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

Abstract

This fluorine-containing ether compound is represented by the following formula. R1-R2-CH2-R3[-CH2-R4-CH2-R3]x-CH2-R5-R6 (where R1 and R6 are organic groups having 1-50 carbon atoms, R2 is formula (2-1) or (2-2), R5 is formula (2-3) or (2-4), R3 is a perfluoropolyether chain, R4 is formula (3-1) or (3-2), and x is 0-2.)

Description

[Technical Field]

[0001] The present invention relates to a fluorine-containing ether compound, a lubricant for magnetic recording media, and a magnetic recording media. This application claims priority based on Japanese Patent Application No. 2022-083154, filed in Japan on May 20, 2022, and the contents of that application are incorporated herein by reference. [Background technology]

[0002] To improve the recording density of magnetic recording and playback devices, development of magnetic recording media suitable for high recording densities is underway. Conventionally, magnetic recording media have consisted of a recording layer formed on a substrate, with a protective layer of carbon or similar material formed on top of 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 top of the recording layer does not provide sufficient durability for the magnetic recording media. For this reason, a lubricant is generally applied to the surface of the protective layer to form a lubricating layer.

[0003] As a lubricant used to form the lubricating layer of a magnetic recording medium, for example, a compound containing a polar group such as a hydroxyl group or an amino group at the end of a fluorine-based polymer having a repeating structure including -CF2- has been proposed.

[0004] For example, Patent Document 1 discloses a fluorine-containing ether compound in which a divalent linking group containing a secondary hydroxyl group and a terminal group are bonded to both ends of a perfluoropolyether chain via a methylene group (-CH2-) in that order. Furthermore, Patent Document 2 discloses a fluorine-containing ether compound in which a glycerin structure (-O-CH2-CH(OH)-CH2-O-) is positioned in the center of a chain-like structure, and on both sides, via methylene groups (-CH2-), a perfluoropolyether chain, a divalent linking group containing a secondary hydroxyl group, and a terminal group having a polar group are bonded in this order.

[0005] Furthermore, Patent Document 3 discloses a fluorine-containing ether compound in which a perfluoropolyether chain and a terminal group are bonded in this order via a methylene group (-CH2-) to both sides of a divalent linking group containing a primary hydroxyl group and a secondary hydroxyl group. Furthermore, Patent Document 4 discloses a fluorine-containing ether compound having a skeleton in which three perfluoropolyether chains are linked via linking groups having secondary hydroxyl groups, and on both sides thereafter, a divalent linking group containing a secondary hydroxyl group and a terminal group having a polar group are linked in that order via a methylene group (-CH2-).

[0006] Furthermore, Patent Document 5 discloses a method for producing polyol (per)fluoropolyether derivatives useful as lubricants for magnetic media. Patent Document 5 describes reacting a protected triol having two protected hydroxyl functional groups and one free hydroxyl group with an activator to produce an activated protected triol, and then subjecting it to a nucleophilic substitution reaction with a hydroxyl group located at the end of a functional (per)fluoropolyether derivative to produce a protected polyol (per)fluoropolyether derivative. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] International Publication No. 2017 / 154403 [Patent Document 2] International Publication No. 2021 / 251335 [Patent Document 3] International Publication No. 2021 / 019998 [Patent Document 4] U.S. Patent Application Publication No. 2016 / 0260452 [Patent Document 5] Patent No. 5334064 [Overview of the project] [Problems that the invention aims to solve]

[0008] In a magnetic recording and reproducing apparatus, there is an increasing demand for further reducing the flying height of the magnetic head. For this reason, it is required to make the thickness of the lubricating layer in the magnetic recording medium thinner. However, generally, when the thickness of the lubricating layer is reduced, the chemical resistance of the magnetic recording medium tends to decrease. In addition, 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.

[0009] The present invention has been made in view of the above circumstances, and an object thereof is to provide a fluorine-containing ether compound that can form a lubricating layer having excellent chemical resistance and capable of suppressing pickup, and can be suitably used as a material for a lubricant for a magnetic recording medium. Another object of the present invention is to provide a lubricant for a magnetic recording medium that contains the fluorine-containing ether compound of the present invention, can form a lubricating layer having good chemical resistance and a high pickup suppressing effect. Another object of the present invention is to provide a magnetic recording medium having a lubricating layer containing the fluorine-containing ether compound of the present invention, having good chemical resistance and a high pickup suppressing effect.

Means for Solving the Problems

[0010] The present invention includes the following aspects. The first aspect of the present invention provides the following fluorine-containing ether compound.

[0011] [1] A fluorine-containing ether compound characterized by being represented by the following formula (1). R 6 , x , 6 , 1 , 5 , 3 , , 2 -R 2 -CH2-R 3 [-CH2-R 4 -CH2-R 3 x -CH2-R 5 -R 6 (1) (In formula (1), R 1 and R 6 are each independently an organic group having 1 to 50 carbon atoms; R 2 ​R is a divalent linking group represented by the following formula (2-1) or (2-2); R 5 R is a divalent linking group represented by the following formulas (2-3) or (2-4); x represents an integer from 0 to 2; R 3 R is a perfluoropolyether chain; if x is 1 or 2, then 2 or 3 R 3 They may be partially or entirely the same, or they may be different; R 4 R is a divalent linking group represented by the following formula (3-1) or (3-2); when x is 2, two R 4 They may be the same, or they may be different.

[0012] [ka] (In equation (2-1), n1 represents an integer from 2 to 4; in equation (2-1), the dotted line bonded to the carbon atom is R 1 The dotted lines indicate bonds with the oxygen atom, and the dotted lines indicate bonds with the methylene group. (In equation (2-2), the dotted line bonded to the carbon atom is R 1 The dotted lines indicate bonds with the oxygen atom, and the dotted lines indicate bonds with the methylene group. (In equation (2-3), n² represents an integer between 2 and 4; in equation (2-3), the dotted line bonded to the carbon atom is R 6 The dotted lines indicate bonds with the oxygen atom, and the dotted lines indicate bonds with the methylene group. (In equation (2-4), the dotted line bonded to the carbon atom is R 6 The dotted lines indicate bonds with the oxygen atom, and the dotted lines indicate bonds with the methylene group. (In equation (3-1), n3 represents an integer between 2 and 4; y1 represents an integer between 1 and 3; y2 represents an integer between 1 and 3; at least one of y1 and y2 is 1; the dotted line bonded to the oxygen atom on the left is R 1 The dotted line indicates the bond to the methylene group on the side, and the bond to the oxygen atom on the right is R. 6(This shows the bond connecting to the methylene group on the side.) (In equation (3-2), y3 represents an integer from 1 to 3; y4 represents an integer from 1 to 3; at least one of y3 and y4 is 1; the dotted line bonded to the oxygen atom on the left is R 1 The dotted line indicates the bond to the methylene group on the side, and the bond to the oxygen atom on the right is R. 6 (This shows the bond connecting to the methylene group on the side.)

[0013] The fluorine-containing ether compound of the first embodiment of the present invention preferably has the following characteristics [2] to

[10] . Two or more of the following characteristics [2] to

[10] may also be arbitrarily combined. [2] R in equation (1) above 2 The above equation (2-1) is, and R 5 The above equation (2-3) is given by x R 4 The fluorine-containing ether compound according to [1], wherein all are of formula (3-1), and in formula (3-1), y1 is 1 and y2 is 1. [3] The fluorine-containing ether compound according to [2], wherein the values ​​of n1 in formula (2-1), n2 in formula (2-3), and n3 in formula (3-1) are all the same.

[0014] [4] R in equation (1) above 2 The above equation (2-2) is, and R 5 The above equation (2-4) is given by x R 4 The fluorine-containing ether compound according to [1], wherein all are of formula (3-2), and in formula (3-2), y3 is 1 and y4 is 1.

[0015] [5] R in equation (1) above 1 and R 6 Each of these is independently one of the following: an organic group having a polar group, an organic group having a carbon-carbon unsaturated bond, or an organic group having both a polar group and a carbon-carbon unsaturated bond. The polar group is at least one selected from the group consisting of a hydroxyl group, an amino group, a carboxyl group, a formyl group, a carbonyl group, a sulfo group, a cyano group, and a group having an amide bond. The fluorine-containing ether compound according to any one of [1] to [4], wherein the carbon-carbon unsaturated bond is at least one selected from the group consisting of an aromatic hydrocarbon group which may have substituents, an unsaturated heterocyclic group, an alkenyl group, and an alkynyl group.

[0016] [6] R in equation (1) above 1 and R 6 A fluorine-containing ether compound according to any of [1] to [5], wherein the total number of polar groups contained is 1 to 4. [7] R in equation (1) above 1 -R 2 -and R 6 -R 5 A fluorine-containing ether compound as described in any of [1] to [6], wherein the - is the same.

[0017] [8] (x+1) R in equation (1) above 3 A fluorine-containing ether compound according to any of [1] to [7], wherein each of the following is an independent perfluoropolyether chain represented by formula (4) below. -(CF2) w1 -O-(CF2O) w2 -(CF2CF2O) w3 -(CF2CF2CF2O) w4 -(CF2CF2CF2CF2O) w5 -(CF2) w6 - (4) (In equation (4), w2, w3, w4, and w5 represent the average degree of polymerization, each independently representing 0 to 20; however, w2, w3, w4, and w5 cannot all be 0 at the same time; w1 and w6 are average values ​​representing the number of CF2 molecules, each independently representing 1 to 3; there are no particular restrictions on the order of the repeating units (CF2O), (CF2CF2O), (CF2CF2CF2O), and (CF2CF2CF2CF2O) in equation (4).)

[0018] [9] (x+1) R in equation (1) above 3 A fluorine-containing ether compound according to any one of [1] to [7], wherein each of the elements is independently selected from one of the perfluoropolyether chains represented by the following formulas (4-1) to (4-4). -CF2-(OCF2CF2) h -(OCF2) i -OCF2- (4-1) (In equation (4-1), h and i represent the average degree of polymerization, where h is between 1 and 20, and i is between 0 and 20.) -CF2CF2-(OCF2CF2CF2) j -OCF2CF2- (4-2) (In equation (4-2), j represents the average degree of polymerization and is expressed as 1 to 15.) -CF2CF2CF2-(OCF2CF2CF2CF2) k -OCF2CF2CF2- (4-3) (In equation (4-3), k represents the average degree of polymerization and is expressed as 1 to 10.) -(CF2) w7 -O-(CF2CF2CF2O) w8 -(CF2CF2O) w9 -(CF2) w10 - (4-4) (In equation (4-4), w8 and w9 represent the average degree of polymerization, each independently representing 1 to 20; w7 and w10 are average values ​​representing the number of CF2s, each independently representing 1 to 2.)

[0019]

[10] A fluorine-containing ether compound according to any of [1] to [9], wherein the number average molecular weight is in the range of 500 to 10000. A second aspect of the present invention provides the following lubricant for magnetic recording media. A lubricant for magnetic recording media, characterized by containing a fluorine-containing ether compound as described in any of [1] to

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

[12] A magnetic recording medium having at least a magnetic layer, a protective layer, and a lubricating layer sequentially provided on a substrate, A magnetic recording medium characterized in that the lubricating layer contains a fluorine-containing ether compound as described in any of [1] to

[10] . A magnetic recording medium according to a third aspect of the present invention preferably has the features described in

[13] below.

[13] The magnetic recording medium according to

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

[0020] 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 magnetic recording media. The lubricant for magnetic recording media of the present invention contains the fluorine-containing ether compound of the present invention, and therefore has good chemical resistance and can form a lubricating layer with a high pickup suppression effect.

[0021] The magnetic recording medium of the present invention has a lubricating layer containing the fluorine-containing ether compound of the present invention. Therefore, the magnetic recording medium of the present invention has good chemical resistance, a high pickup suppression effect, and excellent reliability and durability. Furthermore, because the lubricating layer of the magnetic recording medium of the present invention has good chemical resistance and can suppress pickup, its thickness can be reduced and the amount of magnetic head levitation can be reduced. [Brief explanation of the drawing]

[0022] [Figure 1] This is a schematic cross-sectional view showing one embodiment of the magnetic recording medium of the present invention. [Modes for carrying out the invention]

[0023] To solve the above problems, the inventors have diligently conducted research as described below. Conventionally, fluorine-containing ether compounds having polar groups such as hydroxyl groups have been preferably used as materials for lubricants for magnetic recording media applied to the surface of protective layers (hereinafter sometimes abbreviated as "lubricant"). The polar groups contained in fluorine-containing ether compounds bind to active sites on the protective layer, improving the adhesion of the lubricant layer to the protective layer. In conventional fluorine-containing ether compounds, polar groups are located at the ends of the chain structure. Furthermore, if the fluorine-containing ether compound has multiple perfluoropolyether chains, polar groups are located between adjacent perfluoropolyether chains.

[0024] However, when using conventional lubricants to form a thin lubricating layer on the protective layer, it was difficult to achieve a lubricating layer with good chemical resistance and a high pickup suppression effect. One possible reason for this is the presence of polar groups in the fluorine-containing ether compound in the lubricating layer that are not adsorbed to the numerous active sites on the protective layer.

[0025] If polar groups that are not adsorbed on the active sites on the protective layer are present in the fluorine-containing ether compound contained in the lubricating layer, contaminants are more easily incorporated near these polar groups, reducing the chemical resistance of the lubricating layer. In addition, polar groups in the fluorine-containing ether compound that are not adsorbed on the active sites on the protective layer may be adsorbed on the magnetic head, and this can trigger the pickup of the fluorine-containing ether compound by the magnetic head. For these reasons, if polar groups that are not adsorbed on the active sites on the protective layer are present in the fluorine-containing ether compound contained in the lubricating layer, the chemical resistance and pickup suppression effect of the lubricating layer tend to be insufficient.

[0026] Therefore, the inventors focused on the behavior of bonding between polar groups contained in fluorine-containing ether compounds and active sites on the protective layer, and diligently conducted research to realize a fluorine-containing ether compound in which polar groups that do not participate in bonding with active sites on the protective layer are less likely to be generated. As a result, the inventors found that among the polar groups contained in fluorine-containing ether compounds, secondary hydroxyl groups contained in divalent linking groups positioned between adjacent perfluoropolyether chains and between perfluoropolyether chains and terminal groups are less likely to be involved in binding with active sites on the protective layer.

[0027] Therefore, the inventors chemically modified the secondary hydroxyl groups in the divalent linking groups located between adjacent perfluoropolyether chains and between perfluoropolyether chains and terminal groups of the fluorine-containing ether compound to convert them into primary hydroxyl groups. Then, they formed a lubricating layer using the modified fluorine-containing ether compound. As a result, it was found that chemical resistance and pickup suppression effects were improved. This is presumed to be because the fluorine-containing ether compound became less likely to generate hydroxyl groups that do not bind to active sites present on the protective layer.

[0028] Furthermore, the inventors have conducted extensive research and found that a fluorine-containing ether compound can be formed in which a specific divalent terminal linking group having only one primary hydroxyl group is positioned between each perfluoropolyether chain and terminal group, and if there are two or three perfluoropolyether chains, a specific divalent intermediate linking group having only one primary hydroxyl group is positioned between adjacent perfluoropolyether chains. Each of the two terminal linking groups (or, in the case of multiple perfluoropolyether chains, two terminal linking groups and one or two intermediate linking groups) has a side chain portion that branches off from the chain structure of the fluorine-containing ether compound and is ether-bonded. The side chain portion has a primary hydroxyl group positioned at its tip and has a linking group containing a methylene group (-CH2-) that bonds the carbon atom to which the primary hydroxyl group is bonded to to the oxygen atom bonded to the carbon atom in the chain structure.

[0029] In such fluorine-containing ether compounds, polar groups that do not bond with functional groups (active sites) present on the protective layer are less likely to form for the reasons described below. Therefore, it is presumed that these fluorine-containing ether compounds will form a lubricating layer that has excellent chemical resistance and a high pickup suppression effect.

[0030] In other words, each of the two terminal linking groups (or, in the case of multiple perfluoropolyether chains, the two terminal linking groups and one or two intermediate linking groups) has only one primary hydroxyl group, and is sterically less spaced compared to the case where a secondary hydroxyl group is present instead of a primary hydroxyl group. Therefore, the primary hydroxyl groups of the two terminal linking groups (or the two terminal linking groups and one or two intermediate linking groups) are less likely to have their binding to the active site on the protective layer inhibited by bulky parts in the fluorine-containing ether compound, such as the adjacent perfluoropolyether chain or the tertiary carbon to which the side chain portions of each terminal linking group (or the two terminal linking groups and one or two intermediate linking groups) are bonded. Moreover, primary hydroxyl groups are generally more mobile than secondary hydroxyl groups. Therefore, the primary hydroxyl groups of the two terminal linking groups (or the two terminal linking groups and one or two intermediate linking groups) can each spontaneously move toward the active site on the protective layer. Based on these findings, the primary hydroxyl groups of the two terminal linking groups (or the two terminal linking groups and one or two intermediate linking groups) can easily form bonds with active sites on the protective layer.

[0031] Furthermore, in the above-mentioned fluorine-containing ether compounds, terminal linking groups are positioned between both terminal groups and the perfluoropolyether chain. Therefore, the distance between the primary hydroxyl group of the terminal linking group located at one end of the chain structure and the primary hydroxyl group of the terminal linking group located at the other end of the chain structure does not become too close. Also, if the above-mentioned fluorine-containing ether compound has multiple perfluoropolyether chains, a perfluoropolyether chain is positioned between each terminal linking group and one or two intermediate linking groups. Therefore, the distance between the primary hydroxyl group of each terminal linking group and the primary hydroxyl group of one or two intermediate linking groups does not become too close. Furthermore, if the above-mentioned fluorine-containing ether compound has three perfluoropolyether chains, there are two intermediate linking groups. In this case, a perfluoropolyether chain is positioned between adjacent intermediate linking groups, so the distance between the primary hydroxyl groups of adjacent intermediate linking groups does not become too close.

[0032] Therefore, in the above-mentioned fluorine-containing ether compounds, the primary hydroxyl groups of the two terminal linking groups (or, in the case of multiple perfluoropolyether chains, the two terminal linking groups and one or two intermediate linking groups) are less likely to have their binding to active sites on the protective layer inhibited by the primary hydroxyl groups of other terminal linking groups (or other terminal linking groups and intermediate linking groups) contained in the fluorine-containing ether compound. Furthermore, in the above-mentioned fluorine-containing ether compounds, the distance between the primary hydroxyl groups of the two terminal linking groups (or the distance between the primary hydroxyl groups of each terminal linking group, the distance between the primary hydroxyl groups of each terminal linking group and the primary hydroxyl groups of one or two intermediate linking groups, and the distance between the primary hydroxyl groups of adjacent intermediate linking groups) is never too close. For this reason, the primary hydroxyl groups of the two terminal linking groups (or, the terminal linking groups and one or two intermediate linking groups) are less likely to aggregate.

[0033] Furthermore, in the above-mentioned fluorine-containing ether compounds, the two terminal linking groups (or the two terminal linking groups and one or two intermediate linking groups) each have only one primary hydroxyl group and possess side chain portions that branch off from the chain structure of the fluorine-containing ether compound and are ether-bonded. In the above-mentioned fluorine-containing ether compounds, because the side chain portions of the two terminal linking groups (or the two terminal linking groups and one or two intermediate linking groups) branch off from the chain structure and are ether-bonded, the flexibility of the side chain portions is better compared to the case where the side chain portions are directly bonded to the chain structure (bonded by carbon-carbon bonds). Therefore, the primary hydroxyl groups on the side chain portions of the two terminal linking groups (or the two terminal linking groups and one or two intermediate linking groups) can easily form bonds with active sites on the protective layer.

[0034] Furthermore, in the above-mentioned fluorine-containing ether compounds, in the side chain portions of the two terminal linking groups (or the two terminal linking groups and one or two intermediate linking groups), the carbon atom to which the primary hydroxyl group located at the end is bonded and the oxygen atom bonded to the carbon atom in the chain structure are linked by a linking group containing a methylene group (-CH2-). Therefore, even if the terminal group contains a polar group, the distance between the polar group of the terminal group and the primary hydroxyl group of the terminal linking group adjacent to the terminal group is appropriate. As a result, the primary hydroxyl group of the terminal linking group is less likely to have its binding to the active site on the protective layer inhibited by the polar group of the terminal group. Also, because the distance between the primary hydroxyl group of the terminal linking group and the polar group of the terminal group is appropriate, even if the terminal group contains a polar group, aggregation of the primary hydroxyl group of the terminal linking group adjacent to the terminal group and the polar group of the terminal group is less likely.

[0035] As explained above, in the above-mentioned fluorine-containing ether compound, the side chain portions of the two terminal linking groups (or the two terminal linking groups and one or two intermediate linking groups) have good flexibility, the primary hydroxyl groups of the side chain portions can move spontaneously and are less prone to aggregation, and the primary hydroxyl groups of the other terminal linking groups (or the other terminal linking groups and intermediate linking groups), the polar groups of the terminal groups, and the bulky portions in the fluorine-containing ether compound are less likely to inhibit binding with the active sites on the protective layer. For these reasons, the above-mentioned fluorine-containing ether compound is less likely to produce polar groups that do not bind to functional groups (active sites) present on the protective layer. As a result, it is estimated that the above-mentioned fluorine-containing ether compound is less likely to incorporate contaminants, has good chemical resistance, is less likely to be picked up by magnetic heads, and can form a lubricating layer with a high pickup suppression effect.

[0036] Furthermore, the inventors of the present invention have come up with the present invention after confirming that by using a lubricant containing the above-mentioned fluorine-containing ether compound, it is possible to form a lubricating layer with good chemical resistance and a high pickup suppression effect. The following describes in detail preferred examples of the fluorine-containing ether compound, lubricant for magnetic recording media, and magnetic recording media of the present invention. However, the present invention is not limited to the embodiments shown below. Within the scope of the present invention, additions, omissions, substitutions, and modifications are possible regarding the number, quantity, position, ratio, material, composition, etc.

[0037] [Fluorine-containing ether compounds] The fluorine-containing ether compound of this embodiment is represented by the following formula (1). R 1 -R 2 -CH2-R 3 [-CH2-R 4 -CH2-R 3 ] x -CH2-R 5 -R 6 (1) (In formula (1), R 1 and R 6 Each of these is an organic group with 1 to 50 carbon atoms; R2 R is a divalent linking group represented by the following formula (2-1) or (2-2); R 5 R is a divalent linking group represented by the following formulas (2-3) or (2-4); x represents an integer from 0 to 2; R 3 R is a perfluoropolyether chain; if x is 1 or 2, then 2 or 3 R 3 They may be partially or entirely the same, or they may be different; R 4 R is a divalent linking group represented by the following formula (3-1) or (3-2); when x is 2, two R 4 They may be the same, or they may be different.

[0038] [ka] (In equation (2-1), n1 represents an integer from 2 to 4; in equation (2-1), the dotted line bonded to the carbon atom is R 1 The dotted lines indicate bonds with the oxygen atom, and the dotted lines indicate bonds with the methylene group. (In equation (2-2), the dotted line bonded to the carbon atom is R 1 The dotted lines indicate bonds with the oxygen atom, and the dotted lines indicate bonds with the methylene group.

[0039] [ka] (In equation (2-3), n² represents an integer between 2 and 4; in equation (2-3), the dotted line bonded to the carbon atom is R 6 The dotted lines indicate bonds with the oxygen atom, and the dotted lines indicate bonds with the methylene group. (In equation (2-4), the dotted line bonded to the carbon atom is R 6 The dotted lines indicate bonds with the oxygen atom, and the dotted lines indicate bonds with the methylene group.

[0040] [ka] (In equation (3-1), n3 represents an integer between 2 and 4; y1 represents an integer between 1 and 3; y2 represents an integer between 1 and 3; at least one of y1 and y2 is 1; the dotted line bonded to the oxygen atom on the left is R 1 The dotted line indicates the bond to the methylene group on the side, and the bond to the oxygen atom on the right is R. 6 (This shows the bond connecting to the methylene group on the side.) (In equation (3-2), y3 represents an integer from 1 to 3; y4 represents an integer from 1 to 3; at least one of y3 and y4 is 1; the dotted line bonded to the oxygen atom on the left is R 1 The dotted line indicates the bond to the methylene group on the side, and the bond to the oxygen atom on the right is R. 6 (This shows the bond connecting to the methylene group on the side.)

[0041] The fluorine-containing ether compound of this embodiment has only one primary hydroxyl group, as shown in formula (1). 2 The divalent terminal linking group shown by and R 3 The 1-3 perfluoropolyether chains (hereinafter sometimes referred to as PFPE chains) shown by and the 0-2 R groups having only one primary hydroxyl group 4 R has a divalent intermediate linking group and only one primary hydroxyl group. 5 It has a chain-like structure skeleton in which divalent terminal linking groups, represented by , are linked via methylene groups. 1 and R 6 Each of the terminal groups, consisting of organic groups with 1 to 50 carbon atoms as shown, is bonded to the structure.

[0042] In the fluorine-containing ether compound represented by formula (1), x represents an integer from 0 to 2. Since x is 2 or less, the fluorine-containing ether compound represented by formula (1) does not become too large in size. Therefore, it is a fluorine-containing ether compound that can move freely on the protective layer, spreads easily on the protective layer, and yields a lubricating layer with a uniform film thickness. Furthermore, it is preferable that x be 1 or 2, as this results in a fluorine-containing ether compound that has even better chemical resistance and can form a lubricating layer with a higher pickup suppression effect.

[0043] (R 2 and R 5 a divalent terminal linking group having only one primary hydroxyl group represented by) In the fluorine-containing ether compound represented by formula (1), R 2 and R 5 is a divalent terminal linking group having only one primary hydroxyl group. In the fluorine-containing ether compound represented by formula (1), R 2 and R 5 do not have a secondary hydroxyl group and have only one primary hydroxyl group. Therefore, compared with the case where R 2 and R 5 each have a secondary hydroxyl group, the hydroxyl groups contained in R 2 and R 5 are likely to interact with the active sites on the protective layer. From this, when a lubricating layer is formed on the protective layer using a lubricant containing the fluorine-containing ether compound represented by formula (1), a suitable interaction occurs between the lubricating layer and the protective layer. Therefore, the fluorine-containing ether compound represented by formula (1) has excellent chemical resistance and can form a lubricating layer with a high pickup suppression effect.

[0044] R 2 is a divalent linking group represented by formula (2-1) or (2-2). R 2 is such that the terminal on the R 3 side is an oxygen atom. The terminal on the R 2 side of R 3 is bonded to the methylene group bonded to R 3 by an ether bond. R 2 is such that the terminal on the R 1 side is a carbon atom. The terminal on the R 2 side of R 1 is bonded to R 1 . R 2 is the main chain portion forming the chain structure of the fluorine-containing ether compound, and the R 2 side of R 1It has a side chain portion that branches off from the main chain portion at the carbon atom located at the end of the side and is bonded via an ether linkage. The side chain portion has a primary hydroxyl group at its tip and contains a linking group containing a methylene group (-CH2-) that bonds the carbon atom to which the primary hydroxyl group is bonded to to the oxygen atom (etheric oxygen atom) bonded to the carbon atom of the main chain portion.

[0045] R 2 R 1 The carbon atom located at the end of the side has R as a side chain portion. 2 Due to the ether bond contained in, -(CH2) in formula (2-1) n1 OH or -CH2CH2OCH2CH2OH in formula (2-2) is bonded. In this embodiment, R 2 R 1 The carbon atom located at the terminal end of the side, 2 The side chain portion is ether-bonded, 2 R 1 The carbon atom located at the terminal end of the side, 2 Compared to the case where the side chain portion is directly bonded (bonded by a carbon-carbon bond), R 2 The side chain portion has good flexibility. Moreover, in this embodiment, R 2 The side chain portion has a chain-like structure of appropriate length that includes a linking group. Therefore, R 2 The side chain portion readily interacts with active sites on the protective layer.

[0046] In equation (2-1), n1 is an integer between 2 and 4. If n1 is 2 or greater, R 2 The primary hydroxyl group contained in the fluorine-containing ether compound, and the PFPE chain, R 2 R 1 The distance to bulky parts such as tertiary carbons located at the end of the side becomes sufficiently large, R 2 The primary hydroxyl group contained in becomes more mobile. Also, when n1 is 4 or less, -(CH2) in formula (2-1) n1 The flexibility of OH is maintained. n1 is -(CH2) n1 Since OH can move flexibly, it is preferable that the number be between 2 and 3, and most preferably 2. In equation (2-2), -CH2CH2OCH2CH2OH contains an ether bond (-O-). Therefore, the -CH2CH2OCH2CH2OH in equation (2-2) maintains its kinetic flexibility.

[0047] R 5 R is a divalent linking group represented by formula (2-3) or (2-4). 5 R 3 The end of the side is an oxygen atom. 5 R 3 The terminal end is connected by an ether bond, R 3 It bonds with the methylene group that is bonded to it. 5 R 6 The terminal end is a carbon atom. 5 R 6 The end on the side is R 6 It is connected to this. R 5 The main chain portion forms the chain-like structure of the fluorine-containing ether compound, and R 5 R 6 It has a side chain portion that branches off from the main chain portion at the carbon atom located at the end of the side and is ether-bonded. 2 Similarly, the side chain portion has a primary hydroxyl group at its tip and a linking group containing a methylene group (-CH2-) that connects the carbon atom to which the primary hydroxyl group is bonded to with the oxygen atom (etheric oxygen atom) bonded to the carbon atom of the main chain portion.

[0048] R 5 R 6 The carbon atom located at the end of the side has R as a side chain portion. 5 Due to the ether bond contained in, -(CH2) in formula (2-3) n2 OH or -CH2CH2OCH2CH2OH in formula (2-4) is bonded. In this embodiment, R 5 R 6 The carbon atom located at the terminal end of the side, 5 The side chain portion is ether-bonded, 5 R 6 The carbon atom located at the terminal end of the side, 5Compared to the case where the side chain portion is directly bonded (bonded by a carbon-carbon bond), R 5 The side chain portion has good flexibility. Moreover, in this embodiment, R 5 The side chain portion has a chain-like structure of appropriate length that includes a linking group. Therefore, R 5 The side chain portion readily interacts with active sites on the protective layer.

[0049] In equation (2-3), n² is an integer between 2 and 4. If n² is 2 or greater, R 5 The primary hydroxyl group contained in the fluorine-containing ether compound, and the PFPE chain, R 5 R 6 The distance to bulky parts such as tertiary carbons located at the end of the side becomes sufficiently large, R 5 The primary hydroxyl group contained in becomes more mobile. Also, when n2 is 4 or less, -(CH2) in equation (2-3) n1 The flexibility of OH is maintained. n2 is -(CH2) n2 Since OH can move flexibly, it is preferable that the number be between 2 and 3, and most preferably 2. In equation (2-4), -CH2CH2OCH2CH2OH contains an ether bond (-O-). Therefore, the -CH2CH2OCH2CH2OH in equation (2-4) maintains its kinetic flexibility.

[0050] R 2 and R 5 They may be the same or they may be different. 2 and R 5 If these properties are the same, it results in a fluorine-containing ether compound that is easy to manufacture, which is preferable. In this specification, "R 2 and R 5 "They are the same" means that the -CH2-R group located in the center of the fluorine-containing ether compound represented by formula (1) is the same. 3 [-CH2-R 4 -CH2-R 3 ] x For the structure represented by -CH2-, R 2 Atoms and R contained in 5This means that the atoms contained within are arranged symmetrically. In other words, the fluorine-containing ether compound represented by formula (1) is R 2 Equation (2-1) and R 5 A fluorine-containing ether compound such that is given by formula (2-3) and n1 in formula (2-1) and n2 in formula (2-3) are the same, or R 2 Equation (2-2) is given by R 5 It is preferable that the compound is a fluorine-containing ether compound of formula (2-4).

[0051] (R 4 (A divalent intermediate linking group having only one primary hydroxyl group, as shown by) In the fluorine-containing ether compound represented by formula (1), when x is 1 or 2, R 3 Each PFPE chain represented by -CH2-R 4 They bond to each other via -CH2-. If x is 1 or 2, then x R 4 R is a divalent intermediate linking group having only one primary hydroxyl group. In the fluorine-containing ether compound represented by formula (1), x R 4 Each of them does not have a secondary hydroxyl group, but has only one primary hydroxyl group. Therefore, x R 4 Compared to the case where each has a secondary hydroxyl group, R 4 The hydroxyl groups contained in (1) readily interact with active sites on the protective layer. Therefore, when a lubricating layer is formed on the protective layer using a lubricant containing a fluorine-containing ether compound represented by formula (1), a suitable interaction occurs between the lubricating layer and the protective layer. Thus, the fluorine-containing ether compound represented by formula (1) can form a lubricating layer with excellent chemical resistance and a high pickup suppression effect.

[0052] R 4 R is a divalent linking group represented by formula (3-1) or (3-2). 4 In this case, both ends are oxygen atoms. 4 The ends on both sides are connected by ether bonds, R 3 It bonds with the methylene group that is bonded to it. R 4The main chain portion forms the chain-like structure of the fluorine-containing ether compound, and R 4 The molecule has side chains that branch off from the main chain and are ether-bonded at the oxygen atoms located at both ends of the main chain, with carbon atoms bonded to each other via 1 to 3 methylene groups. The side chains have a primary hydroxyl group at their tip and a linking group containing a methylene group (-CH2-) that bonds the carbon atom to which the primary hydroxyl group is bonded to to the oxygen atom (etheric oxygen atom) bonded to the carbon atom of the main chain.

[0053] R 4 Each of the two oxygen atoms located at the ends on both sides of the molecule, and the carbon atoms bonded via 1-3 methylene groups, have a side chain portion, which is -(CH2) in formula (3-1) via an ether bond. n3 OH or -CH2CH2OCH2CH2OH in formula (3-2) is bonded. In this embodiment, R 4 R 4 The side chain portion is ether-bonded, 4 R 4 Compared to the case where the side chain portion is directly bonded (bonded by a carbon-carbon bond), R 4 The side chain portion has good flexibility. Moreover, in this embodiment, R 4 The side chain portion has a chain-like structure of appropriate length that includes a linking group. Therefore, R 4 The side chain portion readily interacts with active sites on the protective layer.

[0054] In equation (3-1), n3 is an integer between 2 and 4. If n3 is 2 or greater, R 4 The primary hydroxyl group contained in the fluorine-containing ether compound, and the PFPE chain, R 4 A carbon atom that forms the main chain portion of R 4 The distance between the side chain portion and bulky sites such as tertiary carbons to which ether bonds are sufficiently large, R 4 The primary hydroxyl group contained in becomes more mobile. Also, when n3 is 4 or less, -(CH2) in formula (3-1) n3The flexibility of OH is maintained. n3 is -(CH2) n3 Since OH can move flexibly, it is preferable that the number be between 2 and 3, and most preferably 2.

[0055] In formula (3-1), y1 is an integer between 1 and 3, and y2 is an integer between 1 and 3. At least one of y1 and y2 is 1. Since at least one of y1 and y2 is 1, it becomes an easily manufactured fluorine-containing ether compound. When only y1 is 1, y2 (or when only y2 is 1, y1) is 3 or less, and preferably 2 or less, in order to maintain the flexibility of the entire divalent linking group represented by formula (3-1). More preferably, y1 is 1 and y2 is 1, in order to maintain the flexibility of the entire divalent linking group represented by formula (3-1).

[0056] In equation (3-2), -CH2CH2OCH2CH2OH contains an ether bond (-O-). Therefore, the -CH2CH2OCH2CH2OH in equation (3-2) maintains its kinetic flexibility.

[0057] In formula (3-2), y3 is an integer between 1 and 3, and y4 is an integer between 1 and 3. At least one of y3 and y4 is 1. Because at least one of y3 and y4 is 1, it becomes an easily manufactured fluorine-containing ether compound. When only y3 is 1, y4 (or when only y4 is 1, y3) is preferably 3 or less and 2 or less in order to maintain the flexibility of the entire divalent linking group represented by formula (3-2). More preferably, y3 is 1 and y4 is 1 in order to maintain the flexibility of the entire divalent linking group represented by formula (3-2).

[0058] In equation (1), when x is 2, the two R 4 They may be the same or they may be different. 4 If the two R's are the same, it results in an easily manufactured fluorine-containing ether compound, which is preferable. 4 "They are the same" means that two R 4The atoms contained in are R located at the center of the molecular chain structure. 3 This means that they are symmetrically arranged with respect to x. That is, when x is 2, the fluorine-containing ether compound represented by equation (1) has two R 4 Equation (3-1) is given by two R 4 The n3 in equation (3-1) is the same, and the two R 4 In equation (3-1) in which y1 and y2 are R located in the center of the chain structure 3 A fluorine-containing ether compound with a value symmetric to that, or two R 4 Equation (3-2) is given by two R 4 In equation (3-2) in which y3 and y4 are R located in the center of the chain structure 3 It is preferable that the fluorine-containing ether compound has a value that is symmetric with respect to R. For example, R 1 R on the side 4 This is expressed by equation (3-1), where y1 is 1 and y2 is 2, and R 6 R on the side 4 If the expression is given by equation (3-1), and y1 in equation (3-1) is 2 and y2 is 1, and the value of n3 in equation (3-1) is the same for both, then the two R 4 They are the same. Also, for example, R 1 R on the side 4 This is expressed by equation (3-2), where y3 is 1 and y4 is 2, and R 6 R on the side 4 If the expression is given by equation (3-2), and y3 is 2 and y4 is 1 in equation (3-2), then the two R 4 They are the same.

[0059] In the fluorine-containing ether compound represented by formula (1), R 2 Equation (2-1) is given by R 5 Equation (2-3) is given by x R 4It is preferable that all of them are in formula (3-1). In this case, it is more preferable that y1 in formula (3-1) is 1 and y2 is 1. Furthermore, it is more preferable that the values ​​of n1 in formula (2-1), n2 in formula (2-3), and n3 in formula (3-1) are all the same. This is because it results in a fluorine-containing ether compound that can be easily and efficiently manufactured.

[0060] In the fluorine-containing ether compound represented by formula (1), R 2 Equation (2-2) is given by R 5 Equation (2-4) is given by x R 4 It is also preferable that all of them are of formula (3-2). This is because it results in a fluorine-containing ether compound that can be easily and efficiently manufactured. 2 Equation (2-2) is given by R 5 Equation (2-4) is given by x R 4 If all of them are equation (3-2), then it is more preferable that y3 in equation (3-2) is 1 and y4 is 1.

[0061] (R 3 (PFPE chain shown by) In the fluorine-containing ether compound represented by formula (1), the (x+1) R atoms are present. 3 These are each independently perfluoropolyether chains. 3 The PFPE chain shown in this embodiment, when a lubricant containing the fluorine-containing ether compound of this embodiment is applied to the protective layer to form a lubricating layer, covers the surface of the protective layer and imparts lubricity to the lubricating layer, thereby reducing the frictional force between the magnetic head and the protective layer. 3 The PFPE chain shown is appropriately selected according to the performance requirements of the lubricant containing the fluorine-containing ether compound.

[0062] In the fluorine-containing ether compound represented by formula (1), when x is 1 or 2, there are two or three R 3 These may be partially or entirely the same, or they may be different. (x+1) R 3It is preferable that all of them be the same. This is because a more uniform coating state of the protective layer of the fluorine-containing ether compound results in a lubricating layer with better adhesion. (x+1) R 3 Two or more of the R 3 The condition that (x+1) R's are the same is that 3 Among them, R has the same structure as the repeating unit of the PFPE chain. 3 This means that it contains two or more of the same R. 3 This includes those with the same repeating unit structure but different average degrees of polymerization.

[0063] R 3 Examples of PFPE chains represented by include those consisting of polymers or copolymers of perfluoroalkylene oxides. Examples of perfluoroalkylene oxides include perfluoromethylene oxide, perfluoroethylene oxide, perfluoro-n-propylene oxide, perfluoroisopropylene oxide, and perfluorobutylene oxide.

[0064] (x+1) Rs in equation (1) 3 Preferably, each of these is 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 equation (4), w2, w3, w4, and w5 represent the average degree of polymerization, each independently representing 0 to 20; however, w2, w3, w4, and w5 cannot all be 0 at the same time; w1 and w6 are average values ​​representing the number of CF2 molecules, each independently representing 1 to 3; there are no particular restrictions on the order of the repeating units (CF2O), (CF2CF2O), (CF2CF2CF2O), and (CF2CF2CF2CF2O) in equation (4).)

[0065] In formula (4), w2, w3, w4, and w5 represent the average degree of polymerization, each independently representing a range from 0 to 20, preferably from 0 to 15, and more preferably from 0 to 10. They may also be 1 to 8, 2 to 6, 3 to 5, etc. In equation (4), w1 and w6 are average values ​​indicating the number of CF2 units, each independently representing 1 to 3. w1 and w6 are determined according to the structure of the repeating units located at the ends of the chain structure in the PFPE chain represented by equation (4). In equation (4), (CF2O), (CF2CF2O), (CF2CF2CF2O), and (CF2CF2CF2CF2O) are repeating units. There are no particular restrictions on the order in which the repeating units are arranged in equation (4). There are also no particular restrictions on the number of different types of repeating units in equation (4).

[0066] (x+1) Rs in equation (1) 3 Preferably, each of these is independently selected from the PFPE chains represented by the following formulas (4-1) to (4-4). (x+1) R 3 However, if any one of the PFPE chains represented independently by formulas (4-1) to (4-4) is selected, it becomes a fluorine-containing ether compound that yields a lubricating layer with good lubricity. Also, (x+1) R 3 However, if one of the PFPE chains represented independently by formulas (4-1) to (4-4) is selected, the ratio of oxygen atoms (ether bond (-O-) number) to carbon atoms in the PFPE chain is appropriate. As a result, a fluorine-containing ether compound with appropriate hardness is formed. Therefore, the fluorine-containing ether compound applied to the protective layer is less likely to aggregate on the protective layer, and a thinner lubricating layer can be formed with sufficient coverage. In addition, because the fluorine-containing ether compound has appropriate flexibility, a lubricating layer with better chemical resistance can be formed.

[0067] -CF2-(OCF2CF2) h -(OCF2) i -OCF2- (4-1) (In equation (4-1), h and i represent the average degree of polymerization, where h is between 1 and 20, and i is between 0 and 20.) -CF2CF2-(OCF2CF2CF2) j -OCF2CF2- (4-2) (In equation (4-2), j represents the average degree of polymerization and is expressed as 1 to 15.) -CF2CF2CF2-(OCF2CF2CF2CF2) k -OCF2CF2CF2- (4-3) (In equation (4-3), k represents the average degree of polymerization and is expressed as 1 to 10.) -(CF2) w7 -O-(CF2CF2CF2O) w8 -(CF2CF2O) w9 -(CF2) w10 - (4-4) (In equation (4-4), w8 and w9 represent the average degree of polymerization, each independently representing 1 to 20; w7 and w10 are average values ​​representing the number of CF2s, each independently representing 1 to 2.)

[0068] In formula (4-1), there are no particular restrictions on the sequence order of the repeating units, (OCF2CF2) and (OCF2). In formula (4-1), the number of (OCF2CF2) units h and the number of (OCF2) units i may be the same or different. The PFPE chain represented by formula (4-1) may be a polymer of (OCF2CF2). Furthermore, the PFPE chain represented by formula (4-1) may be a random copolymer, block copolymer, or alternating copolymer composed of (OCF2CF2) and (OCF2).

[0069] In formulas (4-1) to (4-3), the average degree of polymerization is 1 to 20 for h, 0 to 20 for i, 1 to 15 for j, and 1 to 10 for k, resulting in a fluorine-containing ether compound that yields a lubricating layer with good lubricity. Furthermore, in formulas (4-1) to (4-3), the average degrees of polymerization are 20 or less for h and i, 15 or less for j, and 10 or less for k, so the viscosity of the fluorine-containing ether compound does not become too high, making it easy to apply lubricants containing it, which is preferable. The average degrees of polymerization of h, i, j, and k are preferably 1 to 10, more preferably 1.5 to 8, and even more preferably 2 to 7, as this results in a fluorine-containing ether compound that spreads easily on the protective layer and yields a lubricating layer with a uniform film thickness.

[0070] In formula (4-4), there are no particular restrictions on the order of the repeating units (CF2CF2CF2O) and (CF2CF2O). In formula (4-4), the number of (CF2CF2CF2O) units w8 and the number of (CF2CF2O) units w9, which indicate the average degree of polymerization, may be the same or different. Formula (4-4) may include any of the monomer units (CF2CF2CF2O) and (CF2CF2O), such as a random copolymer, a block copolymer, or an alternating copolymer.

[0071] 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 equation (4-4), w7 and w10 are average values ​​indicating the number of CF2 units, and each independently represents 1 to 2. w7 and w10 are determined according to the structure of the repeating units located at the ends of the chain structure in the PFPE chain represented by equation (4-4).

[0072] (R 1 and R 6 (Terminal group indicated by) In the fluorine-containing ether compound represented by formula (1), R 1 and R 6 The terminal groups indicated by are each independently organic groups having 1 to 50 carbon atoms.1 and R 6 The terminal groups indicated by are preferably, independently, organic groups having 1 to 20 carbon atoms, and more preferably organic groups having 2 to 10 carbon atoms.

[0073] R 1 The terminal group indicated by is R 2 It is preferable that the end that bonds with R is a carbon atom. 6 The terminal group indicated by is R 5 It is preferable that the end that bonds with is a carbon atom. This allows R 1 (or R 6 If the terminal group indicated by ) has a polar group, R 2 (or R 5 The primary hydroxyl group of ) and R 1 (or R 6 The distance from the polar group of ) becomes even more optimal. As a result, R 1 (or R 6 ) adjacent to R 2 (or R 5 The primary hydroxyl group of ) is R 1 (or R 6 The polar groups present in ) make it even less likely for the binding to the active site on the protective layer to be inhibited.

[0074] R 1 and R 6 The terminal group shown preferably does not contain a secondary hydroxyl group (i.e., the fluorine-containing ether compound represented by formula (1) does not contain a secondary hydroxyl group) in order to further improve chemical resistance. R 1 and R 6 Preferably, each of these is independently an organic group having a polar group, an organic group having a carbon-carbon unsaturated bond, or an organic group having both a polar group and a carbon-carbon unsaturated bond.

[0075] When the terminal group has a polar group, the polar group is a hydroxyl group (-OH) or an amino group (-NR). 7 R 8 ;R 7 and R 8Each of these is independently a hydrogen atom or an organic group. These include a carboxyl group (-COOH), a formyl group (-(C=O)H), a carbonyl group (-CO-), a sulfo group (-SO3H), a cyano group (-CN), and a group having an amide bond (-NR). 9 COR 10 or -CONR 11 R 12 ;R 9 , R 10 , R 11 and R 12 Each of these is independently a hydrogen atom or an organic group. Preferably, it is at least one selected from the group consisting of ). Note that "groups having an amide bond" include both groups that bond to an organic group at the carbon atom constituting the amide bond (e.g., carboxamide group (-C(=O)NH2)) and groups that bond to an organic group at the nitrogen atom constituting the amide bond (e.g., acetamide group (-NHC(=O)CH3)), as shown in the above formula. In groups having an amide bond, the R 9 and R 10 The R 11 and R 12 The R groups may bond to each other to form a ring. 9 , R 10 , R 11 and R 12 Preferably, each of these is independently selected from the group consisting of a hydrogen atom, a methyl group, an ethyl group, a propyl group, and a butyl group. Among these polar groups, it is more preferable that at least one polar group is selected from the group consisting of hydroxyl groups, cyano groups, and groups having an amide bond. This is because it results in a fluorine-containing ether compound that can form a lubricating layer with better chemical resistance and a higher pickup suppression effect. If the terminal group has a polar group, the number of polar groups is preferably 1 to 3, and more preferably 1 to 2. If the number of polar groups is 2 or more, some or all of the polar groups may be the same, or they may be different.

[0076] Organic groups having polar groups are preferably represented as -CH2-Y, -CH2CH2-Y, -CH2-O-CH2CH2-Y, -CH2-O-CH2CH2CH2-Y, -CH2-O-CH2CH(OH)CH2-O-CH2CH2-Y, or -CH2-O-CH2CH(OH)CH2-O-CH2CH2CH2-Y (where Y is a polar group in each of the above formulas).

[0077] When the terminal group has a carbon-carbon unsaturated bond, it is preferable that the terminal group is an organic group having at least one carbon-carbon unsaturated bond selected from the group consisting of an aromatic hydrocarbon group which may have substituents, an unsaturated heterocyclic group, an alkenyl group, and an alkynyl group. Specifically, examples of aromatic hydrocarbon groups that may have substituents include phenyl groups, methoxyphenyl groups, phenyl fluoride groups, naphthyl groups, and methoxynaphthyl groups. Examples of unsaturated heterocyclic groups include pyrrolyl, pyrazolyl, imidazolyl, furyl, furfuryl, oxazolyl, isoxazolyl, thienyl, thiazolyl, isothiazolyl, pyridyl, pyrimidinyl, pyridadinyl, pyrazinyl, indolinyl, benzofuranyl, benzothienyl, benzimidazolyl, benzoxazolyl, benzothiazolyl, benzopyrazolyl, benzoisoxazolyl, benzoisothiazolyl, quinolyl, isoquinolyl, quinazolinyl, quinoxalinyl, phthalazinyl, and synnolinyl groups.

[0078] Examples of alkenyl groups include allyl groups and butenyl groups. Examples of alkynyl groups include propargyl groups. When the terminal group has a carbon-carbon unsaturated bond, it is preferable that the terminal group is an organic group having one of the carbon-carbon unsaturated bonds selected from the group consisting of a phenyl group, a methoxyphenyl group, a naphthyl group, a thienyl group, and an allyl group. This is because it results in a fluorine-containing ether compound that can form a lubricating layer with better chemical resistance and a higher pickup suppression effect.

[0079] Organic groups having a carbon-carbon unsaturated bond are preferably represented as -CH2-OZ or -CH2CH2-OZ (wherein Z is one selected from the group consisting of an aromatic hydrocarbon group which may have substituents, an unsaturated heterocyclic group, an alkenyl group, and an alkynyl group). Organic groups having both a polar group and a carbon-carbon unsaturated bond are preferably represented as -CH2-O-CH2CH(OH)CH2-OZ or -CH2CH2-O-CH2CH(OH)CH2-OZ (wherein Z is one selected from the group consisting of an aromatic hydrocarbon group which may have substituents, an unsaturated heterocyclic group, an alkenyl group, and an alkynyl group).

[0080] In the fluorine-containing ether compound represented by formula (1), R 1 and R 6 Each of these is preferably an end group represented by one of the following formulas (5-1) to (5-8). Formulas (5-1) to (5-3) are all organic groups having only one primary hydroxyl group, which is a polar group. Formula (5-4) is an organic group having one primary hydroxyl group and one secondary hydroxyl group as polar groups. Formula (5-5) is an organic group having one secondary hydroxyl group as a polar group and one allyl group, which is a group having a carbon-carbon unsaturated bond. Formula (5-6) is an organic group having one secondary hydroxyl group as a polar group and one phenyl group, which is a group having a carbon-carbon unsaturated bond. Formula (5-7) is an organic group having one cyano group, which is a polar group. The following formulas (5-8) represent organic groups that have one polar group with an amide bond (-NHCOCH3).

[0081] [ka] (The dotted lines in equations (5-1) to (5-8) represent R 2 or R 5 (This shows the bonds that the atom possesses to the carbon atoms.)

[0082] R 1 and / or R6 When the terminal group indicated by has a polar group, the lubricating layer containing the fluorine-containing ether compound is preferable because it exhibits even better adhesion to the protective layer and can be made thinner. The reason for this is explained below. R 2 and R 5 In the side chain portion of R, the carbon atom to which the primary hydroxyl group located at the tip is bonded and the oxygen atom to which the carbon atom in the main chain portion is bonded are linked by a linking group containing a methylene group (-CH2-). Therefore, R 1 (or R 6 Even if ) contains a polar group, R 1 (or R 6 The polar group of ) and R 2 (or R 5 The distance from the primary hydroxyl group of ) becomes appropriate. As a result, R 2 (or R 5 The primary hydroxyl group of ) and R 1 (or R 6 The polar groups of ) are less likely to have their binding to the active site on the protective layer inhibited by other polar groups, and R 2 (or R 5 ) and the primary hydroxyl group and R 1 (or R 6 The polar groups of ) do not easily aggregate.

[0083] Therefore, R 2 (or R 5 The primary hydroxyl group of ) and R 1 (or R 6 The polar groups of ) can each be independently adsorbed to active sites on the protective layer. As a result, R 1 and / or R 6 A lubricating layer containing a fluorine-containing ether compound whose terminal group is a polar group, as indicated by the symbol, exhibits even greater adhesion to the protective layer, shows good chemical resistance even at a thin thickness, and has a high pickup suppression effect.

[0084] In the fluorine-containing ether compound represented by formula (1), R 1 and R 6The total number of polar groups contained in is preferably 1 or more, and more preferably 2 or more, in order to enhance adhesion with the protective layer and achieve thinning of the lubricating layer. In the fluorine-containing ether compound represented by formula (1), R 1 and R 6 The total number of polar groups contained in the material is preferably 4 or less, more preferably 3 or less, and most preferably 2 or less, in order to prevent the presence of too many polar groups that do not participate in bonding with the protective layer.

[0085] Also, R 1 and / or R 6 When the terminal group indicated by has a carbon-carbon unsaturated bond, the lubricating layer containing the fluorine-containing ether compound is preferable because it exhibits even better adhesion to the protective layer and can be made thinner. The reason for this is explained below. The numerous functional groups (active sites) on the protective layer include locally charged sites and sites where the charge distribution is more widespread. 2 , R 4 and R 5 The hydroxyl group contained within, and R 1 and / or R 6 The carbon-carbon unsaturated bonds in the terminal groups shown by adsorb to other sites on the protective layer. Specifically, in formula (1), R 2 , R 4 and R 5 The hydroxyl groups contained within exhibit adsorption capacity through hydrogen bonding, where hydrogen atoms interact with locally charged sites on the protective layer. On the other hand, R 1 and / or R 6 The carbon-carbon unsaturated bonds in the terminal groups shown have a non-localized charge, and therefore exhibit adsorption capacity by interacting with areas on the protective layer where the charge distribution is more spread out.

[0086] Therefore, R in equation (1) 2 , R 4 and R 5 The hydroxyl group contained within, and R 1 and / or R 6The carbon-carbon unsaturated bonds in the terminal groups indicated by can each independently interact with the functional groups (active sites) on the protective layer. As a result, R 1 and / or R 6 A lubricating layer containing a fluorine-containing ether compound whose terminal group has a carbon-carbon unsaturated bond exhibits even greater adhesion to the protective layer, good chemical resistance even at a thin thickness, and a high pickup suppression effect.

[0087] In the fluorine-containing ether compound represented by formula (1), R 1 and R 6 The type of terminal group indicated can be appropriately selected according to the performance requirements of the lubricant containing the fluorine-containing ether compound.

[0088] In the fluorine-containing ether compound represented by formula (1), R 1 and R 6 These can be the same or different. 1 and R 6 When these factors are the same, the coating state of the protective layer of the fluorine-containing ether compound becomes more uniform, and a lubricating layer with better adhesion can be formed.

[0089] In the fluorine-containing ether compound represented by formula (1), R in formula (1) 1 -R 2 -and R 6 -R 5 - Preferably, the two are the same. This is because it results in a fluorine-containing ether compound that can be easily and efficiently manufactured. In the fluorine-containing ether compound represented by formula (1), there are (x+1) R in formula (1). 3 All of them are the same, and x of R 4 They are all the same, R 1 -R 2 -and R 6 -R 5 -It is more preferable that they be the same. This is because it results in a fluorine-containing ether compound that can be manufactured more easily and efficiently.

[0090] The fluorine-containing ether compound represented by formula (1) is preferably one of the compounds represented by the following formulas (A) to (X) and (XX). When the compound represented by formula (1) is one of the compounds represented by the following formulas (A) to (X) or (XX), the raw materials are readily available, and a lubricating layer with good chemical resistance and high pickup suppression effect can be formed.

[0091] In the compounds represented by the following formulas (A) to (X) and (XX), Rf1, Rf2, and Rf3, which represent the PFPE chain, have the following structures. That is, in the compounds represented by the following formulas (A) to (K), (N) to (R), (T) to (W), and (XX), Rf1 is the PFPE chain represented by formula (4-1) above. In the compounds represented by the following formulas (L), (S), and (X), Rf2 is the PFPE chain represented by formula (4-2) above. In the compound represented by the following formula (M), Rf3 is the PFPE chain represented by formula (4-3) above. Note that h and i in Rf1, j in Rf2, and k in Rf3, which represent the PFPE chain in formulas (A) to (X) and (XX), are values ​​that indicate the average degree of polymerization and are therefore not necessarily integers.

[0092] [ka]

[0093] The compounds represented by the following formulas (A) to (X) and (XX) are all R 2 The linking group is represented by the above formula (2-1) or (2-2), and in both cases R 5 This is the linking group represented by the above formula (2-3) or (2-4). The compounds represented by the following formulas (A) to (M) all have x in formula (1) as 0, and R 4 It does not contain in its structure. Compounds represented by the following formulas (N)~(X), (XX) all have x in formula (1) as 1 or 2, and one or two R 4 The compound represented by the following formulas (N) to (X) and (XX) is R 4This is the linking group represented by the above formula (3-1) or (3-2).

[0094] The compounds represented by the following formulas (A) to (H) have x = 0 in formula (1). 1 and R 6 R is one of the terminal groups represented by the above formulas (5-1) to (5-8). 2 In all cases, the linking group is represented by the above formula (2-1) and n1 is 2. 5 In all cases, the linking group is represented by the above formula (2-3) and n2 is 2. 3 These are all PFPE chains represented by the above formula (4-1).

[0095] The compounds represented by the following formulas (I) and (J) have x = 0 in formula (1). The compounds represented by the following formulas (I) and (J) have R 1 and R 6 These are all terminal groups represented by the above formula (5-1), and R 3 This is the PFPE chain represented by the above formula (4-1). The compound represented by the following formula (I) is R 2 The linking group is represented by the above formula (2-1), and n1 is 3. 5 The linking group is represented by the above formula (2-3), where n2 is 3. The compound represented by the following formula (J) is R 2 The linking group is represented by the above formula (2-1), and n1 is 4. 5 The linking group is represented by the above formula (2-3), and n2 is 4.

[0096] The compound represented by the following formula (K) has x = 0 in formula (1). 1 and R 6 This is the terminal group represented by the above formula (5-1). 2 This is the linking group represented by the above formula (2-2). 5 This is the linking group represented by the above formula (2-4). 3 This is the PFPE chain represented by the above formula (4-1).

[0097] The compounds represented by the following formulas (L) and (M) have x = 0 in formula (1). The compounds represented by the following formulas (L) and (M) both have R 1 and R 6 This is the terminal group represented by the above formula (5-1). 2 In all cases, the linking group is represented by the above formula (2-1) and n1 is 2. 5 In all cases, these are linking groups represented by the above formula (2-3) where n2 is 2. The compound represented by the following formula (L) is R 3 This is the PFPE chain represented by the above formula (4-2). The compound represented by the following formula (M) is R 3 This is the PFPE chain represented by the above formula (4-3).

[0098] The compounds represented by the following formulas (N) to (P) all have x = 1 in formula (1). 2 The linking group is represented by the above formula (2-1), where n1 is 2. 5 The linking group is represented by the above formula (2-3), and n2 is 2. 4 The linking group is represented by the above formula (3-1), where n3 is 2, y1 is 1, and y2 is 1. The compounds represented by the following formulas (N) to (P) have two R 3 These are all PFPE chains represented by the above formula (4-1). The compound represented by the following formula (N) is R 1 and R 6 The terminal group is represented by the above formula (5-1). The compound represented by the following formula (O) is R 1 and R 6 The terminal group is represented by the above formula (5-3). The compound represented by the following formula (P) is R 1 and R 6 This is the terminal group represented by the above formula (5-7).

[0099] The compound represented by the following formula (Q) is one in which x in formula (1) is 1. 1 and R 6 This is the terminal group represented by the above formula (5-1). 2 The linking group is represented by the above formula (2-1), and n1 is 3. 5The linking group is represented by the above formula (2-3), and n2 is 3. 4 The linking group is represented by the above formula (3-1), where n3 is 3, y1 is 1, and y2 is 1. The two R 3 These are all PFPE chains represented by the above formula (4-1).

[0100] The compound represented by the following formula (R) is one in which x in formula (1) is 1. 1 and R 6 This is the terminal group represented by the above formula (5-1). 2 This is the linking group represented by the above formula (2-2). 5 This is the linking group represented by the above formula (2-4). 4 The linking group is represented by the above formula (3-2), where y3 is 1 and y4 is 1. Two R 3 These are all PFPE chains represented by the above formula (4-1).

[0101] The compound represented by the following formula (S) is one in which x in formula (1) is 1. 1 and R 6 This is the terminal group represented by the above formula (5-1). 2 The linking group is represented by the above formula (2-1), where n1 is 2. 5 The linking group is represented by the above formula (2-3), and n2 is 2. 4 The linking group is represented by the above formula (3-1), and there are two n3s, one y1, and one y2. 3 These are all PFPE chains represented by the above formula (4-2).

[0102] The compounds represented by the following formulas (T) to (V) all have x = 2 in formula (1). 2 The linking group is represented by the above formula (2-1), where n1 is 2. 5 The linking group is represented by the above formula (2-3), and n2 is 2. Two R 4 These are all linking groups represented by the above formula (3-1), where n3 is 2, y1 is 1, and y2 is 1. The three R 3 These are all PFPE chains represented by the above formula (4-1). The compound represented by the following formula (T) is R 1 and R 6 The terminal group is represented by the above formula (5-1). The compound represented by the following formula (U) is R 1 and R 6 The terminal group is represented by the above formula (5-3). The compound represented by the following formula (V) is R 1 and R 6 This is the terminal group represented by the above formula (5-7).

[0103] The compound represented by the following formula (W) is one in which x in formula (1) is 2. 1 and R 6 This is the terminal group represented by the above formula (5-1). 2 This is the linking group represented by the above formula (2-2). 5 This is the linking group represented by the above formula (2-4). Two R 4 These are all linking groups represented by the above formula (3-2), with y3 being 1 and y4 being 1. The three R 3 These are all PFPE chains represented by the above formula (4-1).

[0104] The compound represented by the following formula (X) is one in which x in formula (1) is 2. 1 and R 6 This is the terminal group represented by the above formula (5-1). 2 The linking group is represented by the above formula (2-1), where n1 is 2. 5 The linking group is represented by the above formula (2-3), and n2 is 2. Two R 4 These are all linking groups represented by the above formula (3-1), where n3 is 2, y1 is 1, and y2 is 1. The three R 3 These are all PFPE chains represented by the above formula (4-2). The compound represented by the following formula (XX) is one in which x in formula (1) is 1. 1 and R 6 This is the terminal group represented by the above formula (5-2). 2 The linking group is represented by the above formula (2-1), where n1 is 2. 5The linking group is represented by the above formula (2-3), and n2 is 2. 4 The linking group is represented by the above formula (3-1), where n3 is 2, y1 is 1, and y2 is 1. Two R 3 These are all PFPE chains represented by the above formula (4-1).

[0105] [ka] (In equation (A), in Rf1, h and i represent the average degree of polymerization, where h ranges from 1 to 20 and i ranges from 0 to 20.) (In equation (B), in Rf1, h and i represent the average degree of polymerization, where h ranges from 1 to 20 and i ranges from 0 to 20.) (In formula (C), in Rf1, h and i represent the average degree of polymerization, where h ranges from 1 to 20 and i ranges from 0 to 20.) (In equation (D), in Rf1, h and i represent the average degree of polymerization, where h ranges from 1 to 20 and i ranges from 0 to 20.) (In equation (E), in Rf1, h and i represent the average degree of polymerization, where h ranges from 1 to 20 and i ranges from 0 to 20.) (In equation (F), in Rf1, h and i represent the average degree of polymerization, where h ranges from 1 to 20 and i ranges from 0 to 20.)

[0106] [ka] (In equation (G), in Rf1, h and i represent the average degree of polymerization, where h ranges from 1 to 20 and i ranges from 0 to 20.) (In formula (H), in Rf1, h and i represent the average degree of polymerization, where h ranges from 1 to 20 and i ranges from 0 to 20.) (In equation (I), in Rf1, h and i represent the average degree of polymerization, where h ranges from 1 to 20 and i ranges from 0 to 20.) (In formula (J), in Rf1, h and i represent the average degree of polymerization, where h ranges from 1 to 20 and i ranges from 0 to 20.) (In formula (K), in Rf1, h and i represent the average degree of polymerization, where h ranges from 1 to 20 and i ranges from 0 to 20.) (In formula (L), in Rf2, j represents the average degree of polymerization and is expressed as 1 to 15.) (In formula (M), in Rf3, k represents the average degree of polymerization and is expressed as 1 to 10.)

[0107] [ka] (In the two Rf1 in equation (N), h and i represent the average degree of polymerization, where h is between 1 and 20, and i is between 0 and 20; the average degrees of polymerization in the two Rf1 may be the same or different.) (In the two Rf1 in equation (O), h and i represent the average degree of polymerization, where h is between 1 and 20, and i is between 0 and 20; the average degrees of polymerization in the two Rf1 may be the same or different.) (In the two Rf1 in equation (P), h and i represent the average degree of polymerization, where h is between 1 and 20 and i is between 0 and 20; the average degrees of polymerization in the two Rf1 may be the same or different.) (In equation (Q), h and i represent the average degree of polymerization, where h is between 1 and 20, and i is between 0 and 20; the average degrees of polymerization in the two Rf1s may be the same or different.) (In the two Rf1 in equation (R), h and i represent the average degree of polymerization, where h is between 1 and 20 and i is between 0 and 20; the average degrees of polymerization in the two Rf1 may be the same or different.) (In the two Rf2 terms in equation (S), j represents the average degree of polymerization and is between 1 and 15; the average degrees of polymerization in the two Rf2 terms may be the same or different.)

[0108] [ka] (In equation (T), in the three Rf1 terms, h and i represent the average degree of polymerization, where h is between 1 and 20, and i is between 0 and 20; the average degrees of polymerization in the three Rf1 terms may be different, or the average degrees of polymerization in two or three Rf1 terms may be the same.) (In equation (U), h and i represent the average degree of polymerization, where h is between 1 and 20, and i is between 0 and 20; the average degrees of polymerization in the three Rf1s may be different, or the average degrees of polymerization in two or three Rf1s may be the same.) (In equation (V), h and i represent the average degree of polymerization, where h is between 1 and 20, and i is between 0 and 20; the average degrees of polymerization in the three Rf1s may be different, or the average degrees of polymerization in two or three Rf1s may be the same.)

[0109] [ka] (In equation (W), h and i represent the average degree of polymerization, where h is between 1 and 20, and i is between 0 and 20; the average degrees of polymerization in the three Rf1s may be different, or the average degrees of polymerization in two or three Rf1s may be the same.) (In equation (X), in the three Rf2s, j represents the average degree of polymerization and is between 1 and 15; the average degrees of polymerization in the three Rf2s may be different, or the average degrees of polymerization in two or three Rf2s may be the same.) (In the two Rf1 in equation (XX), h and i represent the average degree of polymerization, where h is between 1 and 20, and i is between 0 and 20; the average degrees of polymerization in the two Rf1 may be the same or different.)

[0110] The fluorine-containing ether compound in this embodiment preferably has a number-average molecular weight (Mn) in the range of 500 to 10000, and particularly preferably in the range of 1000 to 5000. If the number-average molecular weight is 500 or more, the lubricating layer made of the lubricant containing the fluorine-containing ether compound in this embodiment will have excellent heat resistance. The number-average molecular weight of the fluorine-containing ether compound is more preferably 1000 or more. Furthermore, if the number-average molecular weight is 10000 or less, the viscosity of the fluorine-containing ether compound will be appropriate, and a thin lubricating layer can be easily formed by applying a lubricant containing it. The number-average molecular weight of the fluorine-containing ether compound is preferably 5000 or less, as this results in a viscosity that is easy to handle when applied to a lubricant.

[0111] The number-average molecular weight (Mn) of fluorine-containing ether compounds was determined using a Bruker BioSpin AVANCE III 400. 1 H-NMR and 19 These values ​​were measured by F-NMR. Specifically, 19 The number of repeating units in the PFPE chain is calculated from the integrated value measured by 1F-NMR, and the number-average molecular weight is determined. For NMR (nuclear magnetic resonance) measurements, the sample is diluted in hexafluorobenzene / d-acetone (4 / 1v / v) solvent before measurement. 19 The standard for the F-NMR chemical shift is the hexafluorobenzene peak at -164.7 ppm. 1 The standard for the 1H-NMR chemical shift is to set the acetone peak at 2.2 ppm.

[0112] In this embodiment, it is preferable to fractionate the fluorine-containing ether compound by an appropriate molecular weight method to achieve a molecular weight dispersion (weight-average molecular weight (Mw) / number-average molecular weight (Mn) ratio) of 1.3 or less. In this embodiment, 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 molecular weight fractionation by supercritical fluid extraction can be used.

[0113] "Manufacturing method" The method for producing the fluorine-containing ether compound of this embodiment is not particularly limited and can be produced using conventionally known production methods. The fluorine-containing ether compound of this embodiment can be produced, for example, using a production method having a first reaction step that forms a main chain portion which constitutes the chain-like structure of the fluorine-containing ether compound, and a second reaction step that forms side chain portions which branch off from the main chain portion, as shown below.

[0114] The first reaction step involves the R of the chain structure of the fluorine-containing ether compound in formula (1). 2 , R 5 (If x is 1 or 2, R 2 , R 4 , R 5 It is preferable that the step involves synthesizing a first intermediate compound, which is a compound having a structure in which a secondary hydroxyl group is arranged in each of the main chain portions. The second reaction step involves R in formula (1) of the first intermediate compound. 2 , R 5 (If x is 1 or 2, R 2 , R 4 , R 5 Preferably, the process involves chemically modifying the secondary hydroxyl groups located in the main chain portion to form a side chain portion having a primary hydroxyl group.

[0115] [First manufacturing method] When producing a fluorine-containing ether compound in formula (1) where x is 0, for example, the first production method shown below can be used. First, in equation (1), R 3 Prepare a fluorine-based compound in which hydroxymethyl groups (-CH2OH) are positioned at both ends of the corresponding perfluoropolyether chain.

[0116] (First reaction step) <R 1 and R 6 If they are the same > In equation (1), x is 0, and R 1 and R 6However, when producing the same fluorine-containing ether compound, in the first reaction step, the hydroxyl group of the hydroxymethyl group located at both ends of the above fluorine compound and the R in formula (1) 1 The corresponding base and R 2 A group (=R) bonded to the group corresponding to the main chain portion. 6 The corresponding base and R 5 The epoxy compound corresponding to the group that is bonded to the main chain portion of the molecule is reacted with the epoxy compound.

[0117] As a result of the above reaction, R 3 At both ends of the corresponding perfluoropolyether chain, R 1 The corresponding base and R 2 A group (=R) bonded to the group corresponding to the main chain portion. 6 The corresponding base and R 5 A first intermediate compound 1a is obtained which has a group (a group bonded to the main chain portion of R) in the first intermediate compound 1a. 2 The groups corresponding to the main chain portion and R 5 Each group corresponding to the main chain portion has a secondary hydroxyl group, which is formed in the first reaction step by the reaction of the hydroxyl group of the hydroxymethyl group with the epoxy group of the epoxy compound.

[0118] <R 1 and R 6 If they are different > In equation (1), x is 0, and R 1 and R 6 When producing a different compound, in the first reaction step, the hydroxyl group of the hydroxymethyl group located at one end of the above-mentioned fluorine-based compound and the R in formula (1) 1 The corresponding base and R 2 The epoxy compound corresponding to the group to which the main chain portion of is bonded is reacted. Then, the hydroxyl group of the hydroxymethyl group located at the other end of the above fluorine compound and R in formula (1) are reacted. 6 The corresponding base and R 5 The epoxy compound corresponding to the group that is bonded to the main chain portion of the molecule is reacted with the epoxy compound that corresponds to the bonded group.

[0119] In this case, the first reaction step involves the hydroxyl group of the hydroxymethyl group located at one end of the above-mentioned fluorine compound and R in formula (1). 6 The corresponding base and R 5 After reacting the epoxy compound corresponding to the group to which the group corresponding to the main chain portion of the above fluorine compound is bonded, the hydroxyl group of the hydroxymethyl group located at the other end of the above fluorine compound and the R in formula (1) 1 The corresponding base and R 2 This may involve a step of reacting a group corresponding to the main chain portion with an epoxy compound corresponding to the bonded group.

[0120] As a result of the above reaction, R 3 At one end of the corresponding perfluoropolyether chain, R 1 The corresponding base and R 2 It has a group bonded to the main chain portion, and at the other end, R 6 The corresponding base and R 5 A first intermediate compound 1b is obtained, which has a group bonded to the group corresponding to the main chain portion of R. 2 The groups corresponding to the main chain portion and R 5 Each group corresponding to the main chain portion has a secondary hydroxyl group, which is formed in the first reaction step by the reaction of the hydroxyl group of the hydroxymethyl group with the epoxy group of the epoxy compound.

[0121] In formula (1) used in the first reaction step, R 1 The corresponding base and R 2 A group bonded to the main chain portion (or R 6 The corresponding base and R 5 As an epoxy compound corresponding to the group bonded to the main chain portion, for example, compounds represented by the following formulas (7-1) to (7-8) can be used.

[0122] [ka] (In formulas (7-1) to (7-4), THP represents a tetrahydropyranyl group.) (In formulas (7-4) to (7-6), MOM represents a methoxymethyl group.)

[0123] The epoxy compound used in the first reaction step is, for example, the R of the fluorine-containing ether compound to be produced. 1 (or R 6 It can be synthesized by reacting an alcohol having the corresponding structure with epichlorohydrin or epibromohydrin. The epoxy compound used in the first reaction step may be synthesized by oxidizing a compound having a carbon-carbon double bond, or it may be purchased commercially and used.

[0124] (Second reaction step) <R 2 The side chain portion and R 5 If the side chain portion is the same as > In equation (1), x is 0, and R 2 The side chain portion and R 5 When producing a fluorine-containing ether compound having the same side chain portion as the first intermediate compound 1a or first intermediate compound 1b produced in the first reaction step, the R of formula (1) is added to the secondary hydroxyl group of the first intermediate compound 1a or first intermediate compound 1b produced in the first reaction step. 2 The side chain portion (=R 5 A second intermediate compound 2a is produced by reacting a halogen with a protected hydroxyl group corresponding to the side chain portion of the compound.

[0125] <R 2 The side chain portion and R 5 If the side chain portion is different > In equation (1), x is 0, and R 2 The side chain portion and R 5 When producing a fluorine-containing ether compound that differs from the side chain portion of the first intermediate compound 1a or the first intermediate compound 1b produced in the first reaction step, the R of formula (1) is used to support the secondary hydroxyl group of the first intermediate compound 1a or the first intermediate compound 1b produced in the first reaction step. 2 A halide having a protected hydroxyl group corresponding to the side chain portion of R 5The second intermediate compound 2b is produced by sequentially reacting a halide having a protected hydroxyl group corresponding to the side chain portion of with a known method. After the reaction, if necessary, the compound is purified by a known method such as column chromatography. 2 The side chain portion and R 5 A second intermediate compound 2b having the side chain portion is obtained. The order of reaction with the first intermediate compound 1a or the first intermediate compound 1b is R 2 A halide having a protected hydroxyl group corresponding to the side chain portion of R 5 Either the halogen with the protected hydroxyl group corresponding to the side chain portion of the compound or the halogen may come first.

[0126] In the second reaction step, R in formula (1) 2 The side chain portion (or R 5 As halides having a protected hydroxyl group corresponding to the side chain portion, for example, compounds represented by the following formulas (8-1) to (8-4) can be used.

[0127] [ka] (In formulas (8-1) to (8-4), THP represents a tetrahydropyranyl group.)

[0128] Next, a deprotection reaction is carried out to remove the protecting group derived from the halide having a protected hydroxyl group, which is present in the second intermediate compound 2a or the second intermediate compound 2b, by a known method according to the type of protecting group. As a result, R in formula (1) 2 The side chain portion and R 5 Each side chain portion has one primary hydroxyl group at its tip. By performing the above steps, a fluorine-containing ether compound in which x in equation (1) is 0 is obtained.

[0129] [Second manufacturing method] When producing a fluorine-containing ether compound in formula (1) where x is 1, for example, the second production method shown below can be used.

[0130] (First reaction step) <Two R's 3 If R is the same, 1 and R 6 If they are the same > In equation (1), x is 1, and the two R 3 The same, R 1 and R 6 When producing compounds that are the same, first, as in the first production method, R in formula (1) 3 Prepare a fluorine-based compound in which hydroxymethyl groups (-CH2OH) are positioned at both ends of the corresponding perfluoropolyether chain.

[0131] Next, of the hydroxymethyl groups located at both ends of the above fluorine-based compound, the hydroxyl group of one hydroxymethyl group and the R in formula (1) 1 The corresponding base and R 2 A group (=R) bonded to the group corresponding to the main chain portion. 6 The corresponding base and R 5 The epoxy compound is reacted with the group corresponding to the main chain portion of the compound (the group to which the group is bonded). After the reaction, the compound is purified by known methods such as column chromatography as needed to obtain a compound in which the epoxy compound is reacted with the hydroxymethyl group located at one of the hydroxymethyl groups located at both ends of the above fluorine compound.

[0132] As a result of the above reaction, R 3 At one end of the corresponding perfluoropolyether chain, R 1 The corresponding base and R 2 A group (=R) bonded to the group corresponding to the main chain portion. 6 The corresponding base and R 5 A precursor compound 11a is obtained having a group (a group bonded to the main chain portion of R) in the precursor compound 11a. 2 The base corresponding to the main chain portion (=R 5The group corresponding to the main chain portion has one secondary hydroxyl group formed by the reaction of the hydroxyl group of the hydroxymethyl group with the epoxy group of the epoxy compound.

[0133] Next, the hydroxyl group of the hydroxymethyl group located at one end of precursor compound 11a and R in formula (1) 4 The halogen compound having an epoxy group corresponding to the main chain portion is reacted with it. This reaction leads to R 4 At both ends of the structure corresponding to the main chain portion, R 3 It has a perfluoropolyether chain corresponding to R at both ends. 1 The corresponding base and R 2 A group (=R) bonded to the group corresponding to the main chain portion. 6 The corresponding base and R 5 A first intermediate compound 1c is obtained which has a group (a group bonded to the main chain portion of R) in the first intermediate compound 1c. 4 The group corresponding to the main chain portion has a single secondary hydroxyl group formed by the reaction of the hydroxyl group of the hydroxymethyl group with the epoxy group of the epoxy compound.

[0134] <Two R's 3 Different, and / or R 1 and R 6 If they are different > In equation (1), x is 1, and the two R 3 Different compounds, and / or R 1 and R 6 When producing a compound different from the one in formula (1), first, R 1 R on the side 3 A fluorine-based compound is prepared in which hydroxymethyl groups (-CH2OH) are positioned at both ends of the corresponding perfluoropolyether chain. Then, precursor compound 11b is prepared in the same manner as when preparing precursor compound 11a, except that this fluorine-based compound is used.

[0135] Precursor compound 11b is R 1 R on the side 3At one end of the corresponding perfluoropolyether chain, R 1 The corresponding base and R 2 It has a group to which the group corresponding to the main chain portion is bonded. In precursor compound 11b, R 2 The group corresponding to the main chain portion has a single secondary hydroxyl group formed by the reaction of the hydroxyl group of the hydroxymethyl group with the epoxy group of the epoxy compound.

[0136] Next, R in equation (1) 6 R on the side 3 Prepare a fluorine-based compound in which hydroxymethyl groups (-CH2OH) are positioned at both ends of the corresponding perfluoropolyether chain. Then, of the hydroxymethyl groups positioned at both ends of this fluorine-based compound, the hydroxyl group of one of the hydroxymethyl groups and R in formula (1) 6 The corresponding base and R 5 The epoxy compound corresponding to the group to which the main chain portion of the fluorine compound is bonded is reacted. After the reaction, if necessary, the compound is purified by known methods such as column chromatography to obtain a compound in which the hydroxymethyl group located at one end of the hydroxymethyl groups located at both ends of the above fluorine compound has reacted with the epoxy compound.

[0137] As a result of the above reaction, R 6 R on the side 3 At one end of the corresponding perfluoropolyether chain, R 6 The corresponding base and R 5 A precursor compound 11c is obtained which has a group bonded to the group corresponding to the main chain portion of R. 5 The group corresponding to the main chain portion has a single secondary hydroxyl group formed by the reaction of the hydroxyl group of the hydroxymethyl group with the epoxy group of the epoxy compound.

[0138] Next, the hydroxyl group of the hydroxymethyl group located at one end of precursor compound 11b and R in formula (1) 4The halogen compound having an epoxy group corresponding to the main chain portion is reacted with the reaction product. The resulting reaction product is then reacted with the hydroxyl group of the hydroxymethyl group located at one end of the precursor compound 11c. Note that R in formula (1) 4 Alternatively, a halogen compound having an epoxy group corresponding to the main chain portion may be reacted with precursor compound 11c, and then the resulting reaction product may be reacted with precursor compound 11b.

[0139] These reactions lead to R 4 R of the structure corresponding to the main chain portion 1 At the end of the side, R 1 R on the side 3 It has a perfluoropolyether chain corresponding to R at its end. 1 The corresponding base and R 2 It has a group bonded to the main chain portion, R 4 R of the structure corresponding to the main chain portion 6 At the end of the side, R 6 R on the side 3 It has a perfluoropolyether chain corresponding to R at its end. 6 The corresponding base and R 5 A first intermediate compound 1d is obtained which has a group bonded to the group corresponding to the main chain portion of R. 4 The group corresponding to the main chain portion has a single secondary hydroxyl group formed by the reaction of the hydroxyl group of the hydroxymethyl group with the epoxy group.

[0140] R used in the first reaction step of the second manufacturing method 4 Examples of halogen compounds having epoxy groups corresponding to the main chain portion of can be used, such as epibromohydrin, epichlorohydrin, 2-bromoethyloxirane, 3-bromopropyloxirane, 2-chloroethyloxirane, and 3-chloropropyloxirane, and in formula (1) R 4 If the expression is given by equation (3-1) and both y1 and y2 in equation (3-1) are 1, or R 4When the expression is represented by formula (3-2) and both y3 and y4 in formula (3-2) are 1, for example, epibromohydrin and epichlorohydrin can be used.

[0141] In the first reaction step of the second manufacturing method, R in formula (1) is used. 1 The corresponding base and R 2 A group bonded to the main chain portion (or R 6 The corresponding base and R 5 As the epoxy compound corresponding to the group to which the main chain portion is bonded, the same as that used in the first manufacturing method can be used.

[0142] (Second reaction step) <R 2 The side chain portion and R 4 The side chain portion and R 5 If the side chain portion is the same as > In equation (1), x is 1, and R 2 The side chain portion and R 4 The side chain portion and R 5 When producing a fluorine-containing ether compound having the same side chain portion as the first intermediate compound 1c or first intermediate compound 1d produced in the first reaction step, the R of formula (1) is added to the secondary hydroxyl group of the first intermediate compound 1c or first intermediate compound 1d produced in the first reaction step. 2 The side chain portion (=R 4 The side chain portion and R 5 A second intermediate compound 2c is produced by reacting a halogen with a protected hydroxyl group corresponding to the side chain portion of ( ).

[0143] <R 2 The side chain portion and R 4 The side chain portion and R 5 If some or all of the side chain portions are different > In equation (1), x is 1, and R 2 The side chain portion and R 4 The side chain portion and R 5When producing a fluorine-containing ether compound in which some or all of the side chain portions are different, in the second reaction step, the R of formula (1) is applied to the secondary hydroxyl group of the first intermediate compound 1c or first intermediate compound 1d produced in the first reaction step. 2 and R 4 and R 5 Halides having protected hydroxyl groups corresponding to each side chain portion are sequentially reacted using known methods to produce the second intermediate compound 2d. After the reaction, R is purified by known methods such as column chromatography as needed. 2 The side chain portion and R 4 The side chain portion and R 5 A second intermediate compound 2d having the side chain portion of R is obtained. 2 and R 4 and R 5 The order in which the halogens having protected hydroxyl groups corresponding to each side chain portion are reacted with the first intermediate compound 1c or the first intermediate compound 1d is not particularly limited.

[0144] In the second reaction step of the second manufacturing method, R in formula (1) is used. 2 and R 4 and R 5 As a halogen having a protected hydroxyl group corresponding to each side chain portion, for example, R in formula (1) can be used in the first production method. 2 and R 5 Similar halides having protected hydroxyl groups corresponding to each side chain portion can be used.

[0145] Next, a deprotection reaction is carried out to remove the protecting group derived from the halide having a protected hydroxyl group, which is present in the second intermediate compound 2c or the second intermediate compound 2d, by a known method according to the type of protecting group. As a result, R in formula (1) 2 The side chain portion, R 4 The side chain portion and R 5 Each side chain portion has one primary hydroxyl group at its tip. By performing the above steps, a fluorine-containing ether compound in which x in equation (1) is 1 is obtained.

[0146] [Third manufacturing method] When producing a fluorine-containing ether compound in formula (1) where x is 2, for example, the third production method shown below can be used.

[0147] (First reaction step) <3 R's 3 The two R's are the same. 4 If R is the same, 1 and R 6 If they are the same > In equation (1), x is 2, and there are three R 3 The two R's are the same. 4 If R is the same, 1 and R 6 When producing a compound that is the same, first, the precursor compound 11a is produced in the same manner as in the second production method.

[0148] Next, R in equation (1) 3 A fluorine-based compound is prepared in which a hydroxymethyl group (-CH2OH) is positioned at both ends of the perfluoropolyether chain corresponding to the given compound. Next, the hydroxyl groups of the hydroxymethyl groups positioned at both ends of the above fluorine-based compound and R in formula (1) are used. 4 The R in formula (1) is reacted with a halogen compound having an epoxy group corresponding to the main chain portion. 3 At both ends of the corresponding perfluoropolyether chain, R 4 A precursor compound 11d having an epoxy group corresponding to the main chain portion is obtained.

[0149] Subsequently, the hydroxyl group of the hydroxymethyl group located at one end of precursor compound 11a and the R group located at both ends of precursor compound 11d 4 The epoxy group corresponding to the main chain portion is reacted to produce the first intermediate compound 1e. In the first intermediate compound 1e, two R 4 Each group corresponding to the main chain portion has a secondary hydroxyl group formed by the reaction of the hydroxyl group of the hydroxymethyl group with the epoxy group.

[0150] <Two R's 4 The same, and the three R's 3 Some or all of them are different, and / or R 1 and R 6 If they are different > In equation (1), x is 2, and the two R 4 The same, and the three R's 3 Some or all of them are different, and / or R 1 and R 6 When producing compounds different from those described below, the following methods can be used.

[0151] In other words, as a fluorine-based compound, there are three R 3 R, which is located in the center of the main chain. 3 Precursor compound 11e is prepared in the same manner as precursor compound 11d, except that a fluorine-based compound is used in which hydroxymethyl groups are positioned at both ends of the corresponding perfluoropolyether chain. Precursor compound 11e has three R 3 R, which is located in the center of the main chain. 3 At both ends of the corresponding perfluoropolyether chain, R 4 It has epoxy groups corresponding to the main chain portion.

[0152] Furthermore, precursor compound 11b and precursor compound 11c are produced in the same manner as in the second production method. Then, the hydroxyl group of the hydroxymethyl group located at one end of precursor compound 11b and the R group located at one end of precursor compound 11e are used. 4 The epoxy group corresponding to the main chain portion is reacted with the reaction product. The resulting reaction product is reacted with the hydroxyl group of the hydroxymethyl group located at one end of precursor compound 11c to produce the first intermediate compound 1f. Alternatively, precursor compound 11e may be reacted with precursor compound 11c, and then the resulting reaction product may be reacted with precursor compound 11b. In the first intermediate compound 1f, two R 4 Each group corresponding to the main chain portion has a secondary hydroxyl group formed by the reaction of the hydroxyl group of the hydroxymethyl group with the epoxy group.

[0153] <Two R's 4 If they are different > In equation (1), x is 2, and there are three R 3 If R is the same, 1 and R 6 The two R's are the same. 4 When producing different compounds, R 3 At both ends of the corresponding perfluoropolyether chain, R 4 The first intermediate compound 1e is prepared by using the precursor compound 11f shown below, instead of the precursor compound 11d which has an epoxy group corresponding to the main chain portion. ru.

[0154] Also, x in equation (1) is 2, and there are three R 3 Some or all of them are different, and / or R 1 and R 6 The two R's are different. 4 When producing different compounds, there are three R's 3 R, which is located in the center of the main chain. 3 At both ends of the corresponding perfluoropolyether chain, R 4 The first intermediate compound 1f is prepared by using the precursor compound 11f shown below, instead of the precursor compound 11e which has an epoxy group corresponding to the main chain portion.

[0155] The precursor compound 11f can be produced by the following method: R 3 (3 R's) 3 If some or all of them are different, then the three R's 3 R, which is located in the center of the main chain. 3 Prepare a fluorine-based compound in which hydroxymethyl groups are located at both ends of the perfluoropolyether chain corresponding to ). The hydroxyl group of the hydroxymethyl group located at one end of the fluorine-based compound and R 1 R on the side 4A halogen compound having an epoxy group corresponding to the main chain portion is reacted with R. Then, the hydroxyl group of the hydroxymethyl group located at the other end of the above fluorine compound and R 6 R on the side 4 The halogen compound having an epoxy group corresponding to the main chain portion is reacted with it.

[0156] As a result, R 3 (3 R's) 3 If some or all of them are different, then the three R's 3 R, which is located in the center of the main chain. 3 ) At both ends of the perfluoropolyether chain corresponding to ), different R 4 A precursor compound 11f having an epoxy group corresponding to the main chain portion is obtained. The order of reaction with the fluorine-based compound is R 1 R on the side 4 A halogen compound having an epoxy group corresponding to the main chain portion, and R 6 R on the side 4 Either the halogen compound having an epoxy group corresponding to the main chain portion of the compound or the halogen compound can come first.

[0157] R used in the first reaction step of the third manufacturing method 1 R on the side 4 and R 6 R on the side 4 As a halogen compound having an epoxy group corresponding to the main chain portion, R is used in the first reaction step of the second manufacturing method. 4 Similar halogen compounds having epoxy groups corresponding to the main chain portion can be used.

[0158] The above R 1 R on the side 4 Examples of halogen compounds having epoxy groups corresponding to the main chain portion include R 1 R on the side 4 If the expression is given by equation (3-1), and y1 is 1 and y2 is 2 in equation (3-1), then R 1 R on the side 4When expressed by formula (3-2), and y3 is 1 and y4 is 2 in formula (3-2), then 2-chloroethyloxirane and 2-bromoethyloxirane can be used. Also, R 1 R on the side 4 If the expression is given by equation (3-1), and y1 in equation (3-1) is 1 and y2 is 3, or R 1 R on the side 4 If the expression is represented by formula (3-2), and y3 is 1 and y4 is 3 in formula (3-2), then 3-chloropropyl oxirane and 3-bromopropyl oxirane can be used.

[0159] The above R 6 R on the side 4 Examples of halogen compounds having epoxy groups corresponding to the main chain portion include R 6 R on the side 4 If the expression is given by equation (3-1), and y1 is 2 and y2 is 1 in equation (3-1), then R 6 R on the side 4 When expressed by formula (3-2), and y3 is 2 and y4 is 1 in formula (3-2), then 2-chloroethyloxirane and 2-bromoethyloxirane can be used. Also, R 6 R on the side 4 If the expression is given by equation (3-1), and y1 is 3 and y2 is 1 in equation (3-1), then R 6 R on the side 4 If the expression is represented by formula (3-2), and y3 is 3 and y4 is 1 in formula (3-2), then 3-chloropropyl oxirane and 3-bromopropyl oxirane can be used.

[0160] (Second reaction step) <R 2 The side chain portion and two R 4 The side chain portion and R 5 If the side chain portion is the same as > In equation (1), x is 2, and R 2 The side chain portion and two R 4 The side chain portion and R 5When producing a fluorine-containing ether compound having the same side chain portion as the first intermediate compound 1e or first intermediate compound 1f produced in the first reaction step, the R of formula (1) is added to the secondary hydroxyl group of the first intermediate compound 1e or first intermediate compound 1f produced in the first reaction step. 2 The side chain portion (= two R 4 The side chain portion and R 5 A second intermediate compound 2e is produced by reacting a halogen with a protected hydroxyl group corresponding to the side chain portion of ( ).

[0161] <R 2 The side chain portion and two R 4 The side chain portion and R 5 If some or all of the side chain portions are different > In equation (1), x is 2, and R 2 The side chain portion and two R 4 The side chain portion and R 5 When producing a fluorine-containing ether compound in which some or all of the side chain portions are different, in the second reaction step, the R of formula (1) is applied to the secondary hydroxyl group of the first intermediate compound 1e or the first intermediate compound 1f produced in the first reaction step. 2 and two R 4 and R 5 Halides having protected hydroxyl groups corresponding to each side chain portion are sequentially reacted using known methods to produce the second intermediate compound 2f. After the reaction, R is purified by known methods such as column chromatography as needed. 2 The side chain portion and two R 4 The side chain portion and R 5 A second intermediate compound 2f having the side chain portion of R is obtained. 2 and two R 4 and R 5 The order in which the halogens having protected hydroxyl groups corresponding to each side chain portion are reacted with the first intermediate compound 1e or the first intermediate compound 1f is not particularly limited.

[0162] In the second reaction step of the third manufacturing method, R in formula (1) is used. 2 and two R 4 and R5 As a halogen having a protected hydroxyl group corresponding to each side chain portion, for example, R in formula (1) can be used in the second manufacturing method. 2 and R 4 and R 5 Similar halides having protected hydroxyl groups corresponding to each side chain portion can be used.

[0163] Next, a deprotection reaction is carried out to remove the protecting group derived from the halide having a protected hydroxyl group, which is present in the second intermediate compound 2e or the second intermediate compound 2f, by a known method according to the type of protecting group. As a result, R in formula (1) 2 The side chain portion, two R 4 The side chain portion and R 5 Each side chain portion has one primary hydroxyl group at its tip. By performing the above steps, a fluorine-containing ether compound in equation (1) where x is 2 is obtained.

[0164] [Lubricant for magnetic recording media] The lubricant for magnetic recording media of this embodiment contains a fluorine-containing ether compound represented by the above formula (1). The lubricant of this embodiment can be mixed with known materials used as lubricants, as necessary, as long as the properties are not impaired by the inclusion of the fluorine-containing ether compound represented by formula (1) above.

[0165] Specific examples of known materials include, for example, FOMBLIN® ZDIAC, FOMBLIN ZDEAL, FOMBLIN AM-2001 (all manufactured by Solvay Solexis), and Moresco A20H (manufactured by Moresco). The known materials used in combination with the lubricant of this embodiment preferably have a number average molecular weight of 1,000 to 10,000.

[0166] If the lubricant of this embodiment contains other materials of the fluorine-containing ether compound represented by formula (1) above, it is preferable that the content of the fluorine-containing ether compound represented by formula (1) in the lubricant of this embodiment be 50% by mass or more, and more preferably 70% by mass or more.

[0167] The lubricant of this embodiment contains a fluorine-containing ether compound represented by the above formula (1), and therefore has good chemical resistance and can form a lubricating layer with a high pickup suppression effect.

[0168] [Magnetic recording medium] The magnetic recording medium of this embodiment has at least a magnetic layer, a protective layer, and a lubricating layer sequentially provided on a substrate. In the magnetic recording medium of this embodiment, one or more underlayers can be provided between the substrate and the magnetic layer, as needed. Furthermore, at least one of an adhesive layer and a soft magnetic layer can be provided between the underlayer and the substrate.

[0169] Figure 1 is a schematic cross-sectional view showing one embodiment of the magnetic recording medium of the present invention. The magnetic recording medium 10 of this embodiment has a structure in which an adhesion layer 12, a soft magnetic layer 13, a first 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.

[0170] "substrate" As the substrate 11, for example, a non-magnetic substrate can be used, which has a film made of NiP or NiP alloy formed on a base made of a metal or alloy material such as Al or an Al alloy. Furthermore, the substrate 11 may be a non-magnetic substrate made of a non-metallic material such as glass, ceramics, silicon, silicon carbide, carbon, or resin, or a non-magnetic substrate in which a film of NiP or NiP alloy is formed on a substrate made of one of these non-metallic materials.

[0171] "Adhesion layer" The adhesive layer 12 prevents the progression 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 placed in contact with each other. The material of the adhesion layer 12 can be appropriately selected from, for example, Cr, Cr alloy, Ti, Ti alloy, CrTi, NiAl, AlRu alloy, etc. The adhesion layer 12 can be formed, for example, by sputtering.

[0172] "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 sequentially laminated. That is, the soft magnetic layer 13 preferably has a structure in which the soft magnetic films above and below the intermediate layer are anti-ferro-coupling (AFC) coupled by sandwiching an intermediate layer made of a Ru film between the two soft magnetic films.

[0173] Examples of materials for the first and second soft magnetic films include CoZrTa alloy and 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 becomes possible to improve the orientation of the first underlayer (seed layer) and reduce the amount of levitation of the magnetic head. The soft magnetic layer 13 can be formed, for example, by a sputtering method.

[0174] "First base layer" The first sublayer 14 is a layer that controls the orientation and crystal size of the second sublayer 15 and the magnetic layer 16 which are placed on top of it. Examples of the first subsoil layer 14 include a Cr layer, a Ta layer, a Ru layer, or a CrMo alloy layer, a CoW alloy layer, a CrW alloy layer, a CrV alloy layer, a CrTi alloy layer, and so on. The first subsoil layer 14 can be formed, for example, by a sputtering method.

[0175] "Second base layer" The second underlayer 15 is a layer that controls the orientation of the magnetic layer 16 to a good degree. The second underlayer 15 is preferably a layer made of Ru or a Ru alloy. The second sublayer 15 may consist of one layer or multiple layers. If the second sublayer 15 consists of multiple layers, all layers may be made of the same material, or at least one layer may be made of a different material. The second subsoil layer 15 can be formed, for example, by sputtering.

[0176] "Magnetic layer" The magnetic layer 16 consists of a magnetic film whose easy magnetization axis is oriented perpendicular or horizontal to the substrate surface. The magnetic layer 16 is a layer containing Co and Pt. The magnetic layer 16 may also contain oxides, Cr, B, Cu, Ta, Zr, etc., to improve the SNR characteristics. Examples of oxides contained in the magnetic layer 16 include SiO2, SiO, Cr2O3, CoO, Ta2O3, and TiO2.

[0177] The magnetic layer 16 may consist of a single layer, or it may consist of multiple magnetic layers made of materials with different compositions. For example, if the magnetic layer 16 consists of three layers stacked from bottom to top—a first magnetic layer, a second magnetic layer, and a third magnetic layer—the first magnetic layer is preferably a granular structure made of a material containing Co, Cr, Pt, and an oxide. As the oxide contained in the first magnetic layer, it is preferable to use oxides such as Cr, Si, Ta, Al, Ti, Mg, and Co. Among these, TiO2, Cr2O3, and SiO2 are particularly suitable. Furthermore, the first magnetic layer is preferably made of a composite oxide with two or more oxides added. Among these, Cr2O3-SiO2, Cr2O3-TiO2, and SiO2-TiO2 are particularly suitable.

[0178] The first magnetic layer may contain one or more elements selected from B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb, Ru, and Re, in addition to Co, Cr, Pt, and oxides. The second magnetic layer may use the same material as the first magnetic layer. The second magnetic layer preferably has a granular structure.

[0179] The third magnetic layer is preferably a non-granular structure made of a material containing Co, Cr, and Pt, but free of oxides. In addition to Co, Cr, and Pt, the third magnetic layer may contain one or more elements selected from B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb, Ru, Re, and Mn.

[0180] When the magnetic layer 16 is formed of multiple magnetic layers, it is preferable to provide a non-magnetic layer between adjacent magnetic layers. When the magnetic layer 16 consists of three layers, 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.

[0181] The non-magnetic layer provided between adjacent magnetic layers of the magnetic layer 16 can preferably be made of, for example, Ru, Ru alloy, CoCr alloy, CoCrX1 alloy (where 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, B).

[0182] For the non-magnetic layer provided between adjacent magnetic layers of the magnetic layer 16, it is preferable to use an alloy material containing an oxide, metal nitride, or metal carbide. Specifically, as oxides, for example, SiO2, Al2O3, Ta2O5, Cr2O3, MgO, Y2O3, TiO2, etc. can be used. As metal nitrides, for example, AlN, Si3N4, TaN, CrN, etc. can be used. As metal carbides, for example, TaC, BC, SiC, etc. can be used. The non-magnetic layer can be formed, for example, by sputtering.

[0183] To achieve a higher recording density, the magnetic layer 16 is preferably a perpendicular magnetic recording layer in which the easy magnetization axis is oriented perpendicular to the substrate surface. The magnetic layer 16 may also be an in-plane magnetic recording layer. The magnetic layer 16 may be formed by any conventionally known method, such as vapor deposition, ion beam sputtering, or magnetron sputtering. The magnetic layer 16 is usually formed by sputtering.

[0184] "Protective layer" The protective layer 17 protects the magnetic layer 16. The protective layer 17 may consist 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. A carbon-based protective layer is preferable because it further enhances the interaction with polar groups (especially hydroxyl groups) contained in the fluorine-containing ether compound in the lubricating layer 18.

[0185] The adhesion between the carbon-based protective layer and the lubricating layer 18 can be controlled by using hydrogenated carbon and / or nitrated 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 to 20 atoms when measured by hydrogen forward scattering (HFS). Furthermore, the nitrogen content in the carbon-based protective layer is preferably 4 to 15 atoms when measured by X-ray photoelectron spectroscopy (XPS).

[0186] The hydrogen and / or nitrogen contained in the carbon-based protective layer do not need to be uniformly distributed throughout the entire layer. Preferably, the carbon-based protective layer is a compositionally graded layer, for example, in which nitrogen is contained on the lubrication layer 18 side of the protective layer 17 and hydrogen is contained on the magnetic layer 16 side of the protective layer 17. In this case, the adhesion between the magnetic layer 16 and the lubrication layer 18 and the carbon-based protective layer is further improved.

[0187] The thickness of the protective layer 17 is preferably 1 nm to 7 nm. If the thickness of the protective layer 17 is 1 nm or more, sufficient performance as a protective layer 17 can be obtained. If the thickness of the protective layer 17 is 7 nm or less, it is preferable from the viewpoint of thinning the protective layer 17.

[0188] As a method for forming the protective layer 17, sputtering using a carbon-containing target material, CVD (chemical vapor deposition) using hydrocarbon raw materials such as ethylene and toluene, and IBD (ion beam deposition) can be used. When forming a carbon-based protective layer as the protective layer 17, it can be deposited by, for example, DC magnetron sputtering. In particular, when forming a carbon-based protective layer as the protective layer 17, it is preferable to deposit an amorphous carbon protective layer by plasma CVD. The amorphous carbon protective layer deposited by plasma CVD has a uniform surface and low roughness.

[0189] "Lubricant layer" The lubricating layer 18 prevents contamination of the magnetic recording medium 10. Furthermore, the lubricating layer 18 reduces the frictional force of the magnetic head of the magnetic recording / reproducing device sliding on the magnetic recording medium 10, thereby improving the durability of the magnetic recording medium 10. As shown in Figure 1, the lubricating layer 18 is formed in contact with the protective layer 17. The lubricating layer 18 is formed by applying the lubricant for magnetic recording media of the above-described embodiment onto the protective layer 17. Therefore, the lubricating layer 18 contains the above-described fluorine-containing ether compound.

[0190] The lubricating layer 18 is bonded with a particularly strong bond to the protective layer 17, especially when the protective layer 17 located beneath the lubricating layer 18 is a carbon-based protective layer. As a result, even with a thin lubricating layer 18, it becomes easier to obtain a magnetic recording medium 10 in which the surface of the protective layer 17 is covered with a high degree of coverage, and contamination of the surface of the magnetic recording medium 10 can be effectively prevented.

[0191] The average thickness of the lubricating layer 18 is preferably 0.5 nm (5 Å) to 2.0 nm (20 Å), and more preferably 0.5 nm (5 Å) to 1.2 nm (12 Å). When the average thickness of the lubricating layer 18 is 0.5 nm or more, the lubricating layer 18 is formed with a uniform thickness without forming islands or a mesh-like structure. Therefore, the surface of the protective layer 17 can be covered by the lubricating layer 18 with a high coverage rate. Furthermore, by making the average thickness of the lubricating layer 18 2.0 nm or less, the lubricating layer 18 can be sufficiently thinned, and the amount of levitation of the magnetic head can be sufficiently reduced.

[0192] "Method for forming a lubricating layer" To form the lubricating layer 18, for example, one method is to prepare a magnetic recording medium in the process of being manufactured, in which each layer up to the protective layer 17 has been formed on the substrate 11, and then apply a lubricating layer forming solution onto the protective layer 17.

[0193] The lubricating layer-forming solution is obtained by dispersing and dissolving the lubricant for magnetic recording media of the above embodiment in a solvent as needed, and adjusting the viscosity and concentration to be suitable for the coating method. Examples of solvents used in lubrication layer-forming solutions include fluorine-based solvents such as Bartrell® XF (trade name, manufactured by Mitsui DuPont Fluorochemicals).

[0194] The method for applying the lubricating layer-forming solution is not particularly limited, but examples include the spin coating method, spray method, paper coating method, and dip method. When using the dip method, for example, the 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 lubricating layer forming solution placed in the immersion tank of the dip coating apparatus. Next, the substrate 11 is withdrawn from the immersion tank at a predetermined speed. This coats the surface of the protective layer 17 of the substrate 11 with the lubricating layer forming solution. By using the dipping method, the lubrication layer-forming solution can be uniformly applied to the surface of the protective layer 17, and a lubrication layer 18 can be formed on the protective layer 17 with a uniform film thickness.

[0195] In this embodiment, it is preferable to heat-treat the substrate 11 on which the lubricating layer 18 is formed. By heat-treating, the adhesion between the lubricating layer 18 and the protective layer 17 is improved, and the adhesion force between the lubricating layer 18 and the protective layer 17 is improved. The heat treatment temperature is preferably 100°C to 180°C, and more preferably 100°C to 160°C. A heat treatment temperature of 100°C or higher provides sufficient improvement in adhesion between the lubricating layer 18 and the protective layer 17. Furthermore, a heat treatment temperature of 180°C or lower prevents thermal decomposition of the lubricating layer 18 due to heat treatment. The heat treatment time can be appropriately adjusted according to the heat treatment temperature, and is preferably 10 to 120 minutes.

[0196] In this embodiment, in order to further improve the adhesion of the lubricating layer 18 to the protective layer 17, the lubricating layer 18 may be irradiated with ultraviolet (UV) light before or after heat treatment.

[0197] The magnetic recording medium 10 of this embodiment has at least a magnetic layer 16, a protective layer 17, and a lubricating layer 18 sequentially provided on a substrate 11. In the magnetic recording medium 10 of this embodiment, the lubricating layer 18 containing the above-mentioned fluorine-containing ether compound is formed in contact with the protective layer 17. This lubricating layer 18 has good chemical resistance and a high pickup suppression effect. Therefore, the magnetic recording medium 10 of this embodiment is excellent in reliability, in particular in suppressing silicon contamination and durability. As a result, the magnetic recording medium 10 of this embodiment can achieve a low magnetic head levitation amount (for example, 10 nm or less) and operates stably over a long period of time even in harsh environments associated with the diversification of applications. Therefore, the magnetic recording medium 10 of this embodiment is particularly suitable as a magnetic disk mounted in a LUL (Load Unload) type magnetic disk drive. [Examples]

[0198] The present invention will be described in more detail below with reference to examples and comparative examples. However, the present invention is not limited to the following examples.

[0199] [Example 1] The compound represented by formula (A) above was obtained by the method described below. (First reaction step) HOCH2CF2O(CF2CF2O) in a 100 mL round-bottom flask under a nitrogen gas atmosphere. h (CF2O) i 10 g of the compound 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) (number average molecular weight 1000, molecular weight distribution 1.1), 4.75 g of the compound represented by the above formula (7-1), and 20 mL of t-butanol were charged together and stirred at room temperature until homogeneous to form a mixture. 0.90 g of potassium tert-butoxide was added to this mixture and the mixture was reacted by stirring at 70°C for 16 hours.

[0200] The compound represented by formula (7-1) was synthesized by protecting the hydroxyl group of 3-buten-1-ol with dihydropyran and then oxidizing it with m-chloroperbenzoic acid.

[0201] The reaction product obtained after the reaction was cooled to 25°C, transferred to a separatory funnel containing 100 mL of water, and extracted three times with 100 mL of ethyl acetate. The organic layer was washed with water and dehydrated with anhydrous sodium sulfate. After filtering off the drying agent, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 11.31 g of the compound shown in formula (9) below as the first intermediate compound.

[0202] [ka] (In formula (9), Rf1 is the PFPE chain represented by formula (4-1) above; in Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which also indicates the average degree of polymerization, represents 4.5; THP represents a tetrahydropyranyl group.)

[0203] (Second reaction step) Next, under a nitrogen gas atmosphere, 11.31 g of the compound represented by formula (9), which is the first intermediate compound obtained above, 4.09 g of the compound (2-(2-bromoethoxy)tetrahydro-2H-pyran) represented by formula (8-1), and 20 mL of dimethylformamide were charged into a 100 mL round-bottom flask and stirred at room temperature until homogeneous. 0.78 g of sodium hydride was added to this homogeneous solution and the mixture was stirred at 40°C for 16 hours to allow the reaction to proceed.

[0204] The reaction mixture obtained after the reaction was allowed to return to room temperature, and 5 g of 10% hydrogen chloride-methanol solution (hydrogen chloride-methanol reagent (5-10%) manufactured by Tokyo Chemical Industry Co., Ltd.) was added and the mixture was stirred at room temperature for 4 hours. Then, the reaction mixture was gradually transferred to a separatory funnel containing 100 mL of saturated sodium bicarbonate solution and extracted twice with 200 mL of ethyl acetate. The organic layer was washed in the following order: 100 mL of saline solution, 100 mL of saturated sodium bicarbonate solution, and 100 mL of saline solution, and dehydrated with anhydrous sodium sulfate. After filtering off the drying agent, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 4.15 g of compound (A) (in formula (A), Rf1 is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, represents 4.5).

[0205] The obtained compound (A) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.60-1.80(4H), 3.40-3.85(22H), 3.85-4.10(4H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(9F), -78.5(2F), -80.5(2F), -91.0~-88.5(18F)

[0206] [Example 2] The compound represented by formula (B) above was obtained by the method shown below. The same procedure as in Example 1 was followed, except that the compound represented by formula (7-2) was used instead of the compound represented by formula (7-1), to obtain 4.02 g of compound (B) (wherein Rf1 in formula (B) is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, also represents 4.5). The compound represented by formula (7-2) was synthesized by protecting the hydroxyl group of allyl alcohol with dihydropyran and then oxidizing it with m-chloroperbenzoic acid.

[0207] The obtained compound (B) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=3.40-3.85(22H), 3.85-4.10(4H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(9F), -78.5(2F), -80.5(2F), -91.0~-88.5(18F)

[0208] [Example 3] The compound represented by formula (C) above was obtained by the method shown below. The same procedure as in Example 1 was followed, except that the compound represented by formula (7-3) was used instead of the compound represented by formula (7-1), and 4.81 g of compound (C) (wherein Rf1 in formula (C) is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, also represents 4.5) was obtained. The compound represented by formula (7-3) was synthesized by protecting the hydroxyl group of ethylene glycol monoallyl ether with dihydropyran and then oxidizing it with m-chloroperbenzoic acid.

[0209] The obtained compound (C) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=3.40-3.85(34H), 3.85-4.10(4H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(9F), -78.5(2F), -80.5(2F), -91.0~-88.5(18F)

[0210] [Example 4] The compound represented by formula (D) above was obtained by the method shown below. The same procedure as in Example 1 was followed, except that the compound represented by formula (7-4) was used instead of the compound represented by formula (7-1), and 5.21 g of compound (D) (wherein Rf1 in formula (D) is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, also represents 4.5) was obtained. The compound represented by formula (7-4) was synthesized by the following method: One hydroxyl group of ethylene glycol was protected with dihydropyran, and then reacted with allyl glycidyl ether. The resulting secondary hydroxyl group was protected with methoxymethyl chloride and then oxidized with m-chloroperbenzoic acid to synthesize the compound.

[0211] The obtained compound (D) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=3.40-3.85(34H), 3.85-4.10(4H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(9F), -78.5(2F), -80.5(2F), -91.0~-88.5(18F)

[0212] [Example 5] The compound represented by formula (E) above was obtained by the method described below. The same procedure as in Example 1 was followed, except that the compound represented by formula (7-5) was used instead of the compound represented by formula (7-1), and 5.41 g of compound (E) (wherein Rf1 in formula (E) is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, also represents 4.5) was obtained. The compound represented by formula (7-5) was synthesized by the following method: Epichlorohydrin was reacted with two molar amounts of allyl alcohol. The secondary hydroxyl group formed after the reaction was protected with methoxymethyl chloride, and then one of the carbon-carbon double bonds was oxidized with m-chloroperbenzoic acid to synthesize the compound.

[0213] The obtained compound (E) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=3.40-3.85(36H), 3.85-4.10(4H), 5.2-6.1(6H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(9F), -78.5(2F), -80.5(2F), -91.0~-88.5(18F)

[0214] [Example 6] The compound represented by formula (F) above was obtained by the method described below. The same procedure as in Example 1 was followed, except that the compound represented by formula (7-6) was used instead of the compound represented by formula (7-1), to obtain 5.82 g of compound (F) (wherein Rf1 in formula (F) is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, also represents 4.5). The compound represented by formula (7-6) was synthesized by the following method: Phenol was reacted with allyl glycidyl ether. The secondary hydroxyl group produced after the reaction was protected with methoxymethyl chloride and oxidized with m-chloroperbenzoic acid to synthesize the compound.

[0215] The obtained compound (F) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=3.40-3.85(32H), 3.85-4.10(4H), 6.8-7.6ppm(10H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(9F), -78.5(2F), -80.5(2F), -91.0~-88.5(18F)

[0216] [Example 7] The compound represented by formula (G) above was obtained by the method shown below. The same procedure as in Example 1 was followed, except that the compound represented by formula (7-7) was used instead of the compound represented by formula (7-1), and 4.61 g of compound (G) (wherein Rf1 in formula (G) is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, also represents 4.5) was obtained. The compound represented by formula (7-7) was synthesized by reacting 3-cyanopropanol with epibromohydrin.

[0217] The obtained compound (G) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.60-1.80(4H), 2.00-2.10(4H), 3.40-3.85(24H), 3.85-4.10(4H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(9F), -78.5(2F), -80.5(2F), -91.0~-88.5(18F)

[0218] [Example 8] The compound represented by the above formula (H) was obtained by the method shown below. The same procedure as in Example 1 was followed, except that the compound represented by formula (7-8) was used instead of the compound represented by formula (7-1), and 4.33 g of compound (H) (wherein Rf1 in formula (H) is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, also represents 4.5) was obtained. The compound represented by formula (7-8) was synthesized by reacting acetaminoethanol with epibromohydrin.

[0219] The obtained compound (H) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.90-2.00(6H), 3.40-3.85(24H), 3.85-4.10(4H), 6.30-6.40(2H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(9F), -78.5(2F), -80.5(2F), -91.0~-88.5(18F)

[0220] [Example 9] The compound represented by formula (I) above was obtained by the method described below. The same procedure as in Example 1 was followed, except that the compound represented by formula (8-2) was used instead of the compound represented by formula (8-1), to obtain 4.18 g of compound (I) (wherein Rf1 in formula (I) is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, also represents 4.5). The compound represented by formula (8-2) was synthesized by protecting the hydroxyl group of 3-bromopropanol with dihydropyran.

[0221] The obtained compound (I) 1 H-NMR and 19The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.60-1.80(8H), 3.45-3.85(22H), 3.85-4.10(4H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(9F), -78.5(2F), -80.5(2F), -91.0~-88.5(18F)

[0222] [Example 10] The compound represented by formula (J) above was obtained by the method described below. The same procedure as in Example 1 was followed, except that the compound represented by formula (8-3) was used instead of the compound represented by formula (8-1), and 4.36 g of compound (J) (wherein Rf1 in formula (J) is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, also represents 4.5) was obtained. The compound represented by formula (8-3) was synthesized by protecting the hydroxyl group of 4-bromobutanol with dihydropyran.

[0223] The obtained compound (J) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.60-1.80(12H), 3.45-3.85(22H), 3.85-4.10(4H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(9F), -78.5(2F), -80.5(2F), -91.0~-88.5(18F)

[0224] [Example 11] The compound represented by the above formula (K) was obtained by the method described below. The same procedure as in Example 1 was followed, except that the compound represented by formula (8-4) was used instead of the compound represented by formula (8-1), and 4.54 g of compound (K) (wherein Rf1 in formula (K) is the PFPE chain represented by formula (4-1) above. In Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, also represents 4.5) was obtained. The compound represented by formula (8-4) was synthesized by brominating one hydroxyl group of diethylene glycol with phosphorus tribromide, and then protecting the other hydroxyl group with dihydropyran.

[0225] The obtained compound (K) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.60-1.80(4H), 3.45-3.85(30H), 3.85-4.10(4H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(9F), -78.5(2F), -80.5(2F), -91.0~-88.5(18F)

[0226] [Example 12] The compound represented by the above formula (L) was obtained by the method shown below. HOCH2CF2O(CF2CF2O) h (CF2O) i Instead of the compound represented by CF2CH2OH, use HOCH2CF2CF2O(CF2CF2CF2O). j Except for using a compound represented by CF2CF2CH2OH (where j, representing the average degree of polymerization, is 4.5), the same procedure as in Example 1 was followed to obtain 4.26 g of compound (L) (where Rf2 in formula (L) is the PFPE chain represented by formula (4-2) above. In Rf2, j, representing the average degree of polymerization, represents 4.5).

[0227] The obtained compound (L) 1 H-NMR and19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.60-1.80(4H), 3.45-3.85(30H), 3.85-4.10(4H) 19 F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(18F), -86.4(4F), -124.3(4F), -130.0~-129.0(9F)

[0228] [Example 13] The compound represented by the above formula (M) was obtained by the method described below. HOCH2CF2O(CF2CF2O) h (CF2O) i Instead of the compound represented by CF2CH2OH, use HOCH2CF2CF2CF2O(CF2CF2CF2CF2O) k Except for using a compound represented by CF2CF2CF2CH2OH (where k, representing the average degree of polymerization in the formula, is 3.0), the same procedure as in Example 1 was carried out to obtain 4.10 g of compound (M) (where Rf3 in formula (M) is the PFPE chain represented by the above formula (4-3). In Rf3, k, representing the average degree of polymerization, represents 3.0).

[0229] The obtained compound (M) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.60-1.80(4H), 3.45-3.85(30H), 3.85-4.10(4H) 19 F-NMR (acetone-D6): δ[ppm]=-84.0~-83.0(16F), -122.5(4F), -126.0(12F), -129.0~-128.0(4F)

[0230] [Example 14] The compound represented by the above formula (N) was obtained by the method described below. (First reaction step) HOCH2CF2O(CF2CF2O) in a 100 mL round-bottom flask under a nitrogen gas atmosphere. h (CF2O) i 20 g of the compound 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) (number average molecular weight 1000, molecular weight distribution 1.1), 2.06 g of the compound represented by the above formula (7-1), and 20 mL of t-butanol were charged together and stirred at room temperature until homogeneous to form a mixture. 0.90 g of potassium tert-butoxide was added to this mixture and the mixture was reacted by stirring at 70°C for 16 hours.

[0231] The reaction product obtained after the reaction was cooled to 25°C, transferred to a separatory funnel containing 100 mL of water, and extracted three times with 100 mL of ethyl acetate. The organic layer was washed with water and dehydrated with anhydrous sodium sulfate. After filtering off the drying agent, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 8.41 g of the compound shown in formula (10) below as the precursor compound.

[0232] [ka] (In formula (10), Rf1 is the PFPE chain represented by formula (4-1) above; in Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which also indicates the average degree of polymerization, represents 4.5; THP represents a tetrahydropyranyl group.)

[0233] Under a nitrogen gas atmosphere, 8.41 g of the precursor compound shown in formula (10), obtained above, 0.88 g of epibromohydrin, and 10 mL of t-butanol were charged into a 100 mL round-bottom flask and stirred at room temperature until homogeneous. 0.96 g of potassium tert-butoxide was added to this homogeneous solution and the mixture was reacted by stirring at 70°C for 23 hours. The reaction solution obtained after the reaction was allowed to return to room temperature, transferred to a separatory funnel containing 100 mL of water, and extracted three times with 100 mL of ethyl acetate. The organic layer was washed with water and dehydrated with anhydrous sodium sulfate. After filtering off the drying agent, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 5.61 g of the compound shown in formula (11) below as the first intermediate compound.

[0234] [ka] (In formula (11), Rf1 is the PFPE chain represented by formula (4-1) above; in the two Rf1s, h, which indicates the average degree of polymerization, represents 4.5, and i, which also indicates the average degree of polymerization, represents 4.5; THP represents a tetrahydropyranyl group.)

[0235] (Second reaction step) Under a nitrogen gas atmosphere, 5.61 g of the compound represented by formula (11), which is the first intermediate compound obtained above, 4.18 g of the compound represented by formula (8-1), and 20 mL of dimethylformamide were charged into a 100 mL round-bottom flask and stirred at room temperature until homogeneous. 0.85 g of sodium hydride was added to this homogeneous solution and the mixture was stirred at 40°C for 16 hours to allow the reaction to proceed.

[0236] The reaction mixture obtained after the reaction was allowed to return to room temperature, and 5 g of 10% hydrogen chloride-methanol solution (hydrogen chloride-methanol reagent (5-10%) manufactured by Tokyo Chemical Industry Co., Ltd.) was added and the mixture was stirred at room temperature for 4 hours. Then, the reaction mixture was gradually transferred to a separatory funnel containing 100 mL of saturated sodium bicarbonate solution and extracted twice with 200 mL of ethyl acetate. The organic layer was washed in the following order: 100 mL of saline solution, 100 mL of saturated sodium bicarbonate solution, and 100 mL of saline solution, and dehydrated with anhydrous sodium sulfate. After filtering off the drying agent, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 2.45 g of compound (N) (Rf1 in formula (N) is the PFPE chain represented by formula (4-1) above. In the two Rf1s, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, represents 4.5).

[0237] The obtained compound (N) 1H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.60-1.80(4H), 3.40-3.85(32H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0238] [Example 15] The compound represented by formula (O) above was obtained by the method shown below. The same procedure as in Example 14 was followed, except that the compound represented by formula (7-3) was used instead of the compound represented by formula (7-1), and 2.68 g of compound (O) (wherein Rf1 in formula (O) is the PFPE chain represented by formula (4-1) above. In the two Rf1s, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, also represents 4.5) was obtained.

[0239] The obtained compound (O) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=3.40-3.85(44H), 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)

[0240] [Example 16] The compound represented by formula (P) above was obtained by the method described below. The same procedure as in Example 14 was followed, except that the compound represented by formula (7-7) was used instead of the compound represented by formula (7-1), and 2.64 g of compound (P) (wherein Rf1 in formula (P) is the PFPE chain represented by formula (4-1) above. In the two Rf1s, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, represents 4.5) was obtained.

[0241] The obtained compound (P) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.60-1.80(4H), 2.00-2.10(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)

[0242] [Example 17] The compound represented by formula (Q) above was obtained by the method described below. The same procedure as in Example 14 was followed, except that the compound represented by formula (8-2) was used instead of the compound represented by formula (8-1), and 2.52 g of compound (Q) (wherein Rf1 in formula (Q) is the PFPE chain represented by formula (4-1) above; in the two Rf1s, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, represents 4.5) was obtained.

[0243] The obtained compound (Q) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.60-1.80(10H), 3.40-3.85(32H), 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)

[0244] [Example 18] The compound represented by the above formula (R) was obtained by the method shown below. The same procedure as in Example 14 was followed, except that the compound represented by formula (8-4) was used instead of the compound represented by formula (8-1), and 2.52 g of compound (R) (wherein Rf1 in formula (R) is the PFPE chain represented by formula (4-1) above; in the two Rf1s, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, represents 4.5) was obtained.

[0245] The obtained compound (R) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.60-1.80(4H), 3.40-3.85(44H), 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)

[0246] [Example 19] The compound represented by the above formula (S) was obtained by the method described below. HOCH2CF2O(CF2CF2O) h (CF2O) i Instead of the compound represented by CF2CH2OH, use HOCH2CF2CF2O(CF2CF2CF2O). jExcept for using a compound represented by CF2CF2CH2OH (where j, representing the average degree of polymerization, is 4.5), the same procedure as in Example 14 was followed to obtain 2.18 g of compound (S) (where Rf2 in formula (S) is the PFPE chain represented by formula (4-2) above; in the two Rf2s, j, representing the average degree of polymerization, is 4.5).

[0247] The obtained compound (S) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.60-1.80(4H), 3.40-3.85(32H), 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)

[0248] [Example 20] The compound represented by the above formula (T) was obtained by the method shown below. (First reaction step) A precursor compound represented by formula (10) was obtained in the same manner as in Example 14. Then, in the reaction to obtain the first intermediate compound in Example 14, the same procedure as in Example 14 was carried out, except that the compound represented by formula (12) was used instead of epibromohydrin, and 7.81 g of the compound represented by the following formula (13) was obtained as the first intermediate compound.

[0249] The compound represented by formula (12) is HOCH2CF2O(CF2CF2O) h (CF2O) i It was synthesized by reacting a compound 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) (number average molecular weight 1000, molecular weight distribution 1.1) with epibromohydrin.

[0250] [ka] (In formula (12), Rf1 is the PFPE chain represented by formula (4-1) above; in Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which also indicates the average degree of polymerization, represents 4.5.)

[0251] [ka] (In formula (13), Rf1 is the PFPE chain represented by formula (4-1) above; in the three Rf1s, h, which indicates the average degree of polymerization, represents 4.5, and i, which also indicates the average degree of polymerization, represents 4.5; THP represents a tetrahydropyranyl group.)

[0252] (Second reaction step) Under a nitrogen gas atmosphere, 7.81 g of the compound represented by formula (13), which is the first intermediate compound obtained above, 6.32 g of the compound represented by formula (8-1), and 20 mL of dimethylformamide were charged into a 100 mL round-bottom flask and stirred at room temperature until homogeneous. 1.08 g of sodium hydride was added to this homogeneous solution and the mixture was stirred at 40°C for 16 hours to allow the reaction to proceed.

[0253] The reaction mixture obtained after the reaction was allowed to return to room temperature, and 5 g of 10% hydrogen chloride-methanol solution (hydrogen chloride-methanol reagent (5-10%) manufactured by Tokyo Chemical Industry Co., Ltd.) was added and the mixture was stirred at room temperature for 4 hours. Then, the reaction mixture was gradually transferred to a separatory funnel containing 100 mL of saturated sodium bicarbonate solution and extracted twice with 200 mL of ethyl acetate. The organic layer was washed in the following order: 100 mL of saline solution, 100 mL of saturated sodium bicarbonate solution, and 100 mL of saline solution, and dehydrated with anhydrous sodium sulfate. After filtering off the drying agent, the filtrate was concentrated, and the residue was purified by silica gel column chromatography to obtain 2.71 g of compound (T) (Rf1 in formula (T) is the PFPE chain represented by formula (4-1) above. In the three Rf1s, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, represents 4.5).

[0254] The obtained compound (T)1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.60-1.80(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)

[0255] [Example 21] The compound represented by formula (U) above was obtained by the method described below. The same procedure as in Example 20 was followed, except that the compound represented by formula (7-3) was used instead of the compound represented by formula (7-1), to obtain 2.68 g of compound (U) (wherein Rf1 in formula (U) is the PFPE chain represented by formula (4-1) above. In the three Rf1s, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, also represents 4.5).

[0256] The obtained compound (U) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=3.40-3.85(54H), 3.85-4.10(12H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(27F), -78.5(6F), -80.5(6F), -91.0~-88.5(54F)

[0257] [Example 22] The compound represented by formula (V) above was obtained by the method shown below. The same procedure as in Example 20 was followed, except that the compound represented by formula (7-7) was used instead of the compound represented by formula (7-1), to obtain 2.92 g of compound (V) (wherein Rf1 in formula (V) is the PFPE chain represented by formula (4-1) above. In the three Rf1s, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, also represents 4.5).

[0258] The obtained compound (V) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.60-1.80(4H), 2.00-2.10(4H), 3.40-3.85(44H), 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)

[0259] [Example 23] The compound represented by the above formula (W) was obtained by the method shown below. The same procedure as in Example 20 was followed, except that the compound represented by formula (8-4) was used instead of the compound represented by formula (8-1), and 2.74 g of compound (W) (wherein Rf1 in formula (W) is the PFPE chain represented by formula (4-1) above. In the three Rf1s, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, also represents 4.5) was obtained.

[0260] The obtained compound (W) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.60-1.80(4H), 3.40-3.85(54H), 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)

[0261] [Example 24] The compound represented by formula (X) above was obtained by the method shown below. HOCH2CF2O(CF2CF2O) h (CF2O) i Instead of the compound represented by CF2CH2OH, use HOCH2CF2CF2O(CF2CF2CF2O). j Except for using a compound represented by CF2CF2CH2OH (where j, representing the average degree of polymerization, is 4.5), the same procedure as in Example 20 was followed to obtain 2.58 g of compound (X) (where Rf2 in formula (X) is the PFPE chain represented by formula (4-2) above; in the three Rf2s, j, representing the average degree of polymerization, is 4.5).

[0262] The obtained compound (X) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=1.60-1.80(4H), 3.40-3.85(42H), 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)

[0263] [Example 25] The compound represented by the above formula (XX) was obtained by the method shown below. The same procedure as in Example 14 was followed, except that the compound represented by formula (7-2) was used instead of the compound represented by formula (7-1), to obtain 2.45 g of compound (XX) (wherein Rf1 in formula (XX) is the PFPE chain represented by formula (4-1) above; in the two Rf1s, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, represents 4.5). The obtained compound (XX) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (acetone-D6): δ[ppm]=3.40-3.85(32H), 3.85-4.10(8H) 19 F-NMR (acetone-D6): δ[ppm]=-55.5~-51.5(18F), -78.5(4F), -80.5(4F), -91.0~-88.5(36F)

[0264] The values ​​of x and R obtained when compounds (A) to (X) and (XX) from Examples 1 to 25 are substituted into formula (1) are given by each of these examples. 1 , R 2 , R 3 , R 4 , R 5 , R 6 The structure is shown in Tables 1 and 2.

[0265] [Table 1]

[0266] [Table 2]

[0267] [Comparative Example 1] The compound represented by the following formula (Y) was synthesized by the method described in Patent Document 1.

[0268] [ka] (In formula (Y), Rf1 is the PFPE chain represented by formula (4-1) above; in Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which also indicates the average degree of polymerization, represents 4.5.)

[0269] [Comparative Example 2] The compound represented by the following formula (Z) was synthesized by the method described in Patent Document 2.

[0270] [ka] (In formula (Z), Rf1 is the PFPE chain represented by formula (4-1) above; in the two Rf1s, h, which indicates the average degree of polymerization, represents 4.5, and i, which indicates the average degree of polymerization, represents 4.5.)

[0271] [Comparative Example 3] The compound represented by the following formula (AA) was synthesized by the method described in Patent Document 3.

[0272] [ka] (In formula (AA), Rf2 is the PFPE chain represented by formula (4-2) above; in the two Rf2s, j, which indicates the average degree of polymerization, is 4.5.)

[0273] [Comparative Example 4] The compound represented by the following formula (AB) was synthesized by the method described in Patent Document 3.

[0274] [ka] (In formula (AB), Rf2 is the PFPE chain represented by formula (4-2) above; in the two Rf2s, j, which indicates the average degree of polymerization, is 4.5.)

[0275] [Comparative Example 5] The compound represented by the following formula (AC) was synthesized by the method described in Patent Document 4.

[0276] [ka] (In formula (AC), Rf1 is the PFPE chain represented by formula (4-1) above; in the three Rf1 values, h, which indicates the average degree of polymerization, represents 7.0, and i, which indicates the average degree of polymerization, represents 0.)

[0277] [Comparative Example 6] The compound represented by the following formula (AD) was synthesized by the method described in Patent Document 5.

[0278] [ka] (In formula (AD), Rf1 is the PFPE chain represented by formula (4-1) above; in Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which also indicates the average degree of polymerization, represents 4.5.)

[0279] [Comparative Example 7] The compound represented by the following formula (AE) was synthesized by the method described in Patent Document 5.

[0280] [ka] (In formula (AE), Rf1 is the PFPE chain represented by formula (4-1) above; in Rf1, h, which indicates the average degree of polymerization, represents 4.5, and i, which also indicates the average degree of polymerization, represents 4.5.)

[0281] The number-average molecular weight (Mn) of the compounds obtained in Examples 1-25 and Comparative Examples 1-7 was measured using the method described above. The results are shown in Tables 3 and 4.

[0282] Next, lubricating layer-forming solutions were prepared using the compounds obtained in Examples 1-25 and Comparative Examples 1-7 by the method described below. Then, using the obtained lubricating layer-forming solutions, a lubricating layer was formed on the magnetic recording medium by the method described below, obtaining the magnetic recording media of Examples 1-25 and Comparative Examples 1-7.

[0283] "Lubricant layer forming solution" The compounds obtained in Examples 1-25 and Comparative Examples 1-7 were each dissolved in Bartrell® XF (trade name, manufactured by Mitsui DuPont Fluorochemicals), a fluorine-based solvent, and then diluted with Bartrell XF to a film thickness of 9.0 Å to 9.5 Å when applied to a protective layer, to prepare a lubricating layer forming solution.

[0284] "Magnetic recording medium" A magnetic recording medium was prepared by sequentially layering an adhesive layer, a soft magnetic layer, a first underlayer, a second underlayer, a magnetic layer, and a protective layer on a substrate with a diameter of 65 mm. The protective layer was made of carbon. The lubricating layer-forming solutions of Examples 1-25 and Comparative Examples 1-7 were applied to the protective layer of the magnetic recording medium, which had each layer up to the protective layer formed, by the dipping method. The dipping method was performed under the following conditions: dipping speed of 10 mm / sec, dipping time of 30 sec, and withdrawal speed of 1.2 mm / sec. Subsequently, the magnetic recording medium coated with the lubricating layer-forming solution was placed in a constant temperature bath, and a heat treatment was performed at 120°C for 10 minutes to remove the solvent from the lubricating layer-forming solution and improve the adhesion between the protective layer and the lubricating layer, thereby forming a lubricating layer on the protective layer and obtaining a magnetic recording medium.

[0285] (Film thickness measurement) The thickness of the lubricating layer in the magnetic recording media of Examples 1-25 and Comparative Examples 1-7 obtained in this manner was measured using FT-IR (product name: Nicolet iS50, manufactured by Thermo Fisher Scientific). The results are shown in Tables 3 and 4.

[0286] Next, the magnetic recording media of Examples 1 to 25 and Comparative Examples 1 to 7 were subjected to the following chemical resistance tests and pickup characteristic tests.

[0287] [Chemical Resistance Testing] The contamination of magnetic recording media by environmental substances that generate pollutants under high-temperature conditions was investigated using the method described below. Si ions were used as the environmental substance, and the amount of Si adsorbed was measured as the amount of pollutant generated by the environmental substance that contaminates the magnetic recording media.

[0288] Specifically, the magnetic recording media under evaluation were kept in a high-temperature environment of 85°C and 0% humidity for 240 hours in the presence of siloxane-based Si rubber. Next, the amount of Si adsorbed on the surface of the magnetic recording media was analyzed and measured using secondary ion mass spectrometry (SIMS), and the degree of contamination by Si ions was evaluated as the amount of Si adsorbed. The evaluation of the amount of Si adsorbed was based on the following evaluation criteria, using the result of Comparative Example 1 as a baseline of 1.00. The results are shown in Tables 3 and 4.

[0289] "Evaluation Criteria" ◎(Excellent): Si adsorption amount is less than 0.70 (very low Si adsorption amount) ○ (Good): Si adsorption amount is 0.70 or higher and less than 0.90 (low Si adsorption amount) △ (Acceptable): Si adsorption amount is 0.90 or more and less than 1.10 (high Si adsorption amount) × (Not acceptable): Si adsorption amount is 1.10 or higher (very high Si adsorption amount)

[0290] [Pickup characteristics test] A magnetic recording medium and magnetic head were mounted on a spin stand and rotated under room temperature and reduced pressure (approximately 250 torr), allowing the magnetic head to levitate for 10 minutes. Subsequently, the surface of the magnetic head facing the magnetic recording medium was analyzed using an ESCA (Electron Spectroscopy for Chemical Analysis) analyzer. The intensity of the fluorine-derived peak (signal intensity (au)) obtained from the ESCA analysis indicates the amount of lubricant adhering to the magnetic head. The pickup characteristics were evaluated using the obtained signal intensity according to the evaluation criteria shown below. The results are shown in Tables 3 and 4.

[0291] "Evaluation Criteria" ◎(Excellent): Signal strength 160 or less (very low amount of adhesion) ○ (Good): Signal strength 161-300 (low amount of adhesion) △ (Acceptable): Signal strength 301-1000 (high amount of signal) × (Not acceptable): Signal strength 1001 or higher (very high amount of signal).

[0292] [Table 3]

[0293] [Table 4]

[0294] As shown in Table 3, the magnetic recording media of Examples 1 to 25, which had a lubricating layer formed using any of compounds (A) to (X), or (XX), all received an excellent (◎) or good (〇) rating in both the chemical resistance test and the pickup characteristic test. From this, it was confirmed that the lubricating layers of the magnetic recording media of Examples 1 to 25 have good chemical resistance and a high pickup suppression effect.

[0295] This is presumed to be because compounds (A) to (X), and (XX) are all fluorine-containing ether compounds represented by formula (1). More specifically, compounds (A) to (X), and (XX) are all perfluoropolyether chains (R 3 ) and terminal group (R 1 R placed between ) 2 , R 3 and terminal group (R 6 R placed between ) 5 , R 3 If you have 2 or 3 of them, then R 3 R placed between them 4 However, it is presumed that none of them contain secondary hydroxyl groups, and that they have side chain portions that branch off from the chain structure of fluorine-containing ether compounds and are bonded via ether links, and that these side chain portions have a primary hydroxyl group positioned at the tip, and that have a linking group containing a methylene group (-CH2-) that bonds the carbon atom to which the primary hydroxyl group is bonded to with the oxygen atom bonded to the carbon atom of the main chain portion.

[0296] In contrast, as shown in Table 4, Comparative Examples 1 to 7, which had a lubricating layer formed using any of compounds (Y) to (AE), all received evaluations of △ (acceptable) or × (unacceptable) in the chemical resistance test and the pickup characteristics test. This is presumed to be because, in Comparative Examples 1-6, the linking groups positioned between the perfluoropolyether chains and terminal groups, and / or between the perfluoropolyether chains themselves, formed a lubricating layer using compounds (Y)-(AD) containing secondary hydroxyl groups.

[0297] In Comparative Example 7, a lubricating layer was formed using compound (AE) that does not contain secondary hydroxyl groups. However, compound (AE) lacks a linking group between the perfluoropolyether chain and the terminal group, which includes a side chain portion that branches off from the chain structure of the fluorine-containing ether compound and is ether-bonded. More specifically, the two hydroxymethyl groups (-CH2OH) located at both ends of compound (AE) are not ether-bonded to the tertiary carbons that form the chain structure of the fluorine-containing ether compound, resulting in insufficient flexibility. Furthermore, in compound (AE), the two primary hydroxyl groups located at both ends are bonded to the tertiary carbons that form the chain structure of the fluorine-containing ether compound via one methylene group. As a result, in compound (AE), the distance between the tertiary carbons located at both ends and the two primary hydroxyl groups is short, and the movement of both primary hydroxyl groups is easily inhibited by the bulky tertiary carbons. Based on these findings, it is presumed that in Comparative Example 7, which had a lubricating layer formed using compound (AE), the fluidity around the primary hydroxyl groups in compound (AE) was insufficient, resulting in insufficient adsorption capacity due to the interaction between the primary hydroxyl groups and the active sites on the protective layer, leading to poor evaluation in the chemical resistance test and the pickup characteristic test.

[0298] Also, as shown in Table 3, among Examples 1 to 25, Examples 1 to 3 and 7 to 25 having a lubricating layer formed using compounds (A) to (C), (G) to (X), and (XX) that do not contain secondary hydroxyl groups all had an evaluation of ◎ (excellent) in the chemical substance resistance test, showing very good results. From this, it was confirmed that by using a compound that does not contain any secondary hydroxyl groups, a lubricating layer with even better chemical substance resistance can be obtained as compared to the case of using a compound in which R 1 and R 6 contain secondary hydroxyl groups.

[0299] Also, as shown in Table 3, Examples 1 and 3 both had an evaluation of ◎ (excellent) in the pickup property test, showing very good results. In contrast, Example 2 had an evaluation of ○ (good) in the pickup property test. This is because in Examples 1 and 3, compounds (A) and (C) in which the number of carbon atoms intervening between the hydroxyl group contained in R 1 (=R 6 ) and the tertiary carbon contained in R 2 (=R 5 ) is 2 or more were used, while in Example 2, compound (B) in which the number of carbon atoms intervening between the hydroxyl group contained in R 1 (=R 6 ) and the tertiary carbon contained in R 2 (=R 5 ) is 1 was used. Due to this difference, in compounds (A) and (C), the distance between the hydroxyl group contained in R 1 (=R 6 ) and R 2 (=R 5 ) is more appropriate than that in compound (B). As a result, in compounds (A) and (C), the movement of the primary hydroxyl group contained in R 1 (=R 6 ) is presumed to be less inhibited by the primary hydroxyl group possessed by R 2 (=R 5 ) and the bulky tertiary carbon contained in R 2 (=R 5 ) as compared to compound (B).

[0300] Furthermore, as shown in Table 3, both Examples 4 and 5 received an excellent (◎) rating in the pickup characteristics test, indicating very good results. In contrast, Example 6 received a good (〇) rating in the pickup characteristics test. In Examples 4 and 5, R 1 and R 6 While the above uses compounds (D) and (E) that do not contain a rigid structure, in Example 6, R 1 and R 6 This is because compound (F) contains a relatively rigid phenyl group. Due to this difference, compounds (D) and (E) have R compared to compound (F). 1 (=R 6 The movement of hydroxyl groups contained in ) is less likely to be inhibited, R 1 and R 6 This is presumed to be because the hydroxyl groups inside can move freely. [Industrial applicability]

[0301] The present invention provides a fluorine-containing ether compound that has excellent chemical resistance and can form a lubricating layer that can suppress pickup. By using the lubricant for magnetic recording media containing the fluorine-containing ether compound of the present invention, it is possible to form a lubricating layer with good chemical resistance and a high pickup suppression effect, even if the thickness is thin. [Explanation of symbols]

[0302] 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 characterized by being represented by the following formula (1). R １ -R ２ -CH ２ -R ３ [-CH ２ -R ４ -CH ２ -R ３ ] ｘ -CH ２ -R ５ -R ６ (1) (In formula (1), R １ and R ６ Each of these is independently a terminal group represented by one of the following formulas (5-1) to (5-8); R ２ R is a divalent linking group represented by the following formula (2-1) or (2-2); R ５ R is a divalent linking group represented by the following formula (2-3) or (2-4); x represents an integer from 0 to 2; R ３ is a perfluoropolyether chain; if x is 1 or 2, then 2 or 3 R ３ They may be partially or entirely the same, or they may be different; R ４ is a divalent linking group represented by the following formula (3-1) or (3-2); when x is 2, two R ４ They may be the same, or they may be different. 【Chemistry 1】 (In equation (2-1), n1 represents an integer from 2 to 4; in equation (2-1), the dotted line bonded to the carbon atom is R １ The dotted lines indicate bonds with the oxygen atom, and the dotted lines indicate bonds with the methylene group. (In equation (2-2), the dotted line bonded to the carbon atom is R １ The dotted lines indicate bonds with the oxygen atom, and the dotted lines indicate bonds with the methylene group. (In equation (2-3), n² represents an integer from 2 to 4; in equation (2-3), the dotted line bonded to the carbon atom is R ６ The dotted lines indicate bonds with the oxygen atom, and the dotted lines indicate bonds with the methylene group. (In equation (2-4), the dotted line bonded to the carbon atom is R ６ The dotted lines indicate bonds with the oxygen atom, and the dotted lines indicate bonds with the methylene group. (In equation (3-1), n3 represents an integer from 2 to 4; y1 represents an integer from 1 to 3; y2 represents an integer from 1 to 3; at least one of y1 and y2 is 1; the dotted line bonded to the oxygen atom on the left is R) １ The dotted line indicates the bond to the methylene group on the side, and the bond to the oxygen atom on the right is R. ６ (This shows the bond connecting to the methylene group on the side.) (In equation (3-2), y3 represents an integer from 1 to 3; y4 represents an integer from 1 to 3; at least one of y3 and y4 is 1; the dotted line bonded to the oxygen atom on the left is R) １ The dotted line indicates the bond to the methylene group on the side, and the bond to the oxygen atom on the right is R. ６ (This shows the bond connecting to the methylene group on the side.) 【Chemistry 2】 (The dotted lines in equations (5-1) to (5-8) represent R ２ or R ５ (This shows the bonds that the atom possesses to the carbon atoms.)

2. R in formula (1) ２ The above equation (2-1) is given by R ５ The above equation (2-3) is given by x R ４ The fluorine-containing ether compound according to claim 1, wherein all are of formula (3-1), and in formula (3-1), y1 is 1 and y2 is 1.

3. The fluorine-containing ether compound according to claim 2, wherein the values ​​of n1 in formula (2-1), n2 in formula (2-3), and n3 in formula (3-1) are all the same.

4. R in formula (1) ２ This is the above equation (2-2), and R ５ The above equation (2-4) is given by x R ４ The fluorine-containing ether compound according to claim 1, wherein all are of formula (3-2), and in formula (3-2), y3 is 1 and y4 is 1.

5. R in formula (1) １ and R ６ The fluorine-containing ether compound according to claim 1, wherein the total number of polar groups selected from the group consisting of hydroxyl groups, cyano groups, and groups having an acetamide bond is 2 to 4.

6. R in formula (1) １ -R ２ - and R ６ -R ５ The fluorine-containing ether compound according to claim 1, wherein the - is the same.

7. The (x+1) Rs in equation (1) above ３ The fluorine-containing ether compound according to claim 1, wherein each of them is 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 equation (4), w2, w3, w4, and w5 represent the average degree of polymerization and each independently represents a value from 0 to 20; however, w2, w3, w4, and w5 cannot all be 0 at the same time; w1 and w6 are CF ２ The average value representing the number of such numbers, each independently representing 1 to 3; the repeating unit in equation (4) (CF ２ O), (CF ２ CF ２ O), (CF ２ CF ２ CF ２ O), (CF ２ CF ２ CF ２ CF ２ There are no particular restrictions on the order of the elements in (O).

8. The (x+1) Rs in equation (1) above ３ The fluorine-containing ether compound according to claim 1, wherein each of them is independently selected from any one of the 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, where h is between 1 and 20, and i is between 0 and 20.) -CF ２ CF ２ -(OCF ２ CF ２ CF ２ ) ｊ -OCF ２ CF ２ - (4-2) (In formula (4-2), j represents the average degree of polymerization and is expressed as 1 to 15.) -CF ２ CF ２ CF ２ -(OCF ２ CF ２ CF ２ CF ２ ) ｋ -OCF ２ CF ２ CF ２ - (4-3) (In formula (4-3), k represents the average degree of polymerization and is expressed as 1 to 10.) -(CF ２ ) ｗ７ -O-(CF ２ CF ２ CF ２ O) ｗ８ -(CF ２ CF ２ O) ｗ９ -(CF ２ ) ｗ１０ - (4-4) (In formula (4-4), w8 and w9 represent the average degree of polymerization and each independently represents 1 to 20; w7 and w10 are CF ２ This represents the average number of [something], and each independently represents 1 to 2.

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

10. A lubricant for magnetic recording media, characterized by containing the fluorine-containing ether compound described in claim 1.

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 characterized in that the lubricating layer contains the fluorine-containing ether compound described in claim 1.

12. The magnetic recording medium according to claim 11, wherein the average thickness of the lubricating layer is 0.5 nm to 2.0 nm.

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