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-CH2-R2-(CH2-R3-CH2-R2)z-CH2-R4 (z represents 1 or 2. R2 represents a perfluoropolyether chain. R1 is indicated by formula (2). R4 represents an organic group having 3-35 constituent carbon atoms and 1-3 polar groups. R3 is indicated by formula (4).)

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. 2023-071338, filed in Japan on April 25, 2023, and the contents of that application are incorporated herein by reference. [Background technology]

[0002] To increase the recording density in magnetic recording and playback devices, development of magnetic recording media suitable for high recording densities is underway. Conventionally, magnetic recording media have been designed in which a recording layer is formed on a substrate, and a protective layer made of carbon or the like is 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. In addition, the protective layer covers the recording layer, preventing the metal contained in the recording layer from being corroded by environmental substances.

[0003] However, the durability of magnetic recording media cannot be sufficiently achieved by simply providing a protective layer on the recording layer. Therefore, a lubricant is applied to the surface of the protective layer to form a lubricating layer. The lubricating layer, which is placed on the outermost surface of the magnetic recording media, is required to improve the durability and protective power of the protective layer, as well as the levitation stability and wear resistance of the magnetic head.

[0004] As a lubricant used when forming a lubricating layer of a magnetic recording medium, a compound containing a polar group such as a hydroxyl group at the end of a fluorine-based polymer having a repeating structure containing -CF2- has been proposed (see, for example, Patent Documents 1 to 6).

[0005] Patent documents 1 to 4 disclose fluorine-containing ether compounds having a skeleton in which multiple perfluoropolyether chains are linked via linking groups having secondary hydroxyl groups, and terminal groups having polar groups are bonded to both sides via methylene groups (-CH2-).

[0006] Patent Document 5 discloses a method for producing polyol perfluoropolyether compounds useful as lubricants for magnetic media. Patent Document 5 describes a method for producing polyol (per)fluoropolyether derivatives by synthesizing an activated protected triol by reacting a triol with an activator, and then subjecting the activated triol to a nucleophilic substitution reaction with hydroxyl groups located at both ends of a functional (per)fluoropolyether.

[0007] Patent Document 6 discloses a fluorine-containing ether compound that contains one perfluoropolyether chain within the molecule, with terminal groups each containing two primary hydroxyl groups attached to both ends. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] International Publication No. 2021 / 251335 [Patent Document 2] International Publication No. 2016 / 084781 [Patent Document 3] U.S. Patent Application Publication No. 2016 / 0260452 [Patent Document 4] International Publication No. 2018 / 116742 [Patent Document 5] Patent No. 5334064 [Patent Document 6] International Publication No. 2022 / 131202 [Overview of the project] [Problems that the invention aims to solve]

[0009] To increase the capacity of magnetic recording and playback devices, development of magnetic recording media suitable for high recording densities is progressing. In recent years, in order to improve the recording density of magnetic recording media, there has been a demand to further shorten the distance between the magnetic head and the magnetic layer of the magnetic recording media, thereby reducing magnetic spacing (levitation height). For this reason, there is a demand to further reduce the thickness of the protective layer and / or lubricating layer in the magnetic recording media. However, generally speaking, reducing the thickness of the lubricating layer tends to decrease the coverage of the lubricating layer, which in turn tends to reduce the wear resistance and smoothness of the magnetic recording medium.

[0010] The present invention has been made in view of the above circumstances, and aims to provide a fluorine-containing ether compound that has excellent wear resistance and can form a smooth lubricating layer, and can be suitably used as a material for a lubricant for magnetic recording media.

[0011] Furthermore, the present invention aims to provide a lubricant for magnetic recording media that contains the fluorine-containing ether compound of the present invention, has excellent wear resistance, and can form a smooth lubricating layer. Furthermore, the present invention aims to provide a magnetic recording medium that contains the fluorine-containing ether compound of the present invention, has excellent wear resistance, and has a smooth lubricating layer. [Means for solving the problem]

[0012] The inventors of this invention have diligently conducted research to solve the above problems. As a result, it has been found that a fluorine-containing ether compound having a skeleton in which two or three perfluoropolyether chains are bonded via a divalent linking group having only one secondary hydroxyl group between adjacent perfluoropolyether chains via a methylene group (-CH2-), and having two groups composed of an organic group having 3 to 35 carbon atoms, which do not contain secondary hydroxyl groups and tertiary hydroxyl groups but contain one primary hydroxyl group, bonded to a trisubstituted carbon atom via a methylene group at at least one end of the skeleton, and having a specific branched terminal group at only one end, and an organic group having 3 to 35 carbon atoms and having 1 to 3 polar groups arranged at the other end via a methylene group, leading to the conception of the present invention. That is, the present invention relates to the following matters.

[0013] [1] A fluorine-containing ether compound characterized by being represented by the following formula (1). R 1 -CH2-R 2 -(CH2-R 3 -CH2-R 2 ) z -CH2-R 4 (1) (In formula (1), z is 1 or 2. R 2 is a perfluoropolyether chain. (z + 1) R 2 may be partly or entirely the same, or may be different from each other. R 1 is a branched terminal group having 3 to 35 carbon atoms represented by the following formula (2). R 4 is an organic group having 3 to 35 carbon atoms and having 1 to 3 polar groups, and may be the same as or different from R 1 . R 3 is a divalent linking group represented by the following formula (4). When z is 2, the two R 3 may be the same or different.)

[0014]

Chemical formula

[0015] [2] The fluorine-containing ether compound according to [1], wherein formula (2) is a group represented by either formula (2-1) or (2-2) below.

[0016] [ka] (In equation (2-1), a is an integer between 1 and 3, and b is an integer between 1 and 4. X 1 X is a hydrogen atom or a group represented by formula (3). 2 X is a base represented by equation (3). 1 and X 2 They may be the same or different. (In equation (2-2), c is an integer between 0 and 3, and d and e are independent integers between 1 and 5. X 3 and X 4 Each of these is independently a hydrogen atom or a group represented by formula (3). 3 and X 4 They may be the same or different. (In equation (3), f is an integer between 2 and 5, and g is either 1 or 2.)

[0017] [3] R in equation (1) above 4 The fluorine-containing ether compound described in [1] or [2], wherein the group is represented by formula (2) above. [4] R in equation (1) above 1 and R 4 The fluorine-containing ether compound according to [2], wherein both are independently represented by formula (2-1) or (2-2). [5] In equation (1) above, R 1 and R 4 A fluorine-containing ether compound described in any of [1] to [4], which is identical to the other.

[0018] [6] R in equation (1) above 4 However, the fluorine-containing ether compound described in [1] or [2] is one of the groups shown in the following formulas (6-1) to (6-3).

[0019] [ka] (In equation (6-1), y1 is 1 or 2, and y2 is an integer from 0 to 3. X 5 is an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, an alkynyl group, or a polar group. When y1 is 1, X 5 X is a polar group. 5 If X is an aromatic hydrocarbon group or an unsaturated heterocyclic group, 5 The atoms that make up the ring structure inside are X 5 It bonds to the adjacent methylene group. 5 If X is an alkenyl group or an alkynyl group, 5 The carbon atoms that make up the unsaturated bond inside are X 5 It bonds to the adjacent methylene group. (In equation (6-2), y3 is an integer between 1 and 3, y4 is 0 or 1, and y5 is an integer between 0 and 3. X 5 is an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, an alkynyl group, or a polar group. When y4 is 0, X 5 X is a polar group. 5 If X is an aromatic hydrocarbon group or an unsaturated heterocyclic group, 5 The atoms that make up the ring structure inside are X 5 It bonds to the adjacent methylene group. 5 If X is an alkenyl group or an alkynyl group, 5 The carbon atoms that make up the unsaturated bond inside are X 5 It bonds to the adjacent methylene group. (In equation (6-3), y6 is 0 or 1, y7 is an integer from 1 to 3, and y8 is an integer from 1 to 3. X 5is an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, an alkynyl group, or a polar group. When y6 is 0, X 5 X is a polar group. 5 If X is an aromatic hydrocarbon group or an unsaturated heterocyclic group, 5 The atoms that make up the ring structure inside are X 5 It bonds to the adjacent methylene group. 5 If X is an alkenyl group or an alkynyl group, 5 The carbon atoms that make up the unsaturated bond inside are X 5 It bonds to the adjacent methylene group.

[0020] [7] (z+1) R in equation (1) above 2 However, each is independently a perfluoropolyether chain represented by the following formula (5), which is a fluorine-containing ether compound as described in any of [1] to [6]. -(CF2) w1 -O-(CF2O) w2 -(CF2CF2O) w3 -(CF2CF2CF2O) w4 -(CF2CF2CF2CF2O) w5 -(CF2) w6 - (5) (In equation (5), 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 (5).)

[0021] [8] (z+1) R in equation (1) above 2 However, each is independently selected from the perfluoropolyether chains represented by the following formulas (5-1) to (5-4), and is a fluorine-containing ether compound as described in any of [1] to [7]. -CF2-(OCF2CF2) j -(OCF2) k-OCF2-(5-1) (In formula (5-1), j and k represent the average degree of polymerization, j represents 1 to 20, and k represents 0 to 20.) -CF2CF2-(OCF2CF2CF2) l -OCF2CF2-(5-2) (In formula (5-2), l represents the average degree of polymerization and represents 1 to 15.) -CF2CF2CF2-(OCF2CF2CF2CF2) m -OCF2CF2CF2-(5-3) (In formula (5-3), m represents the average degree of polymerization and represents 1 to 10.) -(CF2) w7 -O-(CF2CF2CF2O) w8 -(CF2CF2O) w9 -(CF2) w10 -(5-4) (In formula (5-4), w8 and w9 represent the average degree of polymerization and each independently represents 1 to 20. w7 and w10 are average values representing the number of CF2s and each independently represents 1 to 2.)

[0022] [9] The fluorine-containing ether compound according to any one of [1] to [8], wherein all of the (z + 1) Rs in the formula (1) are the same. 2

[10] The fluorine-containing ether compound according to any one of [1] to [9], having a number average molecular weight in the range of 500 to 10,000.

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

[10] .

[0023]

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

[10] .

[13] The magnetic recording medium according to

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

[0024] 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. Because the lubricant for magnetic recording media of the present invention contains the fluorine-containing ether compound of the present invention, it is possible to form a lubricating layer with excellent wear resistance and smoothness even when the thickness is reduced. The magnetic recording medium of the present invention has a lubricating layer containing the fluorine-containing ether compound of the present invention, which has excellent wear resistance and smoothness. Therefore, the magnetic recording medium of the present invention has excellent reliability and durability. [Brief explanation of the drawing]

[0025] [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]

[0026] To solve the above problems, the inventors focused on the relationship between the molecular structure of the fluorine-containing ether compound contained in the lubricant and the protective layer, and diligently conducted research as shown below. Conventionally, fluorine-containing ether compounds having polar groups such as hydroxyl groups have been used as materials for lubricants for magnetic recording media applied to the surface of protective layers (hereinafter sometimes abbreviated as "lubricant").

[0027] Some fluorine-containing ether compounds have polar groups, with terminal groups containing multiple polar groups located at the ends of their chain-like structures. Others have multiple perfluoropolyether chains with linking groups containing polar groups located between adjacent perfluoropolyether chains. In a lubricating layer containing a fluorine-containing ether compound, the polar groups in the fluorine-containing ether compound bind to active sites on the protective layer, improving the adhesion of the lubricating layer to the protective layer.

[0028] However, conventional lubricating layers containing fluorine-containing ether compounds sometimes failed to achieve sufficient adhesion to the protective layer, even when formed using fluorine-containing ether compounds with multiple polar groups in their molecules. One possible method to improve the adhesion of the lubricating layer to the protective layer is to use fluorine-containing ether compounds with a larger number of polar groups. However, lubricating layers formed using such fluorine-containing ether compounds sometimes failed to achieve sufficient smoothness and wear resistance for magnetic recording media.

[0029] Therefore, the inventors focused on the bonding between polar groups contained in fluorine-containing ether compounds and active sites on the protective layer, and conducted extensive research. As a result, we found that the fluorine-containing ether compound has a skeleton having two or three perfluoropolyether chains, as represented by formula (1) above, with a divalent linking group represented by formula (4) above, having only one secondary hydroxyl group, bonded between adjacent perfluoropolyether chains via a methylene group (-CH2-), and at least one end of the skeleton has a branched terminal group represented by formula (2) above, which consists of organic groups with 3 to 35 constituent carbon atoms, does not contain secondary or tertiary hydroxyl groups, but contains one primary hydroxyl group, bonded to a trisubstituted carbon atom via a methylene group, and if only one end is a branched terminal group represented by formula (2), then the other end has an organic group with 3 to 35 constituent carbon atoms having 1 to 3 polar groups, bonded via a methylene group.

[0030] The lubricating layer containing the fluorine-containing ether compound represented by formula (1) above is presumed to have good smoothness and excellent wear resistance due to the synergistic effect of the following actions and functions. The secondary hydroxyl group of the linking group represented by formula (4) and the primary hydroxyl group of the branched terminal group represented by formula (2) contained in the fluorine-containing ether compound represented by formula (1) are as follows: <1> ~ <3> For this reason, it is more likely to engage in binding with active sites present on the protective layer.

[0031] <1> In the fluorine-containing ether compound represented by formula (1), a divalent linking group represented by formula (4), which has only one secondary hydroxyl group, is bonded between two or three perfluoropolyether chains. Therefore, for example, if there are two divalent linking groups represented by formula (4), the perfluoropolyether chain is positioned between the divalent linking groups. Thus, even with two divalent linking groups represented by formula (4), the distance between the secondary hydroxyl groups does not become too close. Therefore, even with two divalent linking groups represented by formula (4), neither of the two secondary hydroxyl groups has its binding to the active site on the protective layer inhibited by the adjacent secondary hydroxyl group.

[0032] Furthermore, in the fluorine-containing ether compound represented by formula (1), perfluoropolyether chains are positioned between the divalent linking group represented by formula (4) and both terminal groups. Therefore, the secondary hydroxyl group contained in the divalent linking group represented by formula (4) does not become too close to the polar groups contained in both terminal groups. As a result, the secondary hydroxyl group contained in the divalent linking group represented by formula (4) is not inhibited from binding to the active site on the protective layer by the polar groups contained in both terminal groups. Thus, the secondary hydroxyl group contained in the divalent linking group represented by formula (4) is more likely to participate in binding to the active site on the protective layer.

[0033] <2> In the fluorine-containing ether compound represented by formula (1), perfluoropolyether chains are positioned between the divalent linking group represented by formula (4) and both terminal groups. Therefore, the secondary hydroxyl group contained in the divalent linking group represented by formula (4) does not inhibit the binding of the polar groups contained in both terminal groups to the active sites on the protective layer, and the secondary hydroxyl group contained in the divalent linking group represented by formula (4) and the polar groups contained in each terminal group are less likely to aggregate. Thus, in the fluorine-containing ether compound represented by formula (1), not only the secondary hydroxyl group contained in the divalent linking group but also the polar groups contained in each terminal group readily bind to the active sites on the protective layer.

[0034] <3> At least one of the terminal groups is a branched terminal group represented by formula (2), in which two organic groups, each containing one primary hydroxyl group, are bonded to a trisubstituted carbon atom, and the distance between the two primary hydroxyl groups in formula (2) is appropriate. For this reason, in the fluorine-containing ether compound represented by formula (1), aggregation due to the distance between the two primary hydroxyl groups in the branched terminal group represented by formula (2) being too close is unlikely to occur, and the two primary hydroxyl groups do not inhibit each other from binding to the active site on the protective layer.

[0035] Furthermore, since the branched terminal group represented by formula (2) is an organic group with 3 to 35 constituent carbon atoms, the distance between the two primary hydroxyl groups contained in the branched terminal group is never too far. Therefore, when one of the primary hydroxyl groups contained in the branched terminal group represented by formula (2) bonds to the protective layer, the other primary hydroxyl group also moves closer to the protective layer. As a result, the other primary hydroxyl group can adopt an orientation that easily attracts adsorption to the protective layer. Thus, the two primary hydroxyl groups contained in the branched terminal group represented by formula (2) readily bond to active sites on the protective layer simultaneously.

[0036] Furthermore, the branched terminal group represented by formula (2) contains no secondary or tertiary hydroxyl groups, but two organic groups, each containing one primary hydroxyl group, are bonded to a trisubstituted carbon atom. For this reason, the area around the two primary hydroxyl groups in the branched terminal group represented by formula (2) is sterically more open than, for example, the area around the secondary hydroxyl groups bonded to carbon atoms forming the chain structure of a fluorine-containing ether compound. Also, since two organic groups, each containing one primary hydroxyl group, are bonded to a trisubstituted carbon atom, the distance between the two primary hydroxyl groups and the adjacent perfluoropolyether chain is appropriate. Therefore, the binding of the two primary hydroxyl groups to the active site on the protective layer is less likely to be inhibited by the bulky portion in the fluorine-containing ether compound represented by formula (1), the adjacent perfluoropolyether chain, and the trisubstituted carbon atom in the branched terminal group represented by formula (2).

[0037] Furthermore, primary hydroxyl groups generally have a high degree of freedom and can move freely compared to secondary and tertiary hydroxyl groups. Therefore, the two primary hydroxyl groups contained in the branched terminal group represented by formula (2) can each spontaneously move relative to the active sites on the protective layer. Thus, both of the two primary hydroxyl groups contained in the branched terminal group can easily form bonds with the active sites on the protective layer.

[0038] For the reasons <1> to <3> above, the secondary hydroxyl group of the linking group represented by formula (4) and the primary hydroxyl group of the branched terminal group represented by formula (2) contained in the fluorine-containing ether compound represented by formula (1) are likely to participate in the bonding with the active sites present on the protective layer. For this reason, the lubricating layer containing the fluorine-containing ether compound represented by formula (1) is adhered to the protective layer by the secondary hydroxyl group contained in the linking group represented by formula (4) disposed between adjacent perfluoropolyether chains and the two primary hydroxyl groups of the branched terminal group represented by formula (2) disposed at at least one end, and has good adhesion to the protective layer.

[0039] Moreover, the lubricating layer containing the fluorine-containing ether compound represented by formula (1) has appropriate flexibility due to the fact that the end bonded to the adjacent methylene group in the branched terminal group represented by formula (2) is an oxygen atom, which results from bonding to the adjacent methylene group through an ether bond. Furthermore, the lubricating layer containing the fluorine-containing ether compound represented by formula (1) has sufficient fluidity and flexibility due to the high mobility of the two primary hydroxyl groups contained in the branched terminal group represented by formula (2). From these facts, the lubricating layer containing the fluorine-containing ether compound represented by formula (1) has very good adhesion to the protective layer.

[0040] Thus, the fluorine-containing ether compound represented by formula (1) can form a lubricating layer with good adhesion to the protective layer, and the perfluoropolyether chains in the fluorine-containing ether compound contained in the lubricating layer can adopt a structure that adheres closely to the protective layer without separating too far from it. Therefore, the state on the protective layer is less likely to be bulky, a lubricating layer with suppressed surface irregularities can be obtained, and a lubricating layer with good coating properties that spreads easily on the protective layer and has a uniform coating state can be formed. As a result, it is estimated that the fluorine-containing ether compound represented by formula (1) can form a lubricating layer with excellent wear resistance and good smoothness.

[0041] Furthermore, because the lubricating layer containing the fluorine-containing ether compound represented by formula (1) has sufficient fluidity and flexibility, even if a part of the lubricating layer deforms due to wear and the fluorine-containing ether compound in the lubricating layer moves to another location, it has a high restorative power that allows it to return to its original position. From this, it is presumed that the lubricating layer containing the fluorine-containing ether compound represented by formula (1) will have better smoothness and superior wear resistance.

[0042] In contrast, if, for example, a fluorine-containing ether compound contains polar groups that are not involved in bonding with active sites on the protective layer, the adhesion between the lubricating layer and the protective layer becomes insufficient. As a result, the fluorine-containing ether compounds in the lubricating layer may aggregate locally, or some molecules of the fluorine-containing ether compounds may lift off the surface of the protective layer, creating irregularities on the surface of the lubricating layer. This causes the lubricant in the lubricating layer to become bulky, resulting in uneven coating of the lubricating layer over the protective layer, making it difficult to obtain a lubricating layer with good coverage and smoothness. Furthermore, if the adhesion between the lubricating layer and the protective layer is insufficient, high-speed rotation of the magnetic recording medium can cause changes in the state of the lubricating layer on the surface of the magnetic recording medium, reducing the wear resistance of the lubricating layer and decreasing the durability and reliability of the magnetic recording medium.

[0043] Specifically, for example, if a divalent linking group having two or more secondary hydroxyl groups is used instead of a divalent linking group represented by formula (4) having only one secondary hydroxyl group, the two or more secondary hydroxyl groups of the divalent linking group tend to inhibit each other from bonding with the active sites on the protective layer. As a result, at least some of the two or more secondary hydroxyl groups tend to become polar groups that do not participate in bonding with the active sites on the protective layer, and these polar groups that do not participate in bonding with the active sites on the protective layer may attract intermolecular and / or intramolecular polar groups, resulting in a fluorine-containing ether compound that is prone to aggregation. Therefore, if a divalent linking group having two or more secondary hydroxyl groups is used instead of a divalent linking group represented by formula (4), it is difficult to form a lubricating layer with good wear resistance and smoothness.

[0044] 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 to form a lubricating layer on the protective layer of a magnetic recording medium, a lubricating layer with excellent wear resistance and good smoothness can be formed.

[0045] The fluorine-containing ether compounds, lubricants for magnetic recording media, and magnetic recording media of the present invention will be described in detail below. However, the present invention is not limited to the embodiments shown below. Within the scope of the present invention, additions, omissions, substitutions, and modifications are possible in terms of number, quantity, ratio, composition, type, position, material, and structure.

[0046] [Fluorine-containing ether compounds] The fluorine-containing ether compound of this embodiment is represented by the following formula (1). R 1 -CH2-R 2 -(CH2-R 3 -CH2-R 2 ) z -CH2-R 4 (1) (In equation (1), z is either 1 or 2. R 2 This is a perfluoropolyether chain. (z+1) R 2These may be partially or entirely identical, or they may be different. 1 R is a branched terminal group with 3 to 35 constituent carbon atoms, represented by the following formula (2). 4 R is an organic group having 1 to 3 polar groups and 3 to 35 constituent carbon atoms. 1 It may be the same as or different from R. 3 This is a divalent linking group represented by the following formula (4). When z is 2, two R 3 They may be the same or they may be different.

[0047] [ka] (In equation (2), R 5 and R 6 x is an organic group that contains one primary hydroxyl group but no secondary or tertiary hydroxyl groups, and may be the same or different. x is an integer between 0 and 3. (In equation (4), h is an integer between 1 and 3, and i is an integer between 1 and 3.)

[0048] In the fluorine-containing ether compound represented by formula (1), z is 1 or 2. Since z is 2 or less, the molecule of the fluorine-containing ether compound represented by formula (1) does not become too large. 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, since z is 1 or greater, a divalent linking group represented by formula (4) having a secondary hydroxyl group can be placed between adjacent perfluoropolyether chains. Therefore, the central part of the chain structure of the fluorine-containing ether compound adheres closely to the protective layer, resulting in a fluorine-containing ether compound that can form a lubricating layer with better adhesion to the protective layer compared to, for example, the case where z is 0 (when there is only one perfluoropolyether chain).

[0049] (R 2 (Perfluoropolyether chains shown as) In the fluorine-containing ether compound represented by formula (1), (z+1) R 2is independently a perfluoropolyether chain (hereinafter sometimes referred to as "PFPE chain"). R 2 The PFPE chain represented by 2 coats the surface of the protective layer and imparts lubricity to the lubricating layer to reduce the frictional force between the magnetic head and the protective layer when a lubricant containing the fluorinated ether compound of the present embodiment is applied onto the protective layer to form a lubricating layer. R 2 The PFPE chain represented by 2 is appropriately selected according to the performance required for the lubricant containing the fluorinated ether compound and the like.

[0050] In the fluorinated ether compound represented by formula (1), (z + 1) R 2 may be partly or entirely the same, or may be different from each other. It is preferable that all of (z + 1) R 2 are the same. This is because the coating state of the fluorinated ether compound on the protective layer becomes uniform, and a lubricating layer with better adhesion is obtained. Two or more of (z + 1) R 2 being the same means that among (z + 1) R 2 , there are two or more R 2 having the same structure of the repeating unit of the PFPE chain. The same R 2 includes those having the same structure of the repeating unit but different average degrees of polymerization. 2

[0051] Examples of the PFPE chain represented by R 2 include those composed of a polymer or copolymer of perfluoroalkylene oxide. Examples of perfluoroalkylene oxide include perfluoromethylene oxide, perfluoroethylene oxide, perfluoro-n-propylene oxide, perfluoroisopropylene oxide, perfluorobutylene oxide, and the like.

[0052] It is preferable that each of (z + 1) R 2 in formula (1) is independently a PFPE chain represented by the following formula (5) derived from a polymer or copolymer of perfluoroalkylene oxide. -(CF2) w1 -O-(CF2O) w2 -(CF2CF2O) w3 -(CF2CF2CF2O) w4 -(CF2CF2CF2CF2O) w5 -(CF2) w6 - (5) (In equation (5), 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 (5).)

[0053] In formula (5), w2, w3, w4, and w5 represent the average degree of polymerization, each independently representing a range of 0 to 20, preferably 0 to 15, and more preferably 0 to 10. In equation (5), 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 (5). In equation (5), (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 (5). There are also no particular restrictions on the number of different types of repeating units in equation (5).

[0054] (z+1) R in equation (1) 2 Preferably, each of these is independently selected from the PFPE chains represented by the following formulas (5-1) to (5-4). (z+1) R 2 However, if any one of the PFPE chains represented independently by formulas (5-1) to (5-4) is selected, it becomes a fluorine-containing ether compound that yields a lubricating layer with good lubricity. Also, (z+1) R 2However, if one of the PFPE chains represented independently by formulas (5-1) to (5-4) 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 an even thinner lubricating layer can be formed with sufficient coverage.

[0055] -CF2-(OCF2CF2) j -(OCF2) k -OCF2- (5-1) (In equation (5-1), j and k represent the average degree of polymerization, where j is between 1 and 20, and k is between 0 and 20.) -CF2CF2-(OCF2CF2CF2) l -OCF2CF2- (5-2) (In formula (5-2), l represents the average degree of polymerization and is expressed as 1 to 15.) -CF2CF2CF2-(OCF2CF2CF2CF2) m -OCF2CF2CF2- (5-3) (In equation (5-3), m represents the average degree of polymerization and is expressed as 1 to 10.) -(CF2) w7 -O-(CF2CF2CF2O) w8 -(CF2CF2O) w9 -(CF2) w10 - (5-4) (In equation (5-4), w8 and w9 represent the average degree of polymerization, each independently representing a value between 1 and 20. w7 and w10 are average values ​​representing the number of CF2 molecules, each independently representing a value between 1 and 2.)

[0056] In formula (5-1), there are no particular restrictions on the sequence order of the repeating units, (OCF2CF2) and (OCF2). In formula (5-1), the number of (OCF2CF2) units j and the number of (OCF2) units k may be the same or different. The PFPE chain represented by formula (5-1) may be a polymer of (OCF2CF2). Furthermore, the PFPE chain represented by formula (5-1) may be a random copolymer, block copolymer, or alternating copolymer composed of (OCF2CF2) and (OCF2).

[0057] In formulas (5-1) to (5-3), the average degree of polymerization is 1 to 20 for j, 0 to 20 for k, 1 to 15 for l, and 1 to 10 for m, resulting in a fluorine-containing ether compound that yields a lubricating layer with good lubricity. Furthermore, in formulas (5-1) to (5-3), the average degrees of polymerization are 20 or less for j and k, 15 or less for l, and 10 or less for m, 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 j, k, l, and m 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.

[0058] In formula (5-4), there are no particular restrictions on the order of the repeating units (CF2CF2CF2O) and (CF2CF2O). In formula (5-4), the number of (CF2CF2CF2O) units w8 and the number of (CF2CF2O) units w9 may be the same or different. Formula (5-4) may include any of the monomer units (CF2CF2CF2O) and (CF2CF2O), such as a random copolymer, a block copolymer, or an alternating copolymer.

[0059] In formula (5-4), w8 and w9, which represent the average degree of polymerization, are independently 1 to 20, preferably 1 to 15, and more preferably 1 to 10. In formula (5-4), w7 and w10 are average values ​​indicating the number of CF2 molecules, 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 perfluoropolyether chain represented by formula (5-4).

[0060] (R 3 (The divalent linking group shown by) In the fluorine-containing ether compound represented by formula (1), R 3 R is a divalent linking group represented by formula (4). 3 This is (z+1) R 2 They are positioned between the PFPE chains shown by . 3 This involves adhering the fluorine-containing ether compound to the protective layer, forming a thin lubricating layer with sufficient coverage.

[0061] Also, R 3 The divalent linking group represented by has only one secondary hydroxyl group and is located between adjacent PFPE chains. Therefore, R 3 The secondary hydroxyl groups in the compound are less likely to have their binding to active sites on the protective layer inhibited, and instead bind to active sites on the protective layer, improving adhesion to the protective layer. As a result, the lubricating layer containing the fluorine-containing ether compound represented by formula (1) is R 3 The PFPE chains positioned at both ends are prevented from separating too far from the protective layer, resulting in a smoother surface with reduced surface irregularities.

[0062] In formula (4), h and i are integers between 1 and 3, and it is preferable that at least one of h and i is 1. It is preferable that at least one of h and i is 1, as this facilitates the production of fluorine-containing ether compounds. It is more preferable that both h and i are 1 in order to maintain the flexibility of the entire linking group. When z in equation (1) is 2, the two R 3 They may be the same or they may be different. 3When the two R values ​​are the same, the coating state on the protective layer of the fluorine-containing ether compound becomes more uniform, and a lubricating layer with better adhesion can be formed. When z in equation (1) is 2, the two R values ​​are 3 Two Rs are the same if they are 3 The atoms contained are R in the center of the molecule 2 This means that it is arranged symmetrically with respect to it.

[0063] (R 1 (Terminal group indicated by) In formula (1), R 1 The terminal group shown is a branched terminal group with 3 to 35 constituent carbon atoms represented by the following formula (2). The branched terminal group represented by formula (2) is a two-organic group (R) that does not contain a secondary hydroxyl group or a tertiary hydroxyl group but contains one primary hydroxyl group. 5 and R 6 ) is bonded to the trisubstituted carbon atom at the branching point.

[0064] [ka] (In equation (2), R 5 and R 6 x is an organic group that contains one primary hydroxyl group but no secondary or tertiary hydroxyl groups, and may be the same or different. x is an integer between 0 and 3.

[0065] The number of constituent carbon atoms in the branched terminal group represented by formula (2) is 3 to 35, preferably 3 to 20, and more preferably 3 to 12. The number of constituent carbon atoms in the branched terminal group may be 3 to 5, 5 to 10, or 10 to 15. The branched end group represented by formula (2) has 35 or fewer constituent carbon atoms, so the distance between the two primary hydroxyl groups contained in the branched end group is never too far. Therefore, the two primary hydroxyl groups contained in the branched end group represented by formula (2) can easily adopt an orientation that facilitates adsorption to the protective layer and readily binds to the active site on the protective layer. Furthermore, since the branched end group represented by formula (2) has 3 to 35 constituent carbon atoms, the ratio of carbon atoms to the number of hydroxyl groups is appropriate, resulting in a fluorine-containing ether compound with appropriate molecular polarity. In addition, if the branched end group represented by formula (2) has 3 to 12 constituent carbon atoms, the proportion of fluorine atoms in the fluorine-containing ether compound molecule decreases, which can suppress an increase in the overall surface free energy of the molecule.

[0066] In equation (2), x represents an integer from 0 to 3. It is preferable that x be between 1 and 3. In this case, R 2 The interatomic distance between the perfluoropolyether chain shown and the trisubstituted carbon atoms in formula (2) becomes more appropriate. Therefore, R 2 The interatomic distance between the perfluoropolyether chain shown and the two primary hydroxyl groups in formula (2) becomes more appropriate. As a result, both primary hydroxyl groups in formula (2) are less affected by the bulkiness of the adjacent perfluoropolyether chain and are more easily adsorbed onto the protective layer. Consequently, a lubricating layer with even better adhesion to the protective layer and superior wear resistance can be obtained.

[0067] In formula (2), R 5 and R 6 Each of these is an organic group that independently contains no secondary or tertiary hydroxyl groups, contains one primary hydroxyl group, and is bonded to a trisubstituted carbon atom. Therefore, R 5 and R 6 Each of the constituent carbon atoms is 1 or more. 5 and R 6 Each of the organic groups represented by may be linear or branched, but linear is preferred. 5 (or R 6If the organic group represented by ) is a straight chain, then R 5 (or R 6 Compared to the case where the organic group represented by ) has branching, R 5 (or R 6 The primary hydroxyl group of ) can move freely. Therefore, R 5 (or R 6 The primary hydroxyl groups of ) can more easily form bonds with active sites on the protective layer.

[0068] R in equation (2) 5 and R 6 It is preferable that the two primary hydroxyl groups contained in are separated by 5 atoms or more. In other words, R 5 and R 6 Preferably, the oxygen atom of one of the two primary hydroxyl groups contained in is bonded to the oxygen atom of the other primary hydroxyl group via a linking group consisting of five or more atoms, including a trisubstituted carbon atom. In this case, the distance between the two primary hydroxyl groups in formula (2) is sufficiently large, making it less likely for the interaction between the primary hydroxyl groups to become dominant, and more effectively suppressing the inhibition of bonding with the protective layer by adjacent primary hydroxyl groups. Therefore, R 5 and R 6 If the two primary hydroxyl groups contained in are separated by 5 atoms or more, R 5 and R 6 The two primary hydroxyl groups contained in this compound can more easily form bonds with active sites on the protective layer, thereby creating a lubricating layer with even greater smoothness.

[0069] R in equation (2) 5 and / or R 6 The organic group represented by formula (2) preferably contains one or more ether bonds (-O-). In this case, the branched terminal group represented by formula (2) has appropriate flexibility, so that the lubricating layer containing the fluorine-containing ether compound represented by formula (1) has even better adhesion to the protective layer. R in equation (2) 5 (or R 6When the organic group represented by ) has multiple ether bonds, it is preferable that adjacent ether bonds are connected via a linking group to which two or more carbon atoms are linked. In this case, the distance between adjacent ether bonds becomes appropriate, resulting in a fluorine-containing ether compound that is less prone to aggregation.

[0070] Formula (2) is preferably a branched terminal group of either formula (2-1) or (2-2) below. When formula (2) is a branched terminal group of either formula (2-1) or (2-2), the carbon atoms to which the two primary hydroxyl groups in formula (2-1) or (2-2) are bonded are bonded via a linking group selected from a linking group consisting of a methine group, a linking group containing a methine group and a methylene group, or a linking group containing a methine group, a methylene group and an ether bond. For this reason, in the branched terminal group of formula (2-1) or (2-2), the distance between the two primary hydroxyl groups of the branched terminal group is appropriate, and the two primary hydroxyl groups do not inhibit each other from bonding to the active site on the protective layer. Thus, the two primary hydroxyl groups of formula (2-1) or (2-2) can each interact with the protective layer independently.

[0071] Furthermore, if formula (2) is a branched terminal group of either formula (2-1) or (2-2), the number of constituent carbon atoms in the branched terminal group is not too large, and the molecular weight of formula (2-1) or (2-2) does not become too large. Therefore, the proportion of fluorine atoms in the fluorine-containing ether compound molecule does not decrease easily, and the overall surface free energy of the molecule can be suppressed.

[0072] [ka] (In equation (2-1), a is an integer between 1 and 3, and b is an integer between 1 and 4. X 1 X is a hydrogen atom or a group represented by formula (3). 2 X is a base represented by equation (3). 1 and X 2 They may be the same or different. (In equation (2-2), c is an integer between 0 and 3, and d and e are independent integers between 1 and 5. X 3 and X 4 Each of these is independently a hydrogen atom or a group represented by formula (3). 3 and X 4 They may be the same or different. (In equation (3), f is an integer between 2 and 5, and g is either 1 or 2.)

[0073] In equation (2-1), a represents an integer from 1 to 3. Since a in equation (2-1) is an integer from 1 to 3, R 2 The interatomic distance between the perfluoropolyether chain shown and the trisubstituted carbon atom in formula (2-1) is appropriate. As a result, both primary hydroxyl groups in formula (2-1) are less affected by the bulkiness of the adjacent perfluoropolyether chain and are more easily adsorbed onto the protective layer. Consequently, a lubricating layer with even greater wear resistance can be formed. Since a makes it easier to ensure the proportion of fluorine atoms in the fluorine-containing ether compound molecule, a is preferably an integer of 1 or 2, and most preferably 1.

[0074] In equation (2-1), b represents an integer from 1 to 4. 1 When the formula is (3), it is preferable that b is an integer of 1 or 2, as this makes it easier to ensure the proportion of fluorine atoms in the fluorine-containing ether compound molecule. Also, X 1 is a hydrogen atom, X 2 If f in equation (3) is 2 or 3, then b in equation (2-1) is preferably 2 to 4, and more preferably 3 or 4. 1 is a hydrogen atom, X 2When f in formula (3) is 2 or 3, and b in formula (2-1) is 2 or greater, the interatomic distance between the two primary hydroxyl groups in formula (2-1) becomes more appropriate. Therefore, the inhibition of the two primary hydroxyl groups in formula (2-1) from each other's bonding with the active sites on the protective layer can be effectively suppressed. As a result, both primary hydroxyl groups in formula (2-1) become more easily adsorbed by the protective layer, resulting in a lubricating layer with better wear resistance and smoother surface.

[0075] X in equation (2-1) 1 X is a hydrogen atom or a group represented by formula (3). 2 X is a base represented by equation (3). 1 and X 2 They may be the same or they may be different. 1 and X 2 When both and are the same group represented by formula (3), the production of fluorine-containing ether compounds may be easier, which is preferable. 1 and X 2 If they are different, it becomes easier to ensure the proportion of fluorine atoms in the fluorine-containing ether compound molecule, X 1 It is preferable that it is a hydrogen atom.

[0076] In formula (2-2), c represents an integer from 0 to 3. It is preferable that c be an integer from 0 to 2, as this makes it easier to ensure a certain proportion of fluorine atoms in the fluorine-containing ether compound molecule. Also, R 2 The interatomic distance between the perfluoropolyether chain shown and the trisubstituted carbon atoms in formula (2-2) becomes more appropriate, R 2 Since the interatomic distance between the perfluoropolyether chain shown and the two primary hydroxyl groups in formula (2-2) tends to be more appropriate, it is more preferable that c is 1 or 2. In particular, X 3 and X 4 If R is a hydrogen atom, 2Since the interatomic distance between the perfluoropolyether chain shown and the two primary hydroxyl groups in formula (2-2) becomes more appropriate, and a lubricating layer with even greater wear resistance can be formed, it is more preferable for c to be 1 or 2.

[0077] In formula (2-2), d and e each independently represent integers from 1 to 5. d and e are preferably integers from 1 to 3, and more preferably 1 or 2, respectively, as this facilitates ensuring a sufficient proportion of fluorine atoms in the fluorine-containing ether compound molecule. d and e may be the same or different. It is preferable that d and e are the same, as this facilitates the production of the fluorine-containing ether compound. Furthermore, it is preferable that the sum of d and e be 4 or greater, as this ensures an appropriate interatomic distance between the two primary hydroxyl groups in formula (2-2). Also, R 2 In order to achieve a more appropriate interatomic distance between the perfluoropolyether chain shown and the primary hydroxyl group included in formula (2-2), it is preferable that the sum of c and d and the sum of c and e are both 3 or more.

[0078] X in equation (2-2) 3 and X 4 X is a hydrogen atom or a group represented by formula (3). 3 and X 4 It may be the same or different. 3 and X 4 If the two are the same, it is preferable because the production of fluorine-containing ether compounds is easy. 3 and / or X 4 It is preferable that X be a hydrogen atom, as this makes it easier to ensure the proportion of fluorine atoms in the fluorine-containing ether compound molecule. 3 and X 4 It is more preferable that both are hydrogen atoms.

[0079] In equation (3), f represents an integer between 2 and 5. It is preferable that f is an integer between 2 and 4, and more preferably 2 or 3. In equation (3), f is the numerical value of a and b in equation (2-1), and X 1The type, the numerical values ​​of c, d, and e in formula (2-2), etc., are determined appropriately.

[0080] X in equation (2-1) 1 X is a hydrogen atom 2 When the formula is (3), it is preferable that f in formula (3) is 2 or 3. This is because the interatomic distance between the two primary hydroxyl groups in formula (2-1) tends to be more appropriate. X in equation (2-2) 3 and / or X 4 When the formula is (3), it is preferable that f in formula (3) is 2 or 3, as this makes it easier to ensure the proportion of fluorine atoms in the fluorine-containing ether compound molecule.

[0081] In equation (3), g represents either 1 or 2. When g is 2, each [-(CH2) f In [-O-], f may be the same or different. In formula (3), g is preferably 1 because it makes it easier to ensure the proportion of fluorine atoms in the fluorine-containing ether compound molecule.

[0082] (R 4 (Terminal group indicated by) In the fluorine-containing ether compound represented by formula (1), R 4 The terminal groups indicated by are organic groups with 3 to 35 constituent carbon atoms and 1 to 3 polar groups. 4 The terminal group indicated by is preferably an organic group having 3 to 20 constituent carbon atoms, and more preferably an organic group having 3 to 12 constituent carbon atoms. 4 When the number of constituent carbon atoms in the terminal group shown is between 3 and 35, the ratio of carbon atoms to the number of polar groups becomes appropriate, resulting in a fluorine-containing ether compound with appropriate molecular polarity.

[0083] R 4 In the terminal group represented by , it is preferable that the end bonded to the adjacent methylene group is an oxygen atom. In this case, R 4However, by bonding to adjacent methylene groups via ether bonds, it becomes a fluorine-containing ether compound with appropriate hardness. Therefore, the fluorine-containing ether compound applied to the protective layer is less likely to aggregate on the protective layer, and even with a thinner thickness, it is possible to form a lubricating layer with superior coverage and smoothness.

[0084] R 4 Examples of polar groups that the terminal group shown by can be a hydroxyl group (-OH) or an amino group (-NR) 7 R 8 ;R 7 and R 8 Each of these is independently a hydrogen atom or an organic group: ), carboxyl group (-COOH), formyl group (-(C=O)H), carbonyl group (-(C=O)R 9 ;R 9 These are organic groups: a sulfo group (-SO3H), a cyano group (-CN), and a group having an amide bond (-NR). 10 COR 11 or -CONR 12 R 13 ;R 10 , R 11 , R 12 and R 13 Each is independently a hydrogen atom or an organic group. ) are examples. Note that "groups having an amide bond" include both groups that bond to the carbon atom constituting the amide bond (e.g., carboxamide group (-C(=O)NH2)) and groups that bond to 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 10 and R 11 The R 12 and R 13 The R groups may bond to each other to form a ring. 10 , R 11 , R 12 and R 13 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. R 4If the terminal group indicated by has a polar group containing carbon atoms (for example, a carboxyl group, a formyl group, a carbonyl group, a cyano group, or a group having an amide bond), then the carbon atoms included in the polar group are R 4 This shall be included in the number of constituent carbon atoms of the terminal group indicated by [the symbol].

[0085] R 4 The number of polar groups in the terminal group indicated by is 1 to 3, preferably 2 or 3, in order to form a fluorine-containing ether compound that can create a lubricating layer with even better adhesion to the protective layer. When the number of polar groups is 3 or less, it is possible to prevent aggregation of the fluorine-containing ether compound and a decrease in smoothness that can occur in a magnetic recording medium having a lubricating layer containing a fluorine-containing ether compound due to too many polar groups in the fluorine-containing ether compound.

[0086] R 4 When R contains two or more polar groups, it is preferable that the two or more polar groups are bonded to different carbon atoms, with one or more carbon atoms between the carbon atoms to which adjacent polar groups are bonded. In this case, compared to the case where the carbon atoms to which adjacent polar groups are bonded are directly bonded, the adjacent polar groups are bonded with an appropriate interatomic distance. Therefore, R 4 The multiple polar groups present in the material are all oriented in a way that allows them to adhere closely to the protective layer. Therefore, R 4 The multiple polar groups present in this material are less prone to aggregation and can easily form bonds with active sites on the protective layer.

[0087] R 4 The terminal group indicated by may be an organic group having 1 to 3 polar groups and further possessing a carbon-carbon unsaturated bond site. 4 When the terminal group indicated by has a carbon-carbon unsaturated bond site, it is preferable that the terminal group is an organic group having at least one selected from the group consisting of aromatic hydrocarbon groups, unsaturated heterocyclic groups, alkenyl groups, and alkynyl groups.

[0088] Examples of aromatic hydrocarbon groups include phenyl groups, methoxyphenyl groups, phenyl fluoride groups, naphthyl groups, and methoxynaphthyl groups. Aromatic hydrocarbon groups also include groups in which substituents such as methoxy groups and fluoro groups are attached to aromatic hydrocarbons, as described above.

[0089] Examples of unsaturated heterocyclic groups include pyrrolyl, pyrazolyl, methylpyrazolyl, 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. Unsaturated heterocyclic groups also include groups in which substituents such as methyl groups are bonded to an unsaturated heterocycle, as described above.

[0090] Examples of alkenyl groups include vinyl, allyl, butenyl, pentenyl, and hexenyl groups. Examples of alkynyl groups include 1-propynyl, propargyl, butynyl, pentynyl, and hexynyl groups.

[0091] R 4 When the terminal group indicated by has a carbon-carbon unsaturated bond site, the lubricating layer containing the fluorine-containing ether compound exhibits excellent adhesion to the protective layer and can be made thinner, which is preferable. The reason for this is explained below.

[0092] The numerous active sites on the protective layer include locally charged regions and regions where the charge distribution is more widespread. 1 and R 3 The hydroxyl group contained within (and, R 4 (Hydroxyl group when has a hydroxyl group) and R 4The carbon-carbon unsaturated bond sites in the terminal groups indicated by the symbol adsorb to other sites on the protective layer.

[0093] Specifically, R in equation (1) 1 and R 3 The hydroxyl group contained within (and, R 4 When R has a hydroxyl group, the hydroxyl group exhibits adsorption capacity by the hydrogen atom interacting with locally charged sites on the protective layer via hydrogen bonding. On the other hand, R 4 The carbon-carbon unsaturated bond sites in the terminal groups indicated by 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.

[0094] Therefore, R in equation (1) 1 and R 3 The hydroxyl group contained within (and, R 4 (Hydroxyl group when has a hydroxyl group) and R 4 The carbon-carbon unsaturated bond sites in the terminal groups indicated by can independently interact with the active sites on the protective layer. As a result, R 4 A lubricating layer containing a fluorine-containing ether compound, whose terminal group is represented by , has even better adhesion to the protective layer, better smoothness, and higher wear resistance.

[0095] R 4 The terminal group indicated by may contain two primary hydroxyl groups. In this case, R 4 It is preferable that it does not contain polar groups other than the two primary hydroxyl groups. 4 If the molecule contains no polar groups other than two primary hydroxyl groups with high mobility and adsorption, it is possible to prevent the formation of polar groups that cannot be adsorbed to the protective layer and become liberated, due to an excess of polar groups that can participate in adsorption to the protective layer. Therefore, it is possible to prevent aggregation of intermolecular and / or intramolecular polar groups.

[0096] R 4 R 1 Similarly, it may be a branched terminal group represented by formula (2) above. In this case, R4 The two primary hydroxyl groups in formula (2) are R 1 Similar to the two primary hydroxyl groups in formula (2), it readily participates in bonding with active sites present on the protective layer. Also, R 4 If is a branched terminal group represented by formula (2), then R 1 Similarly, it possesses moderate flexibility due to bonding to adjacent methylene groups via ether bonds, and also has sufficient fluidity and flexibility due to the high mobility of the two primary hydroxyl groups contained in the branched terminal group represented by formula (2). Therefore, it is presumed that a lubricating layer containing the fluorine-containing ether compound represented by formula (1) will have good adhesion to the protective layer, good smoothness, and excellent wear resistance.

[0097] R 4 If is a branched terminal group represented by formula (2), then R 4 It is preferable that is a branched terminal group of either formula (2-1) or (2-2). In this case, the preferred values ​​of a and b in formula (2-1), c to e in formula (2-2), and f and g in formula (3) are R 1 This is the same as when it is a branched terminal group of either formula (2-1) or (2-2).

[0098] In equation (1), R 4 If is a branched terminal group represented by formula (2), then R 1 and R 4 It is even more preferable that both of them are branched terminal groups of either formula (2-1) or (2-2). In equation (1), R 4 If is a branched terminal group represented by formula (2), then R 1 and R 4 It is preferable that they are the same, R 1 and R 4 It is even more preferable that both of them are the above formula (2-1) or (2-2). 1 and R 4 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.

[0099] In the fluorine-containing ether compound represented by formula (1), z is 1, and R 1 and R 4 and are the same, and the two R 2 It is preferable that the two components are the same, as this results in a fluorine-containing ether compound that is easy to synthesize. Furthermore, fluorine-containing ether compounds with a symmetrical structure spread more easily on the protective layer, forming a lubricating layer with good coverage.

[0100] In the fluorine-containing ether compound represented by formula (1), z is 2, and R 1 and R 4 The three R's are the same. 2 It is preferable that the two Rs are the same, as this results in an easily synthesized fluorine-containing ether compound. Furthermore, if z is 2, then the two Rs 3 It is preferable that the two components are the same, as this makes the fluorine-containing ether compound easier to synthesize. Furthermore, fluorine-containing ether compounds with a symmetrical structure spread more easily on the protective layer, forming a lubricating layer with good coverage.

[0101] R 4 If is not a terminal group represented by formula (2), R 4 The terminal group represented by preferably contains two or three polar groups, and at least one of the polar groups is a secondary hydroxyl group. 4 If is not a terminal group represented by formula (2), R 4 The terminal group represented by is preferably one of the terminal groups shown in formulas (6-1) to (6-3) below.

[0102] [ka] (In equation (6-1), y1 is 1 or 2, and y2 is an integer from 0 to 3. X 5 is an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, an alkynyl group, or a polar group. When y1 is 1, X 5 X is a polar group. 5If X is an aromatic hydrocarbon group or an unsaturated heterocyclic group, 5 The atoms that make up the ring structure inside are X 5 It bonds to the adjacent methylene group. 5 If X is an alkenyl group or an alkynyl group, 5 The carbon atoms that make up the unsaturated bond inside are X 5 It bonds to the adjacent methylene group. (In equation (6-2), y3 is an integer between 1 and 3, y4 is 0 or 1, and y5 is an integer between 0 and 3. X 5 is an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, an alkynyl group, or a polar group. When y4 is 0, X 5 X is a polar group. 5 If X is an aromatic hydrocarbon group or an unsaturated heterocyclic group, 5 The atoms that make up the ring structure inside are X 5 It bonds to the adjacent methylene group. 5 If X is an alkenyl group or an alkynyl group, 5 The carbon atoms that make up the unsaturated bond inside are X 5 It bonds to the adjacent methylene group. (In equation (6-3), y6 is 0 or 1, y7 is an integer from 1 to 3, and y8 is an integer from 1 to 3. X 5 is an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, an alkynyl group, or a polar group. When y6 is 0, X 5 X is a polar group. 5 If X is an aromatic hydrocarbon group or an unsaturated heterocyclic group, 5 The atoms that make up the ring structure inside are X 5 It bonds to the adjacent methylene group. 5 If X is an alkenyl group or an alkynyl group, 5 The carbon atoms that make up the unsaturated bond inside are X 5 It bonds to the adjacent methylene group.

[0103] In equations (6-1) to (6-3), X 5 If X is an aromatic hydrocarbon group, 5 The atoms that make up the ring structure inside are X5 It bonds to the adjacent methylene group. 5 If X is an aromatic hydrocarbon group, 5 As examples, the aromatic hydrocarbon groups exemplified above can be used. In equations (6-1) to (6-3), X 5 If X is an unsaturated heterocyclic group, 5 The atoms that make up the ring structure inside are X 5 It bonds to the adjacent methylene group. 5 If X is an unsaturated heterocyclic group, 5 As an example, the unsaturated heterocyclic groups exemplified above can be used.

[0104] In equations (6-1) to (6-3), X 5 If X is an alkenyl group, 5 The carbon atoms that make up the unsaturated bond inside are X 5 It bonds to the adjacent methylene group. 5 If X is an alkenyl group, 5 For example, -CH=CH2, -CH=CHR 14 (R 14 It is an organic group. ), -CR 15 =CHR 16 (R 15 , R 16 It is an organic group. ), -CR 17 =CR 18 R 19 (R 17 , R 18 , R 19 R is an organic group. 14 ~R 19 The organic groups represented by are preferably hydrocarbon groups having 1 to 3 carbon atoms. X in formulas (6-1) to (6-3) 5 If X is an alkenyl group, 5 It is preferable that -CH=CH2. -CH=CH2 has an appropriate bulk. Therefore, X 5 A lubricating layer containing a fluorine-containing ether compound having a terminal group of -CH=CH2 tends to have a low bulkiness of the fluorine-containing ether compound on the protective layer, resulting in good smoothness.

[0105] In equations (6-1) to (6-3), X 5 If X is an alkynyl group, 5 The carbon atoms that make up the unsaturated bond inside are X 5 It bonds to the adjacent methylene group. 5 If X is an alkynyl group, 5 For example, -C≡CH, -C≡CR 20 (R 20 R is an organic group. 20 The organic group represented by is preferably a hydrocarbon group having 1 to 3 carbon atoms. X in formulas (6-1) to (6-3) 5 If it is an alkynyl group, it will be a terminal group with an appropriate bulk, so X 5 It is preferable that -C≡CH.

[0106] In equations (6-1) to (6-3), X 5 If X is a polar group, 5 The polar groups exemplified above can be used as such. Among these polar groups, X 5 It is preferable that the group is a hydroxyl group, a group having an amide bond, or a cyano group. 5 When the group is a hydroxyl group, a group having an amide bond, or a cyano group, a more favorable interaction occurs between the lubricating layer and the protective layer when a lubricating layer is formed on the protective layer using a lubricant containing the group. X in equations (6-1) to (6-3) 5 When the group is polar, a lubricating layer containing a 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.

[0107] In formulas (6-1) to (6-3), the secondary hydroxyl group and X in formulas (6-1) to (6-3) 5 This means that the bond is mediated through a divalent organic group which may contain an ether bond. Therefore, X 5 Even if it is a polar group, the secondary hydroxyl group and X in formulas (6-1) to (6-3) 5The distance to the polar group represented by becomes appropriate. As a result, the secondary hydroxyl group in formulas (6-1) to (6-3), and X 5 The polar group represented by is less likely to have its binding to the active site on the protective layer inhibited by other polar groups. Also, the secondary hydroxyl group and X in formulas (6-1) to (6-3) 5 Polar groups represented by this symbol are less likely to aggregate.

[0108] Therefore, the secondary hydroxyl group in formulas (6-1) to (6-3), and X 5 The polar groups represented by can each be independently adsorbed to active sites on the protective layer. As a result, X in equations (6-1) to (6-3) 5 A lubricating layer containing a fluorine-containing ether compound having a polar terminal group exhibits even better adhesion to the protective layer, good smoothness, and excellent wear resistance even at a thin thickness.

[0109] Among the above, X in equations (6-1) to (6-3) 5 Preferably, the group is a hydroxyl group, a group having an amide bond, a cyano group, or -CH=CH2. This is because it results in a fluorine-containing ether compound that can form a lubricating layer with higher coverage, smoothness, and better wear resistance.

[0110] In the terminal group represented by equation (6-1), y1 is 1 or 2, and y2 is an integer from 0 to 3. When y1 is 1, X 5 is a polar group, and formula (6-1) has two polar groups. In this case, because formula (6-1) has two polar groups, it can form a lubricating layer with good adhesion to the protective layer. When y1 is 2, X 5 y1 is 2 and X 5 Even if is an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, or an alkynyl group, formula (6-1) has two polar groups. Therefore, a lubricating layer with good adhesion to the protective layer can be formed. In addition, X 5Since is an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, or an alkynyl group, X can be formed without impairing the adhesion of the two hydroxyl groups in formula (6-1) to the protective layer. 5 The π-π interaction between the carbon-carbon unsaturated bond sites and the protective layer allows for the formation of a lubricating layer with excellent smoothness and wear resistance. Also, when y1 is 2 and X 5 If is a polar group, then formula (6-1) will have three polar groups. Therefore, a lubricating layer that exhibits better adhesion to the protective layer can be formed.

[0111] In the terminal group represented by equation (6-1), y2 is an integer between 0 and 3. In the terminal group represented by equation (6-1), X in equation (6-1) 5 Even if X is a polar group, 5 Because the distance between X in formula (6-1) and the secondary hydroxyl group is not too close, the polar group in formula (6-1) is less likely to aggregate. 5 If X is a polar group, 5 Since the distance between the secondary hydroxyl group in formula (6-1) becomes more appropriate, it is preferable that y2 be 1 or greater. In the terminal group represented by formula (6-1), since y2 is 3 or less, X in formula (6-1) 5 The mobility of the terminal groups does not become excessively high, and each polar group of the terminal group can adhere sufficiently to the protective layer. It is more preferable that y2 is 2 or less.

[0112] In the terminal base represented by equation (6-2), y3 is an integer from 1 to 3. When y4 is 0, X 5 It is a polar group. Since y3 is an integer greater than or equal to 1, when y4 is 0, X 5 The distance to the secondary hydroxyl group in equation (6-2) becomes appropriate, and X 5Even if the group is a polar group, the polar groups in formula (6-2) are less likely to aggregate. Also, since y3 is an integer of 1 or more, when y4 is 1, the distance between the secondary hydroxyl groups in formula (6-2) does not become too close, and the secondary hydroxyl groups in formula (6-2) are less likely to aggregate. In the terminal group represented by formula (6-2), since y3 is 3 or less, the mobility of the terminal group represented by formula (6-2) does not become too high, and each polar group of the terminal group can adhere sufficiently to the protective layer. It is preferable that y3 is 2 or less.

[0113] In the terminal group represented by formula (6-2), y4 is either 0 or 1. When y4 is 0, X 5 is a polar group, and formula (6-2) has two polar groups. In this case, because formula (6-2) has two polar groups, it can form a lubricating layer with good adhesion to the protective layer. When y4 is 1, X 5 y4 is 1 and X 5 Even if is an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, or an alkynyl group, formula (6-2) has two polar groups. Therefore, a lubricating layer with good adhesion to the protective layer can be formed. In addition, X 5 Since is an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, or an alkynyl group, X can be formed without impairing the adhesion of the two hydroxyl groups in formula (6-2) to the protective layer. 5 The π-π interaction between the carbon-carbon unsaturated bond sites and the protective layer allows for the formation of a lubricating layer with excellent smoothness and wear resistance. Also, when y4 is 1 and X 5 If is a polar group, then formula (6-2) will have three polar groups. Therefore, a lubricating layer can be formed that exhibits excellent adhesion to the protective layer.

[0114] In the terminal group represented by equation (6-2), y5 is an integer from 0 to 3. In the terminal group represented by equation (6-2), X in equation (6-2) 5 Even if X is a polar group, 5Because the distance between X in formula (6-2) and the secondary hydroxyl group is not too close, the polar group in formula (6-2) is less likely to aggregate. 5 If X is a polar group, 5 Since the distance to the secondary hydroxyl group in formula (6-2) becomes more appropriate, it is preferable that y5 be 1 or more. Also, if y4 is 0, even if y5 is 0, the three methylene groups of y make the polar group X 5 The distance to the secondary hydroxyl group in equation (6-2) is appropriate. When y4 is 0, and y5 is 1 or more, the polar group X is formed by y3 + y5 methylene groups. 5 This is preferable because the distance to the secondary hydroxyl group in formula (6-2) becomes more appropriate. In the terminal group represented by formula (6-2), since y5 is 3 or less, X in formula (6-2) 5 The mobility of the terminal groups is not excessively high, and each polar group of the terminal group can adhere sufficiently to the protective layer. It is preferable that y5 is 2 or less.

[0115] In the terminal group represented by formula (6-3), y6 is either 0 or 1. When y6 is 0, X 5 is a polar group, and formula (6-3) has two polar groups. In this case, because formula (6-3) has two polar groups, it can form a lubricating layer with good adhesion to the protective layer. When y6 is 1, X 5 y6 is 1 and X 5 Even when is an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, or an alkynyl group, formula (6-3) has two polar groups. Therefore, a lubricating layer with good adhesion to the protective layer can be formed. In addition, X 5 Since is an aromatic hydrocarbon group, an unsaturated heterocyclic group, an alkenyl group, or an alkynyl group, X can be formed without impairing the adhesion of the two hydroxyl groups in formula (6-3) to the protective layer. 5 The π-π interaction between the carbon-carbon unsaturated bond sites and the protective layer allows for the formation of a lubricating layer with excellent smoothness and wear resistance. Also, when y6 is 1 and X 5If is a polar group, then formula (6-3) will have three polar groups. Therefore, a lubricating layer can be formed that exhibits excellent adhesion to the protective layer.

[0116] In the terminal group represented by formula (6-3), y7 is an integer between 1 and 3. Since y7 is 1 or greater, when y6 is 1, the distance between the secondary hydroxyl groups in formula (6-3) does not become too close. Therefore, the secondary hydroxyl groups in formula (6-3) are less likely to aggregate. In the terminal group represented by formula (6-3), since y7 is 3 or less, the mobility of the terminal group represented by formula (6-3) does not become too high, and each polar group of the terminal group can adhere sufficiently to the protective layer. It is preferable that y7 is 2 or less.

[0117] In the terminal group represented by equation (6-3), y8 is an integer from 1 to 3. In the terminal group represented by equation (6-3), y8 is 1 or greater, so X in equation (6-3) 5 Even if X is a polar group, 5 The distance between the X in formula (6-3) and the secondary hydroxyl group does not become too close. Therefore, the polar group in formula (6-3) is less likely to aggregate. 5 If X is a polar group, 5 Since the distance between the secondary hydroxyl group in formula (6-3) becomes more appropriate, it is preferable that y8 is 2 or more. In the terminal group represented by formula (6-3), since y8 is 3 or less, X in formula (6-3) 5 The mobility of the terminal groups does not become excessively high, and each polar group of the terminal group can adhere sufficiently to the protective layer.

[0118] In the fluorine-containing ether compound represented by formula (1), R 1 and R 4 The type of terminal group indicated can be appropriately selected according to the performance requirements of the lubricant containing the fluorine-containing ether compound.

[0119] The fluorine-containing ether compound represented by (1) is preferably one of the compounds represented by the following formulas (1A) to (1O) and (2A) to (2O). When the compound represented by formula (1) is one of the compounds represented by the following formulas (1A) to (1O) and (2A) to (2O), the raw materials are readily available, and even with a thin thickness, it is possible to form a lubricating layer with excellent adhesion, smoothness, and wear resistance.

[0120] The compounds represented by the following formulas (1A) to (1O) and (2A) to (2O) all contain R in formula (1). 1 and R 4 The same as the group represented by formula (2-1) or (2-2), R 3 In equation (4), h and i are 1.

[0121] The compounds represented by the following formulas (1A) to (1O) and (2A) to (2O) all contain R in formula (1). 2 The (z+1) PFPE chains shown are all identical. In the compounds represented by the following formulas (1A)~(1O) and (2A)~(2O), Rf1 and Rf2, representing the PFPE chain, have the following structures, respectively. That is, in the compounds represented by the following formulas (1A)~(1F), (1J), (1K), (1N), (2A)~(2F), (2J), (2K), (2N), Rf2 is the PFPE chain represented by the following formula (7-2). In the compounds represented by the following formulas (1G)~(1I), (1L), (1M), (1O), (2G)~(2I), (2L), (2M), (2O), Rf1 is the PFPE chain represented by the following formula (7-1). Note that the values ​​of p and q in Rf1 and r in Rf2 representing the PFPE chain in equations (1A) to (1O) and (2A) to (2O) are values ​​that indicate the average degree of polymerization and are therefore not necessarily integers.

[0122] [ka]

[0123] [ka] (In equation (1A), in the two Rf2 terms, r represents the average degree of polymerization and is expressed as 1 to 15. The r in the two Rf2 terms may be the same or different.) (In equation (1B), in the two Rf2 terms, r represents the average degree of polymerization and ranges from 1 to 15. The r in the two Rf2 terms may be the same or different.) (In equation (1C), in the two Rf2 terms, r represents the average degree of polymerization and is expressed as 1 to 15. The r in the two Rf2 terms may be the same or different.) (In equation (1D), in the two Rf2 terms, r represents the average degree of polymerization and is expressed as 1 to 15. The r in the two Rf2 terms may be the same or different.) (In equation (1E), in the two Rf2 terms, r represents the average degree of polymerization and ranges from 1 to 15. The r in the two Rf2 terms may be the same or different.)

[0124] [ka] (In equation (1F), in the two Rf2 terms, r represents the average degree of polymerization and is expressed as 1 to 15. The r in the two Rf2 terms may be the same or different.) (In equation (1G), p and q represent the average degree of polymerization in the two Rf1 values, where p is between 1 and 20, and q is between 0 and 20. The p and q values ​​in the two Rf1 values ​​may be the same or different.) (In equation (1H), p and q represent the average degree of polymerization in the two Rf1 terms, where p is between 1 and 20, and q is between 0 and 20. The p and q in the two Rf1 terms may be the same or different.) (In equation (1I), p and q represent the average degree of polymerization in the two Rf1 terms, where p is between 1 and 20, and q is between 0 and 20. The p and q in the two Rf1 terms may be the same or different.) (In equation (1J), in the two Rf2 terms, r represents the average degree of polymerization and is expressed as 1 to 15. The r in the two Rf2 terms may be the same or different.)

[0125] [ka] (In equation (1K), in the two Rf2 terms, r represents the average degree of polymerization and is expressed as 1 to 15. The r in the two Rf2 terms may be the same or different.) (In the two Rf1 equations (1L), p and q represent the average degree of polymerization, where p is between 1 and 20, and q is between 0 and 20. The p and q in the two Rf1 equations may be the same or different.) (In equation (1M), p and q represent the average degree of polymerization in the two Rf1 terms, where p is between 1 and 20, and q is between 0 and 20. The p and q in the two Rf1 terms may be the same or different.) (In equation (1N), in the two Rf2 terms, r represents the average degree of polymerization and ranges from 1 to 15. The r in the two Rf2 terms may be the same or different.) (In the two Rf1 equations (1O), p and q represent the average degree of polymerization, where p is between 1 and 20, and q is between 0 and 20. The p and q in the two Rf1 equations may be the same or different.)

[0126] [ka] (In equation (2A), in the three Rf2 terms, r represents the average degree of polymerization and ranges from 1 to 15. The r values ​​in the three Rf2 terms may be different, or some or all of them may be the same.) (In equation (2B), in the three Rf2 terms, r represents the average degree of polymerization and ranges from 1 to 15. The r values ​​in the three Rf2 terms may be different, or some or all of them may be the same.) (In equation (2C), in the three Rf2 terms, r represents the average degree of polymerization and ranges from 1 to 15. The r values ​​in the three Rf2 terms may be different, or some or all of them may be the same.) (In equation (2D), in the three Rf2 terms, r represents the average degree of polymerization and ranges from 1 to 15. The r values ​​in the three Rf2 terms may be different, or some or all of them may be the same.) (In equation (2E), in the three Rf2 terms, r represents the average degree of polymerization and ranges from 1 to 15. The r values ​​in the three Rf2 terms may be different, or some or all of them may be the same.)

[0127] [ka] (In equation (2F), in the three Rf2 terms, r represents the average degree of polymerization and ranges from 1 to 15. The r values ​​in the three Rf2 terms may be different, or some or all of them may be the same.) (In equation (2G), p and q represent the average degree of polymerization in the three Rf1 values, where p ranges from 1 to 20 and q ranges from 0 to 20. The p and q values ​​in the three Rf1 values ​​may be different, or they may be partially or entirely the same.) (In equation (2H), p and q represent the average degree of polymerization in the three Rf1 terms, where p ranges from 1 to 20 and q ranges from 0 to 20. The p and q values ​​in the three Rf1 terms may be different, or they may be partially or entirely the same.) (In equation (2I), p and q represent the average degree of polymerization in the three Rf1 values, where p ranges from 1 to 20 and q ranges from 0 to 20. The p and q values ​​in the three Rf1 values ​​may be different, or they may be partially or entirely the same.) (In equation (2J), in the three Rf2 terms, r represents the average degree of polymerization and ranges from 1 to 15. The r values ​​in the three Rf2 terms may be different, or some or all of them may be the same.)

[0128] [ka] (In equation (2K), in the three Rf2 terms, r represents the average degree of polymerization and ranges from 1 to 15. The r values ​​in the three Rf2 terms may be different, or some or all of them may be the same.) (In the three Rf1 values ​​in equation (2L), p and q represent the average degree of polymerization, where p ranges from 1 to 20 and q ranges from 0 to 20. The p and q values ​​in the three Rf1 values ​​may be different, or they may be partially or entirely the same.) (In equation (2M), p and q represent the average degree of polymerization in the three Rf1 values, where p ranges from 1 to 20 and q ranges from 0 to 20. The p and q values ​​in the three Rf1 values ​​may be different, or they may be partially or entirely the same.) (In equation (2N), in the three Rf2 terms, r represents the average degree of polymerization and ranges from 1 to 15. The r values ​​in the three Rf2 terms may be different, or some or all of them may be the same.) (In the three Rf1 values ​​in formula (2O), p and q represent the average degree of polymerization, where p ranges from 1 to 20 and q ranges from 0 to 20. The p and q values ​​in the three Rf1 values ​​may be different, or they may be partially or entirely the same.)

[0129] The fluorine-containing ether compound in this embodiment preferably has a number-average molecular weight (Mn) in the range of 500 to 10000, more preferably in the range of 500 to 5000, and particularly preferably in the range of 1000 to 3000. When the number-average molecular weight is 500 or more, the lubricant containing the fluorine-containing ether compound in this embodiment is less likely to evaporate, preventing the lubricant from evaporating and transferring to the magnetic head. When the number-average molecular weight is 10000 or less, the viscosity of the fluorine-containing ether compound becomes appropriate, and a thin lubricating layer can be easily formed by applying a lubricant containing it. When the number-average molecular weight is 5000 or less, the viscosity becomes easier to handle when applied to a lubricant, which is therefore more preferable.

[0130] The number-average molecular weight (Mn) of fluorine-containing ether compounds was determined using a Bruker BioSpin AVANCE III 400. 1 H-NMR and19 These values ​​were measured by F-NMR. Specifically, 19 The number of repeating units in the PFPE chain was calculated from the integrated values ​​measured by 1F-NMR, and the number-average molecular weight was determined. For the NMR (nuclear magnetic resonance) measurements, the sample was diluted in one or a mixture of solvents such as hexafluorobenzene, d-acetone, and d-tetrahydrofuran before being used for the measurement. 19 The reference point for the F-NMR chemical shift was set to the hexafluorobenzene peak at -164.7 ppm. 1 The 1H-NMR chemical shift reference was set to a peak of 2.2 ppm for acetone.

[0131] 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.

[0132] "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 the production method shown below.

[0133] Specifically, when producing a fluorine-containing ether compound in formula (1) where z is 1, one of the following production methods (1) to (4) can be used. When producing a fluorine-containing ether compound in formula (1) where z is 2, one of the following production methods (5) and (6) can be used.

[0134] <First manufacturing method> In equation (1), z is 1, and R 1 and R 4The two are the same and are the base shown by equation (2-1) where a is 1 and X 1 is a hydrogen atom, and R 2 The two PFPE chains shown are the same, and R 3 When producing a fluorine-containing ether compound in formula (4) where h and i are 1, the production method shown in formula (8) below can be used.

[0135] [ka] (In formula (8), R 2 R in equation (1) 2 It is the same as PG1, PG2, and PG3 each represent protecting groups and may be the same or different. X represents a (pseudo)halogen group. s, which represents the number of methylene groups, is the integer corresponding to b in equation (2-1). t, which represents the number of methylene groups, is the same as X in equation (2-1). 2 (This is the integer corresponding to f in equation (3).)

[0136] (First reaction) R in equation (1) 2 A fluorine-based compound having hydroxymethyl groups (-CH2OH) at both ends of the corresponding PFPE chain is prepared. The first intermediate compound is produced by attaching an appropriate protecting group (PG1) to the hydroxymethyl group at one end of the fluorine-based compound.

[0137] (Second reaction) Next, a second intermediate compound is produced by reacting the hydroxymethyl group (-CH2OH) in the first intermediate compound obtained by the first reaction, which is not bound to a protecting group (PG1), with an epoxy compound having a hydroxyl group protected by a protecting group (PG2).

[0138] The epoxy compound used in the second reaction is the -(CH2) group shown in formula (2-1). a -CH(OX 2 )-(CH2) b -OX 1It has a corresponding group. Specifically, as shown in formula (8), the -(CH2) of the group shown in formula (2-1) a -CH(OX 2 )-(CH2) b -OX 1 In X, a is 1, b is s, and X 1 An epoxy compound corresponding to one in which the atom is a hydrogen atom is used. Such an epoxy compound may be manufactured by known methods or a commercially available product may be used.

[0139] (Third reaction) Next, in the second intermediate compound obtained by the second reaction, the (pseudo)alkyl halide (X-(CH2)) has a hydroxyl group protected with a protecting group (PG3) to the secondary hydroxyl group. t The -O-PG3) is reacted. Subsequently, the protecting groups PG1, PG2, and PG3 contained in the resulting compound are deprotected under appropriate conditions, and R 2 R at one end of the PFPE chain corresponding to 1 (=R 4 A third intermediate compound having a terminal group equivalent to ) is produced.

[0140] The (pseudo)alkyl halide compound (X-(CH2) used in the third reaction t -O-PG3) is the -OX group represented by formula (2-1). 2 (X 2 It has a group corresponding to the group represented by formula (3). Specifically, as shown in formula (8), it has a group corresponding to the group represented by formula (3) (-((CH2) f -O) g A (pseudo)alkyl halide compound is used that corresponds to the one in -H where f is t and g is 1. Such a (pseudo)alkyl halide compound may be produced by known methods or a commercially available product may be used.

[0141] (Fourth reaction) Finally, R, which is contained in the third intermediate compound 2 The hydroxymethyl group (-CH2OH) located at the terminal end of the PFPE chain corresponding to the linking group R 3A (pseudo)halogenated epoxy compound having a substructure corresponding to the above is reacted. In the first production method, it is preferable that the reaction ratio of the third intermediate compound to the (pseudo)halogenated epoxy compound be about 2:1 (molar ratio).

[0142] The (pseudo)halogenated epoxy compound used in the fourth reaction is the group represented by formula (4) (-O(CH2) h -CH(OH)-(CH2) i It has a group corresponding to O-. Specifically, as shown in formula (8), it has the group (-O(CH2) shown in formula (4). h -CH(OH)-(CH2) i A (pseudo)halogenated epoxy compound is used that corresponds to those in O- where h and i are 1. Such a (pseudo)halogenated epoxy compound may be prepared by known methods or a commercially available product may be used.

[0143] By performing the above steps, z in equation (1) is 1, and R 1 and R 4 The two are the same and are the base shown by equation (2-1) where a is 1 and X 1 is a hydrogen atom, and R 2 The two PFPE chains shown are the same, and R 3 A fluorine-containing ether compound can be produced in formula (4) where h and i are 1.

[0144] In the first manufacturing method described above, the example given was that all protecting groups PG1, PG2, and PG3 contained in the compound are deprotected in the third reaction. However, it is also possible to deprotect only the protecting group PG1 in the third reaction, and then deprotect the protecting groups PG2 and PG3 under appropriate conditions after the fourth reaction.

[0145] Furthermore, in the first manufacturing method described above, the epoxy compound used in the second reaction is one in which a in the group represented by formula (2-1) is 1 and X 1 The example given was the case where an epoxy compound corresponding to a hydrogen atom is used, but X 1An epoxy compound corresponding to a group represented by formula (3) may also be used. 1 The epoxy compounds corresponding to those in which the group is represented by formula (3) may be manufactured by known methods or commercially available products may be used.

[0146] Furthermore, in the first manufacturing method described above, the (pseudo)alkyl halide compound (X-(CH2) used in the third reaction t -O-PG3) represents the group (-((CH2) shown in formula (3) f -O) g The explanation has been given using the example of using a (pseudo)alkyl halide compound corresponding to one in -H where f is t and g is 1, but a (pseudo)alkyl halide compound corresponding to one in the group shown in formula (3) where g is 2 may also be used. The (pseudo)alkyl halide compound corresponding to one in the group shown in formula (3) where g is 2 may be produced by known methods, or a commercially available product may be used.

[0147] <Second manufacturing method> In equation (1), z is 1, and R 1 and R 4 and are the same, R 2 The two PFPE chains shown are the same, and R 3 When producing a fluorine-containing ether compound in formula (4) where h and i are 1, the method represented by the following formula (9) may be used.

[0148] [ka] (In formula (9), R 2 R in equation (1) 2 It is the same as PG4, which represents a protecting group. LG represents a leaving group obtained by reacting a hydroxyl group with an activator. R is R in formula (1). 1 (=R 4 ) of -(CH2) x -CH(R 5 )R 6 This shows an organic group having a substructure corresponding to [X]. (X represents a (pseudo)halogen group.)

[0149] (First reaction) Similar to the first reaction in the first manufacturing method described above, R in equation (1) 2 A first intermediate compound is produced in which a protecting group (PG4) is attached to one end of the corresponding PFPE chain.

[0150] (Second reaction) Next, a known activator is reacted with the hydroxymethyl group at one end of the first intermediate compound obtained by the first reaction to convert the end opposite the protecting group (PG4) of the first intermediate compound to a leaving group (LG) and produce a second intermediate compound. Examples of the aforementioned leaving groups (LG) include chloro groups, bromo groups, iodine groups, p-toluenesulfonyloxy groups, methanesulfonyloxy groups, trifluoromethanesulfonyloxy groups, perfluoroalkylsulfonyloxy groups, and nitrobenzenesulfonyloxy groups.

[0151] (Third reaction) Next, R is applied to the leaving group (LG) of the second intermediate compound obtained by the second reaction. 1 (=R 4 ) of -(CH2) x -CH(R 5 )R 6 After reacting an alcohol compound (R-OH) containing the corresponding substructure to link the terminal group moieties, the protecting group (PG4) is deprotected by an appropriate method. As a result, R 2 At one end of the PFPE chain corresponding to R 1 (=R 4 ) of -(CH2) x -CH(R 5 )R 6 A third intermediate compound having a corresponding terminal group is prepared. The alcohol compound used in the third reaction may be prepared by known methods or a commercially available product may be used.

[0152] (Fourth reaction) Finally, R, which is contained in the third intermediate compound 2The hydroxymethyl group (-CH2OH) located at the terminal end of the PFPE chain corresponding to the linking group R 3 A (pseudo)halogenated epoxy compound having a substructure corresponding to the above is reacted. In the second production method, the reaction ratio of the third intermediate compound to the (pseudo)halogenated epoxy compound is preferably about 2:1 (molar ratio). As the (pseudo)halogenated epoxy compound used in the fourth reaction, the same compound that can be used in the fourth reaction of the first manufacturing method can be used.

[0153] By performing the above steps, z in equation (1) is 1, and R 1 and R 4 and are the same, R 2 The two PFPE chains shown are the same, and R 3 A fluorine-containing ether compound is obtained in formula (4) where h and i are 1.

[0154] The third reaction of the second manufacturing method described above uses R 1 (=R 4 ) of -(CH2) x -CH(R 5 )R 6 Among the polar groups contained in the alcohol compound having a corresponding substructure, those polar groups that do not participate in bonding with the second intermediate compound in the third reaction may be protected with an appropriate protecting group before being used in the third reaction. In that case, the protecting group of the polar group can be deprotected under appropriate conditions after the third reaction or after the fourth reaction.

[0155] <Third manufacturing method> In equation (1), z is 1, and R 1 and R 4 and are the same, R 2 The two PFPE chains shown are the same, and R 3 When producing a fluorine-containing ether compound in formula (4) where h and i are 1, the method represented by the following formula (10) may be used.

[0156] [ka] (In formula (10), R 2 R in equation (1) 2 It is the same as. X represents a (pseudo)halogen group. R' is R in formula (1). 1 (=R 4 ) of -(CH2) x -CH(R 5 )R 6 (This shows an organic group having a substructure corresponding to [the specified substructure].)

[0157] (First reaction) R in equation (1) 2 Prepare a fluorine-based compound having hydroxymethyl groups (-CH2OH) at both ends of the corresponding PFPE chain. R 1 (=R 4 ) of -(CH2) x -CH(R 5 )R 6 A (pseudo)alkyl halide compound (X-R') containing a corresponding substructure is reacted to link the terminal group moieties. This results in R 2 At one end of the PFPE chain corresponding to R 1 (=R 4 ) of -(CH2) x -CH(R 5 )R 6 A first intermediate compound having a terminal group corresponding to R is produced. 1 (=R 4 ) of -(CH2) x -CH(R 5 )R 6 (Pseudo)alkyl halogen compounds containing the corresponding substructure may be produced by known methods or commercially available products may be used.

[0158] (Second reaction) Next, R, which is contained in the first intermediate compound 2 The hydroxymethyl group (-CH2OH) located at the terminal end of the PFPE chain corresponding to the linking group R 3A (pseudo)halogenated epoxy compound having a substructure corresponding to the above is reacted. In the third production method, the reaction ratio of the first intermediate compound to the (pseudo)halogenated epoxy compound is preferably about 2:1 (molar ratio). As the (pseudo)halogenated epoxy compound used in the second reaction, the same compound that can be used in the fourth reaction of the first manufacturing method can be used.

[0159] By performing the above steps, z in equation (1) is 1, and R 1 and R 4 and are the same, R 2 The two PFPE chains shown are the same, and R 3 A fluorine-containing ether compound is obtained in formula (4) where h and i are 1.

[0160] The R used in the first reaction of the third manufacturing method described above 1 (=R 4 ) of -(CH2) x -CH(R 5 )R 6 Polar groups contained in a (pseudo)alkyl halide compound that includes a substructure corresponding to the above may be protected with an appropriate protecting group before being used in the first reaction if they do not participate in bonding with the fluorine-based compound in the first reaction. In this case, the protecting group of the polar group can be deprotected under appropriate conditions after the first or second reaction.

[0161] In the fourth reaction of the first manufacturing method, the fourth reaction of the second manufacturing method, and the second reaction of the third manufacturing method described above, the (pseudo)halogenated epoxy compound is the group represented by formula (4) (-O(CH2) h -CH(OH)-(CH2) iAlthough the example given was the use of a (pseudo)halogenated epoxy compound corresponding to those in formula (O-) where h and i are 1, a (pseudo)halogenated epoxy compound or (pseudo)halogenated alkyl compound corresponding to those in the group represented by formula (4) where h and / or i are 2 or 3 may also be used. A (pseudo)halogenated epoxy compound or (pseudo)halogenated alkyl compound corresponding to those in the group represented by formula (4) where h and / or i are 2 or 3 can be produced by known methods.

[0162] <4th manufacturing method> In equation (1), z is 1, and R 1 and R 4 The terminal group indicated by, or R 2 When producing a fluorine-containing ether compound in which one or more of the two PFPE chains shown are different, the following production method can be used.

[0163] (First reaction) In the same manner as described in the first to third manufacturing methods above, R 1 R on the side 2 At one end of the PFPE chain corresponding to R 1 A first intermediate compound having a terminal group corresponding to the above is produced.

[0164] (Second reaction) Next, R, which is contained in the first intermediate compound 1 R on the side 2 The hydroxymethyl group (-CH2OH) located at the terminal end of the PFPE chain corresponding to the linking group R 3 A (pseudo)halogenated epoxy compound having a substructure corresponding to the above is reacted. In the fourth production method, the reaction ratio of the first intermediate compound to the (pseudo)halogenated epoxy compound is preferably about 1:1 (molar ratio). This allows R 1 R on the side 2 At one end of the PFPE chain corresponding to, R 1 It has a terminal group corresponding to and the other terminal has a linking group R 3A second intermediate compound having an epoxy group having a substructure corresponding to the above is produced. As the (pseudo)halogenated epoxy compound, the same type as that which can be used in the fourth reaction of the first production method described above can be used.

[0165] (Third reaction) Next, in the same manner as the first intermediate compound described above, R 4 R on the side 2 At one end of the PFPE chain corresponding to R 4 A third intermediate compound having a terminal group corresponding to the above is produced. In the fourth manufacturing method, R 4 When producing a fluorine-containing ether compound that is not a branched terminal group represented by formula (2), R 4 A third intermediate compound having a terminal group corresponding to R in formula (1) can be produced, for example, by the method shown below. That is, R in formula (1) 2 A fluorine-based compound having hydroxymethyl groups (-CH2OH) at both ends of the corresponding PFPE chain can be prepared, and a known method can be used to react the hydroxymethyl group at one end with a compound containing a structure corresponding to one of the groups shown in formulas (6-1) to (6-3).

[0166] (Fourth reaction) Subsequently, by reacting the second intermediate compound with the third intermediate compound, z in formula (1) is 1, and R 1 and R 4 The terminal group indicated by, or R 2 Fluorine-containing ether compounds can be produced in which one or more of the two PFPE chains shown are different.

[0167] In the first intermediate compound produced by the first reaction of the fourth manufacturing method described above, and the third intermediate compound produced by the third reaction, the terminal group R 1 and / or terminal group R 4 The polar groups contained in the reaction may be protected by appropriate protecting groups. In that case, the protecting groups of the polar groups can be deprotected under appropriate conditions after the second or fourth reaction.

[0168] In the fourth manufacturing method described above, the first, second, and third reactions were carried out in that order. However, the order in which the third reaction is performed is not particularly limited; it may be performed before the first reaction or between the first and second reactions. Furthermore, in the fourth manufacturing method described above, the first intermediate compound obtained in the first reaction was used in the second reaction, but the third intermediate compound obtained in the third reaction may be used instead of the first intermediate compound. In this case, the first intermediate compound is used instead of the third intermediate compound in the fourth reaction.

[0169] <Fifth manufacturing method> In equation (1), z is 2, and R 2 The three PFPE chains shown are the same, and the two linking groups R 3 The same, R 1 and R 4 When producing a fluorine-containing ether compound in which the terminal group shown is the same, or when z in formula (1) is 2 and R 2 Of the three PFPE chains shown, the central R 2 The only difference is the two linking groups R 3 The same, R 1 and R 4 When producing fluorine-containing ether compounds having the same terminal group as indicated by , the following production method can be used.

[0170] (First reaction) R 1 R on the side 2 (=R 4 R on the side 2 At one end of the PFPE chain corresponding to ), R 1 (=R 4 A first intermediate compound having a terminal group corresponding to ) is produced.

[0171] (Second reaction) R in the center of the molecule in equation (1) 2A fluorine-based compound is prepared in which hydroxymethyl groups (-CH2OH) are positioned at both ends of the corresponding PFPE chain. Next, the hydroxyl groups of the hydroxymethyl groups positioned at both ends of the fluorine-based compound and the linking group R 3 A (pseudo)halogenated epoxy compound having a corresponding substructure is reacted.

[0172] In the fifth manufacturing method, the reaction ratio of the fluorine-based compound to the (pseudo)halogenated epoxy compound is preferably about 1:2 (molar ratio). This results in the R at the center of the molecule in formula (1). 2 The PFPE chain corresponding to the PFPE chain has a linking group R at both ends. 3 A second intermediate compound is produced in which an epoxy group having a substructure corresponding to the above is bonded. As the (pseudo)halogenated epoxy compound, the same type as that which can be used in the fourth reaction of the first production method described above can be used.

[0173] (Third reaction) Finally, the first intermediate compound and the second intermediate compound are mixed and reacted. In the fifth manufacturing method, the reaction ratio of the first intermediate compound to the second intermediate compound is preferably about 2:1 (molar ratio).

[0174] By performing the above steps, z in equation (1) is 2, and R 2 The three PFPE chains shown are the same, and the two linking groups R 3 The same, R 1 and R 4 Fluorine-containing ether compounds having the same terminal group as shown, or where z in formula (1) is 2 and R 2 Of the three PFPE chains shown, the central R 2 The only difference is the two linking groups R 3 The same, R 1 and R 4 Fluorine-containing ether compounds with the same terminal group as indicated by can be produced.

[0175] In the first intermediate compound produced by the first reaction of the fifth manufacturing method described above, terminal group R 1(=R 4 The polar groups contained in ) may be protected by appropriate protecting groups. In that case, the protecting groups of the polar groups can be deprotected under appropriate conditions after the first or third reaction. In the fifth manufacturing method described above, the second reaction was carried out after the first reaction, but the first reaction may also be carried out after the second reaction.

[0176] <6th manufacturing method> In equation (1), z is 2, and there are two linking groups R 3 The same, R 1 and R 4 When producing a fluorine-containing ether compound in which at least one of the terminal groups and three PFPE chains shown are different, the following production method can be used.

[0177] (First reaction) In the same manner as when producing the second intermediate compound in the second reaction of the fifth manufacturing method described above, the R in the center of the molecule in formula (1) 2 The PFPE chain corresponding to the PFPE chain has a linking group R at both ends. 3 A first intermediate compound having an epoxy group with a substructure corresponding to the above is produced.

[0178] (Second reaction, third reaction) R 1 R on the side 2 R at one end of the PFPE chain corresponding to 1 A second intermediate compound having a terminal group corresponding to R 4 R on the side 2 R at one end of the PFPE chain corresponding to 4 A third intermediate compound having a terminal group corresponding to the above is produced.

[0179] (Fourth reaction, fifth reaction) The first intermediate compound obtained in the first reaction is reacted with the second intermediate compound in the fourth reaction, and the fourth intermediate compound obtained in the fourth reaction is reacted with the third intermediate compound in the fifth reaction, in sequence.

[0180] By performing the above steps, z in equation (1) is 2, and the two linking groups R 3 The same, R 1 and R 4 This method allows for the production of fluorine-containing ether compounds in which at least one of the terminal groups (indicated by ) or three PFPE chains is different.

[0181] In the second and third intermediate compounds produced by the second and third reactions of the sixth manufacturing method described above, terminal group R 1 and / or R 4 The polar groups contained in the reaction may be protected by appropriate protecting groups. In that case, the protecting groups of the polar groups can be deprotected under appropriate conditions at any stage from the second to the fifth reaction.

[0182] In the sixth manufacturing method described above, the reactions were carried out in the order of the first reaction, the second reaction, and the third reaction. However, the order in which the first reaction is carried out is not particularly limited; it may be performed between the second and third reactions, or after the third reaction. Furthermore, in the sixth manufacturing method described above, the second intermediate compound was used in the fourth reaction and the third intermediate compound was used in the fifth reaction. However, it is also possible to use the third intermediate compound in the fourth reaction and the second intermediate compound in the fifth reaction.

[0183] As the (pseudo)halogen group (X) contained in the (pseudo)alkyl halide compound and (pseudo)epoxy halide compound used in the above-described first to sixth manufacturing methods, for example, at least one selected from a chloro group, a bromo group, an iodine group, a p-toluenesulfonyloxy group, a methanesulfonyloxy group, a trifluoromethanesulfonyloxy group, a perfluoroalkylsulfonyloxy group, and a nitrobenzenesulfonyloxy group can be used.

[0184] [Lubricant for magnetic recording media] The lubricant for magnetic recording media of this embodiment contains a fluorine-containing ether compound represented by 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.

[0185] 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 500 to 10000.

[0186] If the lubricant of this embodiment contains other materials of the fluorine-containing ether compound represented by formula (1), the content of the fluorine-containing ether compound represented by formula (1) in the lubricant of this embodiment is preferably 50% by mass or more, and more preferably 70% by mass or more. The content of the fluorine-containing ether compound represented by formula (1) may be 80% by mass or more, or 90% by mass or more.

[0187] The lubricant of this embodiment contains a fluorine-containing ether compound represented by formula (1) above, and therefore exhibits excellent adhesion to the protective layer. Even with a thin thickness, it can cover the surface of the protective layer with a high coverage rate, forming a lubricating layer with good coverage. Accordingly, the lubricant of this embodiment can form a lubricating layer with excellent wear resistance and smoothness, even with a thin thickness.

[0188] [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, an adhesive layer and / or a soft magnetic layer can be provided between the underlayer and the substrate.

[0189] 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.

[0190] "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.

[0191] "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.

[0192] "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.

[0193] 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.

[0194] "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.

[0195] "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.

[0196] "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.

[0197] 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. In addition to Co, Cr, Pt, and oxides, the first magnetic layer may contain one or more elements selected from B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb, Ru, and Re.

[0198] The second magnetic layer can be made of the same material as the first magnetic layer. The second magnetic layer preferably has a granular structure. The third magnetic layer 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.

[0199] 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.

[0200] 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).

[0201] 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.

[0202] 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 conventional known method, such as vapor deposition, ion beam sputtering, or magnetron sputtering. The magnetic layer 16 is usually formed by sputtering.

[0203] "Protective layer" The protective layer 17 protects the magnetic layer 16. The protective layer 17 may consist of one layer or multiple layers. Examples of materials for the protective layer 17 include carbon, nitrogen-containing carbon, and silicon carbide. 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 the polar groups contained in the fluorine-containing ether compound in the lubricating layer 18.

[0204] 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).

[0205] 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.

[0206] 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.

[0207] 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.

[0208] "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 contains the fluorine-containing ether compound described above.

[0209] 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.

[0210] 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 1.0 nm (10 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 island-like or mesh-like structures. Therefore, the surface of the protective layer 17 can be covered with a high coverage rate by the lubricating layer 18. 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.

[0211] If the surface of the protective layer 17 is not covered with a sufficiently high degree of coverage by the lubricating layer 18, environmental substances adsorbed on the surface of the magnetic recording medium 10 will pass through the gaps in the lubricating layer 18 and penetrate to the layer below the lubricating layer 18. Environmental substances that penetrate to the layer below the lubricating layer 18 will be adsorbed and bound to the protective layer 17, generating contaminants. Then, during magnetic recording and playback, these contaminants (aggregated components) will adhere to (transfer) the magnetic head as a smear, damaging the magnetic head or degrading the magnetic recording and playback characteristics of the magnetic recording and playback device.

[0212] Examples of environmental substances that generate pollutants include siloxane compounds (cyclic siloxanes, linear siloxanes), ionic impurities, relatively high molecular weight hydrocarbons such as octacosane, and plasticizers such as dioctyl phthalate. Examples of metal ions contained in ionic impurities include sodium ions and potassium ions. Examples of inorganic ions contained in ionic impurities include chloride ions, bromide ions, nitrate ions, sulfate ions, and ammonium ions. Examples of organic ions contained in ionic impurities include oxalate ions and formate ions.

[0213] "Method for forming a lubricating layer" One method for forming the lubricating layer 18 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, apply a lubricating layer forming solution to the protective layer 17, and dry it.

[0214] 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 the lubrication layer forming solution include fluorine-based solvents such as Bartrell® XF (trade name, manufactured by Mitsui DuPont Fluorochemicals) and / or Asahiclean® AE-3000 (trade name, manufactured by AGC).

[0215] 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.

[0216] 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 to 180°C. A heat treatment temperature of 100°C or higher provides sufficient improvement in the 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. The heat treatment time is preferably 10 to 120 minutes.

[0217] 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 excellent adhesion to the protective layer 17, and even with a thin thickness, it can cover the surface of the protective layer 17 with a high coverage rate, and has excellent wear resistance and smoothness. Therefore, the magnetic recording medium 10 of this embodiment can stably levitate the magnetic head, and has good long-term reliability and durability. [Examples]

[0218] 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.

[0219] [Example 1] The compound represented by formula (1A) above was obtained by the method shown below. (Manufacturing process for the first intermediate compound (1A-1)) In a 300 mL round-bottom flask under a nitrogen gas atmosphere, HOCH2CF2CF2O(CF2CF2CF2O) r20 g of a compound represented by CF2CF2CH2OH (where r, representing the average degree of polymerization, is 3.8) (number average molecular weight 909, molecular weight distribution 1.1), 1.95 g of 3,4-dihydro-2H-pyran, and 44 mL of a mixed solution (volume ratio 1:1) of the fluorine-based solvent Asahiclean® AE-3000 (manufactured by AGC Inc.) and dichloromethane were charged together and stirred at 0°C until homogeneous to obtain a mixture. 0.084 g of p-toluenesulfonic acid monohydrate was added to this mixture and stirred at 0°C for 30 minutes, then stirred at room temperature for 2 hours to allow the reaction to proceed.

[0220] The reaction product obtained after the reaction was cooled to 0°C, and 50 mL of saturated sodium bicarbonate solution was added to stop the reaction. The resulting reaction solution was transferred to a separatory funnel and extracted three times with 100 mL of ethyl acetate. The organic layer was washed with 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 10.8 g of the compound shown in formula (11) below as the first intermediate compound (1A-1).

[0221] [ka] (In formula (11), THP represents a tetrahydropyranyl group, and r, which indicates the average degree of polymerization, represents 3.8.)

[0222] (Manufacturing process for the second intermediate compound (1A-2)) Under a nitrogen gas atmosphere, 10.0 g of the compound represented by formula (11), which is the first intermediate compound (1A-1) (number average molecular weight 993, 10.1 mmol), 1.9 g of the epoxy compound represented by formula (12) (A-1) (molecular weight 158, 12.1 mmol), and 20 mL of t-butanol were charged into a 100 mL round-bottom flask and stirred at room temperature to obtain a mixture. 0.2 g of potassium tert-butoxide (molecular weight 112, 2.0 mmol) was added to this mixture and the mixture was stirred at 70°C for 5 hours to allow it to react.

[0223] [ka] (In formula (12), THP represents a tetrahydropyranyl group.)

[0224] 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 10.0 g of the compound shown in formula (13) below as the second intermediate compound (1A-2).

[0225] [ka] (In formula (13), THP represents a tetrahydropyranyl group, Rf2 is represented by the above formula, and r, which indicates the average degree of polymerization in Rf2, represents 3.8.)

[0226] (Manufacturing process for the third intermediate compound (1A-3)) Under a nitrogen gas atmosphere, 10.0 g of the compound represented by formula (13), which is the second intermediate compound (1A-2) (number average molecular weight 1151, 8.7 mmol), 2.7 g of the compound (A-2), represented by formula (14) below (molecular weight 209, 13.0 mmol), which is a (pseudo)alkyl halide compound, and 29 mL of N,N-dimethylformamide (DMF) were charged into a 100 mL round-bottom flask and stirred at 0°C until homogeneous. To this homogeneous solution, 0.70 g of sodium hydride (molecular weight 24, 17.4 mmol) was added and the mixture was stirred at 40°C for 10 hours to allow the reaction to proceed.

[0227] [ka] (In formula (14), THP represents a tetrahydropyranyl group.)

[0228] The reaction mixture obtained after the reaction was allowed to return to room temperature, and 23 g of a 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 2 hours. The reaction mixture was gradually transferred to a separatory funnel containing 100 mL of saline solution and extracted three times with 200 mL of ethyl acetate. The organic layer was washed in the following order with 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. By performing the above steps, 6.5 g of the compound shown in formula (15) below was obtained as the third intermediate compound (1A-3).

[0229] [ka] (In equation (15), Rf2 is expressed by the above equation, and r, which represents the average degree of polymerization in Rf2, represents 3.8.)

[0230] (Manufacturing process of compound (1A)) Under a nitrogen gas atmosphere, 6.5 g of the compound represented by formula (15), which is the third intermediate compound (1A-3) (number average molecular weight 1155, 5.6 mmol), 0.39 g of epibromohydrin, a (pseudo)halogenated epoxy compound (molecular weight 137, 2.8 mmol), and 11 mL of N,N-dimethylformamide (DMF) were charged into a 100 mL round-bottom flask. The mixture was stirred at room temperature to obtain a mixture. 2.7 g of cesium carbonate (molecular weight 325, 8.4 mmol) was added to this mixture, and the mixture was reacted by stirring at 70°C for 8 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 4.5 g of compound (1A) (where the average degree of polymerization r in the two Rf2s of formula (1A) is 3.8) (number average molecular weight 2110).

[0232] The obtained compound (1A)1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR(CD3COCD3):δ[ppm]3.39-4.35(36H) 19 F-NMR (CD3COCD3): δ[ppm] -84.0~-83.0(30.4F), -86.4(8F), -124.3(8F), -130.0~-129.0(15.2F)

[0233] [Example 2] In the production process for the third intermediate compound (1A-3) in Example 1, the same procedure as in Example 1 was performed except that 2.9 g (molecular weight 223, 13.0 mmol) of compound (B-1), represented by the following formula (16), which is a (pseudo)alkyl halide compound, was used instead of compound (A-2) represented by formula (14), and 4.6 g (number average molecular weight 2138) of compound (1B) (in the two Rf2 in formula (1B), the average degree of polymerization r is 3.8) was obtained.

[0234] [ka] (In formula (16), THP represents a tetrahydropyranyl group.)

[0235] The obtained compound (1B) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (CD3COCD3): δ[ppm]1.56-1.80(4H), 3.38-4.35(36H) 19 F-NMR (CD3COCD3): δ[ppm] -84.0~-83.1(30.4F), -86.4(8F), -124.2(8F), -130.1~-129.0(15.2F)

[0236] [Example 3] In the manufacturing process of the second intermediate compound (1A-2) in Example 1, 2.1 g (molecular weight 172, 12.1 mmol) of compound (C-1), represented by the following formula (17), which is an epoxy compound synthesized by the following method, was used instead of compound (A-1) represented by the above formula (12). The same procedure as in Example 1 was carried out, and 4.6 g (number average molecular weight 2138) of compound (1C) (where the average degree of polymerization r, which indicates the two Rf2s in formula (1C), is 3.8) was obtained.

[0237] [ka] (In formula (17), THP represents a tetrahydropyranyl group.)

[0238] Compound (C-1), represented by formula (17), was obtained by protecting the hydroxyl group of 3-buten-1-ol with 3,4-dihydro-2H-pyran and oxidizing the double bond of the resulting compound.

[0239] The obtained compound (1C) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (CD3COCD3): δ[ppm]1.50-1.86(4H), 3.39-4.38(36H) 19 F-NMR (CD3COCD3): δ[ppm] -84.0~-82.9(30.4F), -86.3(8F), -124.1(8F), -130.1~-129.0(15.2F)

[0240] [Example 4] In the manufacturing process of the second intermediate compound (1A-2) in Example 1, 2.1 g (molecular weight 172, 12.1 mmol) of compound (D-1), represented by the following formula (18), which is an epoxy compound synthesized by the following method, was used instead of compound (A-1) represented by the above formula (12). The same procedure as in Example 1 was carried out, and 4.4 g (number average molecular weight 2166) of compound (1D) (where the average degree of polymerization r, which indicates the two Rf2s in formula (1D), is 3.8) was obtained.

[0241] [ka] (In formula (18), THP represents a tetrahydropyranyl group.)

[0242] Compound (D-1), represented by formula (18), was obtained by protecting the hydroxyl group of 4-penten-1-ol with 3,4-dihydro-2H-pyran and oxidizing the double bond of the resulting compound.

[0243] The obtained compound (1D) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (CD3COCD3): δ[ppm]1.44-1.85(8H), 3.35-4.45(36H) 19 F-NMR (CD3COCD3): δ[ppm] -84.0~-83.1(30.4F), -86.4(8F), -124.1(8F), -130.0~-128.8(15.2F)

[0244] [Example 5] In the production process for the second intermediate compound (1A-2) in Example 1, 2.4 g (molecular weight 202, 12.1 mmol) of compound (E-1), represented by the following formula (19), which is an epoxy compound synthesized by the following method, was used instead of compound (A-1) represented by the above formula (12). The same procedure as in Example 1 was carried out, and 4.5 g (number average molecular weight 2198) of compound (1E) (where the average degree of polymerization r, which indicates the two Rf2s in formula (1E), is 3.8) was obtained.

[0245] [ka] (In formula (19), THP represents a tetrahydropyranyl group.)

[0246] Compound (E-1), represented by formula (19), was obtained by protecting the hydroxyl group of ethylene glycol monoallyl ether with 3,4-dihydro-2H-pyran and oxidizing the double bond of the resulting compound.

[0247] The obtained compound (1E) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR(CD3COCD3):δ[ppm]3.30-4.52(44H) 19 F-NMR (CD3COCD3): δ[ppm] -84.2~-83.0(30.4F), -86.5(8F), -124.0(8F), -130.0~-129.0(15.2F)

[0248] [Example 6] In the production process for the second intermediate compound (1A-2) in Example 1, 2.4 g (molecular weight 200, 12.1 mmol) of compound (F-1), represented by the following formula (20), which is an epoxy compound synthesized by the following method, was used instead of compound (A-1) represented by the above formula (12). The same procedure as in Example 1 was followed, and 4.5 g (number average molecular weight 2194) of compound (1F) (where the average degree of polymerization r, representing the two Rf2s in formula (1F), is 3.8) was obtained.

[0249] [ka] (In formula (20), THP represents a tetrahydropyranyl group.)

[0250] Compound (F-1), represented by formula (20), was obtained by protecting the hydroxyl group of 5-hexen-1-ol with 3,4-dihydro-2H-pyran and oxidizing the double bond of the resulting compound.

[0251] The obtained compound (1F) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (CD3COCD3): δ[ppm]1.25-1.78(12H), 3.40-4.38(36H) 19 F-NMR (CD3COCD3): δ[ppm] -84.0~-83.1(30.4F), -86.4(8F), -124.1(8F), -130.1~-129.0(15.2F)

[0252] [Example 7] In the manufacturing process of the first intermediate compound (1A-1) in Example 1, HOCH2CF2CF2O(CF2CF2CF2O) r Instead of CF2CF2CH2OH (where r, representing the average degree of polymerization, is 3.8), use HOCH2CF2O(CF2CF2O) p (CF2O) qThe first intermediate compound (1G-1) was synthesized using 20 g of the compound represented by CF2CH2OH (where p, representing the average degree of polymerization, is 4.0, and q, representing the average degree of polymerization, is 4.0) (number average molecular weight 906, molecular weight distribution 1.1).

[0253] Subsequently, in the production process for the second intermediate compound (1A-2) in Example 1, 2.4 g (molecular weight 200, 12.1 mmol) of compound (F-1), represented by the epoxy compound (20), was used instead of compound (A-1), represented by formula (12). In the production process for the third intermediate compound (1A-3), 2.8 g (molecular weight 223, 12.6 mmol) of compound (B-1), represented by the (pseudo)alkyl halide compound (16), was used instead of compound (A-2), represented by formula (14). The same procedure as in Example 1 was followed, and 4.3 g (number average molecular weight 2217) of the compound represented by the formula (1G) (where the average degree of polymerization p is 4.0 and the average degree of polymerization q is 4.0 in the two Rf1s in formula (1G)) was obtained.

[0254] The obtained compound (1G) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (CD3COCD3): δ[ppm]1.37-1.85(16H), 3.36-4.46(26H) 19 F-NMR (CD3COCD3): δ[ppm] -55.6~-50.6(16F), -77.7(4F), -80.3(4F), -91.0~-88.4(32F)

[0255] [Example 8] (Manufacturing process for the first intermediate compound (1H-1)) The first intermediate compound (1H-1), represented by the following formula (21), was synthesized by performing the same procedure as in the manufacturing process for the first intermediate compound (1G-1) in Example 7.

[0256] [ka] (In formula (21), THP represents a tetrahydropyranyl group, p (representing the average degree of polymerization) is 4.0, and q (representing the average degree of polymerization) is 4.0.)

[0257] (Manufacturing process for the second intermediate compound (1H-2)) Under a nitrogen gas atmosphere, 10.0 g of the first intermediate compound (1H-1) represented by formula (21), 3.3 g of pyridine (molecular weight 79, 15.2 mmol), and 10 mL of dichloromethane were charged into a 100 mL round-bottom flask and stirred at 0°C until homogeneous to obtain a mixture. To this mixture, 3.4 g of nonafluorobutanesulfonyl fluoride (molecular weight 302, 11.1 mmol) was added and stirred at 0°C for 30 minutes, then stirred at room temperature for 2 hours to allow the reaction to proceed.

[0258] The reaction product obtained after the reaction was cooled to 25°C and neutralized with a 5% citric acid aqueous solution. It was transferred to a separatory funnel and extracted three times with 100 mL of dichloromethane. 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 12.0 g of the compound shown in formula (22) below as the second intermediate compound (1H-2).

[0259] [ka] (In formula (22), THP represents a tetrahydropyranyl group, and Nf represents a nonafluorobutanesulfonyl group. Rf1 is represented by the above formula, where p, which indicates the average degree of polymerization in Rf1, is 4.0, and q, which indicates the average degree of polymerization, is 4.0.)

[0260] (Manufacturing process for the third intermediate compound (1H-3)) Under a nitrogen gas atmosphere, 12.0 g of the compound represented by formula (22), which is the second intermediate compound (1H-2) (number average molecular weight 1272, 9.4 mmol), 1.9 g of the compound represented by formula (23), which is an alcohol compound (H-1) (molecular weight 132, 14.2 mmol), and 19 mL of N,N-dimethylformamide (DMF) were charged into a 100 mL round-bottom flask and stirred at 0°C until homogeneous. To this homogeneous solution, 0.76 g of sodium hydride (molecular weight 24, 8.9 mmol) was added and the mixture was stirred at 40°C for 10 hours to allow the reaction to proceed.

[0261] [ka]

[0262] The reaction mixture obtained after the reaction was allowed to return to room temperature, and 25 g of a 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 2 hours. The reaction mixture was gradually transferred to a separatory funnel containing 100 mL of saline solution and extracted three times with 200 mL of ethyl acetate. The organic layer was washed in the following order with 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. By performing the above steps, 6.5 g of the compound shown in formula (24) below was obtained as the third intermediate compound (1H-3).

[0263] [ka] (In equation (24), Rf1 is expressed by the above equation, where p, which represents the average degree of polymerization in Rf1, is 4.0, and q, which represents the average degree of polymerization, is 4.0.)

[0264] (Manufacturing process for compound (1H)) Under a nitrogen gas atmosphere, 6.5 g of the compound represented by formula (24), which is a third intermediate compound (1H-3) (number average molecular weight 1110, 5.9 mmol), 0.4 g of epibromohydrin, a (pseudo)halogenated epoxy compound (molecular weight 137, 2.9 mmol), and 12 mL of N,N-dimethylformamide (DMF) were charged into a 100 mL round-bottom flask. The mixture was stirred at room temperature to obtain a mixture. 2.9 g of cesium carbonate (molecular weight 325, 8.8 mmol) was added to this mixture, and the mixture was stirred at 70°C for 8 hours to allow it to react.

[0265] 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 4.5 g of compound (1H) (in formula (1H), the average degree of polymerization p is 4.0 and the average degree of polymerization q is 4.0) (number average molecular weight 2016).

[0266] The obtained compound (1H) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR(CD3COCD3):δ[ppm]3.36-4.68(28H) 19 F-NMR (CD3COCD3): δ[ppm] -55.5~-50.6(16F), -77.8(4F), -80.2(4F), -91.0~-88.4(32F)

[0267] [Example 9] In Example 8, in the manufacturing process of the first intermediate compound (1H-1), HOCH2CF2O(CF2CF2O) p (CF2O) q Instead of CF2CH2OH (where p, representing the average degree of polymerization, is 4.0, and q, representing the average degree of polymerization, is 4.0), use HOCH2CF2O(CF2CF2O) p (CF2O) qExcept for using 20 g of the compound represented by CF2CH2OH (where p, representing the average degree of polymerization, is 6.3 and q, representing the average degree of polymerization, is 0) (number average molecular weight 909, molecular weight distribution 1.1), and for synthesizing the third intermediate compound (1H-3) using 2.1 g of the alcohol compound represented by the following formula (25) (molecular weight 146, 14.1 mmol) instead of the compound (H-1) represented by formula (23) above, the same procedure as in Example 8 was followed to obtain 4.6 g of compound (1I) (where p, representing the average degree of polymerization, is 6.3 and q, representing the average degree of polymerization, is 0) in the two Rf1s in formula (1I) (number average molecular weight 2050).

[0268] [ka]

[0269] The obtained compound (1I) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (CD3COCD3): δ[ppm]1.50-1.89(2H), 3.46-4.59(30H) 19 F-NMR (CD3COCD3): δ[ppm] -78.6(4F), -81.2(4F), -90.1~-88.4(50.4F)

[0270] [Example 10] In the manufacturing process of the first intermediate compound (1H-1) in Example 8, HOCH2CF2O(CF2CF2O) p (CF2O) q Instead of CF2CH2OH (where p, representing the average degree of polymerization, is 4.0, and q, representing the average degree of polymerization, is 4.0), use HOCH2CF2CF2O(CF2CF2CF2O) rExcept for using 20 g of the compound represented by CF2CF2CH2OH (where r, representing the average degree of polymerization, is 3.8) (number average molecular weight 909, molecular weight distribution 1.1), and for synthesizing the third intermediate compound (1H-3), 4.1 g of the alcohol compound represented by the following formula (26) (molecular weight 288, 14.1 mmol) was used instead of the compound represented by formula (23) (H-1) to synthesize the third intermediate compound (1J-3), the same procedure as in Example 8 was followed to obtain 4.8 g of compound (1J) (where r, representing the average degree of polymerization, is 3.8 in both Rf2 in formula (1J)) (number average molecular weight 2078).

[0271] [ka] (In formula (26), THP represents a tetrahydropyranyl group.)

[0272] Compound (J-1), represented by formula (26), was prepared by the following method: The hydroxyl group of ethyl 3-hydroxypropanoate was protected with 3,4-dihydro-2H-pyran, and (2-bromoethoxy)tetrahydro-2H-pyran, represented by formula (14), was reacted with the α-position of the ester group of the resulting compound to construct a trisubstituted carbon atom. Subsequently, the ester group of the compound having the trisubstituted carbon atom was reduced. This yielded compound (J-1), represented by formula (26).

[0273] The obtained compound (1J) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (CD3COCD3): δ[ppm]1.48-1.84(6H), 3.51-4.50(30H) 19 F-NMR (CD3COCD3): δ[ppm] -84.0~-83.0(30.4F), -86.3(8F), -124.0(8F), -130.0~-128.8(15.2F)

[0274] [Example 11] In the manufacturing process of the third intermediate compound (1J-3) in Example 10, 4.3 g (molecular weight 302, 14.2 mmol) of compound (K-1), represented by the following formula (27), which is an alcohol compound synthesized by the following method, was used instead of compound (J-1) represented by the above formula (26). The same procedure as in Example 10 was followed, and 4.9 g (number average molecular weight 2106) of compound (1K) (where the average degree of polymerization r, representing the two Rf2s in formula (1K), is 3.8) was obtained.

[0275] [ka] (In formula (27), THP represents a tetrahydropyranyl group.)

[0276] Compound (K-1), represented by formula (27), was prepared by the following method. The hydroxyl group of ethyl 3-hydroxypropanoate was protected with 3,4-dihydro-2H-pyran, and the α-position of the ester group of the resulting compound was reacted with (3-bromopropoxy)tetrahydro-2H-pyran, represented by formula (16), to construct a trisubstituted carbon atom. Subsequently, the ester group of the compound having the trisubstituted carbon atom was reduced. This yielded compound (K-1), represented by formula (27).

[0277] The obtained compound (1K) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR(CD3COCD3): δ[ppm]1.36-1.80(10H), 3.43-4.50(30H) 19 F-NMR (CD3COCD3): δ[ppm] -84.3~-83.0(30.4F), -86.4(8F), -124.2(8F), -130.1~-128.8(15.2F)

[0278] [Example 12] In the manufacturing process of the third intermediate compound (1I-3) in Example 9, 4.3 g (molecular weight 302, 14.2 mmol) of compound (L-1), represented by the following formula (28), which is an alcohol compound synthesized by the following method, was used instead of compound (I-1) represented by the above formula (25). The same procedure as in Example 9 was followed, and 4.8 g (number average molecular weight 2106) of compound (1L) (in the two Rf1s of formula (1L), the average degree of polymerization p is 6.3 and the average degree of polymerization q is 0) was obtained.

[0279] [ka] (In formula (28), THP represents a tetrahydropyranyl group.)

[0280] Compound (L-1) represented by formula (28) was prepared by the following method: The hydroxyl group of ethyl 4-hydroxybutanoate was protected with 3,4-dihydro-2H-pyran, and (2-bromoethoxy)tetrahydro-2H-pyran represented by formula (14) was reacted with the α-position of the ester group of the resulting compound to construct a trisubstituted carbon atom. Subsequently, the ester group of the compound having the trisubstituted carbon atom was reduced. This yielded compound (L-1) represented by formula (28).

[0281] The obtained compound (1L) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR(CD3COCD3): δ[ppm]1.34-1.80(10H), 3.40-4.52(30H) 19 F-NMR (CD3COCD3): δ[ppm] -78.6(4F), -81.0(4F), -90.1~-88.4(50.4F)

[0282] [Example 13] In the production process for the third intermediate compound (1H-3) in Example 8, 4.3 g (molecular weight 302, 14.2 mmol) of compound (M-1), represented by the following formula (29), which is an alcohol compound synthesized by the following method, was used instead of compound (H-1) represented by the above formula (23). The same procedure as in Example 8 was followed, and 4.9 g (number average molecular weight 2101) of compound (1M) (in the two Rf1 in formula (1M), p, which indicates the average degree of polymerization, is 4.0, and q, which indicates the average degree of polymerization, is 4.0) was obtained.

[0283] [ka] (In formula (29), THP represents a tetrahydropyranyl group.)

[0284] Compound (M-1), represented by formula (29), was synthesized by the following method. First, a trisubstituted carbon atom was constructed by reacting (2-bromoethoxy)tetrahydro-2H-pyran, represented by formula (14), with the α-position of the ester group of ethyl 3-butenoate. Then, the ester group of the compound having the trisubstituted carbon atom was reduced, the resulting primary hydroxyl group was protected with 3,4-dihydro-2H-pyran, and finally, the carbon-carbon double bond site was hydroborized to obtain compound (M-1), represented by formula (29).

[0285] The obtained compound (1M) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (CD3COCD3): δ[ppm]1.37-1.83(14H), 3.43-4.50(26H) 19 F-NMR (CD3COCD3): δ[ppm] -55.3~-50.6(16F), -77.7(4F), -80.2(4F), -91.0~-88.3(32F)

[0286] [Example 14] In the manufacturing process of the third intermediate compound (1J-3) in Example 10, 4.5 g (molecular weight 316, 14.2 mmol) of compound (N-1), represented by the following formula (30), which is an alcohol compound synthesized by the following method, was used instead of compound (J-1) represented by the above formula (26). The same procedure as in Example 10 was followed, and 5.0 g (number average molecular weight 2134) of compound (1N) (where the average degree of polymerization r, representing the two Rf2s in formula (1N), is 3.8) was obtained.

[0287] [ka] (In formula (30), THP represents a tetrahydropyranyl group.)

[0288] Compound (N-1), represented by formula (30), was synthesized by the following method. First, the hydroxyl group of 1,5-dihydroxy-3-pentanone was protected with 3,4-dihydro-2H-pyran, and the ketone group was converted to an unsaturated ester with triethyl phosphonoacetate. Subsequently, compound (N-1), represented by formula (30), was obtained by reducing the carbon-carbon unsaturated bond and ester group of the resulting compound.

[0289] The obtained compound (1N) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (CD3COCD3): δ[ppm]1.32-1.76(14H), 3.45-4.53(30H) 19 F-NMR (CD3COCD3): δ[ppm] -84.4~-83.1(30.4F), -86.4(8F), -124.2(8F), -130.0~-128.8(15.2F)

[0290] [Example 15] In the manufacturing process of the third intermediate compound (1I-3) in Example 9, 4.7 g (molecular weight 330, 14.2 mmol) of compound (O-1), represented by the following formula (31), which is an alcohol compound synthesized by the following method, was used instead of compound (I-1) represented by the above formula (25). The same procedure as in Example 9 was followed, and 5.0 g (number average molecular weight 2162) of compound (1O) (where the average degree of polymerization p is 6.3 and the average degree of polymerization q is 0 in the two Rf1s in formula (1O)) was obtained.

[0291] [ka] (In formula (31), THP represents a tetrahydropyranyl group.)

[0292] Compound (O-1), represented by formula (31), was synthesized by the following method. First, the hydroxyl group of 1,6-dihydroxy-3-hexanone was protected with 3,4-dihydro-2H-pyran, and the ketone group was converted to an unsaturated ester with triethyl phosphonoacetate. Then, the carbon-carbon unsaturated bond and ester group of the resulting compound were reduced to obtain compound (O-1), represented by formula (31).

[0293] The obtained compound (1O) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR(CD3COCD3): δ[ppm]1.33-1.87(18H), 3.40-4.62(30H) 19 F-NMR (CD3COCD3): δ[ppm] -78.5(4F), -81.2(4F), -90.2~-88.3(50.4F)

[0294] [Example 16] (Manufacturing process for the first intermediate compound (2A-1)) In the manufacturing process of intermediate compound (1A-1) in Example 1, HOCH2CF2CF2O(CF2CF2CF2O) rInstead of CF2CF2CH2OH (where r, representing the average degree of polymerization, is 3.8), use HOCH2CF2CF2O(CF2CF2CF2O) r Except for using 20 g of the compound represented by CF2CF2CH2OH (where r, representing the average degree of polymerization, is 2.0) (number average molecular weight 610, molecular weight distribution 1.1), the same procedure as in Example 1 up to the production step of the third intermediate compound (1A-3) was carried out to obtain 6.0 g of the first intermediate compound (2A-1) represented by the following formula (32).

[0295] [ka] (In equation (32), Rf2 is expressed by the above equation, and r, which represents the average degree of polymerization in Rf2, represents 2.0.)

[0296] (Manufacturing process for the second intermediate compound (2A-2)) In a 100 mL round-bottom flask under a nitrogen gas atmosphere, HOCH2CF2CF2O(CF2CF2CF2O) r 10 g of a compound represented by CF2CF2CH2OH (where r, representing the average degree of polymerization, is 2.0) (number average molecular weight 610, molecular weight distribution 1.1), 4.9 g of epibromohydrin (molecular weight 136, 36.1 mmol), a (pseudo)halogenated epoxy compound, and 33 mL of t-butanol were charged together and stirred at room temperature to form a mixture. 4.6 g of potassium tert-butoxide (molecular weight 112, 41.0 mmol) was added to this mixture and the mixture was stirred at 70°C for 5 hours to allow it to react.

[0297] 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 8.0 g of the compound shown in formula (33) below as the second intermediate compound (2A-2).

[0298] [ka] (In equation (33), r, which represents the average degree of polymerization, is 2.0.)

[0299] (Manufacturing process for compound (2A)) Under a nitrogen gas atmosphere, 6.0 g of the first intermediate compound (2A-1) represented by formula (32) above (number average molecular weight 856, 7.0 mmol), 2.5 g of the second intermediate compound (2A-2) represented by formula (33) above (number average molecular weight 722, 3.5 mmol), and 14 mL of t-butanol were charged into a 100 mL round-bottom flask and stirred at room temperature to obtain a mixture. 3.4 g of potassium tert-butoxide (molecular weight 112, 10.5 mmol) was added to this mixture and the mixture was stirred at 70°C for 10 hours to allow it to react.

[0300] 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 4.5 g of compound (2A) (where the average degree of polymerization r is 2.0 in the three Rf2 values ​​of formula (2A)) (number average molecular weight 2123).

[0301] The obtained compound (2A) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR(CD3COCD3):δ[ppm]3.35~4.41(46H) 19 F-NMR (CD3COCD3): δ[ppm] -84.0~-83.0(30.4F), -86.4(8F), -124.3(8F), -130.0~-129.0(15.2F)

[0302] [Example 17] In the production process for the first intermediate compound (2A-1) in Example 16, 3.9 g (molecular weight 223, 13.0 mmol) of compound (B-1) represented by formula (16) was used instead of compound (A-2) represented by formula (14). The same procedure as in Example 16 was followed to obtain 6.1 g (number average molecular weight 2151) of compound (2B) (where the average degree of polymerization r is 2.0 in the three Rf2 in formula (2B)).

[0303] The obtained compound (2B) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (CD3COCD3): δ[ppm]1.53-1.83(4H), 3.40-4.36(46H) 19 F-NMR (CD3COCD3): δ[ppm] -84.0~-83.1(30.4F), -86.3(8F), -124.3(8F), -130.1~-129.0(15.2F)

[0304] [Example 18] In the production process for the first intermediate compound (2A-1) in Example 16, the same procedure as in Example 16 was performed except that 5.9 g (molecular weight 172, 34.6 mmol) of compound (C-1) represented by formula (17) was used instead of compound (A-1) represented by formula (12), and 6.0 g (number average molecular weight 2151) of compound (2C) (where the average degree of polymerization r in the three Rf2 in formula (2C) is 2.0) was obtained.

[0305] The obtained compound (2C) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (CD3COCD3): δ[ppm]1.48-1.87(4H), 3.40-4.39(46H) 19F-NMR (CD3COCD3): δ[ppm] -84.0~-83.0(30.4F), -86.4(8F), -124.2(8F), -130.1~-129.0(15.2F)

[0306] [Example 19] In the production process for the first intermediate compound (2A-1) in Example 16, the same procedure as in Example 16 was performed except that 6.4 g (molecular weight 186, 34.6 mmol) of compound (D-1) represented by formula (18) was used instead of compound (A-1) represented by formula (12), and 6.2 g (number average molecular weight 2179) of compound (2D) (where the average degree of polymerization r in the three Rf2 in formula (2D) is 2.0) was obtained.

[0307] The obtained compound (2D) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (CD3COCD3): δ[ppm]1.45-1.87(8H), 3.36-4.50(46H) 19 F-NMR (CD3COCD3): δ[ppm] -84.0~-83.1(30.4F), -86.3(8F), -124.4(8F), -130.0~-129.0(15.2F)

[0308] [Example 20] In the production process for the first intermediate compound (2A-1) in Example 16, the same procedure as in Example 16 was performed, except that 7.0 g (molecular weight 202, 34.6 mmol) of compound (E-1) represented by formula (19) was used instead of compound (A-1) represented by formula (12), and 6.4 g (number average molecular weight 2211) of compound (2E) (where the average degree of polymerization r is 2.0 in the three Rf2 in formula (2E)) was obtained.

[0309] The obtained compound (2E) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR(CD3COCD3):δ[ppm]3.30~4.57(54H) 19 F-NMR (CD3COCD3): δ[ppm] -84.2~-83.1(30.4F), -86.4(8F), -124.3(8F), -130.1~-129.0(15.2F)

[0310] [Example 21] In the production process for the first intermediate compound (2A-1) in Example 16, 6.9 g (molecular weight 200, 34.6 mmol) of compound (F-1) represented by formula (20) was used instead of compound (A-1) represented by formula (12) above. The same procedure as in Example 16 was followed, and 6.3 g (number average molecular weight 2207) of compound (2F) (where the average degree of polymerization r is 2.0 in the three Rf2 in formula (2F)) was obtained.

[0311] The obtained compound (2F) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (CD3COCD3): δ[ppm]1.25-1.80(12H), 3.40-4.39(46H) 19 F-NMR (CD3COCD3): δ[ppm] -84.0~-83.0(30.4F), -86.3(8F), -124.3(8F), -130.1~-129.1(15.2F)

[0312] [Example 22] (Manufacturing process for the first intermediate compound (2G-1)) In the manufacturing process of the first intermediate compound (2A-1) in Example 16, HOCH2CF2CF2O(CF2CF2CF2O) r Instead of CF2CF2CH2OH (where r, representing the average degree of polymerization, is 2.0), use HOCH2CF2O(CF2CF2O) p (CF2O) qThe first intermediate compound (2G-1) was prepared by following the same procedure as in Example 16, except that 20 g of the compound represented by CF2CH2OH (where p, representing the average degree of polymerization, is 2.4, and q, representing the average degree of polymerization, is 2.4) (number average molecular weight 614, molecular weight distribution 1.1) was used, 6.89 g of the epoxy compound represented by the above formula (20) (F-1) (molecular weight 200, 34.4 mmol) was used instead of the compound represented by formula (12) (A-1), and 3.7 g of the compound represented by the above formula (16) (molecular weight 223, 16.7 mmol) was used instead of the compound represented by the above formula (14) (A-2).

[0313] (Manufacturing process for the second intermediate compound (2G-2)) In the manufacturing process of the second intermediate compound (2A-2) in Example 16, HOCH2CF2CF2O(CF2CF2CF2O) r Instead of CF2CF2CH2OH (where r, representing the average degree of polymerization, is 2.0), use HOCH2CF2O(CF2CF2O) p (CF2O) q The second intermediate compound (2G-2) was prepared by following the same procedure as in Example 16, except that 10 g of the compound represented by CF2CH2OH (where p, representing the average degree of polymerization, is 2.4, and q, representing the average degree of polymerization, is 2.4) (number average molecular weight 614, molecular weight distribution 1.1) was used.

[0314] (Manufacturing process for compound (2G)) Using the first intermediate compound (2G-1) and the second intermediate compound (2G-2) described above, the same procedure as the manufacturing process for compound (2A) in Example 16 was carried out to obtain 6.0 g of compound (2G) (number average molecular weight 2249) (wherein the three Rf1 in formula (2G), p, which indicates the average degree of polymerization, is 2.4, and q, which indicates the average degree of polymerization, is 2.4).

[0315] The obtained compound (2G) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1H-NMR (CD3COCD3): δ[ppm]1.36-1.85(16H), 3.35-4.46(46H) 19 F-NMR (CD3COCD3): δ[ppm] -55.6~-50.6(14.4F), -77.7(6F), -80.2(6F), -91.0~-88.4(28.8F)

[0316] [Example 23] (Manufacturing process for the first intermediate compound (2H-1)) In the manufacturing process of the first intermediate compound (1H-1) in Example 8, HOCH2CF2O(CF2CF2O) p (CF2O) q Instead of the compound represented by CF2CH2OH (where p, representing the average degree of polymerization, is 4.0, and q, representing the average degree of polymerization, is 4.0), use HOCH2CF2O(CF2CF2O) p (CF2O) q Except for using 20 g of the compound represented by CF2CH2OH (where p, representing the average degree of polymerization, is 2.4, and q, representing the average degree of polymerization, is 2.4) (number average molecular weight 614, molecular weight distribution 1.1), the same procedure as in Example 8 up to the production step of the third intermediate compound (1H-3) was carried out to obtain 6.0 g of the first intermediate compound (2H-1) represented by the following formula (34).

[0317] [ka] (In equation (34), Rf1 is expressed by the above equation, where p, which represents the average degree of polymerization in Rf1, is 2.4, and q, which represents the average degree of polymerization, is 2.4.)

[0318] (Process for producing the second intermediate compound (2H-2)) The second intermediate compound (2H-2) was synthesized by performing the same procedure as in the production process for the second intermediate compound (2G-2) in Example 22.

[0319] (Manufacturing process for compound (2H)) Under a nitrogen gas atmosphere, 6.0 g of the first intermediate compound (2H-1) represented by formula (34) (number average molecular weight 819, 7.3 mmol), the second intermediate compound (2H-2), and 15 mL of t-butanol were charged into a 100 mL round-bottom flask and stirred at room temperature to obtain a mixture. 3.6 g of potassium tert-butoxide (molecular weight 112, 11.0 mmol) was added to this mixture and the mixture was stirred at 70°C for 10 hours to allow it to react.

[0320] 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 4.6 g of compound (2H) (in formula (2H), the average degree of polymerization p is 2.4 and the average degree of polymerization q is 2.4 for the three Rf1 units). (Number average molecular weight 2049)

[0321] The resulting compound (2H) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR(CD3COCD3):δ[ppm]3.36~4.66(38H) 19 F-NMR (CD3COCD3): δ[ppm] -55.7~-50.6(14.4F), -77.8(6F), -80.1(6F), -91.0~-88.4(28.8F)

[0322] [Example 24] (Manufacturing process for the first intermediate compound (2I-1)) In the manufacturing process of the first intermediate compound (2H-1) in Example 23, HOCH2CF2O(CF2CF2O) p (CF2O) q Instead of CF2CH2OH (where p, representing the average degree of polymerization, is 2.4, and q, representing the average degree of polymerization, is 2.4), use HOCH2CF2O(CF2CF2O) p (CF2O) qThe first intermediate compound (2I-1) was prepared by following the same procedure as in Example 23, except that 20 g of the compound represented by CF2CH2OH (where p, representing the average degree of polymerization, is 3.8, and q, representing the average degree of polymerization, is 0) (number average molecular weight 618, molecular weight distribution 1.1) was used, and 2.7 g of the alcohol compound represented by formula (25) (I-1) (molecular weight 146, 18.3 mmol) was used instead of the compound represented by formula (23) (H-1) above.

[0323] (Manufacturing process for the second intermediate compound (2I-2)) In the manufacturing process of the second intermediate compound (2A-2) in Example 16, HOCH2CF2CF2O(CF2CF2CF2O) r Instead of CF2CF2CH2OH (where r, representing the average degree of polymerization, is 2.0), use HOCH2CF2O(CF2CF2O) p (CF2O) q The second intermediate compound (2I-2) was prepared by following the same procedure as in Example 16, except that 10 g of the compound represented by CF2CH2OH (where p, representing the average degree of polymerization, is 3.8, and q, representing the average degree of polymerization, is 0) (number average molecular weight 618, molecular weight distribution 1.1) was used.

[0324] (Manufacturing process for compound (2I)) Using the first intermediate compound (2I-1) and the second intermediate compound (2I-2) described above, the same procedure as in the production process for compound (2H) in Example 23 was carried out to obtain 4.5 g of compound (2I) (number average molecular weight 2089) (where the average degree of polymerization p is 3.8 and the average degree of polymerization q is 0 in the three Rf1 units of formula (2I)).

[0325] The obtained compound (2I) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR(CD3COCD3): δ[ppm]1.50-1.90(2H), 3.45-4.60(40H) 19F-NMR (CD3COCD3): δ[ppm] -78.6(6F), -81.3(6F), -90.1~-88.6(45.6F)

[0326] [Example 25] (Manufacturing process for the first intermediate compound (2J-1)) In the manufacturing process of the first intermediate compound (2H-1) in Example 23, HOCH2CF2O(CF2CF2O) p (CF2O) q Instead of CF2CH2OH (where p, representing the average degree of polymerization, is 2.4, and q, representing the average degree of polymerization, is 2.4), use HOCH2CF2CF2O(CF2CF2CF2O) r The first intermediate compound (2J-1) was prepared by following the same procedure as in Example 23, except that 20 g of the compound represented by CF2CF2CH2OH (where r, representing the average degree of polymerization, is 2.0) (number average molecular weight 610, molecular weight distribution 1.1) was used, and 4.1 g of the alcohol compound represented by formula (26) (J-1) (molecular weight 288, 14.1 mmol) was used instead of the compound represented by formula (23) (H-1).

[0327] (Manufacturing process for the second intermediate compound (2J-2)) The second intermediate compound (2J-2) was synthesized by performing the same procedure as the manufacturing process for the second intermediate compound (2A-2) in Example 16. (Manufacturing process for compound (2J)) Using the first intermediate compound (2J-1) and the second intermediate compound (2J-2) described above, the same procedure as in the production process for compound (2H) in Example 23 was carried out to obtain 4.5 g of compound (2J) (where the average degree of polymerization r is 2.0 in the three Rf2 in formula (2J)) (number average molecular weight 2091).

[0328] The obtained compound (2J) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1H-NMR (CD3COCD3): δ[ppm]1.46-1.86(6H), 3.40-4.55(40H) 19 F-NMR (CD3COCD3): δ[ppm] -84.0~-83.0(30.4F), -86.2(8F), -124.4(8F), -130.0~-129.0(15.2F)

[0329] [Example 26] In the production process for the first intermediate compound (2J-1) in Example 25, the same procedure as in Example 25 was performed, except that 5.6 g (molecular weight 302, 18.4 mmol) of the alcohol compound (K-1) represented by formula (27) was used instead of the compound (J-1) represented by formula (26), and 4.7 g (number average molecular weight 2119) of compound (2K) (where the average degree of polymerization r in the three Rf2 in formula (2K) is 2.0) was obtained.

[0330] The obtained compound (2K) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR(CD3COCD3): δ[ppm]1.35-1.86(10H), 3.47-4.63(40H) 19 F-NMR (CD3COCD3): δ[ppm] -84.0~-83.0(30.4F), -86.2(8F), -124.4(8F), -130.1~-129.0(15.2F)

[0331] [Example 27] In the production process for the first intermediate compound (2I-1) in Example 24, the same procedure as in Example 24 was performed, except that 5.6 g (molecular weight 302, 18.4 mmol) of the alcohol compound (L-1) represented by formula (28) was used instead of the compound (I-1) represented by formula (25), and 4.7 g (number average molecular weight 2145) of compound (2L) (where the average degree of polymerization p is 3.8 and the average degree of polymerization q is 0 in the three Rf1 in formula (2L)) was obtained.

[0332] The obtained compound (2L) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR(CD3COCD3): δ[ppm]1.34-1.80(10H), 3.40-4.52(40H) 19 F-NMR (CD3COCD3): δ[ppm] -78.6(6F), -81.2(6F), -90.1~-88.6(45.6F)

[0333] [Example 28] In the production process for the first intermediate compound (2H-1) in Example 23, 5.5 g (molecular weight 302, 18.4 mmol) of the alcohol compound (M-1) represented by formula (29) was used instead of the compound (H-1) represented by formula (23) above. The same procedure as in Example 23 was followed, and 4.8 g (number average molecular weight 2133) of compound (2M) (where the average degree of polymerization p is 2.4 and the average degree of polymerization q is 2.4 in the three Rf1 in formula (2M)) was obtained.

[0334] The obtained compound (2M) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (CD3COCD3): δ[ppm]1.40-1.86(14H), 3.40-4.60(36H) 19 F-NMR (CD3COCD3): δ[ppm] -55.7~-50.7(14.4F), -77.7(6F), -80.1(6F), -91.0~-88.4(28.8F)

[0335] [Example 29] In the manufacturing process for the first intermediate compound (2J-1) in Example 25, the same procedure as in Example 25 was performed, except that 5.8 g (molecular weight 316, 18.4 mmol) of the alcohol compound (N-1) represented by formula (30) was used instead of the compound (J-1) represented by formula (26), and 4.9 g (number average molecular weight 2147) of compound (2N) (where the average degree of polymerization r in the three Rf2 in formula (2N) is 2.0) was obtained.

[0336] The obtained compound (2N) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR(CD3COCD3): δ[ppm]1.35-1.80(14H), 3.40-4.66(40H) 19 F-NMR (CD3COCD3): δ[ppm] -84.0~-83.0(30.4F), -86.1(8F), -124.3(8F), -130.0~-129.0(15.2F)

[0337] [Example 30] In the production process for the first intermediate compound (2I-1) in Example 24, the same procedure as in Example 24 was performed, except that 6.0 g (molecular weight 330, 18.4 mmol) of the alcohol compound (O-1) represented by formula (31) was used instead of the compound (I-1) represented by formula (25) above. 5.0 g (number average molecular weight 2201) of compound (2O) (where the average degree of polymerization p is 3.8 and the average degree of polymerization q is 0 in the three Rf1 units in formula (2O)) was obtained.

[0338] The obtained compound (2O) 1 H-NMR and 19 The structure was identified by performing 1F-NMR measurements, based on the following results. 1 H-NMR (CD3COCD3): δ[ppm]1.35-1.87(18H), 3.42-4.68(40H) 19F-NMR (CD3COCD3): δ[ppm] -78.5(6F), -81.0(6F), -90.1~-88.6(45.6F)

[0339] The values ​​of z and R obtained when the compounds (1A) to (1O) and (2A) to (2O) of Examples 1 to 30 are substituted into formula (1) are as follows: 1 , R 2 , R 3 , R 4 The structure is shown in Tables 1 to 5. Tables 1 to 5 show the following items from left to right: "z" is the value of z shown in equation (1), and "R 1 " is the branched terminal group R in formula (1) 1 The left side shows the actual branched terminal group, and the right side shows R 1 The structure when expressed by equation (2-1) or (2-2) is shown, and "R 2 " is R in equation (1) 2 The structure when expressed by formula (7-1) or (7-2) is shown, and "R 3 " is R in equation (1) 3 We will show that this is shown by equation (4), and "R 4 " is R in equation (1) 4 The structure is shown. Furthermore, in compounds (1A) to (1O) and (2A) to (2O) of Examples 1 to 30, the R represented by formula (4) 3 Therefore, h=1 and i=1.

[0340] [Table 1]

[0341] [Table 2]

[0342] [Table 3]

[0343] [Table 4]

[0344] [Table 5]

[0345] [Comparative Example 1] Compound (3A), represented by the following formula (35), was synthesized by the method described in Patent Document 1.

[0346] [ka] (In equation (35), Rf2 is expressed by the above equation, and r, which represents the average degree of polymerization in Rf2, represents 3.8.)

[0347] [Comparative Example 2] Compound (3B), represented by the following formula (36), was synthesized by the method described in Patent Document 2.

[0348] [ka] (In equation (36), Rf2 is expressed by the above equation, and r, which represents the average degree of polymerization in Rf2, represents 3.8.)

[0349] [Comparative Example 3] Compound (3C), represented by the following formula (37), was synthesized by the method described in Patent Document 3.

[0350] [ka] (In equation (37), Rf1 is expressed by the above equation, where p, which represents the average degree of polymerization in Rf1, is 3.8, and q, which represents the average degree of polymerization, is 0.)

[0351] [Comparative Example 4] Compound (3D), represented by the following formula (38), was synthesized by the method described in Patent Document 4.

[0352] [ka] (In equation (38), Rf1 is represented by the above equation, and in the central Rf1, p, which represents the average degree of polymerization, is 3.8, and q, which represents the average degree of polymerization, is 0. In the two terminal Rf1s, p, which represents the average degree of polymerization, is 2.4, and q, which represents the average degree of polymerization, is 2.4.)

[0353] [Comparative Example 5] Compound (3E), represented by the following formula (39), was synthesized by the method described in Patent Document 5.

[0354] [ka] (In equation (39), Rf1 is expressed by the above equation, where p, which represents the average degree of polymerization in Rf1, is 4.5, and q, which represents the average degree of polymerization, is 4.5.)

[0355] [Comparative Example 6] The compound (3F) represented by the following formula (40) was synthesized by the method described in Patent Document 5.

[0356] [ka] (In equation (40), Rf1 is expressed by the above equation, p, which represents the average degree of polymerization in Rf1, represents 4.5, and q, which represents the average degree of polymerization, also represents 4.5.)

[0357] [Comparative Example 7] The compound (3G) represented by the following formula (41) was synthesized by the method described in Patent Document 6.

[0358] [ka] (In equation (41), Rf1 is expressed by the above equation, p, which represents the average degree of polymerization in Rf1, represents 4.5, and q, which represents the average degree of polymerization, also represents 4.5.)

[0359] The number-average molecular weight (Mn) of the compounds obtained in this manner from Examples 1 to 30 and Comparative Examples 1 to 7 is as described above. 1 H-NMR and19 The results were obtained from 1F-NMR measurements. These results are shown in Tables 6 and 7. It is estimated that there is a variation of approximately 1-5 in the average molecular weight of the synthesized compounds due to factors such as the molecular weight distribution of the fluoropolyethers used as raw materials and differences in the synthesis procedures.

[0360] [Table 6]

[0361] [Table 7]

[0362] Next, lubricating layer-forming solutions were prepared using the compounds obtained in Examples 1-30 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 1-30 and Comparative Examples 1-7.

[0363] "Lubricant layer forming solution" The fluorine-containing ether compounds obtained in Examples 1-30 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 Å to 10 Å when applied to a protective layer, to prepare a solution for forming a lubricating layer.

[0364] "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 1-30 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, using 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 at 120°C and heated for 10 minutes to remove the solvent in the lubricating layer-forming solution, thereby forming a lubricating layer on the protective layer and obtaining a magnetic recording medium.

[0365] "Film thickness measurement" The peak height of the lubricating layer in the magnetic recording media of Examples 1-30 and Comparative Examples 1-7 obtained in this manner was measured using FT-IR (product name: Nicolet iS50, manufactured by Thermo Fisher Scientific) during CF vibration expansion. Then, the film thickness of the lubricating layer was calculated from the measured peak height of the lubricating layer during CF vibration expansion using the correlation formula obtained by the method described later.

[0366] "Method for calculating correlation formulas" A disk was prepared on a 65mm diameter substrate, with an adhesive layer, a soft magnetic layer, a first underlayer, a second underlayer, a magnetic layer, and a protective layer arranged in sequence. Lubricating layers were formed on the protective layer of this disk with film thicknesses ranging from 6 to 20 Å (in 2 Å increments).

[0367] Subsequently, for each disk with a lubricated layer, the increase in film thickness from the disk surface without the lubricated layer was measured using an ellipsometer, and this was determined as the film thickness of the lubricated layer. In addition, for each disk with a lubricated layer, the peak height during CF vibration expansion and contraction was measured using FT-IR. Then, a correlation equation was determined between the peak height obtained by FT-IR and the film thickness of the lubricating layer obtained using an ellipsometer.

[0368] Next, the magnetic recording media of Examples 1-30 and Comparative Examples 1-7 were subjected to abrasion resistance tests and smoothness tests using the methods described below, and evaluated. The results are shown in Tables 6 and 7.

[0369] "Abrasion resistance test" Using a pin-on-disk type friction and wear tester, a 2 mm diameter alumina ball was slid across the lubricating layer of a magnetic recording medium at a load of 40 gf and a sliding speed of 0.25 m / sec to measure the coefficient of friction on the surface of the lubricating layer. The sliding time until the coefficient of friction on the surface of the lubricating layer increased rapidly (coefficient of friction increase time) was then measured. The coefficient of friction increase time was measured four times for each lubricating layer of the magnetic recording medium, and the average value (time) was used as an indicator of the wear resistance of the lubricant coating.

[0370] "Evaluation Criteria for Abrasion Resistance" The results of the friction coefficient increase time of magnetic recording media using the compounds from Examples 1-30 and Comparative Examples 1-7 are shown in Tables 6 and 7. The friction coefficient increase time was evaluated as follows. A larger value for friction coefficient increase time is understood to indicate a better result. A:650sec or more B: 550 sec or more, less than 650 sec C: 450 sec or more, less than 550 sec D: Less than 450 sec

[0371] Furthermore, the time it takes for the coefficient of friction to increase rapidly can be used as an indicator of the wear resistance of the lubricating layer for the following reason: The lubricating layer of a magnetic recording medium wears down as the recording medium is used, and when the lubricating layer is completely gone due to wear, the contacts and the protective layer come into direct contact, causing the coefficient of friction to increase rapidly. This time until the coefficient of friction increases rapidly is thought to correlate with the results of friction tests.

[0372] "Smoothness test" The touchdown power (TDp) was measured as an evaluation index for the smoothness of the lubrication layer surface. TDp was measured using a write tester (DFH tester) as follows. The magnetic recording medium under evaluation was rotated at 5400 rpm, and the magnetic head was positioned opposite it at a radius of 18 mm from the center. The heater power of the writing element (DFH element) of the magnetic head was gradually increased, causing the DFH element to expand due to the heat generated by the heater. The heater power was then measured as TDp (in mW) at the point when the protruding tip of the DFH element, due to thermal expansion, came into contact with the lubricating layer of the magnetic recording medium. Contact between the tip of the DFH element and the lubricating layer of the magnetic recording medium was detected by an acoustic emission (AE) sensor.

[0373] Generally, as the thickness of the lubricating layer decreases, the TDp required for the DFH element to contact the surface of the lubricating layer increases. On the other hand, when comparing magnetic recording media with the same average thickness, it is known that the greater the surface irregularities of the lubricating layer, the greater the maximum height of the lubricating layer, and therefore the smaller the TDp value.

[0374] "Criteria for evaluating smoothness" The smoothness of the lubricating layer of magnetic recording media using the compounds from Examples 1 to 30 and Comparative Examples 1 to 7 was evaluated as follows. A: TDp value of 51.5mW or higher (very small surface irregularities) B: TDp value 51.0~51.4mW (small surface irregularities) C: TDp value 50.5~50.9mW (large surface irregularities) D: TDp value of 50.4mW or less (very large surface irregularities)

[0375] "comprehensive evaluation" Based on the results of the abrasion resistance test and the smoothness test, an overall evaluation was conducted according to the evaluation criteria shown below. "Evaluation Criteria for Overall Assessment" A: The evaluation for wear resistance and smoothness is all A. B: The wear resistance and smoothness ratings are A or B, with at least one of them being B. C: At least one of the evaluations for wear resistance and smoothness is C, and there are no D ratings. D: One or more of the evaluations for wear resistance and smoothness are D.

[0376] As shown in Table 6, the magnetic recording media of Examples 1 to 30 all received an "A" or "B" rating in both the abrasion resistance test and the smoothness test, and the overall rating was also "A" or "B". From this, it was confirmed that the magnetic recording media of Examples 1 to 30 have good abrasion resistance and high smoothness. This is presumed to be because the compounds represented by (1A) to (1O) and (2A) to (2O) that form the lubricating layer of the magnetic recording media in Examples 1 to 30 all satisfy formula (1).

[0377] In particular, the lubricating layers of the magnetic recording media in Examples 1-7, 11, 12, 14-22, 26, 27, 29, and 30, using compounds (1A)-(1G), (1K), (1L), (1N), (1O), (2A)-(2G), (2K), (2L), (2N), and (2O), all received an "A" rating in the smoothness test.

[0378] In the compounds used in the above examples, the two primary hydroxyl groups in the branched terminal group are spaced more than 5 atoms apart. As a result, the two primary hydroxyl groups are less likely to aggregate and can interact independently with the protective layer. Therefore, they spread uniformly on the protective layer, resulting in a lubricating layer with good coverage, and it is believed that particularly excellent smoothness was obtained.

[0379] Furthermore, the lubricating layers of the magnetic recording media in Examples 3-7, 12-15, 18-22, and 27-30, which used compounds (1C)-(1G), (1L)-(1O), (2C)-(2G), and (2L)-(2O), all received an "A" rating in the wear resistance test.

[0380] In the compounds used in the above examples, the distance between the perfluoropolyether chain and the two primary hydroxyl groups contained in the branched end group is sufficiently large. As a result, the two primary hydroxyl groups contained in the branched end group are not affected by the bulkiness caused by the perfluoropolyether chain. Therefore, both primary hydroxyl groups contained in the branched end group have high mobility and degrees of freedom, resulting in high adsorption to the protective layer. Furthermore, the lubricating layer in the above examples has sufficient fluidity and flexibility due to the high mobility of the two primary hydroxyl groups contained in the branched end group. Therefore, even if a part of the lubricating layer deforms due to wear and the fluorine-containing ether compound in the lubricating layer moves to another location, it has a high restorative power to return to its original position. As a result, it is presumed that particularly excellent wear resistance was obtained.

[0381] In contrast, as shown in Table 7, Comparative Examples 1 to 7, which had lubricating layers formed using any of compounds (3A) to (3G), all received a rating of "C" or "D" in both the wear resistance test and the smoothness test, which was inferior to Examples 1 to 30. This is presumed to be because Comparative Examples 1 to 7 formed lubricating layers using compounds that did not satisfy formula (1).

[0382] Specifically, the magnetic recording media of Comparative Examples 1 to 4 have a lubricating layer formed using compounds (3A) to (3D). Compounds (3A) to (3D) have a linking group having a secondary hydroxyl group positioned between two or three perfluoropolyether chains, and terminal groups at both ends of the perfluoropolyether chains having a secondary hydroxyl group and a primary hydroxyl group in that order. Compounds (3A) to (3D) used in the lubricating layers of Comparative Examples 1 to 4 have hydroxyl group linking groups positioned between two or three perfluoropolyether chains. As a result, the central part of the chain structure of compounds (3A) to (3D) adheres closely to the protective layer. However, because compounds (3A) to (3D) contain secondary hydroxyl groups with low degrees of freedom at both terminal groups, their adsorption to the protective layer is insufficient, and the perfluoropolyether chains tend to lift off.

[0383] Furthermore, in compounds (3B) and (3C), the linking groups positioned between two or three perfluoropolyether chains each contain two secondary hydroxyl groups. It is presumed that a large number of secondary hydroxyl groups in the linking groups inhibits the binding of these secondary hydroxyl groups to the active sites on the protective layer. As a result, it is presumed that polar groups not involved in binding to the active sites on the protective layer aggregate by attracting intermolecular and / or intramolecular polar groups, leading to insufficient abrasion resistance and smoothness.

[0384] Furthermore, compound (3E) has only one perfluoropolyether chain, with terminal groups containing two primary hydroxyl groups at each end. In the magnetic recording medium of Comparative Example 5, in which a lubricating layer was formed using compound (3E), both the abrasion resistance test and the smoothness test resulted in a "D" rating. Compound (3E) has only one perfluoropolyether chain, and no structure containing a polar group is located in the center of the chain structure. Therefore, in the lubricating layer of the magnetic recording medium in Comparative Example 5, only the ends of the compound (3E) molecule are in close contact with the protective layer, while the central part of the chain structure is separated from the protective layer. As a result, it is thought that the wear resistance and smoothness were insufficient.

[0385] Furthermore, the magnetic recording media of Comparative Examples 6 and 7 each have a lubricating layer formed using compounds (3F) and (3G), respectively. In the magnetic recording media of Comparative Example 6, which used compound (3F), both the abrasion resistance test and the smoothness test were "D", while in the magnetic recording media of Comparative Example 7, which used compound (3G), the abrasion resistance test was "D" and the smoothness test was "C". Both compounds (3F) and (3G) have only one perfluoropolyether chain, and their terminal group structure consists of multiple hydroxyl groups, each containing two primary hydroxyl groups, located at both ends of the chain.

[0386] Therefore, in the lubricating layers of the magnetic recording media of Comparative Examples 6 and 7, the central part of the chain structure is separated from the protective layer, similar to the lubricating layer of the magnetic recording media of Comparative Example 5. Furthermore, both terminal groups of compounds (3F) and (3G) contain, in addition to two primary hydroxyl groups with high mobility and adsorption, two secondary hydroxyl groups with low degrees of freedom in compound (3F) and one in compound (3G). Compound (3F) has eight hydroxyl groups in its molecule, and compound (3G) has six hydroxyl groups in its molecule. Therefore, it is presumed that in the lubricating layers of the magnetic recording media of Comparative Examples 6 and 7, there are too many hydroxyl groups involved in adsorption, resulting in hydroxyl groups that cannot be adsorbed to the protective layer and become free. As a result, it is presumed that intermolecular and / or intramolecular polar groups tend to aggregate, leading to insufficient wear resistance and smoothness. [Industrial applicability]

[0387] 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 excellent wear resistance and good smoothness, even if it is thin. [Explanation of Symbols]

[0388] 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 -CH ２ -R ２ -(CH ２ -R ３ -CH ２ -R ２ ) ｚ -CH ２ -R ４ (1) (In equation (1), z is either 1 or 2. R ２ This is a perfluoropolyether chain represented by the following formula (5): (z+1) R ２ These may be partially or entirely identical, or they may be different. １ R is one of the groups represented by the following formulas (2-1) or (2-2). ４ R １ It is identical to R. ３ This is a divalent linking group represented by the following formula (4). When z is 2, there are two R ３ They may be the same or they may be different. 【Chemistry 1】 (In formula (2-1), a is an integer between 1 and 3, and b is an integer between 1 and 4. X1 is a hydrogen atom or a group represented by formula (3). X2 is a group represented by formula (3). X1 and X2 may be the same or different.) (In equation (2-2), c is an integer between 0 and 3, d and e are each independent integers between 1 and 5, and the sum of d and e is 4 or greater. X3 and X4 are each independent hydrogen atoms or groups represented by equation (3). X3 and X4 may be the same or different.) (In equation (3), f is an integer between 2 and 5, and g is either 1 or 2.) (In equation (4), h is an integer between 1 and 3, and i is an integer between 1 and 3.) -(CF ２ ) ｗ１ -O-(CF ２ O) ｗ２ -(CF ２ CF ２ O) ｗ３ -(CF ２ CF ２ CF ２ O) ｗ４ -(CF ２ CF ２ CF ２ CF ２ O) ｗ５ -(CF ２ ) ｗ６ - (5) (In equation (5), w2, w3, w4, and w5 represent the average degree of polymerization and each independently represents a value from 0 to 20. However, it is not possible for all of w2, w3, w4, and w5 to be 0 at the same time. w1 and w6 are CF ２ This represents the average value of the number, with each value independently representing 1 to 3.

2. The (z+1) Rs in equation (1) above ２ The fluorine-containing ether compound according to claim 1, wherein each is independently selected from any one of the perfluoropolyether chains represented by the following formulas (5-1) to (5-4). -CF ２ -(OCF ２ CF ２ ) ｊ -(OCF ２ ) ｋ -OCF ２ - (5-1) (In formula (5-1), j and k represent the average degree of polymerization, where j is between 1 and 20, and k is between 0 and 20.) -CF ２ CF ２ -(OCF ２ CF ２ CF ２ ) ｌ -OCF ２ CF ２ - (5-2) (In formula (5-2), l 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 ) ｍ -OCF ２ CF ２ CF ２ - (5-3) (In formula (5-3), m represents the average degree of polymerization and is expressed as 1 to 10.) -(CF ２ ) ｗ７ -O-(CF ２ CF ２ CF ２ O) ｗ８ -(CF ２ CF ２ O) ｗ９ -(CF ２ ) ｗ１０ - (5-4) (In formula (5-4), w8 and w9 represent the average degree of polymerization and each independently represents 1 to 20. w7 and w10 are CF ２ This represents the average number of units, each independently representing 1 to 2.

3. The (z+1) Rs in equation (1) above ２ A fluorine-containing ether compound according to any one of claims 1 or 2, wherein all of the following are identical.

4. A fluorine-containing ether compound according to any one of claims 1 or 2, wherein the number average molecular weight is in the range of 500 to 10,000.

5. A lubricant for magnetic recording media, characterized by containing the fluorine-containing ether compound described in claim 1 or 2.

6. 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 or 2.

7. The magnetic recording medium according to claim 6, wherein the average thickness of the lubricating layer is 0.5 nm to 2.0 nm.

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