alkylene chain in the main chain portion of the formula (3-1) is not too long (the sum of p and r in the formula (3-1) is 3 or less, t in the formula (3-2) is 4 or less, and the total number of carbon atoms and oxygen atoms in Y in the formula (3-3) is 3 or less). 3 The number of hydroxyl groups contained in R is two, 1 and R 4 The number of polar groups contained in each is two, and R 1 and R 4 is expressed by equation (3-4).

[0387] Among the above compounds, R 3 is the formula (2-1), and R 1 and R 4In Examples 12, 21, and 27, which used compounds (AL), (AU), and (BE) containing a group having an amide bond, the flying stability test was evaluated as A, and the pickup characteristics test was evaluated as A+, which were excellent results. Also, x is 2 and R 3 is equation (2-2) where l=1 and R 1 and R 4 Example 33, which used a compound (BK) containing a cyano group, was evaluated as A+ in the flying stability test and also as A in the pickup characteristics test, showing excellent results. In the compounds of Examples 12, 21, 27 and 33, R 1 and R 4 The strength of the interaction between the active sites on the protective layer and R 3 It is presumed that the balance between the strength of the interaction between the active sites on the protective layer and the surface of the catalyst was appropriate.

[0388] In contrast, in Comparative Examples 1 to 9, which used compounds (ZA) to (ZI), the flying stability test and the pickup characteristic test were all rated C or D, and the overall rating was D. More specifically, in Comparative Examples 1, 2, 8, and 9, which used compounds (ZA), (ZB), (ZH), and (ZI) in which the linking group arranged between adjacent perfluoropolyether chains contained only one hydroxyl group, the results of the floating stability test were D. This is thought to be because the number of hydroxyl groups in the linking group was insufficient, preventing sufficient interaction between the linking group and the protective layer, causing the center part of the fluorinated ether compound to float up and resulting in a loss of smoothness of the lubricating layer.

[0389] In addition, in Comparative Examples 3 and 4, which used compounds (ZC) and (ZD), in which the linking group between adjacent perfluoropolyether chains had two hydroxyl groups but a rigid alkylene chain with four methylene groups bonded between the carbon atoms to which the hydroxyl groups were bonded, the results of the floating stability test were D. This is presumably because the rigid alkylene chain of the linking group restricted the movement of the hydroxyl groups contained in the linking group. As a result, insufficient interaction was obtained between the linking group portion of the compound and the protective layer, and the center portion of the compound floated up, causing the smoothness of the lubricating layer to be lost.

[0390] Furthermore, in Comparative Examples 1, 4 to 7, which used compounds (ZA), (ZD) to (ZG) having terminal groups in which carbon atoms bonded to hydroxyl groups are directly bonded to each other, the pickup characteristics test was evaluated as D. In these compounds, the hydroxyl groups contained in the terminal groups are close to each other, so the intramolecular interaction between the adjacent hydroxyl groups takes precedence over the interaction between the hydroxyl groups and the protective layer. Therefore, it is thought that sufficient interaction between the terminal groups and the protective layer is not obtained, and the terminal portions of the compounds rise up, making them more likely to be adsorbed to the magnetic head.

[0391] In addition, in Comparative Example 9, which used a compound (ZI) in which one of the terminal groups contained only one hydroxyl group, the pickup characteristic test was evaluated as D. This is presumably because the number of hydroxyl groups in the terminal groups was insufficient, and therefore sufficient interaction between the terminal groups and the protective layer was not obtained. As a result, the terminal portions of the compound were presumably raised, making them more likely to be adsorbed to the magnetic head. [Industrial Applicability]

[0392] 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 flying stability and a high pick-up suppression effect. [Explanation of symbols]

[0393] 10...magnetic recording medium, 11...substrate, 12...adhesion layer, 13...soft magnetic layer, 14...first underlayer, 15...second underlayer, 16...magnetic layer, 17...protective layer, 18...lubricating layer.

Claims

1. A fluorine-containing ether compound represented by the following formula (1): R １ -CH ２ -R ２ [-CH ２ -R ３ -CH ２ -R ２ ] ｘ -CH ２ -R ４ (1) (In formula (1), x represents an integer of 1 to 2; R ２ is a perfluoropolyether chain; (x+1) R ２ may be the same in part or in whole, or may be different from each other; R ３ is a divalent linking group having a hydroxyl group; x number of R ３ At least one of the R ３ may be the same or different; R １ and R ４ are each independently a terminal group represented by any one of the following formulas (3-1) to (3-4); R １ and R ４ may be the same or different from each other.) 【Chemical 1】 (In formula (2-2), l represents an integer of 1 to 2.) 【Chemistry 2】 (In formula (3-1), p represents an integer of 0 to 3, r represents an integer of 1 to 5, and the total value of p and r is 1 to 5; q represents an integer of 0 to 2; and A represents a polar group selected from the group consisting of a hydroxyl group, a cyano group, an acetamide group, and a carboxamide group.) (In formula (3-2), s represents an integer of 0 to 2, and t represents an integer of 1 to 5.) (In formula (3-3), u represents an integer of 2 to 4; Y represents a linear alkylene group which may have ether oxygen or a single bond; when Y is the alkylene group, the total number of carbon atoms and oxygen atoms contained in Y is 1 to 5.) (In formula (3-4), v represents an integer of 1 to 3; B represents a cyano group, an acetamide group, or a carboxamide group in which a hydrogen atom at any position on the benzene ring is substituted.)

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

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

4. x R in the formula (1) ３ The fluorine-containing ether compound according to any one of claims 1 to 3, wherein at least one of the following is represented by formula (2-1):

5. (x+1) R in the formula (1) ２ are each independently a perfluoropolyether chain represented by the following formula (4): -(CF ２ ) ｗ１ -O-(CF ２ O) ｗ２ -(CF ２ CF ２ O) ｗ３ -(CF ２ CF ２ CF ２ O) ｗ４ -(CF ２ CF ２ CF ２ CF ２ O) ｗ５ -(CF ２ ) ｗ６ - (4) (In formula (4), w2, w3, w4, and w5 represent average degrees of polymerization, each independently representing 0 to 20; provided that w2, w3, w4, and w5 cannot all be 0 at the same time; w1 and w6 are each independently a value of CF ２ is an average value representing the number of repeating units in formula (4), 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).

6. (x+1) R in the formula (1) ２ are each independently any one selected from perfluoropolyether chains represented by the following formulas (4-1) to (4-4): -CF ２ -(OCF ２ CF ２ ) ｈ -(OCF ２ ) ｉ -OCF ２ - (4-1) (In formula (4-1), h and i represent the average degree of polymerization, h represents 1 to 20, and i represents 0 to 20.) -CF ２ CF ２ -(OCF ２ CF ２ CF ２ ) ｊ -OCF ２ CF ２ - (4-2) (In formula (4-2), j represents the average degree of polymerization and represents 1 to 15.) -CF ２ CF ２ CF ２ -(OCF ２ CF ２ CF ２ CF ２ ) ｋ -OCF ２ CF ２ CF ２ - (4-3) (In formula (4-3), k represents the average degree of polymerization and represents 1 to 10.) -(CF ２ ) ｗ７ -O-(CF ２ CF ２ CF ２ O) ｗ８ -(CF ２ CF ２ O) ｗ９ -(CF ２ ) ｗ１０ - (4-4) (In formula (4-4), w8 and w9 represent the average degree of polymerization, each independently representing 1 to 20; w7 and w10 represent CF ２ is an average value representing the number of

7. The fluorine-containing ether compound according to any one of claims 1 to 3, which has a number average molecular weight in the range of 500 to 10,000.

8. A lubricant for magnetic recording media, comprising the fluorine-containing ether compound according to any one of claims 1 to 3.

9. A magnetic recording medium having at least a magnetic layer, a protective layer, and a lubricating layer sequentially provided on a substrate, 4. A magnetic recording medium, wherein the lubricating layer contains the fluorine-containing ether compound according to claim 1.

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

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